Hot end staying at 30C even after start
Hi
Both of my Prusa MK4's is showing the hotend at either 28C or 30C all the time. This is not just after a print but after being turned off overnight and starting up. This seems to make the fan come on every minute or so for a brief whirr.
I can imagine one thermistor failing but two seems unlikely. I can't see any setting that is keeping this slightly higher than ambient temperature (well as this is the UK, a lot higher :))
Running firmware 6.4 and Octoprint but not had any issues to date.
Stuff prints fine, I'm just trying to work out what, if anything, is the problem.
Any and all suggestions welcomed
Rob
RE: Hot end staying at 30C even after start
Just found firmware 6.5.3 and upgraded both Prusa's. The hot end appears to be cooler now at 22C BUT there appears to be a bug in the Prusa firmware. If you do a M115 command, you get back
Send: M115 Recv: FIRMWARE_NAME:Prusa-Firmware-Buddy 6.5.3+12780 (Github) SOURCE_CODE_URL: https://github.com/prusa3d/Prusa-Firmware-Buddy PROTOCOL_VERSION:1.0 MACHINE_TYPE:Prusa-MK4 EXTRUDER_COUNT:1 UUID:cede2a2f-41a2-4748-9b12-c55c62f367ff Recv: Cap:SERIAL_XON_XOFF:0 Recv: Cap:BINARY_FILE_TRANSFER:0 Recv: Cap:EEPROM:0 Recv: Cap:VOLUMETRIC:1 Recv: Cap:AUTOREPORT_TEMP:1 Recv: Cap:PROGRESS:0 Recv: Cap:PRINT_JOB:1 Recv: Cap:AUTOLEVEL:1 Recv: Cap:Z_PROBE:1 Recv: Cap:LEVELING_DATA:1 Recv: Cap:BUILD_PERCENT:0 Recv: Cap:SOFTWARE_POWER:1 Recv: Cap:TOGGLE_LIGHTS:0 Recv: Cap:CASE_LIGHT_BRIGHTNESS:0 Recv: Cap:EMERGENCY_PARSER:0 Recv: Cap:PROMPT_SUPPORT:0 Recv: Cap:AUTOREPORT_SD_STATUS:0 Recv: Cap:THERMAL_PROTECTION:0 Recv: Cap:MOTION_MODES:0 Recv: Cap:CHAMBER_TEMPERATURE:0 Recv: ok Send: M155 S2 Recv: ok
The key line is THERMAL_PROTECTION:0 I believe this is should be THERMAL_PROTECTION:1.
This is checked by Octoprint and it throws a big warning up. I believe this is a firmware bug from Prusa, or rather the lead Octoprint developer certainly does and she knows far more than I do (not difficult). You can find the thread here https://community.octoprint.org/t/octoprint-tells-me-that-my-printers-firmware-lacks-mandatory-safety-features-what-does-this-mean/350/84
I'm unsure if there is an actual firmware bug OR it's a reporting bug. I'm going to downgrade back to 6.4.x just in case though