AndyUK's Build - 1.2x1.0m Gantry

[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

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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!