The challenge
The cartridges are produced for demanding automotive applications and must meet strict quality requirements. Delamination—where the metal separates due to internal stresses—manifests as a subtle difference in depth on the surface and is barely distinguishable from surface stains or other contaminants in regular color photos. Manual inspection was labor-intensive, not scalable, and prone to errors.
The challenge was twofold: on the one hand, detecting actual delamination without confusing it with surface contamination, and on the other hand, integrating the new inspection into the existing machine environment without disrupting the production cycle.
The solution
Vision Partners conducted an extensive feasibility study in the Vision Lab in Drunen. Various lighting concepts were tested on a dataset of cartridges with known defects—including deep scratches, pits, light scratches, and dents—interspersed with approved products. This revealed that photometric stereo in combination with darkfield illumination delivers the most reliable detection.
In photometric stereo, four consecutive images are taken while the product is briefly stationary, each with a different LED incidence angle. From the intensity differences per pixel, the algorithm calculates a normal map: an image that represents the local surface orientation per pixel. Depth differences such as scratches, pits, and delamination create characteristic patterns in this normal map that can be reliably segmented—while surface stains are precisely not emphasized.
The proposed machine vision system consists of:
- 5 Mpx industrial global shutter color camera with industrial lens, placed in the existing stainless steel machine guard
- Photometric dome lighting (TPL Vision MR-80-WIR-D) for controlled, direction-dependent lighting from four positions
- Industrial machine vision computer (Intel, Windows LTSC) for image processing and inspection logic
- PLC communication via 24V I/O of Ethernet TCP/IP: the system receives a start pulse and returns a pass/fail signal
- Logging from images and inspection results for traceability (>10,000 inspections stored)
In addition to the new delamination inspection, the system also takes over the existing surface inspection, so that both quality controls are carried out by one integrated solution.
The result
The feasibility test evaluated known cartridge delamination defects. The photometric stereo system detected > 93%. Deep scratches, pits, and rough edges were detected consistently and reliably—precisely the types of defects that pose the greatest quality risk in the production process.
Learn more about surface inspection or photometric stereo? Get in touch.
Read our case study about delamination on rotating objects
