Overshoot and really unstable hotend temperature

[databird]

Hello !

I'm upgrading a professional 3D printer (Intamsys Funmat HT) with a Duet 2 Wifi controller and have a lot of problem with hotend temperature.

I try auto-tunning, and play a lot with M307 settings, but nothing work : overshoot & unstable temperature (-7°, +13°)

Duet :

• Duet WiFi 1.02
• RRF : v3.4.5
• WiFi firmware : 1.27
• PT100 daughterboard

Printer :

• Intamsys Funmat HT (work very well with original mainboard)
• CoreXY
• 24v 65W heat cartridge
• PT100 sensor

Tests are done with hotend temperature set to 220°, no FAN (but same if fan's on)

M307 values from autotunning :

M307 H1 R2.797 K1.566:0.000 D14.30 E1.35 S1.00 B0 V24.0

Always overshoot :
"Heater 1 fault: exceeded allowed temperature excursion: target 220.0°C actual 240.0°C"

To remove the overshoot, I need to change to Bang-Bang mode, and set 80% power

M307 H1 R2.797 K1.566:0.000 D14.30 E1.35 S0.80 B1 V24.0

But temperature is really unstable :

Target : 220°
Oscillate between : 213° and 233°

And if I change M307 settings, nothing change :

M307 H1 R3.797 K1.566:0.000 D4.30 E1.35 S0.80 B1 V24.0        ; oscillate : 213°-233°
M307 H1 R4.797 K1.566:0.000 D4.30 E1.35 S0.80 B1 V24.0        ; oscillate : 213°-233°

M307 H1 R4.797 K2.566:0.000 D14.30 E1.35 S0.80 B1 V24.0       ; oscillate : 213°-233°
M307 H1 R1.862 K2.566:0.000 D14.30 E1.35 S0.80 B1 V24.0       ; oscillate : 213°-233°

And here's the : config.g

Is anybody have an idea to help me ?

Thanks for your support !
Serge

[dc42]

@databird said in Overshoot and really unstable hotend temperature:

To remove the overshoot, I need to change to Bang-Bang mode, and set 80% power

No, you just need to adjust the M307 settings. This will not work in bang-bang mode! You will always get oscillations in bang-bang mode.

To reduce overshoot, increase the M307 R parameter.
To eliminate oscillation, increase the D parameter.

[databird]

@dc42 You're a master !
After days of tests... you give me the right answer ! All is working fine now !

My error was, when I tested with PID, it was overshooting (+50° !!!) at first heat, So I stopped all other tests with PID... my bad !

Thanks again !

[Phaedrux]

What kind of heater does this machine have?

[databird]

@Phaedrux This is a heat cartridge 24V 65W

Some pictures :