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Control Problem/ Solution: Multiple Cameras and Lights

[#1] Last update 23 Jan 19
Pete Kepf, Certified Vision Professional - Advanced
Multiple Cameras are used to inspect difficult parts


A manufacturer of rubber seals needed to inspect a variety of its products. Increased sales volumes exceeded the capacity of the inspectors, resulting in more defective parts being shipped to customers. This was beginning to adversely affect costs and long-standing customer relationships.

Products were manufactured using a proprietary continual stamping process which produced large volumes. The wear and batch inconsistencies resulted in a repeatable percentage of parts with the primary defects: flash and voids. Because the process was mature and repeatable, management was reluctant to change it. Because the percentage of defects was fairly fixed and detected defective parts were recycled into the process, management explored an automated inspection option to support the increased sales volume.

The challenge was to introduce a 100%-part inspection methodology for the product. After evaluating several inspection concepts, management selected a non-contact visual inspection method. Major technical issues were:

  • A part handling system for inspection needed to be developed
  • All sides of the parts were to be inspected
  • Flash and voids were to be detected simultaneously
  • Rubber by its nature is pliable and non-reflective
  • Required inspection rates were up to 600 parts per minute (10/second)


The picture at the right shows a simplified layout. The actual installation consisted of successive multiple identical stations for a total of eight cameras: four back lit to detect flash and four front lit to detect voids.

A sensor detects the part at the 3 o'clock position. A sensor pulse and an encoder pulse are sent to the controller; the controller stores the relative position of the "current" part. When that part reaches the 6 o'clock location, the controller sends a pulse to the backlit camera and light; followed by a pulse to the front lit camera and light. The ability of the controller to coordinate the part detection, multiple camera/ lighting pulses and a single reject station was indispensable to the operation of this work cell.