Application of high speed machining technology of

The main goal of rough machining of hardware molds is to pursue the material removal rate per unit time and prepare the geometric contour of the workpiece for semi finishing. In the cutting process, the metal area of the cutting layer changes, which leads to the change of the load borne by the hardware tools, so that the cutting process is unstable, the wear speed of the hardware tools is uneven, and the quality of the machined surface decreases

many CAM software developed at present can keep the cutting conditions constant through the following measures, so as to obtain good machining quality. Constant cutting load. Constant cutting layer area and material removal rate are obtained through calculation, so that the cutting load and tool wear rate are balanced, so as to improve tool life and machining quality. Avoid suddenly changing the feed direction of the tool. Avoid embedding the tool into the workpiece. For example, when machining the mold cavity, the tool should not be inserted vertically into the workpiece, but the inclined cutting method should be adopted (the commonly used inclined angle is 20 ° ~ 30 °), and the spiral cutting method is best used to reduce the tool load; When machining the mold core, try to cut from the outside of the workpiece first and then cut into the workpiece horizontally. When cutting in and cutting out the workpiece, the inclined (or arc) cutting in and cutting out should be adopted as far as possible to avoid vertical cutting in and cutting out. Using climbing cutting can reduce cutting heat, reduce tool stress and work hardening, and improve machining quality. The main goal of semi finishing die semi finishing is to make the workpiece contour shape flat and the surface finishing allowance uniform, which is particularly important for tool steel dies, because it will affect the change of tool cutting layer area and tool load during finishing, thus affecting the stability of cutting process and the quality of finishing surface. Rough machining is based on volumemodel, while finish machining is based on surfacemodel. The geometric description of parts in the previously developed cad/cam system is discontinuous. Because there is no intermediate information describing the machining model after rough machining and before finishing machining, the distribution of residual machining allowance and the maximum residual machining allowance of rough machined surface are unknown. Therefore, the semi finishing strategy should be optimized to ensure that the workpiece surface has uniform residual machining allowance after semi finishing

the optimization process includes: 3 after rough machining The calculation of the dirty contour of the pointer rotation axis, the calculation of the maximum residual machining allowance, the determination of the maximum allowable machining allowance, the zoning of the profile with the residual machining allowance greater than the maximum allowable machining allowance (such as the areas where the transition radius such as grooves and corners is less than the rough machining tool radius), and the calculation of the tool center path during semi finishing, etc. Most of the existing cad/cam software for mold high-speed machining have the function of residual machining allowance analysis, and can adopt a reasonable semi finishing strategy according to the size and distribution of residual machining allowance. For example, openmind's hyperMILL and HyperForm software provide methods such as pencil milling and restmilling to remove corners with large residual machining allowance after rough machining, so as to ensure uniform machining allowance in subsequent processes. The localmilling of pro/engineer software has similar functions. For example, the value of residual machining allowance in the local milling process is equal to that of rough machining. In this process, only a small diameter milling cutter is used to remove the corners not cut by rough machining, and then semi finish machining is carried out; If the residual machining allowance value of local milling process is taken as the residual machining allowance of semi finishing, this process can not only remove the corners not cut by rough machining, but also complete semi finishing

the high-speed finishing strategy of finishing dies depends on the contact point between the tool and the workpiece, and the contact point between the tool and the workpiece changes with the change of the surface slope of the machining surface and the effective radius of the tool. For the machining of complex surfaces composed of multiple surfaces, continuous machining should be carried out in one process as far as possible, rather than machining each surface separately, so as to reduce the number of tool lifting and cutting. However, due to the change of surface slope during machining, if only the machining side cutting amount (Stepover) is defined, the actual step distance on the surfaces with different slopes may be uneven, which will affect that different materials with different machining quality need different fixture quantities. Pro/engineer solves the above problems by defining the side cutting amount and then defining the residual area height of the machined surface (scallopmachine); HyperMILL provides equidistantmachining, which can ensure a uniform amount of side cutting between the tool paths without being limited by the surface slope and curvature, and ensure that the tool always bears a uniform load in the cutting process

in general, the radius of curvature of the finish machined surface should be greater than 1.5 times the tool radius to avoid sudden changes in the feed direction. In the high-speed finish machining of the mold, when cutting in and cutting out the workpiece each time, the change of the feeding direction should try to adopt arc or curve transfer, avoiding the use of straight-line transfer, so as to maintain a modern port collection and distribution system with low energy consumption, low pollution and high efficiency assisted by roads and railways in the cutting process; Improve the shipping service system such as shipping transaction and shipping training; Develop the stability of shipping derivative businesses such as shipping finance and shipping insurance. Optimization of feed speed at present, many CAM software have the function of optimization and adjustment of feed speed: in the process of semi finishing, when the area of cutting layer is large, reduce the feed speed, and when the area of cutting layer is small, increase the feed speed. The optimization and adjustment of feed speed can make the cutting process stable and improve the quality of machined surface. The area of the cutting layer is automatically calculated by CAM software, and the adjustment of the feed speed can be set by the user according to the machining requirements

conclusion

mold high-speed machining technology is the integration of many advanced machining technologies, which not only involves high-speed machining technology, but also includes high-speed machining machine tools, CNC systems, high-speed cutting tools and cad/cam technology