Advice on Mammoth CNC Router Build - Steel Framed - 2440mm x 1220mm cutting area!

[Neale]

How are you planning to allow fine adjustment of bearing/ballscrew nut position? This isn't a criticism of your design but I'm working on exactly the same issue on my own design! I'm assuming I can build a structure to within a millimetre or two, but will need to permit tweaking to get exact alignment afterwards. I can't see how you can move the bearings, for example, in both dimensions, unless you plan to use shims?

[Wejjmeister]

For the top rails, I will use the epoxy method, both on the x and y. For the ballscrews and blocks it will be shimmed to suit, hopefully that will be sufficient?! Im a newbie though too so looking for advice throughout the process just to keep me on track!

[gavztheouch]

Looking pretty nice. I would love to build something like this dedicated to profilling plywood. 8*4 sheets

Do you have a rough idea of the material and parts cost?

[Wejjmeister]

Thanks. So far the budget is around 5k but Im expecting it to be a little over as I am unable to machine some of the parts in house. Doh!! You could cut costs in some areas though as this is also designed for Aluminium sheets, if you just wanted to do ply, you could save a little I would think?

[gavztheouch]

Why do you need the bearing blocks to hold the ballscrews if you are using a rotating nut.

[Wejjmeister]

Why do you need the bearing blocks to hold the ballscrews if you are using a rotating nut.

I will fix them, they are just for reference to begin with to get the spacing etc correct. Couldnt find a skp file for anything else to be honest!

[Wejjmeister]

Can anyone just say yay or nay to the frame as I would like to make a start soon?

[JAZZCNC]

Can anyone just say yay or nay to the frame as I would like to make a start soon?

Frame looks fine to me and if anything it's over engineered in places and under in other. By this I mean you don't need that much diagonal bracing near the floor but it would benifit from more diagonal braces on the sides and ends/cross sections..
If you don't plan to put on feet then I would also lift the lower horizontal beams up a few inches to help with levelling. Just the stubs of the vertical members will be better and easier.

Other than that then it looks fine and will be plenty strong.

[Wejjmeister]

Frame looks fine to me and if anything it's over engineered in places and under in other. By this I mean you don't need that much diagonal bracing near the floor but it would benifit from more diagonal braces on the sides and ends/cross sections..
If you don't plan to put on feet then I would also lift the lower horizontal beams up a few inches to help with levelling. Just the stubs of the vertical members will be better and easier.

Other than that then it looks fine and will be plenty strong.

Thanks Jazz, I can add some bolt in diagonals on the top if necessary after the majority is built, there will be feet too on the bottom to level it all up so got that covered. Thanks for the green light though, very much appreciated!

[Wejjmeister]

Right so I have now officially ordered the Steel for the frame, I have gone with a local company, they've agreed a good price and to cut to a decent tolerance level so I'm happy. The bed Will be tweaked slightly as I've never been happy with it, but the frame is the same.

Questions for those in the know:

1. Does this look to be strong enough guys? The ball-screw will be driven by a pulley on the end so that the pitch can be played around with.
2. I'm not sure where to mount the motor though?
3. Will 20mm profiled rails be sufficient?
4. What kind of motor should I use, as I specced all Nema 34 12.1N's throughout so far but do I really need these on this axis?



The gantry is a nightmare, I am trying to keep everything close together to keep it strong, whilst using the space well too and trying to save on machining costs etc, if you have any thoughts so far, please let me know as I am dreaming in CAD lately and my thoughts are all over the place!!!!