Strange bed heater behavior

[vrenlos]

Hi all,

I've been dialing in my settings and really loving the printer so far. Tonight I went and started a PETG print and noticed that the heated bed hit the 70C target, stayed there for five minutes while printing, and then started to cool.

While it was dropping I tried setting the temp slightly lower and it just kept falling, but the thermistor was reading (what I assume to be) properly the whole way. Any thoughts on this one?

[DeltaCon]

Was the bed-heat LED lighting all that time? Also the Rambo has a LED that starts lighting when power is send to the bed, That way you can determine where it goes wrong. Does the Rambo stop giving the heating command, does the Rambo send out power, but the Onyx does not get it?

[vrenlos]

Thanks for the reply! I've had a massively busy few days at work so haven't had a chance to do much involving the printer :/

Anyhow, last night I powered it up and set the bed target to 70 and left it there for ~20 minutes with no issues. I'm wondering if my original problem may have been due to having accessed Octoprint from a second PC while the print had been going originally? My thought is that maybe in one of the browser interfaces the bed target was set to 0 and for some reason not updating on my laptop in the other room. I'll try printing again, hopefully tonight.

[moo77777]

The original part cooling fans put out an immense amount of air and can cool the bed. Check to see if they are turning on part way in to the print job

[vrenlos]

I finally got around to some printing last night and got this figured out - I had been only using three of the six swivel clips since they were all in a bit too tight, and I think this was causing an air gap between the onyx bed and glass. I gave the glass a good cleaning and set all six clips to a more appropriate tightness and the temp went from ping-ponging all over to rock solid behavior. Thanks for the input, all!