CA2356497A1 - Multi-axis polishing machine - Google Patents
Multi-axis polishing machine Download PDFInfo
- Publication number
- CA2356497A1 CA2356497A1 CA 2356497 CA2356497A CA2356497A1 CA 2356497 A1 CA2356497 A1 CA 2356497A1 CA 2356497 CA2356497 CA 2356497 CA 2356497 A CA2356497 A CA 2356497A CA 2356497 A1 CA2356497 A1 CA 2356497A1
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- CA
- Canada
- Prior art keywords
- polishing
- axis
- carriage
- wheel
- work piece
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
- B23Q1/00—Members which are comprised in the general build-up of a form of machine, particularly relatively large fixed members
- B23Q1/01—Frames, beds, pillars or like members; Arrangement of ways
- B23Q1/012—Portals
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
- B23Q1/00—Members which are comprised in the general build-up of a form of machine, particularly relatively large fixed members
- B23Q1/25—Movable or adjustable work or tool supports
- B23Q1/44—Movable or adjustable work or tool supports using particular mechanisms
- B23Q1/56—Movable or adjustable work or tool supports using particular mechanisms with sliding pairs only, the sliding pairs being the first two elements of the mechanism
- B23Q1/60—Movable or adjustable work or tool supports using particular mechanisms with sliding pairs only, the sliding pairs being the first two elements of the mechanism two sliding pairs only, the sliding pairs being the first two elements of the mechanism
- B23Q1/62—Movable or adjustable work or tool supports using particular mechanisms with sliding pairs only, the sliding pairs being the first two elements of the mechanism two sliding pairs only, the sliding pairs being the first two elements of the mechanism with perpendicular axes, e.g. cross-slides
- B23Q1/621—Movable or adjustable work or tool supports using particular mechanisms with sliding pairs only, the sliding pairs being the first two elements of the mechanism two sliding pairs only, the sliding pairs being the first two elements of the mechanism with perpendicular axes, e.g. cross-slides a single sliding pair followed perpendicularly by a single sliding pair
- B23Q1/623—Movable or adjustable work or tool supports using particular mechanisms with sliding pairs only, the sliding pairs being the first two elements of the mechanism two sliding pairs only, the sliding pairs being the first two elements of the mechanism with perpendicular axes, e.g. cross-slides a single sliding pair followed perpendicularly by a single sliding pair followed perpendicularly by a single rotating pair
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
- B23Q1/00—Members which are comprised in the general build-up of a form of machine, particularly relatively large fixed members
- B23Q1/25—Movable or adjustable work or tool supports
- B23Q1/44—Movable or adjustable work or tool supports using particular mechanisms
- B23Q1/56—Movable or adjustable work or tool supports using particular mechanisms with sliding pairs only, the sliding pairs being the first two elements of the mechanism
- B23Q1/60—Movable or adjustable work or tool supports using particular mechanisms with sliding pairs only, the sliding pairs being the first two elements of the mechanism two sliding pairs only, the sliding pairs being the first two elements of the mechanism
- B23Q1/62—Movable or adjustable work or tool supports using particular mechanisms with sliding pairs only, the sliding pairs being the first two elements of the mechanism two sliding pairs only, the sliding pairs being the first two elements of the mechanism with perpendicular axes, e.g. cross-slides
- B23Q1/621—Movable or adjustable work or tool supports using particular mechanisms with sliding pairs only, the sliding pairs being the first two elements of the mechanism two sliding pairs only, the sliding pairs being the first two elements of the mechanism with perpendicular axes, e.g. cross-slides a single sliding pair followed perpendicularly by a single sliding pair
- B23Q1/626—Movable or adjustable work or tool supports using particular mechanisms with sliding pairs only, the sliding pairs being the first two elements of the mechanism two sliding pairs only, the sliding pairs being the first two elements of the mechanism with perpendicular axes, e.g. cross-slides a single sliding pair followed perpendicularly by a single sliding pair followed perpendicularly by a single sliding pair
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
- B23Q11/00—Accessories fitted to machine tools for keeping tools or parts of the machine in good working condition or for cooling work; Safety devices specially combined with or arranged in, or specially adapted for use in connection with, machine tools
- B23Q11/001—Arrangements compensating weight or flexion on parts of the machine
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B13/00—Machines or devices designed for grinding or polishing optical surfaces on lenses or surfaces of similar shape on other work; Accessories therefor
- B24B13/06—Machines or devices designed for grinding or polishing optical surfaces on lenses or surfaces of similar shape on other work; Accessories therefor grinding of lenses, the tool or work being controlled by information-carrying means, e.g. patterns, punched tapes, magnetic tapes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B41/00—Component parts such as frames, beds, carriages, headstocks
- B24B41/005—Feeding or manipulating devices specially adapted to grinding machines
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B47/00—Drives or gearings; Equipment therefor
- B24B47/22—Equipment for exact control of the position of the grinding tool or work at the start of the grinding operation
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Grinding And Polishing Of Tertiary Curved Surfaces And Surfaces With Complex Shapes (AREA)
Abstract
The invention provides a multi-access polishing machine comprising a first carriage movable in a first horizontal direction, a second carriage mounted on said first carriage and movable in a second horizontal direction substantially perpendicular to the first horizontal direction and a third carriage mounted on said second carriage movable in a third direction substantially perpendicular to the said first two directions;
computer control means to locate said carriages in three dimensions; polishing means mounted on said carriages and movable therewith; said polishing means comprising a support having a motor capable of driving a polishing wheel about its axis of symmetry and a second motor capable of revolving said polishing wheel about an axis perpendicular to its axis of symmetry; a work piece positioning means adapted to locate a work piece relative to said polishing wheel. Said positioning means being computer controlled to rotate said work piece about at least one horizontal axis to present the surface of said work piece to said polishing wheel.
computer control means to locate said carriages in three dimensions; polishing means mounted on said carriages and movable therewith; said polishing means comprising a support having a motor capable of driving a polishing wheel about its axis of symmetry and a second motor capable of revolving said polishing wheel about an axis perpendicular to its axis of symmetry; a work piece positioning means adapted to locate a work piece relative to said polishing wheel. Said positioning means being computer controlled to rotate said work piece about at least one horizontal axis to present the surface of said work piece to said polishing wheel.
Description
MULTI-AXIS POLISHING MACHINE
This invention relates to an improved method and apparatus forfinishing the curved surface of lenses. In this context a lens refers to either a transparent or a reflective curved surface. In particular, it is intended to produce a more even accurate curved surface, especially for aspherical lenses, without the disadvantages of the previous techniques.
The apparatus and techniques described herein are applicable to either grinding or polishing, but especially the latter, and references to polishing should be taken to include both.
The development of modern lenses requires not merely the grinding and polishing of a concave or convex spherical surface but the more difficult accomplishment of providing extremely even surfaces for quality of light transmission and clarity of images, as well as the development of aspherical surfaces which are not of constant radius.
Although the term aspherical can refer to a curved surface with different radii of curvature in different axes or directions, it may also refer to a curved surface in which the radius of curvature varies from the centre to the periphery and it is this latter concept to which the present invention is chiefly directed, although it may be applied to both cases.
Whereas spherical surfaces may be generated by rotating a grinding or polishing wheel which is moved about a fixed point or axis at a constant radius, aspherical surfaces require more complex movement of the grinding or polishing instrument with changing arcs of curvature.
To accomplish this, polishing devices have been developed which move under computerized control according to a three-dimensional grid defined by coordinates in relation to three-dimensions such as an X, Y, and Z axes. This sort of apparatus allows the polishing device to be selectively controlled so that it can grind or polish the curved surface selectively and remove more material where there are high spots and less where there are areas of lower relief. One traditional method of polishing of lens involved spinning a cylindrical shaped polishing tool with a circumferential ring about a central axis while the central axis is caused to swing in a spherical arc about a fixed point. At the same time the workpiece was rotated about an axis coinciding to its axis of symmetry. This technique, however, does not work for aspherical lenses where the radius of curvature is constantly changing. It also does not work for the high quality technique which requires material to be ground or polished from the lens differentially at selective locations.
There also remains the problem of applying the polishing device to the surface in a manner which is substantially parallel to the surface at the point of contact.
In conducting the polishing operation, it is also important that the polishing device not be applied in a unique directional manner so as to create a pattern of rows or furrows corresponding to the direction of travel of the polishing device.
It is therefore the purpose of this invention to provide apparatus and a method for grinding and/or polishing lenses which will overcome the problems associated with aspherical lenses and at the same time to create a highly precise and even curved surface.
These objects and other advantages are sought to be achieved by means of the present invention which comprises a polishing machine having a first carriage movable in a substantially horizontal direction and a second carriage mounted on said first carriage and movable in a second substantially horizontal direction perpendicular to said first direction and a third carriage mounted on said second carriage and movable in a third direction substantially perpendicular to said first two directions. A polishing mechanism is mounted on the third carriage and consists of a polishing wheel having a polishing surface on its periphery and motor means to rotate the wheel about its axis symmetry and a second motor means designed to revolve the wheel about an axis perpendicular to its axis of symmetry so that the wheel will spin and rotate at the same time. The carriages are controlled by a computer programmed to locate the polishing means in any three dimensional position relative to the three coordinates of movement of the carriages so that the polishing wheel may be moved about or located at any desirable position on a work piece.
The machine is provided with a work piece positioning means which is adapted to locate and orient a work piece relative to the polishing wheel.
Preferably this positioning means is rotatable about at least one and preferably two perpendicular axes and is controlled by a computer so that the curved surface of a work piece such as a tense may be presented to the polishing wheel in such a way that the polishing wheel bears against the surface in a direction substantially normal to the surface at the position of contact.
Thus the polishing wheel may be located anywhere along three directions of movement and the polishing wheel will spin perpendicular to its axis of symmetry and rotate in a plane parallel to its axis of symmetry so that the direction of movement of the polishing wheel against the work piece surface is constantly changing.
Thus the polishing wheel may move in a series of traverses across the surface of the work piece, in response to the computer programme, and the direction of the polishing movement will be constantly changing so as to avoid creating furrows or patterns corresponding to the travel of the wheel.
The invention may be better understood by a detailed description of one embodiment thereof with reference to the attached drawings in which:
Figure 1 is a perspective view of one embodiment of the present invention;
Figure 2 illustrates a typical example of a lens of circular shape having a concave cross-section with the path of the polishing apparatus illustrated in broken lines;
Figure 3 is a computer generated graphic display of the irregularities on the surface of a lens;
Figure 3A is a computer generated graphic display of a cross-section of the surface of a lens relative to a datum.
Figure 4 illustrates the position of the polishing wheel of the present invention at the centre of a lens;
Figure 5 illustrates the relative position of the polishing wheel near the periphery of the lens;
Figure 6 illustrates the details of the movement controlling the grinding wheel which is part of the apparatus shown in Figure 1;
Figure 7 is a perspective view showing the workpiece holding apparatus partially shown in Figure 1; and Figure 8 is a vertical cross-section showing the relative position of the polishing apparatus in relation to the workpiece.
In the perspective drawing of Figure 1, the apparatus of the present invention is shown generally supported on a foundation 2 and having a first carriage 4 movable along a first horizontal axial direction by means of parallel tracks 6. The accordion pleated cover 8 covers a helical gear mechanism (although a system of cables and pulleys or rack and pinion could also be used) which under control of the central computer (not shown), is capable of positioning the polishing device with reference to defined coordinates along a first axis, which may be referred to as the X
axis.
Mounted on the first carriage 4 is a second carriage 10 designed to move along a second axial direction perpendicular to the first axis along similar tracks (not shown) covered by the accordion pleated cover 12. In a similar manner a helical gear mechanism (or equivalent device) moves under control of the computer to locate the second carriage 10 in relation to the coordinates of a second axis which maybe referred to as the "Y" axis..
The second carriage 10 supports a vertical track and gear mechanism 11 which is designed to support and move the tower 14 in a vertical direction in response to computer controls, so as to move the polishing apparatus in the vertical direction in relation to coordinates of a third axis "Z".
Thus, by means of computer controls, the tower 14 can move in any combination of the three-dimensional axes X, Y and Z and is capable of positioning the polishing mechanism, shown generally in Fig.6, in any selected position.
As can be seen more clearly in Figure 6, the column 14 has mounted thereon a dove-tailed guide 16 to which is mated a vertical arm 18 of the support 20, which also has a plate 15 extending outwardly from the column to support the mechanism of the polishing wheel described hereafter. The dove-tailed guide 16 and the mating arm 18 allow the support to move vertically under the influence of gravity and the opposing force of the cable 22 which passes over the pulleys 24 from the top of the arm 18 to the counterweight 26 which carries a series of weights 28 of various sizes.
In operation, the weights 28 are chosen so that the counterweight is slightly less than the weight of the polishing mechanism on the other end of the cable 22 and the difference in weight represents the amount of pressure which the polishing wheel will exert on the surface of the workpiece during the polishing operation to be described later.
On the horizontal portion 15 an electric motor 30 is positioned to drive the horizontal gear wheels 32 and 34 which in turn drive the worm gear 36 to rotate the axle 40 and the polishing wheel 38. The polishing surface of the polishing wheel is the periphery 42 which contacts the workpiece on the surface to be polished.
In addition, a second electric motor 44 drives a pair of gears 46 and 48 and causes the bracket 50 to revolve about a vertical axis (which coincides with the centre of the polishing wheel) so that the polishing wheel 38 supported on the bracket is constantly rotating in a different axial plane or direction relative to the workpiece surface, as illustrated in Figure 7.
Figure 7 also illustrates the means by which the workpiece is supported and positioned relative to the polishing wheel. In Figure 7 the workpiece 60 is shown resting on a bed 62 supported by a bridge 64. The bridge 64 is capable of rotation about a horizontal axis 66 which is positioned above the level of the workpiece at a distance which represents approximately the radius of curvature of the lens (in this case concave).
The bridge 64 and its pivot points 68 are supported by a platform 70 which is in turn supported at pivot points 72 so that the platform 70 is rotatable about a second horizontal axis 74 perpendicular to the other axis 66.
This gimbal arrangement allows the bed 62 of the workpiece to be oriented in a manner that presents the surface of the workpiece substantially perpendicular to the downward pressure of the polishing wheel 38 at which ever position on the surface is being polished.
In the illustrated embodiment the workpiece is concave and situated beneath the axes 66 and 74. However, it is also possible to position a workpiece with a convex surface by positioning it above the level of the axes so as to achieve a configuration in which the polishing wheel is directed normal to the surface during the polishing operation.
Figure 8 illustrates in vertical cross-section how the support 20 is movable in a vertical direction under the influence of the computer controlled tower 14 so that the computer causes the polishing wheel 38 to contact the surface for whichever configuration of the workpiece is selected during the grinding or polishing operation. The counterweight 26 will modify the weight of the polishing mechanism so as to determine the pressure to be applied by the polishing wheel to the surface.
Figure 8 also illustrates how the working surface 42 of the polishing wheel 38 rotates about its own horizontal axis while revolving about a vertical axis perpendicular to the rotational axis and substantially perpendicular to the peripheral surface of the polishing wheel.
It can also be seen that the working surface is substantially parallel to the curved surface 80 of the workpiece 60 so that the grinding and polishing effect is directed in a vertical direction which is substantially perpendicular to the surface of workpiece by virtue of the tilting of the workpiece on the bridge 64 about the axis 68.
What is not shown in Figure 8 is a comparable rotation of the platform 70 about the other axis of support 72, referred to and shown in Figure 7.
Rotation about both axes can achieve the appropriate orientation of the workpiece in any location of the polishing wheel on the surface.
It should also be understood that the rotation of the work piece about the axes 66 and 74 of the platform 70 and bridge 64 is controlled by computerized mechanism which coordinates with the computers controlling the location of the polishing wheel 38.
Therefore, for any given position on the surface of the workpiece, support is capable of positioning the workpiece in the correct orientation and the polishing mechanism is capable of positioning the polishing wheel in the correct location.
As previously mentioned, early lenses which were spherical and rotationally symmetrical could be polished by moving a polishing device designed to spin about an axis perpendicular to the working surface, and move it from side to side (or periphery to periphery), while the workpiece was being rotated about a vertical axis, or its axis of symmetry normal to the surface. This technique, however, does not apply to aspherical surfaces and does not apply to polishing techniques which are designed to improve the perfection of the surface of a lens by selectively removing surface irregularity such a high spots. In order to achieve the latter purpose it is necessary for the polishing device to dwell longer on those portions of the surface which have high spots and to spend less time on portions of the surface which are of low relief. In order to do this techniques have been developed to identify by optical means and computer data a profile of the surface of the lens to be treated.
Figure 3 illustrates a computer generated graphic illustration of the shape of the surface of a typical lens identifying high spots to be removed. Figure 3A shows a cross-section identifying a profile through a portion of a lens on which the surface is related to a common datum line or level.
In order to do the grinding or polishing necessary to remove these irregularities at specific locations, the wheel 38 must work on identifiable portions of the surface of the lens and must therefore move across the surface of the lens in a series of traverses, as illustrated in Figure 2, which are controlled by and identified to the computer and enable the computer program to relate the position of the grinding wheel relative to the location of the high spots on the surface of the lens.
The computer can, by appropriate programming, cause the polishing wheel to dwell longer on the high spots, travel more quickly across areas of low relief thereby achieve a more even surface closer to an ideal contour.
It will be recalled that the polishing wheel is capable of such movement by virtue of its support on the column 14 which is movable in the first and second axes by the first carriage 4 and second carriage 10. It will also be apparent from Figure 1 and Figure 8 that polishing mechanism is controlled in a vertical direction and the balance between the weight of the polishing mechanism and the counterweight 26 will establish the downward force applied to the polishing operation.
Figure 4 illustrates in simplified terms the location of the polishing wheel relative to the surface of the lens in a generally central location. It should be noted that the polishing surface 42 of the wheel 38 has a degree of curvature perpendicular to the plane of the wheel which is substantially similar to the radius of curvature of the wheel in the plane of rotation.
Figure 5 illustrates how the surface of the polishing wheel engages the surface of the lens when the lens is rotated about an axis remote from the axis of the wheel at a distance which is determined by the specification of the lens.
Although the arrow 43 represents the distance of the working surface of the workpiece from the axis 66 or 74, it should be remembered that the curvature of an asymmetrical lens changes from the centre to the periphery and therefore this does not represent a rotation of curvature for the entire lens.
With reference to Figure 2, it should be appreciated that it is undesirable that the polishing wheel travelling along one of the illustrated lines of traverse should create a furrow or groove relative to the direction of movement. For this reason, the present invention provides a polishing wheel which not only rotates but revolves so that the direction of rotation constantly changes and the wheel is always polishing in a different direction relative to the direction of movement across the surface of the lens. This is, of course, accomplished by means of the motor and gear mechanism which causes the bracket 50 to rotate. In this arrangement it is also advantageous that the optimum point of contact (or the point of convergence between the curvature of the wheel and curvature of the lens) is also a point at which there is substantial relative movement between the wheel and the lens surface so as to achieve the desired amount of grinding or polishing. This is not possible for a device which spins about its own axis perpendicular to the work surface.
Thus, by means of the illustrated apparatus and the method described above, it is possible to grind and/or polish aspherical lenses and to achieve a high degree of precision in the surface thereof.
While the illustrated embodiment has been described in terms of horizontal and vertical relative directions, these may be altered to other orientations without changing the nature of the invention.
It will, of course, be realized that numerous modifications and variations of the illustrated embodiments and methods described herein may be employed without departing from the inventive concept herein.
This invention relates to an improved method and apparatus forfinishing the curved surface of lenses. In this context a lens refers to either a transparent or a reflective curved surface. In particular, it is intended to produce a more even accurate curved surface, especially for aspherical lenses, without the disadvantages of the previous techniques.
The apparatus and techniques described herein are applicable to either grinding or polishing, but especially the latter, and references to polishing should be taken to include both.
The development of modern lenses requires not merely the grinding and polishing of a concave or convex spherical surface but the more difficult accomplishment of providing extremely even surfaces for quality of light transmission and clarity of images, as well as the development of aspherical surfaces which are not of constant radius.
Although the term aspherical can refer to a curved surface with different radii of curvature in different axes or directions, it may also refer to a curved surface in which the radius of curvature varies from the centre to the periphery and it is this latter concept to which the present invention is chiefly directed, although it may be applied to both cases.
Whereas spherical surfaces may be generated by rotating a grinding or polishing wheel which is moved about a fixed point or axis at a constant radius, aspherical surfaces require more complex movement of the grinding or polishing instrument with changing arcs of curvature.
To accomplish this, polishing devices have been developed which move under computerized control according to a three-dimensional grid defined by coordinates in relation to three-dimensions such as an X, Y, and Z axes. This sort of apparatus allows the polishing device to be selectively controlled so that it can grind or polish the curved surface selectively and remove more material where there are high spots and less where there are areas of lower relief. One traditional method of polishing of lens involved spinning a cylindrical shaped polishing tool with a circumferential ring about a central axis while the central axis is caused to swing in a spherical arc about a fixed point. At the same time the workpiece was rotated about an axis coinciding to its axis of symmetry. This technique, however, does not work for aspherical lenses where the radius of curvature is constantly changing. It also does not work for the high quality technique which requires material to be ground or polished from the lens differentially at selective locations.
There also remains the problem of applying the polishing device to the surface in a manner which is substantially parallel to the surface at the point of contact.
In conducting the polishing operation, it is also important that the polishing device not be applied in a unique directional manner so as to create a pattern of rows or furrows corresponding to the direction of travel of the polishing device.
It is therefore the purpose of this invention to provide apparatus and a method for grinding and/or polishing lenses which will overcome the problems associated with aspherical lenses and at the same time to create a highly precise and even curved surface.
These objects and other advantages are sought to be achieved by means of the present invention which comprises a polishing machine having a first carriage movable in a substantially horizontal direction and a second carriage mounted on said first carriage and movable in a second substantially horizontal direction perpendicular to said first direction and a third carriage mounted on said second carriage and movable in a third direction substantially perpendicular to said first two directions. A polishing mechanism is mounted on the third carriage and consists of a polishing wheel having a polishing surface on its periphery and motor means to rotate the wheel about its axis symmetry and a second motor means designed to revolve the wheel about an axis perpendicular to its axis of symmetry so that the wheel will spin and rotate at the same time. The carriages are controlled by a computer programmed to locate the polishing means in any three dimensional position relative to the three coordinates of movement of the carriages so that the polishing wheel may be moved about or located at any desirable position on a work piece.
The machine is provided with a work piece positioning means which is adapted to locate and orient a work piece relative to the polishing wheel.
Preferably this positioning means is rotatable about at least one and preferably two perpendicular axes and is controlled by a computer so that the curved surface of a work piece such as a tense may be presented to the polishing wheel in such a way that the polishing wheel bears against the surface in a direction substantially normal to the surface at the position of contact.
Thus the polishing wheel may be located anywhere along three directions of movement and the polishing wheel will spin perpendicular to its axis of symmetry and rotate in a plane parallel to its axis of symmetry so that the direction of movement of the polishing wheel against the work piece surface is constantly changing.
Thus the polishing wheel may move in a series of traverses across the surface of the work piece, in response to the computer programme, and the direction of the polishing movement will be constantly changing so as to avoid creating furrows or patterns corresponding to the travel of the wheel.
The invention may be better understood by a detailed description of one embodiment thereof with reference to the attached drawings in which:
Figure 1 is a perspective view of one embodiment of the present invention;
Figure 2 illustrates a typical example of a lens of circular shape having a concave cross-section with the path of the polishing apparatus illustrated in broken lines;
Figure 3 is a computer generated graphic display of the irregularities on the surface of a lens;
Figure 3A is a computer generated graphic display of a cross-section of the surface of a lens relative to a datum.
Figure 4 illustrates the position of the polishing wheel of the present invention at the centre of a lens;
Figure 5 illustrates the relative position of the polishing wheel near the periphery of the lens;
Figure 6 illustrates the details of the movement controlling the grinding wheel which is part of the apparatus shown in Figure 1;
Figure 7 is a perspective view showing the workpiece holding apparatus partially shown in Figure 1; and Figure 8 is a vertical cross-section showing the relative position of the polishing apparatus in relation to the workpiece.
In the perspective drawing of Figure 1, the apparatus of the present invention is shown generally supported on a foundation 2 and having a first carriage 4 movable along a first horizontal axial direction by means of parallel tracks 6. The accordion pleated cover 8 covers a helical gear mechanism (although a system of cables and pulleys or rack and pinion could also be used) which under control of the central computer (not shown), is capable of positioning the polishing device with reference to defined coordinates along a first axis, which may be referred to as the X
axis.
Mounted on the first carriage 4 is a second carriage 10 designed to move along a second axial direction perpendicular to the first axis along similar tracks (not shown) covered by the accordion pleated cover 12. In a similar manner a helical gear mechanism (or equivalent device) moves under control of the computer to locate the second carriage 10 in relation to the coordinates of a second axis which maybe referred to as the "Y" axis..
The second carriage 10 supports a vertical track and gear mechanism 11 which is designed to support and move the tower 14 in a vertical direction in response to computer controls, so as to move the polishing apparatus in the vertical direction in relation to coordinates of a third axis "Z".
Thus, by means of computer controls, the tower 14 can move in any combination of the three-dimensional axes X, Y and Z and is capable of positioning the polishing mechanism, shown generally in Fig.6, in any selected position.
As can be seen more clearly in Figure 6, the column 14 has mounted thereon a dove-tailed guide 16 to which is mated a vertical arm 18 of the support 20, which also has a plate 15 extending outwardly from the column to support the mechanism of the polishing wheel described hereafter. The dove-tailed guide 16 and the mating arm 18 allow the support to move vertically under the influence of gravity and the opposing force of the cable 22 which passes over the pulleys 24 from the top of the arm 18 to the counterweight 26 which carries a series of weights 28 of various sizes.
In operation, the weights 28 are chosen so that the counterweight is slightly less than the weight of the polishing mechanism on the other end of the cable 22 and the difference in weight represents the amount of pressure which the polishing wheel will exert on the surface of the workpiece during the polishing operation to be described later.
On the horizontal portion 15 an electric motor 30 is positioned to drive the horizontal gear wheels 32 and 34 which in turn drive the worm gear 36 to rotate the axle 40 and the polishing wheel 38. The polishing surface of the polishing wheel is the periphery 42 which contacts the workpiece on the surface to be polished.
In addition, a second electric motor 44 drives a pair of gears 46 and 48 and causes the bracket 50 to revolve about a vertical axis (which coincides with the centre of the polishing wheel) so that the polishing wheel 38 supported on the bracket is constantly rotating in a different axial plane or direction relative to the workpiece surface, as illustrated in Figure 7.
Figure 7 also illustrates the means by which the workpiece is supported and positioned relative to the polishing wheel. In Figure 7 the workpiece 60 is shown resting on a bed 62 supported by a bridge 64. The bridge 64 is capable of rotation about a horizontal axis 66 which is positioned above the level of the workpiece at a distance which represents approximately the radius of curvature of the lens (in this case concave).
The bridge 64 and its pivot points 68 are supported by a platform 70 which is in turn supported at pivot points 72 so that the platform 70 is rotatable about a second horizontal axis 74 perpendicular to the other axis 66.
This gimbal arrangement allows the bed 62 of the workpiece to be oriented in a manner that presents the surface of the workpiece substantially perpendicular to the downward pressure of the polishing wheel 38 at which ever position on the surface is being polished.
In the illustrated embodiment the workpiece is concave and situated beneath the axes 66 and 74. However, it is also possible to position a workpiece with a convex surface by positioning it above the level of the axes so as to achieve a configuration in which the polishing wheel is directed normal to the surface during the polishing operation.
Figure 8 illustrates in vertical cross-section how the support 20 is movable in a vertical direction under the influence of the computer controlled tower 14 so that the computer causes the polishing wheel 38 to contact the surface for whichever configuration of the workpiece is selected during the grinding or polishing operation. The counterweight 26 will modify the weight of the polishing mechanism so as to determine the pressure to be applied by the polishing wheel to the surface.
Figure 8 also illustrates how the working surface 42 of the polishing wheel 38 rotates about its own horizontal axis while revolving about a vertical axis perpendicular to the rotational axis and substantially perpendicular to the peripheral surface of the polishing wheel.
It can also be seen that the working surface is substantially parallel to the curved surface 80 of the workpiece 60 so that the grinding and polishing effect is directed in a vertical direction which is substantially perpendicular to the surface of workpiece by virtue of the tilting of the workpiece on the bridge 64 about the axis 68.
What is not shown in Figure 8 is a comparable rotation of the platform 70 about the other axis of support 72, referred to and shown in Figure 7.
Rotation about both axes can achieve the appropriate orientation of the workpiece in any location of the polishing wheel on the surface.
It should also be understood that the rotation of the work piece about the axes 66 and 74 of the platform 70 and bridge 64 is controlled by computerized mechanism which coordinates with the computers controlling the location of the polishing wheel 38.
Therefore, for any given position on the surface of the workpiece, support is capable of positioning the workpiece in the correct orientation and the polishing mechanism is capable of positioning the polishing wheel in the correct location.
As previously mentioned, early lenses which were spherical and rotationally symmetrical could be polished by moving a polishing device designed to spin about an axis perpendicular to the working surface, and move it from side to side (or periphery to periphery), while the workpiece was being rotated about a vertical axis, or its axis of symmetry normal to the surface. This technique, however, does not apply to aspherical surfaces and does not apply to polishing techniques which are designed to improve the perfection of the surface of a lens by selectively removing surface irregularity such a high spots. In order to achieve the latter purpose it is necessary for the polishing device to dwell longer on those portions of the surface which have high spots and to spend less time on portions of the surface which are of low relief. In order to do this techniques have been developed to identify by optical means and computer data a profile of the surface of the lens to be treated.
Figure 3 illustrates a computer generated graphic illustration of the shape of the surface of a typical lens identifying high spots to be removed. Figure 3A shows a cross-section identifying a profile through a portion of a lens on which the surface is related to a common datum line or level.
In order to do the grinding or polishing necessary to remove these irregularities at specific locations, the wheel 38 must work on identifiable portions of the surface of the lens and must therefore move across the surface of the lens in a series of traverses, as illustrated in Figure 2, which are controlled by and identified to the computer and enable the computer program to relate the position of the grinding wheel relative to the location of the high spots on the surface of the lens.
The computer can, by appropriate programming, cause the polishing wheel to dwell longer on the high spots, travel more quickly across areas of low relief thereby achieve a more even surface closer to an ideal contour.
It will be recalled that the polishing wheel is capable of such movement by virtue of its support on the column 14 which is movable in the first and second axes by the first carriage 4 and second carriage 10. It will also be apparent from Figure 1 and Figure 8 that polishing mechanism is controlled in a vertical direction and the balance between the weight of the polishing mechanism and the counterweight 26 will establish the downward force applied to the polishing operation.
Figure 4 illustrates in simplified terms the location of the polishing wheel relative to the surface of the lens in a generally central location. It should be noted that the polishing surface 42 of the wheel 38 has a degree of curvature perpendicular to the plane of the wheel which is substantially similar to the radius of curvature of the wheel in the plane of rotation.
Figure 5 illustrates how the surface of the polishing wheel engages the surface of the lens when the lens is rotated about an axis remote from the axis of the wheel at a distance which is determined by the specification of the lens.
Although the arrow 43 represents the distance of the working surface of the workpiece from the axis 66 or 74, it should be remembered that the curvature of an asymmetrical lens changes from the centre to the periphery and therefore this does not represent a rotation of curvature for the entire lens.
With reference to Figure 2, it should be appreciated that it is undesirable that the polishing wheel travelling along one of the illustrated lines of traverse should create a furrow or groove relative to the direction of movement. For this reason, the present invention provides a polishing wheel which not only rotates but revolves so that the direction of rotation constantly changes and the wheel is always polishing in a different direction relative to the direction of movement across the surface of the lens. This is, of course, accomplished by means of the motor and gear mechanism which causes the bracket 50 to rotate. In this arrangement it is also advantageous that the optimum point of contact (or the point of convergence between the curvature of the wheel and curvature of the lens) is also a point at which there is substantial relative movement between the wheel and the lens surface so as to achieve the desired amount of grinding or polishing. This is not possible for a device which spins about its own axis perpendicular to the work surface.
Thus, by means of the illustrated apparatus and the method described above, it is possible to grind and/or polish aspherical lenses and to achieve a high degree of precision in the surface thereof.
While the illustrated embodiment has been described in terms of horizontal and vertical relative directions, these may be altered to other orientations without changing the nature of the invention.
It will, of course, be realized that numerous modifications and variations of the illustrated embodiments and methods described herein may be employed without departing from the inventive concept herein.
Claims (3)
1. A polishing machine comprising:
- a first carriage movable in a first substantially horizontal direction;
- a second carriage mounted on said first carriage and movable in a second substantially horizontal direction perpendicular to said first direction;
- a third carriage mounted on said second carriage and movable in a third direction substantially perpendicular to said first two direction;
- computer means programmed to move at least two of said carriages in said directions;
- polishing means mounted on said third carriage, said polishing means comprising;
- a polishing wheel having a polishing surface on the periphery thereof and an axle corresponding to the axis of symmetry of said wheel;
- motor means to rotate said wheel about said axle axis;
- motor means to revolve said polishing wheel about an axis perpendicular to said axle axis;
- work piece positioning means adapted to locate a work piece relative to said polishing wheel.
- a first carriage movable in a first substantially horizontal direction;
- a second carriage mounted on said first carriage and movable in a second substantially horizontal direction perpendicular to said first direction;
- a third carriage mounted on said second carriage and movable in a third direction substantially perpendicular to said first two direction;
- computer means programmed to move at least two of said carriages in said directions;
- polishing means mounted on said third carriage, said polishing means comprising;
- a polishing wheel having a polishing surface on the periphery thereof and an axle corresponding to the axis of symmetry of said wheel;
- motor means to rotate said wheel about said axle axis;
- motor means to revolve said polishing wheel about an axis perpendicular to said axle axis;
- work piece positioning means adapted to locate a work piece relative to said polishing wheel.
2. A polishing machine as claimed in claim 1 in which said work piece positioning means is rotatable about at least one axis substantially perpendicular to the direction of movement of said third carriage.
3. A polishing machine as claimed in claim 2 including computer means programmed to rotate said work piece positioning means in a manner to present said work piece to said polishing wheel in a selected orientation.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2356497 CA2356497A1 (en) | 2001-08-30 | 2001-08-30 | Multi-axis polishing machine |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2356497 CA2356497A1 (en) | 2001-08-30 | 2001-08-30 | Multi-axis polishing machine |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2356497A1 true CA2356497A1 (en) | 2003-02-28 |
Family
ID=4169869
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2356497 Abandoned CA2356497A1 (en) | 2001-08-30 | 2001-08-30 | Multi-axis polishing machine |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2356497A1 (en) |
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2860448A1 (en) * | 2003-10-07 | 2005-04-08 | Absalon | Machine tool for part manufacture, has work-holder rotated around vertical axis by driving unit arranged in bed rotated along horizontal axis, and machining system with grinding wheel and barrel structure moving along three axes |
| WO2007147958A2 (en) * | 2006-06-22 | 2007-12-27 | Essilor International (Compagnie Generale D'optique) | Method and machine tool for machining an optical object |
| CN102785156A (en) * | 2011-05-16 | 2012-11-21 | 天津市宝通散热器有限公司 | Polishing machine of radiator |
| EP2837464A1 (en) * | 2013-08-13 | 2015-02-18 | Optotech Optikmaschinen GmbH | Polishing method for processing an optical surface of an optical lens and polishing tools suitable for the same |
| CN106670924A (en) * | 2016-11-09 | 2017-05-17 | 芜湖市恒浩机械制造有限公司 | Grinding device |
| CN107553301A (en) * | 2017-10-25 | 2018-01-09 | 德清创智热喷涂科技有限公司 | A kind of yarn storage disk burnishing device |
| CN107571126A (en) * | 2017-09-26 | 2018-01-12 | 德清县檀香斋木业有限公司 | A kind of wood tool sanding and polishing all-in-one |
| CN108340265A (en) * | 2017-10-25 | 2018-07-31 | 德清创智热喷涂科技有限公司 | A kind of polishing mechanism for yarn storage disk |
| CN110948549A (en) * | 2019-11-20 | 2020-04-03 | 湖南欧威爱特新材料科技有限公司 | Filter core rubber head cutting device |
| CN112894539A (en) * | 2021-01-29 | 2021-06-04 | 四川恒格光电科技有限公司 | Lens processing device |
| CN116572120A (en) * | 2023-07-12 | 2023-08-11 | 晋宁腾锐光学仪器工贸有限公司 | Automatic centre gripping formula optical glass grinding device |
-
2001
- 2001-08-30 CA CA 2356497 patent/CA2356497A1/en not_active Abandoned
Cited By (19)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2860448A1 (en) * | 2003-10-07 | 2005-04-08 | Absalon | Machine tool for part manufacture, has work-holder rotated around vertical axis by driving unit arranged in bed rotated along horizontal axis, and machining system with grinding wheel and barrel structure moving along three axes |
| EP1522378A1 (en) * | 2003-10-07 | 2005-04-13 | Société à Responsabilité Limitée Absalon | Five axis machine tool with continuous grinding wheel dressing device |
| WO2007147958A2 (en) * | 2006-06-22 | 2007-12-27 | Essilor International (Compagnie Generale D'optique) | Method and machine tool for machining an optical object |
| FR2902683A1 (en) * | 2006-06-22 | 2007-12-28 | Essilor Int | PROCESS AND MACHINING MACHINE FOR OPTICAL OBJECT |
| WO2007147958A3 (en) * | 2006-06-22 | 2008-01-31 | Essilor Int | Method and machine tool for machining an optical object |
| US8118642B2 (en) | 2006-06-22 | 2012-02-21 | Essilor International | Method and machine tool for machining an optical object |
| AU2007262926B2 (en) * | 2006-06-22 | 2013-02-14 | Essilor International | Method and machine tool for machining an optical object |
| CN102785156A (en) * | 2011-05-16 | 2012-11-21 | 天津市宝通散热器有限公司 | Polishing machine of radiator |
| EP2837464A1 (en) * | 2013-08-13 | 2015-02-18 | Optotech Optikmaschinen GmbH | Polishing method for processing an optical surface of an optical lens and polishing tools suitable for the same |
| CN106670924A (en) * | 2016-11-09 | 2017-05-17 | 芜湖市恒浩机械制造有限公司 | Grinding device |
| CN106670924B (en) * | 2016-11-09 | 2018-08-17 | 芜湖市恒浩机械制造有限公司 | A kind of grinding attachment |
| CN107571126A (en) * | 2017-09-26 | 2018-01-12 | 德清县檀香斋木业有限公司 | A kind of wood tool sanding and polishing all-in-one |
| CN107553301A (en) * | 2017-10-25 | 2018-01-09 | 德清创智热喷涂科技有限公司 | A kind of yarn storage disk burnishing device |
| CN108340265A (en) * | 2017-10-25 | 2018-07-31 | 德清创智热喷涂科技有限公司 | A kind of polishing mechanism for yarn storage disk |
| CN108340265B (en) * | 2017-10-25 | 2023-12-08 | 德清创智科技股份有限公司 | Polishing mechanism for yarn storage disc |
| CN110948549A (en) * | 2019-11-20 | 2020-04-03 | 湖南欧威爱特新材料科技有限公司 | Filter core rubber head cutting device |
| CN112894539A (en) * | 2021-01-29 | 2021-06-04 | 四川恒格光电科技有限公司 | Lens processing device |
| CN116572120A (en) * | 2023-07-12 | 2023-08-11 | 晋宁腾锐光学仪器工贸有限公司 | Automatic centre gripping formula optical glass grinding device |
| CN116572120B (en) * | 2023-07-12 | 2023-09-15 | 晋宁腾锐光学仪器工贸有限公司 | Automatic centre gripping formula optical glass grinding device |
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