Heater autotuning Warning

claustro

Below my autotune results of hotend. Is the warning something I have to care about?

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12:30:14 M303
Heater 1 tuning succeeded, use M307 H1 to see result

12:29:56 M500

12:29:42 M307 H1
Heater 1 model: gain 539.2, time constant 182.0, dead time 4.3, max PWM 1.00, calibration voltage 24.0, mode: PID
Computed PID parameters for setpoint change: P14.0, I0.077, D42.2
Computed PID parameters for load change: P14.0, I1.126, D42.2

12:12:48 Warning: Heater 1 appears to be over-powered. If left on at full power, its temperature is predicted to reach 564C.
Auto tune heater 1 completed in 282 sec
Use M307 H1 to see the result, or M500 to save the result in config-override.g

12:12:22 M303Heater 1 is being tuned, phase 4 of 4

12:10:00 Auto tune phase 3, peak temperature was 246.5

12:09:52 Auto tune phase 2, heater off

12:08:11 Auto tune phase 1, heater on

12:08:05 M303 H1 S240
Auto tuning heater 1 using target temperature 240.0°C and PWM 1.00 - do not leave printer unattended

dc42

Looks OK to me. The warning message is common, especially since E3D started shipping silicone socks with their hot ends.

Lakko

I have a similar result, so if i try without the silicon protection it may not display the warning message?

Warning: Heater 1 appears to be over-powered. If left on at full power, its temperature is predicted to reach 576C.
Auto tune heater 1 completed in 214 sec
Use M307 H1 to see the result, or M500 to save the result in config-override.g

Edit:
I have tryed it and i still have the warning:

Warning: Heater 1 appears to be over-powered. If left on at full power, its temperature is predicted to reach 476C.
Auto tune heater 1 completed in 181 sec
Use M307 H1 to see the result, or M500 to save the result in config-override.g

So 100°C less then with the silicone protection

claustro

I checked the heater cartridge resistance.
My previous cartridge was about 20 ohm , this on is about 15 ohm , should be this the cause of the warning?

dc42

15 ohms at 24V gives a heating power of 38.4W, which is high especially for a heater with a silicone sock on it. So that high heating power contributes to the problem.

You could turn down your 24V PSU to 22V or even lower, but of course that will reduce the bed heater power too if it is powered by the same PSU. Or buy a 25W heater cartridge. Or just accept the warning.

deckingman

As David's comments above or you could try tuning it/running it with lower PWM e.g tune it with M303 P0.9 S240. If you still get the warning, try S0.8. That's what I did to tame the ridiculous 80Watt heater that was supplied with my 5 colour diamond hot end (which I later replaced with a 40Watt one).

vbtalent

Just trying to understand the warning since I also see the warning when tuning..

12:12:48 Warning: Heater 1 appears to be over-powered. If left on at full power, its temperature is predicted to reach 564C.

Does this mean it is assuming that it will be supplied full power, shouldn't that be controlled by the duet?

12:10:00 Auto tune phase 3, peak temperature was 246.5

Does this mean that the controlled temperature was 246.5 C which is within the 285 C setup recommended by E3d on a E3dv6? If so, then why the warning?

https://e3d-online.dozuki.com/Guide/V6+RepRap+Firmware+Configuration/26

VB,

dc42

Yes the temperature should be controlled by the Duet; but hardware can fail and software can have bugs, so you shouldn't totally rely on it being controlled, especially if you ever leave your printer to print unattended.

The peak temperature just tells you how high the temperature got during auto tuning, which will be a little higher than the temperature you specified in the M303 command.

claustro

thank you all for the answer, I am thinking about to buy a 25W cartridge , just for added safety

vbtalent

Thanks for confirming.

So, if the heater is controlled by the board and if safety is the concern shouldn't the shutoff happen at the board simply by not supplying voltage to the heater if past a certain temp or if it can't read the temperature of the thermister? I'm sure these suggestions are already baked into the design, just making sure I understand how it should work.

Also, if changing to a 25w heater what safety does that offer? can't it still "run away" and continue to heat causing the same problem?

VB,

dc42

Yes the firmware has an independent temperature monitor that attempts to turn off any heater that exceeds it's temperature limit set by M143. But that won't work if you have a short in your wiring, or the heater control mosfet blows (which is very unlikely but not impossible).

Using a lower power heater cartridge will reduce the temperature that is reached if the heater remains on at full power.

vbtalent

Thanks Dave for all the valuable information.