AndyUK's Build - 1.2x1.0m Gantry

[routercnc]

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]

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?




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]

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.



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]

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]

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.


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.


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]

Okay, so its been approximately a year. I suppose I'd better post an update or two!

First things first, current drawings:






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]

And, just to prove I haven't been completely slacking off since last year - some progress photos!



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 :)



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!)



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...



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.



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!



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.



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.

[AndyUK]

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?

[JanBo]

Hi Andy. That's a very nice layout on your machine - it's certainly strong enough to handle aluminium. Grats on the build JanBo

[Zeeflyboy]

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.