Developments in Pressure Diecasting

Abstract

The range of diecasting machines has increased, in size and locking force, making possible the production of engine cylinder blocks, transmission housings, and other large and complex components, especially in aluminium alloys. Instrumentation has been developed to measure and control the speed and pressure of metal injection, temperature control of the dies, measurement of machine locking force, and oscillographic monitoring of the diecasting process, sometimes with a computer built into the equipment. Large diecasting plants can now receive molten aluminium alloy consignments direct from the secondary metal smelter. In molten-metal handling in the diecasting plant, further developments are being made in furnace design, both for bulk metal melting of scrap, runners, and ingots and in the bale-out furnaces adjacent to the diecasting machines. Several producers of zinc alloy diecastings are now making their own alloy, under carefully controlled conditions. During the past ten years most diecasting companies have been successful in mechanizing at least part of their production. Most zinc alloy diecastings are now produced automatically and considerable development in the much more difficult automation of aluminium diecasting has been. achieved. Methods of automatic ladling, lubrication, and trimming and machining processes linked with automatic diecasting production are discussed. New deburring processes and specialpurpose machines and robots used in handling all stages of the manufacturing processes are described. The positioning and the correct dimensioning of runners and gates has received much attention during the past ten years. Die designers are obtaining valuable help from the mathematical formulae and monographs which have been developed. While the major production of zinc, aluminium, and magnesium alloy diecastings involves standard alloys that were well known ten years ago, some new alloys have been developed. The hypereutectic aluminium–silicon alloys used in the production of some cylinder blocks are described. The development of new die materials, including those based on molybdenum, has helped to make possible the diecasting of high melting point alloys, including stainless steel. Some new diecasting techniques are discussed, including the possibilities of the oxygen-purging or pore-free diecasting process, developed in Japan, but so far little explored in the West. Improved finishing processes for the electroplating of zinc alloy diecastings are described.