Overmoulding, as the name implies, is the process of injection moulding a material over the top of another to create one integrated component. This blog will talk through the overmoulding process, particular industries and applications that can benefit from overmoulding and design tips for integrating overmoulding into plastic injection moulding design.
What is overmoulding?
Overmoulding is a process that is used to create a component with specific functionality, aesthetics or comfort that wouldn’t be achievable using a one-shot moulding process. The second material is added to create handles, grips, buttons etc. Plastic injection moulders typically combine a rigid plastic base with a softer material, such as thermoplastic elastomers (TPE), thermoplastic urethane (TPU) .
The base component is created using the standard plastic injection moulding process. This is typically made from a rigid material such as Acrylonitrile Butadiene Styrene (ABS) or polycarbonate etc. Then, depending on the method used, the second material is either added into the component in that mould, or it is placed into a secondary mould. The softer TPE, TPU, rubber or silicone is then injected into specific places to flow into undercuts and grooves in the base component to form a mechanical or chemical bond, creating one final component. For applications where stronger adhesion is needed, then specific material combinations can be chosen to form a chemical bond (eg. Polycarbonate and TPE, PP and TPE-O or ABS and TPE-S, TPE-U).
Benefits of overmoulding
Some of the benefits of overmoulding include its ability to create:
- Improved anti-slip grips or ergonomic surfaces that give the user a better handling experience.
- Multi-texture or colour surfaces in a single part, improving the component’s aesthetic appearance.
- Soft overmoulded layers that deliver shock, noise and vibration absorption properties, promoting the lifespan of the end product and user comfort.
- More durable products that can be water and dust resistant. They can have improved IP rated seals, joints or enclosures or the additional protective layer can offer resistance to wear, chemicals, impact or other environmental conditions.
Industries and applications that benefit from overmoulding
Thanks to its versatility, there are many industries and applications that can benefit from plastic injection overmoulding. However, there are some where its added protection, enhanced functionality and ergonomic benefits are particularly useful. These include:
Medical and healthcare manufacturers – plastic injection overmoulding allows the creation of hygienic, sealed and ergonomic tools, such as insulin pens, inhalers, diagnostic equipment housing and rubberised grips for surgical instruments. Additionally single use consumables also benefit from overmoulding such as bite blocks.
Automotive manufacturers – durability, comfort and dust and water ingress sealing are all important in automotive applications and plastic injection moulding enables the production of durable seals and gaskets, interior buttons and gear stick knobs, cable sensors and assemblies etc.
Consumer electronics, electronics and home appliance applications – plastic injection overmoulding delivers sleek, user enhanced, and tactile benefits for components such as phone cases, headphones and other wearables, overmoulded and waterproof connectors, sensors, switches and relays, appliance buttons, knobs and handles and vacuum cleaner grips.
Defence and aerospace – with components exposed to extreme conditions reliable sealing, toughness and insulation are a priority. Plastic injection overmoulding delivers all these and more, creating ruggled control panels and sealed electrical connectors.
Industrial and tool equipment applications – thanks to the improved grip, impact strength and vibration resistance of plastic injection overmoulding, it is the ideal process for use with hand tools, power drill handles, and rugged enclosures.
Overmoulding design tips
Equipped with the latest technology including a mix of seven clean room based injection moulding machines ranging from 50 ton to 160 ton, OGM is one of the leading plastic injection moulders in the UK. Spanning two sites and more than 50 injection moulding machines from 35t to 1100t OGM is well versed in delivering a wide range of overmoulding solutions. Including twin shot moulding that completes the overmoulding process in a single cycle of the machine removing the need for a manual operation. Here are some design tips that the team has learned over the company’s many years of operation:
- Material compatibility – the overmould material needs to work well with the substrate to achieve the desired goal (be that chemical or mechanical bonding). There are also thermal compatibility issues if the wrong materials are chosen to use together.
- Good mechanical bonding – Don’t forget the importance of texture and undercuts for good mechanical bonding – this is especially key when the two materials won’t promote good chemical bonding.
- Wall thickness and tolerance maintenance – consistency is important in wall thickness to avoid sinking or warping issues. Also overmoulded parts can shrink during cooling, so this needs to be taken into account in the design stage, especially for components that fit together.
- Venting and flow – remember to include vent locations in the mould’s design to avoid air pockets and design out thin sections that may prevent a complete fill. It is worth adding flow channels too to help guide the material during the plastic injection process.
- Prototype testing – even the best design will need real-world testing to ensure it is fit for purpose.
Plastic injection overmoulding delivers a wide range of benefits and is worth including in your design tool box. If you would like to find out more about overmoulding in the plastic industry, what type of plastic injection moulding process would be best to suit your needs or anything else regarding sourcing plastic moulding services you can find out more about our services by visiting the following URL – https://ogm.uk.com/injection-moulding-services/ or by contacting us directly – https://ogm.uk.com/contact-us/.