Fabricated Gearbox Housing Design

Why fabricated rather than cast

A cast housing is the obvious choice at volume, but the tooling cost only makes sense once you are making hundreds. For a handful of units, a welded plate fabrication reaches the same stiffness and bearing alignment for a fraction of the outlay — provided the design accounts for weld distortion and leaves enough material for post-weld machining.

Designing for the weld shop

The housing was broken into individual plates, each detailed as its own drawing with thickness, hole positions and edge preparation. Bearing bores were left with machining allowance so they could be line-bored after welding, which is the only reliable way to hold shaft alignment once the structure has been through the heat of welding.

Detailing that the shop can work from

Every plate carries its own part number and appears on the fabrication bill of materials, so the shop can nest, cut and track them without interpreting a single assembly drawing. The main circular opening takes an evenly spaced twelve-hole bolt circle that locates a flanged bearing retainer, and the perpendicular square face carries its own central bore with corner fixings for the mating shaft. Critical parameters — the ones that decide whether the gearbox runs true — are marked separately so the inspector knows which dimensions actually matter.

What was delivered

A complete 3D assembly, individual plate drawings, a fabrication BOM, weld callouts, and a leak-test note for the finished housing. The set is designed so a fabricator who has never seen the gearbox can build it correctly from the drawings alone.