Instead, RedViking combined a six-axis robot from Fanuc with a machine vision system attached to an end effector to inspect these multiple engine components.
“To successfully implement this machine vision solution, we needed to overcome several challenges, including the fact that the parts lack location preciseness, are all about the same color and lighting varies in the plant,” Olson says. The integrator chose the Cognex In-Sight 7000 vision inspection system to examine anywhere from eight to 24 different positions in the allotted 45 seconds during the inspection stage. The IP67 sealed vision system can achieve these cycle speeds with 7.2 GB of program memory while having a 512 MB image processor on board for the critical vision needs with this application. For example, the timestamp resolution can achieve 8 ns and synchronization accuracy is 5 μs. One of the key enablers for the vision system is the PatMax part location tool, which uses a geometric pattern-matching technology to learn an object’s geometry—such as the crossheads and sockets—using a set of boundary curves. Using PatMax, RedViking designed components arranged in acceptable and unacceptable spatial relationships and, by capturing more images with the vision system, defined specific ranges for acceptable parts. The inspection station uses a Rockwell Automation CompactLogix PLC via a PanelView HMI to control the six-axis robot and vision system. In RedViking’s implementation, the system control first identifies the specific engine model and variants to the operator’s HMI at the inspection station. Inspection includes limiting the natural lighting during the process and capturing side view images of the two rocker arms and crossheads for each cylinder. Then the matching tool determines the location of a known reference point on the engine and uses it to inspect the image. From there, the pattern matching verifies the presence of the engine components and determines whether their location and orientation fall within previously defined acceptable limits. After the crosshead and socket inspection, the robotic arm moves to the other side of the engine and examines the pushrod sockets in a similar fashion. At the HMI panel, operators view the newly scanned engine shots against a correct schematic of the engine via an overlay presentation. Green represents a pass and red indicates a defect. The station’s PLC either moves the engine forward if it passes or diverts it to a separate repair station from the assembly line. A local PC on the network saves the images generated during the inspection process and identifies each image with time, date and engine serial numbers. The images are used by engineers to investigate the causes of failures at later stages of the production process or in the field. With production volumes and capacity utilization increasing in plants, automotive OEMs are finding creative ways to meet demand and keep rolling engines off assembly lines.