In the process of engine assembly and new energy vehicle battery pack assembly, the tightening procedure of bolts must be in proper order according to SOP definition. This is critical to both the product quality and the life cycle of the engine or battery pack. Without proper automated monitoring processes, many incidents are frequently taking place. In order to avoid such manual operational errors, a “real-time” visual monitoring system is required to ensure the entire tightening procedure is following the designed order. This reduces operation error to zero and maximizes the assembling quality.