Design And Research Of Flexible Fixture For Aircraft Structural Parts

The aircraft structural parts are important components of the aircraft frame and aircraft aerodynamic shape.They have the characteristics of important function and different material.In order to improve the processing quality of aircraft structural parts,advanced processing technology is adopted at home.However,because of the low flexibility and low automation of the machine tool fixture,the number of fixture,the narrow application range of the fixture and the difficult clamping of the workpiece are caused.The processing efficiency and processing quality of aircraft structural parts are seriously affected.During the design of fixture for aircraft structural parts,It takes a lot of time to build parts model and virtual assembly,which affects the design efficiency of the fixture.In order to solve the above problems,this paper has carried out the following aspects of research.Firstly,in the environment of CATIA,a fixture design system for aircraft structural parts is developed with VB.The interface of the fixture design system is developed with VB,and the interface between CATIA and the system interface is realized,and the system program is designed.Parameterized modeling of fixture elements is realized by variable driving parametric modeling method and program driven parametric modeling method,and macro modeling is used to get part of modeling program.Using the API interface provided by CATIA and the VB language,the virtual assembly between the parts of the fixture with the attached constraint is realized.The construction plan of fixture standard part library is explained in detail.An example is given to illustrate the specific method of building fixture standard part library,and the structure of fixture standard part library is introduced.Secondly,taking the milling process of aircraft truss structure as an example,a flexible,fast,adaptive and multi station fixture scheme is proposed,and the fixture design system is used to realize parametric modeling and virtual assembly of components,which improves the efficiency of fixture design.The characteristics of the aircraft truss structure are analyzed,the clamping and positioning scheme of the fixture is determined,and the overall design of the fixture structure is realized.To make up for the lack of pneumatic clamping force transmission faults,a detailed analysis of the principle of toggle force amplifier,and the design of the two orthogonal toggle incremental force mechanism.The pneumatic clamping system of the fixture is designed,and the principle of pneumatic clamping is explained in detail,and the degree of automation of the fixture is improved.The fixture is suitable for different sizes of the truss parts,and the multi position processing of the workpiece is realized,thus the flexibility of the fixture is improved.Finally,the fixture control system is designed by using the SIEMENS S7-200 series PLC.The control requirements of the fixture control system are explained in detail,the control flow chart of the fixture control system is drawn,and the selection of the PLC controller and sensor is completed,and the structure of the fixture control system is determined.According to the control requirements of the control system,the I/O address distribution is determined,and the wiring diagram of the control system is determined according to the I/O address distribution table.According to the general method of programming,the corresponding control program is programmed in STEP7-Micro/WIN software,and the control program is debugged correspondingly to simulate the actual working condition,so as to ensure the feasibility of the control program.