hello everybody,
I am facing an issue which has been presented in different shapes, I hope someone will give me a hint. In my handmade 3D printer, I have installed a heated bed, which was not present at all before. I am using the firmware Marlin 3.1.3b2. Heating is provided with a couple of 200W 24V mats with embedded 100K thermistor. The mats temps are correctly read out by Marlin (M105 and temperature bottom status bar), as well as the hotend temperature. Mats power supply is generous, 600W.
I have configured Marlin with PID control both in hotend and in bed heating sections. M303 E-1 C8 S60 performs smoothly , cycles up to the desired 60 °C temp are covered, and the given Kp, Kd and Ki params have been reported by me in the configuration.h section of the Arduino IDE, with firmware reloaded (many times).
The issue is that bed heating (either M140 or M190) stops 10 °C before the desired target, i.e. at 50°C instead of 60. The heating hardware is capable of reaching that temp and well beyond: if I issue M140 S100, heating goes up to 90°C and then starts swinging around 90, never reaching 100 °C. If M190 command was given, that results in a stop waiting for temperature. If otherwise M140 was given, execution is not stopped, but the target temp is nevertheless not reached.
The difference from the goal and the yielded temp appears to be always 10°C exactly.
I have tried to tinker with the hysteresis section of my files with no luck.
I have tried previous not beta versions (3.1.2.5, 3.1.2.7) but I am facing compilation errors I still have to work out.
I can use a workaround editing the G-Code file,replacing M190 entries with M140 (with +10°C target) followed by a pause, but it is nasty.
Any suggestion?
Thank you for helping.
Riccardo
