Bonded Heat bed for 12"

[Chadd]

Cool demo of the problem (thx!).

2 questions:

1. What does "PID" refer to? (Sorry..., been puzzling on that...)
2. What is the table structure of the Mendel90 in the vids? What are its similarities to the MakerFarm wood+glass table?

1. To put it simple PID uses PWM to control your bed temp so it turns the bed on and off very quickly to maintain the temp vs turning the bed on 100% for 5 seconds at time to maintain the temp. The reason you have to have a Solid state relay is because a mechanical relay can't handle the quick on and off switching. In that video link what you are seeing is the bed distorting when it turns on @100% power and then returning to its normal position after the power is off to the bed. The second video shows the same thing with PID, the bed switches on and off quickly to maintain the temp so it doesn't stay on/off long enough to show the change in distortion.

http://techteach.no/kybsim/pwm_control/index.php

2. The bed designs are pretty well identical.