Systems and methods for measuring radiated thermal energy during an additive manufacturing operation

Abstract

This disclosure describes various methods and apparatus for characterizing an additive manufacturing process. A method for characterizing the additive manufacturing process can include generating scans of an energy source across a build plane; measuring an amount of energy radiated from the build plane during each of the scans using an optical sensing system that monitors two discrete wavelengths associated with a blackbody radiation curve of the layer of powder; determining temperature variations for an area of the build plane traversed by the scans based upon a ratio of sensor readings taken at the two discrete wavelengths; determining that the temperature variations are outside a threshold range of values; and thereafter, adjusting subsequent scans of the energy source across or proximate the area of the build plane.

What is claimed is: 
     
         1 . An additive manufacturing method comprising:
 directing a laser at a region of a build plane to generate a melt-pool;   receiving electromagnetic energy emitted from the melt-pool with a first sensor configured to receive a first band of wavelengths and with a second sensor configured to receive a second band of wavelengths; and   calculating a temperature of the melt-pool using a ratio of an output of the first sensor to an output of the second sensor.   
     
     
         2 . The method of  claim 1  wherein the build plane comprises metallic powder that when fused by the laser emits characteristic spectral peaks. 
     
     
         3 . The method of  claim 2  wherein the first and second bands of wavelengths are each offset from the characteristic spectral peaks. 
     
     
         4 . The method of  claim 2  further comprising executing a test algorithm to determine the characteristic spectral peaks before initiating a part build sequence. 
     
     
         5 . The method of  claim 1  wherein the first and second sensors are photodiodes. 
     
     
         6 . The method of  claim 1  wherein the first and second sensors are coaxial with the laser. 
     
     
         7 . The method of  claim 1  wherein at least one of the first and second sensors are offset from an axis of the laser. 
     
     
         8 . The method of  claim 1  wherein the calculated temperature of the melt-pool is correlated with a position of the melt-pool in the build plane. 
     
     
         9 . The method of  claim 1  further comprising comparing the calculated temperature to an allowable range of temperatures and generating an alert when the calculated temperature is outside of the allowable range. 
     
     
         10 . The method of  claim 1  wherein the first sensor and the second sensor are calibrated such that they have a substantially identical response profile. 
     
     
         11 . An additive manufacturing system comprising:
 a build region;   a laser arranged to generate a melt-pool at the build region;   a first sensor arranged to receive a first band of electromagnetic energy emitted from the melt-pool;   a second sensor arranged to receive a second band of electromagnetic energy emitted from the melt-pool; and   a processor arranged to receive an output of the first sensor and an output of the second sensor, the processor further arranged to calculate a ratio of the output of the first sensor to the output of the second sensor.   
     
     
         12 . The system of  claim 11  wherein the processor is further arranged to calculate a temperature based on the ratio. 
     
     
         13 . The system of  claim 12  wherein the processor is further configured to compare the calculated temperature to an allowable range of temperatures and to generate an alert when the calculated temperature is outside of the allowable range. 
     
     
         14 . The system of  claim 12  wherein the processor is further arranged to correlate the calculated temperature with a position of the melt-pool in the build region. 
     
     
         15 . The system of  claim 11  wherein the build region comprises metallic powder that when fused by the laser emits characteristic spectral peaks. 
     
     
         16 . The system of  claim 15  wherein the first and second bands of electromagnetic energy are each offset from the characteristic spectral peaks. 
     
     
         17 . The system of  claim 15  further comprising executing a test algorithm to determine the characteristic spectral peaks before initiating a part build sequence. 
     
     
         18 . The system of  claim 11  wherein the first and second sensors are photodiodes. 
     
     
         19 . The system of  claim 11  wherein the first and second sensors are coaxial with the laser. 
     
     
         20 . The system of  claim 11  wherein at least one of the first and second sensors are offset from an axis of the laser.