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GBX Update August 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:

 

Gigabot X QuickStart Guide

This past month, we published our Gigabot X Quick Start Guide to help new users set up their GBX and get started with the first print. The guide is available for download at our website here

The plan is to use the Quick Start Guide as a foundation to expand into a Gigabot X User Manual. And as always, there are also many helpful articles about GBX in our Knowledge Base, 

 

Crammer Development

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.

I tested the Crammer with TPU pellets that didn’t flow well into the pellet extruder, which resulted in frequent underextrusion. I successfully designed and tested rev7 of the crammer with TPU pellets, and I was able to get significant extrusion and print with them.

 

Tensile Bars from rPET Water Bottle Flake

After confirming the crammer’s success with TPU pellets, I tried to use it with rPET water bottle flake. For over a year I have struggled to print with water bottle flake, which is a main goal of our NSF Phase II grant to develop GBX. There is huge importance and opportunity around recycling PET water bottles due their prevalence around the world, their single-use consumption, and PET’s recyclability as a polymer. There is also motivation to find a water bottle recycling solution for Puerto Rico, where water bottles were brought into the island for disaster relief after Hurricane Maria, and contributed to the shortage of landfill space on the island. re:3D has an outpost in Puerto Rico, and re:3D’s printers were used to print useful objects for the community during the immediate aftermath of the hurricane. 3D printing with recycled water bottles ties into long-term efforts not only to recover from Hurricane Maria, but also to build Puerto Rico’s resilience against future hurricanes.

When printing with rPET flake using the Crammer rev7, the crammer would successfully convey the flake for a few minutes before the motor began skipping, and the screw stopped turning. Closer inspection revealed that water bottle flake was getting caught between the screw and the internal walls of the feed throat, stalling the Crammer motor and preventing conveyance. Since higher tolerance between the parts could not be achieved with 3D printing, an alternative screw was designed (rev8) that left space between the screw threads and the feed throat internal walls, allowing flake to pass between the screw flighting without getting stuck.

With the Crammer, the water bottle flake could be extruded enough to produce ASTM D638 Type I tensile bars with a 0.8mm nozzle. We are currently collecting tensile test data and other material properties for publishing in an upcoming paper. In conclusion, we've made a huge step toward 3D printing with PET water bottle flake!

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