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

[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!!!!

[JAZZCNC]

Ok well it's plenty strong enough but I would use 2 x ballscrews on the Gantry with this wide Y axis design to stop any racking affect but connect with timing belts using one motor.
I would use 20mm diameter and 20mm pitch screws at this length with a ratio applied. This will give more torque allow lower screw speed and still maintain decent rapid speeds.
Regards the motors then be aware that large nema 34 motors spin slower and require high power drives. So for this reason I'd go with 6Nm or no more than 8Nm motors as they will spinn slightly faster but still will require high power drives to get the best from them.

20mm linear rails will be more than enough.

With this wide gantry design you make it more stable/stiff but your making life hard regards the Z axis and you'll need to work on this area because that simple frame won't be enough. To be honest I'm not a Fan of this style of gantry design because it makes life harder than really needs to be and for not much more gain really. If your just cutting wood then you need to ask your self do you really need this complexity and my answer would be No.
Also to take advantage of the extra stiffness the gantry allows you need to have a powerful spindle so again not much point if your just using a plane old router or 2.2Kw spindle as a conventional gantry design built strong will be more than good enough.!!