Clamping System of Injection Molding Machines
In order to keep the mould halves tightly closed when the melt is being injected under high pressure it is necessary to have a clamping system. Most common type of clamping systems are:
1. Hydraulic
2. Mechanical
In the hydraulic systems, oil under pressure is introduced behind a piston connected to the moving platen of the machine. This causes the mould to close and the clamp force can be adjusted so that there is no leakage of molten plastic from the mould.
In the mechanical system, the toggle is the mechanical device used to amplify the force. Toggle mechanisms tend to be preferred for high speed machines and where the clamping force is relatively small. The main advantages of the toggle system are that it is more economical to run the small hydraulic cylinder and since the toggle is self locking it is not necessary to maintain the hydraulic pressure throughout the moulding cycle. The disadvantages of the system is that there is no indication of the clamping force and the additional moving parts increase maintenance costs.
