RU2121914C1 - Grinding spindle assembly - Google Patents

Abstract

FIELD: machining of bodies of revolution by abrasive tool with axially shifted cutting layer, applicable in designing, manufacture and use of grinding, buffing, lapping and finishing machines and appliances. SUBSTANCE: grinding spindle assembly has shaft 3 installed in fixed poppet sleeve 1 on two radial supports 4 and 5, the distance between them is l, and abrasive wheel 6 with axially shifted cutting layer supported as a cantilever on the shaft on the side of front support 5 at an angle to the plane of rotation, and driven pulley on the other side. Besides, the shaft is furnished with support 7 oscillating synchronously to axially shifted cutting layer, support 7 is positioned at distance Xmax=0.42265l from front support 5' in the point of maximum deflection of shaft axis; the value of oscillation of support 7 is the distance between point Xmax and point Xmin of minimum deflection on the axis with maximum deflection nearest to front support 5. EFFECT: enhanced reliability, durability and quality of machined parts by decreasing alternating dynamic loads due to installation of an additional oscillating support operating in points of equal shaft deflection. 3 dwg

Description

 The invention relates to the processing of bodies of revolution by an abrasive tool with an axially offset cutting layer (APC) and can be used in the design, manufacture and operation of grinding, polishing, finishing and finishing machines and devices.

 The spindle of a high-speed grinding machine is known, made in the form of a rotor mounted in two bearing bearings, and driven into rotation by a pulley from an electric motor through a belt drive, in which one of the bearing bearings is made elastic and the other is articulated, a pulley is mounted above the latter so that the force belt tension passes through its center [1].

 The disadvantages of the known spindle are reduced service life, deterioration in grinding quality and increased vibration when using grinding wheels with an axially offset cutting layer, operating under conditions of a radial load cycling in the axial direction.

 Closest to the invention in technical essence is a spindle assembly of a grinding machine, comprising a fixed quill, a shaft mounted on bearings in the quill, and a driven pulley and an abrasive wheel fixed to the shaft from different sides on the shaft, while the shaft is equipped with a flywheel fixed to the console between the abrasive circle and support, and the center of mass of the flywheel is located in the plane of this support on the axis of rotation of the shaft [2].

 The disadvantages of the known site are also a decrease in reliability and durability, deterioration in the quality of the processed products by grinding wheels with an axially displaced cutting layer, operating under conditions of a radially dynamically unbalanced load cyclically moving in the axial direction, causing vibration.

 The objective of the invention is to increase reliability, durability and improve the quality of the processed products by reducing variable dynamic loads due to the installation of additional oscillating bearings, working in places of equal deflection of the shaft.

The problem is solved through the use of a grinding spindle assembly containing a shaft mounted in a fixed quill on two radial bearings, the distance between which l, and mounted on the shaft from the front support at an angle to the plane of rotation with an axially offset cutting layer mounted cantileverly, and with on the other hand, the driven pulley, in addition, the shaft is equipped with a support oscillating synchronously to the axially displaced cutting layer of the circle, located at a distance of X _max = 0.42265 • l from the front support - at the maximum bending of the shaft axis, and the magnitude of the support oscillation is the distance between the points X _max and the point of minimum deflection closest to the front support on the axis with maximum deflection.

 In FIG. 1 shows a loading diagram of a cyclically acting cutting force and deflection of the shaft axis; in FIG. 2 - the proposed assembly, axial section; in FIG. 3 - oscillating support, made in the form of a ball bearing with axial displacement of the outer groove of the inner ring.

 The grinding spindle assembly comprises a pinol 1, a driven pulley 2, a shaft 3 mounted on bearings 4 and 5, an abrasive wheel 6 mounted on the shaft 3 at an angle α to the plane of rotation, and an oscillating support 7.

In the cutting zone in contact with the workpiece 8 of the axially displaced cutting layer of the grinding wheel 6, a cutting force P _z arises that oscillates in the axial direction with an amplitude A _k . The distance C _i from the front support 5 to the place of action P _z will cyclically change
C _i = C _min + A _k / 2 - (D • tgα • sinωt) / 2,
Where
C _min - the minimum distance from the front support to the place of action of the cutting force P _z ;
D is the diameter of the circle;
ω is the angular frequency of rotation of the shaft;
t is time.

где
X - текущая координата;
B - модуль упругости материала вала;

осевой момент инерции сечения вала: I_x = πd⁴/64;
d - диаметр вала.In the front support 5, the reduced alternating moment will act
M ₅ = P _z • C _i = P _z [C _min + A _k / 2 - (D • tgα • sinωt) / 2],
causing variable deflection f _i with a rotation angle φ of the shaft axis, which are determined by known formulas

Where
X is the current coordinate;
B is the elastic modulus of the shaft material;

axial moment of inertia of the shaft section: I _x = πd ^4/64;
d is the diameter of the shaft.

l - расстояние между 4 и 5 опорами.

l is the distance between 4 and 5 supports.

Известно, что угол поворота оси вала есть первая производная прогиба, определим φ

Но так как максимальный прогиб оси вала будет в точке, где φ = 0, определим значение X максимального прогиба
X² - 2lX + (2/3) l² = 0, т.е. X = 0,42265•l.Substituting the value of φ _{o the} angle of rotation of the shaft axis in the formula that defines the deflection, we obtain

It is known that the angle of rotation of the shaft axis is the first derivative of the deflection, we define φ

But since the maximum deflection of the shaft axis will be at the point where φ = 0, we determine the value X of the maximum deflection
X ² - 2lX + (2/3) l ² = 0, i.e. X = 0.42265 • l.

При подстановке значений C_min и C_max определим максимальные прогибы f $\genfrac{}{}{0ex}{}{\text{Cmin}}{\text{max}}$ и f $\genfrac{}{}{0ex}{}{\text{Cmax}}{\text{max}}$ в крайних положениях шлифовального круга. Из вышеприведенного видно, что под воздействием осциллирующей в осевом направлении силы резания P_z ось вала изгибается с переменной величиной максимального прогиба на расстоянии X = 0,42265l от передней опоры 5.In this case, the maximum deflection

When substituting the values of C _min and C _max define the maximum deflections f $\genfrac{}{}{0ex}{}{\text{Cmin}}{\text{max}}$ and f $\genfrac{}{}{0ex}{}{\text{Cmax}}{\text{max}}$ in extreme positions of the grinding wheel. From the above it is seen that under the influence of the cutting force oscillating in the axial direction P _z, the shaft axis bends with a variable maximum deflection at a distance X = 0.42265l from the front support 5.

на оси вала при максимальном прогибе, когда круг находится в положении C_max, путем подстановки известных значений

и C_max в формулу f_i (см. выше)

Приводим к канонической форме и вводим обозначение постоянной величины.Define X _min deflection location

on the shaft axis with maximum deflection when the circle is in the C _max position, by substituting known values

and C _max in the formula f _i (see above)

We bring to the canonical form and introduce the designation of a constant value.

тогда
X_min = [((27•a² - 4l⁶)^1/2 - 27^1/2•a)^2/3 + ((27a² - 4l⁶)^1/2 - 27^1/2•a)^1/3 • 3^1/6 • 6^1/3 • l + 3^1/3 • 6^2/3 • l²]/[(3(27a² - 4l⁶)^1/2 - 27^1/2•a)^1/3 • 3^1/6 • 6^1/3].X ³ - 3l • X ² + 2l ² • X + a = 0,
Where

then
X _min = [((27 • a ² - 4l ⁶ ) ^1/2 - 27 ^1/2 • a) ^2/3 + ((27a ² - 4l ⁶ ) ^1/2 - 27 ^1/2 • a) ^{1 / 3} • 3 ^1/6 • 6 ^1/3 • l + 3 ^1/3 • 6 ^2/3 • l ² ] / [(3 (27a ² - 4l ⁶ ) ^1/2 - 27 ^1/2 • a) ^{1 / 3} • 3 ^1/6 • 6 ^1/3 ].

If we establish an oscillating support with amplitude A ₀ = X _max - X _{min, the} support 7 is synchronously axially displaced by the cutting layer of the wheel and the axial displacement P _z , where the shaft will experience constant deflections throughout the cycle, then the support 7, trying to return the shaft to a neutral position, will be subjected exposure to a constant moment. This does not cause vibration and increases the reliability and service life of the unit.

 Example: On a modernized model 3P722 surface grinding machine, the flat surface of the body is ground. The allowance on the side h = 0.35 mm Ra = 1.25 μm. The workpiece material is hardened steel 45XH, hardness HRC 50.

We choose a grinding wheel ПП 14А25ПСМ27К1А 35 m / s D _k = 450 mm B _k = 80 mm.

We set it at an angle α = 5 ^o , while the amplitude of the inclined circle - And _to = 40 mm

With the assigned cutting modes:
n _k = 1500 min ^-1 ; V _k = 35 m / s; V ₃ = 16 m / min; S _o = 32 mm / table stroke; S _tx = 0.015 mm (on the reverse of the grinding head); cutting power N _res = 8.65 kW, and the force P _z = (1020 • 60 • N _res ) / V _k = 250H.

Determine the maximum deflection of the shaft axis with the length of the console mounting the grinding wheel C = 100 mm; distance between supports l = 300 mm; d = 30 mm, in extreme positions C _min = 80 mm, C _max = 120 mm. Shaft material Steel 50 with E = 2.1 • 10 ⁵ MPa.

-0,0138 мм

-0,0208 мм
Максимальный прогиб

оси вала будет на расстоянии X_max = 0,42265•l = 0,1268 м от передней опоры.

-0.0138 mm

-0.0208 mm
Maximum deflection

the axis of the shaft will be at a distance of X _max = 0.42265 • l = 0.1268 m from the front support.

на оси вала, когда круг в положении C_max : X_min = 0,0505 м
Тогда величина амплитуды A_o осциллирующей опоры будет равна A_o = 0,1268 - 0,0505 = 0,0763 м.Define X _{min the} distance from the front support to the deflection

on the axis of the shaft when the circle in position C _max : X _min = 0,0505 m
Then the amplitude A _{o of the} oscillating support will be equal to A _o = 0.1268 - 0.0505 = 0.0763 m.

Particularly effective impact additional oscillating support 7 to reduce deflection of the shaft axis under the action of a pulsating alternating reduced moment M ₅ on the support 5 at large values of A _k circle oscillation.

 Thus, the proposed site has increased durability due to the reduction of variable dynamic loads due to the installation of an oscillating support, working in places of equal deflection of the shaft, and also improves the quality of the processed surface.

Claims (1)

A grinding spindle assembly comprising a shaft mounted in a fixed quill on two radial bearings located at a distance l and cantilevered on the shaft from the front support side by an abrasive wheel, and on the other hand, a driven pulley, characterized in that the abrasive wheel is mounted on the shaft at an angle to the plane of rotation axially offset to form a cutting layer, and the shaft is provided with a synchronously oscillating axial displacement of the cutting wheel support layer placed at a distance X _max = 0,42265l from the front pillar in place maxim nogo deflection axis of the shaft, wherein the support is equal to the magnitude difference of the oscillation distance X _max X _min and the distance from the front pillar nearest point thereto on the minimum deflection axis with maximum deflection.

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