press_mechanical — defect_detection (patchcore-stamped-part)

Physics

A camera inspects stamped metal parts exiting the press for defects such as tears, wrinkles, dents, and misfeeds (partial or skewed blank progression). patchcore trains a one-class memory bank of patch embeddings from known-good stamped parts and flags a part whose patch embeddings fall far from that bank, which fits stamping because tears and wrinkles vary in exact shape and location with die wear and blank-lot variation, and labelling every possible defect shape is impractical. A raking (low-angle, directional) light is used rather than a diffuse ring light, specifically because bare or lightly oiled sheet metal is highly specular: a low-angle raking light makes surface deformation (wrinkles, dents) visible as shadow/highlight gradients that a diffuse light would wash out, which is the mechanism patchcore’s patch embeddings actually key on for this part type. The inspection Zone covers the part’s stamped face as it exits on the transfer mechanism. For a press running up to 100 strokes/min (1.7 Hz), the part is momentarily stationary in the inspection station between the press stroke and the transfer advance; a photo-eye or transfer-position signal triggers one high-resolution frame per part, so the only rate requirement is that trigger-to-capture latency stays well under the inter-stroke interval of ~600 ms, which a hardware-triggered camera easily satisfies.

Sensor

• Spec: industrial GigE/PoE area-scan camera with fixed-focal C-mount lens and low-angle raking LED bar light, triggered single-frame capture, global shutter
• Signal: scalar (1), range n/a

Example parts

• Basler ace 2 a2A2600-20gcPRO GigE area-scan camera (2608x1960, global shutter, PoE, HW trigger input)
• Teledyne FLIR Blackfly S BFS-PGE-50S5C-C GigE PoE camera (5.0 MP) with 16mm C-mount lens
• CCS Inc. LDL2-100X30RD low-angle raking LED bar light with controller

Mounting

Mount the camera on a rigid fixture over the transfer mechanism’s inspection station, square-on to the stamped part’s face at a working distance that keeps the full part in focus. Mount the raking light at a shallow angle (typically 10-20 degrees from the part surface) on the side that best reveals wrinkle/dent shadowing for the specific die’s part geometry; verify neither camera nor light intrudes into the ram, transfer fingers, or die’s travel envelope at any point in the stroke.

Wiring

Camera connects via PoE Ethernet to the edge box’s GigE Vision NIC; a photo-eye or transfer-position signal at the inspection station is wired to the edge box’s digital trigger input, firing the camera and raking light together; route trigger wiring away from the press’s motor starter and solenoid wiring to avoid induced noise on the trigger edge.

Validation

run 50 known-good parts and a set of deliberately defective parts (tear, wrinkle, dent, misfeed) through the inspection station and compare flagged/not-flagged against a human QC sort

Expected: known-good parts score below score_threshold on >=98% of frames; each seeded defect class is flagged; re-tune score_threshold against the good-part score distribution after any die change, since die wear shifts the good-part baseline

Safety notes

• lock out/tag out the press (LOTO) before mounting the camera/light fixture near the ram, transfer fingers, or die area
• verify the fixture cannot be struck by the ram, transfer mechanism, or die at any point in the stroke, including at minimum clearance
• electrical safety for PoE camera cabling and raking-light power wiring routed near the press’s motor starter and solenoid wiring

Cost

550–2000 USD, difficulty 4/5, ~90 min install downtime.