4' x 4' x 8" Router Build

[JonnyFive]

Hi all, thought it was about time I broke my silence and made myself known on here. Building my own CNC router is something I've wanted to do for a long time. Over 10 years ago whilst pondering the best way to tackle a woodworking project I came up with the idea of a cross vise on a drill press using a router bit to create a low cost but reasonably accurate solution. It then occurred to me that I could put motors on each axis and voila my own CNC machine. A short amount of Googling later revealed I wasn't the first to have this idea and that using a drill press in this manor wasn't a good idea and that is when I stumbled across the buildyourcnc website. Over the years I have collected project ideas and developed my machine requirements to a point well beyond the limitations of an MDF machine which is when I settled on a design based on Joe's Evo machine.

A decade goes by and I'm now in a position where I have the space to build a machine, more importantly I have approval from the boss!! The only thing in short supply is time, a young family takes up the majority of time and energy that I would usually commit to hobbies but I've set myself goals to make this happen. I'm determined to start building this summer and have spent the last 6 months or so learning Fusion 360 and designing my machine. I'm a long term (18 years+) Pro/Engineer / Creo user and initially found Fusion really wasn't intuitive but I'm getting there slowly.

So on to my machine, as mentioned it started as Joe's Evo but I have made tweaks along the way and have ended up with something that doesn't have much in common with this starting point. I've settled on a cutting area of 4' x 4' x 8" with an increased travel (an extra 12") on the y-axis (still confused about which is x and y but it makes most sense to me for the long axis to be y not the gantry) to allow dovetailing or a 4th / 5th axis to be added at some point in the future. I'll be working mainly with wood, plastic and with the occasional bit of aluminium.

The base frame consists of 2 welded side frames (made from 50x50x3 box section with 100x50x4 for the top beams), a welded top frame acting as the machine bed, and lower cross beams. These are all bolted together and then the top beams levelled using epoxy.

The x & y axes uses 20mm Hiwin rails, the z uses 15mm. The x rails are mounted top and bottom of a length of 160 x 80mm aluminium extrusion. The z axis has the carriages fixed to the x axis and the rails on the moving spindle mount plate. I believe this will give me the stiffest setup.

Up until this point I am pretty happy with the design although there is a lot more detail to be added before I start building. I have a number of questions that I would really appreciate the benefit of everyone else's superior knowledge and experience:


How much over travel should each axis have, e.g. for the 4' x-axis how long should the travel really be? Is an extra 1" each side about right?
What should the clearance between the collet and the spoilboard be at maximum (lowest) travel of the z-axis?
What is the best transmission method for this size machine? A lot of people on here use ballscrews but there seems to be a move away from this within the Joe's CNC community for bigger machines (over 1000m). I'm currently using the CNC router parts rack and pinion unit but wondering if this is the best solution?
I'm a little stuck on how I maintain the parallel relationship between the y-axis rails and the racks. Once the frame has been levelled with epoxy it is straightforward to align the rails, but my assumption is that the epoxy is the only reliable datum and the side of the frame could be distorted / twisted due to the welding. The best I can come up with is to either mount the rack on a piece of angle fixed to the top of the epoxy or mount the rail and rack to a piece of aluminium extrusion to keep them both parallel?


I'm sure there will be hundreds of questions to come, thanks all for looking and any suggestions you have.

Cheers,

Jon

P.S. Ignore the left hand side in these pics, I have only concentrated on the right hand side for now.

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[GrahamWhite]

Hi Jon,
I'm currently building a Joes Hybrid R&P 8ft x 4ft
my build is budget constrained so that's why I went with the cnc routerparts pinion drives but even for my machine at 8ft you can go ballscrews- they just need to be 25mm or bigger I was advised to stop the whipping.
If you are still thinking of the pinion drives then please be aware that the spur gear they use is a US imperial pitch size, so if you don't have any machining options they could be very expensive to change to metric- I was quoted £100 each spur! I found it difficult to obtain the Imperial Rack size here so had to sort it a different route.
Afraid that's my only input as I have followed most of the plans fairly closely.
Best of luck with the build :)
Regards
Graham

[routercnc]

Hi Jonnyfive

Overall design concept looks OK, but some comments.

1) An extra 1" travel will be fine to allow the machine to go slightly over the home switch/prox and reverse back to settle at the home position. Gives a small amount of room before any physical hard stop.

2) When the Z is at maximum travel the collet needs to be close enough so that the cutting bit can level the board. I notice on your design that there is still plenty of Z travel left when nearly fully down, which is a bit of a waste. It also means when the Z axis is fully up/home it is still fairly close to the board which will limit the maximum height of the part you can cut. If you want to do vice work this gap looks too small. Most people work to 150 mm from a typical tool tip to the spoil board when fully raised. Yours looks considerably closer. Just check this is what you want the machine to do. You will see other machines on here use vertical risers on the bed, or vertical extensions of the side members for the base frame to get the main beam high enough that the gantry then runs on.

3) Never used R&P so can't comment. Others may be able to chip in on whether you can go up from 16 mm ballscrew to 20 mm ballscrew as an alternative step before going to R&P for the long axis, potentially tensioned at both ends. Wait for advice on that one . . .

4) I've seen racks shimmed in using a DTI mounted to the carriage of the rail, ensuring it runs parallel. Either use proper shim stock or aluminium foil if the gaps are not that big. One thing to consider is that the stiffness of that axis depends on the stiffness of the rack mounting so I wouldn't favour angle brackets and the like, rather a very solid shimmed mount back to the main gantry.

Best bit is when it is all built and moving you will be able to say JonnyFive is alive :friendly_wink:

[JonnyFive]

Thanks for the replies.

Graham:



If you are still thinking of the pinion drives then please be aware that the spur gear they use is a US imperial pitch size

I knew it was an imperial rack but had assumed it was of the standard DP type that isn't too hard to find? Do you know what pitch it is? What is the solution you have come up with?

routercnc:



1) An extra 1" travel will be fine to allow the machine to go slightly over the home switch/prox and reverse back to settle at the home position. Gives a small amount of room before any physical hard stop.

OK, I'll go with 50" travel, I'll round up to 1300mm as I'm a metric kind of guy.



2) When the Z is at maximum travel the collet needs to be close enough so that the cutting bit can level the board. I notice on your design that there is still plenty of Z travel left when nearly fully down, which is a bit of a waste. It also means when the Z axis is fully up/home it is still fairly close to the board which will limit the maximum height of the part you can cut. If you want to do vice work this gap looks too small. Most people work to 150 mm from a typical tool tip to the spoil board when fully raised. Yours looks considerably closer.

This is why I was asking so that I can adjust the offset between the spoilboard and the gantry, it's at a random arbitrary dimension at the moment which I agree looks too small. I guess my question should have been how much does the shortest cutter stick out from the spindle, so long as that just touches the spoilboard then I can adjust my gantry height from that point.



Just check this is what you want the machine to do. You will see other machines on here use vertical risers on the bed, or vertical extensions of the side members for the base frame to get the main beam high enough that the gantry then runs on.

Not entirely sure waht you mean by this, can you explain please?



4) I've seen racks shimmed in using a DTI mounted to the carriage of the rail, ensuring it runs parallel. Either use proper shim stock or aluminium foil if the gaps are not that big.

I can see the advantage of a ballscrew as there are only two points that need shimming.



One thing to consider is that the stiffness of that axis depends on the stiffness of the rack mounting so I wouldn't favour angle brackets and the like, rather a very solid shimmed mount back to the main gantry.

I hadn't considered this, it's a really good point thanks!



Best bit is when it is all built and moving you will be able to say JonnyFive is alive :friendly_wink:

This day is a long way off but I can't wait!

Cheers!

[routercnc]

Ok the vertical risers comment- I meant at the moment the side members that the long axis rails sit on would need to move up to push the gantry up and that it would be stiffer if the vertical parts of the lower frame were longer rather than finding a rectangular section which was very tall and slim. In fact I would probably not go with side members quite as rectangular as you have drawn them but make them a bit more squarish. Then get the height you need by making the base frame vertical parts longer. Very tall large open rectangular sections will start to lozenge when they get pushed sideways by the cutting forces. Away from pc so I can’t sketch something.

[JonnyFive]

Understood. They were originally 50x50x3 like the rest of the frame but I changed them to increase the second moment of area. I can change them back easy enough.

[GrahamWhite]

I bought my rack while the parts where on their way from USA, noobie error on my part! lol
I only matched up the 20 degree angle not the DP
End up buying new 60tooth gears with a hub on and new spur gears for mod 1.0 rack and drilled out and reassembled the drives, at least now if I ever need to replace the spur gear they're only £5 :)

[Neale]

Good luck - it's a fun process!

I built something roughly similar a year or two back - here (http://www.mycncuk.com/threads/11617-AVOR-–-a-steel-framed-medium-size-router). Probably more useful if you look at the "what I would do different next time" comments!

Joe's CNC guys go rack and pinion because it is a heavily US-based community. R&P can be bought from US manufacturers who don't seem to make ballscrews which generally come from China. Not a popular choice for US builders, unlike UK/Europe. Seems to be almost a fashion thing rather than technical choice. Both can work but unless you really need R&P, ballscrews are much easier.

[JonnyFive]

Thanks for your input Neale, just read your thread - great work on documenting everything so thoroughly!! It'd be nice to see some photos of the entire machine, looks like I'm heading along a similar path to you.

Interesting what you say about the R&P. My understanding of the ballscrew / R&P decision was that although ballscrews are more accurate & efficient anything over 1m should use R&P because the ballscrew whipping limits performance - is that correct? There doesn't seem to be much of a cost difference between the two?

[JonnyFive]

I bought my rack while the parts where on their way from USA, noobie error on my part! lol
I only matched up the 20 degree angle not the DP
End up buying new 60tooth gears with a hub on and new spur gears for mod 1.0 rack and drilled out and reassembled the drives, at least now if I ever need to replace the spur gear they're only £5 :)

Sounds like it might have been a costly way of doing things? I had considered designing my own version as there's nothing clever about it really but thought the costs would be more than buying from CNCRP.

Out of interest where did you get your aluminium extrusion from please?

[GrahamWhite]

I ordered it from the UK stockist for 8020 down in Portsmouth. Again a pain to do but I was following the plans, the UK profiles didn't seem to have the same T-slot configuration as the 8020 one. Not much in the price though just longer delivery time.

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[JonnyFive]

I ordered it from the UK stockist for 8020 down in Portsmouth. Again a pain to do but I was following the plans, the UK profiles didn't seem to have the same T-slot configuration as the 8020 one. Not much in the price though just longer delivery time.

That's good to know, I have been in contact with them but not had prices yet. They're not far from me so was thinking I could save on delivery charge by collecting but was concerned that the cost of having it shipped from the US would be prohibitive.

[GrahamWhite]

I collected mine anyway and I'm in Lincolnshire lol, didn't trust a pallet delivery and it was gonna be £100 anyway way so I went for a jolly :) I think for 2x3m and 1x2m was about £430,whether that's expensive or not it suited me for the plans and everything else has fitted around that.
.........
Just looked at bosch and its actually a fair bit cheaper:( but like I say it suited the plans better

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[JonnyFive]

I've been looking at item (https://uk-product.item24.com/catalogue/products/profiles-1001009536/), they do a 160 x 80 profile with a slightly higher second moment than 80/20, haven't got any prices from them yet though.

[Neale]

Interesting what you say about the R&P. My understanding of the ballscrew / R&P decision was that although ballscrews are more accurate & efficient anything over 1m should use R&P because the ballscrew whipping limits performance - is that correct? There doesn't seem to be much of a cost difference between the two?
This is where we get into real design decisions! I'm using 2005 ballscrews. There are a few online critical speed calculators available; the general consensus for 1750mm, fixed/floating bearing, screws is around 900-1000 rpm. That gives me 5000mm/min rapids, which is slower than ideal but which works for me using a hobby machine. In retrospect, I could have used 2010 and run faster. However, I am also using 2x3Nm motors to drive these. Pulley drive, but 1-1 gearing. This is because the motors are just about reaching their corner speed (where torque starts dropping rapidly) at about the "whip" speed of the ballscrews. I'm not entirely sure (because I haven't studied other people's designs) if the motors would handle the load of my heavy gantry using 2010 as there is also the acceleration/speed trade-off. I doa fair bit of small fiddly machining where acceleration is more important in overall cutting time than speed.

All I'm really saying is that you have to balance up all the conflicting requirements for an engineering compromise that is right for you and your intended use. My design/build might not be optimal, even for me, but at least it works! There are plenty of posts one this forum with other designs successfully using ballscrews of this kind of length and I would happily do the same again.

[JonnyFive]

That's good to know, I appreciate your input. I'll keep trawling through build logs and see what others have come up with.

Given what you have said do you think it would be better to have used torquier motors and gear them down to get the speed up, perhaps needing to go up in screw diameter as a consequence? I have no real concept of how fast is too fast / slow or how much torque is needed to cut at reasonable feeds. I have a combination of small fiddly and large uncomplicated projects that I'd like to be able to do on my machine. Initially I'm not that concerned about speed but at some point I would like to make some money out of this and so higher speed would be nice.

[JonnyFive]

Does this look about the right amount of clearance with the z-axis at its lowest?

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My plan is to have two pieces of wood for the bed, the top one being sacrificial. I've assumed the shortest cutter would stick out about 25mm and allowed this much clearance from the top of the first spoil board. This should allow for the top board to be resurfaced a few times and still give enough travel on the Z. Am I about right with this?

Cheers

[routercnc]

Does this look about the right amount of clearance with the z-axis at its lowest?

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My plan is to have two pieces of wood for the bed, the top one being sacrificial. I've assumed the shortest cutter would stick out about 25mm and allowed this much clearance from the top of the first spoil board. This should allow for the top board to be resurfaced a few times and still give enough travel on the Z. Am I about right with this?

Cheers

Spindle looks ok but spindle plate would be better higher to give clearance for clamps or vice jaws. To still give enough travel the whole gantry then needs to be raised the same amount. But if you move it too high then the Z axis has to extend down further so it is all a balancing act in the design stage.

[JonnyFive]

Ok, I’ll move things around a bit to raise the gantry and mounting plate. Cheers


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[Clive S]

Ok, I’ll move things around a bit to raise the gantry and mounting plate. Cheers


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If you raise the Z plate and lower the spindle in the clamp to stop the Z plate catching clamps etc.

[JonnyFive]

I had the spindle mount lower down in my original pics. I’ll put it back where it was. Thanks [emoji1303]


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[JonnyFive]

I have now moved the spindle mount lower onto the backing plate, how does this look?:

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I have done a bit more digging into why people within the Joe's community have moved away from ball screws to R&P, the reasoning appears to be about speed, ease of assembly / maintenace and price more than anything. Looking at the pricing of C7 leadscrews on BST Automation they seem to be cheaper than using the CNC routerparts rack and pinion system (although the postage costs are about as much as the screws!) - I'm confused as to which way to go, any suggestions please? Would I be looking at 2010 for the longest axis, it will be 1600mm long? This comes out around 1000RPM critical speed - is this too low?

All help gratefully received.

Cheers :beer:

[GrahamWhite]

Are you confusing lead screws and ball screws?
Joe's used to use lead screws and went to R&P ,ball screws are better than both but way more expensive!

[routercnc]

Looks ok to me with that spindle mount position. One thing I did on my Mk3 was to drill and tap a second set of holes a bit higher on the Y plate so I had the option of mounting it higher for very tall work. Of course you can only reach across that work an amount until the Y plate may hit it but it is a quick feature to add at the build stage. I also added tapped holes along one edge of the Y plate to allow me to bolt a reference strip and maintain spindle tram alignment whilst adjusting the spindle holder. Never used it of course! But worth a mention

Can’t help on the ballscrew a that long and r&p as haven’t used them.

If you search the forum that sort of thing has been asked before and Jazzcnc has given advice

[JonnyFive]

As far as I can tell Joe's Hybrid machine used lead screws, the Evo used ball screws and the EVO MKII uses R&P, just wondering why they would move away from ball screws if they are the best?

Good shout putting extra holes for spindle mounting, I'll definitely do that.

[Cadvision.fi]

Hello, I am new to this forum and I was looking for information of "pinion & rack & gear reduction with spring tension" -packs - similar to cncrouterparts version of
PRO Rack and Pinion Drive, NEMA 34.
Reasons why I decided to use rack & pinion were exactly those that JF mentioned above (+ the option to make extensions later). So if anyone can help me where can I get as ready sollution as possible I am interested to hear. Nema 34 and module probably 1.25 with straight teeth (the rack can be cut with laser).

[JonnyFive]

Been making very slow progress on my design lately and I'm looking at redesigning my frame but can't decide what size tubing to use. Originally I was using 50x50x3 for most of the frame with 100x50x4 for the rail support, I'm toying with increasing this to 50x50x4, 50x50x5 or possibly even 60x60x5. Obviously there is a cost difference associated with each option so I'd like to do some sort of stress / deflection calculations to work out whether the cost is justified. Can anyone tell me what sort of loading I should be applying to my design to work this out please? I have seen example calculations with 50N as the load on the spindle which seems more than enough from my experience using a hand router - is this a good number to work with? If so I don't imagine I will get much flex from the frame using 50x50x3 let alone the heavier sections, I think most deflection will come from the bearings and aluminium extrusion gantry. What is an acceptable amount of deflection? I understand the argument for increasing mass to reduce vibration but if I can reduce the material costs for the frame and find another way of adding mass to it (sand / epoxy filling the frame?) then I can spend the money elsewhere.

Thanks for your help!

[Neale]

I know that you've had a look at my write-up already. I used 3mm wall thickness. If I were doing it again, I might have used 4mm for some of the parts (like anything that has a rail bolted you it) just for better damping. However, from a strength point of view I am happy with what I have, remembering that my machine is very much hobby class, not commercial/production. Just recently I have been machining quite a lot of small steel components. I use small (2-4mm three-flute coated carbide designed to run without coolant) cutters at around 7-8K RPM and am getting good results. Again, not production-style heavy cuts but the ability to machine more complex profiles (with some 3D work as well) means that I use the router in preference to my vertical mill. My gantry is quite stiff (three 50x50x3 sections). I'm pretty happy with the overall capability which is much more than I might have expected and way beyond what I had hoped to achieve.

This is just one data point from one user so consider it alongside other opinions and designs but it emphasises that engineering design is as much about compromise as ultimate performance in one aspect. After all, my machine is too slow for an ideal woodworking machine and much too light for decent metal cutting. The fact that I can get acceptable results, even if not optimum, owes more to luck than judgment...

[JAZZCNC]

The thicker the better as it significantly dampens vibrations which translates into cleaner cuts and longer tool life.
Don't be messing around with sand etc because while it dampens vibrations slightly the cost in performance due to the extra weight is too expensive for the returns.
Spending a little extra for Thicker steel will pay dividends in quality and stiffness.

For a machine this size I'd go with 60x60x5 as a minimum. It will give you a much stiffer machine than using 50x50. I've built machines this size using both sizes and 60x60 is the better choice.

[JonnyFive]

Neal / Jazz - thanks for the feedback.

I'll look at thickening things up, it does add up quite a bit - going from 50x50x4 to 50x50x5 to 60x60x5 each jump adds about £100 but I only want to build it once so want it to be right.

Jazz - I was only thinking of sand filling the static parts, I wasn't intending to fill the gantry - I'd be much happier not to have to do this. The gantry will be the same 160x80 ali extrusion whichever way I go with the frame.

Is the 50N loading a fair number?

Cheers!

[JAZZCNC]

The gantry will be the same 160x80 ali extrusion whichever way I go with the frame.

Is the 50N loading a fair number

The 50N loading in which direction.? However, to be honest, no matter the direction the correlation between simulation in SW and real-world when it comes to cutting and vibrations etc won't match.

What I can tell you from experience of building god knows how many steel-framed machines is that the extra cost of using thicker steel pays big time regards vibrations. The loads going into the machine don't come close to stressing the steel so it's not something worth fretting over.

Regards the Gantry then again most of my machines use HD ITEM Profile. If you want a much stiffer gantry then I'd suggest you change design slightly and go with L shape setup like I use. Over the years I've used both setups and the L shape is far far stiffer and two pieces of 120 x 80 arranged in an L shape gives much stiffer gantry with lower vibrations than single 160x80.

[JonnyFive]

The 50N loading in which direction.?

I'm referring to the reaction force of the machine pushing the cutter through the material so could be in any direction depending on which way the router is moving. My only reference point is using a hand router and it doesn't fell like it needs 50N to push the router along. I'm talking about the cutting force as shown on this diagram:

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two pieces of 120 x 80 arranged in an L shape gives much stiffer gantry with lower vibrations than single 160x80

Do you mean 120 x 60? I can't find 120 x 80. I have run the calcs on the L section and I'm amazed how much difference it makes - you've convinced me! Do you have any examples of the machines you've made, I'd love to see them.

Cheers :beer:

[JonnyFive]

Do you mean 120 x 60? I can't find 120 x 80

Don't worry, I've found it - I was looking in the Profile 10/12 sections, it's in the Profile 8.

[JAZZCNC]

Don't worry, I've found it - I was looking in the Profile 10/12 sections, it's in the Profile 8.

Yes, the 8mm slot is better because gives more area for profile rail to sit onto.

[routercnc]

I've found the 50 N force in X and Y directions to be a good guide but it is only the start. If under this simple load condition if you are <0.05 mm then I would call that a fair start point, and you would expect a fair amount of accuracy on the finished dimension.

But wait, this 50 N is a simple static force, and does not account for the repeated impacts of the cutting action in the material which will cause a ripple on top of this average force, say from 45 N to 65 N (making the numbers up to show the point) with every rotation. As the cutter rotates very fast this will cause vibrations in the machine, not only at the main impact frequency but across a wide frequency range with amplifications where the machine frame resonances are and this may show up in the finished part.

This is where the wall thickness will help you as Jazz is advising, and this is money well spent. It adds significant stiffness (more than might be suggested is required by the simple static load analysis), which will lower the vibration levels as higher frequencies decay quicker and as they are stiffer they also deflect less initially with each impact. It also adds mass which will also lower the vibration (acceleration) levels as shown by re-arrangement of the famous F=ma equation ; a = F/m). So it is a win-win up to the limit of what your steppers can accelerate around.
Technically you would not have added much damping (energy absorption through friction, e.g. damping pads or sand) but you will still have reduced the vibration amplitude through the mass and stiffness which is all that matters.

If it helps I went through the same thought process on my mk4 machine for the upper box section members on the bed. I went with 5 mm wall in the end, as every mm costs £, but I know it makes a difference.

[JonnyFive]

RouterCNC - thanks for taking the time to explain all that, I appreciate it. I've had a bit of a play with your stiffness calculator spreadsheet and I'm getting gantry deflection of <0.05mm as I would expect following Jazz's advice.

I think I'm going to redo my frame design using 60x60x5 for the legs, 120x60x5 for the rail supports and maybe use 50x50x4 for the bed and triangulation / stiffeners.

[JAZZCNC]

I think I'm going to redo my frame design using 60x60x5 for the legs, 120x60x5 for the rail supports and maybe use 50x50x4 for the bed and triangulation / stiffeners.

I wouldn't take that route as the difference in steel price won't be massive. It will make welding more difficult because of your mixing different thicknesses and tube sizes.
At this width, the bed will be much less resonant with the thicker, wider tube size giving a better finish on parts. Esp when cutting harder materials that will resonate into the bed and frame.

Keep in mind it's the foundation of the whole machine. It really isn't worth spoiling the broth for apeth of salt.

[Kitwn]

It really isn't worth spoiling the broth for apeth of salt.
Where's yer grammar lad? "It in't worth spoilin' t' broth for an ha'p'orth o' salt"
.

[JonnyFive]

Keep in mind it's the foundation of the whole machine. It really isn't worth spoiling the broth for apeth of salt.

Understood, you're right, if it's worth doing it's worth doing right. I'll crack on with 60x60x5 & 60x120x5.

Cheers!

[JAZZCNC]

Where's yer grammar lad? "It in't worth spoilin' t' broth for an ha'p'orth o' salt"
.

Tha's reight old lad, cummin from't God's own country a shuda known bet'ta, but think tha'll fi'nd it's spelt ha'peth.!!. . . . cos we'll av non that posh "orth" rarynd here si'thi.

[Kitwn]

Tha's reight old lad, cummin from't God's own country a shuda known bet'ta, but think tha'll fi'nd it's spelt ha'peth.!!. . . . cos we'll av non that posh "orth" rarynd here si'thi.

My dad was pure-bred Yorkshire (though he was born in Karachi, only because his mother was there at the time) but was educated at Cambridge so the odd posh turn of phrase was known to escape his lips. Not often, mind!

Kit

[JonnyFive]

Mrs J5 is a Yorkshire lass, I’m going to have to ask her to translate.


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[Gustave]

Hello JonnyFive, finally have you done the assembly of 2 x 120x80 suggested in the discussion or do you stay with 160 x 80 ?
Gustave

[JonnyFive]

Hello JonnyFive, finally have you done the assembly of 2 x 120x80 suggested in the discussion or do you stay with 160 x 80 ?

Hi Gustave, I haven’t done any assembly yet, I haven’t been able to spend any time on the project recently and I’m still tweaking the design. I will be using the 120x80 when I get around to it, the maths says it will be a lot stiffer.

Cheers.


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[Gustave]

Hi Gustave, I haven’t done any assembly yet, I haven’t been able to spend any time on the project recently and I’m still tweaking the design. I will be using the 120x80 when I get around to it, the maths says it will be a lot stiffer.

Cheers.


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Thank you, I think I will also going on L shape based on 120x80.
I am designing a nearby machine and I have the same R&P and ball-screw dilem ! For the moment I think going on ball-screw for price (Fred BST), precision, easy to achieve. The X is 1800mm length and I plan to use 2 x 2510 ball screws. I bought servos motors (Simdrive AC system 750W (https://en.cs-lab.eu/product/simdrive-motor-750w-set/), Holding Torque (N.m)
2.4, Peak Torque (N.m) : 7.2, Rated Speed (rpm) : 3000) and I hesitate between direct drive or the use of pulley with a ratio 2: 1. Do you have any advice for me?
Best Regard

[JonnyFive]

Does anyone have any thoughts on mounting the rails as below, it gives a slightly greater distance between the rails than mounting the lower one in line with the top one - is it likely to be a pain to get everything parallel?

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[routercnc]

There is probably a theoretical small gain with the rails set such that the line between them is somewhere around the centre of the overall L shape, and they are furthest apart. But I can’t help thinking you would loose more in the box plates around the outside with vibration and flex. Personally I would put the lower rail directly below the upper so they are close to the front where the Z axis is.

Also the top and bottom plates look a bit thin. 20mm is ideal then the closer plate on the back is less critical. You can delete it, or if you still want it then 6mm would be fine.

[JonnyFive]

That makes sense, thanks! I knew there was a reason I hadn't seen anyone else doing it.

[JonnyFive]

Finally some progress! This project has been rolling along slowly in between the many other things that I've had going on, thought it was about time for an update.

This is where I'm at:

x-axis:
2010 x 1480mm ballscrew geared down 2:1 from 4Nm NEMA 23 motor
2 x 20mm x 1450mm HIWIN rails + 4 x HGW20HC2R carriages

y-axis:
2 x 2010 x 1750mm ballscrews geared down 2:1 from 4Nm NEMA 23 motors
2 x 20mm x 1900mm HIWIN rails + 4 x HGW20HC2R carriages

z-axis:
1605 x 412mm ballscrew geared 1:1 from 4Nm NEMA 23 motor
2 x 20mm X 400mm HIWIN rails + 4 x HGH20HCA1R carriages

Frame:
The frame is a mixture of 60 x 60 x 5 and 60 x 120 x 5, possibly overkill with the bracing so might think about simplifying it a bit.
I am planning to use a strip of steel with rivnuts to secure the y rails to the frame rather than tapping the frame - thought this would give a bit more adjustment.

Gantry:
2 x 160mm x 80mm in L configuration
Intermediate mounting plates for squaring the x & y axis

I'm at the point now that I really need to tie down some key components so that I can finish detailing everything and have a few questions for the hive mind:

Motors - Are the CNC4YOU 4Nm NEMA 23s the way to go for all 4 motors? Electronics is definitely not my strong point, I'm going to need a lot of help to get through that part of the project!

Pulleys - are HTD5 the ones to go for? I've modelled up 14T & 28T (copied from Joe's amazing design) and there are a couple of things I'm not so happy about. Firstly the motor shaft is not long enough for the pulley when using one with a boss, it overhangs the end which doesn't seem ideal. The alternative is to use a pulley where the grub screw is on the toothed part and it seems like that will munch through the belt as it rotates - anyone got experience of this pulley type? My second concern is fitting the smaller pulley onto the 20mm ballscrew - the shaft is nominally 12mm which looks too big for the pulley to fit, turning the ballscrew down to 8mm or so seems like it might be too weak? The alternative to this is increasing pulley sizes which will make the motor pulley quite large.

Cable chains - What size do I need (I'll be using a water cooled spindle)? Should I use the same size for all 3 chains or should they get progressively smaller?

I appreciate all the help, cheers!


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[JAZZCNC]

This is where I'm at:

x-axis:
2010 x 1480mm ballscrew geared down 2:1 from 4Nm NEMA 23 motor
2 x 20mm x 1450mm HIWIN rails + 4 x HGW20HC2R carriages

y-axis:
2 x 2010 x 1750mm ballscrews geared down 2:1 from 4Nm NEMA 23 motors
2 x 20mm x 1900mm HIWIN rails + 4 x HGW20HC2R carriages



Why are you gearing 2:1 if using a 10mm pitch.? It's not required and would actually be detrimental to the machine as it will be slow. If you are trying to lower the screw speed then go with a 20mm pitch and then use the 2:1 ratio, this will give the same travel velocity as 10mm but with half the screw speed.
If not lowering the screw speed just go with a 1:1 ratio with a 10mm pitch.




I'm at the point now that I really need to tie down some key components so that I can finish detailing everything and have a few questions for the hive mind:

Motors - Are the CNC4YOU 4Nm NEMA 23s the way to go for all 4 motors? Electronics is definitely not my strong point, I'm going to need a lot of help to get through that part of the project!


Yes, they will work but if you are going to this trouble then I would go with Closed-loop steppers as the price difference isn't massive and they are much more accurate.
Also, it's not just the motors you need to decide on, the drives which control them and the voltage you run them at are important. Don't go with any drives that are rated, 50Vdc Max. To get the best from 4Nm motors you'll want to be running them around 60-65Vdc or 50Vac if the drives support AC voltage which many do these days. You also need a safety margin on the drive's Max voltage or around 10%, so if using 60Vdc you want drives with a max voltage of 70Vdc or more.



Pulleys - are HTD5 the ones to go for? I've modeled up 14T & 28T (copied from Joe's amazing design) and there are a couple of things I'm not so happy about. Firstly the motor shaft is not long enough for the pulley when using one with a boss, it overhangs the end which doesn't seem ideal. The alternative is to use a pulley where the grub screw is on the toothed part and it seems like that will munch through the belt as it rotates - anyone got experience of this pulley type? My second concern is fitting the smaller pulley onto the 20mm ballscrew - the shaft is nominally 12mm which looks too big for the pulley to fit, turning the ballscrew down to 8mm or so seems like it might be too weak? The alternative to this is increasing pulley sizes which will make the motor pulley quite large.

HTD 5 x 15mm wide is perfect for this job.
Regards the grub screws then turn the Boss inwards so it's on the shaft if possible, if not then it's ok to drill between the teeth provided you remove any burrs. However, you say you are putting the small pulley on the screw.? You have this the wrong way around, you want the small pulley on the motor and the large pulley on the screw if you want 2:1 ratio.



Cable chains - What size do I need (I'll be using a water cooled spindle)? Should I use the same size for all 3 chains or should they get progressively smaller?

Larger is better, the worst thing you can do is use too narrow cable chains and have the cables rubbing against each other, worse still if your running noisy cables like the spindle cable with signal cables like limits, etc, which you will be.
You also don't need 3 chains, on the machines I build I only fit chains on X-axis and Y-axis, the Z-axis which is mostly just the spindle cable and water pipes, I run thru flexible conduit.
The energy chain I supply has internal dimensions of 25 x 58mm.

This pic shows the flexible conduit and energy chain, there is the same chain at the rear of the gantry.

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[JonnyFive]

Hi Jazz, thanks for the reply, I appreciate the help.

I thought I'd read about gearing the motor / ballscrew to lower the screw speed to prevent whip whilst keeping the motor running at it's most efficient speed? Maybe I've got it all wrong. So 1:1 is the way to go is it?

As I mentioned the electronics side of things is really not my strong side, the more I read about it the more lost I get. Could you point me in the direction of some suitable closed loop steppers? I've had a look but they seem to be around £200 each? I had been thinking of going with a UCCNC ethernet controller, is this a good option? Do closed loop steppers need a different controller & drives?

I had put the big pulley on the motor based on what Joe did in his video: https://www.youtube.com/watch?v=gQz9G_Dlv3w about 45 seconds in.

The cable chains I have modelled are 50 x 17.5 internal - I'll increase this to 25 x 58mm as you suggest.

Thanks again :beer:

[JAZZCNC]

I thought I'd read about gearing the motor / ballscrew to lower the screw speed to prevent whip whilst keeping the motor running at it's most efficient speed? Maybe I've got it all wrong. So 1:1 is the way to go is it?

I had put the big pulley on the motor based on what Joe did in his video: https://www.youtube.com/watch?v=gQz9G_Dlv3w about 45 seconds in.

Yes this correct but the way you had it was doing the opposite, this would double the screw speed not half it.

The reason Joe used a large pulley on the motor with a small one on the screw was to increase the speed because he only had 5mm pitch ball-screws. So he needed the 1:2 ratio to get the extra speed but in doing so he doubled the screw speed which increases the chance for the whip.

As the above demonstrates, Be careful with blindly following someone else's component choice or build thread if you don't fully understand what or why these have been used.?
It's very easy to select the wrong components and end up with an unbalanced machine or worse completley unusable machine.!



As I mentioned the electronics side of things is really not my strong side, the more I read about it the more lost I get. Could you point me in the direction of some suitable closed loop steppers? I've had a look but they seem to be around £200 each?

You can get them cheaper than that, but if you are not in a rush I can supply you with 4.5nm and drives from Lichuan that I fit on machines I build. Unfortunately, at the moment I only have enough stock for the machines I'm building, however, I have an order being produced at the moment and will have new stock in about 10 weeks' time.


I had been thinking of going with a UCCNC ethernet controller, is this a good option?:

Yes, it's very good, I use it on the machines we build and fit the AXBB-E ethernet controller. Again I can supply you with UCCNC and Controller if you want to PM I will give you prices.


Do closed loop steppers need a different controller & drives?:

They don't need a different controller but they do need drives that are matched to the motor/encoder. They are often sold in matching sets.

[JonnyFive]

I think part of the problem is I don't have the motor performance curve, I have worked out the ballscrew critical speed is about 1000RPM (end fixity type C - right?) but not sure what speed the motor should be going.

I'd definitely be interested in motors, drives & controllers - I'll PM you. I won't be ready for them for a few months yet so no major hurry on my part, I just need to know what size to design brackets to at the moment.

[JonnyFive]

I think I've remebered how I got confused with the 2:1 gearing, think I read somewhere about using 2020 ballscrews and then gearing them for lower RPM. 2010 seems to be the norm for a 4' machine so will go with that.

I've made a bit more progress on the design......

I have removed the gear reductions, now the x & y axes are geared 1:1 with 20T pulleys and the z is direct drive. I am still working with the 4Nm Nema 23s on all axes.

I have also tidied up the end stops and proximity sensors.

The x & y cable chains now have inner dims of 25 x 57mm (I couldn't find 25 x 58mm).

Think I'm nearly there with the mechanical design, soon be time to concentrate on the electronics - not looking forward to that one!

:beer:

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[Kitwn]

Looks good to me. The only thing I would point out is that you have the proximity sensor end-on. There's very little room for deceleration between detecting the gantry and being smashed by it. A safer option is to have the sensor pointing uipwards so that it detects the gantry riding above it. You already have a non-smashable mechanical end-stop in case that fails.

Kit

[JonnyFive]

That’s a fair point, I’ll look at moving them through 90 degrees. Thanks!


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[Clive S]

I personally would turn the Z axis sensor the other way round ie. fit it on the back plate. This will make the cable neater.

You could just drill the back plate.

[JonnyFive]

I personally would turn the Z axis sensor the other way round ie. fit it on the back plate. This will make the cable neater.

You could just drill the back plate.

I like the sound of that! Thanks.


Sent from my iPhone using Tapatalk

[JonnyFive]

I like the sound of that! Thanks.


Sent from my iPhone using Tapatalk

Thinking about it, I think the reason I didn’t do this is because the sensor would have to be where the lower target thingy is now and there isn’t enough depth to fit it between the gantry and z plate. Unless I’ve misunderstood what you’re suggesting?


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[JonnyFive]

Looks good to me. The only thing I would point out is that you have the proximity sensor end-on. There's very little room for deceleration between detecting the gantry and being smashed by it. A safer option is to have the sensor pointing uipwards so that it detects the gantry riding above it. You already have a non-smashable mechanical end-stop in case that fails.

Kit

I haven’t looked at the data sheet for the sensor but. I’d assumed that it would be triggered 2 or 3mm before contact and I could then have the hard stop almost flush with the sensor z. How much overrun should I allow for? I guess when it’s travelling at speed something like 5-10mm would be better?


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[Kitwn]

I haven’t looked at the data sheet for the sensor but. I’d assumed that it would be triggered 2 or 3mm before contact and I could then have the hard stop almost flush with the sensor z. How much overrun should I allow for? I guess when it’s travelling at speed something like 5-10mm would be better?


Sent from my iPhone using Tapatalk

You need about the same length as a piece of string! All depends on the weight of the gantry, your approach speed for homing (crashes at rapid speed will hopefully be avoided by soft limits once the machine is homed which is the first thing you will do after switching it on) and some stuff to do with drivers that other regulars will understand better than me.

Your Z and other axis (it's Y on my machine but X on many) sensors are right. In practice the overlap of the sensor and your target will not be very much when it triggers. I put slots in the mountings of my targets to make things adjustable but this does increase the risk of something moving and messing up the repeatability of homing.

Kit

[JAZZCNC]

I haven’t looked at the data sheet for the sensor but. I’d assumed that it would be triggered 2 or 3mm before contact and I could then have the hard stop almost flush with the sensor z. How much overrun should I allow for? I guess when it’s travelling at speed something like 5-10mm would be better?


Sent from my iPhone using Tapatalk

The distance is determined by the sensor spec, if using just for homes then 2-3mm won't be a problem but if using for limits then usually you will be traveling at fairly high velocity when tripped so the inertia will easily travel 1-2mm if at high feeds.
Also, the accuracy and sensitivity are affected by distance, so it's best to keep the distance on the smaller side of the sensor spec. This way it will react faster but obviously if end on you have less room to stop. 90deg is a much safer setup.

[JonnyFive]

Finally got around to sorting the proximity sensor bracket:

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I think I'm finally there with the design, still need to finalise the motor choice and sort out some sort of levelling feet - can't decide whether to add levelling casters, they're pretty expensive but probably worth the money if I ever need to move the machine. At the minute I've just got M12 nuts welded on to the base of each leg - they look a little small to me but it seems M12 feet are good for 1000kg each - should be enough!

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[routercnc]

I made some steel discs as targets for mine as the sensor will be more sensitive than on aluminium, but both will work.

[JonnyFive]

Just been pricing up the steel to make my frame, the price has gone through the roof!! Almost double what it was when I last looked!! Ouch!

[JAZZCNC]

Just been pricing up the steel to make my frame, the price has gone through the roof!! Almost double what it was when I last looked!! Ouch!

Tell me about it, and it doesn't just stop at the steel, aluminium has also gone crazy. The price of steel is also driving up the price of motors, ball screws and anything else made with steel. Then on top of this shipping costs have gone crazy.

[JonnyFive]

That’s all I needed to hear, how am I going to explain it to my missus?!?

[Clive S]

That’s all I needed to hear, how am I going to explain it to my missus?!?

Do you need to tell her :surprise:

[reefy86]

I am in the same boat as you. 2018 was the last time I was on here and almost was ready to start it after 2 years of learning and designing from some really top guys on here. It was so easy to source materials and mild steel box sections was cheap as hell but now as you say they have doubled in price and I can't even find any suppliers for ball screws and the ones I have for linear rails they only stock a few. Not even looked at the electronics side yet. Dont know if I should just save money and wait to see if things go down and new suppliers start selling or keep searching and hoping for the best.

[JonnyFive]

Tell me about it, and it doesn't just stop at the steel, aluminium has also gone crazy. The price of steel is also driving up the price of motors, ball screws and anything else made with steel. Then on top of this shipping costs have gone crazy.

Jazz - do you have a feel for how much things have increased overall? Has everything doubled? Just trying to estimate how much extra I need to find.

[JAZZCNC]

Jazz - do you have a feel for how much things have increased overall? Has everything doubled? Just trying to estimate how much extra I need to find.

Oh Yes, I certainly have a feel for it, every month I feel like I've been Butt F^@£ by one supplier or another. Steel has indeed doubled at least and Aluminium tripled for some grades.

This isn't just in the UK either, Even China and Asia are struggling with the rising material cost's. I have never had a Chinese or Taiwanese suppliers apologise because they are increasing prices and in the last 3 weeks I've had 4 suppliers all say the same thing.

On top of this, the cost of shipping has gone crazy, container prices used to be around £2000, now they are anywhere between £10,000 to £12,000 and taking longer to arrive IF you can get them on a ship.!

Airfreight you need to sell a kidney if it weighs more than a mouse. I've just paid £560 to fly 2 ATC Spindles over that would have cost £120 before Covid started, Why when planes are sat on the ground with no passengers.?

I used to fly most of my stuff over a few machines worth at a time, Now I'm shipping by sea freight 20 or 30 machines worth at a time and motors etc by the 100's just so I can keep continuity and be sure prices are kept sensible. The downside being I'm weeks and months behind waiting for stuff to arrive and I'm paying more for the privilege.!

It's the same with Steel and aluminium, I used to buy steel box section 5 or 6 lengths at a time, enough for a couple of machines. Now the only way I can get sensible prices is to buy 30 lengths. Sheet steel is even worse, I'm paying the same now for 3mm as I paid for 10mm 6 months ago.

I would allow at least 40% extra to what you probably think was going to cost.
If you are serious about building then I wouldn't wait for prices to come down either because I don't think it's going to happen any time soon and it's still going up with no sign of coming down.

[reefy86]

Careful Dean we will be adding to your delivery soon �� I am hoping mine doesn't come to more then £6k if I'm honest but if it does I'll sweet talk the Mrs a little more

[JonnyFive]

If you are serious about building then I wouldn't wait for prices to come down either because I don't think it's going to happen any time soon and it's still going up with no sign of coming down.

I was thinking the same, I could be waiting for years for prices to come down, best to just crack on and suck it up.

[JonnyFive]

Oh, and don’t tell the missus [emoji6]

[JAZZCNC]

That’s all I needed to hear, how am I going to explain it to my missus?!?

Usually telling them after it is built works best...:highly_amused: Esp, If you want a divorce..:stupid:

[JonnyFive]

I'm trying to finalise the ball screw design and noticed that the standard dimensions from BST don't seem to be compatible with the FK15A bearings - looks like the spacers eaither side of the bearing are too long and there's not enough length to get the locknut on the end:

30108

Am I missing something? Do I have to turn down the spacers? I'm planning on tweaking the end to have 2 locknuts rather than using the grubscrew, just want to make sure I'm doing it correctly.

Cheers,

[Clive S]

I'm trying to finalise the ball screw design and noticed that the standard dimensions from BST don't seem to be compatible with the FK15A bearings - looks like the spacers eaither side of the bearing are too long and there's not enough length to get the locknut on the end:

30108

Am I missing something? Do I have to turn down the spacers? I'm planning on tweaking the end to have 2 locknuts rather than using the grubscrew, just want to make sure I'm doing it correctly.

Cheers,

Have you purchased the ball screw and bearing FK15A from Fred if so he should have machined it to match the bearing.

Also did you tell him the "F" length you wanted it is normally 15mm as standard but I usually tell him to make it 30mm so as to get more space for a pully.

I am not familiar with that bearing.

[JonnyFive]

It's been slow progress over the last few months. I've spent the last month or so trying to work out how much this thing is going to cost me, looks like it's going to be around £5.5k.

Here's what I got so far:

Steel box section for the frame:

I have scavenged some 80x80x3 box section from work; I have redesigned the top of the frame and the main leg uprights to use this, the rest will be 60x60x5 & 60x120x5 as previously planned. The price of steel is insane at the moment, it's going to cost £750 for the rest of the steel I need - my original cost was £500 when I priced up the entire frame a couple of years ago!! I've been trying to figure out if I've over engineered it, compared to most other designs I've looked at I seem to have an awful lot of steel in there.

Parts from BST:

Original HIWIN Brand Linear guide
2pcs HGR20-L1900mm Linear rail
2pcs HGR20-L1450mm Linear rail
2pcs HGR20-L400mm Linear rail
8pcs HGW20CC-ZA-C Carriage
4pcs HGH20CA-ZA-C Carriage
=USD629.00

Our own Ballscrew Assemble Set
2set RM2010-L1770mm ball screw with SFU2010 Ballnut
1set RM2010-L1480mm ball screw with SFU2010 Ballnut
1set RM1605-L322mm ball screw with SFU1605 Ballnut
All with end machining according your need,1770/1770/1480/322mm is the TOTAL length for each

3pcs 2010 Ballnut Housing
1pcs 2010 Ballnut Housing

1pcs OD25-8x10mm Jaw Coupling
1pcs MBA12 Motor Bracket
USD182.00

2set FK15/FF15 End support-Superior type,FK with P5 grade Angular contact bearing and FF with better deep groove ball bearing
1set BK15/BF15 End support-Superior type,BK with P5 grade Angular contact bearing and BF with better deep groove ball bearing
1set FK12/BF12 End support-Superior type,FK with P5 grade Angular contact bearing and BF with better deep groove ball bearing
6pcs M15x1 Locknut
2pcs M12X1 Locknut
USD145.00

1set 2.2kw spindle motor set=1pcs 2.2KW 220V 4 bearing motor+VFD+80mm Clamp+Water pump+Pipe
USD265.00

6pcs HTD-5M-20Teeth-15mm Wdith Pulley
4pcs HTD-5M-15mm Width-250mm Belt
USD22.00

1pcs 1000mm 25x38mm Cable chain with end connector
2pcs 1300mm 35x75mm Cable chain with end connector
USD26.00

Weight is about 57kg,discounted freight is USD650.00,so totally is USD1919.00.

= £1417

Aluminium extrusion for gantry:

2 off 160 x 80 x 1620mm (with drilling / tapping) = £1064

Aluminium tooling plate:

I've calculated approx £500. I was hoping to get these made for me but there is a maker space recently opened up near me that has a CNC mill so I am thinking it will save me some cash and be a good introduction to CNC to sign up and make them myself.

Closed loop steppers & drivers = £500

Electronics:

I've estimated £500 to cover the PSU, enclosure, cables etc - is this about right?

Miscellaneous:

Estimated around £500 (not including PC and software)


Is there anything obvious I have missed? Are my estimates about right?

I have reworked my frame to include the 80 x 80 x 3 that I have, I used it on the machine bed and the main uprights - I figured the bigger second moment of area compared to 60 x 60 x 5 would make these parts stronger. The frame now looks like this:

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I am also pondering whether to have just a single aluminium extrusion for the gantry to save a bit of money. I can see that it adds a lot to the stiffness to the gantry but £500 each piece is a big investment. I have seen people get pretty good results on lesser machines with far smaller gantry sections. For example a single 160x80 section has a second moment of area 22x greater than a gantry made from C-beam. I'm not 100% convinced the extra cost will result in a significantly better machine - interested to hear what people think of this?

This is how the machine looks now:

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[JonnyFive]

Things just got very real, just ordered all the steel for my build!!!

[JonnyFive]

Finally the first step to making this thing a reality, excuse the terrible welding!!!

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[m.i.k.e]

Great start, the thing about welding is that it doesn't matter what it looks like as long as it's strong which that looks as tho it is. It can be tarted up later with a grinder or flap disc and it's not easy to get neat welds with mig on thick material unless you have a really powerful machine and then it just pulls out of alignment more.
Mike.

[JonnyFive]

Thanks Mike!

I have a 150Amp welder but I'm not convinced that's what it actually puts out, think it's a rebadged Chinese POS but I was given it free so can't complain. There are so many welds on this thing that I don't intend grinding everything back - life's too short! As long as it holds together I'll be happy, I'm just chuffed to see some progress.

Cheers :beer:

[JAZZCNC]

it's not easy to get neat welds with mig on thick material unless you have a really powerful machine and then it just pulls out of alignment more.
Mike.

Not strictly true, with the correct setup and a skill full welder then even a cheap welder can give excellent welds on thick material without too much pulling or distorting as you can see on these pictures of machine we made, one is 5mm plate onto 10mm done with a Cheap £150 180A Ebay Mig, the other is this base frame with some long welds on10mm plate.

You can see the Mig in the pic of the base frame and if you zoom in you can see 10mm pads welded to a 10mm plate, nothing pulled on this frame. Full disclosure here this was My Son Jareds (Jazz) welding, not mine, my eyes are knackered so my welding days are done.!

This said practice makes perfect and a grinder mask's 1000 sins until something falls off...:hysterical:

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[Doddy]

You can see the Mig in the pic of the base frame and if you zoom in you can see 10mm pads welded to a 10mm plate, nothing pulled on this frame. Full disclosure here this was My Son Jareds (Jazz) welding, not mine, my eyes are knackered so my welding days are done.!


...and to the left of the welder, the ubiquitous DeWalt grinder :)

All seriousness - that's a nice job - surprised that's the result of MIG, approaching TIG quality. Impressive.

[m.i.k.e]

Originally Posted by JAZZCNC >> Not strictly true, with the correct setup and a skill full welder then even a cheap welder can give excellent welds on thick material without too much pulling or distorting as you can see on these pictures of machine we made, one is 5mm plate onto 10mm done with a Cheap £150 180A Ebay Mig, the other is this base frame with some long welds on10mm plate.

I was just trying to keep his chin up, now you have posted them pics up JonnyFive will have an inferiority complex :hysterical:

atb Mike.

[Neale]

Is it a complex if you know you are inferior?

My welding is crap but it's good enough that my machine has stayed pretty accurate and hasn't fallen apart in the few years I've been using it. I just don't show it to people...

But don't forget the angle grinder!

[JAZZCNC]

I was just trying to keep his chin up, now you have posted them pics up JonnyFive will have an inferiority complex :hysterical:

atb Mike.

Somehow I don't think JohnyFive is a snowflake so I'm sure he'll be fine....:hysterical:

But in all seriousness, the point of my post was more to let people know that even a cheap Mig can produce very nice welds even on thick-ish material. Yes, 10mm is pushing the limit of a cheap welder but it can be done.

[JAZZCNC]

...and to the left of the welder, the ubiquitous DeWalt grinder :)

Yes, the good old Dewalt grinder and it's got the Evil wire brush on it.:devilish:


All seriousness - that's a nice job - surprised that's the result of MIG, approaching TIG quality. Impressive.

If you think that's good you should see the welds that he does with the big German-made EWM Mig welder.!....That thing is amazing and the speed it welds at is unbelievable, the control panel is like a spaceship, you tap in a code for the material and type of weld joint you are doing and it sets all the settings amps. volts, wire feed, etc and monitors them as you weld, you basically pull the torch along and the metal just flows like water, he says it almost feels like cheating because it's so easy.

My reply is " So it bloody well should @ £6k"....:hysterical:

[JonnyFive]

It takes more than that to upset me [emoji1787] I know my limitations but I’m happy that this thing is strong enough to do its job. The vast majority of the welding I’ve done so far won’t be visible, hopefully I’ll improve a little by the time I get to the bits you’ll see.

I know you shouldn’t blame your tools but tonight I borrowed a friends inverter MIG welder and it seems to produce nicer welds. With only 4 power settings on my welder it always seems that the right level is in between settings. The other welder has infinitely adjustable Voltage and feed speed so it’s easier to get right.

That’s some seriously nice looking welding there Jazz, maybe by the end of this project I’ll be 1/10th as good as that!

[JonnyFive]

Making good progress on the fabrication work [emoji1303]

https://uploads.tapatalk-cdn.com/20220318/6fef89ee6dea8cb24d84ab51d4f8f7a1.jpg

[m.i.k.e]

Looking good, I'm going to have to get some steel ordered and make a start or that will be another year passed lol. That's going to be one strong machine with that bracing.
atb mike.

[Doddy]

Looking good [...] That's going to be one bloody heavy machine with that bracing.

There you go, fixed it for you :)

[JonnyFive]

That's going to be one strong machine with that bracing.

Yep, strong and heavy - CAD says the fabrication is over 370kg!!!!!


Sent from my iPhone using Tapatalk

[JAZZCNC]

Yep, strong and heavy - CAD says the fabrication is over 370kg!!!!!


Sent from my iPhone using Tapatalk

Careful not to get caught up in the "Heavy is good" trap because heavy in the wrong places can be just as bad as underbuilding.?
At least if you are underbuilt you can take lighter cuts and go faster but too heavy and you'll struggle to hit feed rates or suffer from missed steps through motors not being powerful enough to handle the inertia and as we all know it's a lot easier to put weight on and beef up than take it off and a lot cheaper if your too heavy and end up having to replace motors and drives etc.

[JonnyFive]

Understood Jazz. The 370kg is for the welded (static) base frame, I thought mass here would help with damping? The vast majority of the moving bits are aluminium, I haven’t worked out the total mass of the gantry perhaps that’s something I should do?

[JAZZCNC]

Understood Jazz. The 370kg is for the welded (static) base frame, I thought mass here would help with damping? The vast majority of the moving bits are aluminium, I haven’t worked out the total mass of the gantry perhaps that’s something I should do?

Yes nice thick tubes etc will certainly help to dampen vibrations and without a doubt, you need to look at the gantry weight and screw sizes you'll be using to help with motor selection, etc. Mass in the gantry certainly helps here as well but this does come at a high cost with motors etc and isn't always needed so it's worth taking the time to work out the weight you'll be moving.

[JonnyFive]

Frame nearly fully welded and ready for paint [emoji41]

This thing is a beast!

https://uploads.tapatalk-cdn.com/20220524/5bc7279497fe903d0a6ce68c7a1bfbcb.jpg

https://uploads.tapatalk-cdn.com/20220524/9bdb7465790cce9be8392a31975511c7.jpg

https://uploads.tapatalk-cdn.com/20220524/52622226e0ffb466adbb81ee406b0af6.jpg

[JonnyFive]

Got the frame as level as possible and poured the epoxy this weekend:

31165
31166
31167
31168
31169
31170

Overall I'm very happy with it, there's only one area I can see that has a slight wave to it, think I either cooked it with the blow torch or hit it too late and the epoxy was too solid to smooth itself out. I don't think it will be a problem, I'll see once I get to fitting the rails and fill / shim if required.

[JonnyFive]

Can anyone suggest what size cable chain I’ll need for each axis please? Just about to place an order with BST and was going to add these to the order.

[emoji482]

[JonnyFive]

Anyone got any recommendations on the safest way to pay BST? Direct through Aliexpress or via Paypal?

[pippin88]

I've done multiple orders from BST Automation direct through AliExpress.

The few people I have seen online that have had any issue with initial order seem to have had issues sorted fully by BST (Fred)

[JAZZCNC]

Anyone got any recommendations on the safest way to pay BST? Direct through Aliexpress or via Paypal?

Fred is 100% trustworthy so pay him any way you are most comfortable or suits you best. I pay him directly through bank transfer and have done for 10+yrs without any issues. (unless I cock it up like I did the last order, but still got sorted by Fred)

[Lee Roberts]

Don't forget to mention MYCNCUK when you speak to him, he likes to look after members if he knows you've come from here ;-)

[routercnc]

Last time I used Aliexpress they used an intermediate holding area (escrow?) for my payment and it was only released to the seller when I received it. I’m pretty happy with that. Also if it is Fred then no problems.

[JonnyFive]

Is it normal to have to pay import duty to the delivery courier? I’ve had 2 packages from China, from 2 different suppliers - one from BST was delivered no problem, the second with my motors the delivery guy said I have to pay import duty. Just wondering whether I got lucky on the first one or I’m being shafted by the second?

[m_c]

Is it normal to have to pay import duty to the delivery courier? I’ve had 2 packages from China, from 2 different suppliers - one from BST was delivered no problem, the second with my motors the delivery guy said I have to pay import duty. Just wondering whether I got lucky on the first one or I’m being shafted by the second?

Entirely normal, if the cost is over £135.
Under £135, the seller should be VAT registered, and collect the VAT on the UKs (and I think it's also came in for the EU) behalf. If you paid through an online marketplace (aka eBay, Aliexpress), then they have to do the VAT collection.

As for the one you didn't have to pay, give it a month. Some couriers deliver, then send you the bill. Others bill you before they'll deliver.
You might have been lucky. I know I've never been billed for some orders in the past, but generally higher value stuff doesn't slip through the HMRC net.

[JonnyFive]

Entirely normal, if the cost is over £135.
Under £135, the seller should be VAT registered, and collect the VAT on the UKs (and I think it's also came in for the EU) behalf. If you paid through an online marketplace (aka eBay, Aliexpress), then they have to do the VAT collection.

As for the one you didn't have to pay, give it a month. Some couriers deliver, then send you the bill. Others bill you before they'll deliver.
You might have been lucky. I know I've never been billed for some orders in the past, but generally higher value stuff doesn't slip through the HMRC net.

Good to know, thank you!! I’ll brace myself for the upcoming bill on the BST delivery [emoji33]

[JonnyFive]

I’ve pretty much got all my hardware now(gantry extrusion, bearings, ballscrews, motors & drives etc), all I need is the machined parts to be able to start assembly - just waiting on my induction at the local maker space so I can start work on the missing pieces [emoji41]

https://uploads.tapatalk-cdn.com/20221105/1caea499a18a89e9ba4359509a7ce973.jpg

My mind is starting to think about the electronics, this is where my knowledge falls down big time!! I’m not sure where to start really. I think Ethernet is the way to go, I’m thinking UCCNC. I have closed loop stepper motors (not sure did that makes a difference?). Apart from that I’m snookered. Can anyone point me in the right direction please?

[emoji482]

[JonnyFive]

Whilst progress is slow on machining all the parts I need I have put together my attempt at the contrrol circuitry. I have to give a massive shout out to both ROUTERCNC & Joe Harris for their superb videos and documentation covering this side of things - I've watched / read it all several times!!! Using their content, some intense Googling and reading of manuals this is what I've come up with:

31390
31391

I do have a number of questions, hopefully someone will be able to help:


Is a mains filter required for the VFD? I notie=ced ROUTERCNC used one but Joe didn't
I'm assuing I don't need to connect up REV on the VFD as I'll only be running the spindle in one direction?
I've seen diffferent ways of connecting up the step & direction pins from the motor drivers - either commoning up the +ves or the -ves - what's the difference? Is it to do with picking up the leading or trailing edge of the signal? Which should I use? I'm using closed loop steppers if it makes a difference.
My motors came with long cables with extensions - are they ok to use? Or should I be making up my own screened cables?
Do I need to run an earth wire to the gantry & frame?
Is the rotary interlock switch necessary?
Do I need to connect the spindle pin 4 to earth? I've read contradictory things about this.
Do I need to connect the ENA+ & ENA-?
Do I need to twist the PUL & DIR wires?
Is it acceptable practice to crimp 2 wires into one ferrule? Or put 2 ferrules into a single terminal?
Should all the 24V feeds going to the AXBB-E controller be from the switched 24V or permanent supply?



I'm sure there will be many more questions to come. Any feedback would be much appreciated.

Cheers :beer:

[Doddy]

1. The filter is more to protect the supply (and other devices) than the VFD.... they're noisy buggers.
2, Correct
3. Closed-loop makes no difference. Whether you're driving high or low is largely irrelevant (the two pins are the anode/cathode of an internal LED used for isolation - so switching either works). What this gives you though is flexibility - for example an open-collector (open drain) drive is designed for low-side switching (i.e. take the + to supply, and switch on the -). The axbb manual describes the non-isolated outputs as being able to push/pull 20mA - so can source (+ve) or sink (-ve) - so can drive either input.
4. Your call. It's better to cut to length but not if you risk damaging anything.
5. Yes. Unequivocally. Do I?, I might.
6. I only glanced at your schematic - it feels a safe design but more than I'd do for a personal machine. I can't knock safe design but I can duck an errant shock 50% of the time.
7. It's a good idea. Otherwise a stray wire in the spindle could short to the enclosure and zap you. Of course your protective earth will then ensure that you brick your VFD before your blow the protective devices.
8. No. Unconnected, the LED opto-isolator remains inert and the drivers enabled.
9. It's a good idea, but realistically will achieve little. You'll be generating pulses at maybe 100kHz at around 5mA, that will generate some EMF but I'd hazard a guess that you're not going to impact much. The driver inputs going through an opto isolator will be pretty tolerant of any induced emf.
10. Yes, in fact I have insulated ferrules that accept two cores (i.e. a wide rectangular receptacle rather than round), Use common sense - if the cores fit comfortably then there's nothing wrong. Test each crimp.
11. I'd go for the permanent supply, otherwise you can end up with pull-lows on outputs when you don't intend this (remember, you still have a 0V supply to the AXBB, it's capable of hard-driving low). But remember I've not really looked at your schematic.

[JonnyFive]

Thanks Doddy, appreciate the feedback.


1. The filter is more to protect the supply (and other devices) than the VFD.... they're noisy buggers.
I see, so it's to protect things upstream of the VFD on the same mains circuit?


2, Correct
:thumsup:


3. Closed-loop makes no difference. Whether you're driving high or low is largely irrelevant (the two pins are the anode/cathode of an internal LED used for isolation - so switching either works). What this gives you though is flexibility - for example an open-collector (open drain) drive is designed for low-side switching (i.e. take the + to supply, and switch on the -). The axbb manual describes the non-isolated outputs as being able to push/pull 20mA - so can source (+ve) or sink (-ve) - so can drive either input.
Thanks for the explaination, I'll leave them as they are.


4. Your call. It's better to cut to length but not if you risk damaging anything.
I'm fine with cutting them to length.


5. Yes. Unequivocally. Do I?, I might.
I'll add one in.


6. I only glanced at your schematic - it feels a safe design but more than I'd do for a personal machine. I can't knock safe design but I can duck an errant shock 50% of the time.
I'm still in 2 minds, it looks cool but isn't really doing anything that the switch on the mains socket doesn't do other than stop you going in the cabinet which I wouldn't do.


7. It's a good idea. Otherwise a stray wire in the spindle could short to the enclosure and zap you. Of course your protective earth will then ensure that you brick your VFD before your blow the protective devices.
Easily solved, I can add it. I've also seen people saying you need to open up the spindle and check that pin 4 is actually connected to the spindle body, I'll check this too.


8. No. Unconnected, the LED opto-isolator remains inert and the drivers enabled.
:thumsup:


9. It's a good idea, but realistically will achieve little. You'll be generating pulses at maybe 100kHz at around 5mA, that will generate some EMF but I'd hazard a guess that you're not going to impact much. The driver inputs going through an opto isolator will be pretty tolerant of any induced emf.
I'll do it anyway.


10. Yes, in fact I have insulated ferrules that accept two cores (i.e. a wide rectangular receptacle rather than round), Use common sense - if the cores fit comfortably then there's nothing wrong. Test each crimp.
:thumsup:


11. I'd go for the permanent supply, otherwise you can end up with pull-lows on outputs when you don't intend this (remember, you still have a 0V supply to the AXBB, it's capable of hard-driving low). But remember I've not really looked at your schematic.
I don't fully understand what you've said but will swap to the permanent 24V supply - sounds like it's the way to go.

[Lee Roberts]

I've also seen people saying you need to open up the spindle and check that pin 4 is actually connected to the spindle body, I'll check this too.

You could probably check this with a multi meter rather than take it apart and brake any seals etc...

[JAZZCNC]

#4 Depends on the quality of the wire, the wire on the Lichuan motors we use isn't shielded and we never have any noise issues from it, only on very long wire runs ie: 8x4 or 10x5 machines do I tend to fit shielded cable but even then it's only precautionary thing and I doubt would have trouble based off the other machines we built.

#7 We don't connect this as it's given me problems in the past with noise, if the chassis/gantry is earthed then you won't have any issues.

#11 Permanent 24v and 5V supply otherwise you'll drop power to the Axbb-e and lose your Workoffset if you haven't saved it first, UCCNC only saves the Workoffset on shut down so if you haven't saved the offset then it will be lost with a power cut. It's also a pain in the arse having to restart UCCNC, reload the G-code etc just for an E-stop.

[JonnyFive]

You could probably check this with a multi meter rather than take it apart and brake any seals etc...

Thanks Lee. I have done a continuity test and can confirm pin 4 is connected to the spindle housing.

Cheers

[JonnyFive]

#4 Depends on the quality of the wire, the wire on the Lichuan motors we use isn't shielded and we never have any noise issues from it, only on very long wire runs ie: 8x4 or 10x5 machines do I tend to fit shielded cable but even then it's only precautionary thing and I doubt would have trouble based off the other machines we built.

I'm assuming this is something I could easily upgrade if the need arises once I'm up and running? The cables I have came with 3m extension cables, hopefully these will be long enough.


#7 We don't connect this as it's given me problems in the past with noise, if the chassis/gantry is earthed then you won't have any issues.

OK, I'll leave it un-connected. The cable from the VFD to the spindle needs to be shielded but with the shielding only connected at the VFD end and not to the spindle connector - is this correct?


#11 Permanent 24v and 5V supply otherwise you'll drop power to the Axbb-e and lose your Workoffset if you haven't saved it first, UCCNC only saves the Workoffset on shut down so if you haven't saved the offset then it will be lost with a power cut. It's also a pain in the arse having to restart UCCNC, reload the G-code etc just for an E-stop.

I'm referring to the 24V to the isolated inputs, the 24V and 5V power connections to the AXBB-E are permanently connected. Should the isolated inputs be permanent too?

Cheers

[Lee Roberts]

The cable from the VFD to the spindle needs to be shielded but with the shielding only connected at the VFD end and not to the spindle connector - is this correct?

Yea and do the same with the control/comms wire to/from the vfd, except connect that earth to your main star ground in/at the cabinet end.

No ground loops etc...

[JonnyFive]

Yea and do the same with the control/comms wire to/from the vfd, except connect that earth to your main star ground in/at the cabinet end.

No ground loops etc...

You mean the wires going to DCM / FOR / ACM / VI on the VFD?

[Lee Roberts]

You mean the wires going to DCM / FOR / ACM / VI on the VFD?

No, sorry I meant to say shielding not earth, but yes the shielding for that group of wires, not the connections themselves...

So I'm talking about the control wire you would also install so that the main cnc controller can control your VFD from software.

Also, I think you should choose Doddy's advice and mine on this one and definitely connect Pin 4, it costs nothing to do and I too would rather sleep well at night knowing your/my spindle housing is properly wired to be safe in a fault condition.

Earth/ground is there for safty first and should be used as intended, using it for noise drain should be considered as a secondary bonus feature in this application in my opinion.

Noise issues can be isolated and remedied, restarting your heart isn't as easy to do...

[JonnyFive]

I have updated the schematic:


Earth wire from VFD to pin 4 on spindle added.
VFD to spindle cable screened with screen attached to ground.
DCM / FOR / ACM / VI wires all screened and earthed.
Isolated inputs connected to permanent 24V.



31542

[JonnyFive]

Finally a bit of progress to report. It's taken way longer than I'd hoped to make up some of the aluminium plates for the gantry mounting but did the first fit up last night and I'm happy with how it looks:

31807
31808
31809
31810
31811

Without having a definitive datum to work from this is how I set my first linear rail:

31812

Is there a better method for ensuring the rail is straight?

:beer:

[JonnyFive]

Is anyone able to shed some light on how I size my transformer for the motors? I have 3 x 5.5Nm Nema 24s and 1 x 4.5Nm. The motor data sheet says current = 5.8A and the driver max peak current = 6A. Is it just a case of adding them all together? Do you downgrade a bit based on the assumption not all motors will be drawing max current at the same time?

[m_c]

Generally for 4 motors about 50% of total combined capacity will give plenty head room.

I generally go for 50%, then round up to the next transformers size if going for an unregulated supply.

[JonnyFive]

Generally for 4 motors about 50% of total combined capacity will give plenty head room.

I generally go for 50%, then round up to the next transformers size if going for an unregulated supply.

Thanks for the feedback. I’ve asked around in a few places and been told multiple things from 1/3 to 125% of the total current rating which hasn’t made anything any clearer. Let alone the type of power supply - do I go for a switching PSU or just a transformer? AC or DC? I’m still not sure where to go.

This article seems like a good starting point:

http://www.geckodrive.com/support/power-supply-basics/

[m_c]

Gecko is a good resource, as it's written by people who actually understand how drives work, and the principles.

1/3 is probably OK if you're not pushing the motors to their maximum speed with high acceleration.
125% is most definitely a figure thought up by somebody who doesn't understand the power requirements of a stepper motor.

My preference is for a basic unregulated supply, with a transformer, rectifier and diode, however I normally used drives that use a basic DC input and dump energy back into the supply under decelleration. If you're using drives that accept a DC or AC input, then they don't do that (the drive input is rectified, so can't physically dump energy back out it), and I'd pick whatever power supply will physically fit better.

[Neale]

The main reason for using one of the cheap Chinese switch-mode power supplies is that they are cheap, small, light, and cheap. And did I say cheap? However, as has been mentioned in this thread and also alluded to in the Gecko document, they do not suffer overload gracefully. That is, they will trip out if they detect any combination of overload, overvoltage, or whatever (and assuming that the protection circuitry is up to it) and the stepper drivers do not like this - any loss of power is going to mean at best restarting the job and at worst a ruined job as the software has now lost control of machine position. That is why a SMPS needs to be over-rated for the load for those rare just-in-case situations when all the drivers are hitting peak load together. The "linear" power supply - transformer, rectifier, capacitor - will, within reason, accept peak overloads without flinching and just carry on, as long as the average load is within its capabilities. This is why they seem to typically be under-specified as the stepper motors only demand peak current in relatively short bursts and seldom all together.

As m_c says, it used to be the case that stepper drivers would only accept DC and you therefore needed some kind of power supply for them. These days, there seem to be more and more drivers around that will accept an AC input of the appropriate voltage directly and contain all the circuitry needed to generate DC internally. Then you just need the corresponding transformer and it's all a lot easier.

I have a CNC router and CNC mill in my workshop that use the classic transformer/rectifier/capacitor combination, and a CNC lathe that I am currently updating which uses newer drives which accept AC. All of these work just fine. I do use the cheap Chinese SMPS boxes, but for some combination of 5V/12V/24V for the control electronics depending on the machine. The SMPS boxes are fine for that application.

[JonnyFive]

The main reason for using one of the cheap Chinese switch-mode power supplies is that they are cheap, small, light, and cheap. And did I say cheap? However, as has been mentioned in this thread and also alluded to in the Gecko document, they do not suffer overload gracefully. That is, they will trip out if they detect any combination of overload, overvoltage, or whatever (and assuming that the protection circuitry is up to it) and the stepper drivers do not like this - any loss of power is going to mean at best restarting the job and at worst a ruined job as the software has now lost control of machine position. That is why a SMPS needs to be over-rated for the load for those rare just-in-case situations when all the drivers are hitting peak load together. The "linear" power supply - transformer, rectifier, capacitor - will, within reason, accept peak overloads without flinching and just carry on, as long as the average load is within its capabilities. This is why they seem to typically be under-specified as the stepper motors only demand peak current in relatively short bursts and seldom all together.

As m_c says, it used to be the case that stepper drivers would only accept DC and you therefore needed some kind of power supply for them. These days, there seem to be more and more drivers around that will accept an AC input of the appropriate voltage directly and contain all the circuitry needed to generate DC internally. Then you just need the corresponding transformer and it's all a lot easier.

I have a CNC router and CNC mill in my workshop that use the classic transformer/rectifier/capacitor combination, and a CNC lathe that I am currently updating which uses newer drives which accept AC. All of these work just fine. I do use the cheap Chinese SMPS boxes, but for some combination of 5V/12V/24V for the control electronics depending on the machine. The SMPS boxes are fine for that application.

Thanks Neale, really appreciate you taking the time for such a detailed response.

These are the drivers I have:

https://uploads.tapatalk-cdn.com/20231009/705856c0506f93c49dbf707871b3a171.jpg

JazzCNC suggested running them at 55VAC and just using a transformer which is what I have in my control schematic.

I’m not looking to build this on the cheap, I want it to be right and I want it to be reliable. Although I can move my gantry easily turning the ballscrews by hand the gantry will be heavy when it’s finished, I’m guessing 50kg, so there will be momentum creating voltage spikes and the system needs to tolerate them.

[Neale]

Decent drives, and I would be happy using 55V AC with those.

I have a home-built CNC router, roughly 1500x750mm cutting area, and the gantry is about 1m long and fairly heavy - especially with a decent spindle motor on it! I drive it with 2 20mm ballscrews. 5mm pitch as 10mm wasn't so common back when I built it, and given that most of my work is smaller but needs a lot of XY movement (i.e. not just long straight cuts) actually that's not too bad a compromise, and I can still get 5m/min out of it which I find acceptable. Personal choice there, and reflects the kind of work I do. Classic "your mileage may vary" situation! However, when you do the sums, you might be surprised to see just how big a component the rotational inertia of the ballscrews contributes to the torque needed to accelerate and decelerate it. Very roughly, on my machine, the ballscrews need about as much torque to get them turning at speed as the gantry itself needs. Surprising result, but this is exactly why some aspects of machine building are not intuitive. 25mm ballscrews would significantly reduce performance purely due to inertia, and why NEMA34 motors often reduce and not improve performance over NEMA23/24 for this size machine.

What you might want to consider when you get to that point is stepper motor current. There are endless arguments about whether the data sheets talk about average, RMS, peak, etc, current. All are different, and usually you don't know which the motor manufacturer is quoting. I would go out on a bit of a limb here and upset the purists by saying that those data sheet values are only a starting point. Basically, the more current you can put through the motor the better it will perform, but the hotter it will get. So my technique is to start with data sheet values, then check the motor casing temperature after the machine has been used for a bit. If you can comfortably hold the motor, then crank the current up a notch. If it's just a bit too hot to hold, turn the current down a bit. Stepper motors typically run hotter than you might expect. Once you have the current about right, then you can finish tuning the machine max acceleration and speed parameters, knowing that you are getting about the best performance available. Other opinions are available...

[JonnyFive]

Any thoughts on these transformers? Are they up to the job?

https://uk.rs-online.com/web/p/toroidal-transformers/2238314

This one has the same output for a lot less spend:

https://amzn.eu/d/j9rrGWB

A bit more grunt for a little bit more cash:

https://www.rapidonline.com/vigortronix-vtx-146-625-255-toroidal-transformer-625va-0-55v-88-3845

[Neale]

I'm using a couple of Vigortronics transformers myself. Seem to do what they say on the tin! I bought from Rapid but only because I didn't know they were available via Amazon...

500VA is probably enough although because the price difference was small at the time, I went up to 650VA for my router.

[JonnyFive]

I'm using a couple of Vigortronics transformers myself. Seem to do what they say on the tin! I bought from Rapid but only because I didn't know they were available via Amazon...

500VA is probably enough although because the price difference was small at the time, I went up to 650VA for my router.

That’s good to hear some real world feedback, think I might be reaching a conclusion on this……

Based on the Gecko recommendations of 1/3 total current I’d need a 425VA transformer. I’m inclined to go a bit bigger so the transformer isn’t working so hard - if I go for 625VA that takes me to roughly 50% total current as you suggested Neale.

Just to clarify for my own sanity:

1) What are the consequences if I’ve under rated the transformer? The motors will struggle in the situation that they’re all maxed out? How does this actually manifest itself? Motors stall? Feed slows down and start to get rubbing on the cutter?

2) You mentioned checking the motor temperature and adjusting the current - how do you adjust it? Is it a software setting?

3) If I want to add an extra motor sometime in the future (4th axis) I can just add another transformer and wire it in parallel to the first one to give more grunt?

4) The drive accepts AC, I don’t need any kind of smoothing or additional circuitry - just wire direct to the drives from the transformer?

Thanks for your help [emoji482]

[Neale]

1) What are the consequences if I’ve under rated the transformer? The motors will struggle in the situation that they’re all maxed out? How does this actually manifest itself? Motors stall? Feed slows down and start to get rubbing on the cutter?

2) You mentioned checking the motor temperature and adjusting the current - how do you adjust it? Is it a software setting?

3) If I want to add an extra motor sometime in the future (4th axis) I can just add another transformer and wire it in parallel to the first one to give more grunt?

4) The drive accepts AC, I don’t need any kind of smoothing or additional circuitry - just wire direct to the drives from the transformer?


1. With a significant overload, the transformer will overheat leading to breakdown of insulation and/or burnt out winding. However, with short-term overload (say, no more than a few seconds with 2x overload) you will not see any significant effect and the transformer isn't likely to suffer. Output voltage will drop slightly below the nominal value but not enough to worry the stepper drivers. The motors will not notice. And even that level of overload is unlikely. Go 625VA and be safe to add a fourth axis if you like.
2. After my last posting, I went back and looked at your picture of your drivers. I was surprised to see that there was no current control setting. Usually, some of the switches are used for setting maximum current. So maybe these drivers have some kind of software setting, or they are pre-configured for a particular current. Did they come with specific motors? If so, ignore what I said because the manufacturer has already dealt with this one!
3. As per 1 above, if you go for an over-rated transformer you could safely add a fourth axis - just wire it in parallel with the existing drivers. Fourth axis is usually rotary and unlikely to even take as much current as the XYZ motors. Or add another dedicated transformer? Do not wire a second transformer in parallel with the first! Their output voltages unlikely to match closely enough. You do not need any connections between the two transformers. However, I doubt that you would need that anyway.
4. Yes, just connect transformer secondaries directly to the AC in terminals on the driver. If at all possible, you are recommended to wire each driver directly to the transformer, probably via a terminal block of some kind which can take all the wires. Do not daisy-chain more than one driver together (i.e. wires go to first one then continue to the next). Whatever rectification and smoothing is needed by the driver is handled by its internal circuitry.

[m_c]

Just to clarify something on the current requirements, a 5A stepper motor won't draw 5A from the power supply, except in very specific circumstances which are not actually likely to occur.

Say a stepper is rated 5A at 10V while stationary (nice round figures for simplicity, but voltage is likely to be 3-5V for most common steppers), that means at idle, it will consumer 50W (5V x 10A).
If you power that via a 50V transformer, that means at idle the drive is only going to pull 1A (50W/50V). (assuming 100% efficiency - typical efficiencies are going to be in the 90s)

However, once the motor starts spinning, the motor requires more voltage to maintain the rated current due to the generated back emf, so at some point the drive will reach a point where there is not enough voltage for it to maintain the full 5A current, and this is the point where maximum power supply draw will be pulled. As you move above that point, which I'll call the peak power point, current draw will actually decrease.
However (yes another however!), stepper motors are not that efficient, so in practise the current actually drops of before reaching the peak power point, due to that pesky inductance which limits how fast the current can be changed in the coils.

[m_c]

@Neale those drives are software configurable.
I'm not entirely sure why they bother with microswitches for some settings, given other critical settings have to be set in software.

@JonnyFive if you need the software, I've got the install file for V2.1.8, which lists your drives.

[JonnyFive]

@Neale those drives are software configurable.
I'm not entirely sure why they bother with microswitches for some settings, given other critical settings have to be set in software.

@JonnyFive if you need the software, I've got the install file for V2.1.8, which lists your drives.

So there’s an app I need to configure the drivers? I did not know that. Presumably they are set to 6A from the factory, am I likely to need to change it?

[JonnyFive]

Just read the manual for the driver, looks like you need to connect via the comm port to tweak the current. I ain’t gonna do that [emoji1787] The manual says the current will be adjusted automatically.

[JonnyFive]

Let’s talk fuses, how does one work out what amperage to use? Just add up all the current draws within the circuit? Add a bit on top for luck?

[JonnyFive]

I've been researching wire sizing for my build and here's what I've come up with:

1) Cable from wall socket to cabinet - 3 core, 2.5mm2 flex
2) 240Vac within cabinet - 2.5mm2
3) Earthing - 1.5mm2
4) 24Vdc signals - 0.5mm2
5) Proximity switches - 3 core 0.5mm2 CY
6) VFD to spindle - 4 core 1.5mm2 CY
7) 55Vac within cabinet - 2.5mm2
8) A+ / A- / B+ / B- - 4 core 1.5mm2 CY
9) EGND / VCC+ / EA+ / EA- / EB+ / EA- - 1mm2 CY
10) PUl+ / DIR+ - 0.5mm2 twisted

How does that all sound?

:beer: