It’s a world of handheld devices we live in today: smartphones, tablets, GPS assistants and specialized power tools for the shop, lab, kitchen and garden. Medical facilities depend on portable digital devices to care for patients, contractors align studs with pocket-sized levels, troops perform safely in the field with reliable, high-performance equipment and gear, and households are stocked with all kinds of gadgets that make life easier.

Medical grade polymers are quickly becoming the preferred material for a broad range of surgical devices. In certain applications, the robust mechanical properties of medical molding polymers allow complete removal of metal from the surgical device design. In other instances, plastic and metal components can combine to create an enhanced product, with attributes that would not be possible in either an all-metal or an all-plastic device. 

Insert molding is a type of overmolding where a hard substrate component or “insert” is placed inside a mold cavity in an injection molding machine and then “overshot” with an exterior layer—typically a thermoplastic elastomer (TPE). The interaction between the insert and the TPE must be fully understood to create the strongest possible bond. The surface of the insert should also be free of contamination, including dust or even skin oil—even the slightest contamination can weaken the bond between the TPE and the substrate, leading to premature failure.  

The use of overmolding is popular across many manufacturing industries, from consumer products to medical devices, but possibly in no category more noticeable than portable devices. While in some applications, overmolding may seem to merely enhance the aesthetics of a device at first glance — a contrasting color or texture — the use of overmolding on portable devices intended for critical use is highly technical and sometimes highly regulated.

Overmolding is a value-added injection molding method for improving plastic and metal substrate performance and aesthetics. While seemingly simple, the process has a number of underlying complexities which must be carefully considered to ensure your overmolding project meets all goals and expectations.

As the worldwide population ages, healthcare is shifting from clinics and hospitals to in-home care and smaller, non-traditional facilities. As a result, the demand for portable medical devices that monitor diagnostic and therapeutic data and aid in treatment of certain conditions continues to increase. 

Get Control of Tight Tolerances in the Design Phase and Come out Ahead

Here are three things design engineers fully understand:

1. Design has almost everything to do with the success of product or part performance.
2. The importance of design is magnified considerably with tight tolerances.
3. If something goes wrong, check to see if the design is the root cause.

No pressure right? Wrong. There is a lot riding on the designer when developing complex plastic parts and products with tight tolerances, especially when they’re used in critical applications like medicine, auto manufacturing, and military among many others. Here’s why getting control of it in the design phase is a good thing, along with advice that should help take some of the pressure off.

The more companies learn about overmolding, the more they want to use this special injection-molding technology to add value to their product lines. Not only does it improve functionality and performance, it lowers total production costs—that’s pretty rare these days.

So, what is overmolding?