I'm trying to select injection moulding materials, and need some assistance to find the right products.

I have a component that is made up 2 parts; an inner insert and an outer overmould. Originally this was only 1 part, but due to manufacturability of the whole part I have split the processing.

If it's done as a single mould, there are issues with the cycle time, and molten material sitting in the machine too long between cycles causing it to burn. Because of this, I decided to split the part into 2 processes so the inner assembly can be made in volume, perhaps in a separate factory, then very simply located in the mould for the second process (over mould).

The inner polymer insert is injection moulded in a different process long before (days or weeks) the outer moulding process. This contains a bunch of wires and sensors. The sensors are visible on 1 exposed face, and the high wires exit at one side.

When it is ready to use, the inner insert is positioned into the injection mould tool (tooling die). One face of the inner insert makes contact with the tooling die and is shut off, then the overmould is moulded around the inner insert. The inner insert will have one face visible after moulding.

The over mould will have locking mechanisms moulded into it to get it to lock against it matching parts. sounds easy, but the geometry is a little complex to do in 1 process.

The material for the overmould is either ABS (moulding temperature of 180-230°C / 356-446°F) or PBT (moulding temperature of 245-270°C / 473-518°F). The moulding time of the overmould is approximately 20sec.

For the inner insert material, it needs to withstand the above temperatures for the duration without deforming, burning, etc.

Are there any suggestions for the inner insert material that will be compatible with the outer material, and that will withstand the injection moulding process?


  • 1
    $\begingroup$ Insufficient info. Please write about what the inner part must do after the outer mold is complete. As it stands now, there is no reason to avoid doing a single mold. $\endgroup$
    – Abel
    Commented Oct 26, 2022 at 0:55
  • $\begingroup$ Any material that supports the outer materisl pour temperature - check the data sheets. $\endgroup$
    – Solar Mike
    Commented Oct 26, 2022 at 5:33
  • $\begingroup$ @Abel - I have added more detail above. $\endgroup$
    – Nunya
    Commented Oct 27, 2022 at 2:28
  • $\begingroup$ @Solar Mike - Looking at the datasheets will be part of the process, but as there are tens of thousands of different materials, its hard to know what to look at. $\endgroup$
    – Nunya
    Commented Oct 27, 2022 at 2:32
  • $\begingroup$ Generally you pick something that is popular, inexpensive, and sufficient for the task; reducing the per-part costs. Similarly you can do two shots in one mold, further reducing costs and time. --- Your question lacks too many details, you'll need to do a bit more research and provide much more information. --- Perhaps looking at what goes into the design will help: protolabs.com/resources/guides-and-trend-reports/… fastradius.com/resources/plastic-overmolding-materials $\endgroup$
    – Rob
    Commented Oct 30, 2022 at 1:29


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