The Z-axis has seen a number of different efforts at improving it. The original Acme Z-axis upgrade for the first version of the machine is still documented here: ACME Z-axis (SO1).
The ShapeOko 2's improved Z-axis requires a slightly different upgrade, a kit for which is available for sale at shop.shapeoko.com (one could of course, fabricate one's own parts). It can be further upgraded to accommodate NEMA 23 motors:
Please note that Acme rod is available in several different grades intended for differing usages:
- rolled acme stock --- 0.009" per foot accuracy, 2G thread intended for power transmission
- milled or ground --- 0.003" per foot accuracy, 2C (centralizing) thread intended for precision positioning
Reasons for the Upgrade
Discussion in the forums: http://www.shapeoko.com/forum/viewtopic.php?f=7&t=2345#p17825
- 3D carving and speed-constrained on the Z (not as much of an issue if one can change the acceleration limit as on more sophisticated boards)
- Greater Z-axis accuracy (multi-layer PCBs w/ small traces)
- Greater strength and better support
- Being constrained at both ends allows one to spin the rod and move faster w/o whipping
Alternatives and discussion on the forums
There have been a couple of forum threads discussing other options and further improvements. One notable post argues that there is little point to a metal threaded anti-backlash setup.
- ACME Anti-backlash nut --- instructions on using a second nut to fashion an anti-backlash solution.
- Acme thread Z axis with a zero backlash nut
- Alternative Z-Axis Screw Replacement
- Yet another Z axis design --- uses a NEMA 17 motor from RobotDigg w/ an Acme threaded rod for a shaft.
- Re: DEWALT DWP611 --- 1 x 9" 3/8-12 ACME Lead Screw w/Delrin Nut
- Makerwill's build log --- a Shapeoko using a motor w/ an integrated Acme screw for its shaft. See also GT2 pulley and belt --- Announcement of site selling Threaded Rod NEMA17, 280mm Tr8*8mm which should work for the Z-axis, eliminating the coupler and motor stand-off.
- Forum user ejs decided on directly addressing the Z-axis nut in A new Z-axis nut - metal on metal w/ built in anti-backlash. Simpler shape: http://www.amazon.co.uk/Miniature-Lead-Screw-Anti-Backlash-Delrin/dp/B00I5UYB98
- Lee's Shapeoko 2 --- iquizzle used linear rail instead.
- New Z-Axis (Non Milled Acme rod with AntiBacklash Nut)
- Re: Nema23 on Z-Axis --- proposed design using TR10x2 leadscrew and a pulley system which shifts the motor back over the gantry for better balance.
- Shapeoko 2 geared z-axis design --- requires a 3D printer and the ability to mill aluminum.
- Z-Axis Upgrade --- extended Z-axis.
- Youtube: Simple anti-backlash nut
Of especial note is the idea of either canting the nut, or modifying it as discussed here.
Thermoforming a plastic nut
This is done fairly easily using basic tools. The Home Shop Machinist and The Machinist's Workshop Magazines forums: Making Acetal leadscrew nuts the easy way