ACME Z-axis

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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 (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:

  • 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[1].

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