PID Autotune failed!- Temperature too high

[esbowman]

Super excited. I have this thing "finished." I have the printer built, connected, and working using Repetier Host .56 on OS X 10.6.8. I can move it manually using Repetier, and the Extruder > Heat On button works as well as the heated bed > Heat On button.

When running the M303 S200 command to start the autone on the extruder, I get the following:

< 2:21:01 AM: Info:PID Autotune start
< 2:22:29 AM: Error:PID Autotune failed! Temperature to high

That's the log I see in Repetier. I also tried M303 instead, and I received the same error. It doesn't smoke excessively, and seems to be fine but I'm not sure how to get this PID autotune to work. Is the autotune 100% necessary?

BTW, the autotune for the bed finished with no problems.

[geolupulus]

I just built a Rostock v2 and had this issue a couple days ago when I did the autotune. I'd say the autotune is necessary so that the hot end can reliably hit and maintain your target temperature with little temperature fluctuation. I changed the extruder PID max from 255 to 128 in the EEPROM and that solved it for me. Hope that helps!

[esbowman]

Thanks for the reply. I'll try something similar and see if that works.

[geolupulus]

Okay, so to get the autotune to succeed and not get the temp too high error, I stand by my advice, you'll have to turn down the 'Extr. 1 PID max value [0-255]' to avoid an overshoot in temperature.

HOWEVER

When you get your PEEK fan installed, your hot end will not have enough power to reach target temps due to the air flow running across it. This is when you can bring your 'Extr. 1 PID max value [0-255]' back up. You'll have to do another autotune then anyway.

[esbowman]

I was just getting ready to reply with a huge THANK YOU!!!

I was able to get it to autotune after using your advice. Printing my fan shroud now. I'm like a fat kid in a cake factory right now. Lol.

Thanks again!

[geolupulus]

Glad I could help!
Just don't forget to bring the PID Max Value back up to 255 when the PEEK fan is running! I ran autotune without raising the Max value back up and the hotend could only get up to ~160C.

[esbowman]

Thanks again. Will do.

Now I'm battling with ABS not sticking to the glass. Tried an off brand glue stick first. Got about 50% into the shroud print then it broke loose and went nuts. Then I bought a name brand Elmer stick and that failed too. Right now I'm using Aquanet hairspray. So far it seems to be doing better than the first two attempts. Fingers crossed.

[geolupulus]

Is your Z zero too high off the build plate? Have you calibrated? Is your heated bed hot enough?

[esbowman]

Yes I have calibrated a number of times to get it as close as possible, and I don't believe the Z height was too far off the base. I used Gunau's advice here after trying the calibration procedure in the manual: http://forum.seemecnc.com/viewtopic.php ... 985#p36589

For some reason I had issues with the calibration outlined in the manual, but Gunau's advice got me pretty darn close...I think.

Secondly, the extruder was set to 225C and the bed was set to 95C.

Finally, the Aquanet worked great. Probably some layer alignment issues to work on now, but you tell me what you think. I did just notice that the nut holding the extruder, right above the melamine spacer, was loose. I think I just hand tightened that originally when building the printer, as I was afraid to damage anything. I just now tightened that up snug with a wrench and expect that will get rid of some of the layer alignment issues.

Here's the print. Note: It might not look 100% flat on the bottom, or look warped, but it's not...the fan is protruding out of the bottom just a bit causing it to lean. The fan went in with no filing required too. It's snug, but I expect that's intended.

Fan installed

I added another topic about the print here: http://forum.seemecnc.com/viewtopic.php?f=77&t=5233

Thanks again for all the guidance so far man! I appreciate it.

[geolupulus]

Hey I'm just trying to figure all this out too man! I'm glad you figured out the adhesion issue. Thanks for the link to Guanu's calibration technique, I will definitely recalibrate using that when I get a chance. It makes a little more sense than the assembly manual did to me. When I was working on the hot end last night to install the fans I too realized that I had the same thing going on with the nut that attaches the hotend to the effector platform. Your PEEK fan shroud looks awesome! I have been having issues with the heated bed (only can get up to 60C or so) so my ABS prints aren't coming out nearly as nice as yours. I had to file the shroud quite a bit due to warping. Once I switched to PLA I saw a nice increase in quality.

[esbowman]

I wish I had help for you on the heat bed issue. Mine takes quite a bit of time to reach 90, but it will go beyond that if I'm not impatient.

I've had it set to 90C for this layer fan shroud, and it's looking great so far. Almost undetectable layer misalignment issues now that I've tightened the nut above the extruder. Duh. Can't believe I didn't check that before the first print.

[geolupulus]

Upon tightening that nut I noticed the extruder was too high and had to recalibrate using Guanu's method this time, much faster. Thanks for the tip!

[esbowman]

No problem. Glad it helped.

[DonFL]

I just built a Rostock v2 and had this issue a couple days ago when I did the autotune. I'd say the autotune is necessary so that the hot end can reliably hit and maintain your target temperature with little temperature fluctuation. I changed the extruder PID max from 255 to 128 in the EEPROM and that solved it for me. Hope that helps!

That recommendation fixed this same problem for me also. I was seeing temp readings in the 215 range, then a failure. Once I dropped the max to 128, it worked like a charm. Thank you!

[Brazz]

Glad I could help!
Just don't forget to bring the PID Max Value back up to 255 when the PEEK fan is running! I ran autotune without raising the Max value back up and the hotend could only get up to ~160C.

Thanks so much Geolupulus. I was pulling out my hair after messing up my PID hot end values. I could no longer get my hot end to go above 115 and it seemed to not really care to heat up at all, despite being set to 235. Your post caused me to look at my PID Max Value and sure enough it was only set at 134. I changed it to 238 and wham bam I'm heating up quickly again. Not sure how that got messed up but I'm back in business.

*Update: Short of writing a full thread on my experience with figuring out that my resistors had burnt out on my hot-end, I'll first post to clear up my confusion from this post. Somehow, changing my PID Max milked another day of life from my failing hot-end. That said, the next day, it had the same issue of not being able to heat above 165 or so. I ordered 2 more resistors from SeeMeCNC, changed them out per the initial build instructions, and am back to printing daily.

TL/DR: If you're having problems even getting to temperature, even having issues getting to 235 and are instead only getting 230 when set to 235, your resistors are shot and need replacing.

-Brazz