A sensor housing has to protect electronics, position a sensing element, survive thermal cycling and resist whatever the environment throws at it — coolant, exhaust gas, salt spray or hydraulic fluid. That combination is why so many of them are deep drawn stainless steel rather than machined from bar.
How are stainless steel sensor housings made?
Stainless steel sensor housings are normally produced by deep drawing 304 or 316L strip into a cup or can shape, in one or several stages depending on depth and wall thickness, then trimming, piercing, forming any flange or thread relief, and finishing with deburring, passivation or plating as required. Critical characteristics are wall thickness uniformity, concentricity between the bore and the outside diameter, seal face flatness and finish, and overall length. Because austenitic stainless work-hardens during forming, deep housings may need intermediate annealing, and the tooling is designed to resist galling. Balford deep draws sensor housings up to 250 mm diameter on presses from 25 t to 350 t, with inspection on a 2.5D optical projector, vision measuring system, bore micrometres and concentricity gauges.
Why deep drawing beats machining for these parts
- Thin, uniform walls with far less material waste than machining from bar
- A closed end formed in one operation instead of a machined pocket
- Repeatable concentricity when the tool is piloted and maintained
- Lower piece cost at automotive volumes
- Surface finish appropriate for sealing after light finishing
The three characteristics that decide whether it works
Wall thickness uniformity governs strength, weight and how much material the drawing process thins; a wall that is nominally 1.0 mm may be thicker at the cup bottom and thinner at the mid-wall. Concentricity decides whether the sensing element sits correctly and whether the housing assembles without forcing. Seal face condition — flatness and roughness — decides whether the joint seals, which is a finishing and handling problem as much as a forming problem.
304 or 316L — and what to tell the supplier
316L is chosen where chloride exposure or aggressive media are expected; 304 covers most general applications at lower cost. Both are austenitic and therefore essentially non-magnetic, which matters if the housing is also part of a magnetic circuit — in that case a soft magnetic grade is required instead. Tell the supplier the medium, the temperature range, the sealing method and whether the part will be welded, because those four answers change the material and the finishing route.
Key point
For a sensor housing, the drawing defines the shape but the assembly defines the tolerances. Send the mating components or the seal specification with the drawing, and the DFM review becomes specific instead of generic.
Frequently asked questions
Can stainless sensor housings be made without annealing?
Shallow parts often can. Deep or multi-stage draws in 304 or 316L usually need intermediate annealing to relieve work hardening and prevent cracking.
Why is concentricity so critical?
Because it positions the sensing element and controls assembly fit. It is produced by tooling and piloting rather than by inspection, which is why it is reviewed at DFM stage.
Is passivation required on stainless sensor housings?
Passivation is commonly specified after forming and machining to restore corrosion resistance by removing free iron from the surface. Balford manages passivation through qualified partners and discloses it.