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This morning I was printing out something pretty small to give away at work. About layer 6 into a 9 layer print, I noticed that my hot bed was around 4-5 deg hotter than what I had it set. I touched the hot bed around the side, and it was way colder than what it was reading. I noticed that I put the print right on top of where the temp sensor is located. My guess is that the printed part was increasing the temp right at that spot, so it would cut power to the hot bed allow the rest of the hot bed to cool off.

I wonder if this is adding to my lifting issue for larger parts. If the part is big enough, then odds are it will land over the temp sensor. I guess I need to find another plate to help hold the heat an help prevent this from happening.

Has anyone else noticed this?

Shawn

if your using boro glass as your build surface there is a 10+ difference from center to the outside edges, glass does not heat the bed evenly.

The heating element has no idea how hot it is, it just runs until the thermistor reaches the right temp and tells it to turn off. This means that the heating element can be hotter than the sensor is until the heat flows through the board and spreads out enough to reach the sensor... Because of this, the thermistor's reading can raise slightly after the heater has been turned off. It might still need to "catch up", and this is probably what you're observing.

Tuning in the PID will help stabilize this.

I am using the glass plate. Thanks for the replys