Modeling of positive-displacement fluid dispensing processes

Dispensing has been widely used in industry to precisely control the delivery of fluid materials. Among several approaches, positive-displacement dispensing by employing the linear movement of a motor-driven piston is recognized as the most promising because the approach is assumed to be "true" volumetric dispensing. This is true for dispensing a large volume of fluid with continuous piston motion. As the volume of fluid decreases to the micro-liter range, however, this assumption is no longer valid because the fluid properties, in particular the compressibility and flow behavior, can have a significant influence on the volume of fluid dispensed. Taking into account the influence, This work presents the development of a model for the positive-displacement dispensing process. The model is then used to investigate the process performance, with the emphasis on identifying the influence of such factors as the fluid volume in a syringe, the needle temperature, and the fluid properties on the consistency in volume of fluid dispensed.