Build, Test, Document
Build, Test, and IntegrateWork for the building and test phases was split among the team members in a democratic fashion. The mechanical engineering machine shop was utilized as well as the Brinkman Lab for machining of material and testing of subsystems. Total machining time is roughly around 30 or 40 cumulative hours. Special thanks to Rob Kraynik and Jan Maneti from the machine shop for their assistance in design and machining capabilities, and to John Bonzo from the Brinkman Lab for design critique.
Once the parts had been machined, the system assembly began, and shortly after, testing. Some of the testing revealed further design changes which were made promptly, depending on the importance of the change.
From left to right: Nozzle Adapter, Aluminum Barrel, Steel Barrel, Screw, and Bearing Housing.
The old ball bearing with rubber seal was replaced in favor of a graphite insert (black inner ring) and a brass sleeve bearing (outside the graphite). These materials can withstand much higher temperatures. The old one started to melt, and the oil started to burn up during testing.
The final design ended up being significantly differently than the originally planned one. The print head was mounted to a rig to allow it to be moved and tested without the use of a 3D printer. It uses a standalone PID controller (left) and motor controller(right), rather than ones that interface with Arduino. The reasons for this are that the motor was too large for the Arduino to handle, and as a result we decided to not use the Arduino for the temperature as well.
During one of the tests, it was discovered that the screw was being pushed up due to the pressure, so a brass collar was added to prevent upward motion. During this time we were able to see the plastic distribution in the print head.
First test, and material was able to flow through the 0.4mm nozzle successfully!
After the first test, pressure became an issue, and no material was flowing through the nozzle. The test was continued with no nozzle attached, and produced these samples. From left to right, the residence time decreased (leftmost spent about a half hour in the print head, and the rightmost spent about a minute in the print head). It is clear that the long time spent inside the heated chamber burned the plastic.