How Overmolding Enhances Handheld Medical Devices
Popular across many industries, overmolding may initially appear to simply enhance the aesthetics of a device, adding a contrasting color or texture. However, overmolding’s lightweight functionality also elevates ergonomics, deadens vibration, and improves a device’s grip and feel.The result — especially in medical devices — is a product that’s easy to use and withstands impact, abrasions, chemical reactions, and changes in temperature and humidity. Plus, overmolding perfectly meets a critical need within the medical world: the use of handheld, digital devices.
Most of these devices are made from two kinds of durable plastic — inside is a molded plastic frame for strength and rigidity, while outside plastic provides a precisely engineered look, a distinctive shape or contour, a bright color, and a slightly soft, tactile surface that’s tacky enough to prevent slipping and sliding.
Plastic overmolding seamlessly combines multiple materials into one part or product to improve design, performance, and aesthetics.
THE PLASTIC OVERMOLDING PROCESSSimply put, overmolding is partially or fully covering a base substrate of plastic with a thin overlain material — often a thermoplastic elastomer (TPE).
The overmolding process involves two separate molding operations and two separate tools. The base substrate is molded first on its own. To make the final part, the substrate is placed into an overmold tool, where the mold closes over the substrate, material is injected, and the final part is packaged.
The result is an injection molded plastic product with a comfortable, non-slip grip, enhanced durability, impact resistance, and ergonomics without a “plasticky” feel. Overmolding offers a means of producing highly intricate pieces that would be too difficult to make in one injection molding process.
THE EXPERTISE BEHIND PLASTIC OVERMOLDINGAs hinted at above, it’s essential to work with an experienced injection molder that understands the various chemical and environmental interactions between the molded resins and overmolding materials. Special skills and experience are required to execute a multi-material injection molding process at high volume and with acceptably high manufacturing yields, particularly as it relates to material compatibility in overmolding. For example, two plastics may have radically different physical properties, such as melt temperatures or how much they expand when heated. If there’s a mismatch, the inner and outer layers of plastic may not fit together properly, or they will adversely affect each other, mechanically or even chemically. The goal is to get the two molded plastics to bond together in such a way so as to produce a single item that has complete and long-lasting structural integrity. That’s why great care is required throughout an overmolded product’s design and manufacturing, ideally with upfront and ongoing involvement of an experienced custom injection molder.
Neway has an impressive depth and breadth of experience in overmolding, and we’re dedicated to putting seasoned design, manufacturing, and assembly methods to work for our manufacturer partners.