troubleshooting extruder heater

[lasermike]

for those of us who are not electronics wizards. is there a good troubleshooting guide or video on testing and troubleshooting heater problems. my extruder is no longer heating up on my orion and need a good place to start.

[Eaglezsoar]

See this thread for basic troubleshooting - http://forum.seemecnc.com/viewtopic.php?f=54&t=995

[lasermike]

ok, replaced fuses and new thermocouple. it is heating up, but now for any print the extruder stops heating 3 degrees short of the set temp and the print never starts. i have tried changing my extruder temp from 235 (it stopped at 232) down to 225 (it then stopped at 222). i dropped to 220, it stops at 217.

any thoughts. i have also tried changing to Matterhackers from Repitier and get the same issue.

[Nylocke]

Likely your PID tuning is off. Try running M303 S200 C8 and changing the EEPROM values for the PID to what it shows when the tuning is done.

[teoman]

Your I setting on the pid controller is too low.

P = proportional
I = integral
D = derivative


These are all relative to the error. So, if you are at 40 degs and you set it to 200 degs your error is 160 degs. So your controller is outputting P x 160 amount of power.
But the problem is with only P you will never reach your setpoint. The more you approach setpoint it the less it outputs. I.e. if you are at 227 and you want it to reach 230 you are outputting P x 3 which is not enough power to raise the temperature.

The I component of the controller is the integral component. Its purpose is to compensate for lack of the proportional component close to the setpoint. What it basically does is (from the previous example our error was 3 degs) it constantly adds up that error I x 3 and in the next round I x 6 and the Ix 9 ... etc untill it is large enough to make a change in the actual temperature. And untill the error reaches 0.

So you need to increase the multiplier to help the integral component a little.

The D component is to prevent overshoots but that is not really important in this case.

[lasermike]

So is it normal when i run the pid auto tune my new averages are significantly higher than the original set points. original P = 15.91 new average is 56.16 original I = .75 new average is 5.93 original D = 84.02 new average is 134.46.

i ran auto tune again and got even higher averages.

[KAS]

Was it replaced with the exact same thermistor or a different one from a different manufacture?

[lasermike]

i am pretty sure it was an extra that i had from see me cnc, so it should have been the same. cannot guarantee it though

[lasermike]

with the new numbers it takes longer to get there, and now stops about 10 degrees low. have played with the I value bumping it up, nothing. went back to original settings still nothing. i can set to preheat abs and it holds to the set point no problem.

[JFettig]

Its weird, I just dealt with mine, now I have dual extruders and the right one heats up perfectly, left one stops 5-10c short every time. auto tune PID 100 times those values just won't do the trick, I started modifying PID values a bit, worked for a print and now it still has issues for some reason.

[lasermike]

I found i can cheat it, by adding 10 degrees to my desired set point for the extruder, when it gets about 10 degrees away from hitting the set point i stop the extruder fan for about 15 seconds. this lets the extruder heat up to the set point and it starts printing. put the fan back on and it will continue to run but still 10 degrees lower than the set point.

[geneb]

lasermike, you might want to put a layer of Kapton around the metal barrel of the heater block. That might help keep the PEEK fan from robbing heat from the hot end.

g.

[lasermike]

will give that a try. it is printing now, but i have unplugged the fan (for my abs printing)