RU2212309C2 - Device for vibration cutting - Google Patents

Abstract

FIELD: material turning by cutting, machining of difficult work materials. SUBSTANCE: device has separate drive, oscillating mechanism made in form of eccentric bushing, and tool holder. To reduce cutting force, chip crushing and to increase tool stability, device is provided with additional bearing support, connecting rod and torsion bushings. In this case, additional bearing support is installed on eccentric bushing. Connecting rod is installed on additional bearing support and hinged with tool holder, which is installed on axle parallel to connecting rod axis, and torsion bushings are located in hinges of connecting rod and tool holder. EFFECT: higher efficiency of use. 4 dwg

Description

 The invention relates to the turning of materials by cutting with the imposition of forced vibrations on the cutting tool and can be used to improve the machinability of parts, including large ones, from hard-to-process materials in various engineering industries.

 Known works in which the positive effect of the imposition of vibrations on the processes of shaping are investigated. Forced vibrations are set by the following types of vibrators: mechanical, electromagnetic, electrodynamic, magnetomechanical, hydraulic, hydromechanical, hydrodynamic, electrohydraulic, pneumatic, magnetostrictive and piezoelectric. Practice has shown that devices with mechanical type vibrators are most preferred because of their versatility, ease of manufacture and maintenance.

 A vibratory cutting device is known in which axial vibrations are reported to the top of the cutting tool, that is, in the direction of the longitudinal feed (along the axis of rotation of the workpiece) [1]. Vibrations in the axial direction provide an increase in the rake angle (the effect of sharpening the cutting edge) and satisfactory roughness (Ra = 2.5 μm). However, the cutting tool has a short life.

 A vibration cutting device is known in which radial vibrations are reported to the top of the cutting tool, that is, in the direction of the transverse feed (perpendicular to the axis of rotation of the workpiece) [1]. Vibrations in the radial direction provide a decrease in the average value of the cutting resistance, contribute to chip crushing, but worsen the surface roughness and reduce the resistance of the cutting edge of the tool.

 A device for vibrational cutting is known in which tangential vibrations are reported to the top of the cutting tool, that is, in the direction tangent to the surface of the workpiece [1]. Vibrations in the tangential direction provide a reduction in cutting forces, an increase in the tool life, while the roughness of the machined surface is the same as with conventional cutting.

 Known vibration cutting devices in which the top of the cutting tool report vibrations that simultaneously combine two or three directions [2].

 The closest in technical essence and the achieved result is a device according to copyright certificate 429892 in class B 23 B 25/02, publ. 1974 [3]. In this device, the top of the cutter, mounted on the horizontal with the axis of rotation of the workpiece, from a separate drive, using a swing mechanism made in the form of an eccentric shaft with bearing bearings paired with an eccentric sleeve, reports harmonic oscillations in the direction of the plane crossing the direction of the longitudinal feed. The known device [3] contains a base on which the rack is mounted, a drive for communicating to the tool holder mounted on the support with an insert, oscillatory motion in a plane crossing the direction of the longitudinal feed, and a swing mechanism made in the form of an eccentric shaft with bearing supports paired with an eccentric a sleeve on which a cracker is mounted, sliding in the extension socket of the tool holder to convert rotational motion into reciprocating. The insert has two base surfaces mating with the stand: one flat, facing the part, and the other, equidistantly located relative to the axis passing through the tip of the cutter.

 A disadvantage of the known device is the presence of gaps between the cracker and the socket for the extension of the tool holder in the swing mechanism, which leads to the loss of part of the oscillations of the cutter, the appearance of sliding friction and noise during operation and, as a result, rapid wear and jamming of the mechanism.

 The technical result of the invention consists in improving the machinability of hard-to-work materials by informing the top of the cutting tool of pendulum-type harmonic vibrations in which the amplitude of the vibrations must have tangential and radial components functionally related to each other, and in eliminating the loss of the amplitude of vibrations, replacing the sliding friction by rolling friction, eliminating noise during operation, rapid wear and jamming of the mechanism due to the elimination of gaps in the hinges and elements reformation of movements.

The essence of the proposed device lies in the fact that when vibrating cutting the tip of the cutter mounted on the horizontal with the axis of rotation of the workpiece, from a separate drive using a swing mechanism made in the form of an eccentric shaft with bearing bearings paired with an eccentric sleeve, harmonic oscillations of the pendulum are reported types whose amplitude has tangential (A _τ ) and radial (A _r ) components, functionally related to each other.

 The essence of the proposed device lies in the fact that the device for vibration cutting consists of a separate drive, a swing mechanism made in the form of an eccentric shaft with bearing bearings and an eccentric sleeve, and a tool holder. The proposed device further comprises a bearing support, connecting rod and torsion bushings, while the bearing bearing is mounted on an eccentric sleeve, the connecting rod is mounted on the bearing support and pivotally connected to a tool holder that is mounted on an axis parallel to the connecting rod axis, and the torsion bushings are placed in the connecting rod hinges and tool holder. The bearing support eliminates gaps in the swing mechanism and replaces sliding friction with rolling friction. Torsion bushings due to elastic shear deformations eliminate sliding friction and gaps in the hinges of the connecting rod and tool holder. The use of a bearing support and torsion sleeves eliminates the loss of the amplitude of oscillations, noiseless operation, reliability and durability of the device design are achieved. The proposed arrangement of the connecting rod ensures that there is no phase shift between the movements of the crank, the length of which is formed by the eccentric shaft paired with the eccentric sleeve, and the tip of the cutter, i.e. the maximum deviation of the crank will correspond to the maximum deviation of the tip of the cutter.

 The invention is illustrated by drawings, where shown in figure 1 is a schematic diagram of the implementation of the proposed method; figure 2 - the trajectory of the top of the cutter; figure 3 - device for implementing the proposed method, top view; figure 4 is the same, view from the right.

Из ΔС_обрС_рабD найдем угол отклонения вершины резца:
sinα = 0,5•ε•L $\genfrac{}{}{0ex}{}{\text{-1}}{\text{1}}$ . (2)
Подставив формулу (2) в (1) найдем значения тангенциальной (A_τ) и радиальной (А_r) составляющих амплитуд:

где ε - длина кривошипа АВ;
L₀ - величина вылета вершины резца;
L₁ - длина коромысла CD.Schematic diagram of the proposed depicted in figure 1. The following links are distinguished in the mechanism: A and D - axis of rotation, rigidly fixed to the base; AB - crank with a length ε, which is formed by an eccentric shaft paired with an eccentric sleeve; BC - connecting rod; CD is a rocker with a length of L ₁ , DE is the magnitude of the protrusion of the tip of the cutter L ₀ equal to the distance from its tip to the swing axis D (i.e., E is the tip of the cutter), V is the speed of rotation of the workpiece, ω is the angular speed of the crank AB. A feature of vibrational cutting using pendulum-type vibrations is the combined action of vibrations in the tangential and radial directions. Figure 2 schematically shows the paths of oscillation of the tip of the cutter, where the dashed line shows the tip of the cutter in the extreme positions, and the main - in the middle position; EE _slave and SS _slave - working stroke, EE _arr and SS _arr - reverse stroke of the apex of the cutter and rocker, respectively; α is the angle of deviation of the tip of the cutter. From the known mathematical dependencies, it is obvious that, considering the ΔDEE _slave , it is possible to determine the tangential (A _τ ) and radial (A _r ) components of the amplitudes:

From ΔС _arr C _slave D we find the angle of deviation of the tip of the cutter:
sinα = 0.5 • ε • L $\genfrac{}{}{0ex}{}{\text{-1}}{\text{1}}$ . (2)
Substituting formula (2) in (1) we find the values of the tangential (A _τ ) and radial (A _r ) component amplitudes:

where ε is the length of the crank AB;
L ₀ - the magnitude of the departure of the tip of the cutter;
L ₁ - the length of the rocker CD.

The proposed device provides a reduction in cutting forces, crushing chips, increase the resistance of the cutting tool and a satisfactory surface roughness. The cutting force is reduced due to the facilitation of the chip formation process, since during the processing, the speed of the vibrational movement of the tip of the cutter is superimposed on the usual cutting speed, creating the total effect of the dynamic effect. The presence of the radial component And _r , that is, the horizontal movement of the tip of the cutter, contributes to the separation of chips from the workpiece and its crushing. The resistance of the cutter increases by reducing the cutting force and friction forces along the rear surface of the tool during the reverse course of the path of oscillation of the tip of the cutter. In addition, the presence of intermittent contact of the cutting edge with the workpiece provides periodic cooling and allows more effective penetration of coolant into the cutting zone. The dynamic nature of the cutting process facilitates chip formation due to the hydrodynamic pressure of the liquid penetrating through the capillary slots on the chip elements upon contact of the cutting edge with the workpiece.

 The proposed device is shown in FIGS. 3 and 4. The device comprises an electric motor 1, a vibrator housing 2 and a box-shaped tool holder 3, which are mounted on the plate 4. The electric motor 1 is connected by a V-belt transmission, consisting of pulleys 5, 6 and belt 7, with an eccentric shaft 8 , which is installed in the housing of the vibrator 2 on the bearings 9, fixed by removable covers 10 with seals. The clearances in the bearing bearings 9 are adjusted by means of a spline nut 11. Between the pulley 6 and the removable cover 10, a distance sleeve 12 is mounted. An eccentric sleeve 13 is mounted on the eccentric shaft 8. A connecting rod 15 is installed through the bearing 14 through the pin 14. The connecting rod 15 by means of the pin 16 and torsion bars the bushings 17 are connected to the tool holder 3, the latter being mounted on an axis parallel to the connecting rod axis. The tool holder 3 has a half shaft 18, which are installed by the torsion bushings 19 in the earrings 20.

 The tool holder 3 is intended for orienting and securing the tool and communicating harmonic oscillations of the pendulum type to it. The design of the tool holder 3 allows you to use standard cutters and adjust the position of the tip of the cutter relative to the swing axis so that they are on the same horizontal line with the axis of rotation of the workpiece.

 The device operates as follows.

 Using an electric motor 1, through the pulleys 5, 6 and the belt 7, the rotation is transmitted to the eccentric shaft 8. The main parameter of the processing process is the oscillation frequency of the tool, and the secondary is the amplitude. The amplitude of the oscillations is smoothly regulated from zero to a maximum by turning the eccentric sleeve 13 on the eccentric shaft 8, followed by fixing and fixing. The eccentric shaft 8 is paired with the eccentric sleeve 13 forms a link of variable length ε, that is, the crank AB (figure 1). The magnitude of the amplitude is measured on a dial on the right end of parts 8 and 13. The frequency of oscillation of the tool is changed by rearranging the pulleys 5, 6 and depends on the gear ratio of the belt drive, which also serves to prevent the impact of shock loads on the motor shaft and protect the structure from breakage when overloaded. Rotation from the eccentric shaft 8 paired with the eccentric sleeve 13 through the bearing 14 and the connecting rod 15 by means of the pin 16 and the torsion sleeves 17 is transmitted to the tool holder 3, which, relative to the axis of rotation of the axle shafts 18, resting through the torsion sleeves 19 on the earrings 20, performs harmonic oscillations of the pendulum type .

где М_k=P_z•L₀ - крутящий момент;
P_z - главная составляющая силы резания;
L₀ - длина вылета вершины резца;
d - наружный диаметр торсионной втулки;
D - внутренний диаметр торсионной втулки.To eliminate sliding friction and gaps in the hinges C and D (see Fig. 1), the torsion sleeves 17 and 19 are mounted with an interference fit on the pin 16, the tool holder 3, the axle shafts 18 and the earrings 20, and the oscillatory movement is transmitted due to elastic shear deformations:

where M _k = P _z • L ₀ - torque;
P _z is the main component of the cutting force;
L ₀ - the length of the departure of the tip of the cutter;
d is the outer diameter of the torsion sleeve;
D is the inner diameter of the torsion sleeve.

 Bearing support 14 mounted on the eccentric sleeve 13 eliminates gaps in the swing mechanism and replaces sliding friction with rolling friction. The use of a bearing support and torsion sleeves eliminates the loss of the amplitude of oscillations, noiseless operation, reliability and durability of the device design are achieved. The location of the axis of the connecting rod 15 parallel to the axis of the tool holder 3 ensures that there is no phase shift between the movements of the crank, the length of which is formed by the eccentric shaft paired with the eccentric sleeve, and the tip of the cutter, i.e. the maximum deviation of the crank will correspond to the maximum deviation of the tip of the cutter.

 The oscillation frequency and amplitude are set based on the diameter of the part, the material being processed and the processing mode. Moreover, the frequency, if possible, is chosen to be the maximum from the range of low-frequency vibrations, in order to localize vibrations in the cutting zone and prevent their transfer to the machine and technological equipment.

Sources of information
1. Poduraev V. N. Processing by cutting with vibrations. M.: Mechanical Engineering, 1970, 350 p.

 2. Kumabe D. Vibration cutting. M .: Engineering, 1985, 424 p.

 3. A. p. 429892 USSR, cl. At 25 b 25/02. Device for kinematic crushing of chips during turning / G.A. Radoshchekin, V.A. Lyubimov, Yu.A. Shoelaces Publ. in B.I. 1974, 20.

Claims (1)

 A device for vibration cutting, containing a separate drive, a swing mechanism made in the form of an eccentric shaft with bearing bearings paired with an eccentric sleeve and a tool holder, characterized in that it is equipped with an additional bearing support, connecting rod and torsion bushings, while the additional bearing support is mounted on eccentric sleeve, the connecting rod is mounted on an additional bearing support and pivotally connected to the tool holder, which is mounted on an axis parallel to the axis of the connecting rod, and the torso nnye sleeve placed in the joints of the connecting rod and the tool holder.

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