GBX Update February 15 2022

Smart Apaga rHDPE

This past month, recycled rHDPE from the Armenian group Smart Apaga was tested in Gigabot X. The material was subjected to re:3D’s standard testing procedure outlined in re:3D’s Knowledge Base article Material Testing for Pellet Extrusion.

For extrusion testing, five trials of 200mm each were extruded with the extruder heated at 170/210/220C. The extrudate was then massed. The average mass of the five extrusion trials was 1.78g, with a standard deviation of 0.54g, which is very high. However, this material was able to extrude at temperatures ranging from 150C to 220C. Given the large range in possible extrusion temperatures, it was decided that further testing should be conducted to further optimize the temperatures, and the extrusion consistency trials should be redone at the optimized temperatures to arrive at the final extrusion consistency data.

Print optimization testing was then conducted, starting with a calibration cylinder. The material struggled with bed adhesion, so a bed adhesion test was performed. This involved applying various bed adhesives to the printer bed and printing a single rectangular layer to test multiple bed adhesives in a single print. The bed adhesives tested were PVA glue, Magigoo PP, Magigoo PPGF, Magigoo PC, and 3D Lac adhesive. None of the adhesives improved adhesion except for Magigoo PPGF, which did not increase adhesion enough to achieve a first layer. The material was then tested with polypropylene tape, which significantly improved bed adhesion. However, there were still signs of shrinking and warping, which caused the tape to peel up from the print bed. Furthermore, the inconsistent extrusion present during extrusion testing continued in the bed adhesion tests, resulting in inconsistency and gaps in the first layer lines. A calibration cylinder was attempted, and in addition to the above issues, the calibration cylinder walls shrank and collapsed inward, causing a print failure.

In summary, this material needs significant R&D work to achieve viable prints, including potential changes to the feedstock itself. The main roadblocks and potential solutions to printing with this material are:

  • Using a build surface or adhesive specific for HDPE to ensure reliable bed adhesion
  • Mitigating warping in the material by adding additives or fill material, such as fibers, to increase rigidity
  • Troubleshooting inconsistent extrusion


Bed adhesion trials of Smart Apaga rHDPE, printed on polypropylene tape.


Klipper for GBX

For some months now, our software engineer has been configuring our filament 3D printers to use Klipper, an open-source software alternative to Marlin. After building out the infrastructure and conducting many hours of testing with Klipper on the filament machines, this month we started configuring Klipper to work with Gigabot X. Klipper is currently installed on an in-house GBX, and configuration and testing is underway. 

Klipper has many benefits over Marlin:

  • Software configuration is separated and abstracted from the firmware code
  • Software is stored on a Raspberry Pi that processes gcode files, then sends signals to the printer’s board. This means that:
    • The board no longer has to store or process all the software configuration
    • Updating the software configuration is faster and easier, since it’s happening at the Raspberry Pi, and not the printer’s board.
  • Integration with Mainsail, and an open-source UI interface


In practice, Klipper’s software infrastructure enables the access to printers via computer over wifi. In a browser, a user can:

  • Upload and start prints
  • Preheat
  • Send movement commands
  • Execute custom macros, like purging
  • Send gcode via a command line
  • View the printer through a live webcam feed
  • See the configuration settings installed on the printer
  • Update Klipper configuration code from re:3D’s Github with the click of a button, making software maintenance easier and more continuous.


The UI in the browser can also be displayed on a touchscreen attached to the printer, or pulled up on a tablet to accommodate different workflows.


Mainsail UI on Desktop, configured for GBX.


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