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Iwant1
09-07-2012, 06:42 PM
Finally I get the courage to join the forum and start making threads after 2 yeas of first stumbling onto it. When I first got the craze to build my own router, I got so wrapped around the idea I was going to build this incredible machine, which most of my friends don't even know what it is, I started ordering parts without any plans drawn.

So my list of components I have are,
3 sy60sth88-3008bf motors
3 pm752 drivers
breakout board
20mm supported round rail for the x and y axis at 1200mm and 800mm respectively
15mm profiled rail and slides for the z axis at 550mm long
4 1605 ballscrews with nuts and mounts
a 50v minebea psu from ebay, but will eventually build my own.

All this was bought 2 years ago from Zapp and Chai, so now I have to reverse engineer my router to fit these items. I have made some detailed drawings of how I would like my machine to look, but would like some input on a few things.

62926293629462956296629762986300


Ok, as you can see I've been trawling all the build logs and tried to incorporate what I think would be best for my build.

The gantry sides and whole z axis will be made from Ecocast 20mm x 200mm wide ali plate.
The rear plate to the gantry will be 10mm thick which I hope will be sufficient.
The Z axis will have rails on the front plate and slides in the back plate.
All axis will be connected with screws using pulleys and currently at a 1:1 ratio just to get the machine moving.
The frame, which is very similar to Jonathan's, will be made from 50mm steel box section and 50mm x 100mm for the top supporting rail. I'm planing for some adjustability so will be welding the whole bottom section but will use plates and bolts for the top RHS on to which the 20mm suported x axis rails will be resting on. I won't be using any welding on this top section to avoid warping. The actual cutting bed will be height adjustable too.

A few questions I have will be described with illustrations.


63016302

The Z axis I have uses 15mm NSK profiled rails and slides. The problem here is that the total height from the bottom of the rail to the top of the slide is 16mm. The ballscrew mounts which is in between the 2 plates is 43mm thick, so I have to add 30mm of material in between the plates. I would like to know is it best to have this extra spacer added to the rails side, or the slides side. Both variations are shown in the top drawings.

Next:
6303

This type of x axis ball nut mount looks the easiest and neatest from my side, but is it strong enough for pushing the whole gantry. It is made using 20mm plate and has 2 functions, as a nut mount and also to hole the gantry side square to the bearing plate.

Lastly:
6304

I will be using 50mm ali boxing to support the y axis rails onto, but I'm unsure if the wall thickness is enough to drill, tap and hold screws from the top, and also from the back for the 10mm plate. This box section will be held onto the gantry side plates using registering blocks screwed onto the gantry sides and then a threaded rod right the way through the ali box section from gantry side to gantry side. As I've drawn above I could if its very necessary, make a strip of 10mm ali plate into a nut plate, if I can call it that. It will have holes drilled and tapped in the exact position to match the holes on the supported round rails. This way I could make the holes in the ali box section slightly larger and have some adjustability to get the rails aligned with each other.

Thanks for being patient and reading this long boring thread.

Adil

Jonathan
09-07-2012, 08:49 PM
Wow, at last someone has bothered to read build logs and think about it before posting :thumsup:


The frame, which is very similar to Jonathan's, will be made from 50mm steel box section and 50mm x 100mm for the top supporting rail.

What wall thickness? If you stick with 3mm, maybe 3.6mm, it's much easier to weld. Just for reference mine is mainly 60x60x3, 100x60x3.6 (x-rails) and a small amount of 50x50x3mm. If you add some pieces in the corners of the frame at 45 it will significantly increase the rigidity of the frame. I never got round to adding them on mine, although they are on the original drawing. It's the sort of thing you can add when the rest is welded to use up any left over box section.

With regards to the Z-axis rail mounting - neither of those methods is ideal. If you had to pick one I'd put the rails on blocks as that would help stop the Z-axis plate bending, but they would have to be machined accurately - not just any old flat bar. However I'd consider that a last resort since it is important, particularly withnot having profile rails on Y, to get the cutter as close to the Y-axis bearings, when measured parallel to X (the 'overhang'), as you can. Since the Y-axis bearing blocks have a finite stiffness, when a force is applied to the cutter parallel to Y the tool will deflect and this deflection will be proportional to the aforementioned distance, therefore you should minimise it as it will directly increase rigidity.
As you're using standard BK/BF bearing blocks this presents a problem, since clearly they will collide with the Z-axis plate if the spacing is reduced. Options:
1) Make cutouts in both of the 20mm plates which the bearing and ballnut blocks 'sink' into, to effectively reduce their centre height.
2) Use a longer ballscrew and mount it to the Z-axis plate (like on mine), that way the bearing blocks wont be over the other plate. Still need cutout for ballnut.
3) Make lower profile bearing/ballnut mounts, then less deep cutouts are required.

Problem is all of these options are easiest with a milling machine, or require outsourcing but to me it would definitely be worth it.

The ballnut mount looks weak to me since it's so long. The easiest solution is to move the ballscrews up, but no doubt you didn't do that because the ballscrews aren't long enough to mount at the most convenient point. You could make the ballnut mount stronger, but even then there's quite a distance (measured vertically) between the X-ballnut and rail, which for the same reason as for Y/Z it's best to minimise. I would be inclined to raise the ballscrew so it is in line with the X-axis rails and add an aluminium plate to support the non driven end, preferably linking on to the far vertical support. The strength of the non-driven end bearing mount isn't critical as it's (roughly) only there to stop the screw whipping, so there's not much force on it.

I bolted my Y-axis rails to 80x80x3mm aluminium box section. The bolts are strong enough, but in my case the box section is a weak point as there is only one. You can get the necessary adjustment on the rails for them to run smoothly by drilling the holes in the rails slightly bigger to give the bolts a bit of clearance. It would be nice to use a greater wall thickness just from a strength point of view.

Iwant1
09-07-2012, 11:02 PM
Thanks for the suggestions Jonathan. I've redrawn the x axis screw so it is as close to the supported rail as possible. This has bought the ball nut mount up by 60cm.

63056306

Regards the z axis. I had no idea I had to consider the height of profiled slides when I bought them of eBay. Lesson learnt, and if as you say I machine about 10mm grove out of both z axis plates, I still need 10mm. Say I grove out 10mm from the front plate, then sink the ball nut even more, up to a point where the screw shaft just clears the front plate, then I might just get away with that last ten. I'll draw this later to see if it is feasible.

I would definitely consider outsourcing to one of you guys to machine these plates as it will make a much sleeker z axis and also bring the spindle cutting point to within the x axis bearing blocks.

Jonathan
09-07-2012, 11:27 PM
You should consider incorporating adjustment of one of the X-axis ballnut mounts to gain better alignment of the ballscrew. Currently you're relying on the accuracy of the frame, rail position and all sorts for the distance between the rail and the ballscrew to remain constant. In reality the tolerances on all these build up, so it's easiest to make sure at least one of the bearing mounts (clearly the non-driven end is easiest) position is adjustable in the Y-Z plane to ensure you can align it accurately. If not you risk the mechanism binding towards each end which will put a large force on the ballscrew/nut...

On my Z-axis I currently have 520mm long 20mm NSK rails, so the additional height of those helped. If you go up to 25mm plate for one of the plates on the Z-axis that might help to get the required pocket depth without sacrificing strength. Using that strategy I recently made a Z-axis using 25mm profile rails with only 2mm clearance between the plates. Also if you get the Z-axis parts machined there's not really any need to use the more expensive tooling plate - I would mill the surfaces for the rails and blocks to get them flat and in the same plane.

Iwant1
09-07-2012, 11:51 PM
I was just thinking about that adjustment last night. I was going to slide the gantry to the driven end of the x axis, locate the ball screw bearing block there, then slide the gantry to the non driven end and get the position for that screw bearing block. Suppose great minds think alike lol.

Great advice about getting 25mm plate. Does that mean it would be safe to remove 15mm of material? If I don't need EcoCast then what would be suitable 6082 plate, 5083 plate or 6082 flat bar. Also how accurate does the 10mm plate that goes behind the gantry have to be? sorry for so many questions.

I basically was reading in lots of forums that 15mm profile rails would be plenty strong for all axis, but never thought 20/25mm would be better for filling spaces between z plates.

Originally I was going to make the z axis the way I'v drawn, then use a working machine to mill out what we are discussing for a version 2 machine. Thanks for offering, I will pm you about your pricing once I've re drawn it.

JAZZCNC
10-07-2012, 12:53 AM
Like jonathan it's nice to see someone who's actually done the leg work and payed attention. . 10/10. . Big respect. .:thumsup:

Agree with Jonathan on every thing he's said except not using the Ecocast.! Even thou you will machine the bearing mounts etc unless you surface and make parallel both surfaces your still going to have troubles and in-accurecy. The problem comes from the cheaper plate not being uniform thickness so you can't be sure it's the same thickness (Or flat) all along it's length. This means buying much thicker than needed so it can be surfaced and still have the required thickness to be strong.
I used to do just this but since the Ecocast has been easily available in small qty then I don't bother any more and it cuts out some of the work involved and makes things that bit easier.

To be honest the 20mm plate is still fine regards strength even with the neccesary slots cut, I've made several with 19mm 6082 and slots etc and they are more than strong enough for even the most demanding jobs.! (Within reason) See pics of what you may have seen before just not striped down like these.?
(obviously more thickness will be stronger but not 20mm gets the job done.!!)

The only other point I will mention is the belt setup and the lack of protection from chips etc.!!
You probably know my machine use's this setup and I'm guilty of not covering the belts and while it's never been a problem, other than grabbing my teashirt a few times and trying to eat me, I would still advise you to cover them up before using the machine.! . . .I'm pretty sure the constant pounding from chips etc has or will shorten the belts life so worth doing before using the machine otherwise like me you'll never do it after machines put to work.!!

Anyway great work and can't wait to see it turn into reality. . .:yahoo:

Iwant1
10-07-2012, 07:53 PM
Redrawn the z axis with new 25mm plates for the rear and front. Also included registers for the NSK rails and slides although they are only 1mm. It is a very tight fit and looks much sleeker now at only 64mm depth. I suppose If I had to then I could sink the bk/bf blocks a few mm into the rear plate, just where the blocks go. Its not easy to show but the ball nut's flange head sticks into the front plate by a few mm, which could be a good thing if the hole is machined accurately.

The spindle cutter head has now moved 30mm towards the y axis and now rests between the x axis bearing blocks. Pictures showing the new design and also how far the z extension could be dropped. Its around 250mm, not that I would need that much, but the rails are long so might as well use them. I try to put as many detailed pics up for all novices to see, as this is what I was looking for while doing my research. Hope it helps someone.

Adil

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JAZZCNC
10-07-2012, 09:52 PM
Ermm.!! . . . . Been looking at this thinking don't seem quite right.??? . . . I'm sure it's correct because you've obviously taken lots of time over it but I'll ask anyway just in case.!!

The bearing/rail height seems low.? from the dimensions on the drawing it appears to be about 16mm this is very low even for 15mm profiled rails and surely can't be right.? Do you have the bearings set in pockets.?

Iwant1
10-07-2012, 10:47 PM
Thanks for noticing how small my profiled rails are. I mentioned earlier in the thread I didn't realise that they came in such low profile dimension. I got them for 70 from ebay for two slides and 4 rails as 15mm width and 550mm length. I've attached some pics to show their dimensions with respect to the bk/bf blocks. This is why I'm in a pickle over using 25mm plates for the z axis with 15mm machines out from each.

Do you think I should sell them on and get slightly larger rails.

WandrinAndy
10-07-2012, 11:59 PM
I've attached some pics to show their dimensions with respect to the bk/bf blocks.

As a novice who has never seen any of these components in the flesh so to speak, those dimensioned pics have really helped me and reminded me that I need to get a digital caliper... thanks Iwant1... I'm following your build with interest btw, and want one too!

JAZZCNC
11-07-2012, 12:09 AM
Do you think I should sell them on and get slightly larger rails.

I wouldn't go that far but they certainly are not ideal in the respect they make the pockets deep.!!

There is one thing I'm not to sure about and it's hard to tell from the pics, is that they don't look like the 4 row type bearings.? This makes them that bit less ideal and less able to stand the strain that a Z axis will come under.!! If 2 row type then I think for a Z axis then yes I'd sell them and get 4 row type more suited and making the job a bit easier.!!

Jonathan
11-07-2012, 06:46 PM
Having 4-row profile rails is an advantage over 2-row - twice the balls = twice the surface area in contact with the rails which should get better stiffness, in addition to factors usually mentioned. However 2-row is still in a different league compared to round rails, so unless you can sell them and get better rails for the same price I think there's other places the money would be better spent on. You've got long rails, so use that to your advantage as if you're prepared to sacrifice some travel you can space the bearing blocks out more to reduce the load on each, so long as the piece they are mounted on is stiff. I got 760mm rails for my Z-axis, so if I ever get round to making it I'll keep 400mm travel and have the bearings 360mm between ends, which is slightly extreme but the rails were cheap so why not.





Lost of cnc machine parts are available in the SketchUp marketplace, which you get to from within SketchUp. All the rails, bearings, spindle, motors, ball nuts, etc are available.

The standard part libraries can be helpful, but I tend to draw things myself so I can be confident it is correct. I guess if I used SketchUp I might think differently.

Iwant1
11-07-2012, 08:08 PM
The standard part libraries can be helpful, but I tend to draw things myself so I can be confident it is correct. I guess if I used SketchUp I might think differently.

Very true, many of the parts I used, such as the pulleys, timing belts, ball nuts, linear rails and slides were all over 50 times the size I needed and some not 100% right. I spent loads of time scaling the items as a whole and also separately in each axis so that they match what I had. The problem was in SketchUp, the scale function works as a percentage where as I wanted dimensions, so I had to resize, measure, resize again, measure again..... to fractions of mm's. Next time I'll make them up but then I suppose the same tedious task will be spent with my vernier calipers.

Regards the profiled rails, I think what I paid for these 'mini slides' was very good and I definitely won't be able to get larger ones for this price. I spent ages today trawling eBay for profile rails and carriages and found that I can get Thk and Nsk sets at similar length for around 150 with p&p. Problem is I had to constantly go to their manufacturer websites and check whether they got 2 or 4 rows of balls. Then you find out the balls also have 30,45, and 90 degree configurations. Plus I started mixing models like hgh, hgw, hsr, ssr, sr, lf, lu with the wrong manufactures.

I've seen Zapp is very reasonable with his Hiwin rails and carriages, which work out at 180 for a brand new set, hgh15ca and 500 rails, compared to 150 for similar spec second hand Thk/Nsk on eBay. I don't understand how there can only be 30 difference, are Hiwin a cheap brand compared to Thk and Nsk.

I'm also not sure what preload is suitable for my z axis, as gravity is always going to pull the carriages down especially when all components are connected to it. Does ZO, little preload, mean there is more play between rail and carriages then ZA, medium preload. I have no actual experience what any type of preload feels like, as I only have the second hand ones to go by, which you can blow from one side to the other.

Thanks
Adil

Gary
11-07-2012, 09:53 PM
Personally i would use ZA pre load.
Also a heads up, Hiwin have just raised their prices by about 20%, so expect prices to go up by about 25% with most if not all distributors.

Iwant1
11-07-2012, 10:56 PM
I'm trying to make the build as strong as I can or will ever need. There's no specific need for this router, just for fun. Many of my mates ask, 'what's the first thing you're going to make?' I tell them a plaque saying 'test cut', lol. There's no budget to it, just being wise with money. In the end I'm sure it will cost near 1500 once spindle, plate ali, steel tubing, pulleys and belts are factored in. So far Chai took 550 and Zapp took 250 for the electrics.

Time is always a problem as the family want some dad time in the evenings after work. Suppose I'll have to get my 2 and 4 year olds to help mix up my screws and loose my tools. Funny how all kids love work shops, so many things to play with.

Adil

Jonathan
12-07-2012, 08:21 PM
I spent ages today trawling eBay for profile rails and carriages and found that I can get Thk and Nsk sets at similar length for around 150 with p&p.

I've seen Zapp is very reasonable with his Hiwin rails and carriages, which work out at 180 for a brand new set, hgh15ca and 500 rails, compared to 150 for similar spec second hand Thk/Nsk on eBay. I don't understand how there can only be 30 difference, are Hiwin a cheap brand compared to Thk and Nsk.


That's because you only spent 'today' looking, you have to be patient to get the good deals - bidding not buyitnow. Yes I know, I used to think it's annoying when people say things like that, but it's worked for me in the end.


Does ZO, little preload, mean there is more play between rail and carriages then ZA, medium preload. I have no actual experience what any type of preload feels like, as I only have the second hand ones to go by, which you can blow from one side to the other.

If you can blow the carriage along, or it drops if you hold the rail vertically, then the pre-load is zero (Z0). When there is preload there is no clearence (play) between the rail and carriages, in fact the clearance is negative so it's an interference. This means that when the carriage is slid on to the rail the bearings distort slightly, so there is a force between the bearings and the rail - hence the name preload.

I'd consider having zero, or very low, pre-load a much bigger issue than only two rows of balls. You've got both...

P.S. Noticed there's two discussions going on here, the machine and sketchup - I can separate them if you want?

Iwant1
12-07-2012, 09:11 PM
I'd consider having zero, or very low, pre-load a much bigger issue than only two rows of balls. You've got both...

P.S. Noticed there's two discussions going on here, the machine and sketchup - I can separate them if you want?

Thanks for the insight Jonathan, seems as though I made a bad purchase with my profile rails and have decided to get new ones with medium preload and 4 rows of balls.

I think the sketchup discussions have come to an end, and now will be mostly about my build.

Jonathan
12-07-2012, 09:15 PM
Thanks for the insight Jonathan, seems as though I made a bad purchase with my profile rails and have decided to get new ones with medium preload and 4 rows of balls.

Unless you're desperate to get this done, I hope 'new ones' doesn't mean brand new, not from eBay. You only really need to know which rails you have the day before the Z-axis is actually cut, so unless you're in a massive hurry until that time you can wait for something good on eBay.

Iwant1
17-07-2012, 02:54 PM
Hello all,

I decided to do the version2 upgrade whilst v1 was still in the drawing stage. The main change was to go profile rails on all axis. I also changed the x axis steel rectangle box for 45x90mm ali extrusion as it looks simpler and more accurate to fix the profile rails onto. Same goes for the y axis ali box section except its 45x45mm extrusion. There are two qualities to buy extrusion at, light and heavy. What do most people go with.

Anyways, here are some modified drawings. The first one shows the profile update and the x axis ball nut mount which now allows for adjustment. The middle pic shows how I intend on screwing the bk support block and z motor mount opposite each other. A screw will go from the bk side, through the z rear plate and screw into the motor mount. Hope that is strong enough. Last picture shows how the z plates will be machined to make registers for profile rails and carriages and also allow space for moving parts.

637063716372

Thanks for looking
Adil

Jonathan
17-07-2012, 07:03 PM
Definatly use the 'heavy' extrusion if you can afford it. What profile rails are those and what size...hiwin?


A screw will go from the bk side, through the z rear plate and screw into the motor mount. Hope that is strong enough.
It probably would be strong enough, but it would be good to have a second support for the motor mount, like this one I made earlier:

63736374

Much more important though is you need some method to tension the belt. The easiest way is to instead of having simple holes in the motor mount, make them slots so you can pull the motor/belt tight then tighten the bolts - again like in the one above. This also allows different pulley sizes to be used without changing the belt, which could come in useful.

Edit: Just to add, moved sketchup discussion here (http://www.mycncuk.com/forums/showthread.php/4819-Google-Sketchup-tips-discussion) as requested.

Iwant1
18-07-2012, 05:16 PM
This also allows different pulley sizes to be used without changing the belt, which could come in useful.

Thanks Jonathan, good advice as I will be putting larger pulleys on the motor side. Now I can do it with the same belt.

Yep going for Hiwin, as I can't find any suppliers of new THK or NSK. I'm using 20mm profile rails and the carriages have 4 rows of balls.

I've redrawn the motor mount, but decided not to go with a full plate on the back of the z axis. Just extra weight for the gantry to carry. Can be easily added later if needed.

6386

Jonathan
18-07-2012, 07:16 PM
Yep going for Hiwin, as I can't find any suppliers of new THK or NSK. I'm using 20mm profile rails and the carriages have 4 rows of balls.

15mm rails will be plenty strong enough. The load ratings of 15mm are several times what the machine will require... considering you were happy with round rails just a few days ago, I don't think there's much point using bigger than 15mm since the difference in stiffness between 15mm and 20mm profile rails is tiny compared to the difference between profile rails and round rails. Many much larger industrial machines use 15mm rails.


I've redrawn the motor mount, but decided not to go with a full plate on the back of the z axis. Just extra weight for the gantry to carry. Can be easily added later if needed.

If you do add one it needn't be thick - 10mm would be fine as it's only to stop the joint between the plates that the Y and Z bearing blocks mount on bending.

JAZZCNC
11-08-2012, 11:59 AM
If you do add one it needn't be thick - 10mm would be fine as it's only to stop the joint between the plates that the Y and Z bearing blocks mount on bending.

Know this is a bit late 3 weeks after posting but I've been asked for some input by Adil and was looking over the build again and spotted this comment.!!

Jonathan never have understood why you use this rear plate in the way you do because that rear plate on the back add's very little protection against the joint between Y axis bearing plate and Z axis rear plate bending in the vertical.?
The only forces that apply here are vertical force applied from one side and the overhang distance from the Y axis bearing plate to Z axis rear plate is nothing.? possibly few MM's. So the chances of that joint bending are zilch and if the forces were great enough to bend that then the rest of the frame and gantry are in big trouble and 99% sure something else would be bending/breaking much sooner.
Your design is an open ended box with very little strength in the vertical direction and if enough vertical force is applied at one side the other side will deflect in a similar manner.!

If you want to brace for that movement then plates on the side bolted into both plates would be much better and could be much thinner and still give far better bracing support than those backplates.? This back plate just add's weight and cost IMO for not enough gain and isn't required.!

Jonathan
11-08-2012, 12:22 PM
The back plate is there because otherwise the Y-bearing mount plates are effectively cantilevered, hence in my opinion it's worth having something to reinforce these joints. However I agree that plates on the sides, as you suggest, would offer much better reinforcement, but this would increase the width of the Z-axis and loose some travel on Y, assuming the width of the Z-axis has already minimised. The plate certainly doesn't need to be the same thickness as the other parts, it was just convenient for the one in post #20 since I didn't have much of anything less than 20mm in stock, plus it was an easy way to support the motor mount.

Iwant1: How far are you with the design / build now?

JAZZCNC
11-08-2012, 12:56 PM
The back plate is there because otherwise the Y-bearing mount plates are effectively cantilevered,

Not really much of a cantilever is it at 1 or 2mm and still your not supporting the cantilever but have created double cantilever ~(see-saw with bearings as pivot.!) with no bracing support.!!
Plate thickness doesn't matter could be 50mm or 5mm it's still adding very little vertical bracing support.? Plus it restricts the back side of the gantry so cable chain etc is more difficult to run.? . . . Like say IMO it's heavy, expensive, restrictive and unnecessary. . . Each to there own.!!!

Iwant1
11-08-2012, 12:59 PM
Iwant1: How far are you with the design / build now?

Lots of changes have been made, its an ongoing process with every new thread on here, regarding motor drives and the strongest gantry designs. It gets so confusing. So far, I've managed to sell off my supported round rails and have already bought profiled rails for all axis, got a good price so went with 20mm. I also sold my 50v power supply and got a 2x24v toroidal coil from which I will build my 70v supply. And now I'm thinking about selling my pm752's for the digital am822's. I Know I know, I should have waited before I bought all the wrong components, but at the time, 2010, these were the most popular components. 2 years later I now want an even better machine than I originally thought of.

Anyway, I've also been busy buying all the electronics for my control cabinet. I will be using an old pc case, and filling it with goodies. Around 300 have been spent on all the electric bits, including screened cables, regular 16/0.2 cables, e-stops, limit and homing switches, relay gear, toriodal coil and electronics to rectify it, 12v and 24v psu's, small consumer unit, a selection of plugs and sockets, and the list goes on.

Chai a even sorted me out with a good price for a 2.2kw spindle and vfd, so I went and got some cooling components for this too. Mainly, a water pump with reservoir, double aluminium heat exchanger, 2 120mm pc fans and grills to go with the exchanger. Once these bit arrive, then I will see what size pvc hose I need.

I've been taking pic's of the control cabinet getting made and will post soon.

Adil

WandrinAndy
11-08-2012, 01:14 PM
... I've ....... bought profiled rails for all axis, got a good price so went with 20mm ........ limit and homing switches...

I'm guessing that 20mm is kind of the norm for profile-rails and what Jazz for example has used on the majority of his machine pics?

How much space does one need to allow for limit switches?

Iwant1
11-08-2012, 01:34 PM
How much space does one need to allow for limit switches?

Limit switches are quite small and can be put in most place, on the frame or moving parts like the gantry or z axis. I bought the regular small lever micro switches by Omron not the cheap unbranded ones.

But the homing switches, if you use good ones can be around 50mm x 50mm and 20mm thick, quite large. Again I went for Omron and got a good deal on ebay

JAZZCNC
11-08-2012, 09:54 PM
I'm guessing that 20mm is kind of the norm for profile-rails and what Jazz for example has used on the majority of his machine pics?

Andy I only use 20mm because I get them for almost same money has 15mm so worth the few quid more. . . BUT they are massively over the top and 15mm would be far more than enough so use 15mm if you find some cheap.!

Iwant1
08-09-2012, 04:57 PM
So, while away all the bits and pieces I ordered arrived behind me. It was like Christmas, opening all the parcels. I loved it.

Here are some pictures which I think will help others new cnc builders realise how many parts we need to buy.

The first picture is my control box layout inside of an old pc case. 12v, 24v and 70v psu are here along with drives, safety relays, discharge resister, BOB and fuse box.
6802

My spindle and VFD were from Chai, unfortunately FedEX hit me with a 35 quid bill. I bought an er20 collet set, and full cooling setup consisting of double ali radiator, 2 fans, and a pump with reservoir. Just need to buy hoses and adapters. It was a great feeling powering the spindle for the first time.
6803

This picture shows all the other components like switches, connectors, wiring, e-stops and lever connector blocks. Just forgot to put the cy screened cable in this photo.
6804

Close up of switches and plugs. Andy, here you can see the difference in size between my 3 homing switches and 6 regular micro limit switches. The green push button is for the safety reset and round toggle switch is a limits bypass. The ones in the middle seemed a bit small so I bought larger ones which can be seen on the top left of the pic.
6805

Adil

WandrinAndy
08-09-2012, 08:59 PM
They've certainly helped me now view some terms as images... Thanks Adil.

Iwant1
11-09-2012, 05:43 PM
Thought I'd put up my latest renderings of how I want my router built. I went with the L extrusion gantry design which came out on top in this thread, effect-forces-gantry-cross-sections (http://www.mycncuk.com/forums/diy-machine-building/4925-effect-forces-gantry-cross-sections.html).

A big thanks to Dean for helping me along the way, with which I'm now set on a final design. The drawing mostly concentrates on the gantry and z axis. The x axis is not to scale , just for visual purposes of how the components connect.

So, I've got most of the electronic bits, my profiled rails are on route, and the next thing on my order list is the extrusion. The ali plate order needs some jiggling as I want all small parts to fit on one large sheet, so its easier for machining.

The frame, not pictured here, is still made from welded and bolted steel box section.

The x axis drive will also be upgraded from 1 motor and a long belt, to 2 motors and 2 short belts, as my new drivers have stall detection. Will need to buy the extra motor and driver.

682368226821682068196824

JoeHarris
08-10-2012, 08:51 PM
I remember being advised that it was better to keep the ballscrew as close to the z axis as possible - between two ali extrusions rather than behind one...This is maybe not such an issue with profiled rail? I like how compact this is but does it come at a price?

Jonathan
08-10-2012, 10:59 PM
I remember being advised that it was better to keep the ballscrew as close to the z axis as possible - between two ali extrusions rather than behind one...This is maybe not such an issue with profiled rail?

That's something I mention quite regularly. Profile rails will help to compensate for the ballscrew not being in the optimal location, which is directly between the rails on the gantry, but it will still be better if the ballscrew is closer. Currently the ballnuts seem to be 'out on a limb' which risks the plates they are mounted on bending which is best avoided.

Iwant1
08-10-2012, 11:33 PM
I suppose when you go for the 'L' shape gantry, there isn't many options where the ballscrew can go. This type gantry was deemed stronger than having two separate extrusions top and bottom with the ballscrew inbetween. Some compromises have to be made, and I chose to go with a stronger gantry design.The statement below which JAZZCNC made form the 'effects gantry cross sections' thread reassured me it will be fine.


I've built machines using the green design and please believe me you have nothing to fear the strength is easily over the top for anything but steel or harder.

Yes it places the ball-screw slightly further back than what's considered ideal but again it's nothing and doesn't make any difference to how machine performs. The positive is the screw is away from the firing line and protected.

JoeHarris
08-10-2012, 11:49 PM
Ok, just thought I'd flag it up. With a 20mm plate bolted to the back, two profiles on top of each other must be pretty strong though right?!

JoeHarris
21-10-2012, 10:59 AM
I have now read the thread cited above and the more I look at this L shaped gantry the more I like it! It's more compact, makes connection easier, its stronger laterally and omits the plate. Just one (maybe daft!) question. How do you join the two profiles?!

Iwant1
21-10-2012, 04:49 PM
I've made a quick drawing of how I will be connecting them. A screw goes right through the bottom extrusions and screws up into a T-nut slotted in the top extrusion. The screw head will be sunk into the D slot for my profile rails to sit flat on the extrusion. Hope it clears it up a bit.

7189

JoeHarris
21-10-2012, 07:45 PM
Thanks, I figured that was how. Just wanted to check there wasn't some cunning way I hadn't thought of!

JoeHarris
21-10-2012, 07:46 PM
Think I'm going to be changing my design yet again!!

JoeHarris
22-10-2012, 02:16 PM
Adil / andy / dean got to say cheers to you fellas! started drawing up a gantry based on this L layout and intuition is saying this is soooo much better.

Iwant1
22-10-2012, 06:20 PM
You're welcome buddy, I'm also at a stage where I'm very pleased with my design, finally stopped stressing over it and started to get it built.

JoeHarris
24-10-2012, 10:12 PM
One more question if I may - what profile brand are you planning on using?

Iwant1
24-10-2012, 10:36 PM
I'll be buying from KJN KJN - Suppliers or Aluminium Profile and Accessories (http://aluminium-profile.co.uk/) since they do a 45x90 profile unlike Value Frame whose closest is 40x80 profile. I went with bigger is better, also from reviews I've seen on here about their good service and accurate cuts, I'm sold.

Don't for get to order all the extra connecting elements like T nuts and screws when you place the order with your chosen supplier. Also if you go with profile rails rather than supported rails you need to check the maximum socket head screw that will fit in the rail pocket, as you will have to get appropriate T nuts. For the profile rails I have, I found an M6 thread will fit but its head is fractionally too big, so had to use M5. For connecting ali extrusion profile with other I'll be using M6 Screws and nuts.

Hope it helps, Adil

WandrinAndy
29-10-2012, 04:15 PM
A couple of quick queries please Adil...

Does the fit of the T-Nuts in the Slots allow for a wee bit of sideways adjustment, or can you achieve this by using the M5 socket-screws in your rails?

I'm wondering whether it's best to go for high-tensile screws/bolts or whether A2 stainless is good enough....

Also where peeps have found a good place to source socket-head-screws? Did you just get them off eBay?

JoeHarris
29-10-2012, 09:56 PM
Also where peeps have found a good place to source socket-head-screws? Did you just get them off eBay?

Screw fix is always a good place to start?

Jonathan
30-10-2012, 01:03 AM
I use the local fasteners shop (Charnwood Fasteners). Perhaps search for places that sell fasteners nearby as they should be much cheaper than eBay or Screw-fix.

JoeHarris
25-01-2013, 07:10 PM
Adil, how's the build going??

Iwant1
25-01-2013, 10:35 PM
Hi Joe, thanks bumping for my build thread. I've been quite busy with other things and haven't really had time to work on it. I can see my life getting less hectic in a few weeks and that's when you'll see a big jump in progress. I'm getting all the ali plate for the whole z axis, gantry ends and all motor mounts machined. I've seen some teasing pictures, but I'll post when I get them in my hands, and I can't wait.

I got some new tools to play with off ebay to help when I start building. There's a band saw, metal chop saw, stick welder and drill press. I got an eye open on a bargain metal lathe and engineers straight edge. Suppose you can say I'm getting my home workshop ready not just to build the router, but for all the projects to follow.

Some of the recent threads about dual motor X axis vs single motor and long belts, then another about 10mm pitch screws have got me thinking again. Suppose these are thing which can be upgraded easily if I'm not happy. So might just use 1 motor with long belts on my 1605 screws, as that's what I have prepared for, then go from there.

Adil

JoeHarris
25-01-2013, 11:02 PM
Glad things are still ticking along in the background, I too now have a stick welder to play with and seem to be making reasonable progress?!

I saw the 10mm pitch threads too but now I have the 1605 I'm sticking to my guns. The results dean gets from 1605 are plenty good enough for me and if I can get to anywhere close I'll be a happy man!

Look forward to seeing those ali bits and pieces when there done.... Cheers joe

Jonathan
27-01-2013, 11:16 AM
I saw the 10mm pitch threads too but now I have the 1605 I'm sticking to my guns. The results dean gets from 1605 are plenty good enough for me and if I can get to anywhere close I'll be a happy man!

The thing is, it's not just a question of does the machine work well enough with 1605. If 1610 is used where appropriate, then you will get better acceleration and probably higher feedrates with the same motors. The maths to prove that is simple - moment of inertia (J) of 1610 and 1605 is pretty much identical, but to get the same acceleration 1605 needs to spin twice as fast. Torque is moment of inertia multiplied by angular acceleration (Newton's 2nd law), so since we require double the acceleration the torque is twice as great.
Now you may say that you don't need these benefits, since the 1605s are 'good enough', but the point is if you leave it at the same speed and acceleration as you get with 1605 and use 1610 the required torque from the motors is lower. That means you're running further from the limit, so are less likely to have problems since the system isn't being 'stressed' so much. That's not to say you should immediately sell the 1605 screws, since it's no loss to try it and see.

Iwant1
27-01-2013, 01:54 PM
That's not to say you should immediately sell the 1605 screws, since it's no loss to try it and see.

That's exactly what I plan on doing, stick them on and try. If 1605 doesn't work well for me, a pair of 1610 at 1300mm will cost an extra 100 + p&p so its not too bad. What I'd like to clarify, is resolution regards pitch, and micro stepping, and pulley reduction. here's the situations:

1. stick to my 1605 and gear 1:2 to get effective 10mm pitch but, will my nema23 have the torque needed for this gearing? I got the option to gear 1:1 when I need resolution,

2. buy 1610 and gear down 2:1 for high resolution, and stick to my nema23

3. buy 1610 and use micro stepping when high resolution is needed.

Thanks

Jonathan
27-01-2013, 02:38 PM
Microstepping helps with resolution, but not as much as it initially appears to. The datasheets for many stepper motors specify that the tolerance on the angular position for each step is 5%, for a 200step/rev motor. That means you can say with some confidence that if stopping on a full step, the motor will be accurate to 1/(5/100%)=1/20th of a step. That implies that down to around 1/20th microstepping you'll gain resolution, however when stopping on microsteps the tolerance is worse since the relationship between the reluctance of the rotor, and angular position, is not ideal. It's hard to say exactly how much resolution you can gain. My micro lathe has 4mm pitch ballscrews, geared 2.5:1, so the effective pitch is 1.6mm and with 1600step/rev (1600 is good number to use in general) that's 1um per microstep. If I put an indicator on it and try and measure this, the axes do appear to move about 1um per step, which is promising but bear in mind that's in a static situation. Whilst the motor is spinning continuously it will be less accurate. Arguably the main bonus from microstepping is it means the motors are exciting the system at a higher frequency, so problems with resonance are attenuated.

I can think of very few parts that would benefit from the 2* resolution gain got from using 5mm effective pitch instead of 10mm. There's only one part I've made where I decided to swap my pulleys round to get higher resolution, and that wasn't the Mayan calender. However there are numerous other reasons to use pulleys, so it's still a good idea to plan for the ability to swap them to get the higher resolution. If you stick with the 1605 screws then option 1 (1:2 to get 10mm effective pitch) will work substantially better than 1:1.

Unless you'

JAZZCNC
27-01-2013, 04:33 PM
If you stick with the 1605 screws then option 1 (1:2 to get 10mm effective pitch) will work substantially better than 1:1.'

You can't say that without knowing what's being done with machine.? 1610 doesn't work better it just allows higher speeds and if those speeds aren't needed then there's no point.! . . . Infact it's wasted resolution/torque.

That said I didn't realise Adil bought 5mm pitch screws for all axis and believe he mainly wants to cut wood in which case 10mm pitch would have been better suited. But as we know it's not the end of the world and with belt gearing easy sorted.

Regards Micros stepping then Really you shouldn't consider micro stepping for resolution it's biggest help is with smoother operation of the motors at lower speeds and like Jon says it helps with resonance. Just remember the higher you set the resolution the harder the Parallel port has to work putting out more pulses's for the same movement so you'll need a good PP port other wise you could easily lose steps. More than 2000(10x) micros steps is pointless really has most of the Cheaper motors can't resolve to higher than that.

Iwant1
27-01-2013, 05:42 PM
Jazz, I bought my 1605 screws 2-3 years ago, don't think 1610 would've been available then, maybe, can't remember.

You are correct, I will be mainly cutting wood and MDF, next perspex, and dabble in ali. So I do hope my design will cope with the stress of cutting ali now and again.

Am I right in thinking for wood/MDF and plastic, 10mm screws are ideal as motors will be working in their ideal region giving 7mtrs/min cutting speeds, but 5mm geared up will just about work without getting to close to the motors critical speed and screws whip speed. The calculations suggest 1200mm 1605 screw will whip at around 1000 rpm. So even with gearing up, the motors can now spin at 500rpm, giving the screw 1000rpm which is still 5mtr/min. Will I be able to go up to 7mtr/min cutting or just for rapids.

Then for machining ali, 5mm pitch is best, but can we cut with 10mm screws, or do we have to gear down? What is the cutting speed for ali? I had a number of around 2-4mtr/min. When you mainly machine ali why are you using 1:2 on your 5mm pitch screws?

Adil

Jonathan
27-01-2013, 05:57 PM
Cutting aluminium will be fine regardless of which screw you use since it's only possible to use around 0.6-1.2m/min. With regards to resolution 5mm is better, but it's not a big difference and you're unlikely to notice it. If the critical speed is 500rpm, then yes that means you can get 5m/min, but not 7m/min since that would be exceeding the critical speed. The critical speed formula should be treated as a guidline, since it doesn't take into account the support from the ballnut and relies on a constant you select for the end-fixity, which is a bit of a guess. However I still wouldn't be happy with operating much above what the formula states, even if it looks OK. Have you seen irving's motor calculation spreadsheet on this forum - it may help clarify things.

JAZZCNC
27-01-2013, 07:00 PM
Has Jon says the critical speed is a guide and the reality is that you'll possible double that and still get away with it.?. . My 1500mm x 20mm screws do.!

Regards me using 1:2 mostly well that's not exactly correct. Since the last time I changed back to 1:1 it's been left that way and when I do change back it's going to be 1:1.5 because I don't the speed. I don't really need the torque or the resolution either if I'm being honest but that little overhead helps when I do need higher feeds.

JoeHarris
19-02-2013, 02:40 PM
Seems to me from reading (and that is all I can base this on) that both 5 and 10mm pitches will work pretty well on most materials if set up correctly. I was getting all worried at one stage that my 5mm pitch screws would mean I was going to be burning up the wood I was cutting due to the low feed rates then I remembered back to when I started getting into all this lark seeing machines that cut wood pretty reasonably being driven by threaded rod with pitches so small you can hardly see them! Reckon our 5mm screws will be all right. But I may live to eat my words...

JAZZCNC
19-02-2013, 06:02 PM
I was getting all worried at one stage that my 5mm pitch screws would mean I was going to be burning up the wood I was cutting due to the low feed rates then I remembered back to when I started getting into all this lark seeing machines that cut wood pretty reasonably being driven by threaded rod with pitches so small you can hardly see them! Reckon our 5mm screws will be all right.

Ermm Ye understand what your saying Joe.!!. . . BUT don't be fooled.? . . . If truth was told there bull shitting you.!! . . . You'll see many examples of flimsy machines cutting Aluminium with dremels etc but what they don't tell you is the finish is shit and the machine/spindle curled up and died 2hrs after the video.!

Same goes with threaded Rod machines the finish is rubbish the cutters wore out in 30mins and the machine fell to pieces 10mins after that.!!

Your correct thou that 5mm will be ok if you already have them but if your mainly cutting wood then I'd look at gearing at least 1:1.5 or 2:1 has that will allow the speeds needed to cut MDF/plastics at correct feeds.

JoeHarris
19-02-2013, 06:15 PM
Oh yes I moved away from threaded rod a LONG time ago!!! Just comforting to know my £500 worth of ball screws were not a waste of money!!

Iwant1
19-02-2013, 07:28 PM
I too was worried, that my 5mm screws won't be good enough, especially when spending close to 2k on the build. But then there no point on wasting valuable sleeping time, lol. Just going to use what I have, and if its too slow, and whipping about, I'll buy the 10mm pitch and use these for my plasma, or laser, or 3d printer. Got a lot of plans lol.

Danielroyal25
24-02-2013, 01:35 PM
Hi, was just reading through your post and its helped me out a lot with design ideas. I'm still at the design stage at the minute, can't wait to get started on building.
Just wondering how yours is going? Do you have any images and more advice - do's and dont's. cheers!

Iwant1
24-02-2013, 08:03 PM
Hi Dan,

I'm just waiting on the aluminium parts to get machined. To be honest, I'm not pushing on getting them done quickly, as I've got too many things on at the moment. That doesn't mean my minds not thinking about it, lol.

Since I've decided to go with dual x axis drive, my PC case control cabinet is looking too small to squeeze another am882 driver in, and also the recent decision to go with an ethernet SS and PDMX 126 BOB. So another part on my shopping list was a PROPER control cabinet, which as of today, am the proud owner of a used 600mm x 400mm x 200mm electric enclosure with slotted cable trunking, on/off switch and safety locks. Bargain at 40 shipped. Everything should fit now considering its twice the size of my PC case.
82718272

As for advice, DON'T buy any electrical components till your machine is built. Mine are just sitting there, eating up their warranties.

JoeHarris
26-02-2013, 08:41 PM
Since I've decided to go with dual x axis drive, my PC case control cabinet is looking too small to squeeze another am882 driver in.

May of missed this in your thread but why did you decided on 2 drives over the long belt option??

Iwant1
26-02-2013, 09:43 PM
After spending so many hours deciding between the two options, and after some emails with Jazz, I just bit the bullet and decided with dual drive. The main points in my decision were:

with AM882 there wasn't any issue with the gantry racking from one motor stalling as they have stall detection alarms, and the machine will E-stop before any damage is done.

Next, as for sync issues creeping in, Jazz says with descent drives this is drastically reduced compared to cheap Chinese drives. Obviously with one motor and belt its completely eliminated and is only a problem on very long jobs, which I doubt I'll be doing. Though you never know.

Then with 2 motors tucked away in the corners, it keeps the far end of my router free from belts and motors and tensioning arrangements, allowing for sliding long materials through.

With the long belt and one motor, I reckon a larger motor like a nema 34 would have been needed, and since I prematurely bought a nema 23, thought I'd use it on one side and buy another 23.

Also I think the 23 motor can spin faster at the top end, which will be ideal for my incorrectly ordered 5mm pitch screws, when traversing.

This is how I came to my choice, but it no big deal if I want to change change later. And I'm sure someone here will snap up my spare driver and motor, lol

Adil

Danielroyal25
26-02-2013, 10:01 PM
I have been pondering over the 2 motors v 1 motor decision too. I think I will be going with the 1 motor option. You know you mention there may be issues with long jobs, what is the reason behind this.
I wanted the ability to slide large boards through the machine but may settle for turning them through 180 degrees instead.

Iwant1
26-02-2013, 10:42 PM
You know you mention there may be issues with long jobs, what is the reason behind this.
I wanted the ability to slide large boards through the machine but may settle for turning them through 180 degrees instead.

From what I understand, long jobs are when you machine for 10+ hours without homing in between. Imagine one motor is losing a step here and there, and over a all those hours the missed steps could add up to a difference of a few mm's of one side of the gantry, taking it off square.

Homing would normally square it up again, but I'm not sure why on long jobs, like 3d carving, why can't you program a homing function every hour, and then continue where it left off.

Adil

Bart
23-07-2013, 09:39 PM
Hi,

I don't want to hijack this post but i have a similar design and I'd like to use your experience.

I've designed the frame etc. in inventor and from the simulation i get deflections smaller than 0,015 mm with the force of 500N excreted on a tip of an end mill. Thus, the design seems to be sturdy and good enough but I'm waiting for any suggestions.

My questions...

1. Chinese spindle - which one to chose
There is plenty of different looking spindles on ebay and even more sellers so I'm not sure where to buy and more importantly which model. Which one do you have or which one you know is safe to buy.

2. how to avoid two motors.
I tried couple designs of frames to hold one ballnut for one ballscrew in the center under the table but it's hard to get small deflection without making it very heavy. Do you have some ideas how to solve it without 2 ballscrews and motors on each side?
How is the solution, with line that winds up on a rotating drum, called?

3. what's the free play on a linear rail's open bearings?
Is there any free play on them, how much do they flex?
Also I saw couple times that max speed for linear rail bearings is 5 m/s. What happens above that speed and how does it affect service life.

4. whats the advantage of linear guidways over supported rails?
They would cost me at least 2 times more. I've read the spec and according to it they don't deflect almost at all. What are the other advantages and are there any disadvantaged besides the price?


5. End supports for ballscrew.
I saw a design where instead of end supports fixed to the gantry or frame there where bearings directly fixed to gantry/frame. It seams that it might be stiffer and cheaper. What do you think of it?
93249325
Kind Regards
Bart

JAZZCNC
23-07-2013, 11:48 PM
#1: This guy is ok. Most of them are the same spindle and probably out the same factory.?
2.2KW WATER-COOLED MILLING AND GRINDING SPINDLE MOTOR WITH 2.2KW INVERTER VFD q3 | eBay (http://www.ebay.co.uk/itm/2-2KW-WATER-COOLED-MILLING-AND-GRINDING-SPINDLE-MOTOR-WITH-2-2KW-INVERTER-VFD-q3-/370568863650?pt=UK_BOI_Industrial_Automation_Contr ol_ET&hash=item5647a01fa2)

#2: Honestly there is no solution to match driving from both sides whether twin ballscrews, R&P or belt drive it's by far the best and easiest way to get accurate stiff machine. The wire/drum is just a bodge and best doing it correctly first time.?. . You'll only end back there in the end.!!
Unless your machine is narrow format, which it doesn't look, then single screw just won't work good. Making gantry wide helps but there's a limit before it gets unusable or feasible.

#3 Can't answer that question without knowing which make and what size linear rails. What I can tell you is even the lower quality units are capable of handling forces far beyond what you throw at them or what your machine design will handle, so it will fail long before they do.!!

#4: No contest here linear rails win hands down in every department by a very big margin. They can't be compared really in accuracy and performance terms.
The other advantages are longevity, they will easily last several years longer than supported rails, even in very harsh conditions. Hassle free usage, fit grease occasionally and forget.
Disadvantages over linear rails is they don't tolerate poor workmanship and misalignment.

#5: Show us and will comment but until then not sure what you mean.?

Now your design.?? . . . You have a problem Houston (several actually).!!! . . . . but this one Is a common mistake easily missed.!
The linear bearings on the Y axis can't possibly be fastened like you have them drawn.? Chicken and egg problem.!! Fasten plate on one set and you can't access the bolts for the other bearings.!!

I'd also consider using different thickness material for the Z axis.? Those thin plates, even with the bracing will resonate while cutting which will affect quality of finish. Don't rely to heavily on the Cad simulation, without inputting all the variables and cutting forces then it won't show this. I know from experience that if you plan on cutting hard woods or hard material like aluminium then your Z axis just isn't strong enough.
Just remember no matter how well built or how strong or accurate the rest of the machine is it's the Z axis that takes all the cutting forces
and if this flex's or resonates the rest don't matter a jot.!! . . . The machine is only has good has it's weakest link, this Z design is weak.!
( Also Don't rely on the Linear rail adding strength they don't really add much.!)

GTJim
24-07-2013, 02:29 PM
Hi Adil, this is a very interesting build and a great deal of care has been give to getting the design right.
One question regarding the electronics, do you have a wiring diagram/schematic that you are using? If you do, could post it up as I'm currently struggling with this.

Jim

Iwant1
25-07-2013, 12:00 AM
Hi Bart, welcome to the forum mate and don't stress over hijacking the thread, someone needed to bring it back to life.

Jim, honestly everything is as it was few months back, i.e. in pieces. Once I've got the control panel built and I'm happy the way it works, I'll make a schematic and post it for you. It will be quite tricky though coz' it uses a few linked relays.

Jazz, nice to see your back and in full swing.

Bart
31-07-2013, 04:26 AM
Hi,
Thank you for your interest in my design

I guess I should have started with some spec of the design.


Frame dimensions
W x L: 1400mm x 1800mm

Red and Blue is steel
Yellow is aluminium 10mm thick

Linear rails
X: 1800mm x 25mm
Y: 1350mm x 20mm
Z: 380mm x 20mm

Motors:Four Sanyo Denki 103H7823-1730@$80 each - 4A, 2,2 mH, 0,65R, ~2 Nm up to 600 RPM
http://www.plccenter.com/en-US/Buy/
any suggestion of better value for the money?

Driver :TB6600

Gantry
Steel square profile 80x200x (4 or 5)mm

Z axis aluminium plate is all 10 mm


#1: This guy is ok. Most of them are the same spindle and probably out the same factory.?...
That's what I'm hoping for but almost every seller has a picture of slightly different design so I was wondering if any of them is better or more reliable then other.


#2: Honestly there is no solution to match driving from both sides whether twin ballscrews, R&P or belt drive it's by far the best and easiest way to get accurate stiff machine. The wire/drum is just a bodge and best doing it correctly first time.?. . You'll only end back there in the end.!!
Unless your machine is narrow format, which it doesn't look, then single screw just won't work good. Making gantry wide helps but there's a limit before it gets unusable or feasible.

I've just google wire/drum and it's called cable drive and it's not as easy and cheap as it seams - if it is to be precise.
Belt drive is ok but it has a disadvantage of not reducing the moment of inertia of ballscrews. Right now, one ballscrew
has an equivalent mass of 60 kg, that is as mach as moving mass for X axis and same moment of inertia as motor.



#3 Can't answer that question without knowing which make and what size linear rails. What I can tell you is even the lower quality units are capable of handling forces far beyond what you throw at them or what your machine design will handle, so it will fail long before they do.!!

Yes, I've seen the spec for the linear rails and linear guideways and bot of them are pretty strong for the size.
So for the X axis, moving mass is 60 kg and max force when cutting would probably be around 500N which gives (simplifying) 125N per linear bearing.
However, when i asked about flexing of open bearing, what I had in mind was an order of magnitude. Is it 1 um, 10 um or 100 um of flex.


#5: Show us and will comment but until then not sure what you mean.?


Homemade PCB milling machine - YouTube (http://www.youtube.com/watch?v=fnm9B2YVuFE)
start watching at around 1:35



Now your design.?? . . . You have a problem Houston (several actually).!!! . . . . but this one Is a common mistake easily missed.!
The linear bearings on the Y axis can't possibly be fastened like you have them drawn.? Chicken and egg problem.!! Fasten plate on one set and you can't access the bolts for the other bearings.!!

Absolutely right :) - I've noticed it some time ago but i was too lazy to change all the constraints :)
here is an updated photo

9364


I'd also consider using different thickness material for the Z axis.? Those thin plates, even with the bracing will resonate while cutting which will affect quality of finish. It's 10 mm aluminium plate - what do you think it should be?
I was thinking about making a sandwich of wood and aluminium to dampen vibrations. What do you think?

Sorry for slow replay but i was too busy to write a post

Best regards
Bart

JoeHarris
13-06-2017, 09:18 PM
Hi Bart, welcome to the forum mate and don't stress over hijacking the thread, someone needed to bring it back to life.

Jim, honestly everything is as it was few months back, i.e. in pieces. Once I've got the control panel built and I'm happy the way it works, I'll make a schematic and post it for you. It will be quite tricky though coz' it uses a few linked relays.

Jazz, nice to see your back and in full swing.

Adil, what's occurring mate, still building this thing ??!


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