bratan wrote:printbed to take 10 minutes to warm up to 80C
Unfortunately, that's about right.
Unlike many printers, the M2 has a glass printing plate clamped atop an aluminum sheet with the heating pad bonded its the bottom. The combined mass of the two plates takes quite a while to heat up and the small air gap between the glass and aluminum is, unfortunately, a pretty good insulator.
You can add an insulating pad below the heater, but it really won't improve the results by very much.
If you have an old-old M2 with a 12 V heater, check the platform heater connections on the RAMBo board for overheating, because they were prone to cooking. Unplug the connectors and take a look inside to verify there's no corrosion or charring going on.
PID Autotune applies only to the
nozzle heater and won't do anything for the platform.