Override heater fault error

Velvia

I keep getting this error since my bed is slow to heat up. PID tuned it several times. It's a 320mm AC bed of 300w, which isn't enough to heat the 380x5mm aluminium bed fast enough. It does reach it's final temp eventually, so I just need to override the error. It's a Duet 3 MB6HC.

Phaedrux

What error are you getting exactly?

What does your temp graph look like?

What are your PID values?

What firmware version?

Velvia

@Phaedrux

Error: Heater 0 fault: temperature rising too slowly: expected 0.40°C/sec measured 0.11°C/sec
M307 H0 R0.687 K0.500:0.000 D2.48 E1.35 S1.00 B0
Firmware: RepRapFirmware for Duet 3 MB6HC 3.4.1 (2022-06-01)

Don't have a picture of my graph right now. It's an AC heater through an SSR.

Phaedrux

At what point does it error out? I get the same errors myself, usually it's right near the end of the heating phase when it's nearly at temp.

Velvia

@Phaedrux Usually during the beginning. At like 10-20% if that makes sense. Sometimes later.

Phaedrux

300w is a bit on the low side for a 320mm plate, but should still be able to hit temp reliably when tuned.

Velvia

Did a new PID and it now does 0.13 instead of 0.11

Heater 0 fault: temperature rising too slowly: expected 0.44°C/sec measured 0.13°C/sec

I just want this to not interrupt the heating. Is there no way to disable it?

gloomyandy

@Velvia I don't think you can disable that function. However you can probably manually adjust your heater parameters (in the M307 command) to better match what actually happens see: https://docs.duet3d.com/User_manual/Connecting_hardware/Heaters_tuning You may want to decrease the R parameter, or perhaps increase the D parameter.

The other thing to consider is is there anything different in the environment when you tune the heater compared to when you are heating the bed for a print (so for instance is there any sort of fan that is active when printing, but not when tuning)?

Velvia

@gloomyandy

Thanks for the tips. Will try playing around with those parameters. Also thinking of adding some insulation under the silicon mat.

Phaedrux

Insulation would help for sure. You may also want to try creating a macro that heats the bed in stages. It may take a bit longer, but would hopefully be a bit more reliable until we can figure out what's going on.

dc42

@Velvia how close to the desired temperature is it when that fault is generated?

Velvia

@dc42 It's random. I set it to 105, then the fault will happen at anything between 40 and 105. It helped to decrease the R parameter and increase the D parameter. Haven't had the fault since.

dc42

@Velvia I'm glad you found a workaround. Reducing the R parameter reduces the heating rate that RRF expects. Increasing the D parameter delays the start of checking the heating rate.

You may also find it less sensitive in more recent firmware versions.

I'll mark this as solved, but feel free to change it back if the problem recurs.

joeko

i have the same error with the latest firmware (3.45)

dc42

@joeko please start a new thread. This one is marked as solved, and your situation may be significantly different,