Visual surface inspection

© Fraunhofer IIS

Many components from the automotive and mechanical engineering sectors, from aerospace, or from medical engineering have functional inner surfaces that can only be inspected for faults by means of endoscopy. The use of video technology in conjunction with endoscopy as well as suitable illumination makes ergonomic online visualization possible for testing.

The use of digital technology allows a lot more, however: Automated complete surface inspection of drill holes, cavities of components made of metal, plastic, etc. 100-percent, process-integrated series testing with large batches and short cycle times becomes a possibility.

Fraunhofer EZRT has years of know-how, special camera technology, and special illumination. This means that the solution to complex testing jobs such as these can be carried out reliably and precisely. At the core of the new, fully automated drill testing system are a new type of drill probe and a new type of software. This means that, now, even small blind holes can be inspected.

The endoscopy technology, which has been optimized for use with small drill holes in the millimeter range, can be adapted to different tasks and allows full automation of the visual check with improved, objective, and documented evaluation.

System solution PanCam

The PanCam system solution comprises a drill probe and a connected computer for automatic evaluation of the signals received. The computer has process interfaces to allow for automated logging and sorting of the work components tested. The drill probe works in a camera-based manner according to imaging principles. Its main components are:

  • the imaging sensor (video camera)
  • the miniaturized mapping lens (endoscope) to map the inner surface to the sensor, and
  • a suitable, miniaturized illumination device (LED or cold light)

For automated operation, the drill probe is inserted into the drill hole by means of a computer-controlled, motorized linear axis. While the probe is entering or leaving the drill hole, images of the interior surfaces are recorded as short video sequences. The interior surfaces are comprehensively covered using special 360° lenses, allowing them to be recorded in full without the probe having to be turned; linear movement of the drill is all that is required. This allows very quick data capture in just a few seconds. The use of highly sensitive high-speed cameras increases the test speed yet further. In order to obtain optimum picture quality with very different tasks, the video camera, mapping lens, and illumination must be adapted in each case. As the picture quality depends on the diameter of the drill probe (a larger diameter results in higher picture quality), the largest possible probe diameter is also selected depending on the test object. The preferred use of standard components ensures a high degree of system modularity. The platform of the evaluation computer, for example, comprises an industrial PC with the operating system MS Windows®. The evaluation software analyzes the video sequences generated by the camera in the drill probe lightning-fast. Intelligent algorithms "open up" the scanned interior and map it to a flat surface. Various test criteria can thus be analyzed on a component automatically, simultaneously, and while keeping pace with the manufacturing cycle.

Usage example: Drill hole test

  • Test objects: Drill holes 2–50 mm in diameter
  • Surfaces: Metal surfaces, worked
  • Fault types: Cavities, pores (cast), scratches, edge chipping
  • Fault dimension: > 0.1 mm (depending on drill diameter)
  • Test speed: approx. 3 seconds to cover a 100 mm deep drill hole
  • Imaging: Imaging drill probe with high-speed camera (up to 500 pictures per second) and endoscope with panorama lens
  • Computer: Compatible industrial PC (Windows operating system)

Usage example: Testing irregularly shaped, complex cavities

  • Test objects: Cavities with access > 2 mm in diameter
  • Surfaces: Technical surfaces made of metal, plastic, ceramics, etc.
  • Fault types: Surface defects, other anomalies of various types
  • Fault dimension: > 0.1 mm (depending on drill diameter)
  • Test speed: approx. 3 seconds to cover a 100 mm deep drill hole
  • Imaging: Imaging drill probe with high-speed camera (up to 500 pictures per second) and endoscope adapted to problem
  • Computer: Compatible industrial PC (Windows operating system)

  • Test objects: Drill holes and cavities with access > 2 mm in diameter
  • Fault types: Surface defects of various types
  • Fault dimension: > 50 µm (depending on drill diameter)
  • Test speed: Depending on component; approx. 3 seconds to cover a 100 mm deep drill hole
  • Imaging: Imaging drill probe with high-speed camera (up to 500 pictures per second) and mapping lens adapted to problem, e.g. endoscope
  • Computer: Compatible industrial PC (Windows operating system)

Advantages and customer value

  • Series test by means of high test speed and panorama lens used
  • Parallel testing of different criteria and different areas of the surface in a single test
  • Complete automation of the test process
  • Mapping and logging of test results for quality certification
  • High degree of economy due to high cycle rates and short testing times
  • Additional plus: Process monitoring of tools