Friday, Mar 2 2018
After loading up the new software I ran PID Autotune just because. PID settings are used to control heating, getting the nozzle (or bed) to a stable temperature without large temperature swings around the desired value. A while later I tried printing PETG filament the first time. PETG prints at 230 °C, a higher value than the 205 °C I use for PETG. The nozzle came up to temperature but would not stabilize. Hmmm. I restored the default PID values and tried again. The nozzle stabilized (more or less) at 230 °C but it took a good minute after coming to temperature. The graphs:
Autotune PID values — the temperature never stabilized
Default PID values — quite noisy
Guess: the noise on the temperature value screwed up the Autotune PID process. The noise probably comes from a known issue with 5V regulation on some printers. My CR-10S needs a capacitor swap to better filter the 5V line to get more stable temperature control. The manufacturer used a not quite up-to-spec capacitor. A proper capacitor has been ordered.
I didn’t think my machine had the issue because people were reporting 7-10 degree temperature swings and I was only seeing 4-5 degree swings with the default PID settings. I didn’t know that swings should be much lower than that. Seeing the nozzle temperature swing when setting idle at ambient temperature is apparently a good indication that your machine needs fixing.
I’m curious to see if better temperature regulation will help get rid of the small holes I’m seeing. I installed a weaker spring on my extruder and am still seeing the holes in test prints. Chewed up filament does not seem to be the issue.