RU2367565C1 - Method of pulsed needle milling of surfaces - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: device comprising casing with wire frieze bundles gets rotation and lengthwise feed. Processed workpiece receives reciprocation. Proposed device creates additional interference. Device casing represents a plate with radial slots arranged on its end face to accommodate the plates with cutting elements representing aforesaid bundles of wire frieze. The latter represent V-like bent metal wires with their one end rigidly attached perpendicular to the plate plane and their other end making cutting surface. The ends of the said bundles are bent towards the casing periphery. The casing is arranged in shell made up of two lap-jointed rings that allow varying shell height. One end of the said shell allows its rigid attachment. The shell other face has recesses and ledges in contact with bent out ends of wire frieze bundles to straighten the said ends when bundles run on ledges to create aforesaid additional interference.

EFFECT: expanded performances, higher efficiency, lower costs.

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Description

The invention relates to mechanical engineering technology, in particular to methods for finishing and hardening processing of spherical surfaces of parts, for example, automobile ball fingers made of steels and alloys by needle milling or surface plastic deformation (PPD) with static and pulse loading of a tool.

A cylindrical brush and a method of machining with it are known, comprising a holder with cylindrical sockets mounted on the housing, in each of which a glass with a pile of tufts is placed, and an elastic element located under the glasses and in contact with the housing, the glasses being freely installed in the sockets, each socket on the inner surface has an annular groove, and on the outer surface of the glass an annular protrusion is made, the width of which is less than the width of the groove of the socket, and the elastic elements are placed in the grooves of the housing In addition, elastic elements are mounted on the reflector [1].

The known cylindrical brush and the processing method implemented by it have limited technological capabilities, do not allow cutting irregularities of considerable depth, do not allow controlling the force of pressing the tufts of pile to the surface to be treated, i.e. do not allow you to control the depth of cut, which reduces productivity and processing quality.

A known method and device for processing incomplete spherical surfaces of PPD parts, in which rotational movement is reported to the workpiece and the deforming tool, and the deforming device is told to rotate in a circle lying in a plane offset from the center of the processed spherical surface, while the angular velocity of the deforming device is associated with angular velocity ratio ω workpiece _yn >> ω _d, moreover, given the mathematical relationship between effort n immersion and force burnishing [2].

The known method is characterized by low efficiency, high energy intensity, not sufficiently large depth of the hardened layer and a low degree of hardening of the treated surface.

The objective of the invention is to expand the technological capabilities of needle milling or PPD through the use of pulsed loading of a cutting or deforming tool, which allows you to control the depth of the cutting or hardened layer, the degree of hardening and the surface microrelief, as well as improving the quality, accuracy and productivity of processing by using a multi-element cutting or deforming tool.

The problem is solved using the proposed method of finishing processing of spherical surfaces, including the message of the rotational movement of the workpiece, longitudinal feed and rotational movement relative to its axis by a needle mill for processing the workpiece with an interference fit and applying to the waveguide using a striker periodic pulse load generated by a hydraulic pulse generator, when This uses an acupuncture containing a housing with radial grooves and a stepped hole, and a working tool in de beams of pile of metal wires, V-shaped bent inside the body with the formation of a working concave spherical surface with a radius equal to Ri, mm, where R is the radius of the processed spherical surface, mm, i is the interference fit, mm, the tufts of pile are made in the form of cutting or deforming elements, while placing the waveguide in the stepped opening of the housing, and the periodic impulse load is applied from the condition of providing additional movement of the metal wires of the tufts of pile, straightening them and creating additional body interference.

The essence of the proposed method of finishing processing of spherical surfaces is illustrated by drawings.

Figure 1 shows the setup for processing the workpiece of an automobile ball finger installed in a special device based on the conical surface of the shank, according to the proposed method at the time before switching on the stroke, a longitudinal section; figure 2 - diagram of the processing of the workpiece automobile ball finger installed in a special device based on the conical surface of the shank, according to the proposed method at the time of the pulse loading of cutting or deforming elements - tufts of pile; figure 3 is a cross section aa in figure 2; figure 4 - element B in figure 1, where the thin lines show the position of the metal needles of the pile of the pile under the action of a pulsed load P _IM on the needle cutter.

The proposed method of finishing processing is used for needle milling or surface plastic deformation (PPD) - hardening of spherical surfaces 1 with periodic pulsed loading of the tufts of pile 2 from V-shaped metal wires curved into the body. In this case, the workpiece 3 being machined, for example, an automobile ball finger, is provided with a rotational motion V _З , and with cutting or deforming elements - a rotational motion V _И and a longitudinal feed S _PR for the purpose of feeding and pressing them to the center О of a spherical surface.

The housing 4, which is a hydraulic cylinder, is hollow and a nut 5 with a collar 6 is installed on the external surface of the thread from the end face. Housing 4 rotates from an individual drive (not shown) and the striker 7 and the waveguide 8 are located in it.

In the radial grooves at the end of the body 4, cutting or deforming elements 2 are installed, made in the form of pile bundles of metal wires V-shaped inwardly curved into the body, forming a working concave spherical surface with a radius (Ri) mm, where R is the radius of the processed spherical surface 1 of the workpiece 3, mm; i - interference, mm. The tufts of the needle-cutter pile are fastened with a nut 5 with a shoulder 6 or other known methods.

A waveguide 8 is placed in the opening of the housing 4, which is impacted by the firing pin 7, creating a periodic impulse load P _И , generated by a hydraulic pulse generator (GGI) (not shown), which is connected to the housing 4 [3-5]. The periodic impulse load P of the _IM waveguide is aimed at additional communication of the movement of the metal wires of the pile beams 2, straightening them and creating an additional tightness.

The tufts of pile 2, forming a working cutting concave spherical surface, are located at the end of the housing 4 radially relative to the longitudinal axis of the tool. The tufts of pile 2 from one end are rigidly fixed, for example, by welding on a plate, therefore, when they are straightened under the action of P _{IM with the} other end, they act on the workpiece, cutting off the allowance or hardening the machined surface (see Fig. 4).

The housing 4 with a needle cutter 2 is fed to the workpiece in the longitudinal direction S _PR until it comes into contact with the tufts of pile and another amount of interference, which creates a static load P _ST , while the tufts of pile will bend even more (see figure 1), processing spherical surface of the workpiece. Thus, by changing the amount of interference by approaching or removing the tool in the direction S _PR, the depth of cutting or hardening is controlled in the static mode of operation of the device.

When exposed to the end of the waveguide 8, the striker 7, which are coaxially mounted in the housing 4, creates a pulse load P _IM by hitting the waveguide on the curved parts of the tufts of pile, straightening them (see figure 2). Such a static-pulse mode allows you to intensify the process of finishing processing by needle milling or hardening.

With prolonged use of the needle cutter, the tufts of the pile will wear out unevenly. Before dressing, release nut 5, the tufts of tufts are shifted in the radial grooves to the center and fix with nut 5. To correct the cutting properties and the required size (R-i), a straightening diamond tool is used that has the shape and dimensions of the workpiece spherical surface.

To process the workpiece, for example, the upper ball pin 2101-2904187 on the lathe, a special electromechanical device 9 is used (Fig.1-2), which allows the installation, basing and fixing of the workpiece on a pre-machined conical surface of the shank.

A hydraulic pulse generator (not shown) is used as a mechanism for impulse loading of the needle cutter [3, 4]. Rotary movements are reported to the workpiece and the needle cutter, while the needle cutter is also provided with a longitudinal feed. A periodic pulsed P _IM load is applied in the direction of longitudinal supply to the curved part of the tufts of pile, trying to straighten them, and to direct the needles radially to the center of the spherical surface being treated.

The periodic impulse load P _{IM is} carried out using the striker 7, acting on the end of the waveguide 8. As a result of the striking of the striker on the end of the waveguide, shock and oppositely directed pulses of the same amplitude and duration arise in each striker, each of which will affect the pile beams and the processed surface with a cycle equal to double pulse duration. Having reached the surface to be treated, the shock pulse is distributed on the passing and reflecting. The transmitted pulse forms a dynamic component of the deformation force, which intensifies the cutting process or strengthens the surface layer of the processed spherical surface.

The ability to rationally use the energy of shock waves is determined by the size of the instrument.

When moving the striker from the bottom up, according to Fig.1-2, the bent tufts of pile absorb a periodic impulse load P _{IM of the} waveguide, due to which the lower parts of the needles move upward, straighten and radially approach the work surface, increasing the interference fit.

The total longitudinal periodic impulse load P _{IM of the} striker along the waveguide is perceived by the bent part of the pile bundles and is evenly distributed to each needle. This means that each bunch of pile with its needles has a cutting or hardening effect with a pulse load directed to the surface to be treated.

A periodic pulsed P _IM load is applied in the direction of the longitudinal feed and, thanks to the design features of the device, direct it to the center of the surface to be treated.

The periodic impulse load P _IM must be greater than the total force required for the deformation of the tufts of pile and the force necessary for cutting or hardening. The removal of the waveguide and the striker after impact in the initial position (according to Fig.1-2, down) is due to the elasticity of the tufts of the pile and the return of the bent part to their original free V-shaped state. In order to mitigate the impact of the waveguide on the body during the removal of the waveguide, a damper 10 is installed at the end of the body, for example, in the form of a rubber ring.

As a result of the impact of the striker on the end face of the waveguide and the waveguide along the V-shaped curved tufts of the pile, the latter act on the surface to be treated with the cyclicity set by the hydraulic pulse generator. The possibility of rational use of the energy of shock waves is determined by the size of the beams.

The incomplete spherical surface of the workpiece being processed forces the longitudinal axis of the device to be set at an angle α relative to a plane perpendicular to the longitudinal axis of the workpiece and passing through the center of the sphere.

The accuracy of the shape of the processed spherical surface of the workpiece by the proposed method increases and decreases the roughness due to the self-centering and self-installation of the tufts of pile along the treated surface when it is beating and vibrating.

To carry out finishing cutting processing (with chip removal), it is necessary that the hardness and tensile strength of the material of the wire elements of the pile be 1.5 ... 2 times higher than these parameters of the material of the workpiece, the ratio l / i, where i is the smallest radius of inertia of the transverse the cross section of the wire elements was in the range of 50 ... 100, and the coefficient K _{p the} density of the wire pile in the range of 0.7 ... 0.9; while the tightness should be H = 0.7 ... 1.5 mm.

The operating modes can be recommended as follows. The peripheral speed for finishing processing is 2 ... 5 m / s. The longitudinal feed is determined by the formula S = L _protr n (mm / min), where n is the rotational speed of the device, min ^-1 ; the value of L _protrusion (mm) depends on the interference and the diameter of the disk and is determined empirically or by calculation.

Tests during the finishing treatment (with removal of chips) of the workpiece by the proposed method showed that scale is cut off from the treated surface along with the hardened layer; in the process of needle milling due to the elasticity of the working surface of the device, the treated surface is not hardened, the pressing force of the device to the workpiece surface is 200 ... 600 N per 10 mm of the width of the working surface of the device, and the tangential component of the cutting force is 150 ... 550 N.

For finishing processing with removal of chips by the proposed method, it is necessary to comply with the conditions

To _p = p / σ _in = 1,5 ... 2,0,

where p is the pressure during acupuncture, MPa;

σ _in - the tensile strength of the material of the workpiece, MPa.

The choice of the appropriate pressure p depends on the physicomechanical properties of the material of the wire pile, on the rigidity and density of the latter, as well as on the interference fit [6].

If the device that implements the proposed method works as a hardening, then the depth of the hardened layer reaches 0.5 ... 1.5 mm, which is significantly (1.5 ... 2 times) more than with traditional PPD. The greatest degree of hardening is 15 ... 25%. As a result of processing the proposed method in comparison with traditional PPD, the effective depth of the layer, hardened by 20% or more, increases by 1.5 ... 2.2 times, and the depth of the layer hardened by 10% or more, by 1.3 ... 1 , 6 times.

Example. To assess the quality parameters of the surface layer hardened by the proposed method, experimental studies of the processing of an automobile ball finger were carried out using the developed device configured to work as a hardening one. The workpiece of the ball upper finger 2101-2904187, installed in a special electromechanical device, was strengthened on the machine mod. 16K20 using a device using GGI [3-5]. The blank is made of steel 20X GOST 1050-74. Sulfofresol (5% emulsion) was used as the cooling lubricant. Processed a sphere with a diameter of 32.7 ± 0.1; the initial roughness parameter Ra = 3.2 μm, achieved - Ra = 0.63. The values of technological factors (impact frequency, feed rate, rotation speed of the workpiece and tool) were chosen in such a way as to ensure the multiplicity of impact on the elementary area of the treated surface in the range of 6 ... 10. A further increase in the multiplicity of the deforming effect leads to softening.

Given the overrun of the tool, the workpiece was completely processed in 1.25 ... 1.5 turns; the speed of the deforming elements - V _And = 50 m / min (n _And = 500 min ^-1 ); the longitudinal supply of the S _PR device was carried out manually until an interference was created between the deforming elements and the machined surface of 0.3 ... 1.6 mm.

The required roughness and accuracy of the spherical surface were achieved in T _m = 0.81 min (against T _m ^bases = 2.75 min according to the basic version with the traditional rolling treatment at the Oryol steel mill OSPAZ). The control was carried out by an indicator bracket with an indicator ICh 10 B cells. 1 GOST 577-68 and on the profilometer mod. 283 type AN GOST 19300-86. In the processed batch (equal to 100 pcs.) Defective parts were not found. The deviation of the treated surface from sphericity was not more than 0.02 mm, which is permissible.

The magnitude of the force of the pulsed beams of the pile on the treated surface was P _ИМ = 255 ... 400 kN. The depth of the layer hardened by pulsed processing is 3 ... 4 times higher than with traditional rolling. The hardened layer during traditional rolling is formed under long-term action of large static forces. The proposed method, a similar depth of the hardened layer is achieved as a result of a short-term impact on the deformation zone of a prolonged energy pulse.

Studies of the stress state of the hardened surface layer by pulsed processing showed that the maximum residual stresses are close to the surface, as when chasing, which is favorable for most of the interfaced parts of mechanisms and machines. A comparison of the depth of the stressed and hardened layer, the stress gradient and the hardening gradient shows that the depth of the stressed layer is 1.1 ... 1.3 times greater than the depth of the riveted layer, which is consistent with the theory of surface plastic deformation. Processing showed that the roughness parameter of the machined spherical surfaces decreased to Ra = 0.32 ... 0.63 μm with the initial value Ra = 3.2 ... 6.3 μm, the productivity increased more than three times compared to traditional rolling. The energy intensity of the process decreased by 2.2 times.

Microvibrations during processing favorably affect the working conditions of the instrument - tufts of pile of acupuncture. The imposition of a small amplitude oscillatory motion leads to a more uniform distribution of the load on the tool, causes additional cyclic movements of the contact surfaces of the tool and the workpiece, facilitates the formation of a hardened surface. Fluctuations contribute to a better penetration of the cutting fluid (coolant) into the treatment area. When vibration is applied, the deforming elements of the tool periodically “rest”, which helps to increase their resistance. Processing under vibration conditions dramatically increases the efficiency of the cooling, dispersing and plasticizing action of the coolant due to the facilitation of its access to the contact zone of the tool and the workpiece.

The proposed method, implemented by the developed device, extends the technological capabilities of pulsed cutting or surface plastic deformation by controlling the depth of the sheared or hardened layer and the microrelief of the spherical surface by using the device and a special tool with a large number of cutting or deforming elements, which allows to increase productivity and reduce manufacturing costs due to simplicity of design.

Information sources

1. A.S. USSR 824969, MKI ³ A46V 7/10. Cylindrical brush. Berkov B.V. 2809273-12; 08/08/79; 04/30/81. Bull. No. 16.

2. RF patent 2031770, MKP ⁶ V24V 39/04, 39/00. A method for processing incomplete spherical surfaces of PPD parts. Gavrilin AM, Samoilov N.N. 5045958/27; 04/14/92; 03/27/95. Bull. No. 9.

3. RF patent 2098259, MKI ⁶ V24V 39/00. Lazutkin A.G., Kirichek A.V., Soloviev D.L. Method of static-pulse treatment by surface plastic deformation. 96110476/02, 05.23.96; 12/10/97. Bull. Number 34.

4. Kirichek A.V., Lazutkin A.G., Soloviev D.L. Static-pulse processing and equipment for its implementation // STIN, 1999, No. 6. - S.20-24.

5. RF patent 2090342. Lazutkin A.G., Kirichek A.V., Soloviev D.L. Water hammer device for processing parts by surface plastic deformation. 1997. Bull. Number 34.

6. Gavrilenko I.G. A method of combining preliminary and final needle-milling stripping of cylindrical parts // Automation and modern technology. - 1992. - No. 9. - S.27-30.

Claims (1)

A method of finishing processing of spherical surfaces, including communicating rotational movement of the workpiece, longitudinal feed and rotational movement relative to its axis with a needle mill for processing the workpiece with an interference fit and applying to the waveguide using a striker a periodic pulse load generated by a hydraulic pulse generator, characterized in that they use a needle mill, containing a housing with radial grooves and a stepped hole and a working tool in the form of bundles of pile of metal wires V -like-curved inwardly of the body with the formation of a working concave spherical surface with a radius equal to Ri, mm, where R is the radius of the processed spherical surface, mm, i is the interference fit, mm, the tufts of pile are made in the form of cutting or deforming elements, while the waveguide placed in a stepped hole of the housing, and a periodic impulse load is applied from the condition of providing additional movement of the metal wires of the tufts of pile, straightening them and creating additional interference.

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