Laser sintering powder recycle system

Abstract

A method and apparatus for forming three-dimensional objects by laser sintering that includes the use of dense phase pneumatic conveying to internally recycle overflow powder, and to thoroughly blend overflow, recovered and virgin powder to provide a consistent powder feed mix to a laser sintering machine. Overflow powder from the laser sintering machine is recovered and recycled back into the laser sintering machine for reuse. The approach results in a compact and reliable powder recycle system with complete blending and minimum attrition to the handled powder.

1 . An apparatus for producing three-dimensional articles from a powder comprising: 
 (a) a chamber within the apparatus in which a layerwise build process is performed to produce three-dimensional objects, the chamber having a first side and an opposing second side;    (b) a powder feed hopper, located on the first side of the chamber for depositing a quantity of powder into the chamber;    (c) a spreader, located adjacent the feed hopper, for spreading the quantity of powder in the chamber;    (d) a receiving device for receiving overflow powder delivered by the spreader, the receiving device being located adjacent at least one side of the process chamber; and    (e) a pneumatic conveying device in flow communication with the receiving device for returning the overflow powder to the powder feed hopper.    
   
   
       2 . The apparatus of  claim 1  further comprising a separate breakout station which accepts completed output from the apparatus and separates the output into completed parts, recoverable powder, and spent powder.  
   
   
       3 . The apparatus of  claim 1  further comprising a feed line into the apparatus for feeding powder into the feed hopper.  
   
   
       4 . The apparatus of  claim 3  further comprising a powder-processing unit connected to the feed line.  
   
   
       5 . The apparatus of  claim 4  wherein powder fed through the feed line from the powder processing unit is conveyed by pneumatic dense phase conveying by a pneumatic dense phase conveying device.  
   
   
       6 . The apparatus of  claim 1  further comprising the powder feed hopper being located above the first side of the chamber.  
   
   
       7 . The apparatus of  claim 5  wherein the pneumatic dense phase conveying device comprises: 
 (a) a top receiving section for receiving powder to be transferred;    (b) a bottom transfer section, located below the top receiving section, allowing the powder to flow to an outlet;    (c) a porous plate in the bottom section; and    (d) an input of a conveying gas passing through the porous plate.    
   
   
       8 . The apparatus of  claim 4  wherein the powder-processing unit is fed quantities of both virgin and recovered powder.  
   
   
       9 . The apparatus of  claim 4  wherein the powder-processing unit comprises a virgin powder storage vessel that stores and blends quantities of virgin powder.  
   
   
       10 . The apparatus of  claim 9  wherein the virgin powder storage vessel blends by circulating powder through the virgin powder storage vessel.  
   
   
       11 . The apparatus of  claim 10  wherein the powder circulating through the virgin powder storage vessel is conveyed by a pneumatic dense phase conveying device.  
   
   
       12 . The apparatus of  claim 6  further comprising the spreader being positioned below the feed hopper.  
   
   
       13 . The apparatus of  claim 11  wherein the pneumatic dense phase conveying device comprises: 
 (a) a top receiving section for receiving powder to be transferred;    (b) a bottom transfer section, located below the top receiving section, allowing the powder to flow to an outlet;    (c) a porous plate in the bottom section; and    (d) an input of a conveying gas passing through the porous plate.    
   
   
       14 . The apparatus of  claim 9  wherein the virgin powder storage vessel further comprises an interior cone in cone blender device.  
   
   
       15 . The apparatus of  claim 9  wherein the powder-processing unit further comprises a recovered powder storage vessel that stores and blends quantities of recovered powder.  
   
   
       16 . The apparatus of  claim 15  wherein the recovered powder storage vessel blends by circulating powder through the recovered powder storage vessel.  
   
   
       17 . The apparatus of  claim 16  wherein the circulation of powder through the recovered powder storage vessel is conveyed by a pneumatic dense phase conveying device.  
   
   
       18 . The apparatus of  claim 17  wherein the pneumatic dense phase conveying device comprises: 
 (a) a top receiving section for receiving powder to be transferred;    (b) a bottom transfer section, located below the top receiving section, allowing the powder to flow to an outlet;    (c) a porous plate in the bottom section; and    (d) an input of a conveying gas passing through the porous plate.    
   
   
       19 . The apparatus of  claim 15  wherein the recovered powder storage vessel further comprises an interior cone in cone blender device.  
   
   
       20 . The apparatus of  claim 15  wherein the powder-processing unit further comprises a blender vessel for blending and storing combinations of recovered and virgin powder.  
   
   
       21 . The apparatus of  claim 21  wherein the blender storage vessel blends by circulating powder through the blender storage vessel.  
   
   
       22 . The apparatus of  claim 22  wherein the circulation of powder through the blender storage vessel is conveyed by a pneumatic dense phase conveying device.  
   
   
       23 . The apparatus of  claim 22  wherein the pneumatic dense phase conveying device comprises: 
 (a) a top receiving section for receiving powder to be transferred;    (b) a bottom transfer section, located below the top receiving section, allowing the powder to flow to an outlet;    (c) a porous plate in the bottom section; and    (d) an input of a conveying gas passing through the porous plate.    
   
   
       24 . The apparatus of  claim 21  wherein the blender storage vessel further comprises an interior cone in cone blender device.  
   
   
       25 . The apparatus of  claim 1  wherein the pneumatic conveying device is a pneumatic dense phase conveying device that conveys overflow powder via pneumatic dense phase conveying.  
   
   
       26 . The apparatus of  claim 25  further comprising a pneumatic dense phase conveying device for returning the overflow powder to the powder feed hopper.  
   
   
       27 . The apparatus of  claim 26  wherein the dense phase conveying device comprises: 
 (a) a top receiving section for receiving powder to be transferred;    (b) a bottom transfer section, located below the top receiving section, allowing the powder to flow to an outlet;    (c) a porous plate in the bottom section; and    (d) an input of a conveying gas passing through the porous plate.    
   
   
       28 . The apparatus of  claim 4  wherein the breakout station comprises: 
 (a) a worktable for separating recoverable powder and spent powder from finished three-dimensional objects;    (b) a device for processing and separating recoverable powder and spent powder; and    (c) a pneumatic dense phase conveying device for conveying recycle powder to the powder processing unit.    
   
   
       29 . The apparatus of  claim 28  wherein the pneumatic dense phase conveying device comprises: 
 (a) a top receiving section for receiving powder to be transferred;    (b) a bottom transfer section, located below the top receiving section, allowing the powder to flow to an outlet;    (c) a porous plate in the bottom section; and    (d) an input of a conveying gas passing through the porous plate.    
   
   
       30 . The apparatus of  claim 1  wherein the powder feed hopper comprises: 
 (a) an inlet for accepting powder feeds above a hopper chamber;    (b) a cylindrical rotatable roller positioned below the hopper chamber; and    (c) a roller feeder positioned parallel and adjacent the cylindrical rotatable roller to create a defined gap through which powder from the hopper chamber flows as the cylindrical rotatable roller rotates.    
   
   
       31 . The apparatus of  claim 30  wherein the cylindrical rotatable roller has a smooth surface.  
   
   
       32 . The apparatus of  claim 31  further comprising an air slide located below the inlet for accepting powder from the inlet and feeding the powder into the hopper chamber  
   
   
       33 . The apparatus of  claim 32  further comprising an adjustment device to periodically move the roller feeder to increase size of the gap to allow collected powder agglomerates to pass.  
   
   
       34 . A method for producing a bed of powder in a laser sintering machine in which a three-dimensional article is formed in layerwise fashion comprising the steps of: 
 (a) depositing a first portion of powder from a feed hopper in a process chamber across a target area from a first side to an opposing second side;    (b) collecting excess of the first portion of powder as overflow on the opposing second side of the target area;    (c) scanning a laser beam across the first portion of powder in the target area to selectively fuse a layer of powder in a desired cross-section;    (d) depositing a second portion of powder across the target area on the process chamber from the second side to the first side;    (e) collecting excess of the second portion of powder as overflow on the first side of the target area;    (f) scanning a laser beam across the second portion of powder in the target area to selectively fuse a subsequent layer of powder in a desired cross-section; and    (g) pneumatically conveying the overflow from the first side and the second side of target area back to the feed hopper.    
   
   
       35 . The method of  claim 34  further comprising the steps of: 
 (a) separating the three dimensional article from the surrounding bed of powder; and    (b) separating the surrounding bed of powder into recovered powder and spent powder.    
   
   
       36 . The method of  claim 35  further comprising conveying the recovered powder to a recovered powder storage vessel.  
   
   
       37 . The method of  claim 36  further comprising circulating the covered powder through the recovered powder storage vessel to blend contents.  
   
   
       38 . The method of  claim 36  further comprising conveying virgin powder to a virgin powder storage vessel.  
   
   
       39 . The method of  claim 38  further comprising circulating the virgin powder through the virgin powder storage vessel to blend contents.  
   
   
       40 . The method of  claim 39  further comprising combining powder from the recovered powder storage vessel and the virgin powder storage vessel in a blender vessel to form a resultant combined powder.  
   
   
       41 . The method of  claim 40  further comprising circulating powder from the blender vessel back through the blender vessel to create a blended feed powder.  
   
   
       42 . The method of  claim 41  further comprising conveying the blended feed powder to the feed hopper.  
   
   
       43 . The method according to  claim 40  further comprising blending the overflow powder with the resultant combined powder.  
   
   
       44 . The method according to  claim 40  further comprising remotely monitoring system functions during operation of the laser sintering machine and the powder feed, the functions selected from the group consisting of powder blending, powder transfer among powder vessels and the laser sintering machine, emptying powder vessels and adding virgin powder to the blender vessel.  
   
   
       45 . The method according to  claim 44  further comprising remotely monitoring operating parameters of all pressures, powder flow rates, gas flow rates, and powder vessel status.