Design for Manufacture
There is more to designing a part than you might think. At LVS Small Plastic Parts, we understand that how a plastic part looks is only one consideration. As part of the design process. We also consider –
- ‘Mouldability’. It is one thing saying how a part needs to look, we also have to make sure it can be injection moulded. Once formed within the mould tool, components have to be physically ejected or removed by a robot or operator. This means that features such as holes that are set at an angle to the tooling faces must be first created and then ‘cleared’ prior to removal. This is done using devices such as moving hydraulic ‘cores’.
- We also have to ensure that ‘draft angles’ are used, as plastic tends to shrink onto the tooling surfaces (core) as it solidifies. This means that 90-degree corners are usually not achievable, a small taper (or draft) being used to make sure a component can be removed from the tool.
- To ensure high quality components are produced, we have to avoid the pitfalls described in our section on ‘Common Issues & Solutions’. Considerations such as material injection position, wall thicknesses and support structures are therefore critical.
- Precision. Depending on the application of a product, it’s accuracy of manufacture will have a highly varied level of significance. For example, if a part is to be assembled into a product with differing material types and tight tolerances, the material shrinkage rates, levels of allowable distortion and tooling manufacturing methods will have high importance.
- Durability and Stability. Polymer grades and any fillers used can have a major effect on resistance to wear. We can also specify material additives that will help to preserve long term appearance and performance. An example would be UV stabilisers that prevent colour fading and material degradation. Product wall thicknesses and support structures (such as ribs) will also have a major impact on strength, impact resistance etc.
- Cost Considerations. Getting a design right at the start of a products life can save significant amounts of money in the longer term. For example, by minimising the number of components that require assembly.
- Appearance and Ergonomics. This covers cosmetic appearance (less important if the part is hidden from view) and tactile properties such as grip and ‘feel’.
- Future Development. Consideration can be given to possible future modifications. This mainly relates to tooling development. It is much easier to remove material from a metal tool than add it!
- Design for Assembly. We have to consider how a component will interact with others within an assembly. Features such as snap-fit clips can be designed, but secondary operations such ultrasonic welding, pulse staking or bonding can also be considered.
- Design for the Environment. The use of readily recyclable material grades or avoiding the use of metal fasteners (prevent recycling unless first removed) would be typical examples.