CNC4Newbie Z Axis - repairs


(mikep) #1

I find myself needing to replace the anti-backlash assembly in a cnc4newbie z axis. The plastic anti-backlash in this is junk. I’d replace the whole thing with the HDZ axis, but just not in the cards at the moment.

Anyone replaced the anti-backlash with one from off-the-shelf?
Anyone replaced the acme leadscrew with a ballscrew?


(William Adams) #2

There were some designs for this sort of thing for the SO1 which might be applicable:

https://wiki.shapeoko.com/index.php/ACME_Z-axis#Alternatives_and_discussion_on_the_forums

esp. https://forum.shapeoko.com/viewtopic.php?f=11&t=751 and https://forum.shapeoko.com/viewtopic.php?f=11&t=1720&p=12964


(Phil Thien) #3

What kind of anti-backlash nut are they using, have a pic?


(mikep) #4

I don’t have a picture (should have taken one when it was apart).
brass tube, an acetal nut on the bottom (with two screws clamping, not through it) attached to the clamp carrier assembly. Inside the tube is a spring, then another nut with wings keeping it from turning in the tube. It looks from the outside like a ballscrew nut, but it’s not.

These are representative parts below. I think the upper nut is correct, the lower in mine has a tube assembly, not just a aluminum plate, but it’s shown here the same way it’s attached to the carrier - “Pinched” by a couple screws clamping on the plastic.

Problem: Although the carriage can move up and down without observed backlash, if you grab the carriage, it doesn’t take much force to move it up and down ~ 2mm - looking closely, the threaded rod is moving up and down in the lower nut indicating that it’s either worn out, or has extraordinarily loose threads.

The machine has less that 20 hours on it with this Z, so to wear out that quickly seems ridiculous, and they basically want $30 for the acetal lower nut. You can buy a common all brass 8mm leadscrew nut for <$10.

IMG_6823%20Cropped-400x400IMG_0143-400x400


(Phil Thien) #5

Would there be enough room to get one of the anti-backlash nuts from Dumpstercnc.com retrofitted to the axis?

http://www.dumpstercnc.com/


(mikep) #6

Good source, didn’t know about them. Doesn’t look like they have something that fits though, I believe the existing leadscrew is 8mm trapezoidal.


(Phil Thien) #7

There are quite a few 8mm anti-backlash trapezoid nuts on eBay, like this one. Can you find what you have there or something better there?


(mikep) #8

Yes, I found a set of these, which I’ll give a try.