Adjustable Milling Fixture Design Based On In Situ Flatness Measurement

With the rapid development of advanced manufacturing technology, the demand of overall cutting part is flourish. In the process of metal cutting, cutting force and clamping force loaded on the workpiece vary dynamically, which will cause hardly controlled cutting deformation error.. Therefore, dynamic adjustment oriented fixture for end milling, such as adjustable clamping force and variable support point position, has been proposed to online compensate the workpiece deformation during the process of cutting.Hydraulic milling fixture system is designed based on digital control technology, which can adjust the clamping force and support point position dynamically online. It is constructed of three components, i.e., flatness measurement online system, adjustable clamping device and support point position dynamic adjustable device.Based on comprehensive analysis of flatness detection technology, flatness on-line measurement method in milling process is studied. The high precision online laser measurement system is designed to obtain flatness data processed by the error separation technique. Flatness error evaluation algorithm is designed based on hybrid particle swarm algorithm, which compares with the traditional genetic algorithm based and least squares algorithm based method. The online measurement of flatness error provides input data for dynamic control of milling fixture.Online dynamic control method for clamping force is studied. Electro-hydraulic proportional technology is utilized in the clamping mechanism for the purpose of adjusting the clamping force on-line. Closed loop control system is built. The hydraulic system components and control algorithm of dynamic clamping force are designed, and the corresponding PLC procedure is programmed to monitor the real-time clamping force using the winCC configuration software.Adjustable support point position of dynamic fixture is studied. The single point support device whose support position can be adjustable dynamically based on roller and multiple point supporting device whose position can be adjusted are designed respectively with finite element analysis and theory calculation. The movement principle of the mechanism are given and the motion control algorithm and program of the system are designed to support on-line dynamic adjustment of the milling fixture system.