PrintOn a recent LinkedIn live, Craig Tappe and Jeff Dirkx from Accumold’s DfMM team had the opportunity to discuss medical micro molding with the medical engineering and design community, with a focus on overmolding for wearables.
In discussing overmolding options, Dirkx addressed common questions about thermoplastic versus low-pressure molding (LPM) techniques. “One of the main questions we get,” he noted, “is whether we can use thermoplastics to overmold and still get some of the same results or even improve stiffness and permeability compared to low-pressure molding.”
Thermoplastics offer a faster process, which, in turn, reduces piece-part costs—an economic advantage for mass-produced wearables.
Precision in Gate Positioning to Protect Sensitive Components
Protecting delicate components like oscillators, capacitors, and batteries requires precise gate adjustments to control pressure and flow. According to Jeff, “How we adjust the gate or gates to overmold like a PCBA or any type of electronic component is so critical.” Thermoplastic overmolding pressures can reach up to 1,000 PSI—much higher than the typical LPM range of 50 to 200 PSI. Jeff highlighted Accumold’s role in designing features that distribute this pressure effectively, preserving the integrity of sensitive electronics.
Managing the Flow Front
Dirkx illustrated the challenge of managing the flow front in high-pressure molding environments with vivid imagery: “I envision it like a sandstorm coming over a city, just barreling over the top of it.” This metaphor captures the need for careful flow management to avoid damage to components as plastic flows around them. By strategically supporting these features, the molding process maintains integrity even under elevated pressures.
Achieving Single-Shot Overmolding with Thermoplastics
Thermoplastics like polypropylene offer a robust moisture barrier and enable single-shot overmolding, reducing the need for additional layers often required with softer LPM materials. Jeff noted, “If we can do it in one shot, that’s ideal.” This efficiency makes thermoplastics especially suited for rugged applications in wearable electronics, where durability and ease of processing are paramount.