Progressive Die Stamped 316L Medical Instrument Brackets：

Client: MT,Instruments (ISO 13485 certified; USA)

Industry: Medical Device Manufacturing

Challenge:

The client needed 250;000 units per year of small (65mm × 38mm × 12mm) stamping brackets for a reusable surgical instrument sterilizer rack.

The bracket held critical alignment pins and was exposed to:

 Daily autoclave sterilization (steam at 134°C / 273°F; high humidity).

Hospital grade disinfectants (bleach and quaternary ammonium compounds).

 Physical impact from repeatedly loading heavy surgical trays.

The original part was machined from solid 316L bar stock.

While functional; machining had three major problems:

1. Cost: $4.20 per unit (too expensive for a semiconsumable bracket).

2. Lead time: 8 weeks for 5;000 units (machining was too slow).

3. Material waste: 65% of the 316L bar was turned into chips and scrap.

MT requested: stamping brackets alternative at ≤$1.80 per unit; with zero porosity; corrosion resistance equal to machined 316L; and a smooth; cleanable surface (no crevices for bacterial growth).

The Flow Wing Metal Execution:

Step 1: Design for Stamping (DFS) Engineering

Flow Wing Metal’s engineering team reviewed the 3D model and redesigned the stamping brackets:

 Material change removed: Replaced machined bar with 1.2mm thick 316L stainless steel coil (fullhard temper for springback control; then annealed poststamp).

 Geometry optimization: Added 0.5mm fillets to all internal corners (previously sharp 90°) to prevent stress cracking during forming.

 Hole tolerances: Specified punched holes at +0.05mm / 0.00mm for precision pin alignment (achievable with fineblanking techniques).

Step 2: Tooling Fabrication

 Die type: Progressive die with 8 stations.

 Die material: Powdered metallurgy tool steel (CPM 10V) with titanium aluminumnitride (TiAlN) coating for wear resistance against workhardening 316L.

 Press: 200ton Bruderer highspeed stamping press.

 Stations included:

1. Pilot hole piercing

2. Main hole piercing (×4)

3. Lancing: partial cut for clearance feature

4. First 45° bend

5. Second 90° bend

6. Coining: flattening of mounting surface.

7. Blanking: part cut from carrier strip

8. Scrap cutoff

Step 3: Process Development & Testing

 Trial run: 500 parts produced using mild steel (for die validation).

 Stainless trial: 1;000 parts in 316L with specialized chlorinated extremepressure stamping lubricant to prevent galling.

 Adjustments: Increased press speed from 40 to 55 SPM (strokes per minute); added air blast to clear small slugs from piercing stations.

Step 4: Post Stamping Brackets Operations

 Degreasing: Automated threestage spray washer (alkaline wash → rinse → rust inhibitor rinse).

 Deburring: Light vibratory tumbling with ceramic triangles (15 minutes) to remove punchentry burrs (<0.05mm remaining).

 Passivation: Citric acid bath (20% concentration; 25 minutes at 55°C) to restore chromium oxide layer – critical for autoclave resistance.

 Inspection: 100% go/nogo gauge for pin holes; laser micrometer for bend angle tolerance (±0.5°).

Step 5: Quality Validation

 The Result:

 Cost savings: 64% reduction per unit ($4.20 → $1.52) = $670;000 annual savings for the client.

 Production speed: From 8 weeks for 5;000 units (machined) to 2 weeks for 25;000 units (stamped).

 Material utilization: Increased from 35% (machined) to 82% (stamped from coil).

 Quality: Zero field failures reported after 18 months of hospital use. The stamping brackets survive autoclave cycles without pitting; and the passive layer remains intact.

 Client outcome: MT converted 14 additional machined stamping brackets to Flow Wing Metal stamped designs over the following 12 months.

Client testimonial:

> “Flow Wing Metal didn’t just stamping brackets – they re-engineered our entire cost structure. The progressive die tooling paid for itself in the first production run. And the part quality? Better than our original machined version.”,

> – Senior Purchasing Manager; MT Surgical Instruments

Why Choose Flow Wing Metal for Stamping Brackets?

Flow Wing Metal transforms sheet metal into precision components – faster; stronger; and more economical than machining.