PID Tuning an E3D hotend

[KaibutsuX]

I just finished installing my new E3D hotend and I did the final torque adjustment and now I'm ready to run the PID autotuning process.

My question is, during the process should I have the barrel cooling fan on? If so, how do I enable the fan from repetier? The fan control does not control it as my fan is wired to "Fan1" on the rambo and my configuration.h is set to enable the fan on pin 6 when the extruder is on, but after starting the process once, the fan never turned on. I know the fan works, it does turn on when I click the 'Heat Extruder' button, but I'm guessing that it doesn't get started automatically during the pid process.

So if it does need to be on, how can I manually start it from repetier?

[mhackney]

You should calibrate your PID under as near real world use as possible, so yes, leave the barrel cooling fan on. If you can't send gcode to turn it on and off, then you might have to temporarily rewire it so you can use a switch to turn it on. It sounds like the firmware is turning on the fan when the temp gets above a threshold.

From the firmware:

Code: Select all

/** The extruder cooler is a fan to cool the extruder when it is heating. If you turn the etxruder on, the fan goes on. */
#define EXT0_EXTRUDER_COOLER_PIN 7

So, the PID routine must be bypassing that.

EDIT: pin 7 is the first extruder heat pin, so it looks like this would have the fan wired in series to the heater. So it should come on whenever the hot end is on. How do you have the fan wired to the RAMBo, which connector?

[KaibutsuX]

I changed mine to pin 6 because my fan is plugged in to "Fan1" on the rambo. What does pin 7 actually correspond to on the RAMBO?

Code: Select all

/** The extruder cooler is a fan to cool the extruder when it is heating. If you turn the etxruder on, the fan goes on. */
#define EXT0_EXTRUDER_COOLER_PIN 6

[mhackney]

Pin 7 is Heater 1 pin - the hot end for what would normally be the 2nd hot end (the hot ends and fans are numbered starting with "0"). Pin 6 is assigned to Fan 1. There is a pin chart here: http://reprap.org/wiki/Rambo_development - use the pin numbers in the Arduino Pin Name column.

[KaibutsuX]

Thanks, that page is very helpful!

[KaibutsuX]

Wondering if anyone has any tips or insight for my PID tuning troubles, I have referenced http://forum.seemecnc.com/viewtopic.php ... led#p30587 and I'm using those PID settings as a guide. [P,I,D as 40, .55 and 35]

I started with EXT0_PID_INTEGRAL_DRIVE_MAX set to the default of 205. Ran the M303 S200 command and it failed with "Temerature to high". The heater did cut out at about 190 but the temp kept rising until it got to 225.

I tried again with EXT0_PID_INTEGRAL_DRIVE_MAX set to 175 and 150 and the results are exactly the same.

I have set EEPROM_MODE set to 0 to ensure my settings are actually coming from the firmware I'm editing and not stored in the eeprom. Am I adjusting the correct settings here? I see a EXT0_PID_MAX setting which is set to 255 but the comment above says "// maximum time the heater is can be switched on. Max = 255. Overridden if EEPROM activated." and I don't see any talk about adjusting this setting at: https://github.com/repetier/Repetier-Fi ... re-control

I am on FW0.91. My understanding of what's going on is that the heater is running full blast (limited by EXT0_PID_INTEGRAL_DRIVE_MAX) until the temp is within 10 degrees of target (200), but I'm guessing that the E3D resistor is fairly powerful and the head is so small that there's just so much residual heat once it turns off that it continues to rise up to 225 and that's what's ruining the autotune.

My next step is let it cool down again and retry with EXT0_PID_INTEGRAL_DRIVE_MAX set to 100 and keep going down until the tuning works. Am I on the right track or am I doing something wrong?