1 Topic by pirvan

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Topic: Bed heater problems

Once again, I'm having print bed heater problems.

Last time I had a problem with the heater not going above 50°C.  At that time, I did a quick test by plugging the printbed into the hot end port and the bed heated fine, so I replaced the MOSFET driver, but it didn't make any difference.

So I decided to upgrade.  I installed a QU-BD heater pad, and upgraded to a 750W power supply to drive it all.  Everything worked OK, until a couple of days ago.

Prior to this past Monday, the QU-BD bed would heat up to 100°C in about 3.5-4 minutes.  Now it quickly heats up to 60°+ (sometimes higher), then it drops off below 50°, and then slowly creeps upwards, but tops out around 60-65°.

I know it's not the heater pad itself, because I once again plugged it into the hot end port, and it vent straight to 100°C in a little over 3 minutes.  After I plugged it back in its own port, the bed heated up to it's normal 100°C and stayed there, so I thought the "glitch" was gone, but last night it stared doing it again.  Now I get the temp curve you see below, and the temps eventually build up to about 63°C and stay there.

So do you guys think the problem could be?

http://www.soliforum.com/misc.php?action=pun_attachment&item=3947

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To print or, 3D print, that is the question...
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2 Reply by 2n2r5

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Re: Bed heater problems

have you tried enabling Bed PID and then autotuning ?

SD3 w/ mods:
Glass bed with QU-BD heat pad upgrade, threadless ballscrew w/ 8mm smooth rod, spectra line belt replacement, lawsy MK5 extruder, Lawsy replacement carriage, E3D hotend, Ramps 1.4 w/ reprap discount controller, DRV8825 drivers, 12v 30A PS, Acrylic case, Overkill Y-idlers, Filament alarm, Extruder fan + more.

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3 Reply by pirvan

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Re: Bed heater problems

No I haven't.  How do you do that?

FYI, on my setup, I'm still using the original thermistor, rather than the thermistor that came with the QU-BD.  I found that it's actually pretty accurate.  The thermistor readings are usually only 6-8°C higher than the actual measured temps.

To print or, 3D print, that is the question...
SD3 printer w/too many mods,  Printrbot Simple Maker Ed.,  FormLabs Form 1+
AnyCubic Photon, Shining 3D EinScan-S & Atlas 3D scanners...
...and too much time on my hands.

4 Reply by adrian

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Re: Bed heater problems

Your heater mosfet is going bad... try cooling it more by moving the fan closer or hitting it with a freezer can...

5 Reply by pirvan

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Re: Bed heater problems

I just connected the heatpad directly to a 12V supply, and here is the result.  To me, this looks like the heatpad's gone bad.

http://www.soliforum.com/misc.php?action=pun_attachment&item=3950

What do you think?

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6 Reply by 2n2r5 (edited by 2n2r5 2013-11-14 15:18:30)

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Re: Bed heater problems

See any burn marks on the pad? What's the resistance of the bed now?

SD3 w/ mods:
Glass bed with QU-BD heat pad upgrade, threadless ballscrew w/ 8mm smooth rod, spectra line belt replacement, lawsy MK5 extruder, Lawsy replacement carriage, E3D hotend, Ramps 1.4 w/ reprap discount controller, DRV8825 drivers, 12v 30A PS, Acrylic case, Overkill Y-idlers, Filament alarm, Extruder fan + more.

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7 Reply by pirvan

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Re: Bed heater problems

I can't see anything.  The heaterpad is under the insulation cloth, and everything is wrapped in Kapton.

What should the resistance of the pad be?  It currently reads 4.8 ohms.

To print or, 3D print, that is the question...
SD3 printer w/too many mods,  Printrbot Simple Maker Ed.,  FormLabs Form 1+
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8 Reply by elmoret

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Re: Bed heater problems

pirvan wrote:

I can't see anything.  The heaterpad is under the insulation cloth, and everything is wrapped in Kapton.

What should the resistance of the pad be?  It currently reads 4.8 ohms.

P=V^2/R

144/4.8=30

That ain't gonna cut the mustard. Time for a new bed!

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9 Reply by pirvan

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Re: Bed heater problems

Has anyone else experienced this problem?  The Qu-Bd  heater pad is only 2 months old, what do you think it would cause it to go bad in this short a time?

Anyway, today I ordered a replacement from Qu-Bd, and while I was in a buying mood, I also bought the solid copper plate that I've been meaning to use as a replacement for my aluminum build platform, and I also ordered the new Aluminum bed frame from Solidoodle.

So now I wait....

...but the short life span of the qu-bd heater still bugs me.

To print or, 3D print, that is the question...
SD3 printer w/too many mods,  Printrbot Simple Maker Ed.,  FormLabs Form 1+
AnyCubic Photon, Shining 3D EinScan-S & Atlas 3D scanners...
...and too much time on my hands.

10 Reply by elmoret

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Re: Bed heater problems

Haven't had a qu-bd bed fail, but I haven't used one either.

This stuff is largely out of China, with questionable QC. That's why I sourced the heaters for the Filastruder out of North America. I've just heard of the first failure today, out of 900 units shipped. It is on its way to me to be dissected. smile

Filastruder - the robust, inexpensive filament extruder
E3Dv6 All Metal Hotend - the premier 3D printing hotend