Connected to the printer it so I could remove the filaments stacked on top to get at the guts. The software was still running, and had been running for the last 4 days. That is a good thing. Guess I don't have any memory leaks.

When I last disconnected, I was feeding filament to figure out why my one stepper was not pushing and hit the e-stop button to shut it down. What... you don't have an e-stop button?

So when I toggled the e-stop, it started feeding, which powered my mixer. As the hot-end was stone cold, with the mixer embedded in solid plastic, snap went the shaft. I hate it when I'm right. Adding the code to prevent this has moved up the list.

The good news is my heated bed works, well. Perhaps a little too well. I am fairly certain that the battery I used for testing was not delivering the required current. It was a flooded lead acid battery of sufficient size, and it did read 12.6v at the start, but I did not test the output voltage under load.

I held the leads to my power supply output to see if it would just shut down under the load. It had no issues supplying the current, with everything else powered. I continued to hold the leads there, and in about a minute my power supply had slowly turned into a jet engine.

A few minutes later the massive solid stone heated bed was at 70C, and my 8 gauge supply wires were slightly warm. If my leads are heating, I'm fairly certain my T-220 case style mosfet would pop under that kind of load. I'll add a couple more so they can share it.. Now I wonder where I'm going to get a thermal fuse rated at > 40A? I will not be running that, unattended.

I had put another round of furnace cement on the bottom, encapsulating some steel washers I had ground to level it out. The stone varied in thickness (on the back) by almost 2mm. I should have probably measured that earlier. So... I continued heating it up to 100C so I could cure the new cement.

With an IR thermometer, I measured the surface temp at various points. The center was the warmest, with the very edges down by about 10C. At 100C I'm probably getting convection cooling. The vast majority of the build surface varied by less than 2C. I'm calling a 2 percent deviation a success.