Luthier CNC

Minor update today as I have not made as much progress as I hoped.

Cut angles into the side plates using a table saw with a cheap aluminium blade I got from screwfix. Worked perfectly:
Attachment 25859

Started assembling machine only to realise I still have my paper templates on my aluminium plates. Started peeling these off and immediately realised using spray on contact adhesive was a huge mistake. Paper wouldn't come off. Used a Stanley knife blade to try to coax it off with limited success. Spent most of the day trying to clean the leftover gunk with acetone - managed to clean off half of one single plate (and not very well).

After dinner I realised I have lots of lighter fluid which I use for cleaning gunk off guitar finishes and tools. Thought this may be worth a try and it worked fantastically. Finished all of the plates in about 1.5 hours!

1 Douse the paper with lighter fluid
Attachment 25860

2 Leave for 1-2 mins to let it soak in and peel the paper off; dead easy
Attachment 25861

3 Kitchen roll doused in lighter fluid to gently wipe off any gunk - keep adding lighter fluid rather than elbow grease (avoids smearing the gunk around). Here are all the clean plates and extrusions ready to assemble:
Attachment 25862

Nice!

What table saw have you got?

I use blades by OX TOOLS (https://www.ffx.co.uk/tools/product/...6Mm-X-30-X-80T), check out FFX if your a Screwfix/Toolstation kinda shopper, service from them has been great, fast to post out to.

Toolstation have these blades as well but not quite the same size offerings, just got one of these for my circular saw as helping bro build a new workshop: OX TCT Circular Saw Blade 184 x 30 x 28T

Quote:

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Originally Posted by Lee Roberts

Nice!

What table saw have you got?

I use blades by OX TOOLS (https://www.ffx.co.uk/tools/product/...6Mm-X-30-X-80T), check out FFX if your a Screwfix/Toolstation kinda shopper, service from them has been great, fast to post out to.

Toolstation have these blades as well but not quite the same size offerings, just got one of these for my circular saw as helping bro build a new workshop: OX TCT Circular Saw Blade 184 x 30 x 28T

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I use the Triton TWX7 with the table saw module (I have the router table module too, which sees a lot of use in guitar building)
http://www.tritontools.com/en-GB/Pro...20Systems/TWX7

Had it about a year and a half and still everything works very well and no rust - happy with it overall.

Thanks for the links - the table saw needs 245mm blades w/ a 30mm mount - the best deal I found was at screw fix for about £30.

Build started in earnest:

1 Y axis rough assembly
Attachment 25869

2 Y axis ballscrew
Attachment 25870

3 X axis assembly beginning
Attachment 25871

The gantry seems to move on its rails without binding - more by luck than by any concerted alignment effort. I'm not sure what freedom of movement I should be expecting though. It doesn't keep rolling after its been pushed.

Here is a vid of it being moved by hand. Can someone please check if this looks and sounds about normal?
https://streamable.com/u1pd2

Also, I have tried securing the ballscrew nut to the gantry. This seems to work OK, but at both of the extremes of travel, the resistance does go up quite a bit. I think I need to align the ballscrew more accurately to stop this happening. I'm finding this quite difficult - is there any advice you kind folks can offer?

Sounds and looks about right to me, did you get the rails and bearings from fred @ BST?

I've just been setting up a bed axis lead screw and had the same problems last week, I noticed in your video that there was quite a gap between the ball nut mount plate and the ali extrusion that passes under the machine, I'd say you need to shim that gap to perfection, just take your time and have the plate screws just finger tight so you can see any movement the plate wants to do, its likely you'll need to get down to beer/coke can thickness for shim material.

Then when it looks like you've got it close, run the gantry up and down a few times, do this with the ball screw mounts just finger tight as well so they can find their natrual sitting postion, then start at the floating end of the screw with the gantry down at that end as close as it can go (with-out falling off the rails), tighten the fixings for the ball screw mount at the floating end and then run the gantry up to the fixed end and do the same, creep up on perfect alignment and the ball screw should spin effortlessly as you move the gantry, I've got my X axis (gantry axis) so close doing it this way that i can push the whole z axis assembly from one side to the other with one finger and think that's the standard to aim for on the other axis's.

You can fine-fine tune each with a dial gauge later ;-).

Quote:

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Originally Posted by Lee Roberts

Sounds and looks about right to me, did you get the rails and bearings from fred @ BST?

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Lee, that's really useful advice, thanks a lot, I'll try to follow it. Yes, all the linear motion stuff is from BST.

Quote:

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Originally Posted by bluesking

Lee, that's really useful advice, thanks a lot, I'll try to follow it. Yes, all the linear motion stuff is from BST.

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Well Fred's kit is the real deal so you don't need to worry about it being fake Hiwin linear rails and bearings, the fake stuff doesn't move as smoothly as genuine Hiwin dose, Hiwin is usually quieter as well.

Don't forget to clean them and give a few drops of oil, once everything is setup and running great you can start using Lithium 2 lubricating grease, this lasts longer.

Quote:

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Originally Posted by Lee Roberts

Well Fred's kit is the real deal so you don't need to worry about it being fake Hiwin linear rails and bearings, the fake stuff doesn't move as smoothly as genuine Hiwin dose, Hiwin is usually quieter as well.

Don't forget to clean them and give a few drops of oil, once everything is setup and running great you can start using Lithium 2 lubricating grease, this lasts longer.

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Thanks Lee. I had a go at aligning everything tonight. Definitely improved. Shimming made a difference but still something a little sticky at the extremes. I then tried relaxing all the various attachment points for the ballscrew but this didn't make much difference. In the end I relaxed all of the big 12mm screws holding the 3 main extrusions. This made a significant difference but if I tighten them all up as tight as I can there is still some binding. In the end I tightened them quite gently and this reduced the binding at the extremes to very low levels and the overall frame still seems very rigid. I'm still concerned its not exactly perfect!

I don't really understand what you mean by moving the mechanism with one finger. Certainly pushing the gantry, it doesn't move, there is enough friction to stop any linear force from being converted to rotational motion. For the vast majority of the travel I can just about turn the pulley with one finger - is this what I should be looking for?

I do have a dial calliper and stand but very few places to attach it and not really enough skill to use it. I think I'm going to have to just move on and hope - without any experience it is hard to know if I'm facing real problems or just being picky!

Hi bluesking
When I built mine (see here) It moved by it self once I had pushed gently.The ballscrew was NOT connected for this test so that you can detect any binding in the bearings. However I am using SBR bearings on a supported round rail. These are more tolerant of misalignment than the bearings you are using. With the bearings you are using for the gantry, accurate alignment is a must, I'm afraid, but they are the best you can buy!

Quote:

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Originally Posted by MikeyC38

Hi bluesking
When I built mine (see here) It moved by it self once I had pushed gently.The ballscrew was NOT connected for this test so that you can detect any binding in the bearings. However I am using SBR bearings on a supported round rail. These are more tolerant of misalignment than the bearings you are using. With the bearings you are using for the gantry, accurate alignment is a must, I'm afraid, but they are the best you can buy!

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Thanks Mikey,
Thing is, even just running a single hiwin hgr 20 carriage along a single rail (hence no opportunity for misalignment), you give it a little push and it moves, but as soon as you stop applying force it stops - no momentum retained. I think this is due to the relatively high pre-load on the the HGR carriages - they just behave that way. Anyway, with no ballscrew connected I think things behave well overall (see my video above). Connecting the ballscrew introduced the problems - though these have been much reduced now - I just don't know what I am aiming for!

I'll agree 100% about the HGR20's being a little sticky, but I'd rather they were that way and had no play, than "free and easy" and wobbling all over the place. If you can turn the ball screw end shafts smoothly between finger and thumb then I guess it should be OK - after all, a decent stepper should be giving a good few hundred Ncm torque.

Quote:

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Originally Posted by Voicecoil

I'll agree 100% about the HGR20's being a little sticky, but I'd rather they were that way and had no play, than "free and easy" and wobbling all over the place. If you can turn the ball screw end shafts smoothly between finger and thumb then I guess it should be OK - after all, a decent stepper should be giving a good few hundred Ncm torque.

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Thanks for confirming my thoughts about the HGR20s. I think I've got the rails sorted, its the ballscrew causing issues I think. I have got it to a much improved state, but I can't quite "turn the ball screw end shafts smoothly between finger and thumb". Whilst the resistance along the entire travel is now pretty much uniform, there is a little patchiness to the motion - there are occasional slight sticking points which require a bit more force than just two fingers can apply. I mainly test it using the belt to move the ball screw and it all operates ok in motion though from a standing start it can be a little "sticky".

It may well be fine with the reasonably overpowered servos I will be using. I'm going to leave it as is and proceed with the other axes so I can compare the motions between each axis.

If its still a problem I can think of only 2 ways forward:
- widen some of the mounting holes so the major extrusions have a little more "wiggle room" so I have broader alignment range
- buy a new ballscrew - I worry I may have subtly bent this one during my initial tests and now it will bind whatever I do...

Quote:

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there is a little patchiness to the motion - there are occasional slight sticking points which require a bit more force than just two fingers can apply

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BTW, did you check the ballscrew for smoothness throughout its' length before mounting it?? As I mentioned in my thread here: http://www.mycncuk.com/threads/12524-gritty-ballscrews , although Fred tries hard to please, his engineers don't always seem to adhere to the old saying "cleanliness is Godliness" when it comes to machining ballscrews. Even the replacement parts he sent me needed a clean, strip down, flush through and re-grease before they were acceptably smooth. Try running (twisting) the sticky portions through a piece of clean tissue and then examine under magnification to see if there's any small flakes of swarf.

Quote:

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Originally Posted by Voicecoil

BTW, did you check the ballscrew for smoothness throughout its' length before mounting it?? As I mentioned in my thread here: http://www.mycncuk.com/threads/12524-gritty-ballscrews , although Fred tries hard to please, his engineers don't always seem to adhere to the old saying "cleanliness is Godliness" when it comes to machining ballscrews. Even the replacement parts he sent me needed a clean, strip down, flush through and re-grease before they were acceptably smooth. Try running (twisting) the sticky portions through a piece of clean tissue and then examine under magnification to see if there's any small flakes of swarf.

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I think you may be right. I need to dismantle much of my machine anyway so best get to cleaning the ballscrews!

In my hurry I didn't attach the nipples to my HIWIN carriages so this is probably a good opportunity to do that as well. I see you have made a post about these nipples: Do you know if the following are a good way to go for greasing the carriages? Are they also suitable for greasing ballscrews/nuts?

https://www.toolstation.com/laser-grease-gun/p29224
https://www.toolstation.com/lithium-grease/p89691

Quote:

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Originally Posted by bluesking

I think you may be right. I need to dismantle much of my machine anyway so best get to cleaning the ballscrews!

In my hurry I didn't attach the nipples to my HIWIN carriages so this is probably a good opportunity to do that as well. I see you have made a post about these nipples: Do you know if the following are a good way to go for greasing the carriages? Are they also suitable for greasing ballscrews/nuts?

https://www.toolstation.com/laser-grease-gun/p29224
https://www.toolstation.com/lithium-grease/p89691

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Thats what I use, and it works on the ballnuts that Fred has sent me. I think the nipples for the HGR20s are the same, but I haven't gotten that far yet. Highly recommend the flexible extension for the gun, and don't try loading the grease gun for the first time in toolstation's car park when you're inside the car. Not a clean experience. Worth watching a youtube video or two on loading, attaching, and de-attaching grease guns if you've never had the pleasure to using them before, there are a couple of nuances.

This is the flexible bit I'm talking about:
https://www.toolstation.com/laser-gr...nnector/p33147

Quote:

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Originally Posted by AndyUK

Thats what I use, and it works on the ballnuts that Fred has sent me. I think the nipples for the HGR20s are the same, but I haven't gotten that far yet. Highly recommend the flexible extension for the gun, and don't try loading the grease gun for the first time in toolstation's car park when you're inside the car. Not a clean experience. Worth watching a youtube video or two on loading, attaching, and de-attaching grease guns if you've never had the pleasure to using them before, there are a couple of nuances.

This is the flexible bit I'm talking about:
https://www.toolstation.com/laser-gr...nnector/p33147

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Thanks Andy,
Just got back from toolstation with the gun, but didn't get the flexible hose, looks like I'll be going back!

One question, how do you grease your ballscrews? There is no nipple I can see...

Quote:

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Originally Posted by bluesking

One question, how do you grease your ballscrews? There is no nipple I can see...

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There isn't a nipple on the screw itself. The bits that move are the bearings and the ballnut - the rest just needs a slight surface coating to protect the metal. The bearings are sealed, so its just the ballnut that needs the gun.

I over-greased the ballnut and then ran it up and down the screw to smeer the grease all around. The other way would be to smeer some grease with a finger all the way along, then run the ballnut up and down a few times.

Make a new video so we can see and hear whats happening now you've tweaked it some more!

I was about to say the same as Voicecoil re making sure everything is clean, I always suggest people do that with the nut's because I don't think I've seen one yet that didn't have crap inside from the factory.

It can be tricky and the balls will fall out if you remove the nut from the screw, that's OK because your going to flush it all out and clean everything anyway but it can be a little time consuming reloading all the balls back in, to do this pack the nut with some grease first, enough to hold them in place not literally "packed".

The trick is getting the nut back on the screw without dislodging any of the balls, its very doable but equally easy to try and go to fast and knock the balls back out when your trying to thread the nut back on.

While/if your there, count how many balls you've got out altogether, its common for some to be missing from the 17 per track on a 1605 ball nut (even from BST).

Have another read of this thread re nipples and so on, you can include the ball nut: http://www.mycncuk.com/threads/12835

Also (for everyone), if you read the document from Hiwin on the their Linear Guideways it has quite allot of info, Page 27 (2-1-7 Lubrication), shows you info on the grease nipple and ALSO the additional mounting locations built into the blocks so you can move the nipple if you want to: https://www.hiwin.com/pdf/linear_guideways.pdf

Quote:

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Originally Posted by bluesking

I don't really understand what you mean by moving the mechanism with one finger. Certainly pushing the gantry, it doesn't move, there is enough friction to stop any linear force from being converted to rotational motion. For the vast majority of the travel I can just about turn the pulley with one finger - is this what I should be looking for?

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I mean I can move my whole Z axis from the left to the right of the X axis (gantry) really easily, I can push it with my finger and the ball screw on the X axis just spin's like its nothing, its actually amazing that I got it so perfect pre dial indicator to check anything. I think I just got well lucky but it wasn't first time fitting, i went back and forth (literally) for hours loosening the rails and the ball nut and screw fixings until everything just moved perfectly by hand, I used the same method I gave above to do this and at some point you have to say OK that's as good as it gets and start tightening things up as permanent.

I'm really close with the Y axis (bed) but I think its just off a little bit still, like you I still have "sticky points" along the travel, if I push my gantry it is much harder to push along then the X axis for sure but dose go with enough force to get the screw spinning. Still building my machine but i'm going over at the weekend to have another play, I'll get my mate to video me pushing mine about so you can see, maybe the others with more experience can then give their thoughts.

From what I understand, anything less than dial indicator prefect just means uneven ware and tare on the parts and that on a hobby machine used 2-3 times a week, this ware would be negligible because it would take forever to accumulate enough to effect anything a hobbyist would be looking to achieve - Somewhat subjective I know.

Lee, you are a legend, thanks for all the detailed and helpful responses. I will be sure to post a vid showing some of the machine motion once its rebuilt.

Machine is currently in pieces because today I have disassembled all 3 of my ball screws. Cleaned every part with naphtha and relubed with lithium grease (thanks AndyUK - I just smeared about 3cm^3 on the screw and ran the nut over it, repeating until none was left collecting on the rubber seals at the ends of the nut).

Counted the ball bearings - exactly 51 in each ball screw and I managed to get exactly 17 back into each track when reassembling. I reassembled them dry, using the ballscrew itself to guide the balls into their channels. Found this easy and I think its less messy than using grease to stick everything in place. I used the method in this vid to repack the balls https://www.youtube.com/watch?v=GXdt5M8ZeoE

All I have to show for my work is the following vid. Shows all the nasty stuff left floating in the naphtha after cleaning each ballscrew:
https://streamable.com/up3n4

End result certainly feels subjectively smoother - will only know for sure once the machine is rebuilt. One thing I've noticed is that after cleaning the nuts do not spin as easily - though they do spin much more smoothly. I put this down to increased viscosity of the lithium grease compared to what was in there from the factory.

Quote:

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Originally Posted by bluesking

Lee, you are a legend, thanks for all the detailed and helpful responses. I will be sure to post a vid showing some of the machine motion once its rebuilt.

Machine is currently in pieces because today I have disassembled all 3 of my ball screws. Cleaned every part with naphtha and relubed with lithium grease (thanks AndyUK - I just smeared about 3cm^3 on the screw and ran the nut over it, repeating until none was left collecting on the rubber seals at the ends of the nut).

Counted the ball bearings - exactly 51 in each ball screw and I managed to get exactly 17 back into each track when reassembling. I reassembled them dry, using the ballscrew itself to guide the balls into their channels. Found this easy and I think its less messy than using grease to stick everything in place. I used the method in this vid to repack the balls https://www.youtube.com/watch?v=GXdt5M8ZeoE

All I have to show for my work is the following vid. Shows all the nasty stuff left floating in the naphtha after cleaning each ballscrew:
https://streamable.com/up3n4

End result certainly feels subjectively smoother - will only know for sure once the machine is rebuilt. One thing I've noticed is that after cleaning the nuts do not spin as easily - though they do spin much more smoothly. I put this down to increased viscosity of the lithium grease compared to what was in there from the factory.

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No problem, great that's good to know about the ball count if you ever lose any let me know I can send you some the right size.

Yea that's how I started doing them years ago (dry+screw) I've rebuilt quite a few for people now and found it a little obstructive using the screw (length/weight) so I just use a tube of ali to the right OD with a hose spring clip attached to one side, I slide this in just after I've got the first track filled, it depends on the job though as some people ask for the nut to be on the screw when i send it back because they don't want to risk it again. Both ways though I still use a little grease as a "retainer", they used to ship the nuts with the tube and a clip on both ends but they seem to be a plastic tube with cable tie now.

13mm (1/2") Aluminium Alloy Tube

Best served with some of these: Double Wire Spring Clip

Equipped with my newly cleaned ballscrews I made substantial progress today.

First I reworked all of the Ali plates. I widened a bunch of holes. The M12 bolts had 13mm holes, now 14mm. The M5 bolts had 5.5mm holes, now 6.5mm. The idea is to allow more wiggle room so I have wider alignment range on all the mechanics. This worked a treat: I no longer need to use any shims, careful and methodical alignment allowed me to find good alignment without messing about with coke cans and tin foil!

I then bevelled most of the holes in the Ali Plate. I was worried that the burrs around the holes were messing with precise mating of all the pieces:
Attachment 25896
Attachment 25897

Whilst I was at it I bevelled the edges of all the plates at 45deg on my spindle sander. I was getting tired of the sharp edges opening up my skin and getting blood all over the machine!
Attachment 25898

Rebuilt the Y axis (major axis) and aligned the hiwin rails. Here is a vid of the gantry running on just the rails. About the same as before, maybe a bit better, seems fine to me.
https://streamable.com/22i2r

I then connected and aligned the Y axis ballscrew. Got the resistance completely even along its entire travel, all the way to the extremes. It is a HUGE improvement due to the cleaned ballscrews and the improved alignment. Here is me turning the ballscrew and moving the whole gantry with one finger, it is this way along the whole length!
https://streamable.com/n26nm

I can even push the gantry and the Y ballscrew spins accordingly. Unlike Lee, I simply cannot do this with one finger, need both arms and a sure footing! Still, this was completely impossible before:
https://streamable.com/sbztv

Here are some vids showing the same behaviour on the X axis, once again over the entire length of travel. Even easier to move (I think mainly because it is lighter, rather than due to any better alignment).
https://streamable.com/yzbnr
https://streamable.com/73cc5

In summary, everything is hugely better. I now believe this machine is set up absolutely adequately for my purposes, belts encounter almost no resistance when turning, my servos should be able to throw this beast around no problems. In fact, it is much better than my little desktop CNC that I have been using to cut guitar fretboards.

I do not think I can possibly improve on this setup. I love the idea that Lee can move his Z-axis side to side with one finger, but that seems impossible to me on my machine - even disconnecting the ballscrews and one hiwin rail (i.e. moving on just a single rail) I cannot get this performance with the rails I have!

I'm very impressed and grateful for everyones help.

Here is a current snapshot of the machine, ready for assembly of the Z axis:
Attachment 25901

Hi blueskin
Looks a treat and a nice build. It is worth investing in specialised shim stock, because it allows you to shim precisely. see here
Also get you axis nomenclature clear. If you assume that the bottom left corner of your machine (looking top view) is 0,0 then the Y axis is the axis between the gantry sides and the X axis is the longest axis. Z zero is the topmost point of travel on the z axis.

Now start to work out where cable chain will run. This is something I did'nt do until I was at the same stage as yourself. I had to lash something up but luckily the design had space for aluminium channel to be fitted to support the chains

Finally for your spindle mounting, also try and design some means of adjusting for tramming the spindle. It will make your life easier. At the moment I'm using shims and it is tedious!

Keep going!

Michael

Quote:

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Originally Posted by MikeyC38

Also get you axis nomenclature clear. If you assume that the bottom left corner of your machine (looking top view) is 0,0 then the Y axis is the axis between the gantry sides and the X axis is the longest axis. Z zero is the topmost point of travel on the z axis.l

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Surely if you're standing at the front of the machine looking down, (i.e. 0,0 is front LH corner) then this is the opposite to how you'd have X and Y on a normal graph?? I'm with Bluesking on this one :-) Not that it really matters, he's made it perfectly clear what he's doing.

Most 2D/2.5D drawing packages use the normal mathematical convention that the X axis is L -> R as you look at the paper, the Y axis is at right angles to it. How you orient your paper or machine is irrelevant. My machine is in portrait mode and it just makes it easier to visualise if it is the same as the drawing. My Z zero is at the top of the workpiece, but my Z homes to the top of travel. X and Y homes to Left and Nearest me respectively. I just find it less confusing this way and therefore mistakes are less easily made.

Hi Guys

Sorry everyone, this is what I meant - standard landscape graph mode.But I of course it does'nt matter which way you do it providing you know what to expect...

Attachment 25906

Wow, what a controversial issue my axis labelling has turned out to be! I'm happy with my system, long axis Y, short axis X, corresponding to a portrait graph as you guys call it.

Z axis build today.

aligned the hiwin carriages first of all as I can't get to them after anything else is assmebled
Attachment 25917

then finalised the fit of the hiwin rails
Attachment 25918

then ballscrew aligned and attached the spindle once I was happy there was no binding
Attachment 25922

entire travel moves smoothly, it is easily pushed down by hand, not so much up for obvious reasons. My biggest concern here was that the Z axis would fall under its own weight. Well, I got lucky, there is just enough friction to keep the axis from falling down so I won't need to bother with a brake. Here is a video of how it behaves as it is - this is without the belts/servo connected, so after connection there will be even less chance of it falling after powering down:

https://streamable.com/z05b9

bolted on the reinforcement struts to the base to improve rigidity - seems to make a noticeable improvement
Attachment 25921

quick measure up of the drag chain - I'll cut some Ali Plate to support this - one end will be attached to the gantry, the other directly to the table - not pretty but I think it'll work just fine - I liked Wal's build that he had his chain under the table, but I have my reinforcement struts there and prefer rigidity over neatness!
Attachment 25924
Attachment 25923

finally, a quick test fit of the servos to see if there is enough pulley adjustment range (broadly planned that there should be throughout the build!) and to check whether the belts I have are of suitable length. I need to buy a slightly longer Z axis belt, you can see that the servo doesn't quite mount properly as is - I had to shorten the support extrusion for it during the build as I couldn't be arsed to cut an indent to go around the ballscrew bolts.
Attachment 25925
Attachment 25926
Attachment 25927
Attachment 25928

Quote:

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Originally Posted by bluesking

I can even push the gantry and the Y ball screw spins accordingly. Unlike Lee, I simply cannot do this with one finger, need both arms and a sure footing!

I love the idea that Lee can move his Z-axis side to side with one finger, but that seems impossible to me on my machine - even disconnecting the ball screws and one hi-win rail (i.e. moving on just a single rail) I cannot get this performance with the rails I have!]

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Just to clarify mate, I can only push my Z axis across the X (gantry) left to right with hardly any resistance, watching your video of you moving the gantry up and down the Y axis (bed), I would say we are very close in terms of effort required to make it move and the screw to spin.

You should note I'm using supported round rail, I thought I mentioned that in my other post, if I didn't sorry about that. Your rails are far superior to the ones I've used on this machine, overall I think your now on to a winner and agree you should move onto the next parts.

What pitch screws have you used on your longer axis's ? I've used 1610 ball screws on both X and Y, I think that may also be why its a bit easier for me to make things move. The rails on this machine will be making the most difference.

Well done, keep going looking forward to seeing you push the Start button :thumsup:

Quote:

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Originally Posted by Lee Roberts

What pitch screws have you used on your longer axis's ? I've used 1610 ball screws on both X and Y, I think that may also be why its a bit easier for me to make things move. The rails on this machine will be making the most difference.

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Nice one Lee,
I'm using 1605 throughout and various gear ratios. As I'm using servos my main goal is to slow everything down enough rather than to speed it up like most stepper guys are doing.

Between that and the round rails you are using I'm feeling confident that I've managed to squeeze out all the performance I'm likely to get from my machine. Thanks again, you've given me really helpful advice about what I am aiming for and now I can move on with confidence, its a good feeling!

I'll mainly be focusing on the electronics and software from now on.

Hi bluesking
Any progress lately?
What gear ratios did you use for x,y and z axis?I assume 2:1 on x,y and 3:1 on z?
Thanks

Quote:

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Originally Posted by Scustom

Hi bluesking
Any progress lately?
What gear ratios did you use for x,y and z axis?I assume 2:1 on x,y and 3:1 on z?
Thanks

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Hi,
I've almost finished the machine. Just about to post a progress update. Gearing is 2:1 on XY and 4:1 on Z.

Been a little while since I last posted but progress has been made. Almost finished and very pleased - things all worked pretty much to plan, even the electronics and software.

1) Made a simple 400x400mm MDF enclosure for the control box. 3D printed some connection panels so I can change the interface in future if necessary. Bit of spare clear acrylic for the top.
Attachment 26035Attachment 26031Attachment 26032Attachment 26033Attachment 26034

2) Spent about 50 hours of bench time to wire the control box. Surprised at how long this took - thought it would be simpler but I was testing individual functions as I went to make sure it all integrated OK.
Attachment 26028 Attachment 26029Attachment 26030

3) A lot of the bench time was spent preparing cables and connectors. Here's all of the prepared cable ready to go into the workshop:
Attachment 26036

4) Back in the workshop, attaching the drag chain to some 3d printed mounts:
Attachment 26037Attachment 26038

5) Attaching various homing and limit switches, once again on 3d printed mounts. Laying cable in the drag chain.
Attachment 26039Attachment 26040Attachment 26041

6) Here is the basically complete machine!
Attachment 26042

Heres a quick vid of the machine doing some initial rapids. Spindle yet to go on, but I'm getting 9000mm/min on the X & Y axes before servos stall. Thats setup for a theoretical precision of around 1/1000th of a mm with the encoders I have and running the UC400ETH at 200kHz. Obviously that precision is pretty goofy, I was just erring on the side of caution - still there is plenty reason to think I can squeeze a bit more speed and torque from this setup after a bit of experimentation and tuning.

https://streamable.com/orect

There is still spindle mounting and some tuning to do for precise axis scaling and servo PID controller tuning. After that I'll be moving on to spoil board, jigs and dust extraction.

I love the control box! It's so much easier to fix everything to MDF than mild steel or aluminium and makes future changes a lot easier. It also allows you to concentrate the funds where they make a difference rather than just spending money on something that looks good. I've never quite seen the point of making one-off home constructed machines mimic professional, mass produced factory built versions. The priorities are completely different.
The only possible problem is electrical noise, a discussion going on elsewhere on the forum. This is something you can address with additional screening and appropriately placed capacitors if and when it shows up during testing.

Kit

Quote:

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Originally Posted by Kitwn

I love the control box! It's so much easier to fix everything to MDF than mild steel or aluminium and makes future changes a lot easier. It also allows you to concentrate the funds where they make a difference rather than just spending money on something that looks good. I've never quite seen the point of making one-off home constructed machines mimic professional, mass produced factory built versions. The priorities are completely different.
The only possible problem is electrical noise, a discussion going on elsewhere on the forum. This is something you can address with additional screening and appropriately placed capacitors if and when it shows up during testing.

Kit

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Thanks Kit. I couldn't care less what it looks like, as long as it functions well!

Everything seems to be ok so far - no interference yet, but it is very early days. I have implemented a single point star ground and shielded cable throughout, even on the limit switches - I am more worried about interference on all that cable than I am into the control box. Also, almost every EMI noise source in the room is actually sitting in that box already, so I'm not really convinced a metal enclosure will help anything for me! We shall see!

Also, I've been meticulous in avoiding ground loops. Despite this, I did knowingly introduce one ground loop into the system - this loop goes between the control box and the VFD, and back through the mains circuit. I wanted to avoid this, but I also wanted to have a Z probe which worked without a crocodile clip. There were a few options I could see:

1) lift the mains earth in the VFD - this would probably be the best way but the VFD is very high power and I was worried that earthing it through the signal cable shield could potentially dump a huge amount of current into the control box if the VFD failed. Then I would have to replace not only the VFD, but also debug and fix the whole control box!

2) rely on a common earth between the control box and VFD - earth both to the mains, and assume that is adequate to close the loop on my Z probe. This would certainly have worked in my workshop - because I plug both devices into the same mains circuit so they share a common earth. However, if I ever moved the machine somewhere else and the two devices no longer shared a common earth, my Z probe would fail! This seemed like a really unpleasant easter-egg for future me (or another owner) to have to deal with!

3) Knowingly introduce a ground loop. This may or may not cause an interference issue - but is safest option. No issues noted so far!

Quote:

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Originally Posted by bluesking

I also wanted to have a Z probe which worked without a crocodile clip.

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My tool tip has earth continuity, so this type of touch plate works for me.
Attachment 26051
Even though your spindle body may be earthed, that may not continue to the tool if you have ceramic bearings, so a switch type would have to be used.

Have you metered the resistance between collet and spindle body ?

As I've just mentione elswhere, an RCD in your mains supply offers no protection against shocks from the output of your VFD. Don't take risks with the safety earthing of your spindle.

Quote:

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Originally Posted by cropwell

My tool tip has earth continuity, so this type of touch plate works for me.
Attachment 26051
Have you metered the resistance between collet and spindle body ?

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I've metered between collet all the way to the BOB, thats what made me think it would work. I then tested the z probe (same idea as the one in your pic), thats how I know it works!

Weirdly my spindle is quoted as having ceramic bearings though so not quite sure why it does work. But I'm happy so far.

Quote:

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Originally Posted by Kitwn

Don't take risks with the safety earthing of your spindle.

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I haven't taken any risks: the spindle is earthed. Thats the reason why I had to introduce a ground loop to make my z probe work how I wanted and still be safe - at the cost of some potential interference...

It's a basic catch 22 - and the reason why many valve amps have a ground lift switch. Always seems a bit dangerous to me to leave it in the hands of the guitarist to decide what is safe! But it's there when you use multiple amps and you know they are all on the same mains circuit yet the ground loop is causing noise to get in the system.

We should probaly start a new thread to start talking about multiple amps, Brian May, whether Russian ECC83s are better than the Chinese, using CNC machines to build guitars.....................

Kit