The three jobs the enclosure does
Those three jobs conflict at the same features. A fixing that holds the lid down is also a potential path from a live conductor to the tray, and it is also a stress riser in the load path. Designing them together — rather than sealing after the structure is fixed — is what shortens the programme.
- Structural: carries module mass, restraint loads and whatever the crash case imposes; the tray is a load path, not just a container.
- Sealed: keeps water, dust and road debris out of a compartment full of electronics, across thermal cycling and service life.
- Electrical: maintains clearance and creepage between live parts and any earthed metal, including at every fastener and edge.
Materials and forming in practice
| Choice | Reason | Consequence |
|---|---|---|
| Cold-rolled steel tray | Stiffness per unit cost, weldability | Needs full coating or plating; corrosion at cut edges |
| Aluminium tray | Mass saving, thermal mass | More thickness for the same stiffness; different welding and joint design |
| Zinc-coated steel | Corrosion without a full coating | Weld quality drops and the coating burns at the weld |
| Deep-drawn pockets | Module seats formed rather than welded on | Tooling cost; needs volume |
| Folded and welded box | Lower tooling, flexible geometry | Weld distortion control, and a leak path at every seam |
| Stainless fasteners | Avoid galvanic corrosion | Do not mix with coated steel in a wet environment without thought |
Where the DFM conversation usually goes
The most common change we propose is on the lid: a continuous formed groove for the gasket, rather than relying on a flat flange and a self-adhesive seal. The groove costs one forming operation and removes the risk of the gasket being mispositioned during a service reassembly — which is exactly when a pack enclosure gets opened.
The second is on the fastener pattern. Where lid fixings have to be evenly loaded to compress a gasket, the spacing is set by the gasket compression, not by the structural requirement, and the two are often different. Reconciling them at design stage avoids a pattern that seals in the middle and weeps at the corners.
- Design the seal path and the fastener pattern together; gasket compression sets spacing.
- Say which surfaces must remain conductive, and mask them before coating.
- Plan for service: assume the pack will be opened, and design the gasket so it can go back correct.
- Where the tray is also a heat path, the flatness of the module contact face is a functional tolerance, not a cosmetic one.