Heat Fluctuation

[sfuelberth]

So I have noticed that sometimes the bed and the hotend will tend to not hold the set values, well they drift down more than 5°C. I realize there would be some fluctuation however it seems like it should possible stay closer to where set. I have started aiming things about 5°C more than I want figuring that the hotend and bed won't keep up. Am I paranoid about this or is this normal, my other printer seems to stay closer to the set temp. I don't have an enclosure, I am running everything stock besides an added light ring at the moment. Is there something I can do to make this stay at the set temp better? I mean I will probably buy some PEI for the plate, then the bed wont have to be run or at a lower temp. I am printing PLA/PHA Thanks.

[sfuelberth]

I kind of figure I need to build an enclosure if I want better temp control correct?

[IMBoring25]

Does Octoprint give you a PID output history? If the controller is pulling the PID, you just need to tweak the PID values so it holds setpoint. If the PID history shows 100% all the way across, you need to look for bad (high-resistance) connections somewhere in the bed and hot end power wiring or check the power supply output.

I'm not crazy about that short-period oscillation either. You may have intermittently loose connections in the thermistor wiring as well.

[sfuelberth]

I don't have a PID output history and I doesn't look like there is one in the plugin repository. I guess I could look at making one though. Or is there already some tool that would do that for me? I have previously measure the voltage at the Rambo going to the hotend at 12.2 V, so I think that seems fine.

This hotend was built by SeeMeCNC so I am really hoping the wiring is solid there. The I can modify the PID settings though I am not quite sure what the acceptable ranges are for the hotend. Would invalid (if it's even possible) damage anything, I assume the potential exists. I did try and autotune the hotend but the PID values I got out did not work at all, and were nowhere near what the stock firmware comes with.

Thanks

[Xenocrates]

It honestly looks like a PID tuning issue, where the autotune was satisfied because due to the initial overshoot of most loops, it held an acceptable temperature for long enough for it to be happy. I might play with the I parameter a bit, see if twiddling it helps any. Note that a smaller I is more powerful in many implementations.

[sfuelberth]

Thanks I am going through tuning the PID right now. i admit I have not gone through the firmware code yet but is there an autotune for the bed also? And actually I had forgotten that I had changed the PID values before and then wiped them out with the latest firmware upgrade. Thanks for the help.

[sfuelberth]

Alright i found the autotune for the bed: M303 P1 C8 S70

[sfuelberth]

Actually I think that the hotend plug is still wiggling loose slightly even with the retaining clip. I am going to have to look at modifying that part or coming up with a different solution.