Method for Machining Optical Workpieces, in Particular Spectacle Lenses Made of Plastic

Abstract

A method for machining optical workpieces has the following steps: i) providing the blank that is to be machined at least on the rear side and edge; ii) receiving the blank without a block in order to retain it in a supported manner; iii) machining the blank on the front side by use of a first tool to form a peripheral geometric shape with a depth greater than or equal to the edge thickness of the semifinished product to be formed; iv) receiving the workpiece to retain it in a supported manner on the front side; and v) machining the workpiece on the rear side by use of a second tool to form the semifinished product with the predetermined surface geometry on the rear side.

What is claimed is: 
     
         1 . A method of machining optical workpieces, in which a semi-finished product (HZ) with predetermined surface geometries at a front side (FS) and a rear side (RS) remote therefrom and with a contoured edge (RA) of predetermined edge thickness (D 2 ) between the front side (FS) and the rear side (RS) is formed starting from a blank (RL), comprising the following principal steps executed in the stated sequence:
 i) providing the blank (RL), which has a blank thickness (D 1 ) and can already have the predetermined surface geometry at the front side (FS) and which is to be processed at least at the rear side (RS) and the edge (RA);   ii) block-free picking up of the blank (RL) at the rear side (RS) for supported holding of the workpiece;   iii) processing of the blank (RL) at the front side (FS) by a first tool (WZ 1 ) for formation of an encircling groove (NU) or step (ST) with a depth (TI) greater than or equal to the edge thickness (D 2 ) of the semi-finished product (HZ) to be formed and smaller than the blank thickness (D 1 ), or of an encircling cut having at least in part a depth equal to the blank thickness (D 1 ) so that a circumferential surface (UF) defining the contoured edge (RA) of the semi-finished product (HZ) to be formed remains at the workpiece;   iv) picking up the workpiece at the front side (FS) for supported holding of the workpiece; and   v) processing the workpiece at the rear side (RS) by at least one second tool (WZ 2 ) for formation of the semi-finished product (HZ) with the predetermined surface geometry at the rear side (RS).   
     
     
         2 . A method according to  claim 1 , wherein, in the principal step iii), during formation of the encircling groove (NU) or step (ST) or of the encircling cut, an edge contour (RK 1 ) is produced at the semi-finished product (HZ) by the first tool (WZ 1 ), that has a slight oversize in relation to an edge contour (RK 2 ) of the workpiece processed to finished state, and wherein the edge contour (RK 2 ) of the workpiece processed to finished state is produced only after the principal step v) for processing the rear side (RS) of the workpiece. 
     
     
         3 . A method according to  claim 1 , wherein, in the principal step iii), during or after formation of the encircling groove (NU) or step (ST) or of the encircling cut, an edge contour (RK 2 ) is produced at the semi-finished product (HZ) by the first tool (WZ 1 ) or a further tool, that already corresponds with an edge contour (RK 2 ) of the workpiece processed to finished state. 
     
     
         4 . A method according to  claim 3 , wherein, in the principal step iii), a chamfer (FA 1 ) is applied to the transition between the edge (RA) and the rear side (RS) of the semi-finished product (HZ) to be formed and/or a chamfer is applied to the transition between the edge (RA) and the front side (FS) of the semi-finished product (HZ) to be formed. 
     
     
         5 . A method according to  claim 4 , wherein, in the principal step iii), the chamfer or chamfers (FA 1 ) is or are applied by the first tool (WZ 1 ) at the same time as the encircling groove (NU) or step (ST) or the encircling cut. 
     
     
         6 . A method according to  claim 5 , wherein, in the principal step iii), a fastening geometry for the workpiece processed to finished state is produced at the edge (RA) and/or at the front side (FS) of the semi-finished product (HZ) to be formed. 
     
     
         7 . A method according to  claim 6 , wherein, in the principal step iii), the fastening geometry for the workpiece processed to finished state is formed by the first tool (WZ 1 ′) at the same time as the encircling groove (NU) or step (ST) or the encircling cut. 
     
     
         8 . A method according to  claim 7 , wherein the fastening geometry produced in the principal step iii) for the workpiece processed to finished state is a pointed or roof bevel (SF) or an encircling channel or groove at the edge (RA) of the semi-finished product (HZ) to be formed and/or wherein the fastening geometry produced in the principal step iii) for the workpiece processed to finished state comprises one or more bores or notches at the front side (FS) and/or the edge (RA). 
     
     
         9 . A method according to  claim 8 , wherein, at the start of the principal step iii), the first tool (WZ 1 ) and/or the workpiece are so moved relative to one another that, for formation of the encircling groove (NU) or step (ST) or the encircling cut, the first tool (WZ 1 ) enters the workpiece at a frontal entry point starting from the front side (FS) of the workpiece. 
     
     
         10 . A method according to  claim 8 , wherein, at the start of the principal step iii), the first tool (WZ 1 ) and/or the workpiece are so moved relative to one another that, for formation of the encircling groove (NU) or step (ST) or the encircling cut, the first tool (WZ 1 ) enters the workpiece at an edge entry point(ES) starting from the edge (RA) of the workpiece. 
     
     
         11 . A method according to  claim 10 , wherein, in the principal step iii) after entry of the first tool (WZ 1 ) into the workpiece, the first tool (WZ 1 ) and/or the workpiece are so moved relative to one another that the first tool (WZ 1 ) produces the groove (NU) or step (ST) or cut in at least one revolution at the workpiece, and wherein the first tool (WZ 1 ) leaves the workpiece at the edge (RA) of the workpiece at an edge exit point (AS) remote from the frontal or edge entry point(ES). 
     
     
         12 . A method according to  claim 11 , wherein, in the principal step iii), a rotationally driven end mill is used as the first tool (WZ 1 ) for processing the blank (RL) at the front side (FS). 
     
     
         13 . A method according to  claim 12 , wherein the first tool (WZ 1 ) used in the principal step iii) for processing the blank (RL) at the front side (FS) is different from the at least one second tool (WZ 2 ) used in the principal step v) for processing the workpiece at the rear side (RS). 
     
     
         14 . A method according to  claim 13 , wherein, in the principal step iv), the workpiece is picked up block-free at the front side (FS). 
     
     
         15 . A method according to  claim 14 , wherein the workpiece in the principal step iv) is so picked up at the front side (FS) that the workpiece is held at the front side (FS) with support over the whole area. 
     
     
         16 . A method according to  claim 2 , wherein, in the principal step iii), a chamfer (FA 1 ) is applied to the transition between the edge (RA) and the rear side (RS) of the semi-finished product (HZ) to be formed and/or a chamfer is applied to the transition between the edge (RA) and the front side (FS) of the semi-finished product (HZ) to be formed. 
     
     
         17 . A method according to  claim 16 , wherein, in the principal step iii), the chamfer or chamfers (FA 1 ) is or are applied by the first tool (WZ 1 ) at the same time as the encircling groove (NU) or step (ST) or the encircling cut. 
     
     
         18 . A method according to  claim 3 , wherein, in the principal step iii), a fastening geometry for the workpiece processed to finished state is produced at the edge (RA) and/or at the front side (FS) of the semi-finished product (HZ) to be formed. 
     
     
         19 . A method according to  claim 18 , wherein, in the principal step iii), the fastening geometry for the workpiece processed to finished state is formed by the first tool (WZ 1 ′) at the same time as the encircling groove (NU) or step (ST) or the encircling cut. 
     
     
         20 . A method according to  claim 6 , wherein the fastening geometry produced in the principal step iii) for the workpiece processed to finished state is a pointed or roof bevel (SF) or an encircling channel or groove at the edge (RA) of the semi-finished product (HZ) to be formed and/or wherein the fastening geometry produced in the principal step iii) for the workpiece processed to finished state comprises one or more bores or notches at the front side (FS) and/or the edge (RA). 
     
     
         21 . A method according to  claim 1 , wherein, at the start of the principal step iii), the first tool (WZ 1 ) and/or the workpiece are so moved relative to one another that, for formation of the encircling groove (NU) or step (ST) or the encircling cut, the first tool (WZ 1 ) enters the workpiece at a frontal entry point starting from the front side (FS) of the workpiece. 
     
     
         22 . A method according to  claim 1 , wherein, at the start of the principal step iii), the first tool (WZ 1 ) and/or the workpiece are so moved relative to one another that, for formation of the encircling groove (NU) or step (ST) or the encircling cut, the first tool (WZ 1 ) enters the workpiece at an edge entry point(ES) starting from the edge (RA) of the workpiece. 
     
     
         23 . A method according to  claim 22 , wherein, in the principal step iii) after entry of the first tool (WZ 1 ) into the workpiece, the first tool (WZ 1 ) and/or the workpiece are so moved relative to one another that the first tool (WZ 1 ) produces the groove (NU) or step (ST) or cut in at least one revolution at the workpiece, and wherein the first tool (WZ 1 ) leaves the workpiece at the edge (RA) of the workpiece at an edge exit point (AS) remote from the frontal or edge entry point(ES). 
     
     
         24 . A method according to  claim 1 , wherein, in the principal step iii), a rotationally driven end mill is used as the first tool (WZ 1 ) for processing the blank (RL) at the front side (FS). 
     
     
         25 . A method according to  claim 1 , wherein the first tool (WZ 1 ) used in the principal step iii) for processing the blank (RL) at the front side (FS) is different from the at least one second tool (WZ 2 ) used in the principal step v) for processing the workpiece at the rear side (RS). 
     
     
         26 . A method according to  claim 1 , wherein, in the principal step iv), the workpiece is picked up block-free at the front side (FS). 
     
     
         27 . A method according to  claim 1 , wherein the workpiece in the principal step iv) is so picked up at the front side (FS) that the workpiece is held at the front side (FS) with support over the whole area.