Family moulds are used to create several parts of a prototype and are able to be accommodated in the same mould in order to reduce costs and production times. Obviously, these reasons attract many to consider a family mould when they are contemplating their initial mould design, but this format is not always possible in some circumstances, due to space or flow constraints.

As we have previously discussed, when injection moulding, the flow of the resin has to be able to fill the cavity evenly and then be able to cool at a similar rate so as to reduce the appearance of flow lines in the final part and make the part easy to eject from the mould without warping. Adding more parts into each mould makes this task more difficult, which adds further complication as to whether a family mould for some parts is suitable.

Gates: These are used to channel the flow of resin around the part. If the gate is not large enough, it will not be possible to overcome the above issues with flow and not enough resin will be able to fill the mould at the correct pressure. The size, type and location of the gate is very important in ensuring these factors are not compromised and nowhere is this more important than in a family mould with many parts.

Side Actions: More complex mould use side actions to create more than one part in the mould. These must have sufficient space in the mould to work and, therefore, this reduces the space that is available for other parts to be produced in the same mould. They also increase the production time of the product and it may be more suitable to produce parts using a side action individually.

Resin Suitability: As mentioned earlier, it is important to ensure that the flow of resin through the mould is suitable, or a poor quality part may be produced. Certain resins, such as Liquid Silicone Rubber (LSR), are more suitable for this type of mould, as they produce less friction and can fill the mould further and faster, with less pressure.

There you have it! Family moulds are a good way of ensuring economies of scale and reducing production time to a minimum. Yes, they have their difficulties, but a professional engineer will be able to advise whether they are suitable for your project and resin choice.

The engineers at NICE Rapid are experts in producing family moulds and would be happy to assist you in any way that they can. Please do not hesitate to get in contact with us when contemplating your next moulding project.