OCR on motors
BV inspection in the automotive industry, task description
The task of this project is the position recognition and verification of lasered VIN (Vehicle Identification Number) designations on cast aluminium engine blocks and transmissions with very inhomogeneous substrates.
In this case, in addition to unambiguous traceability, a position recognition of the labelled area via OCR evaluation is to be implemented by the system. For clear traceability, engine blocks as well as transmissions are provided with a VIN number. This is applied by laser during production and must then be verified and read out. For this purpose, an image processing system was seamlessly integrated into the customer’s existing system, which reads the previously lasered code and compares it with the specifications of the control system. If the test is successful, the motor is forwarded; if the test is faulty, the corresponding signals are transmitted to the PLC and the status is visualized to the operator, while the test object is discharged at the same time.
Image processing solution
At Volvo, an image processing system was seamlessly integrated into the existing system, which reads the previously lasered code and compares it with the specifications of the control system. If the check is successful, the motor is forwarded; if the check is faulty, the corresponding signals are transmitted to the PLC and the status is visualized to the operator.02
In addition, the system has position recognition. Both laser and camera are attached to a movable robot arm that moves to a specific marking position depending on the motor type. Since the conveyor system does not have sufficient positioning accuracy, the camera checks the laser pose before the marking process and informs the controller of any differences.
After correction of the position a safe marking is now possible. The system is rounded off by an intuitive user interface where the last camera image, position and OCR reading data as well as setting parameters are visualized.
The decisive factor here is the establishment of stable and high-performance communication between the machine vision system, user program and motion control. This was ensured by a solution of integrated system technology from a single source.
Due to the import conditions of some countries, e.g. USA, UAE or Saudi Arabia, engines and gearboxes must be marked directly on the main component with a unique marking. With the OCR application implemented by ISW, the marked plain text without really knowing which alphanumeric character combination was marked on the main part is captured by a camera and evaluated by the software.
In the next step, the recognized alphanumeric character combination is compared with the data set provided by the higher-level controller. The result of the evaluation is then stored by the image processing system in a log file and sent to the higher-level control system.