Hotend temp fluctuations-~6 degrees  

Re: Hotend temp fluctuations-~6 degrees

Values of PID regulator don't quite match your setup.
Follow http://www.reprap.org/wiki/PID_Tuning
The best way to save new values is to put corresponding M301 into starting gcode.

Re: Hotend temp fluctuations-~6 degrees

Do note that PID tuning is tuning for a specific temperature. If you use multiple temps, I would recommend PID tuning for EACH temp.

Re: Hotend temp fluctuations-~6 degrees

I'm having some issues with nozzle temp fluctuations that I think may be causing some issues in the printing of fine columns. The temps vary approximately 6C.

Here is the Octoprint temp history:

The test model shows some variation in layer thickness on a printer with the new heater block/cartridge thermistor/thermistor connector

The same model printed on another printer with a rock-solid octoprint temp history. This printer has the old-style heater/glass thermistor, and crimped thermistor connector:

I saw the Help site description of the thermal runaway and the updated issue with the thermistor connector, but I'm not getting significant temp swings like that.

Any ideas as to what might be causing this? Is it the thermistor connectors? Something else?

I had both the fluctuations due to the thermistor connector and the oscillating temperature once I fixed the connector. I followed Peter's advice about tuning PIDs and that fixed the oscillations.

This PIDs are for the e3d v6 with the sock but they work just as well without the sock. Just in case somebody wants to reproduce the numbers.

Firmware PIDs p:40.93 i:4.88 d:86.08 c:1.00

My PIDs now set in the start g-code... M301 P21 I1.6 D70. I took something of an average of both targets.

2 runs target temperature 240 degree C
M303 S240 C8
Kp: 19.22
Ki: 1.39
Kd: 66.52
-
Kp: 20.20
Ki: 1.52
Kd: 67.02

3 runs target temperature 210 degree C
M303 S210 C8
Kp: 22.26
Ki: 1.72
Kd: 72.10
-
Kp: 23.07
Ki: 1.82
Kd: 73.24
-
Kp: 22.99
Ki: 1.78
Kd: 74.38

Re: Hotend temp fluctuations-~6 degrees

I have to add that I did not observe any quality problems with my prints due to this oscillations. I guess that depends on how forgiving the filament is. They just seemed odd and didn't give me confidence in the printer. Definitely worth fixing.

Re: Hotend temp fluctuations-~6 degrees

Some slicers (such as KISS) have a "Material GCode" option, which is the best place to put the M301/M304 commands.

Peter