Z axis Lead Screw

Any reason to not use a lead screw for the Z axis instead of the all thread?
Can it be used? Using this only for CNC work, with a 3" workable Z axis height.

Not a fan of allthread for things like these, just wondering is the lead screw is compatible with the design, or if anyone created a upgraded part that needs to be printed to use the lead screw.

Should be no issue, lead screw is probably the better choice. Just need to know your lead screws specs so you can accurately set your steps per mm.

The only downside I see is the 3D printer cheap leadscrews have a soft brass nut that might wear very quickly with the weight of a big tool on it, and they have a lot of slop that might affect your z dimensions. This cheap screws are design with light 3d printer gantries on them and only loaded in the direction of gravity. A cnc can experience loads opposite of this and you could have z variances of 1mm or more depending on bit selection, wear on the nut, material being cut. Think about a downcut through plastic. This might actually push the tool up, were regular bits pull the tool down.

I have not done the math on loss or gain of z axis torque either.

I’ll stick with the all thread then. You’ve been playing with this design for long enough, and haven’t had any issues with the all thread setup.

The only downside I see is the 3D printer cheap leadscrews have a soft brass nut that might wear very quickly with the weight of a big tool on it, and they have a lot of slop that might affect your z dimensions. This cheap screws are design with light 3d printer gantries on them and only loaded in the direction of gravity. A cnc can experience loads opposite of this and you could have z variances of 1mm or more depending on bit selection, wear on the nut, material being cut. Think about a downcut through plastic. This might actually push the tool up, were regular bits pull the tool down.

I’m using this one on my prusa i3 http://www.ebay.com/itm/322101010139. The anti-backlash nut was much larger than any of the parts I found on thingiverse so I had to design my own but I’m pretty happy with them. 2mm per turn still gives me plenty of resolution.

Does the anti-backlash feature resolve the slop or backlash problems you described? What would be a suitable alternative to the brass anti-backlash nut?

That Should solve it, those are pretty nice. Now the question is will the brass actually wear down quickly or not. That would be pretty cool if they held up. That anti backlash puts a lot more surface area on the threads. That might work pretty well. Good find.

It can work great on 3D printer but will not for milling or engraving. The spindle/Z axis assembly must be as solid as possible and the backlash should be compensated by software, not hardware. The load on spring on this nut is 4-8N - it will compress at a very little load and the end mill will flutter under different loads (cut depth, side load, RPM speed, feed rate etc.) and break easy.
Just my 2c and a little bit of full size CNC machining experience.

So we need a stiffer spring Paul? How is the preload set? I’ll work on designing a new C-Z-Lower part. Hopefully I have the clearance and can still utilize the bearing above the anti-backlash nut.

Guess I need to mod the nutlock part, not the C-Z Lower

Have you tried the recommended way yet? I’m not sure if all that will fit and I’m not sure if it will improve anything but z axis speed.

I’m still printing but hopefully I’ll get it built soon. Have about half the parts done.