Process for shaping an ophthalmic product

Abstract

The invention relates to a process for shaping an ophthalmic product (20) using a machining device (200) equipped with clamping means (202, 203), a machining tool (210) and a force sensor (234) adapted to measure a force that is related to the force applied by the machining tool to the ophthalmic product (20). According to the invention, the process comprising: —a step of clamping the ophthalmic product in said clamping means; and —a step of roughing out the ophthalmic product by means of the machining tool so as to bring the initial outline of the ophthalmic product to a final outline of different shape, wherein, during the step of roughing out: —the value of said force is measured by the force sensor, and —the machining speed is continuously adjusted so as to maintain the measured value equal to a target value.

1 . A process for shaping an ophthalmic product using a machining device equipped with clamping means for clamping the ophthalmic product, a machining tool for machining the ophthalmic product and a force sensor adapted to measure a force that is related to the force applied by the machining tool to the ophthalmic product, the process comprising:
 a step of clamping the ophthalmic product in said clamping means; and   a step of roughing out the ophthalmic product by means of the machining tool so as to bring the initial outline of the ophthalmic product to a final outline of different shape,   wherein, during the step of roughing out:   the value of said force is measured by the force sensor, and   the machining speed is continuously adjusted so as to maintain the measured value equal to a target value, said target value being determined as a function of an electrical power consumed by the machining device.   
     
     
         2 . The process for shaping according to  claim 1 , wherein, during the step of roughing out, the machining tool follows a first path that is radiale relative to said clamping means until it reaches the final outline, and a second path along said final outline. 
     
     
         3 . The process for shaping according to  claim 1 , wherein the force sensor is adapted to measure a force component that is radiale relative to said clamping means. 
     
     
         4 . The process for shaping according to  claim 1 , wherein, during said step of roughing out, a comparison operation is performed to compare the electrical power consumed by the machining device with a power threshold, and when the electrical power consumed by the machining device is greater than said power threshold, said target value is reduced of a predetermined amount. 
     
     
         5 . The process for shaping according to  claim 4 , wherein the comparison operation is performed only when said target value is greater than a predetermined threshold. 
     
     
         6 . The process for shaping according to  claim 1 , wherein said machining speed is determined by means of a proportional derivative controller. 
     
     
         7 . The process for shaping according to  claim 6 , wherein said machining speed is determined as a function of:
 a first difference between said measured value and said target value, and   a second difference between the measured value, measured at a current instant, and a measured value measured at a previous instant.   
     
     
         8 . The process for shaping according to  claim 1 , wherein, the final outline being characterized by first points:
 intermediate points are defined between said first points, and   during the roughing out step, at each sampling instant, said machining device is programmed to:   select a next point to be reached among the first points and the intermediate points as a function of the difference between said measured value and said target value, and to   control said machining tool and said clamping means such that the machining tool reaches said next point in a predetermined time amount that is constant from a sampling instant to another.   
     
     
         9 . The process for shaping according to  claim 8 , wherein the number of first points is determined as a function of a maximum machining speed or of a maximum speed of the machining device. 
     
     
         10 . The process for shaping according to  claim 1 , wherein said ophthalmic product is an ophthalmic lens or a mold for molding an ophthalmic lens. 
     
     
         11 . The process for shaping according to  claim 1 , comprising, after said step of roughing out, a finishing step that is performed on the part of the ophthalmic product machined by said machining tool, by means of a finishing tool that is distinct from said machining tool. 
     
     
         12 . The process for shaping according to  claim 1 , wherein during said step of roughing out, said ophthalmic product is machined by the machining tool in a single pass around said clamping means.