Printrbot Simple Metal Z-Axis M5 0.8mm Pitch Threaded Rod Upgrade

thingiverse

So this is a mash up between two different Thingiverse listings: https://www.thingiverse.com/thing:96737 and https://www.thingiverse.com/thing:2011148. When I saw the first one, I thought it was nice but then I needed a specific metric Z-rod and a threaded collar that could only be bought from a hardware store at premium prices. I saw a complaint on the Printrbot site about their metric Z-upgrade, which said the Z-axis would fall down if you didn't constantly power the motor to stop it, so I thought that wasn't a good upgrade. Thirdly, I intended to increase my z-volume to around 300mm if possible (not sure it could handle that height but I'll try anyway). Then I saw this thing for the original Printrbot simple: https://www.thingiverse.com/thing:96737. This seemed like the better option! It had a precision thread, specifically M5 0.8mm pitch, which was available from most decent hardware stores! They sold it by the meter for half the price you'd pay for a 200mm metric Z-rod, and with the fine pitch, it stayed put! So I proceeded to draw an adaptor based on thing 2011148. I made a square adaptor that took two brass nuts; they press fit from the side that mounts against the plate (turns out two require more force than the Printrboard can deliver, so I threw one out and only use one). I made no provision for a backlash spring or such because I don't think it's necessary since the thread has the weight of the Z-axis on it. Watch the assembly (I left no hole on the adaptor to facilitate tightening the grub screw on the GT2 belt pulley for the Y-axis motor). So before inserting the threaded rod, test fit the adaptor and the motor. Add the pulley, mark where it needs to be then remove the motor, tighten the pulley in place, add some loctite to the grub screws and then assemble the Y-axis. Insert the threaded rod last (if you don't, you won't get the pulley past the threaded rod and won't be able to seat the motor correctly!). You'll need to adjust the printer's firmware so that the steps-per-mm matches the new thread. To do this, connect to the printer with your software of choice. In the GCode input field type M501 (this will read all your printers eeprom settings). Copy and paste this to a notepad or wordpad page for safe keeping. Now type M92 Z4000 (the new value for the replaced z-rod) after that type M500. Finally, type M501 to read it back and check that the M92 command is now reading Z4000. After that, it should be ready to print. This does work; it's a significantly worthwhile upgrade! My extruder nozzle no longer crashes into previously printed layers, and there's no banding in the z-axis even at a resolution of 0.2mm. Consult both things I listed here for additional setup info. If you modify the adaptor, share your mods here on Thingiverse. Enjoy!