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GBX Update May 19 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:

 

New Hopper and Hopper Lid Designs

We recommend dehydrating any hygroscopic plastics to below 0.02% moisture content to improve print quality. To help prevent pellets in the hopper from rehydrating from ambient moisture in the air, we updated the hopper and hopper lid designs. The lid now includes a flexible Cheetah ring that seals against the hopper when tightened. Other updates to the design include:

  • Stronger base and supports to prevent breaking
  • Larger internal capacity to accommodate GBX’s increased max extrusion rate of 0.5kg/hour
  • Improved attachment to the feed tube to improve material flow from the hopper into the feed tube

 

New Feed Throat Design

We have been working on an improved feed throat in an effort to improve material feeding into the extruder, especially for irregularly-size recycled plastic flake. The new feed throat has larger internal geometry to improve the flow of flake through the part. The design is still undergoing testing, and it will be validated in the Austin office, where Brian is printing with polycarbonate flake from recycled ID cards.

Recycled Polycarbonate Flake Printing

As part of our efforts to 3D print with recycled plastic, Brian is exploring printing with polycarbonate flake from recycled ID cards from HID Global, a company headquartered in Austin, TX. This serves as a pilot to assess GBX’s ability to print with Austin’s municipal waste.

Feeding the irregularly-sized flake into the screw is difficult, and results in extrusion inconsistency. Brian has a few methods to improve material flow:

  • A new feed throat design: experimental designs with larger internal geometry and a higher incline help prevent the flake from packing and clogging in the feed throat.
  • A vibration motor: the motor improves flow, but not enough. Investigation is needed into more a powerful vibration motor, and where that vibration motor should mount to the extruder.
  • Mixing with virgin pellets: Mixing virgin pellets with the polycarbonate recycled flake may improve material flow.

 

Granulator Design

We have continued to work on our desktop granulator design. This month we designed a collection hopper, sourced materials for the granulator screen, and conducted calculations to spec the motor at 0.5 hp. 

New GBX Extruder Cover

Aubrey has updated the GBX Extruder Cover to complement the new versions of the motor spacer and the feed throat.

 

New Feed Tube 

As we gain more experience with larger GBX platforms like XLT GBX and Terabot X, we realized that the longer feed tube slumps from the weight of pellets during printing, causing pockets where pellet flow to the extruder stops. To address this, we’re exploring different feed tubes that are more stiff, and less likely to bend and stop the flow of pellets. We recently ordered a stiff feed tube, with wires that prevent static buildup in the feed tube. Stay tuned for testing results!

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