Separate the layout from the shell
The shell — body, door, frame, gland plate — depends on the internal volume, the mounting arrangement and the environment. Those are usually known early. The back plate, the cut-outs and the drilled device pattern depend on the electrical design, which usually firms up late.
Designing the two as separate parts means a late change re-cuts a plate rather than a finished cabinet. It also makes the cabinet reproducible: two units built a year apart will have identical shells and separately drilled plates.
| Part | Depends on electrical layout? | Revision cost |
|---|---|---|
| Body and frame | No — depends on internal volume | High: welded, coated, hardware fitted |
| Door and hinges | Partly — depends on mounted devices and swing | Medium: reinforcement and cut-outs |
| Back / mounting plate | Yes — entirely | Low: a flat plate, laser cut and drilled |
| Gland plate | Yes — depends on cable schedule | Low, and can be supplied loose |
| Cut-outs for HMI and meters | Yes | Medium: front door rework if late |
Cut-outs, clearances and the panel that arrives too small
Cut-outs for HMIs, meters, breakers and terminal blocks are almost always to a device manufacturer drawing. The dimensions are not negotiable; where the cut-out sits is. Position it from a datum the process can hold — a bend or a formed edge — and check the device clearance on all four sides, not just the cut-out.
A second and more subtle trap: the door is a formed panel with its own flatness and its own thickness. A cut-out placed near a formed edge has less material around it than the same cut-out in the middle of the panel, and that shows up as a bezel that does not sit flush.
- Dimension cut-outs from a bend line or formed edge, never from a far corner.
- Leave at least one device clearance behind every cut-out for the fixing clips.
- Keep cut-outs clear of door formed edges and hinge reinforcement.
- Send the populated door layout, not just the cut-out schedule — they are not the same document.
Welding, painting and access
A control cabinet is normally folded and spot welded or folded and riveted, with a welded frame where the cabinet is large or must be stiff. Whichever it is, the sequence matters: anything to be welded on the inside has to be welded before the box closes, and anything to be painted on the inside needs the paint decided before assembly.
The most common late surprise is a cabinet that is painted inside and out but has no masking plan for the door earth strap, the mounting plate fixings and the gland plate face. Coat thickness at a bolted joint is enough to break continuity.
What to send us
An assembly drawing with the shell dimensions, a populated door layout, the cut-out schedule, the back-plate drilling pattern, the gland plate schedule and the finish specification — including which faces are coated and which must stay bare. With that package the cabinet can be built and checked against the drawing rather than against a conversation.