I have calibrated my thermistor tables by reading the R2 values carefully and generating new custom tables for both the extruder and the heated bed. When I turn on the 12v power I can read both thermistors and they both show reasonable and similar values (about 22C). Looks good so far!
Then I turn on the heater for the extruder. Immediately the temperature reading from both thermistors drops about 5C (22%). If I turn on the HBP, the thermistor value drops 2C more for total error around 33%.
I'm guessing there is some voltage-drop problem causing a variance in the Vref, but I thought that shouldn't matter. I'm not sure how to diagnose it. I've tried two different PSUs (one is brand new 600W, bought for this printer). I read a steady 12V across the power output from the PSU on my DMM during these tests.
Extrusion tests of measured values:
180C: I can extrude tiny bit of ABS, and it solidifies almost as soon as it leaves the 0.4mm nozzle.
210C: I can slowly extrude endless ABS
220C: I can extrude ABS by hand at a decent speed, I guess.
260C: I can extrude an easy stream of ABS. I sometimes here a 'pop'.
I think these values sound about right, so I guess it's measuring correctly. But how can I be sure? And why the initial drop?
I'm using Teacup firmware, if that matters.
Is this normal? If not, do you have any ideas where I can look for the source of the problem?
