CN102806508B - Complex molded surface grinding method for three-axis linkage mechanical sealing ring - Google Patents

Abstract

The invention discloses a complex surface grinding method for a three-axis linkage mechanical seal ring, which belongs to the technical field of complex surface grinding. It is characterized in that it adopts a workpiece shaft, a cup-shaped grinding wheel, a grinding wheel shaft, a swing table, and a linear moving platform. The swing axis of the swing table intersects vertically, the rotation axis of the grinding wheel shaft is parallel to the movement direction of the linear moving platform, and the cutting grinding is done through the end face of the grinding wheel. When grinding the inclined corrugated surface, the rotary motion of the workpiece axis, the reciprocating swing of the swing table and the linear motion of the linear moving platform are controlled in linkage. When grinding the dam surface, the axis of rotation of the cup-shaped grinding wheel is parallel to the axis of rotation of the workpiece shaft. The effects and benefits of the present invention can realize the complex shape of the hydrodynamic sealing ring composed of a flat circular ring-shaped dam surface and a slightly inclined straight line whose radial profile is a slightly inclined corrugated surface whose inclination angle changes periodically along the circumferential direction Precision, low surface roughness machining.

Description

A three-axis linkage mechanical seal ring complex surface grinding method

technical field

The invention belongs to the technical field of complex shape surface grinding, and relates to the grinding of mechanical seal rings, in particular to a kind of bevel whose flat circular dam surface and radial profile are slightly inclined straight lines and whose inclination angle changes periodically along the circumferential direction. An ultra-precision grinding method for complex-shaped surfaces of hydrodynamic and static-pressure combined mechanical seal rings composed of corrugated surfaces.

Background technique

Mechanical seals are widely used in rotating equipment such as pumps, compressors, reactors, agitators, centrifuges and filters that transfer liquids or gases. The development of modern industrial production has higher and higher requirements on the performance and life of mechanical seals working under conditions of high speed, high pressure and high temperature. In the early mechanical seals, the two sealing end faces that fit each other were designed and manufactured as flat as possible, in order to make the effective gap between the two sealing end faces as small as possible to reduce leakage. However, the fluid film formed between these two planes is easy to break, so that the two sealing end faces work more in a contact state, resulting in greater friction, premature wear and even damage. In order to reduce wear and avoid damage, people maintain a stable fluid film by opening deep grooves, shallow grooves, radial tapers, radial shoulders, circumferential waves and other structures on the flat end faces of the seal rings to avoid direct contact between the two seal end faces, thereby A series of new mechanical seals were produced. The most representative one is a fluid dynamic and static pressure combined mechanical seal proposed by Lebeck A. O. et al. in the United States in the 1980s. In this fluid dynamic and static pressure combined mechanical seal, the moving ring can also be a static ring. The end face is composed of a flat circular ring-shaped dam surface and a slightly inclined straight line whose radial profile changes periodically along the circumferential direction. When paired with another flat sealing ring, corrugations are formed on the sealing interface along the circumferential direction. The advantage is that the hydrostatic pressure effect generated by the radial convergence gap ensures that there is always a liquid film between the two sealing interfaces during shutdown and operation, and the fluid dynamics generated by the circumferential corrugated gap The pressure effect ensures sufficient opening force to separate the two sealing faces, while the sealing dam face enhances the leakage control capability. The test results show that this sealing form has greater advantages than the dynamic pressure seal with grooved end face and the static pressure seal with convergent gap along the radial direction. At present, this fluid dynamic and static pressure combined mechanical seal has been successfully applied in steam turbines, oil and gas pipeline pumps, nuclear main pumps and high temperature pumps in petrochemical facilities. The sealing ring of this sealing form is usually made of high-hardness materials such as silicon carbide, silicon nitride, and tungsten carbide. The surface shape accuracy of the sealing ring dam surface and oblique corrugated surface is required to be within 1 to 2 helium light bands (1 The length of the helium band is 0.29 microns), and the surface roughness Ra is within 5 nanometers. Since the inclined corrugated surface is a free-form surface in space, it cannot be processed by traditional grinding methods. However, when multi-axis linkage CNC point contact grinding is used, the grinding wheel wears quickly and the shape retention is poor, so it is difficult to obtain satisfactory surface accuracy. ; Airbag polishing, magnetorheological polishing, ion beam polishing and other computer-controlled optical surface modification technologies can realize high-precision processing of optical curved surfaces, but the processing efficiency is low, and there are edge effects to varying degrees when processing ring-shaped parts. The intersection with the oblique corrugated surface is a first-order differential discontinuity, and it is extremely difficult to accurately modify the shape; there is a problem of large surface roughness when laser processing is used.

Contents of the invention

The purpose of the present invention is to provide a complex surface grinding method for a three-axis linkage mechanical seal ring, which can realize a slightly inclined straight line whose inclination angle changes periodically along the circumferential direction from a flat annular dam surface and a radial profile. The hydrodynamic and static pressure combination type mechanical seal ring composed of corrugated surface is processed with complex shape surface, high surface accuracy and low surface roughness.

The present invention adopts following technical scheme to realize:

A workpiece shaft, a cup-shaped grinding wheel, a grinding wheel shaft, a swing table, and a linear moving platform are used to perform plunge grinding through the end face of the cup-shaped grinding wheel. The sealing ring is clamped at the center of the front end of the workpiece shaft, and the workpiece shaft drives the seal to perform high-precision rotary motion around the rotary axis of the workpiece shaft. The radial runout and end surface runout of the workpiece shaft are 0~0.1 microns, and the rotary positioning error is 0~1. point. The cup-shaped grinding wheel is installed on the grinding wheel shaft, and the cup-shaped grinding wheel performs high-precision rotary motion around its rotary axis. The radial runout and end surface runout of the grinding wheel shaft are 0~0.1 microns. The workpiece shaft is installed on the swing table, the grinding wheel shaft is installed on the slide plate of the linear moving platform, and the swinging table and the linear moving platform are installed on the machine bed. The rotation axis of the workpiece shaft is perpendicular to the swing axis of the swing table, the rotation axis of the grinding wheel shaft is perpendicular to the swing axis of the swing table, the rotation axis of the grinding wheel shaft is parallel to the movement direction of the linear moving platform, and the end face of the cup-shaped grinding wheel faces the workpiece axis. The swing table drives the workpiece shaft to perform high-precision reciprocating swing around the swing axis of the swing table, and the swing positioning error is 0~20 seconds. The linear moving platform drives the grinding wheel shaft and the cup-shaped grinding wheel to perform high-precision linear motion, and the positioning accuracy is 0-20 nanometers. The diameter of the cup-shaped grinding wheel is 150-700 mm, the width of the end face of the cup-shaped grinding wheel is 2-5 mm, and the abrasive used for the cup-shaped grinding wheel is 1000# or finer-grained diamond. When the axis of rotation of the cup-shaped grinding wheel is parallel to the axis of rotation of the workpiece shaft, the distance from any point on the axis of rotation of the workpiece shaft to the plane passing through the axis of rotation of the cup-shaped grinding wheel and the axis of swing of the swing table is equal to one-half of the pitch diameter of the oblique corrugated surface. The distance between the rotary axis of the cup-shaped grinding wheel and the rotary axis of the workpiece shaft is greater than the square root of the square root of the radius of the grinding wheel and the inner radius of the oblique corrugation surface, and the distance between the rotary axis of the cup-shaped grinding wheel and the rotary axis of the workpiece shaft is smaller than the sum of the square root of the radius of the grinding wheel and the outer radius of the oblique corrugated surface. square. The rotary motion of the workpiece axis, the reciprocating swing of the oscillating table, and the linear motion of the linear moving platform can be controlled in linkage. The rotating speed of the cup-shaped grinding wheel is 50~10000 rpm, and the rotating speed of the workpiece shaft is 0.1~500 rpm.

First grind the oblique corrugated surface. When grinding the oblique corrugated surface, the grinding wheel shaft drives the cup-shaped grinding wheel to rotate around the rotation axis of the grinding wheel shaft, the workpiece shaft drives the seal to rotate around the rotation axis of the workpiece shaft, and the swing table drives the workpiece shaft and seal to swing around The swing axis of the worktable swings back and forth, and the linear moving platform drives the grinding wheel shaft and the cup-shaped grinding wheel to make a linear motion. It is necessary to control the rotary motion of the workpiece axis, the reciprocating swing of the oscillating table and the reciprocating linear motion of the linear moving platform to generate oblique corrugated surfaces. During grinding, the feeding motion of the cup-shaped grinding wheel relative to the sealing ring is realized by the linear motion of the linear moving platform.

When grinding oblique corrugated surfaces, if the feed motion of the cup-shaped grinding wheel driven by the linear moving platform is not considered, the wear of the grinding wheel and various errors, the rotary motion of the workpiece axis, the reciprocating swing of the swing table and the straight line of the linear moving platform are not considered. The movement will make the intersection of the cup-shaped grinding wheel and the cylindrical surface containing the inner periphery of the oblique corrugated surface always be on the inner periphery of the oblique corrugated surface of theoretically correct geometry, and at the same time make the intersection of the cup-shaped grinding wheel and the cylindrical surface containing the outer periphery of the oblique corrugated surface always be on Theoretical correct geometry on the outer perimeter of the oblique corrugated surface.

When grinding the oblique corrugated surface, the speed of the cup-shaped grinding wheel is 100-5000 rpm, the rotational speed of the workpiece shaft is 0.1-50 rpm, and the end face of the cup-shaped grinding wheel is used for plunge grinding.

After the inclined corrugated surface is processed, the sealing dam surface is ground. When grinding the sealing dam surface, the swing table is locked at the position where the rotation axis of the cup-shaped grinding wheel is parallel to the rotation axis of the workpiece shaft. The workpiece shaft drives the seal to surround the rotation axis of the workpiece shaft at a constant speed. Rotation, the grinding wheel shaft drives the cup-shaped grinding wheel to rotate at a constant speed around the rotation axis of the grinding wheel shaft, and the linear moving platform drives the cup-shaped grinding wheel to perform feed motion. / min, using the end face of the cup wheel for plunge grinding until the final size is ground.

Since the end face of the cup-shaped grinding wheel with an end face width of only 2-5 mm is used for plunge grinding, the grinding contact area between the cup-shaped grinding wheel and the workpiece runs through from the inner periphery to the outer periphery of the surface to be processed, and no radial cutting is required. The grinding of oblique corrugated surface or dam surface can be realized by giving movement, so there is no need to do complex trajectory planning when multi-axis linkage CNC point contact grinding is used.

Since the maximum radial profile inclination angle of the oblique corrugated surface of the sealing ring is only a few hundred microradians, when grinding the oblique corrugated surface of the sealing ring, the included angle between the axis of rotation of the cup-shaped grinding wheel and the axis of rotation of the workpiece shaft is extremely small, within a few hundred microradians Inside, the two axes are roughly parallel, so when grinding the oblique corrugated surface and sealing dam surface, the contact arc length, contact area and cutting angle between the cup-shaped grinding wheel and the sealing ring are almost unchanged, the grinding force is kept constant, and the processing state is stable. , which is beneficial to ensure the machining accuracy.

Since the end face of the cup-shaped grinding wheel with an end face width of only 2-5 mm is used for plunge grinding, the cup-shaped grinding wheel and the sealing ring are in line contact during grinding, and the cutting speed, cutting depth and cutting path of the effective abrasive grains on the end face of the grinding wheel The length is basically the same, so the wear on the end face of the grinding wheel is uniform, the geometry of the end face of the cup-shaped grinding wheel remains unchanged during grinding, and there is no problem of precise modification of the grinding wheel.

Since the wear of the grinding wheel is only shown as the uniform loss of the end face of the cup-shaped grinding wheel, the wear of the cup-shaped grinding wheel only affects the distance between the end face of the cup-shaped grinding wheel and the swing axis of the swing table, and the wear of the grinding wheel can be effectively compensated by the linear motion of the linear moving platform.

The effect and benefit of the present invention are that it can be used for the complex shape of the hydrodynamic and static pressure combined mechanical seal ring composed of a flat circular ring-shaped dam surface and a slightly inclined straight line whose radial profile changes periodically along the circumferential direction of the oblique corrugated surface. Surface processing with high surface accuracy and low surface roughness.

Description of drawings

Fig. 1 is a schematic diagram of the complex surface of the sealing ring to be processed in the present invention.

Fig. 2 is a grinding schematic diagram of the present invention.

In the figure: 1 sealing ring; 2 inclined corrugated surface; 3 dam surface; 4 swing table; 5 workpiece shaft; 6 cup-shaped grinding wheel; 7 linear moving platform; 8 grinding wheel shaft.

Detailed ways

The specific implementation manner of the present invention will be described in detail below in combination with the technical scheme and accompanying drawings.

As shown in Figure 1, the end face of the sealing ring to be processed is a combination of hydrodynamic and static pressure, which is composed of a flat circular ring-shaped dam surface and an oblique corrugated surface whose radial profile is a slightly inclined straight line and whose inclination angle changes periodically along the circumferential direction. The complex surface of the mechanical seal ring has an inner diameter of 160 mm, an outer diameter of 200 mm, an outer diameter of the sealing dam surface of 170 mm, and the inclination angle of the radial contour of the oblique corrugated surface changes periodically along the circumferential direction between 0 and 0.0006 radians. The number of corrugations is 9, and the material is pressureless sintered silicon carbide.

As shown in Figure 2, a workpiece shaft supported by a high-precision air bearing, a cup-shaped grinding wheel, a high-precision air bearing supported grinding wheel shaft, a high-precision hydraulic swing table and a high-precision hydraulic linear moving platform are used. Plunge grinding on the end face of a shaped grinding wheel.

The sealing ring is clamped at the center of the front end of the workpiece shaft, and the workpiece shaft drives the seal to perform high-precision rotary motion around the rotary axis of the workpiece shaft. The radial runout and end surface runout of the workpiece shaft are less than 0.05 microns, and the rotary positioning error is less than 0.5 minutes. The cup-shaped grinding wheel is installed on the grinding wheel shaft, and the cup-shaped grinding wheel performs high-precision rotary motion around its rotary axis, and the radial runout and end surface runout of the grinding wheel shaft are less than 0.05 microns. The workpiece shaft is installed on the swing table, the grinding wheel shaft is installed on the slide plate of the linear moving platform, and the swinging table and the linear moving platform are installed on the machine bed. The rotation axis of the workpiece shaft is perpendicular to the swing axis of the swing table, the rotation axis of the grinding wheel shaft is perpendicular to the swing axis of the swing table, the rotation axis of the grinding wheel shaft is parallel to the movement direction of the linear moving platform, and the end face of the cup-shaped grinding wheel faces the workpiece axis. The oscillating table drives the workpiece shaft to do high-precision reciprocating swing around the oscillating axis of the oscillating table. The oscillating positioning error is 0-8 seconds. The linear motion platform drives the grinding wheel shaft and the cup-shaped grinding wheel to perform high-precision linear motion, and the positioning accuracy is 0-20. Nano. The diameter of the cup-shaped grinding wheel is 350 millimeters, the working face width of the end face of the cup-shaped grinding wheel is 3 millimeters, and the used abrasive material of the cup-shaped grinding wheel is 1000# diamond. When the axis of rotation of the cup-shaped grinding wheel is parallel to the axis of rotation of the workpiece shaft, the distance from any point on the axis of rotation of the cup-shaped grinding wheel to the plane passing through the axis of rotation of the cup-shaped grinding wheel and the swing axis of the swing table is equal to 92.5mm. The shaft rotation axis distance is 197 mm. The rotating speed of the cup-shaped grinding wheel is 50~5000 rpm, and the rotating speed of the workpiece shaft is 0.1~500 rpm.

First grind the oblique corrugated surface. When grinding the oblique corrugated surface, the workpiece shaft drives the seal to rotate around the rotary axis of the workpiece shaft, the grinding wheel shaft drives the cup-shaped grinding wheel to rotate around the rotary axis of the grinding wheel shaft, and the swing table drives the workpiece shaft and seal to swing around The swing axis of the worktable swings back and forth, and the linear moving platform drives the grinding wheel shaft and the cup-shaped grinding wheel to make a linear motion. It is necessary to control the rotary motion of the workpiece axis, the reciprocating swing of the oscillating table and the linear motion of the linear moving platform to generate oblique corrugated surfaces. The feeding motion of the cup-shaped grinding wheel is realized by the linear motion of the linear moving platform during grinding.

When grinding oblique corrugated surfaces, if the feed motion of the cup-shaped grinding wheel driven by the linear moving platform is not considered, the wear of the grinding wheel and various errors, the rotary motion of the workpiece axis, the reciprocating swing of the swing table and the straight line of the linear moving platform are not considered. The movement will make the intersection of the cup-shaped grinding wheel and the cylindrical surface containing the inner periphery of the oblique corrugated surface always be on the inner periphery of the oblique corrugated surface of theoretically correct geometry, and at the same time make the intersection of the cup-shaped grinding wheel and the cylindrical surface containing the outer periphery of the oblique corrugated surface always be on Theoretical correct geometry on the outer perimeter of the oblique corrugated surface. When grinding the oblique corrugated surface, the speed of the cup-shaped grinding wheel is 500 rpm, the rotational speed of the workpiece shaft is 1 rpm, the feed rate is 0.5 μm/min, and the end face of the cup-shaped grinding wheel is used for plunge grinding.

After the oblique corrugated surface is processed, the sealing dam surface is ground. When grinding the sealing dam surface, the swing table is locked at the position where the rotation axis of the cup-shaped grinding wheel is parallel to the rotation axis of the workpiece shaft. The workpiece shaft drives the seal to rotate around the rotation axis of the workpiece shaft. The grinding wheel shaft drives the cup-shaped grinding wheel to rotate around the rotation axis of the grinding wheel shaft, and the linear moving platform drives the cup-shaped grinding wheel to perform feed motion. The end face is plunge-cut grinding with a feed rate of 1 micron/min and a micro-feed motion resolution of 0.1 micron until the final size is ground.

Claims (4)

1. a three-shaft linkage mechanical seal ring complicated surface method for grinding, adopt a workpiece spindle, a cup emery wheel, a grinding wheel spindle, a swing workbench and a traveling priority platform, by cup emery wheel end face, do crush grinding, it is characterized in that sealing ring is clamped in workpiece spindle front end center, workpiece spindle is arranged on and swings on workbench, grinding wheel spindle is arranged on the slide carriage of traveling priority platform, swinging workbench and traveling priority platform is arranged on bed piece, the axis of rotation of workpiece spindle is vertical with the axis of oscillation that swings workbench, the axis of rotation of grinding wheel spindle intersects vertically with the axis of oscillation that swings workbench, the axis of rotation of grinding wheel spindle is parallel with the direction of motion of traveling priority platform, the end face of cup emery wheel is towards workpiece spindle, the gyration of workpiece spindle is controlled in interlock, swing the reciprocally swinging of workbench and the linear reciprocating motion of traveling priority platform and generate oblique ripple face.

2. a kind of three-shaft linkage mechanical seal ring complicated surface method for grinding according to claim 1, it is characterized in that, when cup emery wheel axis of rotation is parallel with workpiece spindle axis of rotation, the distance that on workpiece spindle axis of rotation, any point has been cup emery wheel axis of rotation and has been swung the plane of workbench axis of oscillation equals 1/2nd of oblique ripple face central diameter, after being greater than grinding wheel radius and oblique ripple face inside radius quadratic sum, cup emery wheel axis of rotation and workpiece spindle axis of rotation distance extract square root, after being less than grinding wheel radius and oblique ripple face outer radius quadratic sum, cup emery wheel axis of rotation and workpiece spindle axis of rotation distance extract square root.

3. a kind of three-shaft linkage mechanical seal ring complicated surface method for grinding according to claim 1, it is characterized in that, during grinding oblique ripple face, if disregard the feed motion that traveling priority platform drives cup emery wheel to do, also disregard abrasion of grinding wheel and various error, the gyration of workpiece spindle, swing the reciprocally swinging of workbench and the rectilinear motion of traveling priority platform by make cup emery wheel with the face of cylinder intersection point that comprises oblique ripple face inner rim all the time on the oblique ripple face inner rim of theoretical perfect form, and the face of cylinder intersection point that makes cup emery wheel and comprise oblique ripple face neighboring is all the time on the oblique ripple face neighboring of theoretical perfect form.

4. a kind of three-shaft linkage mechanical seal ring complicated surface method for grinding according to claim 1, it is characterized in that, oblique ripple face machines rear grinding sealing dam facing, swings workbench and be locked in the cup emery wheel axis of rotation position parallel with workpiece spindle axis of rotation during grinding sealing dam facing.