Quality System Backbone
Work under ISO 9001:2015 or IATF 16949 to guarantee full traceability from raw-material heat number to packed part.
Maintain a 3-year data set of cutting parameters, tool-life records and CMM reports for lot genealogy.
Incoming Material Verification
Spark-OES spectrometer check: for 304 ensure Cr ≥ 16 %, Ni ≥ 8 %; for 316L Mo ≥ 2 %; generate mill-certificate match report.
Salt-spray coupon test (ASTM B117, 48 h) on bar stock to confirm passive-film integrity before machining starts.
In-Process Control Points
First-Article-Dimensional (FAD) on batch start: CMM scan of all GD&T call-outs, PPAP level-3 documentation uploaded to customer portal.
Interval sampling: 3 pcs every 50 pcs on critical OD ± 0.01 mm; laser diameter gauge feeds SPC chart with Cpk ≥ 1.67 target.
Tool-wear gate: change insert when spindle power rises 5 % or surface roughness > 0.4 µm; prevents work-hardened "skin" being transferred to part.
Dimensional & Geometric Inspection Arsenal
CMM (3-D, 0.5 µm resolution) for true-position, profile and cylindricity; program automated comparison to STEP file.
Optical comparator & vision systems: non-contact check of micro-drilled holes (Ø 0.3 mm) and thread crests at 50× magnification.
Height gauges, plug/ring/thread gauges for rapid GO/NO-GO on shop floor; cycle time < 30 s.
Surface roughness: contact stylus (Ra, Rz) + white-light interferometer for mirror spec Ra ≤ 0.2 µm.
Surface & Integrity Testing
Passivation verification per ASTM A967: copper-sulfate swab 6 min, no copper plating (red spots) = pass; ensures Cr-oxide film is complete.
Ferrite content on 316L weld overlays (Feritscope) ≤ 3 % to avoid corrosion or cracking in chloride service.
NDT spot checks: ultrasonic (UT) for internal porosity, magnetic-particle (MT) for 416 martensitic parts to find 20 µm surface cracks.
Final & Outbound Inspection
100 % dimensional patrol: calipers, micrometers, bore gauges; any out-of-tolerance part enters MRB (material review board) for rework or scrap.
Functional gages simulate assembly condition; verify thread engagement, press-fit bore, seal diameter, etc..
Cosmetic & packaging audit: gloves-only handling, 200 lux white-light inspection, single-bag VCI, impact-resistant carton.
Corrective-Action Loop
Real-time SPC alarms auto-stop machine; CAPA logged within 30 min, root-cause (5-Why) closed in 24 h.
Customer score-card reviewed monthly; PPM target < 500 for automotive, < 100 for medical.
