Water jet cutting technology has been increasingly widely used due to its many advantages, and it has also shown different development trends. The current product production is increasingly developing towards multiple varieties, small batches, and high precision. Improving the intelligence of equipment is a major development direction. The most typical one is the putting into use of various multi-axis and multi-dimensional water jet processing systems.
Multi-axis and multi-dimensional waterjet processing systems were originally used in the aviation and aerospace industries. Now they have become standard equipment in the aviation manufacturing industry and are gradually replacing laser processing methods. The American McDonnell Douglas Aircraft Company (now part of Boeing) manufactured and installed the first practical three-dimensional abrasive waterjet cutting system in 1988. The system has 5 control axes, and the sixth auxiliary axis is used to control the hat-shaped jet collector. The size range of the processed parts is 6m in the X-axis direction, 3m in the Y-axis direction, and 0.6m in the Z-axis direction. In the Boeing 777 program, Boeing built a large-scale abrasive waterjet cutting system with two Z-axes, one of which is used to control the movement of the cutting head in the Z-axis direction, and the other Z-axis is used as a coordinate day measuring machine. The entire system has a complex detection system composed of multiple sensors, which can detect processed parts and their processing errors. The universal fixture used consists of hundreds of programmed ball-screw arms. Each arm has a vacuum suction cup at the end. Since the cutting force generated during the water jet cutting process is extremely small, these fixtures only need to bear the mass of the workpiece. , can accurately ensure the positioning of the workpiece, and the processing accuracy is extremely high. Using this abrasive waterjet cutting machine to cut multi-layer carbon fiber reinforced composite materials, the cutting speed can reach 2. 5m/min. Replacing the original traditional process of cutting and blanking according to the template can save 20% of materials and increase productivity by 40%. In order to overcome the shortcomings of high prices for large water jet cutting equipment, water jet cutting system manufacturers have developed a class of medium-sized, lower-priced three-dimensional water jet cutting equipment. The medium-sized five-axis machine tool developed in the United States has a processing size range of 3m long and 2m wide. The maximum processing speed is 10m/min. The processing accuracy at this time is ±0.2mm.
Another measure to improve the automation of water jet equipment is to improve its control system. During the water jet machining process, there are not only dynamic control variables such as pressure, abrasive flow, cutting head feed speed, etc., but also quasi-static variables such as mixing tube diameter and nozzle diameter, as well as static variables such as mixing tube length, abrasive type, etc. In order to improve the accuracy of precision machining, it is necessary to control dynamic variables, monitor quasi-static variables, and reasonably select static variables. For this purpose, an expert control system for the jet machining process was developed to simplify the system setup process. In this system, users only need to input static parameters, specify cutting requirements, such as material type, thickness and surface processing quality, etc., and provide the optimization plan for processing, such as minimum material consumption, maximum cutting speed and best surface quality. Wait, the system twisting software automatically provides the control parameters during the cutting process based on the built-in expert knowledge base, and also allows modification. With the in-depth research on self-learning mechanisms in the field of automatic control, it is now possible to achieve the goal of only requiring a human to drive the robot hand along the processing route once, and the robot hand control system can automatically generate processing control data, supplemented by a certain amount of human-machine dialogue to exchange information. , the robot can automatically process, greatly improving the flexibility of the system.
In order to improve the automation of the system, a fully automatic quick-change nozzle was developed. It consists of the nozzle body, nozzle connector, alignment fixture and connector installation and removal system. When replacing the nozzle, the connector installation and removal system removes the nozzle connector and installs a new connector into the nozzle body. The alignment fixture is used to calibrate the connector assembly so that its axis coincides with the axis of the mixing tube. All operations are performed by a robot. Finish. In addition, the pressure rise curve of the computer closed-loop control system can be adapted to different processing materials and improve the processing quality; by placing the force sensor in the flow of abrasive particles to measure changes in the impact momentum of the abrasive particles, the abrasive flow rate and error can be accurately measured. Less than 5%; the life of the nozzle can be monitored by acoustic methods or by measuring the vacuum degree in the mixing chamber below the water nozzle in the batch nozzle; by measuring the acoustic emission signal of the processed material during the processing, certain processing dimensions can be measured online, such as Hole depth, slit depth, etc. All these developments provide guarantee for improving the automation of jet processing.