Temperature stabilised test

[appjaws]

Eventually my hotend temperature stabilise so I need to delay the print start until the temperature is, say +-0.5 (is that reasonable?)

With my limited skills I have tried to have conditions to check the heat.heaters[1].current
but I end up in a loop or it is ignored and the print never starts.

Could anybody suggest a suitable test please

[PCR]

Easiest solution

Add a G4 S10 (10seconds wait) before the Print start after the heating. Or how long it needs

[engikeneer]

@appjaws why not just use the tolerance parameter (S) in M116?
https://duet3d.dozuki.com/Wiki/Gcode#Section_M116_Wait

You can just set that to 0.5degC or whatever you need

[A Former User]

if the heater has large overshoot then maybe trying to re-tune the PID under the same conditions as a normal print might help M116 do its job

[appjaws]

@PCR Thanks, but I need something that is more automatic, especially during tool change, and keeps the wait time to a minimum.

@engikeneer Thanks, tried that but as soon as the temperature is reached, the print starts even though the overshoot is 5C.

[DonStauffer]

@engikeneer I'm looking at this issue right now.

If I wait for the temperature to be within tolerance, it could see that as the temperature is in the process of overshooting (which is normal). Then I'd be printing at too high a temperature at first. This actually just happened to me yesterday, which is why I did a search on this topic.

What I probably want is for the temperature to STAY within tolerance for a specific period of time, indicating it is stable (not just "passing through"). Perhaps it would be enough to do something like:

M116 P0 S1
G4 S1 ; Allow for Overshoot
M116 P0 S1 ; Wait for Recovery

The 1-second delay gives it time to overshoot by more than the tolerance, and then it waits for it to come back down. I've never seen a properly-tuned hot end drop below the target substantially after recovering from overshoot.

Update: 1 second wasn't NEARLY enough. I'm trying 12 seconds now. There needs to be time for the temp to reach 1 below the target, and continue up to 1 above the target.

[Phaedrux]

@donstauffer Perhaps best to re-tune or manually adjust the parameters to remove the overshoot entirely?

If during initial heating the temperature undershoots the target, reduce the A parameter ((RRF 3.2 and earlier) or increase the R parameter (RRF 3.3 and later). If it overshoots the target, increase the A parameter or reduce the R parameter. Try increasing/reducing it by 5% or 10%.

https://duet3d.dozuki.com/Wiki/Tuning_the_heater_temperature_control

[DonStauffer]

@appjaws I'm watching my 2-color print with those 2 additional temperature stabilization lines in the startup and tool change scripts. OMG, does that matter! Stringing is down, consistent appearance and sheen, even extrusion! Wow!