Design Guidelines: Overmoulding & Insert Moulding

Our basic guidelines for overmoulding and insert moulding include important design considerations to help improve part manufacturability, enhance cosmetic appearance, and reduce overall production time.

We offer a number of secondary moulds and tooling services to support your project.

Size

Height may be limited if using a silicone as the overmould material, and deeper parts are limited to a smaller outline. Minimum part volume is 40 mm² Smaller if side-actions are required

With substrate moulds, we can maintain a machining tolerance of ±0.08mm with an included resin tolerance that can be greater but no less than 0.05mm/mm.

With thermoplastic overmoulds, tolerances remain the same as substrate moulds, however, if the overmould is LSR, then tolerances shift to 0.6mm/mm.

Design Feedback
For additional questions, please contact an application engineers at [email protected] or
+44 (0) 1952 683047.

Insert Moulding Capabilities

Instead of a mould that produces a final part using two separate shots like overmoulding, insert moulding generally consists of a preformed part—often metal—that is loaded into a mould, where it is then overmoulded with plastic to create a part with improved functional or mechanical properties.

One way insert moulding is used is with threaded inserts, which reinforce the mechanical properties of plastic parts’ ability to be fastened together, especially over repeated assembly. Bushings and sleeves are another great way to increase part durability for mating components that need more abrasion resistance due to moving parts

Materials

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Overmoulding Material Bonding

Chemical bonding between overmoulded materials is possible, but material compatibility should be considered in order to achieve desired bond strength. Incorporation of an adequate mechanical bond is strongly recommended if bonding is critical to your application. An undercut is a good example of a mechanical bond.

Surface Finishes

Draft

Undercuts

Wall Thickness

Radii

Some part corners will have a radius rather than a sharp edge since we use an automated CNC milling process to make the mould for your parts. This typically does not require a change to your model, but resulting radii are identified before the mould is milled.