Easy to turn Z-axis Knobs

I found the Z-axis knobs a bit hard to turn and hard to make fine adjustments, so I created new 3D printed knob overlays. I first tried some of the ones on Thingiverse (for other printers), but they either didn't fit or had a lot of sharp corners. I designed these new knobs to fit over the existing metal z-axis knobs, without any sharp edges. Likely any material will work, but I used black PETG, with a raft at normal quality. It took about 45 minutes for each knob.

Once printed, remove all four z-axis metal knobs from the bed, and press fit them into the printed knobs. For me (after a few test prints) a 12mm diameter hole worked perfectly (and actually printed at about 11.8mm). A real 12mm would be too loose.

For me the tie-wrap that holds the bed power cable was in the way of one knob. Easy to replace with a new tie-wrap with the big end of the tie wrap above the bed bottom.

I attached the knobs and used a tiny washer between the metal bed and the metal knob to make it even easier to turn. The washers are not necessary - they just happen to be handy.

These knobs will extend down about 2-3mm more, so depending on how low your printer bed goes, you may need to make a small adjustment. I found a small metal barrel that I added to the limit screw to stop the bed at the bottom about 5mm higher. I used a drop of loctite on the threads. An alternative is to get a longer screw (45mm), but I confirmed the existing screw is at the end of the range - it is not adjustable. This means you lose a tiny bit of build volume, but isn't an issue for me.

Once the new knobs are installed, be sure to go in use the Z-Offset wizard and and the Bed Calibration. I found the manual bed calibration to be the easiest.

Attached are two stl files - the first is a very small test washer (i.e. fast print) that can be used to test that the diameter is correct and presses into the metal knobs. It's not really necessary. The second stl file is the knob.

Now the reality is the z-axis rarely need adjusting once set, but it does make the adjustments easier and gives you finer control as they can be set more precisely than the smaller metal knobs alone.

 

Minor update - if you have a newer R2, the bed heater cable is routed differently, and shouldn't need any tie wrap change.