Micro Deep Drawing of Thin Stainless Steel Sensor Caps (0.1–0.3 mm 316L / 304): What to Check Before a Tender
Why buyers ask
Sourcing consultants running tenders for sensor makers often ask Chinese suppliers to confirm feasibility before they quote. A recent European request is typical: a 316L cap about 0.15 mm thick for a pressure-type sensor, partially nickel plated, with a membrane and adhesive layer, at several million pieces per year, plus a small stamped 304 part at a few tens of thousands per year finished by vibratory (slide) grinding. The questions below are the ones that decide whether such a part is feasible and what it will cost.
What makes thin stainless caps harder than ordinary deep drawing
- Draw ratio and stages: stainless steel work-hardens quickly. A deep, narrow cap needs several draw stages; the number of stages drives the die cost and the number of stations on the press.
- Radii: very small bottom and flange radii relative to the thickness cause thinning and cracks. If the radius is functional (for example where a membrane is seated), mark it as critical; otherwise allow the largest radius the design accepts.
- Flatness and burr: a membrane or seal seat needs a flat, burr-free surface. Say which faces are sealing faces and the flatness and burr limits for them.
- Earing and wall thickness: thin strip forms uneven "ears" at the rim, which is why caps are usually trimmed after drawing. If wall thickness after drawing matters, give a minimum value.
- Material and grain: specify the grade (1.4404 / 316L or 1.4301 / 304), the temper (normally soft annealed for deep drawing) and the surface finish of the strip, and ask for mill certificates.
- Cleanliness: sensor parts are usually degreased, ultrasonically cleaned and packed so they are not touched again. State any particle or residue limit.
Which production route fits which volume
- Prototypes and samples: simple single-stage draw dies or soft tooling; useful to prove the draw before investing in a production die.
- Tens of thousands per year: compound or single-stage dies with manual or semi-automatic feeding are often the economical choice.
- Millions per year: progressive dies or multi-station transfer (eyelet-type) presses fed from coil, with cutting, drawing, trimming and piercing in one line and in-line or batch cleaning.
Give both the annual quantity and the typical release (call-off) size: they decide the die construction, the die steel and whether to plate parts in barrels or on strip.
Partial nickel plating on stainless steel
Nickel does not adhere to stainless steel without activation, so the plating line uses an acid nickel strike before the main nickel layer. To plate only part of the cap, the options are masking, selective (spot or strip) plating, or plating the whole part and removing it where it is not wanted; the right one depends on the geometry and volume. The drawing should show the plated area, the thickness range, and how adhesion and thickness will be checked.
Membranes, adhesives and assembly
If a membrane is bonded into the cap, say whether the membrane and adhesive are supplied by you or should be sourced by the supplier, the curing and peel-strength requirements, and how the assembled part is tested. Assembly in a clean area and packaging that prevents contact with the membrane are usually part of the quotation.
What Hengya can offer
Hengya Stamping deep draws stainless steel, aluminum and copper parts in Wenzhou, with tolerances down to ±0.01 mm on critical dimensions, and quotes plating, cleaning and assembly through our production network across Guangdong, Zhejiang, Jiangsu, Shandong and Fujian. For a tender we return a feasibility statement with the proposed draw stages, the production route for your volume, open questions on the drawing and a quotation. Tooling for production dies normally takes 15–25 days after drawing approval.
What to send for a feasibility check
- 2D drawing (PDF/DWG) with tolerances, and the 3D model (STEP).
- Material grade, thickness and temper, and the strip surface finish.
- Plated areas, plating type and thickness; any finishing such as vibratory grinding or passivation.
- Annual quantity, release size and planned dates for samples and series production.
- Assembly: membrane, adhesive and who supplies them.
- Quality documents required (for example first article report, PPAP, RoHS/REACH) and packaging or cleanliness rules.
- Delivery country, trade term and the tender deadline.
Frequently asked questions
Can 0.15 mm 316L stainless steel be deep drawn into small caps?
Yes. Thin 316L (1.4404) and 304 (1.4301) strip is routinely deep drawn into caps, eyelets and sensor housings from a few millimetres up to about 30 mm in diameter. Feasibility depends on the depth-to-diameter ratio, corner and bottom radii, flatness and burr requirements, so a supplier should confirm it from the drawing, usually with a short draw-stage plan.
Which process is used for millions of micro deep-drawn parts per year?
For annual volumes in the millions, parts are normally drawn from coil on progressive dies or multi-station transfer (eyelet-type) presses, so cutting, several draw stages, trimming and piercing happen in one automatic line. Small volumes of the same part can be made with simpler single-stage dies, at a higher piece price.
How is partial nickel plating done on stainless steel parts?
Stainless steel needs an activation and nickel strike before nickel plating so the layer adheres. Plating only part of the surface is done by masking, by selective (spot or strip) plating, or by plating the whole part and removing it where not wanted. The drawing should mark the plated area, the thickness range and any adhesion or solderability test.
What should I send to get a feasibility statement for a micro deep-drawn part?
Send the 2D drawing with tolerances and the 3D model, material grade and thickness, plated areas and thickness, surface and cleanliness requirements, annual quantity and release size, any assembly such as membrane bonding, the quality documents you need (for example PPAP or first article report) and the tender deadline.
Send your drawing for a feasibility check
Send the drawing with material, thickness, plated areas, annual quantity and deadline. We reply with questions or a quotation and DFM review within 24 hours.