Heated Mold Tooling

Abstract

A method for varying a radius of an optical quality surface of a casting mold formed in a tooling cavity, the tooling cavity at least partially defined by an optical tool having an optical quality surface of a given radius, includes imparting a compressive stress within the optical quality surface of the casting mold to predictably decrease the radius of the optical quality surface of the casting mold.

1 . A method for varying a radius of an optical quality surface of a casting mold formed in a tooling cavity, the tooling cavity at least partially defined by an optical tool having an optical quality surface of a given radius, the method comprising:
 (a) imparting a tensile stress within the optical quality surface of the casting mold to predictably increase the radius of the optical quality surface of the casting mold.   
   
   
       2 . The method of  claim 1 , further comprising forming an annular flange circumscribing the optical quality surface of the casting mold and decreasing, relative to the flange, a cooling rate of a polymeric material adjacent the optical quality surface of a given radius to impart the tensile stress. 
   
   
       3 . The method of  claim 1 , wherein imparting the tensile stress further comprises decreasing a cooling rate of a portion of the optical quality surface of the optical tool. 
   
   
       4 . The method of  claim 1 , wherein imparting the tensile stress further comprises sensing a temperature of a portion of the optical tool. 
   
   
       5 . The method of  claim 4 , further including selectively heating a portion of the optical quality surface of the optical tool based on the sensed temperature. 
   
   
       6 . The method of  claim 1 , wherein the optical quality surface of the casting mold is one of convex and concave. 
   
   
       7 . A method of forming polymeric casting molds in a tooling cavity, the tooling cavity at least partially defined by an optical tool having an optical quality surface of a given radius, the method comprising:
 (a) forming a first casting mold having an optical quality surface radius smaller than the given radius; and   (b)forming a second casting mold having an optical quality surface radius greater than the given radius.   
   
   
       8 . The method of  claim 7 , wherein the first and second casting molds are one of an anterior mold half and a posterior mold half. 
   
   
       9 . The method of  claim 7 , further comprising selectively modifying a cooling rate of a portion of the optical quality surface of the optical tool based on a cooling rate of a portion of the tooling cavity. 
   
   
       10 . The method of  claim 7 , further comprising selectively modifying a temperature of a flange forming portion of the tooling cavity. 
   
   
       11 . The method of  claim 10 , wherein the flange forming portion extends radially around the optical quality surface of the optical tool. 
   
   
       12 . The method of  claim 7 , further comprising imparting a compressive stress within the optical quality surface of the first casting mold. 
   
   
       13 . The method of  claim 12 , wherein imparting the compressive stress assists in predictably decreasing the optical quality surface radius of the first casting mold. 
   
   
       14 . The method of  claim 7 , further comprising imparting a tensile stress within the optical quality surface of the second casting mold. 
   
   
       15 . The method of  claim 14 , wherein imparting the tensile stress assists in predictably increasing the optical quality surface radius of the second casting mold. 
   
   
       16 . The method of  claim 7 , further comprising sensing a temperature of a portion of the optical tool and modifying a temperature of one of the portion of the optical tool and a flange forming portion of the tooling cavity based on the sensed temperature. 
   
   
       17 . A casting mold configured to form an ophthalmic device having an optical quality surface, the casting mold comprising:
 (a) an optical quality surface, and;   (b) a circumscribing flange,
 the optical quality surface of the casting mold having a residual compressive stress, the residual compressive stress decreasing a radius of the optical quality surface. 
   
   
   
       18 . The casting mold of  claim 17 , wherein the optical surface is one of convex and concave. 
   
   
       19 . The casting mold of  claim 17 , further comprising a posterior mold half and an anterior mold half. 
   
   
       20 . The casting mold of  claim 19 , wherein the optical quality surface is a convex surface of the posterior mold half. 
   
   
       21 . The casting mold of  claim 19 , wherein the optical quality surface is a concave surface of the anterior mold half. 
   
   
       22 . The casting mold of  claim 19 , wherein the anterior mold half defines a radial shelf configured to support a plurality of fins of the posterior mold half. 
   
   
       23 . The casting mold of  claim 19 , wherein a portion of the anterior mold half is configured to accept a portion of the posterior mold half so as to define a forming cavity between the mold halves. 
   
   
       24 . The casting mold of  claim 23 , wherein the forming cavity is defined by an optical quality surface of the anterior mold half and an optical quality surface of the posterior mold half. 
   
   
       25 . A casting mold configured to form an ophthalmic device having an optical quality surface, the casting mold comprising:
 (a) an optical quality surface, and;   (b) a circumscribing flange,
 the optical quality surface of the casting mold having a residual tensile stress, the residual tensile stress increasing a radius of the optical quality surface. 
   
   
   
       26 . The casting mold of  claim 25 , wherein the optical surface is one of convex and concave. 
   
   
       27 . The casting mold of  claim 25 , further comprising a posterior mold half and an anterior mold half. 
   
   
       28 . The casting mold of  claim 27 , wherein the optical quality surface is a convex surface of the posterior mold half. 
   
   
       29 . The casting mold of  claim 27 , wherein the optical quality surface is a concave surface of the anterior mold half. 
   
   
       30 . The casting mold of  claim 27 , wherein the anterior mold half defines an annular shoulder configured to engage a plurality of fins of the posterior mold half. 
   
   
       31 . The casting mold of  claim 27 , wherein a portion of the anterior mold half is configured to accept a portion of the posterior mold half so as to define a forming cavity between the mold halves. 
   
   
       32 . The casting mold of  claim 31 , wherein the forming cavity is defined by an optical quality surface of the anterior mold half and an optical quality surface of the posterior mold half. 
   
   
       33 . A tooling cavity configured to form a polymeric casting mold, comprising:
 (a) a tool body;   (b) an optical tool removably connected to the tool body, the optical tool defining an optical quality surface of a given radius;   (c) a non-optical tool configured to assist in forming a radius forming portion opposite the optical quality surface; and   (d) a heat source connected to the tool body and configured to selectively heat a portion of the optical quality surface.   
   
   
       34 . The tooling cavity of  claim 33 , further comprising a flange forming portion circumscribing the optical quality surface of the optical tool. 
   
   
       35 . The tooling cavity of  claim 34 , further comprising an additional heat source disposed proximate the flange forming portion and configured to increase the temperature of the flange forming portion. 
   
   
       36 . The tooling cavity of  claim 35 , wherein the additional heat source is configured to assist in imparting a compressive stress within an optical quality surface of the polymeric casting mold. 
   
   
       37 . The tooling cavity of  claim 35 , wherein the additional heat source is configured to assist in predictably decreasing a radius of an optical quality surface of the polymeric casting mold. 
   
   
       38 . The tooling cavity of  claim 35 , wherein the additional heat source is configured to assist in increasing, relative to the flange forming portion, a cooling rate of the a polymeric material adjacent the optical quality surface of the optical tool. 
   
   
       39 . The tooling cavity of  claim 34 , wherein the heat source is configured to assist in decreasing, relative to the flange forming portion, a cooling rate of the a polymeric material adjacent the optical quality surface of the optical tool. 
   
   
       40 . The tooling cavity of  claim 33 , wherein the heat source is configured to assist in imparting a tensile stress within an optical quality surface of the polymeric casting mold. 
   
   
       41 . The tooling cavity of  claim 33 , wherein the heat source is configured to assist in predictably increasing a radius of an optical quality surface of the polymeric casting mold. 
   
   
       42 . The tooling cavity of  claim 33 , further comprising a cooling circuit configured to reduce a temperature of a portion of at least one of the non-optical tool and the tool body.