Troubleshooting Extruder

Hi, new to this RepRap thing, so if there's a great FAQ or some step I missed, please let me know. Moving on,

I just got my machine generally assembled and wired and prior to getting the endstops running (all servos check out) I was testing the extruder. Frankly, I'm at a loss as to if I made an error or if things aren't running correctly.

I'm running a hot end that came pre-assembled, but I know is nichrome for heat with what I believe is a .4mm orifice. At a rated 270 degrees the plastic barely dribbles out with no discoloration. The stepper refuses to move the filament and even by hand the feed mechanism skips over the plastic. I can back off on the idler wheel tension, but then the extruder refuses to apply any force and just sits there spinning if I try to run the motor.

Temperature reads 21 degrees at idle in a 70-72 degree Fahrenheit room, so I assume I have the correct table there. Motor is a NEMA 17. Running RepSnapper. Generation 3 Electronics.

Frankly the reason I stopped turning up the temperature is I vaguely recall a lot of components only being rated to 300 degrees. Regardless of the nozzle temperature, if the thermocouple exceeds rated temperature I can lose my feedback system.

Any help would be appreciated. Thanks!
Mike

It sounds like the not so hot part of the hot end channel is too small. Can you push filament through by hand easily. I don't mean turn the gears by hand, but rather loosen the idler and actually PUSH the filament in. If you cannot, then you should measure the I.D. of the feed hole, and if it is too small, drill it out a bit.

For example, my filament tends to be about 3.2mm wide max. My feed hole down to the tip is 3.5, and the tip is 3.2.

I'll have to doublecheck all those locations and dimensions, but I think I found the problem while testing for that. Turns out the alignment problem I thought I fixed is back. It takes a tremendous amount of force to even remove the filament. It's got to be misalignment between the hot end and the extruder. I already had to move the holes almost an eighth of an inch.

I'm afraid most of this extruder is going to get replaced with printed parts once I get this version up and running. There's just way too much slop and error in all these parts.

Edited to add: I've found my problems. The friction fit gears slip on the shafts and the extruder wiggled loose. This is looking like quite the project to get it up and running.

Edited 1 time(s). Last edit at 08/06/2011 12:53AM by Michael F.