AndyUK's Build - 1.2x1.0m Gantry

[Nr1madman]

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

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[Neale]

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]

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.

[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.

[AndyUK]

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...ubing-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.