PrintrBot Simple Metal Metric Z Conversion

thingiverse

With the PrintrBot Simple Metal approaching end of life, I've been thinking ahead in terms of replacement parts. Most of the parts on the PrintrBot are fairly generic or can at least be (relatively) easily swapped out with industry standard components, but one part that really worried me was the Delrin Z nut. This is one of the only parts on the printer that is both proprietary and consumable; eventually the nut will wear down and will need to be replaced. Rather than buying a bunch of them to stock up for the future (though at the time of this writing, they are no longer available on the PrintrBot store anyway), I decided to replace the Z movement with a standard 8 mm lead screw that can easily be sourced online for a few dollars. Beyond maintenance and availability issues, converting the PrintrBot's Z motion to metric can (in theory) improve print quality as the controller doesn't have to convert the metric dimensions of the printed part to the PrintrBot's original imperial threaded rod. For source and more detailed documentation, please see the GitHub page for this project: https://github.com/MS3FGX/PBSM_ZNUT Required Parts Installation requires the following additional components: M3X15mm Cap Screws (x2) M3 Nut (x1) Brass T8 nut 250mm T8 Lead Screw 5mmx8mm Coupler (Either printed or purchased) Installation After printing the adapter, press the M3 nut into the bottom and then use the two M3 screws to secure the brass Z nut to the top. Once you're sure the brass Z nut fits into the adapter, you can remove the PrintrBot's Y arm, Y belt, and Y stepper. You can then remove the two white spacers, Delrin Z nut, 5mm threaded rod, and Z coupling. They will no longer be required, but I would keep them to be safe. Install the adapter and Z nut in place of the original parts, then thread the lead screw through the top of the brass Z nut and down into the new Z coupling. Finally, put the Y stepper and belt back on, making sure that the belt isn't rubbing on the aluminum bearing block (you may need to move the sprocket slightly on the shaft). Also check the belt tightness before putting the Y arm back on. Firmware With the new lead screw installed, you'll need to adjust the printer's firmware so that the steps-per-mm matches the new thread. You can use the very handy RepRap Calculator, but assuming you got a standard 4 start T8 lead screw the steps will need to be set to 400. To do that, you'll need to connect to the printer with your software of choice and execute the M92 code in the GCode input field. You'll then need to save it to the EEPROM with M500.