Concept 3 First Testing
John and I met up today to work on our concept 3. The frame still needed some work, so we just tested out the 1″ pipe and the heater setup. The picture below shows the PID temp controller, 12V battery, solid state relay (SSR), 1″ pipe, heater band, and the plunger we used to push the plastic through. This was set up one a press because we were not sure what pressure everything needed to be run at. The Temperatures in the picture are in units of Fahrenheit.
The first test included the pineapple in the pipe with it press fit in. Our first test we used HDPE because the heater band we were using had trouble getting above 200 C. This would not have worked with ABS but HDPE has a melt temp of 120-130C. Once the temp got around 130 C, we filled up the pipe and pressed down on it. We noticed that a lot of force was being applied to the pipe and probably something was wrong. The test was stopped and the assembly was taken apart. The cap was difficult to get off and we found out that the pineapple had slipped down and blocked the nozzle entrance. The pineapple itself was clogged in the pipe with molten plastic around it (hey it worked though). A blow torch and a hammer solved that issue quickly.
Next test, we removed the pineapple and just used the pipe,cap, and nozzle. We hooked everything back up and proceeded to apply heat again. We kept an eye on the force gauge on top of the press. If we started to apply any kind of force, then we had to stop and let the plastic melt. The video below shows our first extruded material.
So some thing to work on for next time. The filament was brittle because it was not heated fully and uniformly. The plastic on the outer wall was melted but the inner material was not. This will be fixed by a the pineapple. Next, we measured the filament and it came out to about .126. When the inside diameter of the nozzle is .118 (~3mm). This expansion would be due to the large amount of pressure being applied to the not fully melted plastic. Further testing will decide our course of action. Our backup plan is to machine a bolt a a nozzle. We have more control on the accuracy that way. Below is a picture of the HDPE we pulled out of the nozzle. The HDPE was easy to clean as it didn’t stick to the metal and just popped right off. So far HDPE has been a pleasure to work with and this orange is a very nice color. It is almost a hunters orange.