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Cant auto tune PID settings, Help!

PostPosted: 2016-Sep-Thu-19-Sep
by Pandariot779
after i installed my e3dv6 and flashed the firm ware my printer wont run PID auto tune correctly.

i see when i run M303 E0 S210 C8 it will do a M105 but then disconnect from the printer.

I am stump to what is going on

I changed thermisters and still get the issue

When i do a test calibration print, the hot end's temperature will dramatically drop mid print and a cold extrustion prevented message would pop up.

I think it has to with the firm ware but i am not sure what to change.

Thank you!

Re: Cant auto tune PID settings, Help!

PostPosted: 2016-Sep-Thu-20-Sep
by frankv
My first guess is that you have an intermittent short in your nozzle heater wires.... Whether the short exists or not is probably dependent on the flexing of the wires which is in turn dependent on the head position.

When the short exists AND the heater on (e.g. as part of the PID tune), all the power goes through the short, and none goes through your controller, which dies, giving comms faults, etc.

a) When the printer *is* working correctly, try wiggling the nozzle heater wires and see if it dies.
b) Inspect the wires, especially close to the nozzle. Even a single fine wire broken out from the rest can cause this.
c) Once you've found and fixed it, anchor the wire bundle *rigidly* to the head/hot-end... all flexing needs to happen in the long bundle between hot-end and base.

Re: Cant auto tune PID settings, Help!

PostPosted: 2016-Sep-Thu-21-Sep
by RetireeJay
+1 on FrankV's suggestion.

Another possibility is an open circuit in your thermistor wires. An open circuit looks like zero degrees (corresponding to what you see in the calibration print). It could be as simple as a connector that's not fully seated, or it could be wires that have fatigue failure, or it could be a bad mechanical splice where the wires from the thermistor bead are joined to copper wires going to the nearest connector. When the firmware sees zero degrees, it assumes (correctly) that there's a fault and that it's not reading the temperature of the hot end correctly. It immediately shuts off power to the hot end (and heated bed) and then goes into an emergency stop - which blocks further communication with the host computer until the printer is rebooted.

Wires can fail due to fatigue when they are repeatedly bent back and forth at a single point. You can easily test this by monitoring the temperature (even room temperature) and wiggling the wires wherever they get subjected to sharp bends. I'm a big believer in cable chain to reduce fatigue failures.