introduction Process planning is an important part of CNC turning programming. Reasonable planning can effectively increase production efficiency and improve the surface quality of parts. At present, the numerical control turning process planning method of conventional parts has been studied more mature, and the corresponding CAM software system has been developed, which provides a powerful tool for NC automatic programming. However, there is a type of part in turning programming, which is characterized by a complex cross-sectional profile and different sizes of daily blanks. This is due to the fact that China's mechanical processing equipment is relatively backward and the precision of rolled blanks is low. At this point, the programming is usually performed in accordance with the maximum blank size. As a result, air cutting occurs and the processing efficiency is reduced. The goal of CNC turning process planning is to pursue a single-piece man-hours-minimum (high-productivity) or minimum-to-wood ratio, and boundary constraints are no geometrical interference and process interference. Therefore, in the numerical control system with the cutting force detection function, for the numerical control processing of the workpiece with large manufacturing error of the blank, the machining allowance of the blank can be measured online using the cutting force sensor, and the cutting of different parts of the wheel can be determined according to the machining allowance. Process parameters (cutting thickness, number of passes, etc.) can be used to process different blanks in different blanks to save processing time. In this paper, we will take the CNC turning of train wheels as an example to describe the principles of on-line measurement, measurement methods, and tool trajectory generation methods for large-diversity revolving parts during turning, and to discuss the method of determining feed and cutting speed. 1 blank machining allowance online measurement Fig. 1 is a half-section view of a train wheel. Since the blank is produced by hot rolling, the size of the blank is not uniform, so the machining allowance is not uniform. The number of passes and the number of passes can be determined by the on-line measurement of the blank machining allowance. The depth of cut of the knife. The on-line measurement of the machining allowance requires the use of the cutting force detection function of the CNC system. The force detection system is mounted on the tool holder. The core of the force detection system is a force sensor that converts the force signal into a voltage signal and transmits it to the CNC through a serial communication protocol. A threshold value (usually set as the yield limit σs for the wheel material chromium manganese steel) can be preset in the sensor. When the tool comes into contact with the workpiece and begins cutting, the cutting force suddenly increases. When the cutting force reaches the set threshold, the CNC system will automatically end the cutting of the current measurement block and record the X and Z coordinates of the current position of the tool. After calculating the margin of a certain part, it is stored in the CNC system. From the viewpoint of appearance, when the tool comes into contact with the workpiece, it is retracted, that is, only one tool is cut at one measuring point. 1.2 Measurement Methods It can be known from the machining allowance measurement principle that the normal cutting of the tool is performed along the workpiece ICI during measurement. Figure 2 shows the machining allowance online measurement. In the figure, A (x, y) points are the planned measuring points, the tool radius is R, and the normal cutting of the tool along the workpiece table ICI is measured at the time of cutting, and the unit normal vector of the cutting allowance of the T may not be calculated. The direction is opposite to the direction vector EA in the measurement cut-in section. Let θ be the angle between the feed direction and the horizontal line, then n = (cos, sinθ ). The total cutting allowance ttotal = A0-R = (R601-x) / cosθ -R, set the finishing allowance to t, then from the total residue can be calculated as roughing allowance t = ttotal - tr = (R601- x)/cosθ-R-tr. The known machining allowance is ttotal, the infeed path is D→E→0, and the retract path is O→F→G. Let the maximum depth of cut be tmax, then the roughing cycle number N is 1.3 Margin Measurement Tool Planning The process planning of the measurement process includes the determination of measurement points, measurement cut-in section planning and measurement cut-out section planning. In order to ensure the accuracy of the machining allowance measurement, it is necessary to ensure that the tool cuts into the workpiece along the normal direction of the part surface when measuring the cutting section. 2 Process Planning 2.1 Cut-in section and cut-out section planning When different workpieces are machined, the tool may be cut into different ways. Common cutting, cutting, and cutting directions are normal, tangential, and oblique, and can be determined according to the starting position, the ending position, and the geometry of the adjacent surfaces of the surface to be machined. Proper planning of cutting-in and cutting-out direction can prevent or reduce the impact of the tool cutting in and cutting out the workpiece. 2.2 Cutting section planning Blanks with low manufacturing precision (for example, large machining allowances, large eccentricity, large curvature, or non-uniform margins, etc.) When CNC machining, machining by conventional methods may damage the tool or even cause it to fail. In this case, several special types of processing methods can be used. (1) Variable feed cutting: When the tool enters the cut-in section, gradually increase the feed amount. This method is used when the eccentricity of the blank is large. (2) Intersection cutting: After the current step has finished a certain knife, it jumps to the next step to carry out cutting, and after the knife of the next step is completed, it continues to complete the unfinished step of the current step. So repeated. This method requires the use of ten workpieces with a large curvature of the contour and a daily machining allowance. (3) Multi-pass cutting: When cutting several times, the tool cutting-in point and cut-out point can be changed to prevent overcutting of the tool when the tool has a large capacity at the entry point or at the cut-out point. This method is used when the machining allowance is particularly large in a certain area. (4) Constant-line-speed cutting: For example, when cutting a spoke, if the rotational speed of the boring axis is constant, the cutting speed varies greatly throughout the entire path of the tool path. Cutting at constant line speed is the ideal solution. Figure 3 is the result of planning the K860B wheel using the above-mentioned step planning principles and planning method. In the figure, the dashed line is the advance/retreat knife path. The data such as "1010" is the current step ID. Feed rate is usually selected based on experience. During roughing, the feed rate is selected based on the material to be machined, the size of the tool shank, the diameter of the workpiece, and the depth of the knife. For semi-finishing and finishing, according to the roughness requirements, the feed is selected according to the workpiece material, the arc radius of the tip, and the cutting speed. The cutting speed is usually selected based on experience. Roughing vehicles often choose lower cutting speeds, and high cutting speeds can be selected for finishing vehicles. In addition, a reasonable cutting speed must be determined by taking into consideration factors such as the processing performance of the material, the cutting performance of the tool, and the operating conditions. 3 Processing planning data storage 3.1 Storage of Individual Step Data The process planning process is carried out in a human-machine graphic interactive manner. The work step is the base of the process planning and data access. The data of the work step is composed of two parts: the tool data and the cutting process data. The tool data includes tool number, tool compensation method, etc. The cutting process data includes cutting parameters, cut-in sections, cutting sections, cut-out sections, and step intersections. The data structure of any step is as follows: 3.2 Data storage between steps Each process is composed of a number of steps. The planned data can be modified at any time. This requires that the storage structure of these data can be easily added, modified, deleted, and the alignment of the left and right tool holders can be achieved. task. Using a doubly-linked list to store this data ensures that the process planning process is flexible enough. There are two pointer fields in the nodes of the doubly-linked list. One of them points to direct successors, and the other points to direct progenitors. The data structure is defined as follows: The extended data segment is a custom data format provided by the CAD platform, with which it is convenient to access different types of data (including graphic data and non-graphic data) in the entity according to different needs. Any voxel in the integrated product model can be supplemented with auxiliary data and referenced as attribute data or attribute connection data. For example, linestrings, polygons, and curves behave similarly at design time. The head information is followed by the number of vertices, followed by the coordinates of the vertices. The number of appearances of these types in a single child is limited. The difference between a polygon and a line string must be the same for the first and last vertices of the ten polygons. For the curve, there are two "extra" points at the beginning and end of the vertex set, and ten is used to determine the curvature of the endpoint. Extending entity data is based on conventional graph data, and adds data blocks formed by combining a series of classification codes, which together with conventional data form a more general entity data. Ten different applications require access to different data, so the extended entity data is grouped by application type in the following form: In this paper, the on-line measurement method, process planning method, and planning data storage method for blanks with uneven dimensions in the turning process planning are described. The essence of this method is to change the processing method for a single fixed cutting amount, and the number of variable cuttings is used. The method of changing the cutting amount achieves different cutting methods for different blanks, thereby effectively improving the processing efficiency. The double linked list data structure is used to store each step data, and an extended data segment is used to add the step data structure table of the double linked list structure to the numerical control processing model, which is advantageous to improve the simplicity and high efficiency of the code in the numerical control programming post processing. Solar Panel Frame is one of the important components in solar module. 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1.1 Measurement principle 
When the tool center X-radius coordinate is R601 when the tool tip contacts the workpiece, then the distance A between the point A on the finished contour and the shank O is (R601-X)/cos θ. 
The symbol "[]" in the formula does not round up. In actual programming, the depth of cut of the knife is treal, = t/N. The product profile is first translated tr distance in the normal direction, and then translated N times, and then the translation distance is treal, tool trajectory can be obtained. 
2.3 Selection of Feed Rate and Determination of Cutting Speed
Process planning data storage is divided into three steps: storage of individual process data, data storage between processes, and integrated storage of process data. 
Due to the large amount of data in the work step, adopting a structure to record this information can coordinate the internal relationship of the data. 
3.3 Integrated storage of step data 
4 Conclusion