Injection Molded Wearable Enclosures

A wearable shell is small and thin, and it carries a battery, a board, sensors, and often a charging contact. Thin walls in a small part fill quickly and freeze quickly, so the flow path from the gate to the far end is checked early. A gate on a hidden face or under a strap keeps its vestige off the surface people look at and touch.

Sealing is usually done in one of three ways. A soft TPE layer overmolded onto the rigid shell seals the seam and adds grip at the same time. A separate gasket is compressed between halves by screws or snaps. Or the halves are closed permanently by ultrasonic welding or adhesive. Charging contacts that pass through the shell are insert molded so plastic seals around each pin.

The failure that surprises teams is cracking in the field. Sunscreen, hand lotion, insect repellent, and some cleaners contain oils and solvents that attack stressed polycarbonate and similar resins. A shell that is fine in the chemical alone, and fine under load alone, cracks when both are present. The cracks start where stress is locked in: press fits, snaps, and screw points.

Two things reduce the risk. Molding with less locked-in stress, through gate placement, even walls, and tool temperature. And choosing a resin grade with better chemical resistance for the surfaces that touch skin. Soaking stressed parts in the real lotions the product will meet is the practical way to check a design before tooling is final.