Surface inspection

Damage to metallic components with textured surfaces is often easily detected by the human eye but is much more complicated for automated inspection systems. This is due to the machining methods used, such as turning, grinding or milling, which generate major differences in the surface structure - even when parts are IO. This makes it difficult to identify processing errors (cracks, impact marks, etc.). Depending on the component’s later function, even tiny impact marks may make it unusable. It is therefore essential to fully inspect such components quickly and reliably.

A full surface inspection system has been developed at Fraunhofer IPA to inspect rotationally-symmetrical components, which are commonly encountered. Among other things, the system assesses components for the presence of scratches, cavities, impact marks and blemishes. It can be individually adapted to different component sizes.

Images are recorded by a bright field line scan camera. A robot (or other handling system) places the component on a turntable located immediately in front of the camera. As the component turns, its entire surface is recorded by the camera.

The key element of the inspection system is the subsequent adaptive image analysis process, which is based on man’s ability to detect irregularities even on unknown surfaces. Provided the defects only make up a small proportion of the total surface, these are recognized because they differ significantly from the background. This process is imitated by the analysis software. In the surface analysis step, a model of the surface structure is generated to mask local disruptions.

The inspection system is based on the image-processing package EMSIS, which was also developed at Fraunhofer IPA. It is used to perform a multitude of optical inspection tasks both quickly and easily. Tailored solutions for diverse workpieces and tasks can be realized by selecting an appropriate combination of cameras, lenses and lighting. The user is provided with a tool which he can use to generate and adapt inspection programs without the need for in-depth background knowledge.

Fraunhofer IPA helps companies design and implement tailored sophisticated solutions for surface inspection applications. Depending on customer requirements, these can be implemented based on the software platform EMSIS or as a customized extension of an existing inspection environment.