#Heated bed consistently throws 'not heating at expected rate' around 90c-100c

1 messages · Page 1 of 1 (latest)

paper oriole
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It's pretty consistent from room temperature. When the fault occurs, it does still look like the temperature going up just slowly. If I restart it after the fault, it usually is able to reach and hold the target of 110c without issue. Any ideas what could be causing this?
Here are some more details:

  • There is no obvious wackiness in the graph, it looks nice and smooth.
  • I would assume it's not the thermal fuse, as it does still heat up.
  • There is no thermostat on this heater pad.
  • I see no obvious signs of charring or bubbles.
  • There are no bed fans, Hotend & part fans are off, Chamber doors are closed and the chamber is insulated.
  • Max Power is set to 0.5. This has not been changed since I built the printer.
  • All [verify_heater] parameters are @ defaults.
blissful willow
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set max power to 1, re pid tune, and see what she does

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i dont know what ssr you have, but max power 1 is 100% safe for the build plate

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if you want you can walk it up by .1 but 1 is just fine and wont taco anything

paper oriole
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I'm not too worried about tacoing TBH, I just never got around to raising it. Never seemed like a big deal since I wait so long for the chamber to heat up anyways.

I believe you're right that raising the max_power would prevent the faults from happening right now. But it doesn't seem like it would identify the root cause, since it as worked fine at 0.5 for years.

blissful willow
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it is odd. is it seasonal by chance? ie its generally colder outside now?

paper oriole
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It is a fair bit colder, yeah. Although I just checked the room temp and it's 80f

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Oh and as for the SSR, it's an Omron G3NA-210B-DC5-24.

blissful willow
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i believe that one is ok

latent canyon
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Could you measure resistance of the heating pad?

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Or power consumption if you have current meter

spice reef
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I had a similar problem and it turned out to be a failing thermal fuse. You might want to measure the resistance.

paper oriole
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Thanks for the advice. I’ll look at that

karmic vessel
spice reef
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Should be really small

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I dont recall what I measured, but should be < 1ohm

karmic vessel
latent canyon
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Event it is small change in 2 times enough to have those issues you describe. So please provide heater expected power and voltage you applies to it

karmic vessel
# latent canyon Depends on the power of heating pad, what nominal power of yours?

i'm using a 650W (120V, US. 350m trident formbot kit). I've run into this same abnormal heating issue recently so this thread has been very helpful. My printer is in the garage and it's significantly colder out there now (50F or so). My main hair pullling excercise was trying to determine what threshold my heater was running afoul of(finding the verify_heater klipper config answered that question). It's actually heating but falling outside of that 60 second sliding window for the 2C rise. I'm also using the stock 0.6 max power on the heater which is something i'm going to adjust to 0.75 and retune my PID settings. While Im down, i wanted to verify that fuse is still functional to rule that out. all of this has been great info.

karmic vessel
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I'm not so convinced my problem is the colder garage temp. I managed to make this plot from the klippy.log and the odd change in temp rise seems consistent near the end both times.

graph.png
blissful pebble
karmic vessel
blissful pebble
lilac maple
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Be careful not to overload your SSR past its rating... Look up the datasheet to see max current for its operating environment.

latent canyon
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If it more like 2 times then smth off with pad if not then try to set pwm cycle to 1

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Also does your pas has build in thermostat, if yes it also could be a problem

karmic vessel
karmic vessel
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curiously this morning with the printer idle, i have noticed that the bed heater thermistor bounces around a full 1C. I find this odd since it's enclosed. Not sure that's exactly normal

latent canyon