Low cost vacuum web coating system

Abstract

A low cost solution for a mini roll to roll web coating system is presented. The design is very simple and involves only three active rolls, two winding/unwinding rolls and a cooling drum. No extra load cells are used to control the web winding mechanism operation. To reach such result it has been necessary to develop an adequate control solution which acts on the two winding roll torques to make the web moving properly. The effect of the control mechanism is to increase electronically the total mechanical inertia of the roll to roll system. In such manner the stick-slip motion of the web, induced by the dry friction affecting the rotation of the rolls, is avoided. The effectiveness of this strategy has been corroborated: a first test showed that the web moves continuously while it is kept tense; in a second experiment a-Si material has been deposited by hot-wire chemical vapor deposition technique. For that material the optical transmission measurements at several points over the deposited area indicate a satisfactory uniformity. The presented tests validate the goodness of the new control method.