Bertha

[SimonC]

Hello everyone!

So, I'm hopefully about to embark on the adventure of building my own CNC router :-)

I've tried to pick up as many tips as I can from the various build logs. Thanks to everyone who's posted info in them - reading them was very very useful! I hope I've arrived at some sensible design decisions but if anyone can spot anything that could be improved upon please do let me know - I'd very much appreciate your thoughts.

Spec :
The machine will be predominantly used for hardwood. If it cuts ally then great but my priority is getting a good finish on wood first and foremost. The working volume I'm aiming for is 1220mm x 610mm x 220mm.

Frame :
60mm x 60mm x 4mm steel box section, welded. Am thinking I'll use self levelling Epoxy on top before mounting the rails. I was considering making some 'bridges' across the structure which will be removed afterwards in order to level both sides up in the same pour. There will be a movable bed, as I doubt I'll make use of the full z travel very often - most of the time it'll be less than 100mm.

Gantry :
I've tried to take on board the comments people have made about getting the distances between the axis, linear bearings, ballscrews etc. as close as possible. For the Y, I'm thinking of a C shape made from extrusion, with the screw the 'right' side (I'll use bellows to keep the chips out).

Linear gear :
SBR20 supported round rail on all axis. RM1610 ballscrews driven by belts all round. X will be two screws driven by a single stepper. I'm thinking the Nema 23 3.1NM motors that everyone seems to recommend.

In my attached pics, green is 60mmx60mmx4mm box section steel, red is 90mmx45mm alu extrusion, orange is 60mmx30mm alu extrusion, blue is 20mm alu plate.

Would be great to get some feedback - thanks very much in advance!

Cheers, Si