[SOLVED] Heated bed PID auto tune failed.

deckingman

@vapvap It's the negative dead time that's screwing it up but I don't know why you are getting that. Are you starting from a low ambient or are things really hot in your part of the world?

vapvap

@deckingman Normal room temperature (~20C).

dc42

What happens if you use a lower target temperature such as 70C?

The bed needs to be allowed to cool down completely to room temperature between tuning attempts.

vapvap

@dc42
11:20:51 PM
M307 H0 A181.2 C1041.0 D4.0 P0.5
Warning: Heater 0 appears to be over-powered. If left on at full power, its temperature is predicted to reach 206C.
11:20:43 PM
M307 H0 A181.2 C1041.0 D4.0 P0.6
Warning: Heater 0 appears to be over-powered. If left on at full power, its temperature is predicted to reach 206C.
10:39:52 PM
M307 H0 A181.2 C1041.0 D4.0 P0.7
Warning: Heater 0 appears to be over-powered. If left on at full power, its temperature is predicted to reach 206C.
10:39:27 PM
M307 H0 A181.2 C1041.0 D4.0 P0.8
Warning: Heater 0 appears to be over-powered. If left on at full power, its temperature is predicted to reach 206C.
10:38:52 PM
M307 H0 A181.2 C1041.0 D4.0
Warning: Heater 0 appears to be over-powered. If left on at full power, its temperature is predicted to reach 206C.
10:21:55 PM
Warning: Auto tune of heater 0 failed due to bad curve fit (A=181.2, C=1041.0, D=-0.8)
10:05:55 PM
Auto tune phase 3, peak temperature was 70.3
10:05:48 PM
Auto tune phase 2, heater off
10:00:36 PM
Auto tune phase 1, heater on
10:00:30 PM
M303 H0 S70
Auto tuning heater 0 using target temperature 70.0°C and PWM 1.00 - do not leave printer unattended
10:00:00 PM
M307 H0
Heater 0 model: gain 90.0, time constant 700.0, dead time 30.0, max PWM 1.00, calibration voltage 0.0, mode PID, inverted no, frequency default
Computed PID parameters for setpoint change: P46.3, I0.319, D971.8
Computed PID parameters for load change: P46.
9:59:31 PM
Connection established!
9:59:31 PM
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dc42

Try with those M307 settings. The warning message is usual when using a high-power bed heater.

vapvap

This post is deleted!

Phaedrux

What type of heated bed is it?

vapvap

@phaedrux Aluminum disc 220mm (Delta Printer).

vapvap

@dc42

In the end, I achieved a positive value.
But what to do next?
After all, the "auto tune" still does not work.

7:20:11 PM
Warning: Auto tune of heater 0 failed due to bad curve fit (A=183.8, C=1042.4, D=0.1)
7:04:11 PM
Auto tune phase 3, peak temperature was 70.3
7:04:04 PM
Auto tune phase 2, heater off
6:58:52 PM
Auto tune phase 1, heater on
6:58:46 PM
M303 H0 S70
Auto tuning heater 0 using target temperature 70.0°C and PWM 1.00 - do not leave printer unattended
6:58:30 PM
M307 H0
Heater 0 model: gain 188.4, time constant 1070.6, dead time 5.0, max PWM 1.00, calibration voltage 0.0, mode PID, inverted no, frequency default
Computed PID parameters for setpoint change: P202.9, I2.773, D710.0
Computed PID parameters for load change: P2
6:58:23 PM
M307 H0 A188.4 C1070.6 D5.0
Warning: Heater 0 appears to be over-powered. If left on at full power, its temperature is predicted to reach 213C.

Phaedrux

@vapvap said in Heated bed PID auto tune failed.:

@phaedrux Aluminum disc 220mm (Delta Printer).

And what is the heating element?

vapvap

@phaedrux said in Heated bed PID auto tune failed.:

And what is the heating element?

https://www.amazon.co.uk/anycubic-MK3-Round-Aluminium-Diameter-Printers/dp/B01LZ36INV

Phaedrux

Ok, now is it wired as 12v or 24v? What is your power supply voltage and wattage?

vapvap

@phaedrux 12V, 30A, 360W.
https://www.amazon.co.uk/gp/product/B072J97N8T/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

Phaedrux

@vapvap said in Heated bed PID auto tune failed.:

https://www.amazon.co.uk/anycubic-MK3-Round-Aluminium-Diameter-Printers/dp/B01LZ36INV

Please note: There is no Thermister not installed on the card or including in the list. Please, install the precisely Thermister

The listing says the bed doesn't come with a thermistor. What thermistor are you using and do you have the right configuration values for it?

vapvap

@phaedrux 100K Wired NTC Thermistor 3950
https://www.ebay.co.uk/itm/100K-Wired-NTC-Thermistor-for-3D-Printers-3950-RepRap-Marlin-EPCOS-Flux-Workshop-/113189674857?hash=item1a5aa15f69

dc42

@vapvap said in Heated bed PID auto tune failed.:

@dc42

In the end, I achieved a positive value.
But what to do next?
After all, the "auto tune" still does not work.

7:20:11 PM
Warning: Auto tune of heater 0 failed due to bad curve fit (A=183.8, C=1042.4, D=0.1)

In your M307 command, use the A and C values reported by auto tuning, but try a value of 5 for D. Then heat the bed to a typical temperature and see how it performs. If the temperature oscillates, increase D some more.

vapvap

@dc42 In the end, everything worked. Many, many thanks for your help.
I did it Only because You shared your thoughts and experience with me.
Without you, I would never have done it.
In gratitude, let me share my experience with you.
It is not enough, it can be useful ...
With best regards.

vapvap

@dc42 After installing MOSFET, I again cannot autotune my PID.

After endless attempts, I just got ~ :
Warning: Auto tune of heater 0 failed due to bad curve fit (A=191.5, C=1032.9, D=-0.1)
8:14:49 PM
Auto tune phase 3, peak temperature was 80.0
8:14:42 PM
Auto tune phase 2, heater off
8:08:14 PM
Auto tune phase 1, heater on
8:08:08 PM
M303 H0 S80
Auto tuning heater 0 using target temperature 80.0°C and PWM 1.00 - do not leave printer unattended
7:34:06 PM
M307 H0 A190.3 C1026.6 D5.0

Tell me please, is my MOSFET a bad idea, or am i doing something wrong?
Regards.

dc42

It's the same issue as before: the PID tuning algorithm has failed to compute the dead time for your bed.

Adding the mosfet may have changed the gain slightly but it won't have changed the time constant or dead time. Comparing your results:

Old: A=183.8, C=1042.4, D=0.1
New: A=191.5, C=1032.9, D=-0.1

this is indeed the case. So I suggest you use the A and C parameters reported by tuning, and whatever value of the D parameter that worked for you last time.

vapvap

@dc42 Unfortunately, I have again and again fail my calibration.
It seems to me that I spend too much time on it.
Maybe it will be easier to install PT100 / Thermocouple?