The damper is a re-circulating air system inside the oven. When the arm cycles into the
oven an analog timer is powered and starts counting down, when it zeros out it sends power
to a solenoid valve that controls an air cylinder to open the damper.
You have to remember this is a convecting oven, with the damper closed the re-circulating
blower is starved for air, this holds the heat in the burn chamber so the oven loses less
heat when the machine cycles from station to station. Once the oven doors close and the
timer zeros the damper opens flushing more oven air through the burn chamber, this makes
the air hotter and more turbulent in the oven, cooking the molds faster.
I hope that helps to explain it.