Method and Apparatus Associated with Anisotropic Shrink in Sintered Ceramic Items

Abstract

A manufacturing method for producing ceramic item from a photocurable ceramic filled material by stereolithography. The method compensates for the anisotropic shrinkage of the item during firing to produce a dimensionally accurate item.

1 . A method, comprising:
 representing an item including its dimensions relative to a three dimensional coordinate system, the item adapted to be formed as a green ceramic item in a stereolithography apparatus from a photo-polymerizable material including ceramic particles;   applying at least two unequal scaling factors to the dimensions to compensate for the anisotropic shrinkage of the green ceramic item relative to the axes of the coordinate system upon the green ceramic item being sintered;   building the green ceramic item in the stereolithography apparatus after said applying; and   heating the green ceramic item to form a sintered ceramic item substantially conforming to the dimensions.   
   
   
       2 . The method of  claim 1 , wherein in said applying the scaling factors are all unequal. 
   
   
       3 . The method of  claim 1 , wherein said building includes forming a plurality of layers of the photo-polymerizable material; and
 which further includes leveling at least one of the plurality of layers of the photo-polymerizable material prior to forming the next of the plurality of layers of the photo-polymerizable material; and   which further includes exposing the at least one of the plurality of layers of the photo-polymerizable material with a dose of energy prior to forming the next of the plurality of layers of the photo-polymerizable material.   
   
   
       4 . The method of  claim 3 , wherein said leveling including mechanically wiping a surface of the at least one of the plurality of layers of the photo-polymerizable material. 
   
   
       5 . The method of  claim 4 , wherein said mechanically wiping changes the homogeneity of the ceramic particles in at least two dimensions. 
   
   
       6 . The method of  claim 4 , wherein said leveling includes leveling each of the plurality of layers of the photo-polymerizable material; and
 which further includes exposing each of the plurality of layers of the photo-polymerizable material with a dose of energy.   
   
   
       7 . The method of  claim 1 , wherein the stereolothography apparatus includes a machine three dimensional coordinate system coextensive with the three dimensional coordinate system. 
   
   
       8 . The method of  claim 1 , wherein the sintered ceramic item is of a near net shape. 
   
   
       9 . The method of  claim 1 , wherein the sintered ceramic item is of a net shape. 
   
   
       10 . The method of  claim 1 , wherein the sintered ceramic item is dimensionally accurate with the dimensions within about 1.5%. 
   
   
       11 . The method of  claim 1 , wherein the sintered ceramic item is dimensionally accurate with the dimensions within about 0.5%. 
   
   
       12 . The method of  claim 1 , wherein said heating includes burning off a polymer in the green ceramic item. 
   
   
       13 . The method of  claim 2 , wherein the three dimensional coordinate system is a Cartesian coordinate system including a first axis corresponding to the X axis and a second axis corresponding to the Y axis and a third axis corresponding to the Z axis;
 wherein the stereolothography apparatus includes a machine three dimensional coordinate system coextensive with the three dimensional coordinate system;   which further includes selecting a build direction corresponding to the Z axis;   wherein said building includes forming a plurality of layers from the photo-polymerizable material in the build direction; and   which further includes wiping an upper surface of each of the plurality of layers of the photo-polymerizable material prior to being exposed to an energy dose, said wiping in the direction of one of the other axes.   
   
   
       14 . The method of  claim 1 , wherein the photo-polymerizable material includes ceramic particles within a range of 35% to 65% by volume. 
   
   
       15 . The method of  claim 1 , wherein said representing is associated with any of electronic data, digital data, virtual data, computer files, solid body modeling, computer modeling, computer aided manufacturing. 
   
   
       16 . The method of  claim 1 , wherein said heating is to a temperature within a range of about 1100° C. to 1700° C. 
   
   
       17 . A method, comprising:
 providing a data representation of an item;   selecting a build orientation for building the item in a stereolithography apparatus from a photo-polymerizable material including ceramic particles, wherein the stereolithography apparatus including a three dimensional coordinate system with a first axis, a second axis and a third axis;   modifying the data representation of the item to form a modified data representation by applying a first expansion factor to increase the dimensions of the item along the first axis and a second expansion factor to increase the dimensions of the item along the second axis and a third expansion factor to increase the dimensions of the item along the third axis, wherein said expansion factors are not equal; and   forming a green state ceramic item conforming to the modified data representation by controlling the delivery of energy to the photo-polymerizable material.   
   
   
       18 . The method of  claim 17 , wherein said forming including building a plurality of layers from the photo-polymerizable material, and wherein the photo-polymerizable material includes a monomer and a photoinitator. 
   
   
       19 . The method of  claim 18 , which further includes leveling each of the plurality of layers of the photo-polymerizable material, and wherein said forming includes exposing each of the plurality of layers of the photo-polymerizable material to an energy dose. 
   
   
       20 . The method of  claim 19 , wherein in said forming the item is built in the direction of the third axis and said leveling including mechanically wiping a surface of each of the plurality of layers of the photo-polymerizable material with a wiper blade. 
   
   
       21 .- 56 . (canceled)