Insert Molding and Over-MoldingMolding

Over-moulding and insert moulding are related injection molding processes where a part made first is then moulded over, or inserted inside a mould, to create a single unified part or product.

Insert Molding and Over-Molding

Insert-molding enables a single co-joined part to contain multiple materials. Previously molded or machined parts, metal or plastic, are inserted into the mold cavity so that the injected resin, either thermoplastic or elastomer, solidifies around them.

Insert-molding enables In-Mould Labelling, a popular design technique which gives designers the facility to embed labels, logos, artwork etc. into a finished product or part. We see this commonly used in the manufacture of phone cases, where pre-printed artwork is inserted into the mold cavity so that, once injected, the artwork is physically sealed inside the back/sides of the case, creating a single unified piece. As opposed to the artwork being printed or stuck on the case after it is molded.

Some molds allow pre-molded parts to have another layer form around them in a process known as over-molding, thereby producing double layer, one-piece items. This process is further refined with double-injection or multi-shot molds where a two-layer part or product is created within one machine either as two shots, one after the other, or co-molded in one cycle. Double-injection molding machines allow for relatively complex two-layer parts or products to be rapidly produced. These final unified pieces can clearly show two distinct materials and colors, or form a more subtly integrated aesthetic.

Understand better what you can do on your next project by reading our Insert & Over Molding Guidelines.

What are the advantages of insert molding and over-molding ?

Superior part or product quality – A unified multilayer part is created
Eliminates further assembly procedures (e.g. adhesives)
Fast production of complex design - shorter lead times on final product
Low manufacturing cost (i.e., vs labor intensive secondary stage processes)
Increased design capabilities
Can add both ergonomic and aesthetic appeal of final product (e.g., phone cases with soft-touch individually colored buttons, or custom rubber grips)
Improved product durability and/or strength

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