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Looking for advise on frame modification


i had my neighbor make an alloy frame for me based on a frame plan i did find here on the maslow cnc forum. Unluckily the top bar is leveled with the base of the waste board so the chains are not parallel to the work space. And i do have a linkage setup which i cant really level. This means i need to move the motors away from the frame.

The top bar is 12" by 3.5cm X 3.5cm and rests on 2 x 3.5cmx3.5 bars and 2 x 2.5cm x 2.5cm bars.

I want to move the motors about 12-15cm away from the work-space base and would like to ask how to best do this as i am not a metal worker. (There is no unistrut or similar available in the area i live, btw.)

the best way is to get another 12’ top beam (or cut the one you have away from the frame) and build some brackets that let you space it out from the frame.

it would be better to mount the motors so the bracket is on the sprocket side rather than the back side.

the problem with the way you have it and adding any spacers at the end of your beam is that it gives the chains more leverage to flex the frame and mounts

I did already check the available materials here and its, unluckily quite limited. There are no beams which are larger than 3.5x3.5cm. So that would mean i would need to weld 3-5 topbeams together to get motors at least 12cm above the workspace base.

And yes, attaching the motors on top is better. But i need to change the 3D Printed chain guide for this. Which now is less of a problem because i have a 3D printer now. Luckily.

Do you think its possible to 3D print a motor mount which “wraps” around the top-beam using carbon enhanced filament (NOT PLA) or polycarbonate based filament? Preferably an adjustable one?

you don’t need solid metal, so you wouldn’t need 3-5 top beams. just one top
beam pushed out. The stock frame supports the top beam in just two locations, so
you would only need two supports.

the motors don’t need to be at the top of the beam (that’s just an optimization
to make the machine a few inches shorter), but they should not be in front of
the beam. In an ideal world, the chain would be centered on the beam so it’s not
putting any forward bending force on the beam, but since that’s not very
practical, we generally have it so the chain just clears the beam.

you can make them from wood, or metal, with the standoff at a right angle to the
top beam. you don’t need something as fancy as carbon enhanced filament. You
just want something that will support the weight of the top beam.

if you were to cut the top beam off your machine and then weld a 1’ length of
square tube across the top of the frame and the top of the top beam, you would
have a great support. If instead of welding it to the top beam you cut a slot
(or series of holes in it) so that you can mount the top beam out at different
distances from the frame, you now have it adjustable

David Lang