Extruder overhoots while heating up

kdehm

Hi there,

I updated the firmware on my Boxzy printer to add a heating bed in the setup.

While the heating bed is working, now the extruder temperature overshoots everytime when heating up. When (manually) setting the heater to 200°C, it gets up to approx. 250°C, but target temperature can be reached if extruder is deactivated earlier.

Playing with the parameters (in PID control / Dead time control) doesn't change anything.
So I'm able to print, but it makes me a bit nervous.

Here you can see the overshoot and the temperature swinging further on:

Unfortunately, I havn't the the old firmware settings and Boxzy do not reply either.

Do you have any ideas how to calibrate without knowing the exact extruder facts?

Thanks in advance!
Kai

Repetier

Ok, don't see 50°C overshoot here but 20 and it is surely not calibrated correctly.
Have you tried M303 to get a proposal for PID values? Which firmware does it use?
If you see the output you clearly see that the I part is not working correctly making it so unstable. You should see that it builds an average pwm value. So why does I not accumulate? Too small or did you contrain it so it is not allowed to raise?

kdehm

Thank you for the reply and the hint!

When you look at the picture above, then you can see that I switched off the heater manually, to avoid the high overshoot, but temperature kept rising (otherwise it would have reached _250°C)
Firmware is 1.0.4

It turned out that the heater power was way too high and dead time control wasn't working properly in my case.

I set the the power to 100 and used PID controller. With M303 (thank you for that) I got the values: P=4, I=0.3, D=13, which seem to work well. Swinging is left now only at preheating and later when the fan is turned on.

Kai

Repetier

Last image looks like temperature is jittering a lot. But maybe you are still on 60 minute interval and that are just the swings. But look sin deed much better. Dead time is hard with high power extruder. When activating it makes a big jump after a few seconds you are just lost.