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This black panel is the overmolded housing of a resistor and fuse module. Dozens of brass terminals sit in a grid across the face, each one overmolded in place so the plastic both holds them at pitch and isolates them from each other; the edges carry spade tabs and mounting feet, and the face is left with windows where the fuses and resistors seat. It is less a box than a rigid, insulated circuit board made by molding instead of etching.
The resin is a glass-fiber-reinforced polyamide — the PP66+30GF grade, a PA66 base with 30% glass — rated UL94 V0. This page covers insert overmolding, what glass does to a flat part, and the checks that matter.
The terminals could be pressed into a molded housing afterwards, and for low volumes they are. Overmolding them wins at volume for three reasons: the plastic grips each terminal over its full embedded length instead of relying on one knurl; the terminal cannot back out under vibration because it was set in melt, not friction; and the pitch between contacts is held by the tool, not by an assembly fixture that drifts. The terminals are loaded into the mold on pins, the tool closes on them, and the shot forms around them in one cycle.
The process demands discipline. A terminal seated wrong in its pocket gets molded over and scrapes a whole panel, so loading fixtures and vision checks sit in front of the press, and the first shots of every shift are sectioned to confirm the melt has wrapped every terminal completely.
Glass fiber makes the panel stiff and dimensionally stable under heat — exactly what a fuse carrier needs when the engine bay pushes it toward softening. The same fibers make the part want to warp, because they orient along the flow and shrink differently across and along it. On a large flat face this shows as dish or bow. The counters are mold-side: gate placement that splits the flow pattern, wall sections kept uniform, and cooling laid out so neither face of the panel sets before the other. Flatness is measured on a surface plate, not by eye.
The glass also toughens the resin against the one abuse a fuse panel gets: repeated seating and pulling of fuses, which loads the windows around every position.
A fuse panel lives next to current, and the resin carries a UL94 V0 rating — it stops burning within ten seconds and does not drip flaming material. That rating is a property of this specific compound, not of “PA66 with glass” generally, so the resin lot and rating are checked against the material certificate on every receipt. The molding itself does the insulating work: creepage paths between adjacent contacts are drawn into the part as ribs and slots, so the distance current would have to travel across the surface meets the voltage requirement even in a dirty environment.
The spade tabs at the edges are left exposed by design, with the plastic around them forming the isolation walls between circuits.
Kunshan Maifeng Precision Industry Co., Ltd. runs insert overmolding like this panel in house, from terminal loading fixtures to sectioning checks, on machines from 90 to 700 tons with tooling built on site. Send us the terminal drawing and the circuit layout, and we will come back with a mold and process proposal.
Kunshan Maifeng Precision Industry Co., Ltd. (MIF) has an investment of RMB 35 million and an independent factory of more than 5,000 m². The company operates 36 single- and dual-color injection molding machines from 90 to 700 tons, together with more than 50 sets of mold manufacturing and processing equipment. Our service, management and production team includes over 100 people.
Our parent company was established in 2008. We provide product design, mold design and manufacturing, injection molding and product assembly services for custom plastic parts, supporting both domestic and international customers.
1. Product Design
Product structure design and optimization based on customer drawings and samples.
2. Mold Design
Mold design developed around product geometry, material and production requirements.
3. Mold Manufacturing
Machining, polishing, fitting and assembly for custom injection molds.
4. Injection Molding
Single- and dual-color injection molding for project and order requirements.
5. Product Assembly
Supporting assembly services for molded plastic components.
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