PID Autotune Not Working

I've run PID tuning several times, especially when I take a shift in temp usage [like when I raised temps for ABS/PA alloy experimentation]. But no matter what, it always overshoots, and stays that way, on lower temps [230C for example, will not* get bellow 234C].
I've done M303 E0 S235 C8
And I've done M303 E0 S235
And one of the two, don't remember which, at 200C.
Am I doing something wrong? I always start it cold and don't touch anything until it's finished, then I put the values in to the EEPROM.

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Realizer- One who realizes dreams by making them a reality either by possibility or by completion. Also creating or renewing hopes of dreams.
"keep in mind, even the best printer can not print with the best filament if the user is the problem." -Ohmarinus

Just ran it again at 200C cycling 8. Still overshooting and staying such. It's not so much a problem for printing, at all really, but it often times adds waiting time to the start of a print as it waits for the heater to stabilize.


I'm running an E3D v5, no mods to it.

Edited 1 time(s). Last edit at 07/07/2014 12:33PM by MrDoctorDIV.

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Realizer- One who realizes dreams by making them a reality either by possibility or by completion. Also creating or renewing hopes of dreams.
"keep in mind, even the best printer can not print with the best filament if the user is the problem." -Ohmarinus

is there a fan always on to carry away the heat? this is a full metal hot end correct?

pid only works if there is variation to correct and a known loss, if it always overheats it is because the integral part is not the same, meaning that the part stays heated when it should be cooling. if you want precise control without a fan you will need to adjust differential to a lower amount and it will take a lot longer to heat up. also make sure pid is enabled and power output is less than 255, look in configuration.h for values to change, and be sure to have an fan always on blowing at the top end of the hot end, otherwise the only thing to cool the hot end down would be feed stock flowing thru.

another issue is if the heater is too powerful, or the heater block with the thermistor a poor conductor of heat, will prevent ambient air the chance to allow for a lower temp equilibrium to reach the thermistor. stainless steal has a delay of 10 seconds or more for equilibrium of temps to reach the other side of the material in heater block for example.

if after you apply active cooling the heater keeps overshooting, then replace the heater block with another one made of brass, or aluminum.

Edited 1 time(s). Last edit at 07/07/2014 01:14PM by jamesdanielv.