Hotend Temp Fluctuation

[JeremyAgost]

Hi all. Can anyone explain this?
[youtube]http://www.youtube.com/watch?v=OWO9iwO4ysI[/youtube]

I've got an E3D v6 on my ORION. While printing the hotend temperature fluctuates up and down, +/- 20ºC of the set point. It stays perfectly stable while idle and I've done PID tuning several times. When heating it doesn't go far over the set point, so the tuning seems good. While it's idle I've tried playing with the leads to the thermistor to see if I could get it to fluctuate from cable strain but it stays stable. Any thoughts? Is it really heating and cooling that quickly? The EEPROM setting for Extr. 1 Heat Manager is #1, which is PID as far as I know.

[Earthbound]

The values you are seeing are not real temperature fluctuations. The thermal mass of a hot end won't heat/cool that fast. There must be an issue with the thermistor, its wiring, connection to the control board, or the board itself. Since you've said the value only fluctuates when printing, I would suspect a bad connection at/near the hot end first. When you swapped in the E3Dv6, did you add a JST plug or other means to easily disconnect the thermistor? If so, I'd suggest making up a jumper cable to temporarily bypass the thermistor wiring in the main umbilical. Use jumper to connect thermistor to control board and see if problem goes away. If not, next most likely culprit is the thermistor itself.

[gestalt73]

Hey Jeremy,

You're going to love your V6, once you get everything dialed in.

+1 for Earthbound's suggestions. triple check every connection, crimp, barrel connector, whatever you used to hook up that new thermistor.
Also, the new thermister mounting system is kinda awesome, just make sure the thermistor is firmly fastened to the block and isn't flopping around inside, you used the fiberglass insulating sleeve, and it's not shorting out from any exposed sections of thermistor wiring.

Try the wiggle test to zero in on the problem. take the hotend temp up to 180c or so, and start wiggling around the wire along every section and connection until you can recreate the issue. I'll bet that the temperature is steady when the hot end is holding still, right?

There's no way the hotend is changing temperature that fast.

Once you have that straightened out, there are a few more things you'll most likely have to do, to really dial it in:
- update your thermister type, not sure if in eeprom or in firmware. I'm pretty sure the Orion uses a different thermistor in their stock hot end, right?
- try running pid autotune, but i've heard from alot of people that the autotune values aren't sane for the 40w heater cartridge. you may need to hand tune if you're still seeing +/- fluctuations. Once everything is dialed in, you should be within about +/-0.5c of your target temperature.

[Polygonhell]

Agree with Earthbound, not an actual temperature change, most likely lose/bad wiring on the thermistor.

[RegB]

Air gap between the thermistor and the "block".
Sometimes the thermistor touches hot aluminum, sometimes it floats around in warm air, movement of the head stimulates the effect.
I know the copper laden goop is recommended for the standard build hot end, but I figured "why NOT ?" for the E3V6.

I get fluctuations, but they are much smaller than that, biggest swing is when it starts feeding filament FAST or stops feeding - much as expected.