The development of an instrumented tamp-filling capsule machine I: Instrumentation of a Bosch GKF 400S machine and feasibility study

The instrumentation of capsule filling machines operating by the tamp-filling principle has been described only once, using strain gauges. In the present paper the instrumentation of a Bosch GKF 400S tamp-filling machine has been described using a prototype of a pneumatic tamping head equipped with a piezoelectric force transducer. The pneumatic system replaces the conventional springs situated between tamping pins and upper part of the tamping head. Via a feedback switch valve, the air pressure inside the pneumatic chamber can be regulated. This provides a potential mechanism for feedback control of capsule fill weight during continuous capsule filling. It was found that the use of the pneumatic tamping head is limited to the control of fill weight during tamping. Major adjustments of fill weight at the set-up stage of the machine should be made by alteration of the tamping pin and powder bed height settings. The principles of capsule fill weight control by continuous monitoring of tamping forces have been established, but the transfer of the system to full industrial use requires further development of the prototype by the machine manufacturer.