Fine tune bed ACD parameters

token47

The automatic calibration of my bed heating parameters got me this behavior:

0_1537728919702_0ae90e22-2cea-4221-b743-f3c5ebcf94df-image.png

I already tried manually increasing the dead time to get rid of this oscillation but no matter how high I put it the pattern does not change. What am I doing wrong? Do anyone have suggestion values to try?

Current ones are: "A102.1 C36.8 D0.4 S0.75 V12.3" (my bed is too powerful and I like to run it at 0.75 pwm factor)

Thank you

dc42

Do you have B0 on that M307 line to disable bang-bang mode too?

token47

Yes, my complete settings are:

M307 H${HEATER_PIN} A-1 C-1 D-1 ; Disable Heater pin used by probe
M307 H0 B0 ${HEATER_H0} ; Disable bang-bang and tune heating parameters
M307 H1 B0 ${HEATER_H1} ; Disable bang-bang and tune heating parameters

And also:

; Heaters Tunning
HEATER_H0="A102.1 C36.8 D0.4 S0.75 V12.3"
HEATER_H1="A674.5 C185.7 D4.8 S1.00 V12.3"

deckingman

@token47 Those commands don't look much like RepRap firmware commands.

https://duet3d.dozuki.com/Wiki/Gcode#Section_M307_Set_or_report_heating_process_parameters

token47

@deckingman they are compiled to raw gcode doing variable substitutions and sent by ftp to the duet, automatically. For the case in question, just imagine the substituted command. They are below for easier reading, this is what is actually on the config.g file:

M307 H0 B0 A102.1 C36.8 D0.4 S0.75 V12.3
M307 H1 B0 A674.5 C185.7 D4.8 S1.00 V12.3

For the record, the config generator is at https://github.com/token47/duetcfgen

thanks

deckingman

@token47 said in Fine tune bed ACD parameters:

@deckingman they are compiled to raw gcode doing variable substitutions and sent by ftp to the duet, automatically. ................................

You are talking to a 65 year old retired mechanical engineer. I have no idea what that means (but it sounds very clever)

Edit. FTP to me means Federal Test Procedure, as in Ftp75 which is/was a type of exhaust emission test.

Phaedrux

@token47 said in Fine tune bed ACD parameters:

M307 H0 B0 A102.1 C36.8 D0.4 S0.75 V12.3

Try a larger D value to increase deadtime.

https://duet3d.dozuki.com/Wiki/Tuning_the_heater_temperature_control#Section_Setting_the_model_parameters_manually

dc42

I agree, D0.4 is unfeasibly low for a bed heater. 5 to 10 is more usual. We already know that with some types of bed heater, tuning is unable to establish the dead time, and finding a better way to measure it is on my todo list.

token47

@deckingman LOL. Not exactly, but good to know that, heheh. BTW, very nice project your printer, following every move. Congrats!

token47

@dc42 Hummm, that explains why I upped the value until more than double and it still would not make a difference. Will try that. Thanks!

token47

Yes! D8.0 was perfect for my bed. I was afraid of going too high compared to the original 0.4 value and wouldn't go past 1.0. Thank you for the information that 5 to 10 were more usual values!