RU2094207C1 - Method of abrasive working of rotation surface - Google Patents

Abstract

FIELD: mechanical engineering. SUBSTANCE: width of a tool for abrasive working is defined by a relationship presented in the invention description. EFFECT: simplified method. 6 dwg

Description

 The invention relates to mechanical engineering, and in particular to methods of processing conical surfaces of revolution, for example, rings and rollers of tapered bearings with convex raceways.

 A known method of abrasive machining of surfaces of revolution (and.with. N 1199593 B 24 B 1/00 // B 24 B 19/06, B.I. N 47, 1985), in which they take a tool whose profile shape in the axial section of the workpiece represents an arc of a circle, and they roll around the surface to be machined, while the break-in speed and (or) the force of pressing the tool against the workpiece are selected according to the mathematical dependence.

 The disadvantage of this method is that it cannot provide high accuracy for the shape of the convexity on the conical surface, since during the rolling process a constant tool width (in the plane perpendicular to the axis of rotation of the workpiece) interacts with different diameters of the machined surface. The largest allowance will be removed from the smallest diameter of the conical blank, and the smallest allowance will be removed from the largest. Therefore, under such conditions of interaction of the tool with a conical surface, it is impossible to obtain the required convexity in it in the axial section of the workpiece.

,
где h_min минимальная ширина инструмента; R_min радиус профиля инструмента в месте минимальной его ширины; R_i радиус профиля инструмента в i-м сечении; h_i ширина инструмента в i-м сечении; перед прижимом устанавливают инструмент так, чтобы его сечение с минимальной шириной совпадало с сечением заготовки с минимальным радиусом, а усилие прижатия при обкатке изменяют пропорционально изменению ширины бруска.The closest in technical essence is the method of abrasive processing of surfaces of revolution (patent N 1809799, B 24 B 1/00, B.I. N 14, 1993), in which the tool, the shape of which in axial and cross sections represents a circle, and the length is the length of the workpiece’s machined surface, is pressed against the machined surface of the rotating workpiece and is rolled around the machined surface, the radius of the circumference of the tool in each cross section is selected by the formula

,
where h _{min is the} minimum width of the tool; R _{min the} radius of the profile of the tool in place of its minimum width; R _{i is the} radius of the profile of the tool in the i-th section; h _{i the} width of the tool in the i-th section; Before clamping, set the tool so that its cross section with a minimum width coincides with the cross section of the workpiece with a minimum radius, and the pressing force during break-in is changed in proportion to the change in the width of the bar.

 The disadvantage of this method is that it, removing a uniform allowance along the entire machined profile and while ensuring high accuracy of the profile in the axial section of the part, cannot provide the desired convexity of the conical surface, since it does not provide for targeted removal of the allowance from the conical surface in each of its transverse section.

 The aim of the invention is to improve the accuracy of a given shape of the generatrix of the conical surface by ensuring a constant ratio of the length of the cutting part of the tool to the area of the removed allowance, due to the shape of the generatrix, in each of the many sections of the interacting surfaces of the tool and the workpiece.

где R_i радиус заготовки в i-м сечении;
l_i длина режущей части инструмента в i-м сечении.The goal is achieved by using a tool whose width in each cross section is selected by the formula

where R _{i the} radius of the workpiece in the i-th section;
l _{i the} length of the cutting part of the tool in the i-th section.

при этом отношение длины режущей части инструмента, представляющей собой длину следа, оставленного на обрабатываемой поверхности совокупностью режущих зерен, к площади сечения удаляемого припуска в каждом из множества сечений взаимодействующих поверхностей инструмента и заготовки есть величина постоянная. Таким образом, предлагаемый способ соответствует критерию "новизна".A comparative analysis of the claimed solution with the prototype showed that the proposed method differs from the known one in that they take a tool whose width in each cross section is selected by the formula

the ratio of the length of the cutting part of the tool, which is the length of the trace left on the surface to be treated by the combination of cutting grains, to the cross-sectional area of the removed allowance in each of the many sections of the interacting surfaces of the tool and the workpiece is a constant. Thus, the proposed method meets the criterion of "novelty."

,
где R_i радиус заготовки в i-м сечении;
l_i длина режущей части инструмента в i-м сечении,
обеспечивает постоянство отношения длины режущей части инструмента, представляющей собой длину следа, оставленного на обрабатываемой поверхности совокупностью режущих зерен, к площади удаляемого припуска в каждом из множества сечений взаимодействующих поверхностей инструмента и заготовки. В результате этого на долю одного и того же зерна бруска в любом произвольном сечении приходится один и тот же микрообъем удаляемого металла, что обеспечивает управляемое удаление припуска различной величины по всему коническому профилю обрабатываемой поверхности и стабильную высокую точность формы выпуклого профиля в осевом сечении детали.Known technical solutions (and.with. N 1199593, B 24 B 1/00 // B 24 B 19/06, B.I. N 47, 1995), in which the tool runs around the work surface. However, the constant width of the tool does not provide the necessary shape of the bulge on the machined conical surface, which is achieved in the claimed technical solution. This allows us to conclude that the condition "inventive step"
Using a tool whose width in each cross section is selected by the formula

,
where R _{i the} radius of the workpiece in the i-th section;
l _{i the} length of the cutting part of the tool in the i-th section,
provides a constant ratio of the length of the cutting part of the tool, which is the length of the trace left on the surface to be treated by a set of cutting grains, to the area of the removed allowance in each of the many sections of the interacting surfaces of the tool and the workpiece. As a result of this, the same grain of the bar in any arbitrary section accounts for the same microvolume of the metal being removed, which ensures controlled removal of allowances of various sizes along the entire conical profile of the machined surface and stable high accuracy of the shape of the convex profile in the axial section of the part.

 In FIG. 1 shows a diagram of the implementation of the method; in FIG. 2 tools (whetstones) and a workpiece in a minimum section; in FIG. 3 the same in the intermediate section; in FIG. 4 the same in maximum cross section; in FIG. 5 shows a diagram of the formation of the cutting part of the tool in one of the cross sections of the workpiece; in FIG. 6 is a view of the shape of the working surface of the tool in the horizontal plane.

 The device comprises a bar 1 and a mandrel 2 for processing a workpiece 3 with a machined conical surface 4 of length L (Fig. 1). The magnitude of the removed metal layer Z gradually increases from the center to the edges of the treated surface 4.

The cast 1 in various cross sections of the workpiece has a variable width h ₁ , h ₂ and h ₃ (Fig. 2, 3 and 4). The area of the removed allowance S _z in sections 1-1, 2-2 and 3-3 is also variable. The cutting part of the tool with a length L involved in material removal is the length of the trace left on the surface to be processed by the set of cutting grains of the bar when interacting with the workpiece in the considered cross section for one full working stroke of the tool (Fig. 5). The working surface of the tool in the projection onto the horizontal plane has the shape of a trapezoid with concave lateral sides (Fig. 6).

The method is as follows. A bar 1 having a profile, the shape of which in the projection onto the horizontal plane has the shape of a trapezoid with concave lateral sides, and in the projection onto the vertical plane of the toroid, are preliminarily oriented relative to the part so that its end part of the minimum base of the trapezoid with a width of h ₁ coincides with the minimum diameter D _{min of the} treated surface 4, and the maximum base of the trapezoid with a width of h ₃ coincides with the maximum diameter D _max . After orientation, the bar 1 is set by combining its plane of symmetry in a longitudinal section with the middle of the length L of the work surface 4. The workpiece 3 is informed of the rotation and the bar 1 is pressed against its conical surface 4.

When rolling the abrasive bar 1 along the profile of the conical surface 4, each point of its working surface periodically comes into contact with the work surface without slipping, i.e. the interaction of the bar and the workpiece is carried out by point contact. Point m on bar 1 coincides with point m 'on the surface of the workpiece, and point n with point n'. The pressure of the bar 1 in the direction from the minimum diameter D _min (section 1-1) to a larger D _max (section 3-3) increases in proportion to the change in the diameters of the conical surface 4 in each of its cross sections (Fig. 1 4).

). Каждые последующие зерна (точки), срезая стружку, также увеличивают режущую часть инструмента установленную предыдущими зернами, и это продолжается до образования полной дуги режущей части инструмента l_i (положение инструмента 3-3, точки

). Следовательно, длина режущей части бруска, участвующая в съеме металла, представляет собой длину следа, оставленного на обрабатываемой поверхности совокупностью точек (режущих зерен) взаимодействия бруска и заготовки в рассматриваемом поперечном сечении. Дальнейшее перемещение бруска вызывает аналогичные образования режущих частей на обрабатываемой поверхности в любом из множества поперечных сечений заготовки. Длина следа в произвольном сечении (фиг. 2, 3 и 4) рассчитывается по формуле
l_i= R_i•2β,
где R_i радиус в i-м сечении, 2β угол охвата бруска. Откуда

Ширину инструмента в i-м сечении определяем по формуле (фиг. 2, 3 и 4)
h_i= 2•R_i•sin(β).
Подставляя получаем

,
где R_i радиус заготовки в i-м сечении;
l_i длина режущей части инструмента в i-м сечении заготовки.In the place of contact of the bar with the machined conical surface in a certain cross section, the formation of its cutting part begins (Fig. 5, the position of the tool 1-1, point A ₁ ). In this case, only one abrasive grain (or the point of interaction of the tool surface and the workpiece) is involved in the cutting work. When rolling the tool (for example, in the direction of the smallest diameter D _min ), grains come into operation, which, cutting chips and doing work, increase the cutting part of the tool in this cross section of the workpiece, set by the first grain (point) (tool position 2-2, points

) Each subsequent grains (points), cutting the chips, also increase the cutting part of the tool set by the previous grains, and this continues until the complete arc of the cutting part of the tool l _i (position of the tool 3-3, points

) Consequently, the length of the cutting part of the bar participating in the removal of metal is the length of the trace left on the surface to be treated by the set of points (cutting grains) of interaction between the bar and the workpiece in the cross section under consideration. Further movement of the bar causes a similar formation of cutting parts on the work surface in any of the many cross sections of the workpiece. The length of the trace in an arbitrary section (Fig. 2, 3 and 4) is calculated by the formula
l _i = R _i • 2β,
where R _{i is the} radius in the ith section, 2β is the angle of the bar. Where from

The width of the tool in the i-th section is determined by the formula (Fig. 2, 3 and 4)
h _i = 2 • R _i • sin (β).
Substituting we get

,
where R _{i the} radius of the workpiece in the i-th section;
l _{i the} length of the cutting part of the tool in the i-th section of the workpiece.

Due to the fact that the width of the tool in each cross section is selected according to the formula (1) and its working profile in this case has the shape of a trapezoid with concave lateral sides (Fig. 6), the value of the length of the cutting part of the tool in the cross sections of the workpiece is different. When the condition for the constancy of the ratio of the length of the cutting part of the tool l _i to the area of the removed allowance S _Zi (l _i / S _Zi = const) is fulfilled, the value of the metal layer to be removed gradually increases from the middle to the edges of the machined surface. From this it follows that for every single grain in an arbitrary section of the bar one and the same microvolume of the removed metal is accounted for.

 This condition provides the necessary convex symmetrical profile on the conical surface, and hence the high hermetic accuracy of the shape in its axial section.

 Example. Consider processing the raceway of the inner ring of a tapered bearing 7516.

The workpiece has a straight conical surface with a minimum diameter D _{min zag} = 40.24 mm, a maximum diameter D _{max zag} = 50.2 mm and an average diameter D _{cf zag} = 45.22 mm.

It is necessary to obtain a ring with a convex symmetrical profile on a conical surface in which D _{min det} = 40.14 mm, D _{max det} = 50.06 mm and D _{cf det} = 45.14 mm. Therefore, the allowance on the treated surface is distributed as follows: in section 1-1, the allowance Z _1-1 = 0.05 mm is removed, in section 2-2 Z _2-2 = 0.04 mm and in section 3-3 - Z _{3 -3} = 0.07 mm.

In accordance with the recommendations (Mazalsky VN Superfinishing machines. L. Mashinostroenie, 1988, 26 pp.), We take the angle of the bar 2β in section 1-1 equal to 2β _1-1 60 ^o .

При этом площадь удаляемого припуска составит

Исходя из постоянства отношения

,
находим величину C

Следовательно, можно определить длины режущих частей инструмента в сечениях 2-2 и 3-3, обеспечивающих заданную выпуклость.Then the length of the cutting part of the tool in section 1-1 will be equal to

The area of the removed allowance will be

Based on the constancy of the relationship

,
we find the value of C

Therefore, it is possible to determine the lengths of the cutting parts of the tool in sections 2-2 and 3-3, providing a given convexity.

Согласно формуле (1) находим ширину бруска в сечении 1-1

в сечении 2-2

в сечении 3-3

Исходя из пропорциональности количества зерен на рабочей поверхности инструмента определим количество зерен на длинах дуг режущей части в сечениях 1-1, 2-2 и 3-3. Приняв шаг между зернами равным t=0,1 мм, получаем

Объем металла, подлежащий удалению с поверхности заготовки (по ширине кольцо k=1 мм) составляет
в сечении 1-1

в сечении 2-2

в сечении 3-3

Тогда объем металла, приходящийся на одно зерно, составит
в сечении 1-1

в сечении 2-2

в сечении 3-3

Следовательно, предлагаемый способ обеспечивает условие, при котором на одно зерно в любом произвольном поперечном сечении взаимодействующих поверхностей режущего инструмента и детали приходится одинаковый микрообъем удаляемого металла, но при этом величина снимаемого припуска в данных сечениях различна, чем и достигается заданная высокая геометрическая точность формы выпуклого симметричного профиля конической поверхности.

According to the formula (1) we find the width of the bar in section 1-1

in section 2-2

in section 3-3

Based on the proportionality of the number of grains on the working surface of the tool, we determine the number of grains at the lengths of the arcs of the cutting part in sections 1-1, 2-2 and 3-3. Taking the step between grains equal to t = 0.1 mm, we obtain

The volume of metal to be removed from the surface of the workpiece (ring width k = 1 mm) is
in section 1-1

in section 2-2

in section 3-3

Then the volume of metal per grain is
in section 1-1

in section 2-2

in section 3-3

Therefore, the proposed method provides a condition under which the same microvolume of the metal to be removed is equal to one grain in any arbitrary cross-section of the interacting surfaces of the cutting tool and the part, but the size of the removed allowance in these sections is different, thereby achieving a given high geometric accuracy of the shape of a convex symmetric conical surface profile.

Claims (1)

A method of abrasive treatment of surfaces of revolution, in which the tool, the profile of which in axial and transverse sections is a circle and the length is equal to the length of the workpiece surface, is pressed against the workpiece surface of the rotating workpiece and is rolled around the surface to be machined, before the clamp, the tool is set so that its cross section with the minimum width coincided with the cross section of the workpiece with the minimum radius, and the pressing force during the run-in is changed in proportion to the change in the width of the bar , characterized in that they take the tool, the width in each cross section of which is selected by the formula

where R _{i the} radius of the workpiece in the i-th section;
l _{i the} length of the cutting part of the tool in the i-th section of the workpiece,
the ratio of the length of the cutting part of the tool, which is the length of the trace left on the surface to be treated by the combination of cutting grains, to the cross-sectional area of the removed allowance in each of the many sections of the interacting surfaces of the tool and the workpiece is a constant.

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