RU208324U1 - Support knife - Google Patents

Abstract

The utility model relates to mechanical engineering, in particular, to equipping centerless grinding machines with modernized support knives with a combined shape of the working surface, and can be used for centerless grinding of roller bearing rollers and balls, in particular, hollow ones. Within the working area, the working surface of the support knife consists of two sections: the first section has a helical shape and a bevel at an initial angle α to the plane in which the axes of the grinding and driving wheels are located, the length of the knife support surface in this section is equal to the length from the beginning of the working area to a distance of 0.75 of its length; the second section has a length of 0.25 of the length of the working area and does not have a slope; within its limits, the supporting surface is flat and parallel to the plane in which the axes of the driving and grinding wheels are located, which makes it possible to eliminate the operating size error resulting from continuous cutting of the base surface when it is centerless grinding and displacement of the workpiece in the direction of the driving circle.

Description

The utility model relates to mechanical engineering, in particular, to equipping centerless grinding machines, and can be used for centerless grinding of cylindrical parts, for example, roller bearing rollers, as well as balls, in particular, hollow ones.

Currently, for processing balls in serial production, universal centerless grinding machines are used, the working area of which contains a grinding wheel 1 and a leading abrasive wheel 2 between which the workpiece 3 is located on the support knife 5 (Fig. 1).

So, for example, in the method of centerless grinding of balls per passage [1], the balls are placed in a technological device on a beveled support knife and moved along it by means of a helical groove of the driving wheel.

Known support knife [2] (prototype), having a working surface in the form of a plane inclined at an angle to the plane of the axes of the driving and grinding wheels.

A common disadvantage of all known designs of supporting knives, including the prototype, is that their working surface is made in the form of a plane parallel to the axis of the leading abrasive wheel and inclined at a constant angle to the plane of the axes of the driving and grinding wheels. In most sources of technical information, without any calculation justification, it is recommended to take this angle equal to 20 °.

(фиг. 2). Фактически выполняемым размером будет не диаметр сферы, а именно величина этой хорды. Величина погрешности ξ может быть определена следующим образом:In this case, as a result of grinding part 3 with its movement along the surface of the support knife 5 due to the removal of the allowance Z, an error ξ arises in the diameter due to the continuous displacement of the measuring base of the adjustment size in the form of a chord KK ₁ , connecting the points of contact of the workpiece with the driving wheel 2 and the grinding circle 1. At the end of processing, this chord takes the position

(Fig. 2). The actual size will not be the diameter of the sphere, but the size of this chord. The magnitude of the error ξ can be determined as follows:

where D ₃ and d are the diameter of the original ball blank and the diameter of the ball after processing, respectively;

D _B - the diameter of the driving circle;

D _W - the diameter of the grinding wheel;

h - the value of the excess of the center O of the ball after processing over the plane in which the axis of the leading O _B and the axis of the grinding O _{W of the} wheels are located at the initial moment of processing;

h ₁ - the value of the excess of the center О _{1 of the} ball after processing over the plane in which the axis of the driving О _В and the axis of the grinding О _Ш1 wheels are located after the end of processing:

where α is the bevel angle of the support knife.

FIG. 2 also shows:

D _W - the diameter of the grinding wheel 1;

S _BP - cutting feed of the driving wheel 2;

ω _W - the peripheral speed of the grinding wheel 1;

ω _B - the peripheral speed of the driving circle 2;

N is the point of contact of the workpiece 3 with the support knife 5;

N ₁ is the point of contact of the ball after processing 4 with the support knife 5.

In the initial period of grinding, which is roughing, this error is not critical, and the presence of a wedge-shaped space with an angle of less than 90 °, in which the part moves, provides it with greater stability and the possibility of high-performance removal of the main allowance value. During processing, the specified error increases and at the final stage (when the part leaves the working area) it becomes unacceptable in magnitude.

The proposed technical solution to this problem arises from the disadvantages of the prototype and consists in the need to increase the accuracy of the size of the processed surface of rotation by eliminating the error of the adjustment size.

The problem is solved as follows (Fig. 3, Fig. 4).

The working surface of the knife is made up of two sections. The first section is made in the form of a helical surface with a rectilinear generatrix. At the beginning of the first section of processing, corresponding to the placement of the part at the beginning of processing, the working surface of the knife has the required initial angle α of inclination to the plane of the axes of the driving and grinding wheels, for example, α = 20 °, and at the end of this section at a distance of 0.75 * L ( Fig. 4) from the end of the support knife corresponding to the placement of the part at the beginning of processing, where L is the length of the working surface of the support knife, the angle of inclination is zero. In this section, the main machining allowance is removed and the operational size error is gradually corrected (1). The second section of the working surface of the knife is mated with the first, it is made flat without inclination to the plane of the axes of the driving and grinding wheels parallel to their axes. In this area, the nursing process takes place with the stabilization of the operating size. The length of this section is 0.25 * L (Fig. 3). The 3D model of the proposed design of the support knife is shown in Fig. 3. A sketch of the proposed design of the support knife is shown in Fig. 4.

Thus, the problem of increasing the accuracy of the size of the machined surface during centerless grinding is solved by a rational change in the design of the support knife.

A significant difference between the proposed device and the prototype is that the working surface of the support knife is combined, consisting of two sections:

- the first section, intended for placing the part at the beginning of processing and removing the main stock, has a helical shape and a bevel at an initial angle α to the plane in which the axes of the grinding and driving wheels are located. The length of the working surface of the knife in this area is equal to the distance from the beginning of the working zone to 0.75 of its length. Throughout this section, the bevel angle decreases continuously from the value of α to zero;

- the second section, which allows you to constantly reach a constant value of the adjustment size, has a value of 0.25 of the length of the working zone and does not have a slope. Within its limits, the working surface is flat and parallel to the plane in which the axes of the driving and grinding wheels are located, therefore, the error determined by relationship (1) is zero.

Literature

1.A.S. USSR No. 1537480 class. В24В 11/02, 1989, Method for centerless grinding of balls. Vasin A.N., Gundorin V.D., Novikov V.I. Publ. 01.23.1990. Bul. No. 3.

2. Patent RU 2351453 C2. Centerless grinding method and abrasive tools used therein.

Claims (1)

A support knife for centerless grinding of parts such as a body of revolution, containing a working surface, characterized in that said working surface consists of two sections, while the first section is intended for placing the workpieces at the beginning of processing and removing the main allowance and is made in the form of a helical surface with a rectilinear generating and smoothly changing bevel, and the second section is conjugated with the first section, is made flat without inclination to the plane of the axes of the grinding and driving wheels and is located parallel to it, and the bevel in the first section is made from a given initial angle of inclination α to the specified plane at the beginning of the section to zero at the end of the section, while the length of the first section of the working surface is 0.75L, and the length of the second section is 0.25L, where L is the length of the working surface of the supporting knife.

Images