Classifications

• • 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
  • B24B51/00—Arrangements for automatic control of a series of individual steps in grinding a workpiece
• • 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
  • B24B49/00—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation

Definitions

• the invention relates to a method for grinding and polishing free-form surfaces, in particular rotationally symmetrical aspherical optical lenses.
• these aspherical lenses have special optical properties that theoretically represent the physical optimum. In practice, this means that the images realized with these aspherical lenses are much brighter and sharper. You avoid errors like spherical aberration.
• the object of the invention is to avoid these disadvantages.
• rotationally symmetrical free-form surfaces In contrast to any free-form surfaces, rotationally symmetrical free-form surfaces have a regular shape in the form of their rotational symmetry. It is irrelevant how the lens is rotated within its axis of symmetry, the cross-section of the surface shape as for example in Fig. 4 surface (1) remains the same. If the same surfaces are processed using methods that utilize the rotational symmetry (see also FIG. 4), the surface defects are also distributed rotationally symmetrically. Then it is possible to control the removal only radially. To control such processing, the method presented is converted into a one-dimensional form. The virtual removal and the distribution of the areas is limited to the one-dimensional, radial area (see FIG. 5). The machining then takes place with the rotation of the tool and workpiece.
• overlapping areas are also permitted.
• the areas B1, B2, B3 ... B9 shown in FIG. 10 overlap in pairs by 50%. For example, B3 overlaps half with B4 and half overlaps with B5. There are 16 common support points or calculation points.
• this process enables the use of tools (2) with diameters from one eighth to one quarter of the diameter of the workpiece (Fig. 11) and is still able to correct the surface (1) (see also in embodiment).
• tools (2) with diameters from one eighth to one quarter of the diameter of the workpiece (Fig. 11) and is still able to correct the surface (1) (see also in embodiment).
• the use of these tools alone enables a more than six-fold increase in removal and a corresponding reduction in processing time.
• the existing errors (7 in FIG. 12), which must be removed in order to achieve the required accuracy, are decisive for the use of tools. It is generally known that the tools used for correlating may only be as wide as the narrowest error, here 20 mm, which must be removed. With this method it is possible to use tools that are twice as wide or. have twice the diameter of 40 mm as the errors to be corrected. The errors are corrected as before, but in a quarter of the time, since the machining area quadruples with the tool, which is twice as wide as before.
• the polishing or grinding film (14 from FIG. 13), the material of the tool (2) coming into contact with the processing surface should have a homogeneous structure which is free from bubbles, cracks or the like.
• the composition of the material itself should also be macroscopically uniform.
• a reproducible removal is essentially achieved when the tools rest vertically on the surface.
• 16 illustrates an arrangement of several tools, all of which lie tangentially on the surface.
• machining the surface is also possible and useful if the tools are not moving.
• the tools are arranged in such a way that the entire free-form surface is machined, which is the case in the example from FIG. 14.
• each of the individual tools is controlled separately.
• it is easier, especially if the handling system of the tools for several lenses is to be universal, if each of the tools has a movable foot that meets the condition that the tool lies tangentially on the free surface even if it is not entirely correct Delivery guaranteed.
• the individual tools can be mechanically bundled in a rod-shaped composite (18).
• Round composites (17) are also an option for combining individual tools (2). In terms of the tangential support of the tool, they are particularly advantageous on a round, rotationally symmetrical free-form surface (1).
• the exemplary embodiment relates to an aspherical optical lens that is to be corrected.
• the lens is measured interferometrically.
• FIG. 3 shows the error distribution measured before processing. Since the previous polishing out of the lens, as can be seen very well in FIG. 3, already took place in a rotationally symmetrical manner, the errors present on the surface are distributed rotationally symmetrically. In the meantime, both the lens and the tool rotate, the tool travels radially from the edge of the lens with a vertical orientation to its surface to the center of the lens (FIG. 4). The correction of the errors should be controlled along this path by the dwell time. In contrast to general free-form surfaces, the entire error analysis for the correction of this lens is limited to the radial distance. A somewhat descriptive example is chosen here to simplify the illustration. The application of the method to general free-form surfaces means only a transformation in two dimensions, i.e. the use of a surface instead of only one (radial) path.
• the error of the entire measured area is first averaged over the radial average. 5 shows the result in curve 7.
• the entire method works on 130 support points, on which calculations are made. The virtual removal is known for each position. Building on this, a dwell time is generated and used to control the removal during processing. Each of these interpolation points was generated with measured values from FIG. 3. In this example, these 130 support points correspond to a distance of 20 mm.
• the virtual removal of the tool is calculated on the basis of footprints for the entire surface.
• the tool has a width of 33 points, about 5 mm.
• the areas should have the width of the tool.
• a system of equations is now set up and solved for each of these areas, which reduces the error of the surface in this area by the influence of the adjacent areas estimated for the zero approximation (for Bl: B2 / for B2: Bl, B3 / for B3: B2, B4 / and for B4: B3) and the virtual removal at each of the 33 positions belonging to the area.
• the example shows that the method is able to correct difficult surface defects in an extremely short time when using large tools.
• the large tool diameter ratio tool: workpiece / 1: 8
• the ability of the process to remove just enough to reduce only the actually existing error plays a significant part in the shortening of the production time.
• FIG. 6 shows a curve 13 which illustrates how much removal is removed in such cases. In this case, the processing time would increase to 20 minutes. It is also crucial that this result was achieved in one processing step without repeated measuring and reworking.
• Fig. 1 division of a round free-form surface (1) in areas (3) when using the
• Fig. 2 Division of a rectangular free-form surface (4) into areas (3) which are delimited by the area boundaries (5) and correspond to the size of the tool (2) (top view on the free-form surface)
• Fig. 3 Two-dimensional error distribution (6) of a rotationally symmetrical optical
• FIG. 5 Radial average of the error distribution (7) on the rotationally symmetrical optical lens from FIG. 4; this corresponds to the minimum necessary removal 6: shifted radial average of the error distribution (13) on the rotationally symmetrical optical lens from FIG. 4; This corresponds to the removal that has often been carried out to date
• Fig. 7 Illustration of the method with the actual state of the surface defect (7), the forecast removal (sum of 8 and 9) and the forecast remaining error after processing (10) Residence times determined by the method (11)
• Fig. 9 The remaining on the surface processed with these residence times (11)
• Fig. 10 Exemplary distribution of 50% overlapping areas (Bl, ..., B9) within a radial average of a rotationally symmetrical surface
• Fig. 11 Size relationships between tool and workpiece 1: 8 and 1: 4
• Fig. 12 Size comparison between the narrowest error in the error distribution () and the
• Tool (2) Fig. 13 Tool with adapted polishing or grinding film (14) with vertical edges (15)
• Fig. 14 Arrangement of several tools (2) on the round free-form surface (1)
• Fig. 15 Arrangement of several tools (2) on the rectangular free-form surface (4)
• Fig. 16 Arrangement of several tools (2) that are tangential Lie on the freeform surface (1) with a vertical orientation.
• Fig. 17 Arrangement of round mechanical assemblies (17) of tools (2) on a round free-form surface (1)
• Fig. 18 Arrangement of rod-shaped mechanical assemblies (18) of tools (2) on a rectangular free-form surface (4)

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)

Applications Claiming Priority (3)

Publications (2)

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Family Applications (1)

Country Status (6)

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Family Cites Families (5)

• 2002
  • 2002-02-21 DE DE10207379A patent/DE10207379A1/de not_active Withdrawn
• 2003
  • 2003-02-20 WO PCT/EP2003/001749 patent/WO2003070427A2/fr not_active Ceased
  • 2003-02-20 AT AT03742562T patent/ATE343454T1/de not_active IP Right Cessation
  • 2003-02-20 DE DE50305484T patent/DE50305484D1/de not_active Expired - Lifetime
  • 2003-02-20 US US10/505,195 patent/US20050215175A1/en not_active Abandoned
  • 2003-02-20 AU AU2003215573A patent/AU2003215573A1/en not_active Abandoned
  • 2003-02-20 EP EP03742562A patent/EP1478490B1/fr not_active Expired - Lifetime

Non-Patent Citations (1)

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