GBX Update July 21 2020

Hi everyone! I hope everyone is continuing to stay safe given the pandemic. In the meantime, below are the GBX R&D updates from the past month:


Printing with Recycled Polycarbonate Regrind

At re:3D’s Houston factory, we have a print farm of around two dozen printers that is always printing production parts, contract prints, and R&D projects. That also means we generate a lot of rafts, supports, and failed prints. We collect this plastic and put it into our granulator to make regrind to put into GBX!


Recently I’ve printed a lot of test prints out of Polymaker polycarbonate regrind from this in-house waste stream. I previously printed a NIST artifact from the rPC with a 0.8mm nozzle:

This month, I experimented with printing with a 0.4mm. Unfortunately, I have no pictures because each print would start off great before extrusion would suddenly stop. Increasing the nozzle temperature didn’t help. After removing the nozzle and purging several times, I concluded that there is probably some kind of contaminant in our rPC regrind that periodically clogs the 0.4mm nozzle.

I moved on to a 0.8mm nozzle. To push the resolution as high as possible, I set the layer height to 0.3175mm. This time, I had no extrusion issues, and was able to print a Moai:

In summary, printing with rPC on GBX is very promising >.>


Gigabot X Quick Start Guide

Based on feedback from early GBX customers, we’ve been working on creating a Gigabot X Quick Start Guide to help new users get started with their first print. The plan is to use the Quick Start Guide as a foundation to expand into a Gigabot X User Manual.

The Quick Start Guide will be published to our knowledge base in the next few days, and will be accessible here: https://re3d.zendesk.com/hc/en-us/categories/360002506231-GIGABOT-BASICS


Continued Work on the Crammer

In last month’s update, I described how as part of our efforts for printing with recycled materials, we’re developing what we call a crammer to improve the printability of non-uniform particles. The crammer is a modified 3D printed feed throat with a motorized auger that physically pushes particles into the GBX extruder.

Since last month, I have tested and verified firmware to use Marlin’s ditto printing feature (DUAL_NOZZLE_DUPLICATION_MODE) to rotate the crammer motor when the pellet extruder motor turns. To control the motors’ relative esteps, I altered the microsteps of the crammer motor by adding/removing jumpers from the electrical board. Unfortunately I have not figured out a software solution for this. The crammer motor esteps cannot be controlled via slicer because the ditto movement is copied on the firmware side, and ignores any slicer settings I tried (M92 gcode commands, extrusion multiplier, filament diameter). A software solution will involve something in the firmware.

I also CADed a few iterations of the crammer feed throat, screw, and a motor mounting plate. Most of the design changes were to improve the internal geometry of the feed throat, and to increase the space in the screw flighting to more effectively convey printing material.

When I tested rev5 of the crammer feed throat with one of our TPU regrind materials, it quickly seized up, and the motor did not have enough torque to turn the screw. Therefore, I redesigned both the feed throat and the screw to further reduce the space between them where plastic can get caught.

Rev6 is currently printing, and I’ll test it tomorrow!


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