An Analysis of Archimedes Screw Design Parameters and their Influence on Dispensing Quality for Electronics Assembly Applications

Category: Adhesives and Dispensing
Post Date: July 20, 2004
Author(s): Daryl Santos, and Sunil Chhabra, State University of New York at Binghamton, and Douglass Dixon, Wendy Cummings, Sergio Porcari, and Steve Marongelli, Universal Instruments

Description
An Archimedes pump utilizes a threaded screw to turn the material down a cylinder. The material is pumped forward by the relative movement of the screw in the cylinder. The transporting mechanism is similar to a nut held in a wrench with the screw rotating in the nut. Normally, the screw advances in the nut, but when the screw is physically prevented from advancing, as in the case of the Archimedes screw, the nut will slide in the wrench. A motor through a gearbox turns the screw, but a circular ring on the head of the screw prevents it from being pushed out of the cylinder. The movement of the screw within the cylinder causes a pressure rise along the length of the screw. When the material reaches the nozzle, it experiences a change in area, and as a result, it undergoes pressure variation. The nozzle offers resistance to the flow of material, termed as Back-Pressure. The force with which the material dispensed is resultant of the pressure difference between the pump and the nozzle. As a result, it is extremely important to understand the screw parameters, the screw-nozzle combination and the operating conditions that maximize production.

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