A new powder flow control system for electrostatic powder coating: a closed-loop-control system equipped with a capacitance sensor

A new powder feed system for powder coating is developed with the aim of th e application of powder coating to high-grade finishing like clear topcoats for automotive bodies. In the new system, a capacitance-type sensor is ins talled, and the system for the closed-loop control based on the detected da ta is constructed. The operation principle of the system is described in th is paper. Next, experiments for performance evaluation of the system were c arried out. Then, the discussion on the experimental results is also carrie d out. Concretely, it is confirmed that the accuracy of powder feed is with in a preset value +/- 3 %. The quantification of conveying air flow rate is also achieved along with stable power feed. In addition, the response spee d within 0.5 s is also realized on the responsiveness of powder feed by the speedup of the valve operation. (C) 2000 Elsevier Science B.V. All rights reserved.