Electronics Housings & Enclosures
Everything on this page comes from parts we have actually molded and shipped: rugged handheld enclosures, sensor housings, connector bodies, junction boxes with molded-in metal inserts, keycaps, power inlet inserts and clear socket housings. They look unrelated. The problems that decide whether they pass a first trial are almost the same four — how the wall changes thickness, how the part closes, how metal and plastic meet, and how the outside face reads. All four are settled in the drawing, not on the press.
What Goes Wrong, and When It Gets Fixed
Almost every reject on an electronics housing traces back to one of six causes. Five of them cost a few hours in CAD to avoid, and a set of steel changes to fix later.
| What you see | Usual cause | Where it gets fixed |
|---|---|---|
| Sink mark on the outside face | Thick section behind a rib, boss or snap hook | Design — thin the feature, not the wall |
| Warpage, or a twisted parting line | Wall thickness uneven across the part, cooling unbalanced | Design, then tool cooling layout |
| Snap fit breaks on first assembly | No root radius, too little draft, undercut too tight for the tool to cut | Design |
| Crack at a screw boss or insert | Boss wall too heavy, no fillet, metal and plastic shrinking against each other | Design, then molding conditions |
| Short shot at the far end | Wall too thin for the flow length, or the gate in the wrong place | Design and gate position |
| Flow lines or a weld line on a visible face | Gate location, or two flow fronts meeting | Tool — partly; texture hides what is left |
The one on that list that is expensive to fix after the tool is cut is the weld line, because it follows the gate. The rest can be corrected in CAD for the cost of a few hours, which is why we ask for the model rather than a photo.
Wall Thickness Comes First
A housing that looks right in CAD can still sink, warp or short-shot. The usual cause is a wall that changes thickness without a transition. We hold a consistent nominal wall and step between thicknesses gradually instead of in one jump, and we add ribs where the part needs stiffness rather than thickening the shell. Ribs sit thinner than the wall they stand on, which keeps the outside face flat and avoids the sink marks that show up over thick sections.
On a part the size of a handheld enclosure, this is usually the difference between a first trial that passes and three rounds of steel changes.
Snap Fits, Bosses and Screw Posts
Most assembly problems in an electronics housing are designed in months before anyone runs a trial. A snap fit needs enough draft and travel to release, and enough clearance under the undercut that the tool can actually cut it. A screw boss needs a wall thick enough to survive driving torque, a pilot hole sized to the screw you will use, and a rib or gusset where it stands far from a corner.
If the housing is ultrasonically welded, the joint geometry — the energy director and the mating surface — is part of the part design, not something added after the tool is cut. We check these features against the assembly method you plan to use, because the same housing usually cannot be both snapped and welded. If you have not settled on a closing method yet, that is the first thing to decide.
Molded-In Metal Inserts
Junction boxes, power inlet inserts and connector bodies usually carry metal that has to end up in a fixed position. Where that metal goes changes the tool. An insert placed by hand at the press needs a seating feature and a clearance that survives operator variation; an insert loaded into the mold needs the tool built around it from the start.
Metal and plastic shrink differently, so the wall around an insert has to carry the stress the insert puts on it as the part cools. Too little material there and the part cracks at the insert within days or weeks of molding, which is a failure that does not show up in inspection. Tell us the insert drawing and the pull-out or torque it has to survive at quoting, not after the steel is cut — retrofitting an insert seat into a finished tool is one of the most expensive changes there is.
Clear and Light-Guided Parts
Transparent housings are judged by a different standard. In a clear or translucent part, the gate position, the weld line and any trapped gas all stay visible in the finished product, so the gate location is an appearance decision as much as a filling one. Polycarbonate absorbs moisture and has to be dried to the right level before it runs; molded wet, it shows splay and bubbles that cannot be polished out.
Between PC and PMMA, the choice is usually decided by whether the part will be dropped. PC survives impact and takes heat; PMMA is clearer and harder to scratch but cracks under a snap fit. For a lens cover that sits behind glass, PMMA is the better part. For a housing that forms the outside of the product, it usually is not.
For light pipes, diffusers and indicator windows, we work to the optical requirement you give us — clear, frosted or diffused, and how even the light has to be — because that decides both the resin and the surface finish of the mold cavity.
Sealing, and What Actually Makes It Work
Where a housing has to keep water or dust out, the seal is a geometry problem before it is a material problem. Three approaches cover most of what we mold:
- A compressed gasket or O-ring in a groove — the groove depth and width have to leave the right amount of squeeze, and the screws have to sit close enough together that the lid does not bow between them.
- Ultrasonic welding along a continuous energy director — strong and permanent, but the part cannot be reopened, and the joint needs a flat uninterrupted path the whole way round.
- Dispensed adhesive, or a formed-in-place gasket — the most forgiving on tolerance, the slowest to assemble.
What we need at quoting is the IP requirement you are actually testing to, where the cable enters, and the wall thickness at the joint. A sealed housing is the one case where a small change after T1 is genuinely expensive, because the seal is the feature the whole tool was cut around.
Material Choice
We keep 13 engineering resin grades on the floor — ABS, PC, PC+ABS, PA6, PA66, PP, POM, PMMA, HDPE, LDPE, TPE, TPR and TPU. The ones that actually come up on electronics work:
| Resin | Why you would pick it | What to watch |
|---|---|---|
| ABS | The default. Good surface finish, paints easily, lowest cost of the three styrenics. | Not for heat or solvent exposure. |
| PC/ABS | More impact resistance and better dimensional stability than ABS alone. | Higher cost; confirm the FR grade early if you need one. |
| PC | Heat resistance, and clarity when the part has to be clear or translucent. | Must be dried to the right moisture level; stress cracking around inserts. |
| PMMA | The clearest option, hardest surface, best light transmission for lenses and light guides. | Brittle — avoid snap fits and thin walls. |
| PA6 / PA66 | Internal brackets and frames that need stiffness and chemical resistance. | Absorbs moisture, so dimensions move after molding. |
| POM | Buttons, sliders and latch parts that need low friction and wear resistance. | Paint and adhesive do not stick well. |
| TPE / TPU | Overmolded grips, gaskets and soft-touch surfaces. | Needs a mechanical interlock in the substrate, not just adhesion. |
If the product needs a flame-retardant grade, give us the standard and the wall thickness it has to meet at the start. Switching to an FR grade later changes the flow and often the wall, which means the tool changes with it. If the part needs EMI shielding, that is normally a conductive coating or a metal can, and either one affects wall design before the steel is cut.
Surface and Appearance
Consumer-facing housings are judged on the outside face. We specify texture on the drawing — a matte or fine-grain finish hides flow marks and handling far better than a polished surface, which shows every defect. Painting, pad printing, screen printing and laser marking run as finishing steps after molding, so the finish decision belongs in the same review as the tool design, not after the first samples arrive.
Assembly and Test
Closing, joining and packing are done here rather than shipped out. Four lines cover ultrasonic welding, adhesive bonding, screw and snap assembly, hardware insertion and final packing. Where the build calls for it, we add a functional test station and check every unit against an agreed checklist before it is packed for export.
The tooling, molding and assembly for these parts sit in the same building. That is what keeps a design change from sitting in an outside tool shop’s queue.
What We Need to Quote
Send the STEP file, a 2D drawing with the tolerances that actually matter, the material or flame-retardant requirement, the surface finish, the annual volume, and — if the housing has to keep water or dust out — the sealing or IP requirement. With those in hand we can return a DFM note and a price instead of a list of questions.
Browse electronics housings we have molded — sensor housings, rugged handheld enclosures, connector bodies, junction boxes and clear parts.
See how a two-part PC/ABS switch controller housing went from drawing to first article
Send your 3D file for a manufacturability review — we will tell you what we would change and why before anything is quoted.