How to choose the right way of cutting in CNC machining

Reasonable choice of knife-moving method 　　

1. Basic selection principles 　　

2. There are two points to consider when choosing the cutting method: one is the length of the processing time, and the other is whether the machining allowance is uniform. Generally speaking, the circular cutting method is based on the shape of the workpiece, and the machining allowance is relatively uniform. However, the machining allowance of the row cutting method is more uneven. If you want to leave a more uniform allowance after the row cutting, it is usually necessary to increase the circular cutting tool path around the boundary. If the requirement of margin unevenness is ignored, the tool path length of the line cutting tool is usually relatively short; if the unevenness of the margin is considered and the circular cutting tool path is increased, when the processing area boundary is longer (such as the case of multiple islands) , The circular cutting tool path around the boundary has a more obvious impact on the total processing time, and the horizontal cutting tool path is generally longer than the circular cutting tool path. The tool position of the row cutting tool is easy to calculate, and it takes up less memory, but there are more times of lifting the knife. When using a circular tool path, it is necessary to offset the ring boundary several times and clear the self-intersecting loop. 　　

2, choose according to the shape characteristics 　　

The shape feature of the workpiece determines the way of machining. According to the different processing individuals, the workpieces can be simply divided into plane-shaped cavities and free-form surfaces. Plane-shaped cavities are generally processed by row cutting. Since most of this type of workpieces are formed by overall blank milling, such as boxes, bases and other parts, the machining allowance is large. The row cutting method is conducive to maximize the progress of the machine tool. Feeding speed improves processing efficiency, and its cutting surface quality is also better than circular cutting processing. Free-form surfaces are generally processed by circular cutting, mainly because the curved surfaces are mostly castings or formed by regular shapes, and the margin is not uniformly distributed. At the same time, the curved surfaces have higher requirements for the accuracy of the molding surface; secondly, the circular cutting and row cutting methods are similar. It can approach the true shape of the surface better than having good surface processing characteristics. 　　

3. Choose according to processing strategy 　　

The processing of parts is often divided into three processing stages: rough processing, semi-finishing and finishing, and sometimes there are finishing stages. A reasonable division of the processing stages is necessary to ensure the processing accuracy. Due to the relatively single function of the machine tool, the traditional processing method can clearly see the boundary of each stage in the process route. However, the boundary of the CNC milling processing method is relatively fuzzy and may be mixed (such as precision in the roughing stage). The content of processing, the finishing stage may also have traces of rough machining), in order to ensure the quality of processing, the division of processing stages is also necessary in CNC machining, but in order to reduce the clamping time and simplify the tool movement, how to determine the stages The processing content and the considerations may be somewhat different from the traditional processing technology. 　　

The main goal of rough machining is to pursue the material removal rate per unit time and prepare the geometric contour of the workpiece for semi-finish machining. Therefore, the row cutting method or the compound method is often used for layer cutting. The main goal of semi-finishing is to make the contour of the workpiece smooth and the surface finishing allowance is uniform. Therefore, the ring cutting method is often used. The main goal of finishing is to obtain workpieces with geometric dimensions, shape accuracy and surface quality that meet the requirements. According to the geometric characteristics of the workpiece, the internal cutting method shall be adopted, and the circular cutting method shall be adopted for the edges and joints. 　　

4. Choose according to programming strategy When programming, the main principles for determining the cutting method are: it should be able to ensure the requirements of the machining accuracy and surface roughness of the parts; the processing route should be shortened as much as possible to reduce the idle movement time of the tool; the numerical calculation should be simple and the number of program segments should be small. To reduce programming workload. Generally speaking, for the plane-shaped cavity, the processing area is divided by the row cutting method to reduce the number of tool lifting; the free-form surface-like circular cutting method approximates the shape. The selected size of the blank shape will affect the choice of programming. By increasing the shape of the blank, the shape processing that is not easy to be clamped can be converted into the easy clamping line-cutting method and cavity processing; or the free-form surface processed by ring cutting can be changed to line Cutting way to a large margin to improve processing efficiency.