MIM Work Sequences
The Injection cycle consists of several stages
The production of an injection-moulded part from the feedstock is comparable with the injection-moulding of plastics. The binder component of the compound is melted in the injection unit and is again kneaded through the screw during dosage. It is then injected under high pressure into the cavity of the mould inserted into the clamping unit. After the feedstock has hardened there, the mould is opened by opening the clamping unit, the moulded part is ejected by the ejector and is picked up by a robotic handling unit.
Due to the fact that material and mould changing can be carried out manually in as short a time as under 20 minutes allows just-in time production in line with requirements. The wide range of automation possibilities means that uncomplicated series production of components made of metal powder is easily possible.
The structure of an injection moulding machine
In general, a normal screw-type injection moulding machine consists of a clamping unit, an injection unit and a controller.
The mould, consisting of two halves, is securely fitted in the clamping unit. The clamping unit itself has a stationary platen, referred to as the fixed mounting platen, and also a moving mounting platen. When the clamping unit and therefore the mould is closed, the material can be injected. If the mould is opened due to the clamping unit being open, the moulded part can be removed.
The structure of the injection unit
The machine’s injection unit principally consists of the screw, which transports the compound and compresses it so that is free of bubbles, the heating system which controls the temperature of the compound, and the nozzle out of which the compressed and heated material is injected under pressure into the mould.
Finally, the controller coordinates all movement and production sequences of the powder injection moulding machine.
The injection moulding machines are equipped with computer controllers and monitors to allow ease of use.
All defined adjustment parameters can be saved on data mediums, thereby guaranteeing that executed production cycles can be reproduced. As early as during the production process, reject and good parts can be identified and automatically separated.
To inject powder materials, it is possible to use moulds with the features normally used for working plastics, such as sliding bars, core pulls, unscrewing units, cavity pressure transducers etc.
However, due to the abrasive properties of the powder / binder melts, attention should be paid to providing protection against wear.