Method and System for Quality Assurance and Control of Additive Manufacturing Process

Abstract

An additive manufacturing system and method is provided for fabricating 3D objects ( 16 ) from successive layers ( 14 ) of material. The additive manufacturing system ( 10 ) has an energy projection assembly ( 20 ) for inputting energy ( 22 ) into a specified area within the layer ( 18 ) to consolidate the material; a plurality of image sensors ( 30 , 32 , 34 ), each of the image sensors having a corresponding field of view ( 35 , 40 , 42 ) covering at least part of the layer ( 18 ) of material, such that each of the fields of view at least partially overlap with the field of view of at least one other of the image sensors; and an image processor ( 56 ) to capture image data from each of the image sensors ( 30 , 32 , 34 ). The image processor ( 56 ) controls exposure times for each of the image sensors ( 30 , 32 , 34 ) and combines the image data from the image sensors to provide a single, spatially resolved image of the energy being input throughout the specified area for each layer ( 14 ) of material respectively for comparison against threshold data values to locate potential consolidation defects in the specified area.

1 . An additive manufacturing system for fabricating 3D objects from successive layers of material, the additive manufacturing system comprising:
 an energy projection assembly for inputting energy into a specified area within the layer to consolidate the material;   a processor configured to receive data indicative of energy input to the material and thereby identify regions of the specified area having insufficient energy input as defect regions not meeting a predetermined quality metric; wherein,   the processor operatively controls the energy projection assembly to selectively apply energy to the defect regions.   
     
     
         2 . An additive manufacturing system according to  claim 1  wherein the processor is further configured to vary input power to the energy projection assembly to adjust the energy input to the material. 
     
     
         3 . An additive manufacturing system according to  claim 2  wherein the energy selectively applied to the defect regions is controlled by the processor to provide the material with a customised microstructure. 
     
     
         4 . An additive manufacturing system according to  claim 3  wherein the customised microstructure differs from the microstructure of the material in the remainder of the specified area. 
     
     
         5 . An additive manufacturing system according to  claim 1  wherein the energy projection assembly has a scanning energy beam and the processor is configured to selectively control one or more of the following process parameters during the application of energy to the defect regions:
 scan speed; 
 scan acceleration; 
 scan direction; 
 hatch distance being the spacing between adjacent scan tracks; 
 offset distance being a difference, if any, between an area scanned by the energy beam and the defect region; 
 beam focus in which the energy beam input spot size is altered; and 
 beam input power modulation to alter the energy beam power. 
 
     
     
         6 . An additive manufacturing system according to  claim 3  wherein the processor selects one or more of the following scan patterns during the application of energy to the defect regions:
 directional rastering in which energy beam scan tracks extend back and forth in a regular hatching style pattern; 
 point exposure in which the energy beam is held at a fixed location proximate the defect region for a specified period of time; 
 nested contour loops in which the energy beam path is a contour-wise, nested rastering of discrete loops corresponding to the defect region shape; and, 
 spiral winding in which the energy beam path is a contour-wise, nested rastering of continuous loops corresponding to the defect region shape. 
 
     
     
         7 . An additive manufacturing system according to  claim 3  wherein the processor is configured to divide the defect region into a number of sub-regions and applies the energy to each of the sub-regions using different process parameters. 
     
     
         8 . An additive manufacturing system according to  claim 3  wherein the processor is configured to apply the energy to the defect region if the defect region is sufficiently proximate defect regions detected in at least one previous layer of the material. 
     
     
         9 . An additive manufacturing system according to  claim 8  wherein the processor is configured to control one or more of the process parameters during the energy input such that consolidation occurs in the previous layer as well. 
     
     
         10 . An additive manufacturing system according to  claim 3  wherein the processor is configured to detect excess energy input into the specified area and adjust process parameters for inputting energy into a specified area of a subsequent layer of the material. 
     
     
         11 . An additive manufacturing system according to  claim 3  wherein the processor is configured to access a database with the process parameters used during previous corrections of consolidation defects, and use information from the database to select the process parameters for the application of energy to the defect region. 
     
     
         12 . An additive manufacturing system according to  claim 11  wherein a plurality of like additive manufacturing systems record process parameter data into the database. 
     
     
         13 . An additive manufacturing system according to  claim 1  wherein the processor is configured to generate a record of build quality for each of the fabricated 3D objects in a two-dimensional slice form, or three-dimensional volume form, showing locations of the defect regions. 
     
     
         14 . An additive manufacturing system according to  claim 11  wherein the processor is further configured to use information from the database to automatically identify regions with higher propensity for defects from recorded defects in previously built components or particular structures, and pre-emptively vary the process parameters to avoid defect formation.