Nowadays, in industrial processes, automatic monitoring is considering as an important factor in reducing cost and time, improving product quality and system performance, and increasing customer satisfaction. Currently, there is automatic monitoring in many industries such as textiles, wood, pharmaceuticals, iron and steel, and even in the agricultural industry. One of the commonly used methods for auto-monitoring is use of machine vision. In this method, the video or photographs of goods or products are captured and analyzed by using various image processing methods. One of the most important industries in the country is steel industry and the largest factory in the country in this literature is the Mobarakeh Steel Complex in Isfahan. The complex has units and sections where hot rolling mill is one of these units. In this unit, the hot steel plate is produced. Before finishing production in a hot rolling unit, there is a device called Crop Shear. This device cut off the beginning and the end of the slab, which has become uneven and undesirable. The important problem in the hot rolling unit is the random operation of the crop shear to cut the slab at the beginning and the end of the slab. If the crop shear does not fully work, the unit will suffer financial losses and may even damage the employees. It is very difficult to monitor human due to environmental conditions. Especially in the cold seasons, when water vapor in the environment prevents the slabs from being seen. Therefore, the unit needs for deploying a system that observes this action independently of the environmental conditions. In this environment, it is possible to detect cut pieces using a suitable camera. Extreme conditions such as high temperatures, humidity and water sprays, water vapor, vibration, oil spill, shells caused by slurry scrubbing, and collisions of objects such as cranes and forklifts with the camera are challenges ahead. In this research, the design, construction and testing of the system are investigated. A system that detects the beginning and the end of the slab by using online image and video processing methods.