Optical quality testing
Many suppliers currently use industrial image processing systems with cameras for their test systems in order to be able to test their components quickly and reliably in all relevant quality parameters after production and assembly.
This process has its pitfalls – industrial image processing systems that have been used so far are no longer the first choice, especially for different painted surfaces and very diverse components. The reason is that these systems are dependent on a corresponding contrast of the components and an adapted light. In order to achieve convincing results, a large number of aligned cameras are required for different surface coatings and large component variance. An implementation of such systems is very time-consuming and therefore expensive as well as inflexible for future variants of test items. In addition, in practice stray light or changing ambient light often falsify the results. Furthermore, manufacturers of test systems rely on the use of workpiece carriers for the transport of components through the test system – which means that the systems require more space, are less flexible, require changeover times when variants are changed, and ultimately lead to higher costs.
The customer therefore decided to use 3D scanners instead of industrial image processing systems. The first scanner captures the coordinates of the test item on the conveyor belt and passes them on to the robot gripper arm. The system operates completely independently of the position of the component on the conveyor belt. The scanning of the test item for optical inspection for completeness, correct assembly, etc. is done in the “Smart Component Tester” SCoT via a second 3D scanner. The optical inspection is carried out using 3D images.
The “Smart Component Tester” SCoT is a test system for the optical inspection of components for completeness, correct assembly, etc., e.g. for vehicle components of automotive manufacturers and suppliers. It consists of a conveyor belt for inserting and removing test specimens, a test cabin with a robot gripper, two PhoXi 3D Scanners, and a control panel for a graphical overview of the test results.
The short, linear conveyor belt transports the test item without fixed orientation and variant definition to the first station, where a 3D scanner records the respective 3D model. The robot gripper uses this 3D model for an exact calculation of the coordinates of the test item on the conveyor belt. That enables the robot to pick up the respective test specimen quickly and safely – regardless of where and at what angle it lies on the conveyor belt. The robot then picks up the test item and places it in the actual testing position.
The second 3D scanner displays the 3D data for a specially developed virtual camera, which performs the optical test analogously to conventional vision inspections – but is completely unaffected by the current light situation, the contrast between the component and its surroundings, or disturbing reflections.
Other suppliers work with conventional image processing, which is significantly more prone to failure and requires workpiece carriers. In this approach, the type of test item and the position coordinates are determined via a 3D scanner.
With the “Smart Component Tester” SCoT, modules at the end of the assembly line can be checked for correct assembly and position of the components regardless of changing light conditions, contrasts, reflections, and scattered light. SCoT delivers perfectly reproducible results, even with changes in contrast and/or light conditions. In addition, SCoT no longer requires elaborate conveyor technology based on workpiece carriers – and can therefore be used very flexibly. All this means time and space savings, cost reduction, and high flexibility in terms of variant independence: the input, testing, and output of test specimens run in parallel, which is why three workpieces can always be located in the test system at once. Because the system works without workpiece carriers, changeover times are completely eliminated and a mixed operation is possible. Different variants and models can be tested at the same time and new variants can be added quickly and easily in the software.
What convinced Berghof to use Photoneo technology in this test system is the speed of Photoneo 3D scanners. Berghof needed to reach a certain cycle time demanded by their customer and with the Photoneo system, they have succeeded.
The “Smart Component Tester” SCoT from Berghof Testing is one of the “Winners” of the German Innovation Award 2021 in the category “Machines & Engineering”. The “German Innovation Award” honors products and solutions that differ from previous solutions mainly by being user-centered and offering added value. A total of almost 700 innovations were submitted to the critical judgment of the “German Innovation Award” jury, which is made up of independent, interdisciplinary experts from industry, science, institutions, and finance. The entries are evaluated based on the level of innovation, user benefits, and efficiency.