Blown film extrusion is a process requiring a high level of operator skill. Producing film to geometric specification requires a good understanding of the dependence of bubble dimensions on the interrelationship of process variables. Dimensions include film thickness, bubble diameter, and frost line height. Process variables for controlling these dimensions include screw speed, nip speed, cooling air speed, and bubble air volume. An experienced operator understands that changing any one variable will affect all three dimensions, and understands the change that will result. A highly realistic blown film extrusion simulator has been used to elucidate these interrelationships for all personnel.