Taz 6 PID autotune vs. fan cooling

I’m running into a bit of an issue with my Taz 6 and keeping consistent heating. I’m running an SE 0.5mm toolhead, and overall it’s working great with PLA (200C). I went and started printing some PETg t-glase (230C), and I noticed the heating was all over the place on the hot end. It was bad enough that a print wouldn’t start since the temp couldn’t stabilize.

I went through learning about PID autotuning, and found a setting I could add to my printer profile’s g-code to get the PID nice and tight. Prints are consistent, all prints start properly, etc. However…

I’m noticing that after starting my prints, once I get off the first layer, the slicer (Cura) has the fan kick on for the material. That’s when my hot end temp can drop up to 10C, and it never gets back to target temp. In fact, it bounces around ±8C at least. It still prints ok, but this is something I’m not sure how to account for in my PID autotune.

LB support was really great when I thought this was a toolhead problem with helping me through some of this. I did turn off the fan for the PETg since it’s such a hot material, and the hot end temps were nice and tight. However, back to PLA with my autotune, and after the first layer, things go nuts again.

I’m attaching a screenshot of the temp curve. This is with PLA. I’m hoping anyone has suggestions on how to have a good PID autotune that also accounts for when the fans kick off past the first layer.

Any input or help is greatly appreciated.

Can you copy paste what this command was? Does your start gcode already have an M301 command in it? When you did your PID autotune, did you save it?

Since you have Octoprint, try these commands and see if the problem goes away

M303 E0 C8 S220 U1

You can additionally take the PID values output from the M303 command and craft them into an M301 command you place in your start gcode.

Some schools of thought have you turning the fan on while doing the PID autotune. I got some E3D silicone socks instead.

I run PrusaSlicer, so I did a PID autotune with my nozzle near the bed with the bed at 60c and fan on 100%. I wrote those values down for use with the M301 command.

I did a second PID autotune with the bed at 85c and the nozzle about 5mm off the bed, without the fan on. I wrote those values down as well for use with the M301 command.

Prusaslicer lets you do some basic if-then statements, so I put the saved PID values into the beginning of my startup GCODE.

;This G-Code has been generated specifically for a highly modified Taz6
{if filament_type[current_extruder]=="PLA"} M301 Pxxx Ixxx Dxxx ;pid settings for PLA
{elsif filament_type[current_extruder]=="PETG"} M301 Pxxx Ixxx Dxxx ;pid settings for PETG
{elsif filament_type[current_extruder]=="ABS"} M301 Pxxx Ixxx Dxxx ;pid settings for ABS
{else};no filament-specific PID settings used

Then the rest of the startup gcode was done as normal below that.

If you don’t want to use Prusaslicer, you can set up different “machines” in curaLE and have a Taz6-PLA, Taz6-PETG, Taz6-ABS, etc. and put the M301 into the startup GCODE for each of those.

That said, silicone sock definitely helps with stability when the fans kick on.

Thanks for the reply here! I appreciate the help.

I did a PID autotune by running:

M303 E0 S230 C8

Since I was targeting the PETg material, which printed at 240C, I picked 230C.

I let the hot end cool down completely and ran that again two more times. The resulting PID values were all somewhat close, so I took the one in the middle.

I added these into my g-code for the printer profile during startup with the M301 command. I didn’t commit them to the EEPROM with M500 since it wasn’t the same settings the autotune spit out for 200C as the target (for PLA).

I did try turning the fan down in the slicer, and it improved things. But, I ordered some silicone socks and am going to give these a try. Now I’m at the mercy of the postal service to deliver them…

Thanks for the reply!

I like the idea of having the different profiles with the different PID values if I find I need them.

I’m going to try the socks once I get them in the mail. Thanks for the additional nod to using those!

Yes, that’s one of my minor complaints with Lulzbot is the E3D and Slice hotends do not come with the silicone socks. I mean, if you buy an E3D Aero, it comes with it. Someone has a drawer full of these things somewhere :slight_smile: Slice used to charge $10 for theirs but they now include accessories.

And yes, for PID, they really do help.