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View Full Version : BUILD LOG: AndyUK's Build - 1.2x1.0m Gantry



AndyUK
23-12-2017, 07:58 PM
Hi All,

First things first - Thankyou everyone. This forum is an amazing resource. I've spent the past year lurking and researching, and thought it was about time to get a build log started. Now, if you don't mind, lets begin the self-indulgence!

What do I want out of this?
The biggest draw for me is learning the skills in building and improving the thing. I want your opinions and suggestions. Secondly, I want an awesome tool that can help with my DIY projects going forwards - I would like to be able to work primarily in wood (I'm thinking small furniture building, engraving etc), but want to do small things in aluminium too (like parts for models, handy things for the house or whatever). One of the more exciting applications I have in mind for the future is helping my wife with her glass work - either by scoring / cutting / engraving glass, or creating moulds for the kiln.

Tools
So, I intend to expand my garage substantially... but, I have the basics like a chop-saw, bench drill, etc. My designs are conscious of the fact I have (occasional) access to a Bridgeport milling machine and a reasonable size lathe. The largest 'tool' in the garage is me (in every sense)... I'm a Physicist by trade so can handle electronics and equations - I have greater trouble with the structural design aspects and the physical creation, so those are what I want to learn the most about - I've never welded or tapped a hole before, so they're going to be fun to learn.

The Design So Far
I've thusfar chosen a gantry-based design, about 1.2m by 1.0m which gives me a working area of approximately 1.0m by 0.8m. I think this will be large enough for any project I can throw at it, but small enough to fit in the garage and still have a degree of stiffness! I've particularly liked the common design on this forum, and have used Joe Harris' thread (http://www.mycncuk.com/threads/4513-3-Axis-CNC-router) and video logs in particular for ideas and inspiration (cheers!). I've also chosen a L-shape gantry, currently proposed to be created from a rectangular and box section steel extrusion, and a C style carriage to wrap around it, after looking at the gantry design study threads and following through the mathematics (largely helped by the cutting forces calculation spreadsheets on this forum (http://www.mycncuk.com/threads/2017-Unsupported-Precision-Round-Rail-Calculator)). I was thinking of having a dual X-motor setup, which I know is the slightly less-favoured setup around here, but I don't like the idea of large timing belts - they just weird me out. I do plan to use small belts on all the drives though to give myself some gearing and alignment flexibility. I'd expect to go for one of the large Chinese water-cooled spindles with a VFD. I was anticipating welding the square sections for the gantry, and then using the milling machine to give me good parallel even faces - same goes for the large square tubes that the gantry moves along, but they won't be welded. Not sure if the gantry side plates and the z drive plates should be made from 20mm aluminium or steel yet, so would appreciate comments on that aspect - I think the weight is still feasible with steel, and as I can machine it...? I'm also not very good at knowing where it would be good to add adjustment features, and what form they should take.

Heres a few pictures of my plans so far.... Forgive my Solidworks skills... they're not the greatest!
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I'd like your help with...
Everything!
Specifically at the moment, I'm at the stage of wanting to get the build started. I plan to construct the base frame and the adjustable height bed first, which means learning to weld. Before I dive in head first - I'd like your opinions on the overall design and in particular my base and bed design. Is there anything I've completely overlooked? The base is made from 80x80x4mm and the bed is made from 60x60x4mm square mild steel tubing, with the plates and angles you see made from 3mm mild steel. I planned to construct the base in four welded parts which will then bolt together - the two end squares, and the two central sections.

Here are a couple of detail shots:
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Thanks All, and Happy Christmas!

Clive S
23-12-2017, 08:49 PM
Andy Welcome to the forum and a merry Xmas.

You have certainly done some good research with the design. I use dual motors and home them independently with no problem.
The usual advise on here is to advise not to order any electronics (or kits of electronic)s as thing often change in the design. I don't think you will need the dual screws to be full length as you can move the nut mounting a bit further back on the gantry side and save about 200 mm of screw length.

I would also consider for the gantry HD ally profile say 90 x 45 two pieces one horizontal and the other on top vertical the slots in them are correct for BK12 bearing mount etc. so make it very simple.

Anyway just two sleeps for Xmas:beer:

Nr1madman
23-12-2017, 09:17 PM
Looks awesome!

I see a few improvements in your design that I will use if I start again with a new machine ;)

One thing I cant see clearly is the spacing of the bearings on the gantry sides compared to the spindle?
Its generally recommended to have the cutter inside of the bearings if you look from the side..
And it might be thats the case here.. but cant see clearly ;)

Skickat från min SM-G955F via Tapatalk

AndyUK
24-12-2017, 09:56 PM
Andy Welcome to the forum and a merry Xmas.

You have certainly done some good research with the design. I use dual motors and home them independently with no problem.
The usual advise on here is to advise not to order any electronics (or kits of electronic)s as thing often change in the design. I don't think you will need the dual screws to be full length as you can move the nut mounting a bit further back on the gantry side and save about 200 mm of screw length.

I would also consider for the gantry HD ally profile say 90 x 45 two pieces one horizontal and the other on top vertical the slots in them are correct for BK12 bearing mount etc. so make it very simple.

Anyway just two sleeps for Xmas:beer:

Hi Clive,

Thanks for the comments, much appreciated! I'm glad to know dual motor setups will work and I'll have someone to bug when I come across some niggles ;)

I'll try adjusting those motor mounts to see if I can shorten the screw - from memory, I think I put them there to have the motors embedded into the end of the frame (may not work, but its nice to dream - I'm thinking of adding cooling into there...) and I sort of thought having the nut mounted half-way between the linear bearings made sense - I don't suppose you happen to have any advice on placement?

Definitely will head your warning on the electronics - at the very least technology will have advanced somewhat before I'm ready to get them going! ;) I'll also try and run the numbers on the Ally profile.

Best Wishes, and a Happy New Year!





Looks awesome!

I see a few improvements in your design that I will use if I start again with a new machine ;)

One thing I cant see clearly is the spacing of the bearings on the gantry sides compared to the spindle?
Its generally recommended to have the cutter inside of the bearings if you look from the side..
And it might be thats the case here.. but cant see clearly ;)

Skickat från min SM-G955F via Tapatalk

Thanks Nr1madman! I don't think theres anything too original in here, I've just pulled in ideas from a couple of people around here - its essentially intellectual theft! ;)

The spindle vs. gantry spacing is an interesting point; at the moment the spindle is just outside the bearing (see picture below), which I gather isn't ideal. Originally this was so I could get right up to the edge of the waste board - should I make the bearing footprint larger to encompass the spindle or is the current setup okay? If so - do you have any suggestions as to how far within the footprint the spindle needs to go?

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Thanks!
Andy

Nr1madman
25-12-2017, 08:28 AM
The way to get ahead is to steal the best ideas and improve on them. So well done ;)

The way you have the bearings probably will work just fine because of the square rails you have chosen to work with. They should take the load.
Just so you know its unnecessary leverage and will intruduce forces that you could avoid.
If you were using other types of rails like unsupported rods it would be a much bigger issue :)

I know I spotted something else that I wanted to comment on but right now Im drawing a blank.. must be the snaps yesterday :D

Skickat från min SM-G955F via Tapatalk

Neale
25-12-2017, 08:39 AM
You could take the top rails slightly beyond the end of the machine to allow travel of the spindle past the edge of the base board and still keep it within the bearing span. I pinched that idea from somewhere else (sorry - "research") and it works well.

routercnc
25-12-2017, 07:07 PM
Design is basically sound. Setting motors inside the section has probably occurred to most people at some point. If worked hard they may reach 80 degrees or more so you may want vent holes in the section.

I can't see how the gantry cross beam connects to the platforms it sits on apart from the small angle bracket. You will need more than that. You can bolt down through lower inner edge of the gantry into the platform on the rectangle and possibly the square if you can get a tool inside. Or if you can weld then cap off the end of the section and drill and tap to fix the side plates. Popular way to do it for steel.

Alum profile was mentioned and this is another way to do it as you can easily tap the ends.

I would go steel as it is stiffer but both can work.

AndyUK
25-12-2017, 08:18 PM
The way to get ahead is to steal the best ideas and improve on them. So well done ;)

The way you have the bearings probably will work just fine because of the square rails you have chosen to work with. They should take the load.
Just so you know its unnecessary leverage and will intruduce forces that you could avoid.
If you were using other types of rails like unsupported rods it would be a much bigger issue :)

I know I spotted something else that I wanted to comment on but right now Im drawing a blank.. must be the snaps yesterday :D

Skickat från min SM-G955F via Tapatalk

Thanks Nr1madman, I guess its an easy thing to fix if I'm not happy - just need to remake the end plates to the gantry to extend the bearing location. Let me know as soon as you remember the other issue - personally I'm on 'Bad Santa' ale this evening which is going down a treat...!



You could take the top rails slightly beyond the end of the machine to allow travel of the spindle past the edge of the base board and still keep it within the bearing span. I pinched that idea from somewhere else (sorry - "research") and it works well.

Hi Neale,

Great plan! I guess if I do this or not sort of depends on the gantry rails levelling method I choose. I'd like to avoid epoxy if I can get away with just using the Bridgeport (which has a 4ft bed travel - hence the limitation of these rails to 1.2m) - but I guess that doesn't perfect the height between the two rails, so I may end up with having to epoxy anyway.




Design is basically sound. Setting motors inside the section has probably occurred to most people at some point. If worked hard they may reach 80 degrees or more so you may want vent holes in the section.

I can't see how the gantry cross beam connects to the platforms it sits on apart from the small angle bracket. You will need more than that. You can bolt down through lower inner edge of the gantry into the platform on the rectangle and possibly the square if you can get a tool inside. Or if you can weld then cap off the end of the section and drill and tap to fix the side plates. Popular way to do it for steel.

Alum profile was mentioned and this is another way to do it as you can easily tap the ends.

I would go steel as it is stiffer but both can work.

Thanks - Its really encouraging to have experienced eyes looking over things.

My plan for the motors was, as you point out, cut some ventilation holes in the rails, and to try and mount a fan inside the rail (assuming the vibration isn't too much) - I'm not massively set on having them there, whilst its aesthetically pleasing I can see that placement causing all sorts of headaches while I'm trying to diagnose things!

The gantry cross beam is connected with the small angle bracket, and a pair of M6 bolts from the carriage plate up into the square steel sections (see below - this view is from below the gantry with the bearings removed). I must admit, this connection was one of the most puzzling parts of the design for me, and I'm not entirely sure that this will be up to the job. What I haven't added to the model yet, but intended to do in order to firm up this connection was add a square-ish steel plate to the back of the gantry with bolts into the smaller square steel tube, carriage plate, and gantry side plate (see second picture). I like your idea of welding a cap onto the end, thankyou - although I might not block it off completely and just half-cap to thread into - would be nice to retain an exit path for swarf and I've gathered the impression from youtube that welding things like this completely shut was generally a bad idea?

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Regards the Aluminium profile, I've been running the numbers of 90x45 Heavy Duty profiles against the steel box section. The biggest draw for me simply, as you say, the stiffness of steel - Aluminium's young's modulus is a quarter that of steel. Practically, thats the difference between 0.1mm and 0.05mm max deflection under weight once the profiles are taken into account - I'm not even sure if that'll be noticeable at the accuracy levels this machine will eventually keep - but may as well aim high now while I can!

routercnc
26-12-2017, 08:52 AM
Hi Andy,

I think bolting the gantry beams to the platform will be a bit awkward from underneath and will make it difficult to align everything.
Better to bolt from the top side - you will also get a better joint because the bolt will pass through the thin gantry section and tap into the thick platform. These can be cap head bolts, but if tool access it tricky then hex head will be better.

I didn't quite follow your 'square-ish steel plate idea' but if you want to bolt the gantry in place (i.e. without any welding) then better to use a solid block at the top and bolt it to the gantry, and bolt the side plates to that. Will get a nice support from the top of the gantry down to the platforms. The small L corner brackets are not really up to the job.

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I think you said as much but make sure the gantry pieces are connected to each other otherwise you don't get the benefits of the much larger overall shape. Either bolt the inner faces together, using a clearance hole in the rear face of the small square to pass the bolt through, or weld them.

p.s. aluminium is 1/3 the Young's modulus of steel, not 1/4. So in like-for-like sizes steel is stiffer. But as aluminium is less dense (therefore lighter in a like-for-like size) you can increase the aluminium size or wall thickness and recover the stiffness and be no heavier than the steel version. Aluminium profile is easier to bolt together, so good if you don't have a welder. But then aluminium is expensive. In short, use what you feel comfortable working with - either can work well.

Clive S
26-12-2017, 10:12 AM
Aluminium profile is easier to bolt together, so good if you don't have a welder. But then aluminium is expensive. In short, use what you feel comfortable working with - either can work well.

It might also be worth noting that the 90x45 ali profile can be tapped 12mm with a spiral tap very easily in the end holes which make a build quite simple.

Desertboy
26-12-2017, 12:42 PM
It might also be worth noting that the 90x45 ali profile can be tapped 12mm with a spiral tap very easily in the end holes which make a build quite simple.

Or if you buy it from KJN they'll tap the ends for a couple of quid if you're lacking taps and I remember I think it was alex had issues until he got the right tap then it was super easy.

I never tapped the extrusion I used an impact driver to force the M12 bolts into the extrusion, I used corners and T nuts to keep the extrusion straight (My frame is 9045) but the gantry I recessed the aluminium into the aluminium plates by 5mm each side (20mm thick plates) which kept the gantry straight whilst I bolted it on.
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I got the Hiwin recess wrong so I ended chopping 1.5cm off the Hiwin's which when I checked the Cad model was obviously wrong lol I must have been having a moment.

Hiwin's are rated for 95%+ of their loading capacity when mounted sideways on this is why on my machine I mounted the Hiwin's where the ballscrew is on yours and the ballscrew when you have the hiwins.

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Removes triangles considerably simplifies the build but increase gantry plate height which can be an issue with flex. I'm only cutting wood and I made my gantry mounts 20mm thick so I don't think this is a problem for me. If and when I build again I'm going to build it same way I did before but undersling the ballscrew so it's out of way of any debris.

I have to say the No.1 thing I would do differently is rotating ball nut but if not then 10mm pitch ballscrews my router is very close in size to yours my travel is 130cm*70cm but I got 5mm pitch ballscrews and this is the biggest mistake I made on my build. (If you exclude me blowing up 1 PSU lol)

As for electronics I went with 4 AM882 (£240 new from China, Toroidal transformer for 70v (£80 from Rapid), $5 BOB for control with a PC parallel port and linuxcnc. I do intend to add an 7i73 board (allows me to use ethernet to breakout boards instead of PP) but I would say the setup I have is the bear minimum for a decent router. Stall protection being the bare minimum in a stepper driver.

Good luck with your build.

AndyUK
13-11-2018, 07:09 PM
Okay, so its been approximately a year. I suppose I'd better post an update or two!

First things first, current drawings:


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I mulled over the advice I got from Clive and routercnc for a long time. far too long. I repeated my deformation calculations with various materials and geometries. Ultimately, Aluminium won :) There's a few solid reasons:

Cost - It isn't as bad as I expected. The aluminium profiles are only about £50.
Ease of working with. The connection to the side plates is just so much easier.
Deformation is tolerable. I think it increases vs my steel design from 3.0um to 4.9um - Lets be honest, its never getting close to those tolerances elsewhere!
Proven history of this configuration working for others on this forum.


That decision also cemented the plan for making the side plates out of 20mm aluminium plate - and I think they look reasonable. The other factor is that the milling machine is currently in storage a couple of hundred miles away, and at least I can work aluminium in my garage :D This means I'm also planning on going down the epoxy route for levelling the x-axis, and my belief is that the y axis on the ali-profile should be reasonable out of the box (?). That also allowed me to further copy Joe (thanks bud!) and start designing my motor mount locations etc.

Plan for the motors is that they're all going to have a 15mm timing belt connection to the ballscrews. I believe this allows me some flexibility to gear up/down in the future.

I want to start ordering the linear motion bits - so I've got a few questions:

I've up-beefed the x-axis ballscrews to 2010 1100mm. The y axis is currently 1610 750mm, and the z is 1605 250mm. I'm having a little crisis of confidence in these though, so before I bother Fred for a quote, does that sound right to everyone? Does that get appropriate speeds for what I'm planning on doing? I'm probably mostly cutting wood and occasionally glass and aluminium - I guess I can gear the x axis if it becomes a problem? I was planning on 4x 6nm Nema 23s.

Second crisis of confidence about the screws is the bearings. I'm planning for a BK15 and BF15 (one either end, fixed at motor) for the x axis, then BK12 and BF12s for the Y and Z. Add to that a ballnut for each screw, and thats everything right? :)

Finally, I think my linear rails are as follows: All 20mm, 1200 on X, 850 on Y, and 400 on Z. I think I'll need 12 carriages. Sound good?

AndyUK
13-11-2018, 09:58 PM
And, just to prove I haven't been completely slacking off since last year - some progress photos!

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Large steel delivery (about three hundred quid for the base frame and adjustable bed + some sizable offcuts). Lots of cutting... then lots of cleaning up the pieces to make them nice and shiny and easy to weld. At this point, also, you know, learnt to weld a bit :)

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Marking up - discovering what marking up fluid is, and then having to find my own tub! At this point I couldn't wait to layout the steel in approximate locations to give me a better idea of size (wife redacted!)

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Worth also mentioning that part of the reason I've been so slow with this project to date is that I started it a couple of months after buying our first home. My workshop needed a little attention due to a steel lintel which rusted and pushed up the top few brick layers, and the window had rotted out - so here's a couple of pictures illustrating what we did with it. We followed this up with a complete rewire. Notice large pile of steel under bench...

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LOTS of drilling, and LOTS of tapping. I said in my first post I'd never tapped a hole before this. Well, Now... lets just say there were evenings I wore blisters! Should probably have got myself a power-tap, but hey, all good experience.

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By this point the milling machine had made it into storage (for various reasons...), and I wanted to get on with my steel plates for the bed. The shape is cosmetic anyhows, so I went ahead and used the solution to hand, which was a jigsaw with a metal blade. Was quite exciting to do a quick visualisation - although a bit of a tight fit before clearing the space for it! Note that one of the key changes I've made is bolting the frame together initially - I still plan to weld it, but I liked the idea that I could assemble then tack weld once I'm happy with the structure and basic alignment. Whilst I doubt it will help much with distortion, it has prevented me from making any big cockups with the basic dimensions of the base frame - and that steel is expensive!

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Time to sort out the angle iron - needed quite a few of these since I started bolting together. Took the opportunity to borrow the bandsaw whilst at the in-laws and get them nicely cut to size. Marking them was a bit of an onerous task, so as my wife had recently taken up 3D printing as a hobby, printed out a jig to prevent me needing to measure! Worked surprisingly well, as our off-the-shelf middle-of-the-range printer is astonishingly accurate on its dimensions.

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Now that I had the angle pieces, I could start bolting the base together. This is pretty much how it stands today - I've added the other two cross bars, and tightened it all down. I was gobsmacked when I went around measuring the dimensions against the CAD model, to find everything was smack on what I designed it to be - although I don't have a meter long pair of calipers so I'm calling close enough!

Next stage is to start assembing the adjustable height bed - this time I'll be welding straight out of the gate, then I need to tack weld the base frame together and design some height adjustable feet. I'm considering drilling into the concrete base of the workshop and attaching it down - thoughts? Otherwise, as I mentioned in my last post, I want to get the linear motion components on order, and order the aluminium profiles for the gantry to begin assembling those.

Thanks for reading this far - its quite fun sharing this now I've eventually gotten around to it! :) I certainly wouldn't be able to get any of this done without the help and guidance I've found on this forum already.

AndyGuid
14-11-2018, 12:53 AM
. . . . . . .

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Marking them was a bit of an onerous task, so as my wife had recently taken up 3D printing as a hobby, printed out a jig to prevent me needing to measure! Worked surprisingly well, as our off-the-shelf middle-of-the-range printer is astonishingly accurate on its dimensions. . . . . . . .


Like that thinking! What make and model 3D printer are you using?

The large dimension box section you've used for the base frame is great but I would suggest that, when you get to the welding stage, you stiffen the frame by triangulating with diagonal bracing.

Personally I would brace roughly the bottom half of the side frames (sorry about negating those bottom drilled holes for the adjustable bed. Eek!)

Your build thread reminds me of the build by Joe Harris, and is a good one to follow!

Andy

AndyUK
19-11-2018, 01:31 PM
Like that thinking! What make and model 3D printer are you using?

Thanks Andy :) We're using a Creality CR10-S. Was printing accurately with PLA within an hour of opening the box - very pleased with it so far.


Personally I would brace roughly the bottom half of the side frames (sorry about negating those bottom drilled holes for the adjustable bed. Eek!)

So we're on the same page, I guess you're talking about adding the red lines in the diagram below, rather than the green? I suppose if they were removable bracing they wouldn't foul the adjustable bed permanently... I was hoping to use the lower sections of the frame for a second structure, like a coolant trap or something.

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AndyUK
22-11-2018, 01:13 PM
I want to start ordering the linear motion bits - so I've got a few questions:

I've up-beefed the x-axis ballscrews to 2010 1100mm. The y axis is currently 1610 750mm, and the z is 1605 250mm. I'm having a little crisis of confidence in these though, so before I bother Fred for a quote, does that sound right to everyone? Does that get appropriate speeds for what I'm planning on doing? I'm probably mostly cutting wood and occasionally glass and aluminium - I guess I can gear the x axis if it becomes a problem? I was planning on 4x 6nm Nema 23s.

Second crisis of confidence about the screws is the bearings. I'm planning for a BK15 and BF15 (one either end, fixed at motor) for the x axis, then BK12 and BF12s for the Y and Z. Add to that a ballnut for each screw, and thats everything right? :)

Finally, I think my linear rails are as follows: All 20mm, 1200 on X, 850 on Y, and 400 on Z. I think I'll need 12 carriages. Sound good?

No readers objected violently, so I've got a quote for the above from Fred. Very helpful and quick service.

First thing he pointed out was that I needed to specify that I'm planning to use timing belts on the ballscrews rather than direct connections, as the machining will be different. Can anyone shed some light on why? Is it a different shaft diameter or is it keyed or flatspotted for a grub screw?

Second point is he has offered two types of BK support, one with upgraded P5 AC bearings. Any thoughts?

Clive S
22-11-2018, 01:25 PM
No readers objected violently, so I've got a quote for the above from Fred. Very helpful and quick service.

First thing he pointed out was that I needed to specify that I'm planning to use timing belts on the ballscrews rather than direct connections, as the machining will be different. Can anyone shed some light on why? Is it a different shaft diameter or is it keyed or flatspotted for a grub screw?

Second point is he has offered two types of BK support, one with upgraded P5 AC bearings. Any thoughts?

Probably because on the ball screw where the pulley fits is called the F length I think from memory this is about 25mm if you are using pulleys then tell him to make it 30 or 35mm you can always cut it shorter.

Go for the best bearings re the BK

Zeeflyboy
26-11-2018, 07:34 PM
My plan for the motors was, as you point out, cut some ventilation holes in the rails, and to try and mount a fan inside the rail (assuming the vibration isn't too much) - I'm not massively set on having them there, whilst its aesthetically pleasing I can see that placement causing all sorts of headaches while I'm trying to diagnose things!

If motor heat is a concern (and generally they are designed to run hot without a problem, worth a quick check of the specs) you could always plumb them into the water-cooling loop you will have anyway for the spindle. Just a generic water block attached to the motors enough to pull away a good amount of heat - i've seen similar done for 3d printers where the motors are inside of the heated enclosure.

Overall design looks very nice, you've clearly done a good deal of reading and research. I'm sure it'll be a good machine!

End machining will be different re pulley or direct coupling. That is not to say you couldn't make a direct drive coupling end work with a pulley, you'll just be making your life more complicated.... go with best angular contact bearings you can afford.

AndyUK
26-11-2018, 10:15 PM
If motor heat is a concern (and generally they are designed to run hot without a problem, worth a quick check of the specs) you could always plumb them into the water-cooling loop you will have anyway for the spindle. Just a generic water block attached to the motors enough to pull away a good amount of heat - i've seen similar done for 3d printers where the motors are inside of the heated enclosure.


What a great idea! It was only this morning I was pondering making some sort of heatsink for them. Last night I read a thread on here from July which was quite negative about enclosed motors. I'd been thinking along the lines of aluminium block and some copper heat pipes, but water cooling is an excellent idea which deserves investigation :)

http://www.mycncuk.com/threads/12075-can-Nema-23-s-be-placed-inside-box-tubing-X-Y-axis


Overall design looks very nice, you've clearly done a good deal of reading and research. I'm sure it'll be a good machine!

Thanks! As I say, mostly ideas are 'borrowed' from others ;) I'd love to make something that looks as professional as your current project (I love the way everything is covered and enclosed on yours) but I think that is a bit beyond me for now... maybe next time eh? :)



End machining will be different re pulley or direct coupling. That is not to say you couldn't make a direct drive coupling end work with a pulley, you'll just be making your life more complicated.... go with best angular contact bearings you can afford.

Cool, thanks for the tip. I'm currently discussing Clive's suggestion with Fred, and taking his advice as he clearly knows his stuff. Hopefully not too far away from getting these major components ordered. Going to go with the upgraded bearings, and I'm also taking the opportunity to get the Spindle + VFD while I'm at it from someone reputable. Hopefully will also cut down on the shipping costs.

AndyUK
14-12-2018, 05:33 PM
Very exciting package just arrived!

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Still working my way through it, but all looks spot on so far. Very pleased and impressed by Fred.

For those of you who are trying to price up your builds in the future, I think this set me back approx £1150. It includes everything you see above - all my rails, ballscrews (+bearings and mounts), and spindle, inclusive of delivery, VAT and Customs. I think it would have cost ~£2000 from a UK (re-)seller.

AndyUK
17-02-2019, 08:17 PM
Hi All,

Hard at work as ever, just about finished welding the frame and will be painting soon... I've also got the main gantry structure together, and have starting cutting the aluminium components to form the Y and Z carriages. Photos soon, I promise!!

Quick question though - my linear rails on the gantry are collecting a bit of dust - whats the best way to clean and (oil?) them? Any recommendations for grease to flush the HGR20 carriages through with? And I need a grease gun... any advice appreciated.

Thanks in advance folks!

Lee Roberts
17-02-2019, 08:35 PM
I'd clean and flush with oil then use some multipurpose lithium 2 grease as its quite cheap to buy, some links on it below :).

Spec me some lube! (http://www.mycncuk.com/threads/11748)

Profiled rails - Installation guidelines and manufacturer comparison chart (http://www.mycncuk.com/threads/4862-Profiled-rails-Installation-guidelines-and-manufacturer-comparison-chart?p=55256#post55256)

Lithium Grease 400g - Toolstation (https://www.toolstation.com/lithium-grease/p89691)

AndyUK
17-02-2019, 08:37 PM
Legend! Thankyou - Your forum searching foo is far superior to mine ;)

AndyUK
17-03-2019, 09:26 PM
Promised a couple of photos of the aluminium parts... so here we go - Don't judge my sloppyness too harshly ;)

I've been using the printer at work to get drawings printed out as accurately as possible. I'm then using contact adhesive to attach them to the aluminium, which makes the drilling process a lot easier. The drawings get a little busy and unprofessional, but it helps when I'm checking how accurate the printout is to be able to quickly know what each relative dimension should be.

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Oh my life - the counter bore cutters are amazing. I love these things.

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So, after some bandsaw action, some broken drill bits, a screwed up aluminium part (try and spot whats asymmetrical!), and some other parts made, I finally got around to some rough first-time assembly this evening. The rails aren't perfect yet - they're dialed in to about 0.02mm from the surface of the Ali extrusion whilst I'm awaiting my precision straight edge which is back ordered, but the carriage went together like a dream, and runs nice and smoothly along them.

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Lee Roberts
17-03-2019, 09:52 PM
Looking good Andy,

I and a few others I know print things out like this and it works quite well, if you set your printer to print at a 1:1 scale, it should print out "reasonably close" to true 1:1, then you can just measure what you get on the print out and adjust your printer settings accordingly, though I've never had to do this as its always been good enough.

Great build keep up the good work !

AndyUK
06-04-2019, 10:51 PM
Hi All,

Small progress update; welding and grinding on the frame and bed is completed, I'm currently prettying it up, and will start painting soon. Once my ugly welds are covered up sufficiently I'll share an updated photo ;) I've got the Epoxy sorted, so that'll be the next job on the frame once the weather improves sufficiently.

I'm starting to ponder the electronics, and its all a little overwhelming. I don't think my budget stretches to servos, so steppers it is, and from the quick calculations I've done it appears I'll be wanting the standard ~3nm steppers with a ~70V homebuilt PSU. I'll be putting more thought into specifics and posting my thoughts before ordering them, but I'm utterly lost when it comes to narrowing down drivers.

Lets take Zapp Automations 3.1nm NEMA 23 stepper (https://www.zappautomation.co.uk/home-page-products-2/sy60sth86-3008b-nema-23-stepper-motor-48577.html) for example (it appears to me to be the standard) - it has a bipolar parallel (which appears to be the standard config) max rated current of 4.2A, so I'm thinking any stepper motor driver able to cope with >4.2A will be able to use the motor to it's full potential (more to the point, I'll have to limit the current on the driver). I'll probably want a motor driver capable of microstepping - and in this regime there appears to be named brand and off brand:

Gecko G2xx Drives - the difference appears to be the native stepping resolution and their microstepping capabilities, generally all in the £100+/ea region. I've seen a few US-based bloggers I trust using these and seem quite happy which is tempting.
Leadshine as used by a few people here... £50-100/ea from that I can see.
Random Brands, Same black box... £40-50/ea

Regards microstepping I have 2010 on X, 1610 on Y, and 1605 on Z (currently all planned for 1:1 but pulleys so room to gear) - lets take the 10mm pitch screws, 1.8steps/degree means half stepping nets 0.025mm/step - is that a reasonable target?

So can anyone shed some light on Drivers and point me in the right direction? Maybe point me to a resource which explains whats what, and what I need to look for to identify a reasonable product?


Second, I had originally thought of using a CSMIO/IP-M controller - I liked the ethernet functionality, 24V lines, and the fact that it was well documented, recommended, and provided a command buffer - BUT - I've been very aware that it has two very key draw backs for me: no good slave axis functionality for my dual x-axis screws, and four axis limit which would be a pain in the future if I wanted to add a 4th axis. I'm not keen on the cheaper parallel port breakout board style (rightly or wrongly, I'm kinda dumping the UCxxx controllers in here - please correct me if I'm wrong), but I have been thinking about the ESS ethernet smoothstepper. From what I can tell, it has the capability to handle up to 6 motors which allows future expansion, and can handle the dual screws and independent homing well - but it needs to be combined with a suitable BoB and only provides me with 5v IO which I'll need to put more effort into sorting.

Can someone tell me if I'm on the right lines, or if theres something drastic I'm missing or some better option? I'm really keen to have a robust and smooth machine.

Thanks for listening to the fevered rant this far - double thanks if you're able to put me straight on a question or two!

Neale
08-04-2019, 11:02 AM
Microstepping - yes, half-stepping probably gives you as good a resolution as you need for a router, but the thing will run like marbles in a cement mixer! Go to x8 microstepping and it runs much more smoothly. Go much higher and you start to lose torque - x8 or so is a good compromise. That's my experience - steppers just don't run at all smoothly unless you microstep them.

Try some critical speed calculations (there are online calculators available) to see what max speed you can run your ballscrews at. Those X screws will probably go up to around 800RPM (exact figures depend on which calculator you use - my machine uses 1750mm 2005 and I can run up to about 900-1000RPM). Then look at what kind of rapid speed you would like, and work backwards to get pulley ratio. My 3Nm steppers run at around 1000RPM before starting to lose torque, so 1-1 with my ballscrews gives me about 4500-5000mm/min rapid. That's fine for me but your 2010 with, say, 2-3 pulley ratio, would give you more speed and the pulley ratio will increase available torque on the ballscrew to help. But play with the numbers - there are trade-offs here. I am happy with my machine because I mainly do small fiddly work which needs acceleration rather than high max speed but your needs might be different. There are also 4Nm steppers around (I think that CNC4YOU sell them, for example).

Drivers - I use EM806 and am very happy with them. Gecko are popular in the US but remember that they are a US product and there is an automatic bias towards "locally made". Understandably - and i believe that there are now tariffs which penalise Chinese imports! But in the UK we have a wider choice. Main points are enough current capacity (you have identified this), enough voltage headroom (EM806 is rated at 80V which works well with 68-70V PSU), and digital control - partly for smoother motion, partly for stall detect which I feel is vital if you are using dual-motors. Every so often I get a stall for some reason and the machine stops immediately without tearing itself apart. The 806 is a more recent Leadshine offering but there are clones of the previous model whose number I forget) widely available at lower cost. Any driver in this kind of range will support adequate microstepping, almost certainly. Plenty of people use the cheaper version although I chose the 806 as it looked as if the previous version was becoming obsolete. And so it was, but it seems only from Leadshine and the clone industry then took over!

I also use an IP/M. No, it does not properly support dual-axis homing, although assuming you have a way to home your machine, it does understand the concept of a slave axis and will drive it happily. For a long time, I homed my machine via the usual Mach3 option, then disabled the drivers to allow the slave stepper to be turned by hand, and tweaked it until the LED on the proximity switch tripped. Crude but effective. However, someone recently reported on the forum that you could go into the IP/M config tool in Mach3, disable slaving, then use a modified Mach3 homing routine to home X+A at the same time. This works very well. You then go back and re-enable slaving and carry on as before. My machine was built with adjustable targets for X and A, and by tweaking I can get good reliable squaring this way. It's a slight fiddle, but you normally only need to do it once at the start of a session.

The 4-axis limit is more problematic with the IP/M. If I were doing it again, I would probably go UC300ETH plus UB1 breakout board. As far as I can see, this is very similar to the IP/M with 24V signalling and plenty of I/O. And 6 axes! Can't remember now if it does differential signalling to the stepper driver, though, which is an CSMIO feature and, I feel, worth having if possible. Better noise rejection, in short, as with 24V signalling. 24V is useful if you use proximity switches as these typically run with 10V plus. When i tested mine, I found them a bit flaky at their nominal lowest voltage but they are fine at 24V, and I happily run them in pairs in series on X and Y so upper and lower limits go to the same input pin. Keeping XYZA on separate pins is useful on a larger machine as you can home multiple axes simultaneously that way in Mach3 (I home Z for safety, then X and Y at the same time, or XYA at the same time for initial homing as above). Using the UC300 also means that you could look at the UCCNC software in place of Mach3. I still have reservations about Mach4, and you have to be very careful about the exact version of Mach3 you run with the CSMIO plugin.

Anyway, just my thoughts, and I'm sure that others will disagree!

AndyUK
08-04-2019, 09:52 PM
Thanks Neale, that was a super helpful post, and its going to take me a few evenings to reply in full!

Lets talk numbers first, because I've being doing these calcs behind the scenes. I've written my own version of irving2008's motor calc sheet. Its basicly the same, but I'm doing the calcs myself so I understand it, and I'm doing all three axis at once. I've also modified it to cope with dual screws on the X (I've doubled the screw inertia then doubled the Est Torque output - which in my head counters the additional drag of driving an extra screw against the additional power output.)

I've set the sheet up here for 5500mm/min, with a 50N (Ali) cutting force. Its currently not setup for gearing at all - and I have a microstepping factor of 1x because I haven't thought how to include these factors yet.

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So, with 2x 4.0 Nm on the X we can just achieve this setup (I say just - as per the original spreadsheet there's a 3x Margin on the required torque), and rapids at 9000mm/min whilst staying below 900rpm (below corner and 80% of critical speeds). Note that although I've simulated 3.1 Nm on the Y and Z, they're massively overkill. Especially the Z.

Questions are - does this look realistic and okay? Is my dual screw fudge acceptable or are there any obvious holes?

Any tips on how to integrate the pulley factor and microstepping? How do I take these results and figure out what gearing to use?

Thanks!

AndyUK
26-04-2019, 12:18 PM
Quick Update;

I've decided to go with a 1:1 ratio for now (which was always the intention) but by designing in the pulleys, I'll have the option for change in the future. This means that the dual 4.0Nm on the X should do okay, and despite the overkill, I've gone for 3.1Nm on the Y and Z (thinking being if I have issues with one motor, I'll have an identical one to swap in and out for troubleshooting).

I've also done a lot of investigation around motor drivers, and have ultimately followed Neale's recommendation with the EM806s - they seem to tick all the boxes for me and the stall detection is a really big draw. That, and Zapp's sale means they're very reasonably priced! (£62/ea rather than £105-£110/ea elsewhere).

Still quite undecided about breakout boards / control boards, although I'm moving further away from the CSMIO offerings. Watch this space!

AndyUK
26-04-2019, 05:51 PM
Now that I know my motor and drive choices, my thoughts have rushed ahead to the PSU for the drives. This is all speculative, but I wanted to air my thoughts.

We have 2x 4.2A Max steppers, and 2x 4.0A Max steppers. Thats a load of 16.4A at full pelt, but the drivers only need 60-70% of that current. So worst case, I need between 9.9 and 11.4A. Lets call it 12A for the sake of overbuilding things.

The highest inductance of my motors is 3.2mH. So, 32*sqrt(3.2) = 57.2V Ideal voltage. Drivers can take up to 80V.

The secondary voltage of an unregulated PSU is increased by the capacitor bank by a factor of sqrt(2) - So I'm aiming for an ideal secondary voltage of 41V.

12 A * 41 V = 492VA. This is the minimum power of transformer I'll need. Standard size options are therefore a 500VA transformer, or a 625VA transformer would be the next size up. Standard secondary voltages in my range are 2x25V (in Series = 50V), 2x40V (in parallel) or 2x45V (in parallel). I'm therefore looking at a 500 or 625VA transformer with 2x45V secondaries, giving a voltage to the drives of 64V.

Capacitors wise, to achieve a 5V ripple at 50Hz under full load (which keeps me above the ideal supply voltage) I'm looking at C = 12A / (4*50Hz*5V) = 12,000uF. But more won't hurt. Also, while we're talking capacitors, I ideally want them to be able to cope with 2x V (so 120V), but 100V rated caps will probably do the job.

fgfreek32
02-05-2019, 05:18 AM
looks like mine,like it25744

Doddy
02-05-2019, 07:53 AM
Just a thought with the selection of a transformer - ignoring core flux (not realistic, but bear with me) - you can use the typical twin secondaries not so much in parallel, but as two separate supplies. It costs an additional capacitor (though lower capacitance) and an additional rectifier. It means that your copper losses are reduced on individual supplies and regulation is arguably better. It's an approach that I'm trying with my type of machining (typically machining In X/Y, not 3d profiling) - so I intend to bond Y/Z on one supply and X/A on the second - my thoughts are that only one stepper is likely under load at any point in time on any one supply.

80V drivers?, some common ones in this range are AC/DC - if so just remember that the first thing these will do is rectify/smooth the supply internally.

Your preference to rate the caps at 2x VDC - your money. A bit of head-room is a good idea but 2x is a little bit frivolous. Admittedly mine are more so - at 160VDC (50V secondaries) but that's simply because I had them in the shed as part of a bulk-buy.

AndyUK
02-05-2019, 09:41 PM
looks like mine,like it

Thanks! They certainly share a few design ideas don't they? :)


Just a thought with the selection of a transformer - ignoring core flux (not realistic, but bear with me) - you can use the typical twin secondaries not so much in parallel, but as two separate supplies. It costs an additional capacitor (though lower capacitance) and an additional rectifier. It means that your copper losses are reduced on individual supplies and regulation is arguably better. It's an approach that I'm trying with my type of machining (typically machining In X/Y, not 3d profiling) - so I intend to bond Y/Z on one supply and X/A on the second - my thoughts are that only one stepper is likely under load at any point in time on any one supply.

Interesting idea - I don't know much about power supplies and transformers though, so I'll need to do more research! On mine with the two drives on X, I'd be wary of joining the X/A because they'll be drawing significantly more that Y/Z, and they'll be doing so at the same time as each other.


Your preference to rate the caps at 2x VDC - your money. A bit of head-room is a good idea but 2x is a little bit frivolous. Admittedly mine are more so - at 160VDC (50V secondaries) but that's simply because I had them in the shed as part of a bulk-buy.

Good point - but it looks like I'll end up paying about £12-15 for the four capacitors I need, at that price I can afford to over-rate them!

AndyUK
02-05-2019, 09:45 PM
So, because I've sorted my motors and drivers before the rest of the control system, I've spent the evening checking that everything works as expected before I pack them away and let the warranties tick away.... At least I'll know they all worked at least once eh?

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Simple setup with a 48VDC power supply I had lying around and an Arduino to generate the pulses. Always nice to see a stepper womble back and forth, and it means as soon as my mechanicals are ready I can test the steppers in place without needing the control system finalised.

AndyUK
22-05-2019, 12:34 PM
1x PSU Fabracobbled together.

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Still needs some hot glue on the caps (I've misplaced the glue gun - d'oh) - Testing will need to wait until the Wife gets back from a work trip, I'm not turning this one on whilst I'm alone in the house! Went with a 625VA with 2x 40V secondaries in the end, gave me 45V on the secondary, so hopefully about 63V after rectification and smoothing.

Oh, and yes I'm a muppet and ordered the wrong size capacitor clamps. 3D Printer to the rescue!!

Nickhofen
23-05-2019, 08:46 AM
It looks good!

AndyUK
02-06-2019, 06:29 PM
Hi All,

Wiring Diagram, V1 attached! Please note future builders, this is a very early days schematic - I don't have half the components and most of these connections are untested.

Questions I'm currently pondering:


Theres currently no ground to the UB1, and by extension anything that it connects to, other than cable shielding. I feel like I should be grounding the motor drivers or something...!
Does the E-Stop circuit look okay?
Need to find Limit and Home switches and then tailor diagram to their requirements.
Need to figure out what I'm doing with the 4th pin on the spindle re grounding. Does the ground go to the VFD like I've shown?
Noise suppression - The VFD and the 24V/60V PSUs will be sharing a mains connection. The garage is on a 16A spur, so it's quite hard to get cable distance between them, is there something I can put into the system to suppress the noise from the VFD?


Thanks Nick, I've been using a few of your diagrams on here and CNC Zone :)

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Doddy
02-06-2019, 06:39 PM
Hi All,

Wiring Diagram, V1 attached!

Questions I'm currently pondering:


Theres currently no ground to the UB1, and by extension anything that it connects to, other than cable shielding. I feel like I should be grounding the motor drivers or something...!
Does the E-Stop circuit look okay?
Need to find Limit and Home switches and then tailor diagram to their requirements.
Need to figure out what I'm doing with the 4th pin on the spindle re grounding. Does the ground go to the VFD like I've shown?


Thanks Nick, I've been using a few of your diagrams on here and CNC Zone :)

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1) Why? you're driving the stepper drivers through their own opto isolation - no need for common ground there, and I *think* the analogue output from the UB1 for spindle speed control is also an isolated supply. Don't worry about galvanic shielding - the UB1/UC300 isn't shielded so you're gaining nothing.
2) Let someone else answer
3) Let you answer
4) Should ideally go to a common/star earth point, similar to the VFD earth (and the supply lead earth)

Not familiar with the UB1 - can it drive the 24V contractor coil directly?, and back emf?

AndyUK
02-06-2019, 07:23 PM
Thanks Doddy,

1) That makes sense. I think I just have a pathological need to make sure everything is grounded as much as possible..!!

4) That's my plan - it looks like that connection is the only place on the VFD to earth it, so I may end up connecting that to both the spindle body via pin 4 and the mains gnd.

Not sure, haven't spec'd a contactor yet, but will look into it. At the moment I don't think I'm asking the UB1 to drive it directly? Its driven by the 24V PSU via the PNOZ.

Re Back EMF, from the VFD? If so I've added a question above about noise suppression above. I guess I'll also get back EMF in the 60V PSU, but was expecting the capacitor bank to help out with that, will that cause issues upstream?

Doddy
02-06-2019, 08:21 PM
Back emf: from the coil of the contactor/relay.

But I don’t know the particular UB1 output spec. If a mosfet might find it has a commutatinf diode built in, otherwise place a 1N4001 across the coil, cathode to 24v line, anode to ground

Nickhofen
03-06-2019, 07:44 PM
Does this answer one of your your questions about VFD?
http://www.mycncuk.com/threads/4985-VFD-Cable-and-2-2kw-spindle-wiring
About the last question i believe this can do the job :
https://www.aliexpress.com/item/32781939486.html?spm=a2g0s.9042311.0.0.27424c4d4Nk JmR

AndyUK
17-06-2019, 01:07 PM
Back emf: from the coil of the contactor/relay.

But I don’t know the particular UB1 output spec. If a mosfet might find it has a commutatinf diode built in, otherwise place a 1N4001 across the coil, cathode to 24v line, anode to ground

Perfect, Thanks


Does this answer one of your your questions about VFD?
http://www.mycncuk.com/threads/4985-VFD-Cable-and-2-2kw-spindle-wiring
About the last question i believe this can do the job :
https://www.aliexpress.com/item/32781939486.html?spm=a2g0s.9042311.0.0.27424c4d4Nk JmR


Cheers Nick!

Little more progress on the Z axis - managed to mill the channels required for the Z ballscrew yesterday. Bridgeport wasn't trammed perfectly, so the surface is a little off, (I was under quite strict time constraints and the tramming worm screw is broken - so its as good as I could get without it) but it will certainly do the job I need it to. Assembled the Z axis for a test-fit late last night, but forgot to take pictures, so they'll follow.

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My monster of an electrical cabinet has also arrived... 800x600x300 is massive, but should fit everything!! Went for the glazed door option, although unfortunately it has some dings in the door - I'm guessing its just a grey hammerite paint touchup job.

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I know I promised frame photos.... but I'm still halfway through painting the bed, and I'm not massively pleased with my 'smooth' hammerite finish. Despite our best efforts, the paint ran all over the place and whilst the surface is smooth, the light clearly reflects the brush strokes. :/ Any advice appreciated!

Nickhofen
17-06-2019, 01:54 PM
I use paint rollers to paint my bed,the painting is faster and easier to applied this way .
If you see lines this means that you have to thinner the paint , when the paint is thinner is leveled when applied, but be careful not to use too much thinner.

AndyUK
17-06-2019, 08:51 PM
Thanks Nick, what do you use to thin it? How much?

Test assembly of the Z axis with obligatory drill movement test (although I can rotate the screw by hand):
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Nickhofen
17-06-2019, 10:19 PM
You have to use the exact thinner type that the company suggest,about how much you will find it on the color container. I usually start with less thinner than the amount the company suggest,then try the thinned paint on a surface with the paint roller and let it seat for about ten minutes .
If it is not transparent and the color is leveled it self,I mean you do not see marks after ten minutes,you can do your job, with the roller you might notice small bubbles in the color,it is ok those are going to disappear when the color cures
If the paint is sticky add thinner, shake well before use!
Make one thick pass and do not repaint after some minutes or hours , because the new paint will dilute the old one and you will end up with a mess....
Good luck!

AndyUK
27-06-2019, 08:04 PM
Thanks Nick, the thinners and your advice has really helped. I've recoated it, and although it's still not removed the paint brush lines and the surface is nowhere near perfect, it's improved a lot. I think ultimately, I'll need to take the frame back to bare metal to fix this mess, but then again, it's just looks - the metal is protected as is, so I'm going to forge on regardless.

Also been cleaning up a few of the Z axis components now they're complete, ready for final assembly when I got the surface plate out.

In other news, put my slightly dented but massive cabinet up on the wall... Used a spirit level on the edges... The damn thing is a rombus!! The door is extra wonkey to boot... Serves me right for buying a cheaper cabinet I suppose...

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Next steps...

The current challenge on the base frame front is the epoxy framing and pour - I've sourced the MDF side pieces and cut to size, time to start gluing and siliconing!

On the gantry front, my next challenge is the motor mounts (thats the only thing, besides no belts, stopping me driving the Z and Y with motors).

And on the electronics front, I'm currently sourcing cables and components for the cabinet... its all go!

AndyUK
30-06-2019, 08:59 PM
Visited the science museum yesterday, saw this and it made me smile and think of you lot:

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But the smile has faded, because today, I've been tackling the demon that is E-P-O-X-Y. Unfortunately, I don't think its gone too well, but I'm going to let it do its thing for two weeks, then if needs be chip it off and start all over.

So, first off, I started by levelling the base frame on its levelling feet. Turns out my longest spirit level has an error in it, and I wasted a good half hour chasing the damn thing until I figured out it changed when rotated 180 degrees. Oops. Trusty digital spirit level to the rescue, which was much easier to flip round every time.

Once my lovely smooth and flat steel beam was level, I then set about mauling it with the grinder. The idea was to give the epoxy something better to stick on to.

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We then assembled the epoxy frame. This seemed to go really well - the only thing i'd change would be the width of those spacers you see over the top of the frame - it was quite a pain in the arse getting below them on the later stages. Take special note of the blue bottle we purchased to do the epoxy pour with - it has a tap on the other side which we thought would be ideal. We then started heating the garage up, got the air temp up to about 28 dungarees, and whilst we were doing this we taped the bottom edge of the epoxy frame, and then used silicone sealant all the way around on both the inside and outside faces (we really don't want any epoxy leaks). We also clamped the frame down onto the bed before doing this.

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After letting all that silicone set, and a bloody-good chineese takeaway, we set about the epoxying. We measured out and mixed the 1.3L in six equal sets by weight, taking a minute to thoroughly stir after each set. Naturally I got the wife to do this, as she is an expert stirrer.... When we got to the end, we did a two minute stir, then thought it would be a really good idea to let it sit for 10mins to let the bubbles rise out. It was going really really well - the bubbles were rising to the surface nicely, away from our little tap....

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Cue minute eight. The tub starts to look a little strange. Cries of "Oh Shit! The pots melting!!" come from the other side of the garage as the tub starts imploding and the epoxy level rapidly rises towards the rim of the bottle. Thankfully, we already had our gloves on and at the ready, so taking the very hot bottle, I swing it over to the frame and start the first pour by hammering on the tap's release button....

Of course, the damn thing had already jammed shut. At this point, theres nothing for it but to up-end the bottle and start pouring from the top. Bubbles are being created everywhere, and there are a lot of fumes being released into my unsuspecting garage. I think they were mostly melting plastic fumes... but they could also have been fumes from the rapidly curing quatermass.

Somehow, we managed to get the epoxy poured (taking shifts on who could hold their breath in the toxic air for the longest, the other running outside for some palatable air). I managed to go round 3/4 of the frame with a scribe and poke a few of the biggest bubbles before it became too gelled to continue, but most of them have left small craters. I'm quite sure the last 10cm or so hasn't been able to level before gelling.

Heres the good bit (that was poured first and attended to) - We then decided to coat everything but the bridge in clingfilm, so that nothing can fall into it, and then we retreated putting the mangled bottle in the emergency bucket.

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Videos of the final result to follow....

AndyUK
30-06-2019, 09:12 PM
https://youtu.be/2-7Gt-XMFd4

https://youtu.be/UW6zPT2v4nc

Scustom
04-07-2019, 06:18 PM
Hi Andy,already sent you a pm about what may happened,and here is the answer from west system site:https://www.westsystem.com/instruction-2/epoxy-basics/epoxy-chemistry/
Controlling Epoxy’s Cure Time

In warm conditions use a slower epoxy hardener, if possible. Mix smaller batches that can be used up quickly, or pour the epoxy mixture into a container with greater surface area (a roller pan, for example), thereby allowing exothermic heat to dissipate and extending open time. The sooner the mixture is transferred or applied (after thorough mixing), the more of the mixture’s useful open time will be available for coating, lay-up or assembly.

AndyUK
04-07-2019, 10:43 PM
Thanks to both Scustom and routercnc, think you have both nailed it, the combination of waiting for bubbles, and mixing in a tall narrow container allowed the exothermic reaction to spiral out of control.

I've got a new set of Epoxy on order, I've spent the evening clearing off the crap pour and the mountain of silicone, and will try again soon. Thankfully the frame hasn't suffered and can be used again with a fresh set of silicone. Expensive mistake but hey, we all screw stuff up every now and again!

This time, I'm going to make the amount in three mixes rather than 6, and in a wider tub. I'll then transfer to another jug with a taped up hole in the bottom, and immediately pour onto the rails.

Sent from my SM-G950F using Tapatalk

AndyUK
05-07-2019, 07:36 PM
Living near Southampton has some advantages - fast epoxy delivery!

Poured again tonight, and fingers crossed, I think we've nailed it.

We mixed in a very wide tub - an old decking screws container. Did the entire 1.3L in one go, adding 175g 105 and 50g alternatively, mixing a little inbetween. The mixup process took about 6.5mins start to finish, then did another final mix for 1.5min until no streaks were visible and the colour was entirely uniform. We then transferred to a 2L ice-cream tub which had two 8mm holes in the side at the bottom corner taped over (we measured the flow time of 0.5L of water through a 5mm hole, and decided it needed to be 8mm. Found about 20seconds for water through 8mm - so decided that should be a nice 1-2min pour of the epoxy which worked well. Second hole was a backup and never used.

The pour went really well - managed to time it so that the fizzy bubbles at the end of the tub landed in the centre of the bridge. Surface looks glassy smooth - had two 1-2mm bubbles on the main beams, but managed to easily pop them with a scribe. There are some very small <0.5mm bubbles in the epoxy itself throughout - but I'm not too worried about these as they're so small.

Weather looks good for the week, not dipping below 14 degrees, and the garage was 23 degrees when we poured. I haven't used any artificial heating yet - the plan is to poke the bridge section on Sunday, and if its still not gelled, we'll start heating then.

Thanks for the help everyone... fingers crossed!!

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AndyUK
08-08-2019, 05:23 PM
Lets talk cabinet layout for a moment or two.

I've just started a thread about tidy wiring (here (http://www.mycncuk.com/threads/12956-Tidy-Cabinet-Wiring?p=110025#post110025)) so I'm currently still deciding how to do my wiring channels (shown as green in the annotated diagram) as neatly as possible, but I think I've got a plan for the overall layout.

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As you can see, I've silently been buying more and more electronical bits (psst... please don't tell the wife how much this stuff costs...). My plan is to have the drives vertical in the bottom right with heatsinks facing each other, right by the inlet fan. The outlet fan will then be at the top of the case directly above the VFD (or possibly top left facing out sideways... which might be better from a water point of view if the roof were to leak (a real possibility in my garage...). My thinking here is that they'll have the most urgent cooling need in the cabinet, so they get the coldest air first. I'll probably put the two X drives at the top, as they'll be working the hardest and I don't want their heat transferring to the Y and Z drives - Who knows if that logic makes any sense or not? Maybe it should even be the other way around...

This position allows the driver outputs to get straight out through the GX20 connections on the base, and the input signals can come directly in from the right hand edge (as shown) of the UB1 where all the step and direction signals come from. The drive PSU is a little awkward here, but shouldn't be too far for the power to get to the drives from the right hand side of the PSU.

The GX16 connections (limit switches, homing switches etc) also come in at the bottom and can go straight up to the UB1.

My plan is for mains to come in bottom left, skirt behind or up the side of the PSU, and into the distribution/fuses area. From there each mains device will connect via individual EMF filters and relays/contactors/big on off switch as required.

Finally, theres a low voltage section up top. My plan for this is to have the safety / 24V circuits up here. This is where the control panel will interface - I have a selection of LED buttons for this, each with a specific function in mind, but I still haven't decided exactly where the panel will go (having a glass fronted cabinet is nice, but not so many options for things like buttons!).

Anyhow, I hope that either this post is helpful to others, or someone can point out any glaring problems or things I've not thought about! Update on the mechanicals soon - there is currently paint drying, and the garage has been even messier than usual in the last few weeks so I've not gotten around to photographing and writing up the most recent developments.

AndyUK
14-08-2019, 10:27 AM
I promised an update on the frame - here she is in all her badly painted glory!!

Since the last photos, I've

Faired the edge of the epoxy into the frame and repainted the box sections.
Filed off the meniscus along the edges and at the ends.
Marked drilled and tapped the epoxy for the rails.
Roughly aligned the rails for parallelism
Checked the levelling with a precision straight edge - more details below.
Thrown the gantry on the rails - it glides super smooth (and made me very happy!)
After getting happy about that, I then got very sad. Turns out my steel frame is a bit of a rhombus! When I bring the gantry to one edge, it hits the end of one rail about 3-5mm before the end of the other, and the opposite occurs at the other end. I don' t think this will actually affect anything, except perhaps my pride...
I then did some more milling, making my Z and Y nema 23 motor mounts. That was fun. :)
Did a rough assembly - All I need now to make the Z and Y axis move under their own power are the belts which are on order. It was nice to be able to measure the distances between pulley centres physically rather than just in CAD.


The rails both show the same trend, they're high at the ends and low in the middle with an error of about 0.05mm - I'm sure this could be better, the epoxy still set relatively quickly, so I'm sure there are improvements to make. It could be that I just haven't filed down the ends of the epoxy enough and they're slightly propped up at the ends, but its 'close enough' for me at this stage. The other consideration is that this value is the stated accuracy of my straight edge, so optimising it now seems counter productive. I will probably come back and shim the rails, but I'm keen to do a 'proof of concept' and am aiming to have the machine cut something by Christmas.

I've noticed that the Z axis isn't as smooth as the others; I think it might be the alignment of the ballscrew vs the rails, I've discovered that my design is a bit of a nightmare to try and measure the alignment between the two, because the rails and the screw are attached to different parts. The other thing it might be is that the Z axis is the only one thats had a load of EP2 applied - does that typically increase the resistance on the screw? I can turn the pully by hand no problem, but you can feel that it has more and less resistance at different ends of the travel, which is something I don't feel on the Y. Any hints or tips?

The other problem I'm now considering is how to check the axis are perpendicular... can anyone point me in the right direction? I think Boyan mentioned needing two precision squares to align properly... I can see why you'd need one, but two?

Thanks!

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Nickhofen
14-08-2019, 09:28 PM
If the diagonals of the x (long axis ) are equal, then the axis is orthogonal,start from this !
Then bring the Y axis at a point and measure with a square, that you know it is at true angle.
How you know that you square is really a square?
Check this video:
https://m.youtube.com/watch?v=gDh-E5xhm0o
If your square is not as it should ,do not through it away,check on YouTube how you can make it square again.
Good luck!
And remember any precision tool that is fall on the ground or it it is banged on something hard,stops to be a precise any more,it needs re calibration.

NordicCnc
15-08-2019, 12:20 PM
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Hello. Looks really good! Is there any benefit if looking a how rigid the machine is by having the gantry rails on top and at the bottom, compared to mounting both on the same side?

For example if we compare these 5 options, which one is the best for rigidity?


Both rails on the spindle motor side of the gantry, ballscrew in between rails.
Both rails on one spindle motor side of the gantry, ballscrew in between on the opposite side.
One rail on the spindle motor side side, ballscrew on the same side and the other rail on the top of the gantry.
One rail on the top, one at the bottom and the ballscrew on the opposite side of the spindle motor side.
One rail on the top, one at the bottom and the ballscrew on the same side as the spindle motor side.

AndyUK
15-08-2019, 12:33 PM
Both rails on the spindle motor side of the gantry, ballscrew in between rails.
Both rails on one spindle motor side of the gantry, ballscrew in between on the opposite side.
One rail on the spindle motor side side, ballscrew on the same side and the other rail on the top of the gantry.
One rail on the top, one at the bottom and the ballscrew on the opposite side of the spindle motor side.
One rail on the top, one at the bottom and the ballscrew on the same side as the spindle motor side.


See the Beginner Moving Gantry Design Thread (http://www.mycncuk.com/threads/9082-Beginner-Moving-Gantry-Build-Read-This%21)

NordicCnc
15-08-2019, 05:49 PM
Thanks for that link!

By the way do yiu have a youtube chabbel? I saw a very similar if not the exact same build. Joe Harris is the name of the channel.

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