Defect-free cast components

The VisionTools automatic visual inspection system with integrated image processing provides a solution to these problems. Mounted directly in the production line, it enables the non-contact recording of the component geometry of a cast component from a safe distance. Using an Ensenso N35 3D camera from IDS, it checks the correct condition and completeness of all sprues, casting beans, runs, channels or feeders.

The evaluation is then carried out with the image analysis software VisionTools V60. Depending on the size and position of the component, several images are required to check all beans, slugs and sprues. For this purpose, the robot places the component in front of the 3D camera. The image acquisition and evaluation takes between 0.3 and 1.2 seconds per component position. The type and test position number are specified by the machine control system.

VisionTools uses an Ensenso N35 3D camera to distinguish the beans in the images from the background. However, different workpieces often have different gloss properties. The camera must be up to these challenges. Since the quality of stereo vision depends directly on the lighting conditions and surface texture of the objects to be inspected, Ensenso 3D cameras are particularly suitable for this application since they make use of the "Projected Texture Stereo Vision" method.

Each model uses two CMOS cameras and a projector that projects auxiliary light patterns onto the object to be captured (in this case the cast components), to increase the accuracy of the surface image. The two CMOS cameras view the respective component from different positions.

Although the image content of both camera images seems to be identical, they show differences in the position of the component under consideration, e.g. the engine components or chassis parts. Since the distance and viewing angle of the cameras as well as the focal length of the optics are known, the Ensenso software can convert these differences into known lengths by triangulation and thus determine the 3D coordination of the object point for each individual image pixel and merge them into a 3D point cloud of the component to be processed. This not only improves the quality of the depth information but also achieves more precise measurement results.

The Flex View projection technology integrated in the N35 model further increases the accuracy of the measurement results. The position of the projector mask in the light beam can be shifted linearly in very small steps. Consequently, the projected texture on the surface of the component  also moves and creates additional structure to help with the reconstruction. Acquiring multiple image pairs with different textures of the same object scene produces a lot more image points, resulting in an increase in resolution. In addition to the resolution, the robustness of the data on difficult surfaces also increases, as the shifted pattern structures apply additional information to shiny, dark or reflective surfaces. The Ensenso N35 thus meets the customer's requirements to make the beans in the photos distinguishable from the background and to be able to reliably test the workpieces which often have different gloss properties.

VisionTools' camera-based image processing solution reduces part inspection errors to a minimum and the downtime of the die casting machines can be almost completely avoided.