introduce
The five-axis NC machining technology of complex surfaces is a high-tech in today's manufacturing industry. It is a comprehensive technology involving computer three-dimensional modeling, CAM automatic programming technology, measurement technology, manufacturing technology and cutting simulation technology, so it has high technical difficulty. However, due to the characteristics of high precision, high efficiency and strong machining adaptability, the five-axis linkage machining technology can better adapt to the NC machining of complex surfaces. Nowadays, five-axis machining technology has been widely used in power generation equipment manufacturing, aircraft manufacturing and shipbuilding. For the five-axis NC programming of complex surfaces, because the surfaces are complex, and most of them are inextensible sculpture surfaces, it is easy to produce imperceptible interference phenomena such as over-cutting. Moreover, in the machining of five-axis CNC machine tools, the rotation of CNC milling head or workpiece is prone to interference and collision, resulting in the damage of workpiece, tool and even machine tools. Therefore, in actual processing, even experienced engineers need to repeatedly try and cut the debugging program, resulting in waste of manpower, time, energy and materials and low efficiency. VMs (Virtual Manufacturing System) is a complete mapping of the actual manufacturing system that does not consume energy and resources in the information world. Virtual manufacturing was first proposed by the United States in the 1980s. It is a dynamic simulation of real product manufacturing, and it is a simulation manufacturing software technology that does not consume physical resources on the computer. Virtual manufacturing machine tool system is the mapping of real manufacturing machine tool system in virtual space. It is a virtual system consisting of virtual machine tool → cutter → fixture → workpiece, which has all the functions, characteristics and behaviors of a real machine tool processing system and can complete the same virtual production tasks as the real machine tool processing system. Using virtual manufacturing machine tool to simulate the five-axis NC machining of complex surfaces can truly reflect the interference phenomena such as overcutting and collision in the manufacturing process, and provide data for program modification. The machining program can be debugged repeatedly, and the correct NC machining program can be obtained without consuming materials and energy and occupying machine time. Virtual manufacturing machine tool system can provide key data in machining process, such as optimized cutting parameters and total machining time, through which machining strategy can be evaluated and machining scheme can be improved. The machining program can be further optimized, the idle feed time in the cutting process can be shortened, and the machining feed speed at different positions of complex surfaces can be adjusted.
Virtual manufacturing machine tool system
Aiming at the problems existing in the machining of complex curved surface five-axis linkage system, the following technical research is needed to establish virtual manufacturing machine tool system by using commercial software.
1. Composition of Virtual Manufacturing Machine Tool
2. Machine tool simulation and calibration
3. Program optimization
The virtual manufacturing machine tool should be able to reflect the real machine tool completely and truly, and be consistent or similar to the real machine tool in terms of topological structure, external dimensions and motion functions. The establishment of virtual manufacturing machine tool mainly includes the establishment of machine tool geometry structure, control system and tool library. In order to truly reflect the real machine tool, the virtual machine tool must have the same machine tool topology, and then the geometric dimensions of each motion axis of the machine tool should be consistent with the real machine tool. In particular, the dimensions of CNC milling head and Z-axis ram of a five-axis linkage machine tool with two rotating shafts need to be completely consistent with the real machine tool. In addition, the motion limit and relative relationship of each motion axis of the machine tool should also be consistent with the real machine tool. The purpose of establishing the control system is to make the virtual control system have the same functions as the real system, define the machine tool functions, such as G code and M code, and realize the control function of the virtual machine tool. The establishment of machine tool library is mainly to establish all kinds of tools with the same size and specification used in the actual manufacturing system to simulate the cutting process truly. After adding workpiece blank, cutter and fixture to virtual manufacturing machine tool, setting the relative position relationship between programming coordinate system and machine tool coordinate system, and loading machining program, the simulation of real machine tool machining can be realized. The simulation can truly simulate various phenomena such as overcutting and collision, and give an alarm to indicate the location where this phenomenon occurs. Program optimization first needs to establish a personalized program optimization library for different product materials and tool materials, which needs to be established by doing a lot of cutting experiments. In the process of program optimization, according to different processing materials and tools, examples in the optimization library are selected to optimize the program. After optimization, different cutting feed speeds are automatically set in different machining areas of complex curved surfaces, so that the cutting amount per tooth and metal removal rate remain constant, thus improving machining efficiency.
Application example of virtual manufacturing in complex curved surface machining
The machining of hydraulic turbine blades belongs to the machining of large-scale complex sculpture surfaces, with large blank volume and expensive materials. Using virtual manufacturing technology to simulate the machining process can avoid various manufacturing risks and improve the machining quality and efficiency of parts. The process of machine tool simulation of turbine blades by virtual manufacturing technology is shown in figure 1. We use VERICUT machine tool simulation software to build a virtual manufacturing machine tool on the computer to realize machine tool simulation, program verification and program optimization in the process of machining hydraulic turbine blades. Taking the machine tool simulation of Francis turbine blades as an example, this paper introduces the method of realizing virtual machine tool manufacturing of complex surfaces by using VERICUT software.
Compilation of 1 FKSA 1800 Machine Tool Model System
2. Simulation, verification and program optimization of five-axis machining machine tool for complex surfaces.
FKSA 1800 is a single-arm five-axis linkage milling machine in hydraulic turbine factory. It has three straight axes of X, Y and Z and two rotating axes of B and C. Y axis is attached to Z axis, while C axis is attached to Z axis, and B axis is attached to C axis, which belongs to the first five-axis linkage machine tool. The size of the workbench is1.6m.