What Is Insert Molding?
Insert molding is an injection molding process in which a pre-placed component — usually a metal insert such as a threaded bush, pin or terminal — is encapsulated with molten plastic to form a single, integrated part. It combines metal and plastic in one operation, removing secondary assembly and producing stronger, more reliable components.
How insert molding works
- The metal insert is placed into the mold cavity (manually or by automation)
- The mold closes and molten plastic is injected around the insert
- The plastic cools and solidifies, encapsulating the insert
- The finished, assembly-ready part is ejected
Common inserts used in insert molding
- Threaded brass and steel inserts
- Electrical terminals, pins and contacts
- Bushings, sleeves and wear plates
- Embedded wires and wire-harness supports
- Custom metal components
Benefits of insert molding
- Stronger parts with durable metal threads
- Fewer fasteners and assembly operations
- Part consolidation — multiple components in one part
- Improved reliability and reduced loosening
- Lower total assembly cost
Typical applications
- Electrical connectors and terminal housings
- Automotive brackets and mounting parts
- Industrial handles, knobs and housings
- Sensor housings with integrated contacts
Insert molding vs over molding
Insert molding encapsulates a solid (often metal) insert in plastic. Over molding, by contrast, molds one material over another already-molded plastic — commonly a soft grip over a rigid body. See our full insert molding vs over molding comparison.
Materials used in insert molding
Common resins include nylon (PA), PBT, polycarbonate (PC), ABS and polypropylene (PP), often in glass-filled grades for added strength. Rollex advises on material selection for secure encapsulation and long-term performance.
Frequently Asked Questions
What is the difference between insert molding and over molding?
Insert molding encapsulates a pre-placed solid insert (usually metal) in plastic; over molding molds one material over another already-molded plastic, typically for soft-touch grips or seals.
What metals can be insert molded?
Brass and steel threaded inserts, terminals, pins, bushings and custom metal components are commonly insert molded.
Does Rollex Industries offer insert molding?
Yes. Rollex Industries is an ISO 9001:2015 certified insert molding manufacturer in Pune, India, supplying insert molded components in India and for export.
Need insert molded components?
Share your part drawings and our team will respond with DFM feedback and a quotation.
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