Multi-component moulding

Formulations for producing polyurethanes (PUs) by reaction injection moulding (RIM) usually contain mixtures of polyols and diols in order to achieve the desired properties in the moulded part. The present work forms part (1) of a systematic investigation into the effects of polyol blends and glass fibres on the physical properties of unfilled and filled PUs formed by RIM. In the case of unfilled PUs, by using a multi-component polyol mixture, it is possible to investigate the effects on properties of (a) polyol structure, molar mass and functionality, (b) the relative proportions of diol-based hard blocks and triol-based soft blocks and (c) polyol blend compatibility. The... 

Alternatives to multi-component injection moulding are worth considering too. These techniques have not yet been referred to in the present chapter. 

The principle of multi-component moulding has been used for many years. It requires the use of injection machines with several injection units and in most cases the potential for the table to move (turn or slide) with one of the mould halves. The next fragment of the piece remaining in this half of the mould is injected in during the following cycle. 

Deutsches IngenieurBlatt (For engineers in the construction industry) MM MaschinenMarkt Special Plastics (Injection moulding and mould construction, features specialist reports on injection moulding techniques (e.g. injection moulding machinery), special injection moulding processes (e.g. multi-component injection moulding), subsequent processes (e.g. surface treatment), injection mould construction (e.g. CAD/CAM systems, simulation) and other relevant topics)... 

Injection moulding of LSR is possible with an LSR cylinder assembly. However, a multi-component dosage unit is required. A multi-eomponent dosage imit mixes the components A and B and feeds the resulting compoimd to the injection moulding machine. Equal amounts of A and B are mixed and then fed into the injection cylinder. A typical processing system will include ... 

Various terminologies are used in multi-material moulding to describe particular process routes. These have been split into three categories here multi-component, multi-shot and over-mould. Assisted moulding techniques include both gas and water. A brief description of each of these technologies and some of the names commonly used for them in the literature now follows. 

Transfer molding is used for the manufacture of small components and is particularly useful with multi-cavity tools and where small inserts are to be moulded in. Materials used are polyester and epoxide dough moulding compounds, although a new liquid resin injection technique is reported. 

The base moulding shown in Figure 10.4 is a component of a column-mounted multi-function switch used in motor vehicles to operate the direction indicators and horns, and to select main or dip beam. The base is required to bolt to the steering column, to locate the rotor and act as a bearing for the rotation of the rotor, while holding the contacts for the switching of the direction indicators. 

Multi-shot can be used to describe any process whereby distinct multiple material shots are applied to produce a single final component. This includes processes whereby preforms are moulded and then transferred to different cavities on the same machine. It can also be used to describe processes where multiple shots are made into the same tool without the tool opening between shots. 

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