Theoretical Investigation Into the Performance of the Positive-Displacement Dispensing Process

Abstract

Dispensing has been widely used in industry to control the delivery of fluid materials. Among various dispensing approaches, positive-displacement is recognized as the most promising as its performance is assumed to depend on the mechanical motion of the dispensing apparatus and not on the properties of the fluid dispensed. However, with decreasing volumes dispensed, this assumption is no longer valid as the fluid properties, and in particular the compressibility and flow behavior, can have a significant influence on the performance of the process. This paper presents the development of a model for the positive-displacement dispensing process that accounts for both fluid compressibility and non-Newtonian flow behavior. This model is used to investigate the process performance, with the emphasis on identifying the effects of such factors as the fluid volume in syringe and the needle temperature on the consistency in process performance.