RU2351456C1 - Superfinishing method of screws - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to abrasive machining field and can be used at finishing treatment by means of superfinishing of screw blanks and other details such as shafts made of steels and alloys. Treatment is implemented by means of facility, containing body, frames and holders with diamond-abrasive bars. Blank is imposed rotation. Facility is imposed - oscillating to-and-fro movement, traverse of diamond-abrasive bars, bars loading to blank with constant force and minimal pressure in workpiece range. Mentioned facility is used with body, allowing box shape. Inside the body in grooves there are located frames, bearing in its slots with ability of plate radial motion with rigidly fixed axis. On the last there are installed springs, providing frame pressure on plates. Plates allows pins, on which there are movable by means of grooves are installed holders with ability of alternate cross motion, which is perpendicular to plates radial displacement. On the body in brackets it is mounted shaft with jaws and handle for frames lead with bars from treatment area.

EFFECT: it is improved productivity of process ensured by increasing of contact markings, there are improved roughness parameters of treated surface, process cheapen.

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Description

The invention relates to mechanical engineering technology, in particular to finishing diamond abrasive processing by superfinishing screw blanks and other parts such as shafts of steel and alloys with multi-element diamond abrasive tools.

A known method of superfinishing using a holder consisting of a frame and a pivotally mounted housing with diamond-abrasive bars, allowing self-installation of bars on the workpiece’s work surface by swinging the housing relative to the transverse axis, while the swing is limited by the adjusting nut [1].

The disadvantages of this method are the low productivity in relation to diamond-abrasive superfinishing of screws and other parts such as shafts of large length due to the small contact patch of diamond-abrasive-containing elements with the treated surface, as well as low processing quality.

The objective of the invention is the expansion of technological capabilities, which consists in improving the roughness parameter of the processed surface due to the actions of a large number of diamond-abrasive elements, in increasing productivity by increasing the contact spot of these elements with the treated surface 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, as well as in failure e from expensive special equipment and the ability to process complex shaped bodies of revolution on universal equipment.

The problem is solved by the proposed method of superfinishing screws, including a message to the rotation of the workpiece, and a device containing a body, frames and holders with diamond abrasive bars, oscillating (oscillating) movement, longitudinal feeds of diamond abrasive bars, constant pressure of the bars against the workpiece and low pressure in the processing zone, characterized in that the casing has a box-like shape, inside of which in the grooves there are frames bearing in their grooves with the possibility of radial movement of the plate with with fixed axes, on which springs are installed, which allow applying pressure of the frame to the plates, in addition, the plates contain pins on which holders are mounted movably with the help of grooves with the possibility of reciprocating transverse movement perpendicular to the radial movement of the plate, while on the case in brackets mounted shaft with cams and a handle necessary for the withdrawal of frames with bars from the treatment area.

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

Figure 1 shows a diagram of the proposed process of superfinishing the outer screw surface of the screw pump screw on a lathe and a device that implements the proposed method; figure 2 is a cross section aa in fig. one; in Fig.3 - view B in Fig. one; figure 4 is a section bb in figure 2; figure 5 - element G in figure 1.

The proposed method is used for diamond-abrasive machining by superfinishing the external surfaces of rotation of workpieces such as shafts and screws with a large pitch, for example, screw pumps, screw shafts, and also eccentric shafts and other complex parts.

The processing is performed on turning, rotary machines with a message about the rotational movement of the workpiece - V _s , and for the device with the tool - the movement of the longitudinal feed S _ol , oscillatory (oscillating) movement S _о with constant pressure of the bars against the workpiece and low pressure P _min in the processing zone.

The proposed method of superfinishing processing is implemented by a device that contains diamond-abrasive bars 1, acting on the screw blank 2, a box 3 having a box-shaped inside of which a frame 4 is located in the grooves. Brackets 5 that form the grooves are rigidly fixed in the frame 4, in which freely located with the possibility of radial movement are plates 6. On the shelves of the plates 6 are fixed axes 7 on which cylindrical compression coil springs are installed 8. The springs 8 exert a constant working pressure P _min per instrument. In addition, pins 9 are mounted on the plates 6, on which the holders 10 with diamond abrasive bars 1 are mounted. In the holders 10, grooves 11 are made for receiving the pins 9 in them and due to which the bars 1 have the possibility of reciprocating transverse movement perpendicular to the radial the movement of the plate 6. Thus, having the ability to move in the transverse plane in two mutually perpendicular directions, the bars are easily self-mounted on the machined screw surface.

For more intensive processing, the device is equipped with a large number of bars, and the width B _{B of the} bars is selected as maximum and is in the range D _З > B _B > О _З / 2, where D _З - diameter of the workpiece; and the thickness h of the bars is assumed to be minimal. The working surface of the new bars in the transverse plane is filled according to the shape of the workpiece in the transverse plane, and the configuration of the working surface and the radius R (see Fig. 5) of the bars in the longitudinal plane is formed by self-sharpening and depends on the configuration of the cavity of the screw blank in the longitudinal section. As the bars wear out, the cutting properties and the configuration of the working surface are ensured by self-sharpening.

To enter the bars into the treatment zone and withdraw them after processing on the casing 3, a shaft 13 with cams 14 and a handle 15 is mounted in the brackets 12. When the handle 15 is turned clockwise, as shown in FIG. 2, the cam 14 enters the groove 16, made in frame 4, and lifts the latter, removing the bars from the treatment area.

The proposed method can be carried out, for example, on a lathe, while the device that implements the method is mounted on a support on brackets (not shown) so that the bars are above the workpiece. The workpiece, for example screw 2, is fixed in the cartridge 17 of the spindle 18 of the headstock 19 and is pressed by the center 20 of the tailstock 21.

After the workpiece of the screw 2 is fixed in the cartridge 17, it is pressed by the rear center 20 and include the main movement - rotation V _Z. Next, a super-finishing device is brought into contact with the workpiece and diamond-abrasive bars are pressed with the required force P _min .

The device is given a longitudinal feed motion S _ol and an oscillatory (oscillating) motion — S _о . Processing is carried out with a constant force of pressure of the bars to the workpiece and low pressure P _min in the processing zone.

In the process of turning on the longitudinal feed S _ol and the oscillatory motion S _{on the} diamond-abrasive bars with their working surfaces come into contact with the workpiece and carry out grinding. Processing occurs without a significant change in the size and macrogeometry of the surface. As the tops of the scallops are removed, the contact surface increases, the pressure of the bars decreases, the chips fill the pores of the bars, the cutting ability of the bars decreases, the processing stops.

In the initial period of processing the next workpiece, diamond-abrasive bars, in contact with a rough surface, self-sharpen and restore cutting properties.

Superfinishing by the proposed method reduces the surface roughness to Ra = 0.012 ... 0.1 μm, increases the supporting surface from 20 ... 30 to 80 ... 90%, removes the defective surface layer.

The allowance on the side by 10 ... 20% should exceed the height of the surface roughness so that there are no traces of the previous treatment after superfinishing. When machining parts from cast iron, non-ferrous metals and non-hardened steel, a tool made of silicon carbide is used; electrocorundum bars are used for superfinishing parts of hardened steels.

The speed of the oscillatory motion S _{о is} limited by the arising inertial forces during reversal and usually does not exceed 5 ... 7 m / min with an oscillation amplitude of up to 6 mm; K = V _W / S _about . With a decrease in K, the cutting ability of the bars is more fully restored and the metal removal rate increases, but the surface roughness parameter increases. Therefore, it is advisable to conduct processing with a variable value of K, which is governed by a change in the speed of rotational motion: at the beginning of the cycle, V ₃ = (2 ... 4) S ₀ , and at the end of the cycle V ₃ = (8 ... 16) S ₀ . For soft materials and rough surfaces, the K value is greater, for hard materials - less.

The pressure of the bars on the treated surface determines the intensity of the process. Superfinishing uses low pressures. Finishing is performed at a minimum pressure: 0.1 ... 0.3 MPa for parts made of steel, 0.1 ... 0.2 MPa for parts made of cast iron, 0.05 ... 0.1 MPa for parts made of non-ferrous metals.

The composition of the working fluid affects the quality of the treated surfaces. With increasing viscosity of the working mixture, the cutting action of the bars decreases and blunting occurs faster. The best working fluid should be considered a mixture of kerosene (80 ... 90%) with spindle or turbine oil (10 ... 20%).

Example. The screw left 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, screw cross-section diameter ⌀27 ^-0.05 mm , eccentricity e ₁ = l, 65 mm, e = 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. The roughness obtained in the previous operation R _a = 1.6 μm. The allowance on the side is 10 ... 20 microns. Processing was carried out on a mod screw-cutting machine. 16K20 using the developed device for superfinishing screws with bars having the characteristic: grain material 63 C, grain size 8 ... 6, hardness C2 ... CT2. The device was fixed on the support of the machine. Cutting fluid - a mixture of kerosene (80 ... 90%) with turbine oil (10 ... 20%).

The peripheral speed of the workpiece at the beginning of the cycle is V _З = 10.6 m / min (0.176 m / s), n _З = 125 rpm and at the end of the cycle - V _З = 106 m / min (1.76 m / s) , n _З = 1250 rpm, the speed of the oscillatory motion S _o = 5 m / min. Processing was performed at a minimum pressure P _min 0.1 ... 0.3 MPa; the required roughness and accuracy of the helical surface was achieved after T _m = 5.8 min (against T _m ^bases = 46.5 min according to the basic version with traditional grinding using a grinding head, followed by polishing with a diamond strip on a 1K62 lathe at Livhydromash JSC "). 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 process of diamond abrasive processing, increases the roughness parameter of the processed surface, increases productivity by increasing the number of diamond abrasive elements, and also reduces the cost of the process and reduces the cost of manufacturing tooling.

Sources of information taken into account

1. Reference technologist-machine builder. In 2 vols. T.1 / Ed. A.G. Kosilova and R.K. Meshcheryakova. - 4th ed., Revised. and add. - M.: Mechanical Engineering, 1986. P.437 ... 440, Fig. 292 - prototype.

Claims (1)

A method for superfinishing screws, including communicating rotation to the workpiece, and to a device comprising a body, frames and holders with diamond abrasive bars, oscillating oscillating motion, longitudinal feeds of diamond abrasive bars, pressing them against the workpiece with constant force and minimum pressure in the processing zone, characterized in that they use the aforementioned device with a box-shaped body, inside of which are placed in the grooves of the frame, bearing in their grooves with the possibility of radial movement of the plate with heated axes, on which springs are installed, which provide pressure of the frame to the plates, the plates have pins, on which the holders are mounted movably with the help of grooves with the possibility of reciprocating transverse movement perpendicular to the radial movement of the plate, while a shaft with cams is mounted on the case and a handle for removing frames with bars from the treatment area.

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