Method and device for the surface machining of workpieces composed of non-brittle materials in optical lens manufacturing and tool for this purpose

• US 20030043343A1
• Filed: 08/30/2002
• Published: 03/06/2003
• Est. Priority Date: 09/06/2001
• Status: Active Grant

• Current Assignee: Satisloh GmbH (EssilorLuxottica SA)
• Original Assignee: Loh Optikmaschinen AG
• Inventors: Lautz, Ronald, Tross, Karl-Heinz, Diehl, Joachim
• Granted Patent: US 6,991,525 B2
• Time in Patent Office: Days
• US Class Current: 351/177
• CPC Class Codes: B23B 2226/31 Diamond
• CPC Class Codes: B23C 2200/203 Curved cutting edges
• CPC Class Codes: B23C 2226/315 polycrystalline [PCD]
• CPC Class Codes: B23C 2226/61 Plastics not otherwise provided for, e.g. nylon
• CPC Class Codes: B23C 3/023 Milling spherical surfaces
• CPC Class Codes: B23C 5/006 Details of the milling cutter body
• CPC Class Codes: B23C 5/2273 having a special shape
• CPC Class Codes: B24B 13/01 Specific tools, e.g. bowl-like; Production, dressing or fastening of these tools
• CPC Class Codes: B24B 13/043 using cup-type grinding wheels
• CPC Class Codes: B24B 13/06 grinding of lenses, the tool or work being controlled by information-carrying means, e.g. patterns, punched tapes, magnetic tapes
• CPC Class Codes: B29D 11/00932 Combined cutting and grinding thereof
• CPC Class Codes: Y10T 407/1946 Face or end mill

Abstract

A device is disclosed for the surface machining of, among other things, plastic spectacle lenses, which has a work spindle, by means of which the spectacle lens can be driven with a controlled angle of rotation about an axis of work rotation, and a tool spindle, by means of which a tool can be driven to rotate about an axis of tool rotation, work and tool spindle being movable relative to one another with their positions controlled in two axes running at right angles. For rotational machining of the surface of the spectacle lens to be machined, the tool can also be swiveled by means of the tool spindle with a controlled angle of rotation about the axis of tool rotation, so that a rotational cutting edge provided on the tool can be brought into a defined rotational machining engagement with the surface of the spectacle lens to be machined as a function of the angle of rotation of the spectacle lens. Also included is a combined milling and rotational machining tool and a combined milling and rotational machining method. As a result, high cutting rates and very good surface qualities can be easily and efficiently achieved in the surface machining.

Claims

1. A method for the surface machining of workpieces composed of non-brittle materials in optical lens manufacturing, such as plastic spectacle lenses, in which the workpiece rotating with a controlled angle of rotation about an axis of work rotation is subjected to a milling operation by a tool, which rotates about an axis of tool rotation enclosing a predetermined angle with the axis of work rotation, the workpiece and the tool being movable relative to one another with their position controlled in at least one of two axes running at right angles, wherein the tool during an infeed grinding operation produces an annular trough-shaped recess at least in the area of the outer edge of the workpiece, before the tool in a shaping operation abrades further material along a helical path over the workpiece;

and wherein said milling operation is followed by a rotational machining operation, in which a rotational cutting edge provided on the tool is applied, by a positionally controlled relative movement of workpiece and tool in at least one of the two axes and by a swivel movement of the tool, with a controlled angle of rotation about the axis of tool rotation, tangentially to the surface to be machined on the workpiece that is being turned with a controlled angle of rotation about the axis of work rotation, and, in the rotational machining engagement, is guided along a helical path over the workpiece.

2. A method according to claim 1, wherein, in the rotational machining operation at least one area of a rotational cutting edge of the tool is brought into rotational machining engagement with the surface of the workpiece to be machined, at least that area of the rotational cutting edge brought into rotational machining engagement being equally or only slightly more curved than the surface to be machined.

3. A method according to claim 1, wherein, in the rotational machining operation at least one area of a rotational cutting edge of the tool is brought into rotational machining engagement with the surface of the workpiece to be machined, the tool for further rotational machining operations being swiveled with a controlled angle of rotation about the axis of tool rotation as a function of the wear of the rotational cutting edge, in order to bring another area of this rotational cutting edge or at least an area of another rotational cutting edge into rotational machining engagement with the surface of the workpiece to be machined.

4. A method according to claim 1, wherein, for the rotational machining operation a rotational cutting edge is used on the tool which has differently curved areas, the tool being swiveled with a controlled angle of rotation about the axis of tool rotation as a function of the desired cutting volume and the desired surface quality of the machined surface of the workpiece, in such a way that for a comparatively large cutting volume a more heavily curved area of the rotational cutting edge is brought into rotational machining engagement with the surface of the workpiece to be machined, whereas for a comparatively high surface quality a less heavily curved area of the rotational cutting edge is brought into rotational machining engagement with the surface of the workpiece to be machined.

5. A method according to claim 1, wherein, in the rotational machining operation a rotational cutting edge in rotational machining engagement with the surface to be machined is guided over the workpiece along a helical path having a shape similar to an Archimedean spiral.

6. A method according to claim 1, wherein a high-pressure coolant jet is directed at the point of machining engagement between tool and workpiece at least during the rotational machining operation.

7. A tool for the surface machining of workpieces composed of non-brittle material in optical lens manufacturing, such as plastic spectacle lenses, the tool having a body defining an axis of tool rotation, on which body a plurality of milling cutter edges are provided, which as the tool rotates about its axis of tool rotation define a circular orbit in a plane perpendicular to the axis of tool rotation, wherein at least one rotational cutting edge is also provided on the body, which is offset radially inwards by a predefined amount in relation to the circular orbit of the milling cutter edges.

8. A tool according to claim 7, wherein multiple rotational cutting edges are provided on the body, which are distributed uniformly over the circumference of the body.

9. A tool according to claim 7, wherein said at least one rotational cutting edge has a constant curvature with a radius, which is substantially equal to the distance of the rotational cutting edge from the axis of tool rotation.

10. A tool according to claim 7, wherein the rotational cutting edge has areas, of different, in each case constant curvature, the curvature viewed in the direction of rotation of the tool diminishing continuously area by area from one end of the rotational cutting edge to the other end of the rotational cutting edge.

11. A tool according to claim 10, wherein the rotational cutting edge has two areas, of which one area has a constant curvature with a radius essentially equal to the distance of the rotational cutting edge from the axis of tool rotation, whilst the other area has a constant curvature with a radius that is distinctly smaller than the radius of the former area.

12. A tool according to claim 7, wherein the rotational cutting edge is formed by a cutting tip on a turning tool, which is detachably fixed to the body.

13. A tool according to claim 12, wherein the body is provided with a blind hole for receiving a shank of the turning tool which is circular in cross-section, the shank having an inclined recess, against which a screw that can be screwed into a tapped hole in the body bears in order to detachably fix the turning tool to the body and to hold it up against a base of the blind hole.

14. A device for the surface machining of workpieces of non-brittle materials in optical lens manufacturing, such as plastic spectacle lenses, the device having a work spindle, by means of which the workpiece can be driven to rotate with a controlled angle of rotation about an axis of work rotation, and a tool spindle, by means of which a tool can be driven to rotate about an axis of tool rotation, which encloses a predetermined angle with the axis of work rotation, the work spindle and the tool spindle being movable relative to one another with their positions controlled in two axes running at right angles;

wherein for a rotational machining of the surface of the workpiece to be machined, the tool can be swiveled by means of the tool spindle with a controlled angle of rotation about the axis of tool rotation, so that a rotational cutting edge provided on the tool can be brought into a defined rotational machining engagement with the surface of the workpiece to be machined as a function of the angle of rotation of the workpiece.

15. A device according to claim 14, wherein both the work spindle and the tool spindle are aligned horizontally.