Two steel medical doors can look identical on the loading dock and behave completely differently in year three — one delaminating at the core, the other still sealing. The difference is almost always traceable to what was inspected at the factory. Which quality-control gates and tests actually predict field performance?

Incoming Inspection (IQC)

Quality starts before fabrication:

  • Material certificates — mill certs for steel coil (grade, coating mass for galvanized stock) checked against the purchase spec; stainless verified by grade (304 vs 316) with PMI testing where substitution risk exists.
  • Sheet condition — thickness gauged, surface free of rust, oil, and scratches; protective film intact on cosmetic faces.
  • Hardware and components — hinges, locks, closers, motors, and sensors checked against approved samples and certifications (EN 1935 hinge grades, EN 1154 closers, EN 16005 sensor compliance for automatic systems).
  • Core materials — density checks for rock wool and honeycomb; fire-rated cores verified against the test evidence for the door's rating.

Rejecting nonconforming material at the dock is cheap; discovering it after powder coating means scrapping finished product.

In-Process Dimensional Checks

At each fabrication stage:

  • After cutting: contour and aperture dimensions against the flat pattern (fiber laser accuracy ≈ ±0.05 mm should be the capability benchmark).
  • After bending: angles and flange lengths; angular tolerance around ±0.1 mm on capable press brakes; check for corner tearing and stretched holes near bends.
  • After welding/assembly: leaf overall dimensions, diagonal (squareness), face flatness, hinge and lock prep positions, frame mitre alignment. Door-set gaps (typically 3–4 mm leaf-to-frame) are verified with go/no-go gauges before finishing.

Weld Quality Inspection

  • Visual inspection of 100% of seams against ISO 5817 acceptance levels — specify level B or C for visible/cleanable faces: no cracks, no surface porosity beyond limits, no undercut.
  • Seam continuity and dressing: ground flush, pinhole-free on hygienic surfaces.
  • For structural reinforcement welds, spot-check with dye-penetrant on first articles; systematic records of welder qualification where the customer or certification body requires it.

Coating Inspection

Powder-coating QC follows established test standards:

  • Dry-film thickness with a calibrated gauge (per ISO 2360 methods); typical target 60–80 µm.
  • Adhesion — cross-cut test to ISO 2409 / ASTM D3359 on a sample per batch; classification 0–1 is the usual acceptance for door skins.
  • Cure verification — solvent (MEK) rub test or hardness check; undercured film from a 180–200 °C/10–20 min metal-temperature profile failure is soft and fails disinfection exposure.
  • Corrosion performance — neutral salt spray to ISO 9227 on periodic audit samples; hours-to-failure agreed in the spec (e.g., 500 h for interior, higher for humid climates).
  • Appearance — colour/gloss against master panels under controlled lighting; no orange peel, pinholes, or edge-coverage voids.

Operational and Durability Testing

  • Operational test: every door-set assembled with its hardware; open/close force, latch engagement, closer sweep and latching speeds, seal contact all verified. Automatic doors run through activation, presence-safety, and power-fail manual-force checks (see Chapter 18).
  • Cycle/durability evaluation: representative door-sets on cycle rigs — hinge endurance graded by EN 1935 (grades span 10,000 to 200,000 cycles) and closer endurance per EN 1154 — with periodic teardown inspection for wear, core settlement, and fastener loosening. A common mistake is quoting hardware cycle grades as whole-door-set life without testing the assembly.
  • Airtightness: hermetic doors pressure-decay or smoke-tested; isolation door-sets verified at the specified pressure differential.
  • Fire-rated assemblies: no substitution of tested construction — core, intumescent seals, and hardware must match the fire test evidence exactly.

Traceable Quality Records

Traceability is what converts inspection from opinion into warranty protection:

  • Batch/serial numbering on each leaf and frame, linked to material coil numbers, coating batch, welder, and test results.
  • Inspection records at each gate (IQC, in-process, final) retained per ISO 9001 practice; medical fabricators routinely deliver material traceability documentation and CMM/inspection reports with each shipment.
  • Nonconformance and rework log — a factory with a healthy NCR log is more trustworthy than one claiming zero defects.
  • Final inspection report and test certificates shipped with each order; buyers should demand them in the PO, not request them afterward.

Practical Recommendation

When qualifying a factory, audit the records before the machines: ask for three months of IQC reports, coating cross-cut results, and one full traceability chain for a shipped door. A factory that can produce that chain in an hour controls its process; one that cannot is assembling doors, not manufacturing them.