Temperature overshoot issue

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pcenginefx
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Temperature overshoot issue

Post by pcenginefx » Sun Nov 29, 2015 8:26 pm

Hi all,

So this has been bugging me for awhile now - in S3D (I'm using v3.0.1) when I go to pre-heat my extruder on my M2 (now using v4 extruder, but this also repros on my other M2 w/3b extruder), it always overshoots the target temp by 5 degrees then has to cool back down. I assume it has to do with something in the FW, but I'm very hands-off when it comes to the FW, so if anyone has an easy to follow fix I'd appreciate it - thanks!
//Aaron
3D Print Services | www.3dhubs.com/seattle/hubs/aaron

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Jules
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Re: Temperature overshoot issue

Post by Jules » Sun Nov 29, 2015 9:19 pm

It's supposed to do that. (And there is probably some way to mess with some setting to keep it from overshooting by quite so much (PID settings or something), but it's the way the program is written. :)

swbluto
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Re: Temperature overshoot issue

Post by swbluto » Sun Nov 29, 2015 10:08 pm

Yeah, it's supposed to do that. The way to diminish the overshooting is by increasing the dampening factor in the PID control loop (Essentially slow down how quickly it heats up). One way to possibly fix this is by modifying the G-code (Instead of going straight from 20 to 230, go to 225, and then 230.), but that's not an option available in S3D.

Actually, I wonder if you did...

"Layer 1 225"
"Layer 1 230"

If it would do just that? MIght be worth experimenting.

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pcenginefx
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Re: Temperature overshoot issue

Post by pcenginefx » Mon Nov 30, 2015 2:10 am

If this was supposed to do that, then how come it didn't do that before? I've not had this issue until around the time I upgraded to S3D 3.0 (just haven't got around to asking for help about it till now).
//Aaron
3D Print Services | www.3dhubs.com/seattle/hubs/aaron

swbluto
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Re: Temperature overshoot issue

Post by swbluto » Mon Nov 30, 2015 2:15 am

pcenginefx wrote:If this was supposed to do that, then how come it didn't do that before?


Because in previous versions it heated up slower? That's the thing about PID control loops, there's a tradeoff between overshoot and the ramping speed.

See this image from wikipedia for a basic understanding.

Image

Granted, I'm pretty sure a sophisticated enough algorithm could heat up quickly without overshooting that much, but that's not true of simple PID algorithms which is what I'm guessing S3D is using.

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pcenginefx
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Re: Temperature overshoot issue <SOLVED>

Post by pcenginefx » Mon Nov 30, 2015 2:45 am

So then it sounds like it could be a bug with S3D 3.0+ since it didn't occur before upgrading to that version. I'll take a look over on their forums to see if they have any solutions to this issue. Thanks!
//Aaron
3D Print Services | www.3dhubs.com/seattle/hubs/aaron

jsc
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Re: Temperature overshoot issue

Post by jsc » Mon Nov 30, 2015 3:04 am

You can run a PID autotune to dial in the parameters for your preferred temperatures. Details are here: http://reprap.org/wiki/PID_Tuning

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jimc
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Re: Temperature overshoot issue

Post by jimc » Mon Nov 30, 2015 3:51 am

yes it has nothing to do with s3d. its all your pid. run the autotune sequence like jin said. every heater cartridge and the temp at which you are printing are a little different so the stock pid values in the fw get you close. even when it is tuned though 5 deg overshoot aint bad. I would consider that tuned pretty well. 20 deg overshoot or if it has trouble keeping things steady within a deg or two while printing then that's a different story.

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pcenginefx
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Re: Temperature overshoot issue

Post by pcenginefx » Mon Nov 30, 2015 10:37 pm

Thanks for the info! Will try this tonight to see if it fixes both my printers.
//Aaron
3D Print Services | www.3dhubs.com/seattle/hubs/aaron

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