Overmoulding is a plastic injection moulding process which is very useful for producing multi-material parts with some unique properties.

What is Overmoulding?

Overmoulding is the process of taking a part and then using plastic injection moulding to add additional layers over the current part. With overmoulding, you essentially take two different plastics and combine them into one part. Traditionally, overmoulding starts with injection moulding a hard plastic resin that has a higher melting point. Then, once that part is cooled, another plastic resin is injection moulded over the first part. Usually this is to create a grip or accents on the original part.
What are the benefits of Overmoulding?

Saves money and time
One of the biggest benefits of overmoulding is saving money and time. Since overmoulding can be completed with two runs through our in-house injection moulding process at us, it's not necessary to outsource the overmoulding as a secondary process at another facility. That means there is a cost and time savings by not having to schedule additional outside production.

Doesn't require additional adhesive
This also can save quite a bit of money. By overmoulding, the two pieces are bonded together without adhesive. Otherwise, you would have to setup an additional manufacturing run to attach the two pieces together with adhesive. You would also have to make sure the adhesive is compatible with the two materials, or else the parts will degrade and fall apart.

Different textures and design
With overmoulding, you can combine two different types of plastic resins onto one part. This means you can have a rigid plastic body and then overmould soft silicone grips onto areas that an end user would grab, such as the handle of a tool. You also can overmould different plastic resins to have two very different textures and aesthetic design. For example, we overmoulded a tire showroom display for a customer. The "rubber tread" material was moulded over the harder, blue piece (substrate) that represents "water" in the tread. 

Are there special considerations for overmoulding?

Overmoulding is not without its limitations. One consideration is that the two materials must be compatible, chemically and thermally. Since the first piece is put back into a plastic injection mould, it is important that the first piece can withstand the temperature needed to melt the second material. Also, you will need to make sure the two resins don't react to each other. That can cause the overmould to fall apart.  Finally, overmoulding is not a straightforward injection moulding process like making a part out of a single material. A high level of experience is required to successfully accomplish the overmoulding process. This is a process we do well. In our many years of experience in plastic injection moulding, we've successfully completed numerous overmoulding projects for our customers.

Overmoulding vs Insert Moulding

On the surface, these two techniques look very similar. Overmoulding takes a part and then overlays another layer of plastic injection moulding material over it. One example would be taking a plastic handle and overmoulding a soft silicone grip. Insert moulding takes small parts and embeds them during the plastic injection moulding process. For example, embedding brass wires in a plastic part to create a connector.
How Long Does an Injection Mould Last?

Our injection moulds will typically last well over 100,000 cycles. Moreover, we offer a lifetime warranty for these injection moulds. As long as we continue to make the parts for you, we will maintain and refurbish the tool as needed at our own cost.

Process for overmoulding — Plastic Injection Moulding

Our online quoting team and mould frame sharing technology enables us to simplify and shorten both the quoting and tooling manufacturing process for plastic injection moulding. 

1. Load your 3D CAD file to get your mould and part quote.

2. Add your requirements for overmoulding in the comments, and your project manager will contact you.

3. Upon order confirmation, we start the mould and part order process.

4. Tooling design review by our engineers.

5. Upon design approval, we begin building your injection mould.

6. Customer examines samples for approval.

7. Part production begins.