Design, Processing and Inspection of Geometric Angle of Turnable Turning Tools

March 27, 2024

With the popularity of CNC machine tools, the range of applications for indexable turning tools is expanding. The indexable turning tool is fast in the processing, stable in size, and can be quickly replaced after the blades are worn, thus significantly improving the machining efficiency and saving the tool cost. 1 Design of indexable turning tool geometry The position of the indexable turning tool insert groove is mainly determined by the main declination angle kr, the blade inclination angle ls and the rake angle g0. Table 1 Rotary turning tool angle of declination Recommended values Processing conditions Main declination angle kr Recommended value Roughing system technology Rigidity better 45°~75° Rigidity of the processing system is 75°~90° Roughness of the finishing system is good 45 ° Process system rigidity is poor 60°~75° Slender shaft and thin-walled parts 90°~95° Workpiece middle cut-in, profiling 45°~60°, 90°~95° Table 2 Indexable turning angle Recommended value Processing conditions Blade inclination ls Recommended value Finishing car 0°~5° Rough turning car -5°~0° Intermittent cutting -5°~0° Processing hardened steel -5°~-10° Table 3 Indexable car Knife angle recommended value Workpiece material front angle g0 Recommended value Rough turning car Low carbon steel 13°~20° 20°~25° Carbon structural steel (normalizing) 10°~15° 13°~17° Carbon structure Steel (tempered and tempered) 5°~10° 8°~13° Alloy structural steel (normalizing) 8°~13° 10°~15° Alloy structural steel (tempered and tempered) 5°~8° 5°~10° Grey Cast iron (HT15-32, 20-40) 5°~10° 5°~10° High-strength steel -5° -5° Table 4 Indexable turning angle recommended value of workpiece Turning angle recommended value of workpiece material Ordinary steel 5° ~12° Ordinary cast iron 6°~8° High-strength steel 10°~15° Wear-resistant cast iron 8°~12° Lead angle kr Lead angle The lifespan of an indexable turning tool Larger. In general, reducing the lead angle can increase the tool life. However, when the process system or the workpiece is not rigid enough, reducing the main deflection angle will increase the radial force, thereby increasing the deformation deflection, causing processing vibration, reducing the machining accuracy and machining surface quality, and at the same time affecting the tool life. Therefore, Different lead angles are selected for different processing conditions. See Table 1 for the recommended lead angle when designing the tool. The blade inclination ls blade inclination also has a great influence on the cutting performance of the indexable turning tool. When cutting, the size of the blade inclination influences the chip flow direction. When finishing a car, in order to avoid the flow of chips and scratch the machined surface, the blade angle is often taken as a positive value. In addition, the size of the blade inclination will also affect the cutting edge sharpness. When designing the tool, the recommended value of the blade inclination is shown in Table 2. The size of the rake angle of the rake angle g0 directly affects the strength and sharpness of the cutting edge. Increasing the rake angle reduces chip distortion, makes cutting lighter and increases tool life. However, if the rake angle is too large, the strength of the cutting edge will be weakened and the chipping will be easy. This will shorten the tool life. There are many factors affecting the selection of the rake angle of the indexable turning tool, and the design recommendation values ​​are shown in Table 3. In the design of the indexable turning tool, the rake angle of the blade itself is also an important parameter and should be taken into consideration. The relief angle is mainly used to reduce the friction between the flank surface and the transition surface during cutting. When designing an indexable turning tool, it is necessary to comprehensively consider the back angle and the front angle. After selecting the back angle of the insert, the back angle of the insert groove is determined according to the front angle of the insert groove. Refer to Table 4 for the recommended design values ​​for the corner of the turning tool. Modeling Design and Drawing Labeling The labeling of turning tool turning parameters is shown in Figure 1.

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Fig. 1 Drawings of cutting parameters for turning tools

When using AutoCAD 2000's physical functions to design an indexable turning tool, first select the insert according to the machining conditions, and then subtract the rake and back angle of the insert itself to determine all the parameters needed to design the indexable turning tool. In the solid modeling design, the blade cannot be rotated exactly according to the desired blade angle and rake angle, but it should be converted into the normal forward angle. The conversion formula is tangn=tang0cosls. (1) The sequence of blade rotation during solid modeling should be: Main angle → blade angle → normal angle. 2 Indexable turning tools can be used in the milling of indexable turning tools, which can better ensure the dimensional accuracy of tool manufacturing, but the processing cost is higher. The use of ordinary milling machines to process turning tools is cheap, However, it is usually only possible to machine a simple turning tool with a rake angle of 0°. The author through a lot of practice on the design and processing of turning tools, summed up in the ordinary milling machine processing with a compound angle (ie, the blade inclination and rake angle are not 0 °) can be turned tooling process.

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Figure 2 Coordinates of the axis of rotation with four rotary axis flat nose pliers

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Figure 3 Coordinates of the rotary axis with three rotary axis flat nose pliers

When machining the turning tools in small batches on an ordinary milling machine, it is best to use the universal flat pliers as a fixture. The more rotary axes the universal flat nose pliers have, the more convenient the machining, but the relatively rigid structure of the flat pliers is relatively poor. When using a universal flat-nose pliers with four rotating shafts (see Figure 2) to clamp and machine the indexable turning tool, first clamp the turning tool and turn the shaft 1 to form the main declination angle of the turning tool; then turn the shaft 3 to form the car. The blade angle of the knife; then turn shaft 2 to form the forward angle of the turning tool. At this time, the bottom surface of the insert pocket is parallel to the plane of the table. According to the selected car blade, the shaft 4 is then rotated so that one side of the blade slot is parallel to the horizontal axis of the table, and then the turning tool can be milled. After machining a back wall, turn shaft 4 and rework the other insert groove back wall. If a universal rotary cutter with three rotating shafts (see Fig. 3) is used to clamp the indexable turning tool, the rotation sequence differs from that of the four-axis parallel cutting tool. Turn the shaft 1 first, and turn the angle according to the formula (2). Calculate; then turn axis 2 and calculate the angle of rotation according to formula (3). At this time, the bottom surface of the sipe is parallel to the horizontal plane of the machine tool, then you can turn axis 3 and start milling processing as described above. Tanq=tang0/tanls (2) tang=(tan2g0+tan2ls)1⁄2 (3) When large quantities of indexable turning tools are processed on an ordinary milling machine, horns placed on both sides and the bottom surface of the turning tool can be used to adjust the angle. The horn can also be fixed on the pliers (at this time, the workpiece can be clamped using a flat pliers with only one rotation axis). 3 Detection of indexable turning tool angle Detection of main declination angle kr The indexable turning tool is placed on the universal tool microscope. The angle f between the cutting tool side base surface and the main cutting edge is measured. Then the formula kr= The main declination kr can be calculated by 90°-f. The detection of the blade inclination angle ls and the relief angle a0 will place the indexable turning tool on the flat plate, and directly measure the blade inclination angle ls and the relief angle a0 with the universal angle ruler. When detecting ls, it should be measured along the direction of the main cutting edge; when detecting a0, first measure an along the direction perpendicular to the main cutting edge, and then calculate a0 according to the formula tana0=tanancosls. The detection of other dimensions of turning tools can refer to the detection methods of ordinary turning tools.

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