RU213598U1 - 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 balls, in particular hollow ones. Within the working area, the working surface of the supporting knife has a slope, the value of which is determined by the above dependence. EFFECT: increased accuracy of processing due to the elimination of the error in the operational size, which occurs due to the continuous cutting of the base surface during its centerless grinding. 5 ill.

Description

The utility model relates to mechanical engineering, in particular to equipping centerless grinding machines, and can be used for centerless grinding of balls, in particular, hollow ones.

Currently, for the processing of balls in mass 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 a workpiece 3 is located on a support knife 5 (Fig. 1).

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

Known reference knife 5 [2] (prototype), made of ceramics and having a working surface in the form of a plane parallel to the axis of the leading abrasive wheel 2. The workpiece 3 is located between the grinding wheel 1 and the leading abrasive wheel 2 and rests on the plane of the reference knife 5 (Fig. .2).

A common disadvantage of all known designs of support knives, including the prototype, is that their working surface is in the form of a plane parallel to the axis of the leading abrasive wheel 2 and has no kinks within the working area.

(фиг. 3). 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 the workpiece 3 with its movement along the surface of the support knife 5 due to the removal of the allowance on the Z side, an error occurs<f in 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 circle 2 and grinding wheel 1. At the end of processing, this chord takes the position

(Fig. 3). In fact, the size performed will not be the diameter of the sphere, but the value of this chord. The error value ξ can be determined as follows:

where D _З and d - the diameter of the workpiece and the diameter of the ball after processing, respectively;

D _B - diameter of the leading circle;

D _W - diameter of the grinding wheel;

h - the value of the excess of the center O of the ball after processing above the plane in which the axis of the leading O _B and the axis of the grinding O _W wheels are located at the initial moment of processing;

h ₁ - the value of the excess of the center O, the ball after processing above the plane in which the axis of the leading OB and the axis of the grinding O _Sh1 circles are located after the end of processing:

,

,

where α is the bevel angle of the support knife.

In FIG. 3 also shown

D _W - diameter of the grinding wheel 1;

S _BP - plunging feed of the driving circle 2;

ω _W - angular speed of the grinding wheel 1;

ω _In - the angular velocity of the leading circle 2;

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

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

The technical problem of the proposed technical solution stems from the shortcomings of the prototype and is the need to improve the accuracy of the size of the processed spherical surface.

The problem posed is solved in the following way.

The specified error ξ can be prevented by using a support knife with a modernized shape of the support surface. The modernized design of the support knife (Fig. 4) should provide for the possibility of ensuring the optimal position of the center of the cross-section of the workpiece as the allowance is removed at a level that maintains the achieved value of the adjusting size. To do this, its supporting surface should not be straight, but combined, i.e. consist of several sections.

The proposed device is illustrated by illustrations (Fig. 4, Fig. 5)

Section I is designed to place the workpiece before starting processing. Its surface is parallel to the axes of the driving and grinding wheels.

Section II is made with a certain slope. The value of the slope Δ allows, when moving the workpiece along the surface of the knife in the process of removing the allowance, to constantly reach the position of the center of the sphere, which ensures a constant position of the chord, the size of which is the adjusting one.

Section III is intended for the final formation of the size of the sphere in the process of nursing. This section has a surface parallel to the axes of the driving and grinding wheels.

In FIG. 4 also shows the angle α - the angle of the bevel of the supporting knife; B is the length of the working surface of the grinding wheel, i.e. the size of the working area.

Let us show by calculation the method for determining the rational value of the blade slope in section II, which ensures the absence of an error in the adjusting size (Fig. 5).

- расстояние между точкой контакта шарика после обработки 4 с ведущим кругом 2 и шлифовальным кругом 1 и вертикальной осью поперечного сечения шарика после обработки в конечный момент обработки; α - угол скоса опорного ножа.In FIG. 5 shows 1 - a grinding wheel, the axis of which lies in the same plane with the axis of the driving wheel 2 at some angle to it; 3 - blank; 4 - ball after processing; 5 - support knife with a combined support surface having a section with a slope Δ, providing a rational position of the center of the workpiece in the process of removing the allowance on the Z side; D _З and d - the diameter of the workpiece and the diameter of the ball after processing, respectively; D _W - diameter of the grinding wheel 1; D _B - diameter of the leading circle 2; ω _W - angular speed of the grinding wheel 1; ω _In - the angular velocity of the leading circle 2; h - the value of the excess of the center O of the ball after processing above the plane in which the axis of the leading O _B and the axis of the grinding O _W wheels are located; About _B1 - the position of the axis of the leading circle at the final moment of processing; About _W - the position of the axis of the grinding wheel at the final moment of processing; K ₂ -K ₁ - the distance between the point of contact of the workpiece with the driving wheel 2 and the grinding wheel 1 and the vertical axis of the cross-section of the workpiece at the start of processing;

- the distance between the point of contact of the ball after processing 4 with the driving circle 2 and grinding wheel 1 and the vertical axis of the cross-section of the ball after processing at the final moment of processing; α - bevel angle of the support knife.

From the geometric diagram in Fig. 5 we have

adjusting size error:

.

.

Example 1: let D _B =300mm; D _Z \u003d 26.4 mm; d=25.4 mm; h=10 mm; α=30°. Then the calculation according to formula (3) gives the value of the error of the adjustment size ξ=0.00354 mm.

или OK=OK'. При выполнении этого условия получим, чтоIn order to fulfill the condition ξ=0, it is necessary to achieve the relation:

or OK=OK'. If this condition is met, we get that

.

.

Calculation by formula (4) gives the result: h1=9.971754 mm.

That is, to maintain the correct value of the setting size, it is necessary not to maintain a constant value of h, but to reduce the excess value from h to h ¹ in accordance with (4).

When using the support knife of the described design, the error of the adjustment size during centerless grinding of the sphere is significantly reduced, almost by an order of magnitude, and occurs only due to the presence of a tolerance on the size of the workpiece. Its value in this case can be determined using (4), but the value of h will then change and take on the value

,

,

where T is the tolerance on the diameter of the spherical workpiece.

Example 2: for the conditions given in the previous examples and T=0.1 mm, the calculation according to formulas (1) and (2) gives the result: ξ=0.051493 mm; calculation according to formulas (3) and (5) gives the result: ξ=0.0035 mm.

Thus, the problem of increasing the accuracy of the size of the machined surface during centerless grinding is solved by expediently changing the design of the support knife.

The essential difference between the proposed device and the prototype is that the working surface of the support knife is made up of three sections: the first section, designed to accommodate the workpiece before processing, is parallel to the axis of the leading circle, the second section, which allows you to constantly achieve a constant value of the adjustment size, within the working area has a slope, the third section, intended for nursing, is parallel to the axis of the leading circle.

In this case, the value of the slope on the second section of the working surface of the support knife is determined as follows

where Z - allowance on the side of the workpiece;

B is the length of the working surface of the grinding wheel, i.e. the size of the working area.

h - the value of the excess of the center O of the ball after processing above the plane in which the axis of the leading O _B and the axis of the grinding O _W wheels are located at the initial moment of processing;

h ₁ - the value of the excess of the center O1 of the ball after processing above the plane in which the axis of the leading O _B and the axis of the grinding O _W wheels are located after the end of processing.

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. Published 01/23/90. Bull. Number 3.

2. A.s. USSR No. 141072 class. 67a 24/01, 1961 Support knife for centerless grinding machine. Puzyrev E.I. Published 1961. Bull. No. 17.

Claims (1)

Support knife for centerless grinding of balls, having a flat working surface, characterized in that the working surface of the support knife is made up of three sections, the first section is made with the possibility of placing the ball blank before the start of processing, the second section is made with a slope, and the third one is made with the possibility of forming a sphere of the ball in the process of nursing.

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