RU2291761C1 - Combined milling method by means of needle milling cutter at strengthening openings - Google Patents

Abstract

FIELD: manufacturing processes in machine engineering, working materials by cutting.

SUBSTANCE: method comprises steps of imparting lengthwise feed to tool having body with seats provided with turning on their inner surfaces for freely mounting bushings with working surfaces in the form of wire pile bundles and imparting rotation to blank. In order to enlarge manufacturing possibilities due to controlling depth of cut-off layer and micro-relief of worked surface, tool is used in seats of which additional bushings are arranged for preliminarily knurling of worked surface and for surface plastic deforming. Said bushings are arranged according to blank rotation sign in next succession: bushing for preliminarily knurling, bushing with pile bundles, bushing for surface plastic deforming. Tool body is in the form of mandrel with radial seats having rectangular cross sections. On outer surface of bushing whose shape is reciprocal to that of seat shoulder is formed. In turning of seats for bushings with pile bundles compression spring is arranged. Said spring rests upon shoulder of bushing and creates static load at needle milling. In turnings of seats for bushings used for preliminary knurling and for surface plastic deforming, compression spring and ring are arranged. Said spring displaces bushings to center of tool and it rests upon said shoulder of bushing. Ring is arranged on periphery of mandrel and it has openings for working surfaces of sleeves. Bottom of bushings is inclined by acute angle to plane normal relative to lengthwise axis of bushing and it engages with cone surface of wave-guide arranged in central lengthwise opening of mandrel. Striker acts upon end of wave-guide and it creates pulse load acting upon bushings. Striker is mounted in central lengthwise opening of mandrel along the same axis and it is driven from hydraulic pulse generator. Helical cylindrical compression spring acts upon opposite end of wave-guide. Radial extension of bushings is regulated by means stop limiting lengthwise motion of wave-guide at side of said spring.

EFFECT: enlarged manufacturing possibilities of method.

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Description

The invention relates to mechanical engineering technology, to the processing of materials by cutting, in particular to intensive machining by acupuncture of the holes of metal blanks with simultaneous hardening.

A known method of processing a cylindrical brush containing a holder mounted on the casing with cylindrical nests, each of which contains a glass with a pile of pile, and an elastic element located under the glasses and in contact with the housing, the glasses are installed in the nests freely, 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, on other elements mounted reflectors [1].

The known method, implemented by a cylindrical brush, does not allow cutting irregularities of considerable depth, does not allow you to control the force of pressing the tufts of pile to the work surface, i.e. it does not allow to control the depth of cut, which reduces productivity and processing quality.

The objective of the invention is the expansion of technological capabilities by controlling the depth of the cut layer and the microrelief of the inner surface, the intensification of the process by applying a constant static load and a variable impulse load, which allows to improve the quality, productivity and to harden the processed surface by using a special tool containing three varieties of work items : working elements for preliminary notching the treated surface, working ementy with bundles of wire pile for iglofrezerovaniya and operating elements for the surface plastic hardening.

The problem is solved by the proposed combined method of needle milling with hardening of holes, including a message to the tool containing the housing with sockets having a recess on the inner surface, in which glasses with working surfaces in the form of bundles of wire pile, longitudinal feed, and the workpiece are rotationally placed, moreover glasses for preliminary notching of the treated surface and glasses for surface plastic control are additionally placed in the tool sockets in the following sequence along the rotation of the workpiece: a glass for preliminary notching, a glass with tufts of pile, a glass for surface plastic hardening, a glass with tufts of pile, etc., while the casing is made in the form of a mandrel with radially located nests, in cross section representing a rectangle, and on the outer surface of the glass, having a shape corresponding to the shape of the nest, a flange is made, and in the recess of the nests under the glasses with tufts of pile there is a compression spring abutting against the aforementioned drill the teak of the cup and creating a static load on the needle milling, in addition, in the recesses of the nests under the cups for preliminary notching and surface plastic hardening there is a compression spring that moves the cups to the center of the tool and abuts against the mentioned bead of the cup and a ring that is installed on the periphery of the mandrel and having holes the working surfaces of the glasses, while the bottom of the glasses is made at an acute angle α to a plane perpendicular to the longitudinal axis of the glass and is in contact with the conical surface with an angle α of the waveguide, which is located in the central longitudinal hole of the mandrel, in addition, the hammer acts on the end of the waveguide, creating an impulse load on the cups, coaxially mounted in the central longitudinal hole of the mandrel and driven by a hydraulic pulse generator, and a screw end acts on the opposite end of the waveguide a cylindrical compression spring, the radial extension of the cups being regulated by an emphasis restricting the longitudinal movement of the waveguide from the side of the aforementioned spring.

Features of the processing of the holes of the proposed method are illustrated by drawings.

Figure 1 presents the tool, a longitudinal section bB in figure 2 and the hole processing diagram; figure 2 is a General view from the left along A in figure 1; figure 3 is a longitudinal section bb in figure 2; figure 4 is a General view of the tool; in Fig.5 - element G in Fig.1, the scheme of cutting a bundle of wire pile pre-incised surface.

The proposed combined method relates to needle milling with simultaneous hardening of the machined surface of the holes and includes a message to the tool 1 of the longitudinal feed S _CR , and the workpiece 2 - rotational movement V _C Tool 1 contains glasses with working elements of three varieties: glasses for preliminary notching 3 of the treated surface, glasses with bundles of wire pile 4 for acupuncture of the left allowance and glasses for finishing, hardening treatment 5 with surface plastic deformation.

The tool 1 contains a housing with sockets 6, in each of which freely placed glasses 3-5.

Glasses in the housing are placed in the following sequence along the rotation of the workpiece 2:

- glass 3, the working surface of which is made in the form of a multi-blade chisel. The pulse action on the glass with a force P _imp leaves transverse grooves on the surface to be treated in the form of a preliminary notch of the surface to be applied, applied to facilitate cutting allowance and hardening of the surface layer in the grooves;

- glass 4 with bundles of wire pile, cutting by needle milling. The pulse effect on the glass with a force of P _imp allows you to intensify the cutting process while hardening the treated surface;

- glass 5, which serves for the final finishing, hardening treatment with surface plastic deformation, and the pulse action on the glass with a force P _imp allows you to reduce, smooth the height of the microroughness;

- a glass 4 with tufts of pile for hardening the treated surface and so on.

The tool body is made in the form of a mandrel with radially located sockets 6, in cross section representing a rectangle. Each socket 6 on the inner surface has a recess 7, and on the outer surface of the glass 3-5, having a shape corresponding to the shape of the socket 6, a bead 8 is made.

In the recess 7 of the sockets 6 under the glasses 4 with bundles of wire pile there is a compression spring 9, abutting against the shoulder 8 of the glass 4. The compression spring 9 has the shape of a glass and is made screw. The spring 9 creates a static load on the bundles of wire pile P _article and seeks to move the cups 4 from the center to the periphery, acting on the surface to be treated with tufts of pile.

Due to the action of the springs 9, a static load P _{article is created} on the tufts of pile, acting normal to the workpiece surface being machined. The change in the stiffness of the springs 9 control the efficiency of needle-milling.

In the recesses 7 of the sockets 6 for cups 3 and 5 for preliminary notching and surface plastic hardening are located compression springs 10, abutting against the shoulders 8, and a ring 11, which is installed on the periphery of the mandrel and having holes for the working surfaces of the cups. The springs 10 constantly move the cups 3 and 5 to the center of the tool and do not allow contact with the work surface when the impulse load P _imp does not work.

The ring 11 also holds the glasses 4 with tufts of pile in the nests 6 when the tool is inoperative and outside the workpiece.

The bottom of the glasses 3-5 is made at an acute angle α to the plane perpendicular to the longitudinal axis of the glasses, and is in contact with the conical surface of the waveguide 12, which is made at an angle α to its longitudinal axis. The waveguide 12 is located in the Central longitudinal hole of the tool and in addition to the conical surface has a cylindrical part, which it mates with the surface of the Central longitudinal hole of the tool.

The end face 13 (right, according to FIGS. 1, 3) of the waveguide 12 is pulsed by the hammer 14 with a force P _imp coaxially mounted in the central longitudinal hole of the tool and driven by a hydraulic pulse generator (not shown) [2, 3].

On the other end 15 (left, according to FIGS. 1, 3) of the waveguide 12, a helical coil compression spring 16 acts, which, resting on the plug 17, constantly presses the waveguide 12 against the striker 14.

The radial departure of the glasses 3-5 is regulated by an abutment 18, which limits the longitudinal movement of the waveguide 12 and is in contact with its left (according to FIGS. 1, 3) end face 15. The abutment 18 is made in the form of a screw and screwed into the threaded hole of the plug 17.

A hydraulic pulse generator is used as a mechanism for impulse loading of a tool [2, 3]. The workpiece is given a rotational movement V _s , and the tool is given a longitudinal feed S _ave . A periodic pulsed P _imp load is applied in the direction of the longitudinal feed and, thanks to the clinoplunger mechanism, consisting of glasses with an inclined bottom and the conical part of the waveguide, they are directed normal to the surface to be treated.

The periodic impulse load P _{imp is} carried out using the striker 14, acting on the end 13 of the waveguide 12, which with its cone radially spreads glasses 3-5 with different working surfaces. The magnitude of the radial movement of the glasses 3-5 is regulated by the stop 18 by screwing it in or out from the plug 17. In order to divert the waveguide 12 after impact, the end face 15 of the waveguide is acted upon by a coil compression spring 16 (for example, taken in accordance with GOST 13766-68).

As a result of the impact of the striker 14 on the end face 13 of the waveguide 12, shock and oppositely directed pulses of the same amplitude and duration arise in the striker and waveguide, each of which will act on glasses 3-5 with different working surfaces and on the treated 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 process of preliminary notching, cutting and hardening of the surface layer of the hole being machined.

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

Example. To assess the quality parameters of the surface layer, processed and hardened by the proposed method, experimental studies of the processing of the liner using a special stand. The values of technological factors (impact frequency, tool radius, feed rate) were chosen in such a way as to ensure the multiplicity of impact and cutting impact on the elementary area of the treated surface in the range of 6 ... 10. A further increase in the multiplicity of the deforming and cutting effects leads to the appearance of large inertial forces and vibrations, which adversely affect the quality of processing.

Before starting a new tool, the working surface of the wire pile was ruled by grinding it in assembled form. A steel spring wire with a diameter of 0.5 ... 1.0 mm from 65G steel was used as a pile.

In the process of processing the inner surface of a rotating workpiece, bundles of wire pile inserted into the hole of the tool are pressed against it by interference N due to the action of the springs 9. In this case, the working elements for preliminary notching and surface plastic hardening do not touch the surface to be treated until the impact impulse P _imp Due to the discontinuous working surface of the tufts of pile, the main force acting on the surface to be treated is carried out by the first wire elements of one bundle in the direction of rotation (see FIG. 5), having the largest free length l and deflection f. The wire elements adjacent to them elastically compress them, slightly increasing the concentrated total effect on the surface to be treated.

Under the action of a pulsed load P _imp on the working elements 3 in the form of a multi-blade chisel, the machined surface is pre-incised with the formation of transverse corrugations, the depth of which is not more than the allowance left for needle milling.

Notched flutes facilitate subsequent chip removal, reduce the deflection f of the wire elements of the pile bundle, improve quality and intensify processing.

To carry out cutting operations, 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 inertia radius of 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 - N = 0.7 ... 1.5 mm. The modes of operation of the tool can be recommended as follows. The peripheral processing speed is 2 ... 5 m / s. The longitudinal feed is determined by the formula S _CR = L · n (mm / min), where n is the workpiece rotation frequency, min ^-1 ; the value of L (mm) depends on the interference and the diameter of the tool and is determined empirically or by calculation.

Tests of the tool, working according to the proposed method, when processing a billet blank from a hot-rolled steel pipe 20 showed that it cuts off scale from the surface to be processed along with the left allowance; in the process of needle milling due to the impulse load and the radial reciprocating movement of the reinforcing working elements, the treated surface is hardened, the force of pressing the tufts of beams to the workpiece surface was 200 ... 600 N per 10 mm of the width of the working surface of the beams, and the tangential component of the cutting force equal - 150 ... 550 N.

For processing by the proposed method, it is necessary to comply with the conditions K _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 stiffness and density of the latter, as well as on interference N.

When treating metals with the proposed method, the hardness of the processed surface increases, as a result, the wear resistance of the treated surface and the quality of processing are improved, the roughness of the processed surface is reduced, and the processing productivity and tool durability are increased. The magnitude of the force of the pulse loading of the tool was P _imp = 255 ... 400 kN.

Production tests showed that the proposed method intensifies the processing process due to the impact of the pulse load on the working elements, as well as preliminary notching of the treated surface. The conditions for self-sharpening the wire elements of the pile are improved.

The method extends the technological capabilities of needle-milling in combination with preliminary notching and final hardening, improves the quality and productivity of processing due to the communication of low-frequency, independent of the tool rotation speed, radial vibrations to the pile beams, intensifies the process of needle-milling and hardening due to the application to the pile beams and working elements for surface plastic hardening of the radial pulsed force, as well as by increasing the area of contact of the tool with zag Preparations.

The advantage of the method is the ability to smoothly control the frequency and force of the pulsed load of the tool working elements, which makes it easy to optimize the processing process in production conditions when the material being processed, chemical-thermal operation, cutting wire tool elements, technical conditions, cutting conditions.

The 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.

The ultimate roughness value achieved during processing by the proposed method is R _a = 0.8 μm, a reduction of the initial roughness by a factor of 2.5 is possible.

Microvibrations in the process favorably affect the working conditions of the instrument. 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 surface of the tool periodically “rests”, which helps to increase its 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.

Thus, the proposed method allows to expand technological capabilities by controlling the depth of the cut layer and the microrelief of the treated inner surface, to intensify the process by applying a constant static load and a variable impulse load, which allows to improve the quality, productivity and harden the processed surface.

Information sources

1. A.S. USSR 824969, MKI ³ A 46 V 7/10. Cylindrical brush. Berkov B.V. 2809273-12; 08/08/79; 04/30/81. Bull. No. 16 is a prototype.

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

3. 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.

Claims (1)

A combined method of needle milling with hole hardening, comprising a message to an instrument comprising a housing with recesses having recesses on the inner surface, in which cups with working surfaces in the form of bundles of wire pile, longitudinal feed, and the workpiece are rotationally moved, characterized in that the tool is used , in the nests of which there are additionally placed glasses for preliminary notching of the treated surface and glasses for surface plastic hardening in sl traveling sequence along the rotation of the workpiece: a glass for preliminary notching, a glass with tufts of pile, a glass for surface plastic hardening, while the body is made in the form of a mandrel with radially located nests with a cross section in the form of a rectangle, and on the outer surface of the glass having the shape in the reciprocal shape of the nest, a collar is made, and in the recess of the nests under the glasses with tufts of pile there is a compression spring abutting against the said collar of the glass and creating a static load In the recesses of the nests under the cups for preliminary notching and surface plastic hardening, there is a compression spring that moves the cups to the center of the tool and abuts against the mentioned bead collar and ring, which is installed on the periphery of the mandrel and has openings for the working surfaces of the cups, while the bottom of the cups is made at an acute angle α to a plane perpendicular to the longitudinal axis of the glass, and is in contact with a conical surface with an angle α of the waveguide, which is located in the central longitudinal from at the same time, the tip of the waveguide acts on the end of the waveguide, creating a pulsed load on the glasses, coaxially mounted in the central longitudinal hole of the mandrel and driven by a hydraulic pulse generator, and a helical cylindrical compression spring acts on the opposite end of the waveguide, and the radial reach of the glasses is regulated by the stop, restricting the longitudinal movement of the waveguide from the side of the said spring.

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