Closed-mould pressure injection system

Clamping Systems In order to keep the mould halves tightly closed when the melt is being injected under high pressures it is necessary to have a clamping system. This may be either (a) hydraulic or (b) mechanical (toggle) - or some combination of Ae two. 

To achieve a more uniform distribution of resin throughout the reinforcement, more automated systems have been developed [12]. In matched-die moulding pre-mixed resin and hardener are injected under pressure from a pressure pot into the reinforcement placed in a closed matched cavity tool [13]. The resin spreads out radially from the point of injection, permeating through the reinforcement until the cavity is completely filled with resin. 

Hydraulic drives. A special pump or else the injection moulding machine s own hydraulic system is used to power a hydraulic drive. The drive system comprises a pressure regulator (the pressures used are 2-8 MPa, depending on the manufacturer) and hydraulic manifolds. The injection machine control system is normally used to control the drive the injection signal is used to open the nozzle and the end of holding phase signal to close the nozzle. Special time relays may also be used to provide control in a different seqnence. 

The control system is there to ensure repeatability during moulding operation. It monitors both the hydraulic system and the process parameters such as temperature, injection speed, screw retraction speed and injection and back pressure. The ability to control the process has a direct impact on final part quality, part to part consistency and economy. The nature of the control system may vary from a simple relay switch to a complex microprocessor system with closed-loop control. Some of the components of the machine control system will now be introduced. 

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