The Use of Variable Speed Drives to Retrofit Hydraulic Injection Molding Machines

Abstract

Injection Molding is a common method of plastic processing in which thermoplastic materials can be molded into arbitrary complex shapes. Most injection molding machines use complicated hydraulic systems to perform the necessary work of the process. Hydraulic system flow and pressure requirements vary throughout the cycle and in many cases, excess fluid that is not required by the process is throttled back to the reservoir, wasting motor energy and producing additional thermal load on the cooling system. Variable speed drives can be used to allow injection molding machine hydraulic systems to vary the amount of fluid being pumped and thus reduce the amount of fluid that is throttled, reducing the amount of wasted energy. This paper discusses injection molding machine processes and develops a protocol for assessing the efficacy of variable speed drive retrofits for hydraulic injection molding machines.