Copper heat blocks and heater calibration failures with 6.4.0-RC
It seems running heater calibration is hit or miss when using a copper heat block. I accidentally reran it (I needed to run other tests) and it kept failing. This creates an annoyance because the printer will display nag screens that the calibration is not complete when turning on the printer and I have to hit "OK" to continue. It will also do the same before starting a print. To make it pass I swapped out for an aluminum heat block.
I haven't dug into the firmware source code yet, but if I were to guess, the PID settings in firmware are calibrated to an aluminum block and the heater test is probably testing for ramp up time which then fails. Otherwise, the copper blocks work fine.
- Bob Marley
RE: Copper heat blocks and heater calibration failures with 6.4.0-RC
I'm using a copper heat block on my Core one and don't experience this. Since you've changed the heat block the heater set screw must be snug, one possibility. Try a different heater? This is a test of that element after all. If there's some on hand, maybe some thermal paste.
RE:
The test doesn't pass consistently. Otherwise there is nothing wrong with the heat block. It comes up to temp set in g-code and stays there.
I replaced the heat block with aluminum (same heater and thermistor) and it passed 100% of the time. I'm not doing anything crazy with the grub screw like making it too tight. My guess is that there is probably a timer and if the test temp isn't reached before the timeout, it fails.
- Bob Marley
RE: Copper heat blocks and heater calibration failures with 6.4.0-RC
So basically Prusa confirmed to me that they (in essence) don't support 3rd party heat blocks, i.e. non-aluminum directly in the firmware. For sure, M303 S<temp> will run PID and those parameters can be injected into the startup g-code but passing the heater calibration (for copper blocks), running and storing PID from the UI is currently not supported. I created an enhancement request so hopefully some day in the future they will add it.
- Bob Marley
RE: Copper heat blocks and heater calibration failures with 6.4.0-RC
The request for the PID calibration function from the printer menu has been rolling on Github since February 2025. It even has an internal ticket created:
https://github.com/prusa3d/Prusa-Firmware-Buddy/issues/4490#event-3343261833
No need to create a new request, just support the old one.
RE: Copper heat blocks and heater calibration failures with 6.4.0-RC
The request for the PID calibration function from the printer menu has been rolling on Github since February 2025. It even has an internal ticket created:
https://github.com/prusa3d/Prusa-Firmware-Buddy/issues/4490#event-3343261833
No need to create a new request, just support the old one.
My request is specific to the heater calibration test failing for copper blocks: https://github.com/prusa3d/Prusa-Firmware-Buddy/issues/4901
- Bob Marley
RE: Copper heat blocks and heater calibration failures with 6.4.0-RC
Since it is not possible to edit an older post, here is an addition to the problem: According to the request, I understood that it is an initial calibration. That is of course something different. Here it would be necessary to actually perform a calibration with the type of block for which the correct values are in the FW. If Prusa really accepted my request for the function, in my opinion, the following initial calibration could be performed according to the last written PID value. But I could be wrong and, for example, after resetting the printer to the factory settings, the factory values for the aluminum block will be used for the initial calibration. Although I understand why Prusa does this and it was explained quite well, because after the first start, the printer really does not know if there is an error in the assembly and has nothing to catch.