CAD CUT x-axis

[bsmith]

It says on the CAD CUT website that it uses dual x-axis drives. I assume this means one motor driving two rack and pinion gears. In any case, my question is can this arrangement ever cause racking or binding problems due to slight differences in alignment, tolerances, backlash etc, in the racks on each side? If not initially, could these problems build up over time so that it would require re-aligning? If a single motor is used, is the connecting drive shaft strong enough to avoid any twisting/warping in the shaft itself that could also create binding problems?

It seems like the idea may be preferable over a drive on just one side, but I am curious about the issues raised above...

[HuFlungDung]

Which site is this exactly?

To me, dual X axis drives means two servos running in a master/slave relationship. These might run two ballscrews, or two rack and pinion assemblies. If there are any good pics on the site, maybe this could be determined.

You are correct, there would be far too much "windup" in a long shaft with a couple of pinions mounted on the ends, unless a relatively massive shaft or tube were used to connect the pinions. However, if such a massive pinion shaft were built, I don't suppose there would be a whole lot of reason why they would get out of phase with one another.

[bsmith]

It's the CAD-CUT site at http://www.inshorepowerboats.com/cnc.../CNCROUTER.htm

It's hard to tell if two servos are being used in the system -- if so, it's possible they are mounted inside the middle of the gantry.

When using two servos in master/slave, is a system still susceptible to racking due to slight offsets, backlashing, and motor/screw tolerances, causing creeping over time? It may be moot -- practically, this probably doesn't occur.

One idea when using dual x-axes would be to allow one of the motors to be a lot less powerfull and purposely slip to prevent binding on that side. The lower power on that side would be there just to help the gantry along and reduce torsional forces. (This could perhaps be called a 'limited slip differential' though that would be a misnomer since it's nothing like the differential mechanics in a car). Purely speculative -- this could be a really bad idea.

A compensated or non-compensated dual x-axes design may in fact be the preferred method of some of the large CNC manufacturers -- I don't know enough about CNCs to determine that. I did notice that dual drive x-axes are used on one of the high-end Multicams. I also want to share that as far as build-your-own CNCs go, the CAD CUT design does look pretty remarkable.

[ninewgt]

The machine uses a single stepper on a shaft driving 2 pinion gears. You could build it and use 2 motors no problem if you prefer. I have had no problem at all with the single motor arrangement though and have cut a lot of parts with excellent results.


" I also want to share that as far as build-your-own CNCs go, the CAD CUT design does look pretty remarkable".

Thank you - I tried really hard to make it a good machine as well as easy to build...........

Tom