WASP PET-G HELL — GUY ERIK GARDNER

This is the saga of the 3D printer pellets from hell. It all started when I suggested we try to use our WASP large format printer to print the lamps for Mauricio Soto-Rubio’s design-build project using recycled PET-G, the kind of plastic used in drinking bottles. I had seen some interesting results that people had achieved using the material and heard good things about its durability and printing properties. Prior to this we have been printing with PLA - a type of biodegradable plastic made from plant starches.

We ordered a large enough quantity of the material from our supplier and WASP North American Distributor https://www.picosolutions.com/ to print the lamps. As soon as I loaded the printer, problems started. The machine started under-extruding and seemed clogged. I contacted Pico’s tech support, they walked me through disassembling, cleaning and reassembling the machine, loading the right settings into the slicing software, Cura, and trying another print. The same thing happened, with the same recommendations.

After cleaning and then reassembling, I began to preheat the printer when I noticed that the temperature reading on the controller was rising rapidly. As I shut the machine off it had climbed above 275, and smoke began to rise from the extruder nozzle as plastic bubbled inside.

The thermistor and control unit were damaged by a power surge possibly resulting from plastic being drawn up above the extrusion chamber during retraction

The screen of the controller was a series of white bars when I turned it on. I contacted Pico, who contacted WASP, who informed us that the motherboard was likely fried, and the extruder would have to be inspected and potentially replaced.

So that is what we did. In the meantime, Mauricio’s lamps still needed to be printed. So we redesigned and created toolpaths for the ABB robots to print using the MDPH2 extruder we rigged up last summer. It was not the most accurate setup - I learned a lot about robotic 3d printing, but it definitely isn’t as precise as the WASP. We did get some almost workable prototypes, but the plastic seemed really uncontrollable.

When we explained the situation to Pico, and that our deadline was approaching, they offered to help out. Initially they looked into printing the lamps for us and shipping them out, but then offered to send us a replacement extruder and motherboard to use until ours was returned.

The replacement parts arrived, and I installed them, turned on the machine and,…. it seemed to be working….. but then, when it tried to go its home position it would instead continuously try to drive down through the build plate. Ugh. So Milan, the technician with Pico organized a zoom meeting with 2 engineers from WASP. They had me plug in the printer, open up the controller cabinet and peer around with my webcam inside the motherboards. Finally, we found a connector that must have come unplugged from a jolt in transportation.

That was it, the printer was finally working! I loaded up the material, and it was under-extruding, then clogged. Again, I went through the process of disassembling, cleaning, reassembling and testing over and over again with the same results.

The deadline was rapidly approaching, and so we decided it was time to pull the plug on the PET-G material. Switching back to the PLA, the printer worked perfectly. Upon reporting these results, we heard back from Pico that they had found the material was below grade, and the material properties had likely caused the issues with our printer.

In the end, Pico offered to provide us a credit for the material we had purchased. Having them quickly send a substitute extruder was also what allowed us to finally complete the lamps. We ran the printer basically around the clock for 3 weeks to print the 30 components that made up the lamps. Along the way there were numerous failures due to running out of material mid-print or having prints lift off the bed while no one was watching, and in one case having the nozzle unscrew itself and dump the contents of the pellet hopper through the extruder chamber like a plastic-spewing fire hose.

This project taught me a lot about the material properties of plastics and about large scale 3d printing, lessons which will definitely inform future avenues of investigation. Here is the full story of the project: https://news.ucalgary.ca/news/student-designed-test-project-aims-improve-safety-and-vibrancy-downtown