Development and Evaluation of a Work System with Product-Specific Lighting Scenarios for Visual Inspection Tasks

Even though machines are increasingly capable of carrying out inspectiontasks, the human eye still is indispensable in the quality control of complexobjects. The disc-shaped products discussed below are engine elements ofmotor vehicles. In service, the elements are subjected to high dynamic loads, sothat small surface deficiencies can cause - due to stress concentration - technicalfailures of the element and (the break down of) the engine. High qualitystandards, and the enormous costs for the supplier in the case of a recall in theautomobile industry, lead to the necessity to check each element prior to shipping.The occurrence of hard to discern surface deficiencies is normally not predictable.Type and position of the deficiency on the disc are critical to decide whether theelement is substandard or not. As well as recognizing and rejecting inferiorgoods, the defects must be categorized and, if necessary, the production areamust be informed in order to fix errors in the manufacturing process.The surface is of significant importance for inspection at the workplaces. Highduty engine parts are often shot peened to improve their durability in dynamicuse. Shot-peening produces a bright appearance of the goods, and the lightis reflected diffusely from the surface. In contrast, products with a thin oxidelayer, resulting from heat treatment, can be classified as elements with a darktype of surface. These parts appear dull black in the light. Lustrous surfacesoccur at least on products which are oily or on partly shiny surfaces.