[SOLVED] Heated bed PID auto tune failed.

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?

dc42

@vapvap said in [SOLVED/(+/-)UNSOLVED ] Heated bed PID auto tune failed.:

@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?

I don't understand what you mean by "fail my calibration". All you need to do is add M307 P0 A191.5 C1032.9 D5.0 to your config.g file, and make sure that there isn't a similar command in config-override.g that will override it. Then heat the bed up to normal temperature. If you see oscillations then increase the D parameter. You can do this live, i.e. send the M307 command with different D parameters while the bed is hot, until you find a suitable value.

adavidm

@dc42 said in [SOLVED/(+/-)UNSOLVED ] Heated bed PID auto tune failed.:

@vapvap said in [SOLVED/(+/-)UNSOLVED ] Heated bed PID auto tune failed.:

@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?

I don't understand what you mean by "fail my calibration". All you need to do is add M307 P0 A191.5 C1032.9 D5.0 to your config.g file, and make sure that there isn't a similar command in config-override.g that will override it. Then heat the bed up to normal temperature. If you see oscillations then increase the D parameter. You can do this live, i.e. send the M307 command with different D parameters while the bed is hot, until you find a suitable value.

It looks like @vapvap is setting the parameters using M307 and then running an autotune with M303, thinking that that is needed. Possibly a language barrier problem?

adavidm

vapvap

@adavidm I'm afraid that you are absolutely right. That's how I understood the instruction ...
Sorry guys, I'm a total novice.
I just needed an instruction for dummies.

vapvap

@dc42 Thank you, I'll try.