What’s the design goal for bed temp control accuracy and uniformity? Once the temp controller signals that the temp has hit the commanded value, is there any need to allow additional time for achieving uniformity?
What should I expect near the bed edges? Obviously you don’t want to print to the physical edge, but what’s the design goal for how close you can get in practice?
I’m having trouble with warping/lifting/curl-up that seems to increase away from the bed center. Beginning to suspect the bed is reasonably well-regulated, on-temp near center, but significantly cooler away from the center. My cheapo, +/- 5C non-contact infrared thermometer seems to agree.
The TAZ 2 bed should be able to heat well, and rather evenly. Does one side of the bed feel cooler than the other? Mind taking some resistance measurements? With the printer turned off and unplugged disconnect the heat bed from the wiring harness and test the bed for the proper resistance. The smaller wires are for the thermistor and should read ~100k at room temperature. The larger connectors are for the heated bed heater coils and should read between ~0.8 Ohm.
You didn’t complete your thought with the upper range of the heater’s expected resistance value…
I’m not a particularly good judge of temperature, but --as I said-- I ran some checks with a non-contact infrared thermometer, a Ryobi IR001 (https://www.ryobitools.com/power-tools/products/details/360) , starting at bed center and running outward. Near the center, the heating looked on-target and reasonably stable. That seems to indicate that the sensor is working. However, I saw temperatures up to 20C lower near the edge.
It is possible that such a thermometer is a totally unsuitable device. Handheld, it’s pretty shaky. Possibly the PET film covering the bed interferes. What is the official way validating correct (vs commanded) and uniform bed temperature?
From a quick eyeball of the installed bed, it looks like the heater is firmly bonded to the underside and covers it from very near edge-to-edge, so I’d expect very uniform temperatures. Could there be thermal bonding difficulties on my unit?
Since I did not have actual timings I didn’t add to my report: bed heating seemed to take more and more time, now far more than I expect. Maybe that’s consistent with a failing bed heater, too.