ORIFICE DESIGN FOR EXTRUDING PASTE-LIKE ADHESIVES AND OTHER THICK LIQUIDS

摘要

In high rate tech manufacturing, paste-like adhesives and other similarly-thick liquids must oftenrnbe extruded at high rates, through syringes with long, narrow orifices, and often havingrnconstricting nozzles as well as other segments. Each segment tends to affect liquid flow rate,rnsomething not always fully accounted for, by designers of syringes and their orifices. Anrnadequate flow rate is required through each of the several orifice segments, since theserncollectively add up to a resultant liquid flow rate, which must generally be at or above a certainrnvalue. Further, this value is normally not prescribed adequately in user procurement documents.rnThis paper will discuss the several orifice segments that have been used, detailing their separaternand eventual collective effects. It will show how they impact the result. The basic starting point,rngiven the liquid being extruded, is the required liquid flow rate. In particular, it will show whichrnof the design parameters are most important. It will include specifics of particular designs andrnproblems, as actually experienced in manufacturing. The problems posed by inadequate designs,rnespecially those resulting from adding segments such as tapered flow regions, or constrictivernnozzles, will be discussed. Solutions will be analyzed using Newtonian flow model, withrnmention of the Power Law flow model.