Correct selection of tools and programming for CNC machine tools (2)
December 11, 2022
CNC machining tool selection
The selection of the tool is carried out in the human-computer interaction state of the NC programming. The tool and tool holder should be selected correctly according to the machining capacity of the machine tool, the performance of the workpiece material, the machining process, the amount of cutting and other relevant factors. The general principle of tool selection is: easy installation and adjustment, good rigidity, durability and high precision. Under the premise of meeting the processing requirements, try to choose a shorter tool holder to improve the rigidity of the tool processing.
When selecting a tool, the size of the tool should be adapted to the surface size of the workpiece being machined. In the production, the peripheral contour of the plane parts is often processed by an end mill; when milling the plane, the cemented carbide insert milling cutter should be selected; when the bosses and grooves are machined, the high-speed steel end mill is selected; the surface of the blank is machined or roughed. For the hole, the corn milling cutter with the carbide insert can be selected; for the machining of some three-dimensional and variable bevel contours, ball-end milling cutters, ring milling cutters, conical milling cutters and disc milling cutters are often used.
In the free-form surface (mold) processing, since the cutting speed of the end of the ball-end tool is zero, in order to ensure the machining accuracy, the cutting distance is generally the tip-tight distance, so the ball head is often used for the finishing of the surface. The flat-blade tool is superior to the ball-end knives in terms of surface quality and cutting efficiency. Therefore, the flat-blade knives should be preferred if the surface is roughed or finished under the premise of ensuring no cutting. In addition, the durability and accuracy of the tool are highly dependent on the tool price. It must be noted that in most cases, the choice of a good tool increases the tool cost, but the resulting processing quality and processing efficiency increase. , can make the entire processing cost greatly reduced.
Spindle speed n (r/min). The spindle speed is generally selected based on the cutting speed v. The calculation formula is: V=pnd/1000. The control panel of the CNC machine tool is generally equipped with a spindle speed trimming (magnification) switch, which can adjust the spindle speed during the machining process.
Feed rate Vf. The vF should be selected based on the machining accuracy and surface roughness requirements of the part as well as the tool and workpiece material. The increase in Vf can also increase production efficiency. When the surface roughness of the machined surface is low, the Vf can be selected to be larger. During the machining process, Vf can also be manually adjusted by the trim switch on the machine control panel, but the maximum feed rate is limited by the stiffness of the equipment and the performance of the feed system.
With the wide application of CNC machine tools in production practice and the formation of quantitative production lines, CNC programming has become one of the key issues in CNC machining. In the process of programming the NC program, it is necessary to select the tool and determine the amount of cutting in the human-computer interaction state. Therefore, the programmer must be familiar with the selection method of the tool and the principle of determining the amount of cutting, so as to ensure the processing quality and processing efficiency of the part, give full play to the advantages of the CNC machine tool, and improve the economic efficiency and production level of the enterprise.
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