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.
The process of overmolding partially or fully covers a substrate of metal or plastic with a thin overlain material — often a pliable rubber or thermoplastic elastomer (TPE) layer. The lightweight functionality that overmolding brings to portable devices can improve ergonomics, deaden vibration and improve a product’s grip and feel. The end result is a product that is easily used and can withstand the abuses that naturally come with portable devices, such as drops, abrasions, chemical reactions and fluctuations in temperature and humidity. These considerations are of utmost importance for medical devices and other critical-use applications in various industries from military and automotive to heavy industrial sectors.
Below are four examples of how overmolding is used to help ensure the reliable operation of critical-use portable devices.
1. Surgical Instruments and Devices
Perhaps nowhere do you need devices to function at peak performance more so than in the operating room. Overmolded handles on surgical instruments, for example, provide a surgeon with a comfortable, ergonomic grip for optimum precision.
Portable monitors and other overmolded items in the surgical suite must remain sterile and be able to withstand harsh cleaning agents and autoclaving, along with other environmental factors such as radiation from scans. Not only do surgical devices need to be reliable 100% of the time, they also need to meet FDA medical requirements. Select grades of TPE are chemical resistant which fits well in these applications.
2. AED Units
Automated External Defibrillators (AEDs) are life-saving portable units that must be protected from impact, weather and a host of other factors. An overmolded TPE layer reduces shock, provides a watertight seal, UV resistance and insulates the interior unit from the abuses that can occur in the fast-paced emergency environment where defibrillators are often used. Battery function is critical, so special housing must be engineered and sealed to ensure that moisture or dust particles don’t enter the chamber and cause corrosion. In light of a series of failures that prompted the FDA to tighten its regulatory review process for AEDs in recent years, a qualified injection molder with deep plastics engineering experience and clean room certification must be used to ensure compliance.
3. Electrical Applications
The use of Thermoplastic Elastomer (TPE) as an overmolding material is ideal for situations in which electrical components need to withstand the elements. For example, outdoor electrical outlet covers must be weatherproof and able to withstand years of abuse in various climates. Specially manufactured TPE gasket can expand to create a seal and restrict moisture from coming in contact with electrical connections to prevent shock and fire.
4. Communication and Navigation Devices
GPS units and two-way radios offer many conveniences to consumers. However, when these units are used for emergency personnel or military operations, reliability is absolutely critical. Creating lightweight hand-held devices that are designed for use by soldiers or EMTs in the field is important for those who are weighed down by personal protective gear. Material selection is key for minimizing weight, and protecting the delicate inner electronics against fine dust particles, rain, shock, vibration and other elements is also highly critical. Overmolding can help achieve reliability and durability in these devices, but the proper chemical interaction/compatibility between the substrate and TPE is critical for bonding action and project success.
When such products have critical use applications, the importance of working with an experienced injection molder that understands the various chemical and environmental interactions between the molded resins or metal part and overmolding materials is essential.
To learn more about overmolding benefits, material selection, types of overmolding processes including insert and multi-shot molding and other variables, download our helpful guide, Overmolding Fundamentals. Click the button below for your free copy! If you still have questions contact us directly. Our team of expert engineers are ready to discuss your overmolding and other injection molding needs.