hi all, I'm a small custom ski builder who's looking to begin a cnc project to assist in cutting and profiling of ski cores and ski bases. This involves cutting mainly hardwood, UHMWPE plastics and some MDF. Aluminum would be nice but not a necessity yet. My current idea is to use c beam to build an OX of 750 x 2500. The narrow width is due to limited shop space and, as I understand, may help to reduce torsion in the frame. I would either join longer pieces of 1500mm beam or possibly source longer stuff from china. The entire frame would also be mounted to a steel frame and legs and possibly supported by steel around the perimeter at the base of the frame. Z axis would also be c beam. Z axis travel would be in the range of 4-6". My question is can I use the regular parts list from the OX build to get started or are the gantry plates much different? I realize I'd need longer belts. I guess I'd need the c beam gantry plates as well. Are there other modifications I would need to make to make this work? Thank you! Vin
Hi Vin. Great to see your intention to delve into the CNC world. Firstly, it is very important to realise that, the longer any of the axis are, the greater chance and more likelihood, of flex and twist. This problem can be overcome, by strengthening and generally, seriously beefing up your machine. However, at just 750mm for your X Axis, I would recommend using CBeam for a good strong gantry. I think as long as you make sure the 2500mm "Y Axis" is securely fixed, strengthened and joined, you will be able to get away with such a long axis. Be careful with the "Z Axis", this is where you can get variations as the drill bit is pushed against the material. The further the tip is from the gantry, the pivot point, the greater the possibility of error. Just some points to ponder. Don't hesitate to get back to us, we're always ready to help. Gray
Thanks, yes I plan on anchoring and supporting the frame very well to prevent flex. I think I can get some 2.5m rails from china, so I'll probably go with those instead of tying to join 2 sections. So if I keep the z axis height to a minimum, in essence that should also minimize deflection at the cutter head??? Thank you. Do you think I can just use the ox plans and parts list with the c beam gantry plates?
You will need custom side plates to integrate a c-beam gantry with into the ox design. Have a chat with @Chris Laidlaw as he has made plenty of them. As for 2.5m long rails use caution when ordering Chinese knockoffs. If the tolerances aren't the same that will really mess with your wheel spacing so it's best to get your rails first and then verify against a standard section prior to ordering/making plates. Personally I would have no issue with butting 1 and 1.5 meter lengths. Just drill some dowels into the lengthwise holes in the extrusion for alignment and the connect rails with the Quad Tee Nut - MAKERLINK (10 Pack). To help deal with racking, run the 20x40 platform support rails crosswise and anchor them into the bottom 2 rows of the 20x80 side rails. 16" centers should be fine. It would also be a good idea to use double belts on the long axis to help deal with belt stretch.
Thank you! What if I use 2 sections of 20x60 v slot for the gantry rail, will that be stiff enough? The cross supports and double belts are a great tip thanks.
I haven't really thought about that yet. But something around 2 HP to cut hardwoods without bogging down too much.
Could I get away with a well supported OX build? 20x80 Y axis that is well supported with support rails within the frame and anchored to a sturdy frame? Do I even need the C-beam? I want this to be beefy but I also want this to be simple since this is my first CNC build and I have a lot to learn. how about 2500 x 750 (20x80 rails) 20x40 internal supports, 2 pieces of 20x60 or (20x80??) for the gantry, double belt set up. This anchored with L brackets to a steel table frame with a 3/4 plywood top.????
Overall sounds reasonable but I would still probably go with an 80mm deep gantry beam whether it be double 20x80s or a C-beam. As far as the router goes, don't expect this level of a system to push anything more than a 1 1/4HP trim router. These are hobby grade systems and while they do remarkable work, they aren't designed to power their way through anything.
1.25HP should be fine. I'm not looking for superfast on the hardwood cutting but I do want to be as accurate as I can. The ski base material is only 1.4mm thick and I'll probably end up with a drag knife for that after I add vacuum hold down. Will do on the double 20x80 gantry This is going to be my winter project, hoping to have it functional by April or May when I start building skis again.
Is the 1.4mm material hardwood? A drag knife just wont do it (foam it will), you can cut it with a router bit in two passes if wood.. Interesting project, can't wait to see what you do with it.
1.4 mm material is UHMWPE ski base. I'm considering a cnc routerparts machine. I'm concerned about the stiffness of this machine ....
