What a fabricated enclosure order covers
A steel enclosure is a formed and welded structure with a door or cover, a mounting plate or rail system, provisions for cable entry, and a finish. When a buyer sends one out, the purchase is the sheet metal structure, not the electrical assembly that goes inside it.
That split decides where the standards land. The empty enclosure standard EN IEC 62208:2023 covers an enclosure as supplied by the enclosure manufacturer, before the assembly manufacturer fits switchgear and controlgear rated up to 1 000 V AC or 1 500 V DC, and the 2023 edition was updated against the current standard for low voltage switchgear and controlgear assemblies. The completed cabinet is the buyer's product, verified against the assembly standard, not the fabricator's.
So the enquiry should carry two documents: the enclosure structure as a mechanical item with its own tolerances, weld class and finish, and a short statement of what the buyer's own electrical build will add. Realjet manufactures machinery components to customer drawings, and formed cabinets, covers and housings run through the same route as machine frames and chassis: cutting, forming, welding, machining, finishing and inspection.
Sheet grade and thickness set the process route
Most enclosure structures use continuously hot dip coated steel flat product, the family described by EN 10346 for grades such as DX51D with a stated zinc coating mass. Stainless grades appear where washdown duty or corrosion resistance demands them. Aluminium appears where weight matters, and it brings a different weld procedure and a lower stiffness, so the frame layout usually changes with it.
Thickness drives the rest. Door skins and light covers sit in the 1.5 to 2 mm band and run on press brakes. Frames, plinths, bases and machine housings move into 3 to 6 mm plate, which needs more bending force, larger inside radii and a weld procedure qualified for that thickness.
Two commercial points belong in the enquiry itself. Does the buyer accept a substitute grade or coating mass if the specified material is not in stock, and who approves that substitution? And is the steel bought by the manufacturer or issued by the buyer, because that choice changes the traceability chain in the material certificates. Our note on material certificates and traceability covers what the EN 10204 certificate levels actually prove.
Bending, welding and the flatness a door needs
Press brake capacity sets the largest single formed part. Working lengths from 3,200 to 6,000 mm with capacity up to 500 tonnes cover boxes, frames and complex formed structures, and plate up to 12 m can be cut before bending. A part longer than the brake bed has to be split and joined, which adds a seam the drawing should anticipate instead of discovering at first article.
Forming has limits worth writing into the drawing. Inside radius scales with thickness, springback varies with grade and coating, and holes close to a bend line do not stay round or in position. Hole to bend distances are a drawing dimension, not a note on a shop drawing.
Welding then moves the shape again. Heat input pulls thin panels, so a door frame that is square after forming may not be square after welding. On an enclosure, two surfaces carry function rather than appearance: the gasket face around the door opening, and the mounting face inside. Both should either be machined or ground after welding, or the drawing should accept a straightening step and state its acceptance criterion. Cut and formed parts in the same package have the same problem in a smaller form.
Ingress protection and impact ratings belong on the drawing
An IP rating is not a gasket chosen at the end of the build. The IP code in IEC 60529 classifies protection against contact with live parts and against ingress of solid objects and water, and the IK code in IEC 62262 covers resistance to external mechanical impact. For empty enclosures, IEC 62208 defines the type tests behind those ratings, and the test schedule covers static loads, lifting and transport supports, mechanical operation of doors, axial loads on metal inserts, impact, ingress protection, earth continuity, ultraviolet exposure, corrosion and thermal power dissipation.
Two of those results depend on geometry as much as on material. Ingress protection depends on the flatness of the gasket face and on the door's ability to hold a consistent gap, which is why the flatness tolerance in the drawing matters more than the gasket specification. Impact resistance depends on panel span between stiffeners, so a thinner sheet with closer stiffeners can pass the same test as a thicker sheet with wide spans.
Where the enclosure has to carry a declared rating, the buyer should state it in the enquiry and expect the fabricator to confirm which dimensions and which weld class make it achievable. Neither party should assume a rating from a drawing note.
Thermal load, cable entry and internal mounting
Heat dissipation is a declared characteristic of an empty enclosure under IEC 62208, and it cannot be estimated from a picture. It depends on surface area, material, internal volume and ventilation. If the buyer's electrical build generates more heat than the steel can reject, the answer is geometric: louvres, a filtered fan unit, or a larger cabinet. All three change the sheet metal, so the thermal calculation has to arrive with the drawing, not after production.
Cable entry is the other late change that hurts. Gland plates, cable entry plates, blind knockouts and floor entry positions are formed or cut into the structure. Each one adds a cut, an edge treatment and, in an outdoor cabinet, a sealing detail. A schedule of entries with sizes, positions and whether they are cut or left blank is far more useful to a fabricator than a note saying "suitable cable entries".
DIN rail, mounting plates, earth studs and hinges are small parts with their own tolerances. They are normally bought in and welded or riveted to the structure, so they belong on the drawing with their fixing method and their position tolerance.
Finish, masking and the interface with the electrical build
Enclosure finishes are usually phosphate and powder coat, or a wet paint system where the colour or the substrate demands it. What matters to a fabricator is the specification, not the colour name: the surface preparation grade, the coating system, the dry film thickness and the acceptance test. Our note on surface treatment and coating scope sets out how those items are written into a contract manufacturing enquiry.
Masking is the detail that decides whether the finished cabinet works. Earth stud faces, gasket lands, machined faces and hinge pins should not be coated, and where they are, the coating has to be removed afterwards without damaging the surrounding finish. A masking schedule costs nothing to write and prevents a painted cabinet from arriving with no electrical continuity to its door.
Assembly cleanliness matters where the cabinet will house controls. Cutting, welding and coating all leave debris, and a specified final clean before packing is a reasonable requirement to put in the enquiry. Packaging and export scope then decides how the cabinet survives the trip.
Tolerances, evidence and what to send with the enquiry
For formed and welded structures, general tolerances to ISO 2768 cover most dimensions, and the critical features are listed separately: door opening squareness, gasket face flatness, mounting plate position, hole patterns for hinges and interlocks, and the position of gland plates.
Evidence should be scaled to the risk. A dimensional report on the critical features, the material certificate for the sheet and the purchased parts, the weld procedure reference and the coating thickness record cover most cabinets. Where a declared IP rating is part of the contract, photographic evidence of the gasket face and records of the door gap are more useful than a general statement of conformity.
The most common delay in this kind of order is an incomplete interface. Send these with the enquiry:
- The sheet grade, thickness and coating for each part of the structure
- The frame layout, door arrangement and hinge type
- The gasket face flatness, door gap tolerance and the declared IP and IK ratings
- The mounting plate or rail layout, with positions and tolerances
- The schedule of cable entries, with sizes and cut or blank status
- The masking schedule and the coating specification
- The applicable standard for the mechanical structure, stated on the drawing
Our note on drawing and BOM readiness lists the rest of the package in more detail, and the same rules apply here.
Where the responsibility boundary sits
A fabricator can engineer the structure, choose the forming sequence, qualify the welds and hold the tolerances in the drawing. It cannot decide the electrical design, the heat load, the short circuit rating, the protective measures or the final assembly verification. Those stay with the buyer, and IEC 62208 is explicit that the empty enclosure is one product and the completed assembly is another.
Stating that boundary in the enquiry avoids the most expensive misunderstanding in this product family, which is a buyer expecting a certified cabinet and a fabricator quoting a steel structure.
Next step
Before you request a quotation, put the enclosure side and the electrical side in separate sections of one document, name the ratings you expect the steel to achieve, and mark which dimensions are functional. Include the masking schedule and the coating specification. With that package, a contract manufacturer can quote the forming route, the weld class, the finish and the inspection evidence in one response, and can say plainly which requirements belong to your design authority.