RU2284258C1 - Sine diamond-abrasive cut-off wheel - Google Patents

Abstract

FIELD: abrasive working, possibly manufacture of high-speed diamond abrasive wheels used in ferrous metallurgy for cutting in abrasive-cutting off machine tools blanks of constructional, tool, corrosion resistant and fire resistant steels and alloys.

SUBSTANCE: wheel includes boss and sine disc with peripheral axially shifted cutting portion and with riffled ends. Disc is made according to condition providing formation of radial end recesses and dents arranged in staggered fashion on wheel ends. Amplitude of sine and riffle width are equal to height half of cutting part of disc. Riffles are formed only in recesses of sine disc along Archimedean helix. Plane of riffle protrusions is inclined by angle 1 - 2° in radial direction towards wheel center. Helixes of riffles are multi-start ones, they have even number of starts. Beginning of Archimedean helix of each end of wheel coincides with one of its generatrices. Formula is given in description of invention for determining quantity of end protrusions depending upon temperature drop.

EFFECT: improved design, lowered thermal stresses at cutting due to oscillations of cutting part of wheel, increased wear resistance, mechanical strength of wheel, improved efficiency of cutting without wheel camber.

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Description

The invention relates to mechanical engineering technology, to the manufacture of diamond-abrasive cutting tools, and can be used in the manufacture of high-speed cutting wheels used in ferrous metallurgy when cutting workpieces from structural, tool corrosion-resistant and heat-resistant steels and alloys on abrasive-cutting machines.

Known abrasive cutting wheel, on the end surface of which there are protrusions in the form of an isosceles triangle, alternating with depressions [1].

The disadvantages of the known tool are increased heat and rapid wear of the circles, especially on the tops of the protrusions, i.e. at the ends, while the low axial stiffness that these circles possess, leads to a decrease in their performance and a decrease in quality.

Known diamond-abrasive cutting wheel, which is mounted on the spindle at an acute angle α to a plane perpendicular to the axis of rotation, while the height of the wheel is less than the width of the cut groove, and the installation angle is determined by the formula

α = arctg [(H-B) / D],

where B and D are respectively the height and outer diameter of the circle, mm;

H - the width of the slotted groove, mm;

α is the angle of inclination of the circle to a plane perpendicular to the axis of rotation, deg [2].

In this case, the correction of its peripheral surface was made at a zero angle of installation of the circle on the spindle, and the installation and adjustment of the angle of inclination α - using oblique washers installed in pairs from the ends of the circle. In addition, wear of the end surfaces was compensated by increasing the angle of inclination α, and the shape of the edit of the peripheral surface depends on the axial stiffness, moreover, the editing of thick hard circles was made along the cylindrical generatrix of the peripheral surface, and thin circles with low axial stiffness of the circles formed V-shaped in a longitudinal section of the shape of the generatrix with a vertex in the plane of symmetry perpendicular to the axis of rotation of the circle lying on the maximum outer diameter.

The disadvantages of the known tool are reduced mechanical strength, low durability and rapid wear of the circles, especially at the ends, the complexity and complexity of dressing, which reduces the cutting performance and increases the cost of the process.

The objective of the invention is to increase the resistance, mechanical strength of the cutting wheels and cutting performance, reduce the risk of burns by reducing the heat stress of the cutting due to the oscillation of the cutting zone and the exclusion of deflection of the sinusoidal circle.

This is achieved by using a diamond-abrasive cutting wheel with an axially-displaced peripheral cutting part and corrugations located on its end surfaces, characterized in that it is made in the form of a hub and a sinusoidal disk from the condition of the formation of radial end cavities and protrusions located staggered at the ends of the circle, while the corrugations with a width of h = B / 2 equal to half the height of the cutting part of the circle are located only in the hollows along the spiral of Archimedes, and the plane of the corrugation protrusions is inclined under angle β = 1 ° ... 2 ° in the radial direction towards the center of the circle, while the corrugation spirals are multi-starting with an even number of entries, and the beginning of the Archimedean spiral at each end of the circle coincides with one of its generators, in addition, the amplitude And _{with a} sinusoid equal to half the height B / 2 of the cutting part of the disk of the circle, and the number of end protrusions n is determined depending on the degree of temperature decrease by the formula

n = π · D / P,

where D is the outer diameter of the circle, m;

P is the period of the sinusoid, m, determined by the formula

P = 2 (H / 2) _and ² · V · C / (10 · a),

H is the total height of the circle along the vertices of the sinusoid, equal to the width of the slot to be cut, m;

V _and - tool rotation speed, m / s;

a - thermal diffusivity of the workpiece material, m ² / s;

C is the sinusoidality coefficient, determined by the formula

C = (1-k _k ) / (k _A + k _B · V _rel ),

V _rel - the relative speed of movement of the workpiece, determined by the formula

v _rel = V _s · N / 2a,

V _s - rotation speed of the workpiece, m / s;

k _A is a coefficient depending on the degree of temperature decrease and takes values of 1.0; 1.0; 4.0; 5.0 with a decrease in temperature by 10%, 20%, 30% and 40%, respectively;

k _B is a coefficient depending on the degree of temperature decrease and assuming a value of 0.1; 0.32; 0.75; 1.7 with a decrease in temperature by 10%, 20%, 30% and 40%, respectively;

k _k is a coefficient depending on the relative speed and taking values of 0.18; 0.28; 0.53; 0.74 with a decrease in temperature by 10%, 20%, 30% and 40%, respectively.

The essence of the design of the circle is illustrated by drawings.

Figure 1 shows the scheme of cutting the workpiece and a General view of the diamond-abrasive cutting wheel having a hub, a sinusoidal disk with a peripheral axially offset cutting layer and corrugation in the hollows of the sinusoid, a partial longitudinal section; figure 2 is a cutting wheel, a view of the end surface on the left along A in figure 1; figure 3 is a General view of a cutting wheel, corrugations are conventionally shown in one cavity; figure 4 - scheme of cutting a round billet.

The proposed sinusoidal diamond-abrasive wheel has a sinusoidal disk 1 with a peripheral axially offset cutting layer from the condition of the formation of radial end depressions 2 and protrusions 3 located in a checkerboard pattern at the ends of the disk 1 and diverging fan from the center to the periphery. For reliable attachment of the circle, it has a hub 4.

Height In the sinusoidal part of the cutting disk 1 is less than the width H of the groove of the workpiece 5, this allows you to interrupt cutting in some cross sections, reducing the cutting temperature, and to exclude burns and microcracks on the machined surfaces.

In order to increase the axial stiffness of the cutting disk 1, it has at the ends of the working surface in the grooves of the corrugation 6, made according to Archimedean multi-helix. In Figs. 1-4, the corrugations 6 are conditionally highlighted with a thicker background, and the circle has two-way spirals, while Fig. 3 shows a general view of a detachable sinusoidal circle in which the corrugations are conventionally shown in one cavity.

The width h of the corrugations 6 is assigned based on the total stiffness of the circle and the possibility of its molding and is approximately equal to half the height B of the cutting disk 1, while to reduce the friction forces, the plane of the protrusions 7 of the corrugations 6 is inclined at an angle β = 1 ° ... 2 ° in the radial direction towards the center of the circle, and the corrugation spirals are multi-starting with an even number of approaches, and the beginning of the Archimedean spiral at each end of the circle coincides with one of its generators.

To cut semiconductor wafers, thin diamond wheels with a width of a fraction of a millimeter are used, cutting diamond wheels, the axial rigidity of which depends not only on the performance of the wheels themselves, but also on the quality, especially the accuracy, of the machined surface [3]. Such circles will be considered circles with low axial stiffness.

Due to the corrugations and sinusoidality, the proposed cutting wheels acquire a fairly high axial stiffness.

In the work of a diamond-abrasive cutting wheel with a sinusoidal peripheral cutting part of the disk 1, a parametric oscillation appears, characterized by the amplitude A _c , affecting the width H of the slot to be cut.

Due to the oscillation of the cutting zone, the height of the disk 1 is taken less than the width of the slot to be cut, which significantly affects the saving of expensive diamond-abrasive material.

The number of end protrusions n of the sinusoidal disk is determined depending on the degree of temperature decrease [4] according to the formula

n = π · D / P,

where D is the outer diameter of the circle, m;

P is the period of the sinusoid, m, determined by the formula

P = 2 (H / 2) _and ² · V · C / (10 · a),

H is the total height of the circle along the vertices of the sinusoid, equal to the width of the slot to be cut, m;

V _and - tool rotation speed, m / s;

a - thermal diffusivity of the workpiece material, m ² / s;

C is the sinusoidality coefficient, determined by the formula

C = (1-k _k ) / (k _A + k _B · V _rel ),

V _rel - the relative speed of movement of the workpiece, determined by the formula

V _rel = V _s · N / 2a,

V _s - rotation speed of the workpiece, m / s;

k _A is a coefficient depending on the degree of temperature decrease and takes values of 1.0; 1.0; 4.0; 5.0 with a decrease in temperature by 10%, 20%, 30% and 40%, respectively;

k _In - coefficient, depending on the degree of temperature decrease and taking values of 0.1; 0.32; 0.75; 1.7 with a decrease in temperature by 10%, 20%, 30% and 40%, respectively;

k _k is a coefficient depending on the relative speed and taking values of 0.18; 0.28; 0.53; 0.74 with a decrease in temperature by 10%, 20%, 30% and 40%, respectively.

The magnitude of the amplitude And _with equal to half the height In a sinusoidal disk.

The proposed circle has a hub 4, convenient for fastening it on the spindle, with ends perpendicular to the longitudinal axis, and disk 1 has a sinusoidal shape with a peripheral axially offset cutting layer and allows:

- reduce the grinding temperature in the contact zone by 30 ... 40%;

- Cut blanks in more forced modes without causing burns and microcracks. Due to this, processing productivity increases by 1.2 ... 1.3 times;

- maintain a good cutting ability of grains working in the self-sharpening mode for a long time, increase the general resistance of the circles by 2 ... 3 times;

- reduce rejects and achieve vibration resistance in the operations of cutting billets of steel and alloys predisposed to burns and cracks.

Example. To determine the advantages of the proposed design of the cutting wheel and the cutting method, a batch of cutting wheels of a new design with a diameter of 500 mm was manufactured using the power bakelization technology and comparative tests were carried out with serial wheels in the factory when cutting steel 12X2H4A with a diameter of 80 mm, the results of which are presented in the table.

Circle characteristic No. of a circle. Initial diameter mm Final diameter mm Number of cuts Cutting time, s K _sh ^* Abrasive cutting wheels according to GOST 2424-83, characteristics D500 × 5 × 51, 14 A 63 ST BU, 80 m / s one 500 312 22 21.1 1.06 2 500 298 25 21.6 1,11 3 500 303 24 20.6 1.10 four 500 300 25 21,2 1.19 The proposed abrasive cutting wheels, D500 14 A 63 ST BU, 80 m / s, the height of the sinusoidal disk B = 3 mm, the width of the grooves h = 2 mm, the width of the groove cut H = 5 mm, the spiral of the grooves is two-way 5 500 318 34 17.6 1,56 6 500 311 32 16.3 1.51 7 500 292 36 17.9 1.47 8 500 313 34 16.8 1.42 To _w ^* - the ratio of the rate of metal removal to the wear rate of the abrasive

The geometric parameters of the abrasive cutting wheel with a sinusoidal end surface for cutting are determined.

Grinding modes: circle rotation frequency - V _and = 80 m / s; workpiece rotation frequency - V _s = 0.5 m / s; cutting depth equal to the width of the slot to be cut t = 0.005 · 10 ^-3 m; the outer diameter of the tool is D _and = 0.5 m; disk height - B = 0.003 m; H = 0.005 mm; workpiece material - steel 12X2H4A with thermal diffusivity - a = 3 · 10 ^-6 m ² / s; the degree of temperature decrease - k _T = 30%.

We determine the relative speed of movement of the workpiece by the formula

V _rel = V _s · N / 2a = 0.5 · 0.005 / 2 · 3 · 10 ^-6 ≈416.7.

We determine the coefficient of sinusoidality by the formula

C = (1-k _k ) / (k _A + k _B · V _rel ) = (1-0.52) / (4 + 0.75 · 416/7) = 0.00151.

We determine the value of the period of the sinusoid according to the formula

P = 2 (N / 2) ² · v _and · C / (10 · a) = 2 (0.005 / 2) ² · 80 · 0.00151 / 10 · 3 · 10 ^-6 = 0.05 m.

From the data obtained, we determine the number of end protrusions on a circle with a sinusoidal periphery with a diameter of 500 mm

n = πD / P = 3.14 · 500 / 50≈31.4.

Round the number of end protrusions to n = 32 and determine the parameters of the diamond-abrasive wheel with a sinusoidal periphery

P = πD / n = 3.14 · 500/32 = 49 mm.

We determine the magnitude of the amplitude A _c = B / 2 = 1.5 mm, take A _c = 2 mm.

Example 2. According to example 1, determine the number of end protrusions to lower the temperature by 10%, 20% and 40%.

After calculating according to the above formulas, we determine the number of end protrusions for lowering the temperature by 10%, 20% and 40% for a circle with a diameter of 500 mm, respectively, n _10% = 2; n _20% = 9; n _40% = 130.

The new design of the wheel provides an increase in the grinding coefficient by an average of 45%, the resistance of the wheel by 45%, an increase in productivity by 30%.

The presence of radial grooves on the end surfaces of the wheel provides a decrease in the temperature of the workpiece due to less friction of the circle on the surface of the workpiece, and this, of course, reduces the risk of burning and grinding cracks on the cut surface.

Thus, the proposed diamond-abrasive detachable sinusoidal wheel with corrugations at the ends reduces the risk of burns by reducing the heat stress of the cutting due to the oscillation of the contact zone of the circle with the workpiece and intermittent cutting, has increased wear resistance due to the inclusion of the end parts of the wheel, increased axial stiffness and strength and provides increased cutting performance while reducing abrasive consumption.

Information sources

1. A.S. USSR No. 306011, MKI B 24 D 5/12. Abrasive cutting wheel. 1971 - an analogue.

2. RF patent 2235632, MKI B 24 D 5/12. Diamond-abrasive cutting wheel with parametric oscillation. Yu.S. Stepanov, B.I. Afanasyev and others. No. 2003129219, application. 09/30/2003, publ. 09/10/2004. Bull. No. 25 is a prototype.

3. Petasyuk G.A. The accuracy of cutting semiconductor wafers with diamond circles // STIN - 1998. - No. 3. - S.24-27.

4. Yakimov A.V. Abrasive-diamond processing of shaped surfaces. - M.: Mechanical Engineering, 1984. - S.118-124.

Claims (1)

Diamond-abrasive cutting wheel having an axially offset peripheral cutting part and located on its end surfaces of the corrugation, characterized in that it is made in the form of a hub and a sinusoidal disk with radial end cavities and protrusions located in a checkerboard pattern at the ends of the circle, the corrugations are made of width h, equal to half the height In the cutting part of the circle, and are located only in the hollows of the sinusoidal disk in a spiral of Archimedes, while the plane of the protrusions of the corrugations is inclined at an angle β = 1 ... 2 ° into the radial ohm direction of the circle center side, the spiral corrugations formed multistart with an even number of taps, and the beginning of the spiral of Archimedes at each of the ends of the circle coincides with one of its generators, with the value of the amplitude A _with the sinusoid is equal to half the height in the cutting portion of the disc, and the number of its end faces protrusions n is determined depending on the degree of lowering the grinding temperature according to the formula n = π · D / P, where D is the outer diameter of the circle, m; P is the period of the sinusoid, m, determined by the formula P = 2 (N / 2) ² · V _and · C / (10 · a), H is the total height of the circle along the vertices of the sinusoid, equal to the width of the cut groove of the workpiece, m; V _and - the frequency of rotation of the circle, m / s; a - thermal diffusivity of the workpiece material, m ² / s; C is the sinusoidality coefficient, determined by the formula C = (1-k _k ) / (k _A + k _B · V _rel ), V _rel - the relative speed of movement of the workpiece, determined by the formula V _rel = V _s · N / 2a, V _s - rotation speed of the workpiece, m / s; k _A is a coefficient depending on the degree of lowering the grinding temperature and takes values of 1.0; 1.0; 4.0; 5.0 with a decrease in temperature by 10%, 20%, 30% and 40%, respectively; k _B is a coefficient depending on the degree of lowering the grinding temperature and takes values of 0.1; 0.32; 0.75; 1.7 with a decrease in temperature by 10%, 20%, 30% and 40%, respectively; k _k - coefficient depending on the relative speed and taking values - 0.18; 0.28; 0.53; 0.74 with a decrease in grinding temperature by 10%, 20%, 30% and 40%, respectively.

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