Apparatus and Method for Cooling Part Cake in Laser Sintering

Abstract

A part cake defining a build produced by laser sintering and the surrounding unfused powder is contained in an enclosure, aid the enclosure includes displaceable wall portions for compressing the part cake to support the build against distortion during rapid cooling from a cooling fluid. The enclosure enables the part cake to be quickly and reliably cooled either within the laser sintering system or outside the laser sintering system. A source of cooling fluid connects to the enclosure and a lid holds the part cake in place as cooling fluid is forced through the pore volume of the cake. An inert gas blanket apparatus is also provided to reduce or prevent oxidation of the part cake and/or to cool the part cake. Once the part cake is cooled, the build produced by laser sintering may be removed from the part cake.

1 . An apparatus for cooling a part cake containing a build produced by laser sintering, the apparatus comprising:
 a) an enclosure for containing the part cake, the enclosure having a first pair of opposed displaceable wall portions in displaceable relation from a laser sintering position to a part cake compression position and at least one wall portion having fluid passages therethrough; and   b) a source of cooling fluid in fluid communication with the at least one wall portion having fluid passages therethrough for supplying cooling fluid through the part cake when the first pair of opposed displaceable wall portions is in a part cake compression position.   
     
     
         2 . The apparatus of  claim 1  wherein the enclosure further comprises opposed displacement rods corresponding to the first pair of opposed displaceable wall portions, the opposed displacement rods cooperating to displace the at least one first pair of opposed displaceable wall portions from a laser sintering position to a part cake compression position. 
     
     
         3 . The apparatus of  claim 2  further comprising a housing for the enclosure, the housing fixing the displacement rods for displacement of the first pair of opposed displaceable wall portions of the enclosure. 
     
     
         4 . The apparatus of  claim 3  further comprising a wheeled frame for the housing for moving the housing from a laser sintering system to a cooling station having the source of cooling fluid. 
     
     
         5 . The apparatus of  claim 1  further comprising two pairs of opposed displaceable wall portions, the pairs forming the sides of the enclosure. 
     
     
         6 . The apparatus of  claim 5  wherein the at least one wall portion having fluid passages therethrough defines a build platform of the enclosure. 
     
     
         7 . The apparatus of  claim 6  further comprising a lid for the enclosure, wherein the lid is opposed to the build platform and wherein the lid comprises a lower portion that is perforated to provide for passage of cooling fluid through the part cake. 
     
     
         8 . The apparatus of  claim 1  wherein the enclosure comprises a second pair of opposed displaceable wall portions and wherein the apparatus further comprises a housing for the enclosure, the housing comprising opposed displacement rods corresponding to the first and second pairs of opposed displaceable wall portions, the opposed displacement rods cooperating to displace the pairs of opposed displaceable wall portions from a laser sintering position to a part cake compression position. 
     
     
         9 . The apparatus of  claim 8  wherein the first and second pairs of opposed displaceable wall portions are offset at the corners for displaceable relation from a laser sintering position to a compression position. 
     
     
         10 . The apparatus of  claim 1  wherein one wall portion of the first pair of opposed displaceable wall portions is moveable and the other wall portion of the first pair of opposed displaceable wall portion is stationary, such that only one wall portion of the first pair of opposed displaceable wall portions is moved do define the laser sintering position and the part cake compression position. 
     
     
         11 . A method for producing a build by laser sintering, the method comprising:
 a) producing a build in a part cake;   b) removing the part cake from the laser sintering system;   c) compressing the part cake to support the build to generally prevent distortion of the build during cooling;   d) forcing a cooling fluid through the compressed part cake; and   e) removing the build from the part cake.   
     
     
         12 . The method of  claim 11  further comprising decompressing the part cake after the part cake has been cooled, prior to recovering the build from the part cake. 
     
     
         13 . The method of  claim 11  wherein compressing the part cake comprises moving at least one wall portion to a compression position. 
     
     
         14 . The method of  claim 11  wherein forcing a cooling fluid through the compressed part cake comprises attaching a source of forced cooling fluid to a housing that encloses the part cake. 
     
     
         15 . The method of  claim 11  wherein the part cake is compressed to between 60% and 80% of full density. 
     
     
         16 . An inert gas blanket apparatus for covering a part cake containing a build produced by laser sintering, the apparatus comprising:
 a) a lid for selectively covering the part cake, the lid having a passage to receive inert gas and to cause the received inert gas to be in fluid communication with the part cake;   b) an inert gas supply in fluid communication with the passage of the lid; and   c) a controller that selective controls the flow of inert gas from the inert gas supply to the lid,   wherein the inert gas in fluid communication with the part cake generally forms a blanket of inert gas that generally reduces oxidation of the part cake.   
     
     
         17 . The apparatus of  claim 16  wherein the inert gas comprises nitrogen. 
     
     
         18 . The apparatus of  claim 16  wherein the controller comprises at least one valve device that selectively controls the flow of inert gas from the inert gas supply to the lid. 
     
     
         19 . The apparatus of  claim 16  wherein the lid comprises a top portion generally parallel to a top surface of the part cake when the lid is covering the part cake and wherein the lid comprises at least one sidewall overhanging the sides of the part cake such that the inert gas is supplied to a passage in the top portion of the lid and the inert gas generally flows over the top surface of the part cake and between the sides of the part cake and the sidewall of the lid to generally define a blanket of inert gas over the top surface of the part cake. 
     
     
         20 . The apparatus of  claim 16  wherein the lid comprises a top portion and wherein the inert gas is supplied to a passage in the top portion of the lid and the inert gas generally flows over the top surface of the part cake and down through the part cake.