Sprueless and Runnerless Moulding

Abstract

During the 40 years that sprueless or runnerless moulding (RM) has existed in the injection moulding industry, moulding techniques have basically remained the same. However, the tooling techniques have changed, although the same economic benefits have been maintained, i.e. no secondary separation, no trimming, more cycles per hour, less energy used in plasticising, less energy used in cooling, no regrind and smaller machine size requirements. With the large selection of engineering plastic materials now available, physical properties of the injection moulded part can dictate that RM be considered, rather than a conventional runner mould, because of optimum gate placement on the moulded part. Since engineering materials are much more costly than commodity-type materials, coupled with the need to mould virgin material, a runnerless mould can pay for itself in a matter of weeks.