Designing Stamped Metal Enclosures: Shielding, Fit and Finish
Short answer: a stamped metal enclosure is one or more formed sheet-metal parts — a can, lid, frame or channel — that close around a PCB or module to give mechanical protection, EMI shielding and a repeatable fit. Design with a material that forms cleanly (0.2–1.5 mm cold-rolled steel, stainless or aluminum), hold the outline to ±0.1 mm and mating features to ±0.05 mm, and treat the seam as the shielding problem: keep apertures small, make mating surfaces bare metal, and add enough overlap and clamping features that the two halves stay shut. Tooling is a progressive or transfer die, so expect it to dominate first cost, with per-part cost falling once volumes pass a few thousand pieces.
Enclosures look simple until the first prototype comes back with a lid that will not close, a shield that leaks at the seam, or a finish that scratches the moment the boards are handled. Almost every one of those problems was decided at the drawing stage, not on the press. This guide covers the four decisions that actually determine whether a stamped enclosure works in production: material and gauge, the fit and tolerance stack, the shielding design of the seam, and the finish — plus the tooling and cost logic that surrounds a real program.
What a Stamped Enclosure Has to Do
An enclosure is a system, not a part. The same folded sheet of steel may have to protect a board from impact and dust, carry ground from one half to the other, block radiated interference, spread heat away from a hot component, and locate itself precisely so connectors line up through the wall. Each of those jobs pushes the design in a different direction, and the drawing has to satisfy all of them at once without over-specifying any single one.
Stamped construction suits this because a progressive die can pierce, form, coin and cut a complete shell from coil at high speed, with features held to a few hundredths of a millimetre repeatably. That is why enclosures for power supplies, LED drivers, sensors, controllers and small modules are almost always stamped rather than cast or machined. Where an enclosure is large or produced in very small numbers, a folded build from a laser-cut blank is the better first step before committing to a die.
Before you fix a material, fix the function. A shielded enclosure that never opens can be a single drawn shell; one that is serviced in the field needs a removable lid with a predictable clamp load and a seam that re-closes to the same contact resistance after every service visit. Write down which joints are permanent and which open, and the design almost writes itself. Permanent seams can be crimped or spot-welded, while serviceable seams need screws, snap features or a slide fit — and each of those choices changes both the tolerance stack and the shielding approach.
Choosing the Material and Gauge
The material has to form without cracking, resist the environment it lives in, and — if shielding matters — conduct. Thin gauges form tighter radii and lighter parts; thicker gauges hold shape and take more abuse. The common choices behave very differently on the press.
| Material | Typical gauge | Formability | Shielding | Relative cost |
|---|---|---|---|---|
| Cold-rolled steel (SPCC) | 0.5–1.5 mm | Good | Good | 1.0× |
| Stainless 304 | 0.3–1.0 mm | Moderate | Good | 2.5–4.0× |
| Aluminum 5052 | 0.5–1.5 mm | Very good | Good | 1.3–1.8× |
| Aluminum 6061 | 0.8–2.0 mm | Fair | Good | 1.5–2.0× |
| Tinplate | 0.2–0.6 mm | Very good | Good | 1.1× |
| Pre-plated steel | 0.3–0.8 mm | Good | Very good | 1.2× |
Cold-rolled steel is the default for cost-sensitive enclosures that will be plated or painted. Aluminum 5052 is the friendliest to form and gives a light part with decent conductivity, which makes it a favourite for enclosures that also serve as a heat spreader. Stainless resists corrosion and holds a crisp edge, but it work-hardens quickly, so bend radii and press tonnage need care. Pre-plated steels arrive already coated, which removes a finishing step but demands gentle handling so the coating survives forming.
Getting the Fit Right: Tolerances and Stack-Up
A stamped enclosure is judged by how it fits when assembled, and that is where tolerance discipline pays off. The critical dimension is usually not the outline but the relationship between features that must line up — a tab that enters a slot, a screw boss opposite a clearance hole, a connector cut-out that has to sit flush around a mating plug. If those features drift, the enclosure will not close at volume even though every individual part passes its own drawing.
Plan on the following typical capabilities for a well-built progressive die, then loosen only where the function allows.
| Feature | Typical stamped tolerance |
|---|---|
| Overall outline and profile | ±0.1 mm |
| Hole-to-hole position | ±0.05 mm |
| Interlocking tabs and mating features | ±0.05 mm |
| Bend angle | ±1° |
| Flatness on a seating face | 0.1 mm |
| Burr height (functional faces) | ≤0.05 mm |
Tightening any row above raises die cost and slows the press, so specify the loose value wherever it will do. The bend allowance in the flat pattern is the other half of the fit problem; if the blank is not developed with the right allowance, every bend lands in the wrong place by a fraction of the material thickness. Our sheet metal bending allowance guide explains the K-factor math, and it is worth reading before the flat pattern is frozen.
Shielding: Closing the Seam
If the enclosure has to block interference, the walls are almost never the problem — the seam is. Radiated energy enters through the joint between the two halves, through vents, through connector cut-outs and through screw holes. A well-designed enclosure turns that one big leak into many small ones: an overlapping lip, a row of dimples or fingers, and a conductive path across the joint.
Two rules govern the design. First, keep every aperture below roughly one twentieth of the wavelength of the highest frequency you must block — at 1 GHz that is about 15 mm, at 3 GHz about 5 mm — so vents and slots must shrink as frequency rises. Second, make the mating surfaces bare and conductive; anodized or painted faces are insulators and give the interference another way through. Where a hard seam cannot be made tight enough, a stamped gasket of spring fingers bridges the gap. The mechanics of that are covered in our EMI shielding contacts guide and in the companion piece on stamped shields and enclosures, which covers mating surfaces and assembly force in more depth.
Finish and Plating
The finish protects the metal and, for shielding parts, keeps the seams conductive. The choice often comes down to whether the enclosure must conduct across its joints or simply survive outdoors.
| Finish | Thickness | Purpose |
|---|---|---|
| Zinc plating | 5–10 µm | Corrosion protection on steel, cheap |
| Tin plating | 3–10 µm | Solderability and stable contact resistance |
| Nickel plating | 2–5 µm | Wear resistance, solderable |
| Powder coat / paint | 60–100 µm | Colour and weather protection, blocks conductivity |
| Pre-plated steel | as supplied | Conductive, no separate finishing step |
The trap is finishing a shielding enclosure with an insulating coating. If the halves must ground to each other, mask the contact zones or specify a conductive finish on those faces. Conductive finishes on steel are usually zinc or tin; on aluminum, a chromate conversion coating or a masked anodize keeps the shielding intact where it matters.
For enclosures that will be handled and reworked, a conductive finish that tolerates abrasion is worth the extra cost: a scratch through the plating on a seam face creates a high-resistance spot that grows with every opening. If cosmetic appearance matters as well, plate the functional zones and paint the rest, so the shield stays intact where it is needed and the visible surfaces still look right.
Tooling, Lead Time and Cost
An enclosure program is a tooling program. The die is the largest single cost, and it is a one-time investment that the per-part price then amortises. Stripping out unnecessary features, keeping bends in one direction where possible, and designing the flat pattern for good material nesting all reduce die cost and material scrap at the same time. A simple single-part shell may need a progressive die with 6–12 stations; a two-piece interlocking enclosure with gaskets and plated contacts needs more, and the lead time runs longer.
Indicative tooling for a single-cavity progressive enclosure die typically starts in the low thousands of US dollars and climbs with complexity, and the unit price that follows is dominated by material and press time. Above a few thousand pieces a year, stamped enclosures are almost always the cheapest way to make a shielding can or housing. Send the drawing, target volume and shielding requirement to sc@bquq.com and we will return a tooling and unit estimate within 12 working hours.
Common Enclosure Design Mistakes
The same handful of mistakes cause most enclosure failures at production ramp, and almost all of them are visible on the drawing before any metal is cut.
The first is specifying tolerance everywhere instead of only where it matters. A drawing that puts ±0.05 mm on the outline and on a cosmetic face buys nothing but cost; the tight value belongs on the mating features that decide whether the halves close. The second is forgetting that an insulating finish and a conductive shield cannot share the same surface — if the halves must ground to each other, those zones need masking or a conductive coating. The third is designing for a gasket that is compressed past its elastic range, so the fingers take a set after the first assembly and the contact force drops away. The fourth is ignoring the flat pattern: a bend allowance that is wrong by even 0.1 mm per bend compounds across a multi-bend part and throws a connector cut-out out of position by the time the part is formed.
Most of these are far cheaper to fix at the drawing stage than after the die is cut. A short design review before tooling release — covering seams, mating surfaces, bend radii and the tolerance call-outs — prevents weeks of tool rework later.
Frequently Asked Questions
Q: What tolerance can stamped metal enclosures hold?
A: Plan on ±0.1 mm on the outline and ±0.05 mm on hole positions and mating features, with bend angles held to ±1°. Tighter values are possible but raise die cost and slow production, so only call them where the fit actually needs them.
Q: Which material is best for a shielding enclosure?
A: Cold-rolled steel or a copper-alloy-based pre-plated steel gives the best conductivity for the cost. Aluminum 5052 forms well and works if you keep the seam surfaces conductive. Avoid anodizing or painting the mating faces, because an insulating coating defeats the shield.
Q: Do stamped enclosures need a gasket for EMI?
A: Only if the seam cannot be made tight and conductive on its own. An overlapping lip or a row of dimples often closes the joint well enough at lower frequencies, while a stamped finger gasket adds compliance and contact points at higher frequencies or where the halves flex.
Q: What is the minimum order for a stamped enclosure?
A: There is no hard minimum, but tooling dominates below a few thousand pieces, so low-volume runs are better served by a folded laser-cut build first. Once the design is frozen and volume is real, a progressive die makes the stamped version far cheaper per part.
Q: How is burr controlled on enclosure edges?
A: Burr height on functional and handling edges is typically kept to 0.05 mm or less by die clearance control and, where needed, a deburring or tumbling step. Edges that a hand will touch during assembly always merit a burr spec on the drawing.
Related Resources
- EMI shielding contacts guide: materials, plating and grounding for shielded enclosures.
- Stamped enclosures and terminals: stamped cans, frames, lids and contacts from a Dongguan source factory.
- About BQUQ: an ISO9001-certified source factory running stamping, CNC, springs and heat sinks under one roof.
- Contact us: send your drawing and get a quote within 12 working hours.
Authored by the BQUQ Engineering Team. BQUQ is an ISO9001-certified source factory in Dongguan, China, running CNC machining, metal stamping, custom springs, heat sink and collet lines under one roof. Send drawings to sc@bquq.com or WhatsApp +86 13713157787 for a quote within 12 working hours. www.bquq.com
