1 Topic by abruski (edited by abruski 2014-12-09 12:38:21)

  • abruski
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Topic: Bed thermal expansion bending "issue" discussion

While calibrating my bed (at 90° Celsius & extruder at 230° Celsius) I noticed that the bed bends downwards in the middle with ≈0.05mm. I suppose it could be even fluctuating or oscillating, but I suspect the latter. That is because glass expands when heated. This could be an engineering fault where no "wiggle" room was left for the glass to expand and thus it bends downwards. This means that loosening the bed a little would help.
PID tuning can help if luc's repetier supports it.

This is the temperature curve of the bed. I don't even know what to make of it.
h_ttp://i.imgur(dot)com/BT96oEB.png
Any help would be appreciated.

2 Reply by carl_m1968 (edited by carl_m1968 2014-12-09 18:31:31)

  • carl_m1968
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Re: Bed thermal expansion bending "issue" discussion

abruski wrote:

While calibrating my bed (at 90° Celsius & extruder at 230° Celsius) I noticed that the bed bends downwards in the middle with ≈0.05mm. I suppose it could be even fluctuating or oscillating, but I suspect the latter. That is because glass expands when heated. This could be an engineering fault where no "wiggle" room was left for the glass to expand and thus it bends downwards. This means that loosening the bed a little would help.
PID tuning can help if luc's repetier supports it.

This is the temperature curve of the bed. I don't even know what to make of it.
h_ttp://i.imgur(dot)com/BT96oEB.png
Any help would be appreciated.

Based on your curve I would have to say there is something wrong with your thermal management circuits. My 1.0 is all stock except the host and firmware which are both Repetier and as you can see by my curve it is fairly stable. It also looks like yours heats very slowly. Yours is at 30 minutes to set temp of 90 while it took mine 5 minutes to reach a set temp of 80. Based on that my guess is your heater is bad or the driver for the heater is bad.

http://i92.photobucket.com/albums/l5/solarenemy/tempcurve.jpg

Printing since 2009 and still love it!
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3 Reply by abruski

  • abruski
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Re: Bed thermal expansion bending "issue" discussion

It appears to be some external interference.
But the bed bending problem persists. As found on h_ttp://creatrtips.freeforums(dot)org/banding-pwm-and-pid-for-the-bed-heating-t129.html