Designing an Experiment for TAZ 5 heated bed

I am working on an experiment to determine how variable your print’s quality will be based on where it is on the printing bed. We have a few of these printers at my university and over time they have started to show some issues with certain areas of the bed. I am conducting a research project to identify whether or not the location on the bed where the print takes place is of concern.

We have 3 TAZ 5’s and at this point I need to develop three levels for my analysis. For these levels I will need to figure out how variable the temperature across the bed can be based on the input temp and break the 300 x 300 mm plate into 3 distinct areas where the temperature would be noticeably different. I know the plate is Borosilicate glass and I have found the thermal conductivity for the material, however I am assuming the heater is designed to be extremely uniform with the grid like pattern.

As I have researched information on the plate but I cannot find how the plate is heated. I have found the heating element available on the lulzbot site but is the heating through the grid channels totally uniform? I am assuming it is hard to heat up a rectangle uniformly, that’s why pizzas are round.

There is an infrared image of the taz heated bed that shows the conductor pattern pretty well floating around somewhere in Google Image search. It’s basically a series of concentric rectangles, with no heater loop right at the cable connection point. The middle does tend to be hotter on a glass bed. an aluminum bed will heat more evenly to the edge. Images of that in infrared exist in this forum.

The other issue you will see is the apparent hump in the bed center. It is actually flat, but the droop due to gravity of the extruder and the bed results in an apparent high spot. The fixed is stronger rods or boxed rails. Without modifications though, your adhesion success will be lower at the edges than the center.

Thanks for the input!
I found som GIFS of heat up ans steady state.

Yup, that’s the bed pattern.