RU2349444C1 - Device for burnishing of screws - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: invention is related to technology of machine building, namely, to finishing of screw blanks by surface plastic deformation. Rotary motion and longitudinal feed are imparted to screw blank and device that comprises body and working deforming elements arranged in the form of helical cylindrical spring turns. Prior to start-up of longitudinal feed, cross-feed movement is imparted to spring with deforming elements, and it is put in contact with blank and guide block. Rotation from blank is imparted to mentioned spring, which is freely installed on elastic base on axis in body bearings. Guide block shaped as processed screw is used. Forced rotation is imparted to guide block from blank with speed equal to blank speed. In diametrally opposite place relative to guide block blank rests on support holder having support roller. Axes of support holder roller, blank, spring and guide block rotation are parallel. Interaxial distance between blank and guide block is calculated according to formula given in description.

EFFECT: technological resources of surface plastic deformation process are expanded, roughness parameter of processed surface is increased, its hardness is increased, as well as efficiency, and processing cost is reduced.

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Description

The invention relates to mechanical engineering technology, in particular to finishing processing by surface plastic deformation of screw blanks and other parts such as shafts made of steels and alloys and realized by multi-element deforming tools in the form of coil springs.

A known method of surface plastic deformation (PPD), carried out by a tool containing a housing, on the periphery of which elastic working deforming elements made in the form of turns belonging to a helical spring are rigidly fixed in grooves [1].

The disadvantages of this method are: narrow technological capabilities, low productivity in relation to the finishing, finishing processing of screws and other parts such as shafts due to the small contact patch of working elements with the treated surface, as well as low quality processing.

A known method of PPD, implemented by a rotating spring tool, in which on the outer surface of the disk holder is fixed a coil spring rolled into a ring [2]. Separate turns of the spring during the working rotation of the tool holder play the role of deforming elements that interact with the machined surface of the rotating workpiece mounted on a screw-cutting lathe.

The disadvantages of this method are: narrow technological capabilities that do not allow to process shaped surfaces, and low productivity due to the small number of deforming elements simultaneously participating in the processing, as well as hardening to a small depth.

The objective of the invention is the expansion of technological capabilities, which consists in improving the roughness parameter of the treated surface due to the sequential actions of a large number of deforming elements, in increasing productivity by increasing the contact spot of these elements with the surface being treated and the possibility of using large feeds and adjusting working forces, in reducing the cost of the process and cheaper tool manufacturing due to compactness and simplicity of design, in the ability to process difficult-shaped bodies of revolution and to neutralize the runout of the workpiece surface, which adversely affects the quality of processing, in unloading the nodes of the technological system: machine - tool - tool - workpiece from unilaterally applied effort, especially when processing non-rigid workpieces.

The problem is solved by the proposed method of rolling screws, including a message of rotational movement of the screw preform and longitudinal feed to a device containing a housing and working deforming elements made in the form of coils of a coil spring, and before turning on the longitudinal feed to the spring with deforming coils, a transverse feed is introduced and brought into contact with the workpiece and the copier, while the spring receives rotation from the workpiece, since it is mounted freely on an elastic basis on an axis in the bearings kach of the housing, and said copier has the shape of a machined screw and is shifted in the longitudinal direction by half a pitch of the screw so that, for example, the cavity of the screw blank is opposite the protrusion of the copier, and the copier has a forced rotation from the workpiece at a speed equal to the speed of the workpiece, and the same with it, in addition, in a diametrically opposite place relative to the copier, the workpiece rests on a rest, having a support roller with a length of at least two steps of the screw being machined, while the axis of rotation of the roller units, blanks, deforming springs and copier are parallel, and the center distance A _m between the blank and the copier is determined by the formula

And _m = D _З + D _CR - 2h, mm,

where A _m is the center distance between the workpiece and the copier, mm;

D _З - screw blank diameter, mm;

D _CR - the outer diameter of the deforming spring, mm;

h is the preload required for surface plastic deformation during rolling in, mm.

Features of the proposed method are illustrated by drawings.

Figure 1 shows the processing scheme of the proposed method and a device for running the screws of screw pumps, top view; figure 2 is a transverse section along aa in figure 1, rotated; figure 3 is a transverse section along BB in figure 1, rotated; figure 4 is a longitudinal section along bb in figure 1; figure 5 is a longitudinal section along BB in figure 1, a variant of the deforming spring with tightly wound coils; Fig.6 is a diagram of the processing and the forces acting on the workpiece during rolling, a cross-section along G-G in Fig.1.

The proposed method is intended for processing by surface plastic deformation of the outer surfaces of rotation of workpieces such as shafts and screws with a large pitch, for example, screws of screw pumps, as well as eccentric shafts and other complex parts.

The processing is performed on turning, rotary machines with the message of the rotational movement of the workpiece - V ₃ and the movement of the longitudinal feed -S _pr rolling device.

A rolling device that implements the proposed method comprises a housing 1 in the form of a base on which working deforming elements are installed, made in the form of turns 2 of a coil spring 3.

The spring 3 is mounted on an elastic base 4 made, for example, of rubber by vulcanization together with the axis 5. The axis 5 rotates freely in the bearings 6 of the housing 1.

The housing 1 with the spring 3 is installed so that the spring 3 is located between the workpiece 7 of the screw and the copier 8, and their axis of rotation is parallel. The copier 8 has the shape of the screw 7 being machined and is shifted in the longitudinal direction relative to the screw blank 7 by a value of t / 2 equal to half the pitch t of the screw 7, so that, for example, the depression of the screw blank 8 is against the protrusion of the copier 8. The copier 8 has a forced rotation from the spindle 9, in the chuck 10 of which the workpiece 7 is fixed. The forced rotation of the copier 8 is provided, for example, by gearing of the wheels 11, 12 and 13. The gear 11 is mounted on the spindle 9, is the leading one and transfers to the intermediate gear 13 the sweeping movement of the driven gear wheel 12, which is mounted on the spindle 14, where the copier 8 is mounted using the chuck 15. Since the gears 11 and 12 have an equal number of teeth, the speed of rotation of the copier 8 is equal to the speed of rotation of the workpiece 7, and thanks to the intermediate gear 13 the copier 8 has the same direction of rotation with the workpiece 7.

In a diametrically opposite place relative to the copier 8, the workpiece 7 rests on a rest 16, which has a support roller 17 with a length of at least two steps (2t) of the machined screw 7. The axis of rotation of the roll 17 of the rest 16, workpiece 7, deforming spring 3, and copier 8 are parallel.

A center distance _m between the workpiece and the copier for a particular workpiece is a fixed value and is determined in accordance with Figure 2 as the sum of the radii of the workpiece (D _W / 2) and the tracer (D _k / 2) plus the cross-sectional outer diameter (D _ave) deforming springs minus double preload (2h), which is necessary for surface plastic deformation during processing by rolling. But since the dimensions of the copier are equal to the dimensions of the workpiece of the screw, the center distance A _m between the workpiece and the copier is

And _m = D _З + D _CR - 2h, mm,

where A _m is the center distance between the workpiece and the copier, mm;

D _З - screw blank diameter, mm;

D _CR - the outer diameter of the spring, mm;

h is the preload required for surface plastic deformation and installed during rolling in, mm.

The proposed method is carried out using this device, which is installed and secured, for example, on a modernized lathe. Modernization consists in establishing:

on a support - the case with a deforming spring and a lunette;

on the headstock - an additional spindle and cartridge for the copier and its drive;

on the tailstock - an additional support center.

Before processing, the workpiece 7 is installed and secured in the cartridge 10 and is tightened by the rear center 18. The main rotational movement of the workpiece V _{3 is turned on} and then the slow transverse feed S _pop (upward, according to FIG. 2) of the case with a deforming spring. The transverse supply of S _{pop is} carried out until the longitudinal axis of the deforming spring is in the same horizontal plane with the axes of the workpiece and the copier.

Since the center distance A _{m is} fixed, and the gap between the workpiece and the copier is smaller than the outer diameter of the spring, the coil of the spring is deformed, turning from cylindrical to elliptical, and there are large static loads P _article necessary for rolling in and acting on the surface to be machined from the side deforming turns of the spring (see Fig.6).

Processing rolling over the entire length of the screw is provided by the inclusion of a longitudinal feed S _pr deforming spring along the workpiece. The number of longitudinal strokes of the deforming spring along the workpiece depends on the requirements:

- to the roughness of the treated surface;

- to the value of the hardened layer and the degree of hardening,

as well as from the workpiece material and other technological requirements.

Since the deforming spring 3 unilaterally affects the workpiece, the rest 16, moving along with the deforming spring in the longitudinal direction, eliminates the one-sided impact of the deforming tool and the axis deflection when rolling in non-rigid workpieces with high static loads - P _article , with which traditional rolling tools work .

The necessary static load - P _article , providing surface plastic deformation, is created by the device design, namely by setting the center distance A _m between the copier and the workpiece, which is controlled by a change in the interference h.

Before processing a batch of billets, the device is tuned to the necessary static load - P _st , which provides surface plastic deformation by approaching or removing the copier from the workpiece being processed, and there is a need to replace the intermediate gear 13 with a wheel with a correspondingly reduced or increased number of teeth.

In the process of turning on the rotational movement of the workpiece V _З , introducing a deforming spring onto the line of the centers of the copier and the workpiece and longitudinal feed S _{pr, the} elastic deforming elements 2 of the spring 3 carry out surface plastic deformation.

Having elasticity, the deforming elements of the coils 2 of the spring 3 with the help of a copier provide a more elastic clamp to the machined complex shaped surface, thereby achieving more uniform hardening of the surface layer of the workpiece.

The presence of an elastic element, which is a deforming spring 3, provides a constant hardening force at any point on the machined complex shaped surface.

The proposed method makes it possible to most fully use the working surface of the deforming elements and thereby significantly increase the durability of the tool.

The elastic elements of the tool, i.e. the spring is made of steel: alloyed ShKh15, KhVG, 9Kh, 5KhNM, carbon tool U10A, U12A. Hardness of the working surface of coils made of HRC 62 ... 65 steel. The working surface of the deforming coils 2 of the spring 3 is polished to Ra = 0.08 ... 0.16 μm.

The spring 3 can be wound tightly with a pitch equal to the diameter of the wire from which the spring is made (see Fig. 5), as well as with a large pitch, allowing better penetration of the lubricating-cooling fluid into the contact zone (see Fig. 4).

The performance of the proposed process of hardening processing is determined by the diameter of the wire from which the spring is made, and the diameter of the turns of the spring. When processing screw blanks, the diameter of the wire is dictated by the dimensions of the depression of the screw surface, namely, the diameter of the spring wire must be such that it contacts all points of the bottom of the depression in the longitudinal section of the screw.

A device with a large wire diameter allows processing with a large longitudinal feed S _ol , however, in this case, it is necessary to create large working forces P _st , which reduces the surface quality. The parameters of the deforming spring depend on the value of the permissible working force P _st .

It is most expedient to process the initial surfaces of 7 ... 11th qualifications by rolling.

When rolling by the proposed method, roughness parameters Ra = 0.2 ... 0.8 μm are practically achieved with the initial values of these parameters 0.8 ... 6.3 μm. The degree of reduction in surface roughness depends on the material, working force or interference, feed, initial roughness, device design, etc.

Running in the proposed method should be carried out so that the desired results are achieved in one pass. Do not use the reverse stroke as a working stroke, as repeated passes in opposite directions can lead to excessive deformation and peeling of the surface layer.

The workpiece speed V _З does not have a noticeable effect on the results of processing by rolling and is selected taking into account performance requirements, design features of the workpiece and equipment. Typically, the speed V _Z is 30 ... 50 m / min. The value of the rolling force is selected depending on the purpose of the treatment. The optimal force P _article (N) corresponding to the maximum endurance limit is determined by the formula P _article = 500 + 1.66 D ² , where D is the diameter of the workpiece’s surface to be rolled in, mm.

The proposed method, implemented by a device with a multi-element deforming spring tool, provides a constant contact force of deforming elements with the treated surface and almost does not reduce the error of the previous processing, being a copy.

Sulfofresol (5% emulsion) serves as a lubricant-cooling fluid during the run-in. Cast iron processing is recommended without cooling.

Example. The left screw H41.1016.01.001 of the screw pump EVN5-25-1500 (see figure 1) was processed, which had the following dimensions: total length - 1282 mm, length of the screw part - 1208 mm, cross-section diameter of the screw D _З = ⌀27 ^-0.05 mm, eccentricities - 1.65 mm, 3.3 mm, pitch t = 28 ^{± 0.01} mm, roughness R _a = 0.4 μm; single-helical screw surface, left direction; material - steel 18HGT GOST 4543-74, hardness HB 207-228, weight - 5.8 kg. Processing was carried out on a mod screw-cutting machine. 16K20 using a rolling device with a deforming spring. The spring was made with the outer diameter of the coils in a free unloaded state D _CR = 30 mm, from a wire with a diameter of 5 mm. The working surface of the deforming turns of the spring was polished to R _a = 0.08 ... 0.16 μm.

Cutting fluid - sulfofresol. The peripheral speed of the workpiece - V _З = 21 m / min (0.35 m / s), n _З = 250 rpm, longitudinal feed S _CR ⁼ 0.25 mm / rev, the required roughness and accuracy of the screw surface was achieved through T _m = 2.5 min (against T _m ^bases = 36.5 min according to the base case with traditional ball rolling around on a 1K62 lathe at Livhydromash OJSC). As a result of plastic deformation of microroughnesses and the surface layer, the surface roughness parameter increased to R _a = 0.4 μm with the initial value of R _a = 3.2 μm. The surface hardness increased by 50 ... 80% with a riveted layer depth of 0.3 ... 3 mm. The residual compressive stresses reached 400 ... 800 MPa on the surface. The control was carried out by an indicator bracket with an indicator ICh 10 B cells. 1 GOST 577-68. The cumulative error between any non-adjacent steps was not more than 0.1 mm, the clearance when controlling the straightedge of the protrusions forming in diameter was not more than 0.07 mm, which is permissible according to the technical specifications.

The proposed method extends the technological capabilities of the surface plastic deformation process, increases the roughness parameter of the treated surface, increases its hardness to a considerable depth, increases productivity by increasing the contact spot of a large number of deforming elements with the surface being treated, and also reduces the cost of the processing process.

Information sources

1. German patent No. 665083, cl. 67 p. 1, 1940.

2. Nikiforov A.V., Sakharov V.V. Technological capabilities and prospects of finishing and hardening with an elastic tool (Mashinostroit. Pr-in. Ser. Progressive technological processes in engineering: Obzor. Inform. / VNIITEMR. Issue 5) .- M, 1991. - P.31 ... 37, prototype.

Claims (1)

A method of rolling in screws, comprising communicating rotational motion to a screw preform and longitudinal feeding to a device comprising a housing and working deforming elements made in the form of coils of a coil spring, characterized in that before turning on the longitudinal feed, the spring with deforming coils informs the transverse feed and is brought into contact with the workpiece and the copier, the said spring, which is mounted freely on an elastic basis on an axis in the bearings of the housing, reports rotation from the workpiece, while the copier has t is the shape of the screw being machined and is shifted in the longitudinal direction by half the pitch of the screw so that the cavity of the screw blank is opposite the protrusion of the copier, and the copier is forced to rotate from the workpiece at a speed equal to the speed of the workpiece and the same direction with it, and in a diametrically opposite place relative to the copier, the workpiece rests on a rest, having a support roller with a length of at least two steps of the machined screw, while the axis of rotation of the roll of the rest, workpiece, spring and copier are parallel, and the center the total distance A _m between the workpiece and the copier is determined by the formula
A _m = D _s + D _ol - 2h, mm,
where A _m is the center distance between the workpiece and the copier, mm;
D _s - diameter of the workpiece of the screw, mm;
D _CR - the outer diameter of the spring, mm;
h is the interference fit for surface plastic deformation during rolling in, mm.

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