Injection moulding computer control

Computer controlled injection-moulding machines store the optimum process parameters for each mould/polymer combination. However, a number of machine settings affect each polymer variable the melt temperature prior to injection is influenced by the screw speed, the back pressure on the screw, and the barrel and nozzle heater temperatures. There is no simple way of measuring the melt temperature at the nozzle any thermocouple projecting into the melt would be sheared off by the high flow stresses. Therefore, there is open-loop control on the melt temperature, with the value fluctuating both during and between cycles. 

Pigmented pellets from a twin-screw extrusion compounding line are diverted to an adjacent injection moulding machine to prepare test plaques. These are transported automatically by robot to a spectral photometer, where colour intensity is measured and, if necessary, to maintain consistent quality, subsequent automatic adjustments are made to the rate of colourant addition at the compounder. The whole system is centrally computer controlled. 

The rheological measurements were made using a controlled-stress Rheometrics dynamic stress rheometer (SR 500) with a data module and computer acquisition system. The measuring head was a parallel-plate system with diameter 2.5 and 4 cm and a gap of 1 mm. The steady-state viscosity curves, the creep curves and the components of the complex modulus and the complex viscosity were determined in the temperature region between 170 and 230 °C in a dry nitrogen atmosphere. Samples were produced in the form of injection-moulded disks. Orchestrator 6.5.5 software was used to analyse the data. The characteristics of materials investigated are summarized in Table 1. 

Hellmeyer, H. O. and Menges, G., Application of process computers for the control and optimization of injection moulding process, Proc. Annual Tech. Conf. Soc. Plastics Engrs. (1976), p. 386. 

PEI is also used in so-called moulded intercoimect devices (MID), because of its unique plating capabilities. PEI allows the combination of electrical fimctions with the advantages of injection moulded three-dimensional mechanical components in electrical control units, computer components, telecom and mobile phones, internal antennae of duplexers or microfilters, and fibre optic connectors. 

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