A system for generating a response curve for adjusting the positions of a pair of adjustable edge seals to the width of a print medium in a printing system is disclosed. The system comprises a vacuum chamber connected to a vacuum source, which provides vacuum to the vacuum chamber. Spaced sealing rollers and edge seals define an opening in the vacuum chamber. A sensor measures a vacuum level in the vacuum chamber. A controller is used to produce signals indicative of an activation level or a vacuum level. Means for adjusting the position of the edge seals are used to reposition the edge seals to at least one new position. The controller produces signals indicative of an activation level or a vacuum level at the new positions. A response curve is produced using the signals produced at the first and new positions.