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The application of MasterCAM lathe module in compound lathe machining

mastercam is a PC based cad/cam software developed by CNC software company of the United States. It is equipped with low hardware configuration requirements, convenient operation and powerful functions. It has functions from part modeling to tool path generation and post-processing. Nowadays, the machining parts tend to be complex, the precision of parts is getting higher and higher, and the number of NC machining axes is increasing. Manual programming can not meet the requirements of modern machining. Using CAM software programming has become an effective means for modern NC machining to improve programming efficiency and solve complex parts machining and multi axis machining

the lathe module of MasterCAM has rich menu functions and convenient modeling. In the tool path, there are not only rough and finish machining of various shape cycles, thread and inner hole cycles, but also integrated machining of c-axis, surface and grooving. Especially in surface machining, c-axis can automatically program and process surfaces without fixed logic relationship, which solves the problem of machining programs that cannot be written manually or solved by macro programs. The two-dimensional and three-dimensional machining of the c-axis tool path in the lathe module expands and improves the machining range of the NC turning center

1 application of turning milling composite machining

1.1 adapter shaft parts

as shown in Figure 1, the adapter shaft parts are composed of cuboid and shaft parts. The axis of the cuboid and the front shaft is coaxial in X direction, the axis distance in Y direction is 4mm, and the limit deviation of eccentricity is ± 0.005mm. The shape and position tolerance of this part is required to be high, and the parallelism and perpendicularity are required to be 0.02mm. If the parts are processed according to the turning and milling procedures respectively, the milling clamping will lead to repeated positioning and clamping errors after the turning of the parts. It is difficult to ensure that the shape and position tolerance of the parts and the eccentricity dimension of the axis of the front end shaft and the cuboid shape of 4 ± 0.005mm are controlled within the tolerance range. By using and developing the milling composite processing of the lathe module of MasterCAM software, all processes can be completed in a single clamping to ensure the dimensional accuracy and line position tolerance requirements of the products

(a) lattice module modeling (b) design modeling

Fig. 1 adapter shaft

1.2 adapter ring parts

when the adapter ring parts are processed according to the traditional process, after the turning process is completed, it is necessary to carry out milling processing. It is difficult to process and clamp the milling machine. The hole position accuracy tolerance between the inner ring center and the six opposite adapters is 0.02mm. Turning milling is processed in different processes, which is difficult to meet the requirements. The lathe module of CAM software is used for programming to carry out turning and milling composite machining. The shape and inner cavity can be clamped on the hating T42 composite turning and milling center at one time, and cut off with a cutting knife, which ensures the overall length of the workpiece and its tolerance requirements, and saves a processing procedure

1.3 three axis linkage

machining joint parts, the common method is macro programming, but macro programming has certain conditions, it can only be written according to a certain logical relationship, and automatic programming can overcome the defects of macro programming. As long as the actual shape of the product can be created, the selected cutting tools, tool paths and selected cutting parameters can be determined, the machining program can be quickly generated according to the shape, Improve the efficiency of programming and expand the processing range of CNC equipment

2 research on post-processing interpolation methods

various workpiece contours, most of which are composed of basic elements such as straight lines and arcs, can directly generate tool paths. If the machining contour is composed of conic and high-order curve, the machining tool path needs to be fitted with the minimum straight line and arc elements. This fitting method is interpolation. It is that the NC device generates the basic linetypes such as straight line and arc according to certain methods according to the limited data during programming, and completes the fitting of the required contour trajectory on this basis

in the automatic programming of lathe module, two different interpolation methods, namely software data sampling interpolation and polar coordinate interpolation, are used to carry out 2D and 3D turn milling composite processing for products

2.1 data sampling interpolation

the data sampling procedure for the post-processing of the adapter shaft is shown in the figure below. The experiment continues after the oil cylinder is reset. Rdquo; the digital servo valve is not reset 2

Figure 2 transfer shaft post-processing data sampling interpolation program segment

it can be seen from the program segment of the milling process of the lathe module that the program generated by the module is a data sampling interpolation method. Data sampling interpolation is to divide the given contour curve into the feed segment of each interpolation cycle, that is, the contour step. In each interpolation cycle, perform an interpolation operation to calculate the coordinates of the next interpolation point, so as to calculate the feed rate of each coordinate in the next cycle. The data sampling interpolation method does not get the feed pulse, but the feed rate expressed in good decimal when the load when the material is damaged should fall in the second and third quadrants of the experimental machine. The computer regularly samples the actual position of the coordinates, compares the sampled data with the command position, obtains the position error, and then controls the servo system according to the position error to eliminate the error

for straight-line interpolation, the straight-line segment of the moving point moving in one cycle coincides with the given straight-line. For arc interpolation, the straight-line segment of the moving point moving in one interpolation cycle approximates the arc with chords, and the interpolation uses a small segment of straight-line to approach the given trajectory. The interpolation output is the distance of each axis to move in the next interpolation cycle. It is not necessary to perform pulse equivalent interpolation every step, so as to achieve a higher feed speed

2.2 polar interpolation method

Figure 3 shows the polar interpolation procedure for post-processing of transfer shaft

Figure 3 polar interpolation subroutine segment for post-processing of transfer axis

polar interpolation method of G112 is used by the controller to interpret several data and determine the method and speed that each axis must move to the command end point. The coordinate system adopts polar interpolation method, and each programmed end point is distributed on this plane as coordinates. When composite machining is carried out in this way, it should be pointed out that when the polar interpolation processing instruction is effective, The following g codes can be used: G01, G02, G03, G40, G41, G42, G65, g98. When polar interpolation is effective, G00 positioning is not allowed. When polar interpolation is used, the unit of c-axis command is mm or inch, not degrees. When the command is c-, the spindle will rotate in the forward direction, and when the command is c+, the spindle will rotate in the reverse direction. Before commanding the c-axis, the M23 profiling mode must be used to start the c-axis. G113 cancel polar interpolation

2.3 comparison of the two interpolation methods

the data sampling interpolation output is the distance to be moved by each axis in the next interpolation cycle, and it is not necessary to perform pulse equivalent interpolation every step. For polar coordinate interpolation, the computer can calculate and judge the machining deviation point by point in the process of controlling machining, so as to control the coordinate feeding and process the required workpiece according to the specified graphics. The interpolation is completed through the steps of computer deviation discrimination, feed deviation calculation and end point discrimination

it can be seen from the two program segments in Figure 4 and figure 5 that in the processing of the same part, the byte amount of the program segment generated by data sampling interpolation is about 80% larger than that of the polar coordinate interpolation method. When the memory of CNC system is small and the system does not support DNC machining and external memory card calling, and the memory is not enough to store the generated processing program bytes, it can be considered to try to complete the turning milling compound machining of parts by polar coordinate interpolation

3 parameter setting and correction in the automatic programming of composite machining

during the turn milling composite machining, the product modeling shall be carried out first. Before generating the machining tool path, the software will require the operator to input the parameters such as the diameter of the milling tool used in the tool parameters. In the milling parameters, the tool compensation direction G41 or G42 used, the milling depth and the milling depth and compensation method of each tool of z-axis layering shall be input, which shall be directly compensated by the computer, Controller compensation, two and two reverse compensation modes can be selected. With different correction methods, CAM software will automatically generate the corresponding machining contour track

4 conclusion

although we have adopted a large number of multimedia teaching methods, fully developed the lathe module of MasterCAM software, and used its interpolation method to produce products that are more in line with the market demand, we can carry out 2D and 3D turning milling composite processing of product parts on hating T42 turning milling composite center, improve programming efficiency, and avoid repeated positioning errors caused by multiple clamping of products, The dimensional accuracy requirements of the product are ensured. (end)

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