Powder feeder for material deposition systems

Abstract

A method and apparatus for embedding features and controlling material composition in a three-dimensional structure ( 130 ) is disclosed. The invention enables the control of material characteristics, within a structure ( 130 ) made from a plurality of materials, directly from computer renderings of solid models of the components. The method uses stereolithography and solid model computer file formats to control a multi-axis head ( 480 ) in a directed material deposition process ( 123 ). Material feedstock ( 126, 127 ) is deposited onto a pre-heated substrate ( 19 ). Depositions ( 15 ) in a layer-by-layer pattern, defined by solid models ( 141, 146 ), create a three-dimensional article having complex geometric details. Thermal management of finished solid articles ( 250 - 302 ), not available through conventional processing techniques, is enabled by embedded voids ( 152 ) and/or composite materials ( 126, 127 ), which include dissimilar metals ( 210, 216 ). Finished articles control pressure drop and produce uniform coolant flow and pressure characteristics. High-efficiency heat transfer is engineered within a solid structure by incorporating other solid materials with diverse indexes. Embedding multi-material structures ( 132, 134 ) within a normally solid component ( 141 ) produces articles with diverse mechanical properties. Laser and powder delivery systems ( 420, 170 ) are integrated in a multi-axis deposition head ( 480 ) having a focused particle beam ( 502 ) to reduce material waste.

1 . A powder feeder comprising: 
 a chamber;    an inlet for providing powder to said chamber, the powder forming a pile in said chamber;    a rotating disk partially immersed in said pile, said disk comprising a plurality of circumferentially disposed receptacles for picking up and removing powder from said pile; and    a wiper assembly for removing the powder from said receptacles.    
   
   
       2 . The powder feeder of  claim 1  wherein an angle of repose of said pile continuously limits a flow of powder into said chamber.  
   
   
       3 . The powder feeder of  claim 2  wherein said disk is not clogged by the powder.  
   
   
       4 . The powder feeder of  claim 1  wherein said receptacles comprise holes in said disk.  
   
   
       5 . The powder feeder of  claim 1  wherein said receptacles bring a controlled volume of powder to said wiper assembly.  
   
   
       6 . The powder feeder of  claim 1  wherein a spacing of said wiper assembly from said disk is chosen to minimize contact between the powder and said wiper assembly.  
   
   
       7 . The powder feeder of  claim 6  wherein wear of said wiper assembly is substantially reduced.  
   
   
       8 . The powder feeder of  claim 1  wherein said wiper assembly provides a first gas flow substantially perpendicular to said disk.  
   
   
       9 . The powder feeder of  claim 8  wherein said first gas flow comprises a flow of an inert gas.  
   
   
       10 . The powder feeder of  claim 8  wherein said powder feeder is insensitive to variations in a rate of said first gas flow.  
   
   
       11 . The powder feeder of  claim 8  wherein said first gas flow clears powder from said receptacles and entrains the powder, thereby providing a powder flow.  
   
   
       12 . The powder feeder of  claim 11  wherein said first gas flow fluidizes the powder.  
   
   
       13 . The powder feeder of  claim 11  wherein a rate of said powder flow is proportional to a rotational speed of said disk.  
   
   
       14 . The powder feeder of  claim 11  wherein a rate of said powder flow is as low as approximately 0.1 grams per minute.  
   
   
       15 . The powder feeder of  claim 11  wherein a rate of said powder flow is linear between approximately 0.1 grams per minute and approximately 30 grams per minute.  
   
   
       16 . The powder feeder of  claim 11  further comprising: 
 a gas inlet providing a second gas flow;    a spool valve assembly comprising a plunger, said plunger comprising a plurality of passages for diverting from one to one hundred percent of said powder flow to a first waste stream and diverting from one to one hundred percent of said second gas flow to a second waste stream;    an outlet for mixing an undiverted portion of said powder flow together with an undiverted portion of said second gas flow to form a final powder mass flow having a controlled rate; and    at least one outlet for collecting waste gas and powder.    
   
   
       17 . The powder feeder of  claim 16  further comprising a flow rate controller for each of said powder flow and said second gas flow.  
   
   
       18 . The powder feeder of  claim 16  through which gas is constantly flowing.  
   
   
       19 . The powder feeder of  claim 16  comprising a sufficient gas flow to prevent powder from settling out of said powder flow or said final powder mass flow.  
   
   
       20 . The powder feeder of  claim 16  wherein said plunger is rapidly moveable within said spool valve assembly.  
   
   
       21 . The powder feeder of  claim 20  wherein said controlled rate of said final powder mass flow is rapidly variable.  
   
   
       22 . The powder feeder of  claim 21  wherein said controlled rate of said final powder mass flow is variable from no powder to a mass flow rate of said powder flow.  
   
   
       23 . The powder feeder of  claim 16  wherein a position of said plunger is controllable by a computer.  
   
   
       24 . The powder feeder of  claim 16  further comprising a mass flow sensor.  
   
   
       25 . The powder feeder of  claim 24  further comprising a feedback loop for control of said final powder mass flow rate.  
   
   
       26 . A material deposition apparatus comprising at least one of said powder feeders according to  claim 16 .  
   
   
       27 . The material deposition apparatus of  claim 26  for depositing a first powder and a second powder, said apparatus rapidly controlling relative proportions of the first powder supplied from a first powder feeder and the second powder supplied from a second powder feeder.  
   
   
       28 . The material deposition apparatus of  claim 27  wherein said apparatus deposits three-dimensional gradient material structures.  
   
   
       29 . The material deposition apparatus of  claim 27  wherein said apparatus deposits a buttering layer.  
   
   
       30 . A method for providing a powder flow, the method comprising the steps of: 
 forming a pile of powder;    continuously limiting a size of the pile;    moving a quantity of the powder from the pile to a first gas flow; and    entraining the moved powder in the first gas flow to form a powder flow.    
   
   
       31 . The method of  claim 30  wherein the limiting step comprises blocking a powder supply tube until the pile collapses, thereby temporarily unblocking the tube.  
   
   
       32 . The method of  claim 30  wherein the moving step comprises filling with powder a plurality of receptacles circumferentially disposed in a rotating disk.  
   
   
       33 . The method of  claim 32  wherein the receptacles comprise holes in the disk.  
   
   
       34 . The method of  claim 32  further comprising the step of partially immersing the disk in the pile.  
   
   
       35 . The method of  claim 34  further comprising preventing clogging of the disk.  
   
   
       36 . The method of  claim 30  further comprising the step of controlling the quantity of the powder being moved.  
   
   
       37 . The method of  claim 30  wherein the entraining step comprises fluidizing the powder.  
   
   
       38 . The method of  claim 32  wherein a powder flow rate is proportional to a rotational speed of the disk.  
   
   
       39 . The method of  claim 30  wherein a powder flow rate is as low as approximately 0.1 grams per minute.  
   
   
       40 . The method of  claim 30  wherein a powder flow rate is linear between approximately 0.1 grams per minute and approximately 30 grams per minute.  
   
   
       41 . The method of  claim 30  further comprising the steps of: 
 providing a second gas flow;    diverting from zero to one hundred percent of the powder flow to a first waste stream;    diverting from zero to one hundred percent of the second gas flow to a second waste stream; and    mixing an undiverted portion of the powder flow together with an undiverted portion of the second gas flow to form a final powder mass flow.    
   
   
       42 . The method of  claim 41  further comprising the step of collecting waste gas and powder from the first waste stream and the second waste stream.  
   
   
       43 . The method of  claim 41  further comprising the step of separately controlling a rate of the second gas flow and a rate of the powder flow.  
   
   
       44 . The method of  claim 41  further comprising providing sufficient gas flow to prevent powder from settling out of the powder flow or the final powder mass flow.  
   
   
       45 . The method of  claim 41  further comprising the step of controlling a rate of the final powder mass flow.  
   
   
       46 . The method of  claim 45  wherein the controlling step comprises rapidly varying the rate of the final powder mass flow.  
   
   
       47 . The method of  claim 45  wherein the controlling step comprises using a computer.  
   
   
       48 . The method of  claim 45  wherein the controlling step comprises varying the rate of the final powder mass flow from no powder to a mass flow rate of the powder flow.  
   
   
       49 . The method of  claim 45  further comprising the step of measuring the rate of the final powder mass flow.  
   
   
       50 . The method of  claim 49  further comprising the step of providing a feedback loop for controlling the rate of the final powder mass flow.  
   
   
       51 . The method of  claim 41  further comprising the step of depositing powder from the final powder mass flow.  
   
   
       52 . The method of  claim 51  further comprising the step of depositing a first powder from the final powder mass flow and a second powder from a second final powder mass flow.  
   
   
       53 . The method of  claim 52  further comprising the step of rapidly controlling relative proportions of the first powder and the second powder during deposition.  
   
   
       54 . The method of  claim 53  wherein the depositing step comprises depositing three-dimensional gradient material structures.  
   
   
       55 . The method of  claim 53  wherein the depositing step comprises depositing a buttering layer.