On Sunday, I made a few last-minute adjustments to the Printrbot+, wired the motors and sensors to its circuit board, loaded the software on my computer, powered it up, plugged in the USB cable, and gave it a whirl. Shockingly, the blue smoke remained inside the board and all axes and the extruder responded to computer control.
I applied some blue painter’s masking tape directly to the print bed as a surface, loaded up the extruder, and set it printing technoswiss’s ‘Printrbot glass clips’ so that I could install the 8×8″ sheet of borosilicate glass I’d purchased from McMaster Carr to use as a print bed. The extruded plastic would not stick to the tape. I increased the heat of the bed and extruder and had some success, but eventually gave up on that print surface and applied a surface of heat-resistant Kapton material to the print bed. That worked much better, and produced the squishy version of the clip visible above.
Monday’s subsequent attempts at printing didn’t stick to the Kapton, and I realized that I needed to recalibrate the Z-axis and attempt to level the bed, as the hot end of the extruder was just not getting close enough (it’s supposed to print from a distance roughly equal to the thickness of a piece of paper). Problem solved, but as it printed I noticed that the printhead was squishing the printed object around as if it were a block of cheese. I reasoned that this was due to excessive bed temperature, excessive hot-end temperature, a miscalibrated z-axis (the head was not raising enough between layers), and a miscalibrated extruder (it was extruding too much plastic). A few measurements and adjustments later, and a much better print was produced. It seemed like it would be usable, so I printed 3 more.
And then it seemed time to print some replacement parts before the bits that had broken in assembley stopped working. I’d split the y-axis pulley by over tightening and had also broken a y-axis belt clip. I downloaded the files and tried printing these more complicated parts. Unfortunately at this point the broken y-pulley was beginning to slip on the motor shaft, so the y-axis was not stable. The pulley is probably not going to be usable, but it does look cool. The belt clip is slanted due to the slipping y-axis, but it’ll probably work fine. I have more precise GT2 belts and pulleys on order, so it should be printing much more accurately by next week.