The effects of powder compressibility, speed of capsule filling and pre-compression on plug densification

This paper describes the effect of powder compressibility and two process parameters of a dosator nozzle capsule filling machine on powder densification during plug formation. One process parameter was the ratio between the powder bed's depth and the length of the nozzle dosing chamber, hereinafter referred to as F. The other one was the speed of capsule filling. This paper demonstrates that powder densification during the capsule filling process is a function of the powder compressibility and the above process parameters (increasing them leads to higher plug density). The Walker model was used to characterize the compressibility of powders at low compression forces and the obtained compressibility coefficient W proved to be a good predictor of powder densification during the capsule filling process.