This weekend I did the first full test assembly of the extruder! It went pretty poorly.
I tested the drive motor before I mounted everything, and it appeared to rotate (foreshadowing).
I got the whole thing assembled and mounted on my ender 3. I used a printed quickswitch mount so I can swap between the granules extruder and my standard bowden. I lost probably 4-5 cm of y axis since the carrage is thicker now, but I'm fine with that.
While mounting, I kept having issues with my thermistor coming out of its hole. Since the whole thing was already mounted and wired, I ocouldn't really try to get the screw to hold it in place, so I jury-rigged something to keep it there.
My goal was to heat the hotend, see if it could maintain temp, and verify that the extrude stepper would correctly spin the screw.
Heating the hotend went fine at first, it got warm and the temp kept going up! Slower than with my other hotend, but it's probabluy 4x the mass so that doesn't suprise me. I heard some popping from the glass insulator but I didn't notice any obvious cracks.
Once it got to 180c I tried to extrude, but the motor didn't seem to spin at all! I didn't get much of a chance to investigate, because right after that my printer threw a thermal runaway error and I shut the whole thing down. I was out of time for the day, but in the last couple of minutes I noticed that the glass insulator had completly cracked in half.
- Verify that my stepper works while not mounted to the main gear
- Verify that the stepper can drive the main gear
- Verify if the thermistor hole can accomidate the thermistor hold screw, and if not make a new one that does
- Try to heat the hotend by itself and verify that it can maintain temp
- Cut a new insulator, trying very hard not to make any small cracks
- Test everything again, and hopefully get something extruded!
- Do I need thicker glass? My current glass is just window glass, would it not crack if it was substantially thicker? Multiple layers?
- Do I need to make any firmware changes?
I designed some printed angle brackets to attach the hotend to the coldend assembly, and they didn't melt! As far as I could tell the rods didn't even get warm, but it was hot for 5 minutes so that wasn't a real test.
Also, if I ever redesign the hopper, I have some ideas now! Since I already have a carrage, I don't need the holes or any of the back half, so I could probably make the whole assembly smaller. The only things I want to add right now is the quickswitch mount I'm using, and some cable runs.
Here's a low quality photo of my build after the failure. You can even see the duct tape for the thermistor!
