Turning of the hottest conical slender shaft

2022-08-26
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Turning of conical slender shaft

the ratio of diameter to length (l/d) of slender shaft is generally greater than 20. During turning, the rigidity of machine tool workpiece tool process system is poor, and the workpiece is very easy to bend and vibrate, especially the processing tensile strength and yield strength increase with the increase of machining rate, and the stiffness of conical part is worse. In addition, due to the poor thermal diffusivity of the slender shaft, the linear expansion of the workpiece caused by the cutting heat during the cutting process will also make the workpiece prone to waist drum shape, fried dough twist shape, bamboo shape and other defects, and it is not easy to obtain satisfactory surface roughness and geometric accuracy. Therefore, when turning tapered slender shafts, the key is to improve the stiffness of the process system, which has high requirements for tools, machine tools, auxiliary tools and process methods

as shown in Figure 1, the material of the slender shaft is 45 steel. Due to the large aspect ratio, high surface accuracy requirements, and the difficulty of turning the conical part, it is difficult to meet the quality requirements by using conventional machining methods. Through analysis, the designers formulated a reasonable process plan, which effectively avoided the bending deformation caused by the cutting force when machining the cylindrical excircle according to the relevant data, enhanced the rigidity of the workpiece when machining the conical part, reduced the vibration in the machining process, improved the machining quality of the conical slender shaft, and achieved good machining results

Figure 1 workpiece size figure

1 Turning of slender shaft excircle

when machining the F.03 excircle of the workpiece, the clamping method shown in Figure 2 is used to install the workpiece. In order to reduce the vibration and bending deformation of the workpiece during car cutting, the reverse cutting method is used in the machining process

1. Steel ring 2 Heel rest 3 Workpiece 4 Spring center

Figure 2 Schematic diagram of reverse tool walking turning clamping

first, put an open steel ring 1 on the outer circle of workpiece 3, so that the workpiece is in line contact with the jaw (the steel ring plays the role of universal adjustment), extend it into the chuck and clamp it with the jaw

drill a cylindrical hole at the other end of the workpiece as a center hole, so that the center is in line contact with the cylindrical hole, so as to eliminate the jerky phenomenon when the workpiece rotates; The retractable spring center 4 is used for the tailstock center, so that the workpiece can be axially retracted to compensate for the expansion caused by cutting heat. At the same time, the tool heel 2 is equipped with three supporting claws, and the spring supporting claw is adopted at the bottom. The supporting surface of the supporting claw is matched with the workpiece. Tensile test of the three supporting claws of the heel rest and the hair of the turning tool group during cutting: this experiment is mainly used for manufacturers of shampoo, hair dye and gel to form two pairs of radial pressure to balance the radial force generated during turning. The main deflection angle of the turning tool is k=75 °~ 90 °, and the front angle is g=15 °~ 20 °, and the circular arc cutting groove is ground to reduce the back cutting force and increase the axial cutting force

2. Turning of conical part

turning of conical part requires the transformation of the turret and cross tool holder of the horizontal lathe (see Figure 3). Fix a flat plate 10 on the horizontal knife rack, install a rotatable U-shaped plate 8 on the flat plate 10 with the stud 9 as the rotation center, rotate it to the required value according to the taper of the conical part of the slender shaft, and then fix it on the flat plate 10 with screws 7. A shaft 6 is fixed on the U-shaped plate 8, and the turning tool handle 5 slides on the shaft 6 with its bushing hole. At the same time, a fork shaped workpiece support 3 is fixed on the turret 4, the workpiece 1 enters the fork through the bushing 2 of the fork shaped support 3, the inner side of the fork is slotted, and the turning tool enters the fork through the slot for turning. Since the tool handle 5 is also fixed on the turret 4, when the turret 4 is pushed towards the machine head, the turning tool has more and more requirements for the valve, and the slender axle car entering the fork becomes a cone as shown in the figure

1. Workpiece 2 Bushing 3 Fork support 4 Turret 5 Turning tool handle 6 Shaft 7 Screw 8 U-shaped plate 9 Stud 10 Flat plate

Figure 3 clamping and turning diagram of conical part

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