Insert Moulding

 What is Insert Moulding?

Insert moulding is a process that starts with placing metal, ceramic, or plastic parts into the plastic injection mould. After those parts have been properly placed, the mould is filled with molten plastic in the regular injection moulding process. Once the plastic has cooled, the inserted parts are now firmly bound to, and integrated into, the plastic parts. There are many options for inserts that can be placed into the mould.  Threaded bushings, wires, batteries, and warning labels are a few examples.

Why Should I Use Insert Moulding?

One of the biggest reasons to use insert moulding is the overall cost savings. While it will cost more during the production run for the inserts to be added, there is significant savings by not having the part handled a second time to manually install the inserts. The other benefit is that the inserts are more structurally stable then if they were inserted post-moulding.

Consider a plastic part that requires multiple threaded bushings integrated into it. If these bushings weren't insert moulded during the plastic injection moulding process, the bushings would have to be added by some other method, such as heat staking (thermoplastic staking), in an additional post-moulding process. This secondary process would add time and cost to the moulding project.

One last benefit to consider is the amount of weight you can save with insert moulding. For instance, if you were considering creating your part completely out of metal because it required machined metal screw holes, you could save significant weight by injection moulding your part out of plastic and inserting threaded metal bushings (assuming your design would allow this change in material). This is very important in industries where weight reduction is a priority, like in the automotive and aerospace industries.

Are There Special Considerations for Insert Moulding?

Whether you are using metal, ceramic, or plastic inserts, one of the biggest considerations is that you have enough material to support your inserts. Having too thin of walls will lead to the insert breaking away from the rest of the part. This can happen during production or during the use of the part. You need to make sure there is enough plastic material to house the insert properly.

This consideration is more of an issue when using plastic inserts. You will want to make sure that the inserts you are using in the mould can safely be exposed to the temperature required to melt the plastic injection material without deforming your inserts. If your inserts can't handle the temperature required to melt the plastic material, you will want to see if a different plastic material with a higher melting point to be safely used in your part.

The other consideration for insert moulding is whether or not your inserts can handle the pressure. The amount of pressure generated during the plastic injection moulding process is very intense. You need to make sure that the inserts can withstand this pressure without cracking or deforming.

Insert Moulding vs Overmoulding

On the surface, these two techniques look very similar. Insert moulding generally takes a small part and encapsulates it within the plastic resin, like embedding a threaded bushing. Overmoulding, on the other hand, is the process of plastic injection moulding a layer of plastic over the top of another, different material, piece of plastic. An example of this is the housing for a portable drill. The main body of the housing is the first run (substrate) of injection moulding, and then the softer grips and handles are overmoulded onto the main body.

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 Insert Moulding — 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.