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
  • B23Q1/25—Movable or adjustable work or tool supports
  • B23Q1/44—Movable or adjustable work or tool supports using particular mechanisms
  • B23Q1/50—Movable or adjustable work or tool supports using particular mechanisms with rotating pairs only, the rotating pairs being the first two elements of the mechanism
  • B23Q1/54—Movable or adjustable work or tool supports using particular mechanisms with rotating pairs only, the rotating pairs being the first two elements of the mechanism two rotating pairs only
  • B23Q1/5468—Movable or adjustable work or tool supports using particular mechanisms with rotating pairs only, the rotating pairs being the first two elements of the mechanism two rotating pairs only a single rotating pair followed parallelly by a single rotating pair
  • B23Q1/5481—Movable or adjustable work or tool supports using particular mechanisms with rotating pairs only, the rotating pairs being the first two elements of the mechanism two rotating pairs only a single rotating pair followed parallelly by a single rotating pair followed parallelly by a single rotating pair
• • 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

Definitions

• the invention relates to a method and a device for polishing an optical component.
• the conventional technique for manufacturing optical components of the lens or mirror type comprises successive roughing, smoothing and polishing operations.
• the blank is produced by machining, using a bell-shaped diamond tool.
• the smoothing and polishing are carried out using a polisher and an abrasive. Smoothing is a relatively easy and quick roughing operation, but polishing is a very long, expensive operation and on which all the optical quality of the component depends.
• polishing is characterized both by the rusticity and the age of the machines used, and by the subtlety of the artisanal know-how of the specialized personnel in charge of this operation.
• Traditional polishing machines essentially comprise a lathe with a vertical axis of rotation, on which the component to be polished is fixed, a polisher in contact with the polishing surface of the component, this polisher being supported in its center by a ball joint and driven in movement. orbital with a bearing force on the surface to be polished, and mechanical means with rod and crank for positioning the polisher and generating its movement.
• the polishing process consists of interposing a powdered abrasive, of determined particle size, and a wetting liquid between the polisher and the component to be polished.
• the abrasive supply, the type of polisher, its diameter, its pressing pressure, the position, amplitude and speed adjustments of its orbital movements, as well as the rotation of the lathe constitute the polishing parameters. It is necessary to proceed with all the more caution since one does not precisely control the location and the amplitu ⁇ of polishing operations. We therefore proceed, during polishing, to an alternation of very limited control and material removal operations. Indeed, excessive removal of material at a particular point, with overshoot of the dimension towards which the successive polishing operations converged, requires a recovery of the entire surface of the optical component. This risk is permanent and, whenever it occurs, it a significant increase in cost.
• polishing a mirror with a diameter of 600 mm requires approximately 400 hours of machine and 150 hours of specialized personnel.
• finishing period which lasts 10 to 15 days
• two to three checks of the surface finish of the component are necessary each day. It takes about 40 successive polishing operations to pass the amplitude of the surface defects from 5 microns to 1/8 of the wavelength.
• the subject of the invention is in particular a method and a device for polishing optical components, which meet these needs.
• the invention therefore provides a method of polishing an optical component, by means of a polisher mounted on a support for guiding and generating movement, characterized in that it consists in transferring to the side of the polisher and its support the parameters defining elementary polishing operations and quantifying them, making the polisher and its support insensitive to disturbing reactions appearing at the polisher-surface interface of the component, giving said parameters values or successive groups of values which correspond respectively to one or more polishing pads of the component and which are obtained by comparison of the desired final surface of the component and a precise statement of its surface defects, to execute the elementary polishing operation (s) defined by these values of parameters, then to make a precise statement of the surface defects of the component and to deduce new values polishing parameters.
• the ill-defined interaction between the polisher and the surface of the optical component which was encountered in the prior art, is replaced by a precise and well controlled action of the polisher on the surface of the optical component, thanks to the transfer on the side of the tool of the polishing parameters and to the insensitivity of the tool to the reactions of its interface with the optical component.
• the method according to the invention is further characterized in that it consists in giving the parameters values allowing, within a determined polishing range and by an elementary polishing operation, to remove at least 50% of the amplitude of the defects of surface to be treated.
• the efficiency of elementary polishing operations can reach a value of 70 to 80%, which makes it possible to obtain, after three or four elementary polishing operations, the same result and the same precision of surface condition as after 40 polishing operations according to the prior art.
• the invention makes it possible to divide by a factor of the order of ten the number of finishing operations, and therefore the number of control operations.
• the method also consists in uniformly distributing the action of the polisher on the optical component in their contact area, and in preserving this uniform distribution during movements and displacements of the polisher on said surface.
• the invention provides for creating a virtual center of rotation of the polisher on its support at a point substantially coincident with the point of application of the result of the friction forces between the polisher and the component surface in their contact area. In this way, the movements and displacements of the polisher on the surface of the component cannot harm the uniformity of action of the polisher on the optical component.
• the method also consists in polishing the surface of the component range by range, by modifying from one range to another the values of at least some of the polishing parameters, said ranges being for example spherical caps of indifferent axis, spherical zones, or any other spherical surface fractions. Controlling the polishing parameters makes it possible to vary their values from one range to another of the surface to be polished, to obtain the desired result more quickly.
• the method also consists in slaving the component in rotation around this axis, to position it or drive it in continuous, discontinuous or variable speed rotation, slow down, reverse or stop the rotation of the component for polishing a surface area, or resume this rotation to move the polisher from this beach to another.
• it is of course possible to drive the component in continuous rotation about its axis of revolution, for the polishing of a zone in sphere segment.
• the invention also provides a device for polishing an optical component, comprising a polisher and a support for guiding and generating movement of the polisher on the surface of the component, characterized in that it comprises means for mounting the pusher on its support for rotation about a point which substantially coincides with the point of application of the resultant of the tangential forces of friction between the moving polisher and the surface of the component in their contact area.
• the device comprises pneumatic means for controlling and adjusting the pressing pressure of the polisher on the surface of the component.
• these pneumatic means of control and adjustment constitute a means of pneumatic suspension of the polisher on its support, making it possible to absorb the vibrations of this support.
• the device comprises means for driving the polisher in rotation about its axis, means for moving the polisher in translation, for example circular around the axis of its support, and means for relative movement of the optical component relative to the polisher.
• the support of the polisher forms the last articulated element of a robot arm with three degrees of freedom controlled in position. More precisely, the support comprises a turntable to which the polisher is fixed by two pairs of bending blades arranged in cascade at 90 ° from one another, these blades defining at their intersections two axes of rotation of the polisher, which are perpendicular and intersect at a point forming the virtual center of rotation of the polisher.
• the plate is slidably mounted and free to rotate on a shaft coaxial with the polisher, and is connected to a motor means by the aforementioned means of pneumatic suspension and of adjustment of the pressing pressure of the polisher on the component.
• the turntable is supported by a frame guided in circular translation, so as to remain parallel to itself, about an axis parallel to the axis of the polisher, by means of a rod-crank system with eccentricity adjustable.
• FIG. 1 schematically shows a polishing device according to - the invention.
• FIG. 2 is a schematic view, on a larger scale, of the polisher support;
• FIG. 3 is a schematic sectional view, on a larger scale, of the lower part of this support
• Figure 4 is a schematic top view of the polisher support of Figure 2;
• FIG. 7 schematically illustrates the action of the polisher on the surface of an optical component.
• FIG. 8 shows schematically an embodiment of a robot arm.
• the polishing device according to the invention shown diagrammatically in FIG. 1 essentially comprises a robot arm 10 with three degrees of freedom controlled in position, carrying a polisher 12 displaced on the surface to be polished by an optical component 14 mounted on the plate d a lathe 16 with a vertical axis of rotation 18.
• the robot arm 10 comprises a vertical element 20 provided with means for vertical displacement of a horizontal element 22, horizontally displaceable in translation, and at the end of which a third element 24 for supporting the polisher 12 is mounted for rotation around a horizontal transverse axis 26.
• This third element 24 comprises (FIG. 2) a frame 28 rotatably mounted around the axis 26 of the second element 22 of the robot arm, and which in particular carries an electric motor 30 whose output shaft 32 is connected to a gear reducer 34 with hollow output shaft 36 which is vertical in Figure 2.
• This output shaft 36 is integral in rotation with two parallel crank arms 38, which are horizontal in Figure 2 and which carry a frame 40 with square or rectangular outline, arranged in a vertical plane in Figure 2.
• the frame 40 is mounted pivoting about a vertical median axis on the arms 38, by means of two suitable articulations 42 arranged in the middle of the horizontal sides of the frame 40.
• the reduction gear 34 which supports the arms 38 and the frame 40, is itself supported by the frame 28.
• the frame 40 is preferably guided in a circular translational movement around the axis 44 of the output shaft 36 of the reducer 34.
• the upper part of the frame 40 is connected by two articulated links 46 parallel and of the same length to a carriage 48 slidably mounted on a horizontal rail 50 carried by the chassis 28. From this in this way, the rotation of the arms 38 around the axis 44 of the output shafts of the reduction gear 34 is transformed into a circular translational movement of the frame 40 (which remains parallel to itself all the time), centered on the axis 44.
• each arm 38 contains a rack 52 (figure 3) which meshes with a toothed wheel 54 connected by a shaft 56 to the corresponding toothed wheel 54 of the other arm 38.
• the shaft 56 is coaxial with the shaft 36 of the reduction gear 34, this shaft 36 being tubular so that the shaft 56 connecting the two toothed wheels 54 can be accommodated there.
• Each rack 52 is integral in translation with a vertical shaft 58 of which a threaded end is screwed into a threaded hole of the rack 52, of which a threaded intermediate part receives a nut 60 for locking on the corresponding arm 38, and the end of which opposite is connected to the corresponding side of the frame 40 by means of a ball or roller stop 62 to form the above-mentioned joint 42.
• One of the racks 52 has a threaded orifice parallel to the direction of the corresponding arm 38 and in which is engaged an adjustment screw 64, accessible from one end of the arm 38. The rotation of the screw 64 in one direction or in the another makes it possible to move the corresponding rack 52 in one direction or the other with respect to the arm 38.
• This movement of the rack 52 results in a rotation of the toothed wheel 54, transmitted by the shaft 56 to the toothed wheel 54 associated with the rack 52 of the other arm 38.
• the lower horizontal side of the frame 40 is connected by a section of shaft 66 to a pulley 68 connected by a toothed belt 70 to the output shaft of a gear motor 72 carried by a vertical side of the frame 40 ( Figure 4).
• the pulley 68 which is supported by the shaft section 66 and which is mounted to rotate freely thereon by means of bearings 74 (FIG. 3) is made integral in rotation, by means of torque blades not shown, d 'A plate 76 guided in rotation and in translation, by means of a ball bushing 78, on the lower end of the shaft section 66.
• the plate 76 is also connected to the pulley 68 by means of air suspension with substantially constant stiffness. To this end, the pulley 68 and the plate 76 delimit between them a fluid chamber 80 connected to a source of pressurized gas via in particular a channel or through passage 82 of the shaft 66.
• the pulley 68 and the plate 76 comprise two coaxial cylindrical flanges 84, 86 respectively which are connected to each other by an annular membrane 88 elastically deformable, sealingly closing the chamber 80.
• the lower end of the shaft 66, housed in a well 90 of the plate 76, is provided with a proximity detector 92, detecting the position of the bottom 94 of the well 90, corresponding to the abutment of the plate 76 on the end of the shaft 66. This detector allows a height adjustment, for a mid-stroke operation.
• the movement of the plate 76 in the other direction in the vertical direction is limited by a stop 96 carried by the pulley 68.
• the plate 76 supports the polisher 12, by means of the means which will now be described, with reference to FIGS. 3, 5 and 6.
• These means comprise a horizontal beam 98 with a U-section facing downwards, and two pairs of bending blades 100, 106 which are cascaded, a pair of blades 100 connecting the plate 76 to the beam, the other pair of blades 106 connecting the beam to the polisher.
• a pair of blades 100 in Figure 5 there is shown a pair of blades 100 in Figure 5, and the other pair of blades 106 in Figure 6.
• the two bending blades 100 are opposite and symmetrical with respect to the axis of l 'shaft 66, and each is embedded at its ends on the plate 76 and on the lower end 102 of a vertical wall of the beam 98.
• the two blades 100 are oriented obliquely so that their extensions intersect along a line 104 which is perpendicular to the axis of the shaft 66 and which is located under the beam 98.
• This line 104 constitutes a first axis of rotation of the beam 98.
• the other two flexure blades 106 are secured at one end to the longitudinal ends of the horizontal wall of the beam 98 and extend symmetrically obliquely between the vertical walls of this beam, to be secured at their other end of the polisher 12.
• the extensions of these bending blades 106 intersect along a line 108 which is perpendicular to the axis of the shaft 66 and to the axis 104 of rotation of the beam 98.
• This line 108 constitutes a second axis of rotation of the polisher 12 relative to the beam 98.
• the heights and the inclinations of the beam 98 and of the bending blades 100 and 106 are designed such that the axes of rotation 104 and 108 are coplanar. They intersect at a point which constitutes a virtual center of rotation, equivalent to a universal joint, of the polisher 12 relative to the plate 76.
• This center of rotation designated by the reference 110 in FIG. 2, coincides with the point of application of the result of the friction forces of the polisher 12 on the surface to be polished of the optical component 14, as explained below with reference to FIG. 7.
• the polisher 12 applied on schematically the concave surface 112 to be polished of the optical component 14.
• the polisher 12 is of conventional constitution, that is to say that it comprises on the surface inférieu ⁇ re a machined plate with a curvature equal to that locally desired for the surface 112
• This lower plate is lined with a coating of a material allowing the retention of the abrasive and having a certain plasticity for adaptation to the surface to be polished.
• the friction forces between the polisher and the surface 112 are at all points tangential to the surface 112 and oriented in the opposite direction to that of the movement of the polisher 12 over the surface 112.
• the point 116 of application of their resultant is located on the vertical axis 114 of the polisher, below the surface 112, that is to say on the convex side of the interface and inside the optical component.
• the virtual center of rotation 110 of the polisher on its support coincides with this point 116.
• polishing according to the invention of an optical component is carried out as follows.
• the pneumatic suspension means of the plate 76 carrying the polisher 12 allow, by means of a pneumatic regulator and a asser ⁇ screwing system, to control the gas pressure in the chamber 80.
• a vacuum in this chamber allows d '' lighten or lift the polisher, to move it from one area to another of the surface to be polished.
• a pressure greater than atmospheric pressure in the chamber 80 increases the bearing force of the polisher on the surface to be polished.
• the mounting of the polisher on the plate 76 by means of a virtual center of rotation which coincides with the point of application of the result of the friction forces of the polisher on the surface to be polished, makes it possible to move the polisher on this surface by maintaining a uniform distribution of the action of the polisher on the surface of the optical component, this action being due to the bearing force of the polisher and to its movements on this surface.
• the pneumatic suspension of the plate 76 relative to the pulley 68 also has the advantage of not transmitting to the polisher the axial vibrations of the pulley.
• the three degrees of freedom of the elements of the robot arm make it possible to determine the area of the surface of the optical component which will be subjected to a polishing operation.
• the speed of rotation of the frame 40 around the axis 44 of the reduction gear 34, the value of the offset, the speed of rotation of the plate 76 around the axis of the pulley 68, the pressure of support of the polisher 12 on the surface of the optical component, the type of abrasive used, the rotation of the optical component 14 about its axis of revolution, and the duration constitute the other parameters of a polishing operation.
• the invention allows the surface of an optical component to be polished by proceeding track by track, without these areas necessarily being spherical areas.
• the use of the lathe 16 driving the optical component in rotation around its axis of revolution makes it possible to pass from one range to the other.
• continuous rotation of the lathe limits the work of the tool to polishing spherical areas or spherical caps.
• the invention also applies to the polishing of surfaces which are not surfaces of revolution.
• all the movements of the polisher and the robot arm, as well that the rotation of the optical component around its axis of revolution are controlled in position in order to avoid a harmonic coupling between the various movements and to guarantee that no point on the polisher will pass cyclically over the same points on the surface to be polished.
• the characteristics of a polishing device according to the invention can be the following:
• Rotary speed of the polisher around its axis about 2 revolutions per minute
• Offset of the circular translation movement of the frame 40 from 0 to 100 mm approximately
• Support force of the polisher on the surface of the component from 0 to a few tens of kg.
• Such a device allows, for example, the polishing of medium and large components (diameters ranging from 600 mm to approximately 2 m).
• the structure of the robot arm is for example that shown in FIG. 8.
• the three elements of the robot arm are pivotally mounted around horizontal axes and are part of deformable parallelograms.
• the first element 120 and the second element 122 of the robot arm are articulated one on the other about an axis 118 and form part of the same parallelogram 124 articulated at 126 on a fixed frame 128.
• the first element 120 is driven around the axis 126 by a motor 130.
• a third side 132 of the parallelogram, parallel to the element 122, is driven around the axis 126 by a motor 134 and rotates the element 122 around the axis 118.
• the third element of the robot arm which is the support 24 of the polisher 12, is articulated at 136 on the end of the second element 122, and is part of a parallelogram 138 connected by a triangle indéfor ⁇ mable 140 articulated at 118 and a parallelogram 142 articulated at 126, to a motor 144 mounted on the fixed frame, at the base of the robot arm.
• the combined rotations of the first element 120 around the axis 126 and the second element 122 around the axis 118 allow the end of the second element to be placed at any desired point in the plane of the drawing relative to the surface of a component to be polished.
• Support rotation 24 around the axis 136 determines the orientation of the axis of the polisher with respect to the surface to be polished.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Grinding And Polishing Of Tertiary Curved Surfaces And Surfaces With Complex Shapes (AREA)
• Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

Family

ID=9364997

Family Applications (1)

Country Status (11)

Cited By (2)

Families Citing this family (12)

Citations (4)

Family Cites Families (6)

• 1988
  • 1988-04-06 FR FR8804519A patent/FR2629746B1/fr not_active Expired - Lifetime
• 1989
  • 1989-03-30 IL IL89812A patent/IL89812A/xx not_active IP Right Cessation
  • 1989-04-05 JP JP1504148A patent/JPH02504492A/ja active Pending
  • 1989-04-05 WO PCT/FR1989/000154 patent/WO1989009680A1/fr not_active Ceased
  • 1989-04-05 DE DE8989400932T patent/DE68903661T2/de not_active Expired - Fee Related
  • 1989-04-05 ES ES198989400932T patent/ES2037438T3/es not_active Expired - Lifetime
  • 1989-04-05 AT AT89400932T patent/ATE82894T1/de active
  • 1989-04-05 US US07/458,732 patent/US5138798A/en not_active Expired - Fee Related
  • 1989-04-05 EP EP89400932A patent/EP0336838B1/fr not_active Expired - Lifetime
  • 1989-12-05 RU SU894742637A patent/RU1834787C/ru active
• 1993
  • 1993-02-24 GR GR930400380T patent/GR3007132T3/el unknown

Patent Citations (4)

Non-Patent Citations (4)

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