How to Source Sheet Metal Enclosures
Sheet metal enclosure RFQ checklist: material and thickness, bends, hardware, seams, NEMA or IP rating, gaskets and finish, with costs and lead times.
1,699 sheet metal fabrication companies in the Noramark directory
An enclosure is a set of sheet metal parts that must fit each other, carry hardware, take a finish and often seal against water and dust. Fabricators build them from laser-cut or punched blanks, bent on a press brake, with self-clinching hardware pressed in, seams welded or fastened, and a powder coat or plating on top. Each of those steps is a place where an incomplete drawing turns into a guess.
A good enclosure RFQ gives a model the shop can unfold, the material and thickness, the bend radius you can accept, every piece of hardware by part number, how the seams are joined, the finish and color, and the environmental rating the box must meet. Mark the dimensions that matter (cutouts, mounting holes, door gaps) and let the rest follow a general tolerance: a press brake holds hole-to-hole on one face far better than it holds across bends.
RFQ checklist
15 things to settle on the drawing or in the request before you ask for sheet metal enclosure quotes. Print it and tick it off against the print, or copy it into the RFQ.
Material and blanks
Material, temper and thickness in mm or inches (for example 5052-H32 at 2.0 mm, 304 2B at 1.5 mm, cold rolled or galvanneal steel), not a gauge number alone
The same gauge number means different thicknesses for steel, galvanized, stainless and aluminum. A thickness removes the ambiguity, and the temper sets the minimum bend radius.
Inside bend radius, or permission to use the shop's standard tooling radius
Every shop has its own punch radii and die openings. Allowing its standard radius lets it build the flat pattern from its own bend deductions, and the parts come out to size.
Cosmetic side and grain or brush direction
The cosmetic side decides which way parts go into the brake and which side keeps its protective film. Brushed finishes look wrong, and some tempers crack, when bent across the wrong direction.
Geometry and tolerances
Critical dimensions (cutouts, mounting hole patterns, door openings) and the datum each is measured from
Features on one flat face are laser or punch accurate, about ±0.1 mm (±0.004"). Dimensions across a bend hold about ±0.25 mm (±0.010"), and each further bend adds to it. Mark the ones that matter.
A general tolerance note for everything else
Without one, the title-block tolerance applies across bends and may be tighter than a press brake can hold.
Minimum flange lengths and hole-to-bend distances checked against the thickness
A flange shorter than about 4 times the thickness will not seat on a standard V-die, and a hole closer to a bend than about 2.5 thicknesses plus the radius distorts. Shops will ask to move them.
Doors and covers: hinge type, swing direction, door gap, latch or lock part numbers
Hinges and latches set hole patterns, clearances and assembly steps, and door gap is one of the tolerances customers notice.
Hardware, seams and sealing
Hardware by manufacturer part number: self-clinching nuts, studs and standoffs, and the side each installs from
Self-clinching hardware is rated for a sheet hardness and minimum thickness. The wrong series pulls out of stainless or thin aluminum, and part numbers let the shop check that.
Seam method: continuous weld ground flush, stitch weld, spot weld, rivet, or fasteners
A continuous TIG seam ground flush on stainless can cost more than cutting and bending the box. Stitch welds or fasteners may be all the design needs.
Environmental rating to meet: NEMA 250 type (for example Type 4 or 4X) or IEC 60529 IP code (for example IP65), and whether it must be tested
A rating drives continuous seams, gasket flanges and door design. Sealing has to be designed into a rated box; it cannot be added after fabrication.
Gasket material and form (formed-in-place foam, adhesive-backed strip, or extruded profile) and where it goes
Formed-in-place gaskets are dispensed by machine after finishing; strip gaskets are applied by hand. Either changes the routing and the price.
Grounding and bonding points: studs, and contact areas to mask from coating
Powder coat insulates. Earth studs and bonding areas must be marked or the finisher coats over them.
Finish, assembly and quantity
Finish: powder coat color and texture (RAL or powder supplier code) and gloss; or plating, chem film, passivation or brushed; plus silkscreen or label artwork
Color, gloss and texture must be named exactly to match other parts. Powder coat adds about 50-100 µm (2-4 mil) per coat, which matters at hardware and tight fits. Screen printing needs artwork and a screen setup.
Assembly level: loose parts, welded box, or fully assembled with doors, gaskets and hardware
On small runs, assembly labor can exceed the fabrication cost.
Quantity per release and annual volume
At a few hundred a year, laser and brake is right. At thousands, a turret punch or stamping tools for the high-volume panels may cut the price.
What to send with the RFQ
- A STEP model with the sheet metal features intact, so the shop can unfold it with its own bend deductions.
- A PDF drawing with critical dimensions, hardware callouts, finish and the rating to meet.
- A hardware list with manufacturer part numbers and quantities.
- Flat patterns (DXF) only as reference; the shop will make its own.
- Artwork for silkscreen or labels as vector files.
- Quantity per release and annual usage.
Lead times
| Prototype or first parts | 1-3 weeks for laser-cut, bent parts with hardware installed; add about a week for powder coat or plating, more for custom colors. |
|---|---|
| Production or repeat orders | 3-6 weeks for repeat orders; longer when stamping tools, custom gaskets or rating tests are involved. |
Typical of U.S. job shops, from order or approved drawing to shipment; confirm with the shop for your part.
What drives the cost
- Welding and grinding, especially continuous seams on stainless that must be blended.
- Number of parts and bends, and bends that need special tooling (offsets, hems, short flanges).
- Hardware count: every insert is a handling step.
- Finish: masking, custom colors with minimum batch charges, and two-color jobs.
- Tight tolerances across bends that need first-piece checks and re-bends.
- Assembly of doors, hinges, gaskets and panel hardware by hand.
- Material: stainless costs more to buy and cut than steel or aluminum and shows every scratch.
Common mistakes
- Gauge numbers with no material thickness.
- Sharp inside corners or zero bend radii in the CAD model.
- Holes and hardware so close to a bend that they distort or cannot be installed after forming.
- Title-block tolerances of ±0.1 mm applied across several bends.
- No masking callout, so ground studs and threads come back powder coated.
- Calling for NEMA 4X or IP66 without designing the seams and door seal for it.
Questions to ask the shop
- What is your standard inside radius for this thickness, and can we use your bend tables?
- Do you powder coat or plate in-house, and what is the minimum charge for a custom color?
- Which hardware do you stock, and may you substitute equivalent self-clinching parts?
- Can you weld and blend cosmetic stainless seams, and can we see a sample?
- Have you built rated enclosures before, and how were they tested?
Typical processes
Typical materials
Charts and calculators
Frequently asked questions
- Should I send a DXF flat pattern or a 3D model?
- Send the 3D model and a drawing. Flat patterns depend on the shop's tooling and bend deductions, so a flat from another shop or from CAD defaults can come out a few tenths of a millimeter off per bend. Let the fabricator make its own flats and approve the first article.
- What is the difference between NEMA 4X and IP66?
- NEMA 250 Type 4X covers indoor or outdoor use against windblown dust, rain and hose-directed water, adds corrosion resistance, and requires the box to be undamaged by external ice. IP66 under IEC 60529 covers dust-tight and powerful water jets, and says nothing about corrosion or ice. They overlap but are not equivalent; specify the one your customer or code requires.
- Aluminum, stainless or steel for an enclosure?
- 5052-H32 aluminum bends well, is light and takes chem film or powder coat. Cold rolled steel is the cheapest and must be coated. 304 stainless suits washdown and outdoor use, and 316 salt and chemicals. Avoid 6061-T6 for tightly bent parts: it cracks unless the radius is generous.
- How tight can a sheet metal enclosure be toleranced?
- Laser-cut features on one flat face hold about ±0.1 mm (±0.004"). Each bend adds roughly ±0.2-0.25 mm (±0.008-0.010") to dimensions measured across it. Put tight tolerances between features on the same face, and datum the critical ones there.
Build the RFQ: attach the print and this checklist
Attach the drawing (PDF) and the model (STEP), and put your answers to the checklist in the description. A Noramark sourcing specialist matches the request with U.S. shops that make sheet metal enclosures and contacts you within 1 business day.
