CNC lathe tool selection principle?
Tool life is closely related to the amount of cutting. When setting the amount of cutting, you should first choose a reasonable tool life, and a reasonable tool life should be based on the optimization goal. Generally, it is divided into the highest productivity tool life and the lowest cost tool life. The former is determined according to the goal of the least piece of work, and the latter is determined according to the goal of the lowest process cost.
The following points can be considered when selecting the tool life based on tool complexity, manufacturing and sharpening costs. Complex and high precision tool life should be chosen to be higher than single-edged tools. For the machine clamp indexable tool, due to the short tool change time, in order to give full play to its cutting performance and improve production efficiency, the tool life can be selected to be lower, generally taking 15-30min. For multi-tool machines, combination machine tools and automatic machining tools with complicated tools, tool changes and tool adjustments, the tool life should be selected higher, especially for tool reliability. When the productivity of a certain process in the workshop limits the productivity of the entire workshop, the tool life of the process should be selected to be lower. When the total plant expenditure is shared in a certain process per unit time, the tool life should also be selected. In the case of lower part finishing, in order to ensure at least one pass and avoid changing the tool during cutting, the tool life should be determined according to the part accuracy and surface roughness. Compared with the ordinary machine tool processing method, CNC machining puts higher requirements on the tool, not only needs good quality, high precision, but also requires dimensional stability, durability, and the performance of the break and row performance is also convenient to install and adjust. Meet the high efficiency requirements of CNC machine tools. The tools selected for CNC machine tools often use tool materials that are suitable for high-speed cutting (such as high-speed steel, ultra-fine-grained carbide) and use indexable inserts.
CNC turning tools commonly used are general-purpose turning tools, pointed turning tools, circular turning tools and three types. The forming turning tool is also called the model turning tool, and the contour shape of the machined part is completely determined by the shape and size of the turning edge of the turning tool. In CNC turning, common forming turning tools include small radius arc turning tools, non-rectangular grooving knives and thread knives. In CNC machining, the turning tool should be used with little or no use. The pointed tool is a turning tool characterized by a linear cutting edge. The cutting edge of this type of turning tool consists of straight main and auxiliary cutting edges, such as 900 inner and outer turning tools, left and right end turning tools, grooving (cutting) turning tools and various outer and inner edges with small chamfering edges. Hole turning tool. The selection method of the geometric parameters of the pointed tool (mainly geometric angle) is basically the same as that of ordinary turning, but it should be comprehensively considered in combination with the characteristics of CNC machining (such as machining route, machining interference, etc.), and should take into account the tip of the tool itself. The strong second is a circular arc turning tool. The circular turning tool is a turning tool characterized by a circular arc-shaped cutting edge with a small roundness or line contour error. Each point of the turning edge of the turning tool is the cutting edge of the circular arc turning tool. Therefore, the cutting point is not on the arc but on the center of the arc. The circular turning tool can be used for turning the inner and outer surfaces, and is particularly suitable for turning various smooth joints (concave) forming surfaces. When selecting the arc radius of the turning tool, it should be considered that the arc radius of the cutting edge of the two-point turning tool should be less than or equal to the minimum radius of curvature on the concave contour of the part, so as to avoid the occurrence of shallow dryness. The radius should not be too small, otherwise it is not only difficult to manufacture. The tool cutter may be damaged due to the weakness of the tool tip or the poor heat dissipation of the tool body.
In CNC machining, flat-end end mills are commonly used for milling inner and outer contours of plane parts and milling planes. The empirical data of the parameters of the tool are as follows: First, the cutter radius RD should be smaller than the minimum radius of curvature Rmin of the inner contour surface of the part, generally taking RD= (0.809) Rmn. The second is the machining height of the part H < (1/4-1/6) RD to ensure that the knife has sufficient rigidity. The third is to use the flat-bottom end mill to mill the bottom of the inner groove. Because the bottom of the groove needs to be overlapped twice, the radius of the bottom edge of the tool is Re=Rr, that is, the diameter is d=2Re=2(R-η). When programming, the tool radius is Re=0.95 (Rr). For the machining of some three-dimensional and variable-angle contours, spherical milling cutters, ring milling cutters, drum milling cutters, conical milling cutters and disc milling cutters are commonly used.