Controlling heat sources based on representative temperatures

Abstract

In an example, a method includes measuring a temperature of a plurality of regions of a layer of build material in an additive manufacturing apparatus to provide initial temperature values. For each of a plurality of regions which comprise build material which is intended to fuse, an average temperature value of a plurality of neighbouring regions may be determined and the initial temperature values may be replaced with the average temperature value. Based on the replacement temperature values, a representative temperature of an area of the layer of build material may be determined and a heat source may be controlled based on the representative temperature.

1 . Additive manufacturing apparatus comprising processing circuitry, the processing circuitry comprising:
 a temperature determination module to determine a representative temperature value for a layer of build material by replacing measured temperature values of pixels from a plurality of regions of a heat map of the layer which comprise build material which is intended to fuse with average temperatures of neighboring pixels; and   a controller, to control a heat source based on the representative temperature value for a layer of build material.   
     
     
         2 . Additive manufacturing apparatus of  claim 1 , in which the temperature determination module is to determine a plurality of representative temperatures for different zones of the layer, and the controller is to control each of a plurality of heat sources based on the representative temperature value for a zone associated with that heat source. 
     
     
         3 . Additive manufacturing apparatus of  claim 2 , further comprising a plurality of heat sources. 
     
     
         4 . A machine readable medium comprising instructions which, when executed by a processor, cause the processor to:
 identify, from a heat map of a layer of build material in an additive manufacturing apparatus comprising a plurality of pixels, pixels which are directly indicative of a temperature of the layer in the absence of applied print agent;   for a plurality of pixels indicative of a temperature of a plurality of regions of the layer to be fused, determine an average temperature value of a plurality of neighbouring regions;   determine, based on the pixels which are directly indicative of a temperature of the layer in the absence of applied print agent and the determined average temperature values, a representative temperature of an area of the layer of build material; and   control a heat source based on the representative temperature.   
     
     
         5 . A machine readable medium of  claim 4 , wherein the instructions to identify the pixels which are directly indicative of a temperature of the layer in the absence of applied print agent comprise instructions to identify the pixels based on data modelling a content of a fabrication chamber. 
     
     
         6 . A machine readable medium of  claim 4 , wherein the instructions to determine an average temperature value comprise, for at least one pixel which is not directly indicative of a temperature of the layer in the absence of applied print agent, instructions to determine a first average temperature value of a first plurality of neighbouring regions and a second average temperature value of a second plurality of neighbouring regions. 
     
     
         7 . A machine readable medium of  claim 4 , further comprising instructions to determine a size of a continuous set of pixels which are not directly indicative of a temperature of the layer in the absence of applied print agent; and
 when the area is below a threshold size, to determine the average temperature values, and, when the area is at least a threshold size, to use a linear regression and a predicted heat of each region to determine a representative temperature.   
     
     
         8 . An additive manufacturing apparatus comprising:
 An array of temperature sensors for measuring a temperature of a plurality of regions of a layer of build material in an additive manufacturing apparatus to provide initial temperature values;   processing circuitry comprising a temperature determination module for
 determining, for each of a plurality of regions which comprise build material which is intended to fuse, an average temperature value of a plurality of neighboring regions, 
 replacing the initial temperature values with the average temperature values, and 
 determining, based on the replacement temperature values, a representative temperature of an area of the layer of build material; and 
   a controller for controlling a heat source based on the representative temperature.   
     
     
         9 . The additive manufacturing apparatus of  claim 8 , wherein the temperature determination module is programmed to determine the representative temperature using:
 a first iteration, for a plurality of regions, determining a first replacement temperature value comprising an average value of neighboring regions on a first and second side of a region; and   a second iteration, for a plurality of regions, determining a second replacement temperature value comprising an average value of neighboring regions on a third and fourth side of a region,   wherein the representative temperature is based on the second replacement temperature values.   
     
     
         10 . The additive manufacturing apparatus of  claim 8 , wherein the temperature determination module is further programmed for:
 determining an indication of a size of a continuous area of the layer of build material which comprises build material which is intended to fuse, and   determining the replacement temperature values for the area when it is determined that the continuous area is below a threshold size.   
     
     
         11 . The additive manufacturing apparatus of  claim 10 , further comprising, when the temperature determination module determines that the continuous area is above a threshold size, the temperature determination module is programmed to use a linear regression and a predicted heat of each region based on data indicating portions of the layer which are intended to fuse to estimate the representative temperature. 
     
     
         12 . The additive manufacturing apparatus of  claim 8 , wherein the average temperatures value is a weighted average, wherein at least one weighting is indicative of whether the temperature value of a neighboring region is an initial value or a replacement value. 
     
     
         13 . The additive manufacturing apparatus of  claim 12 , wherein the weighting is indicative of how many initial values were used in determining a replacement value of that region. 
     
     
         14 . The additive manufacturing apparatus of  claim 8 , wherein the temperature determination module is further programmed to:
 determine, for each of a plurality of regions which are in a boundary zone of the layer, an average temperature value of a plurality of neighboring regions; and   replace the initial temperature values with the average temperature values,   wherein determining, based on the replacement temperature values, a representative temperature of an area of the layer of build material comprises determining the temperature based on the replacement temperature values of the regions in the boundary zone.   
     
     
         15 . The additive manufacturing apparatus of  claim 8 , wherein:
 the temperature determination module is programmed to determine a representative temperature for each of a plurality of print bed zones; and   the controller is programmed to control a plurality of heat sources based on the representative temperature of an associated print bed zone.   
     
     
         16 . The additive manufacturing apparatus of  claim 8 , wherein the temperature determination module is programmed to determine each pixel of a thermal image of the layer of build material is used as a region for which the average temperature value of a plurality of neighboring regions, an initial temperature value for a number of the pixels being replaced with such an average temperature value. 
     
     
         17 . The additive manufacturing apparatus of  claim 16 , f wherein the temperature determination module is programmed to determine an average temperature value to replace an initial temperature value for each pixel in a sweep pattern from a first corner of the thermal image to an opposite corner of the thermal image. 
     
     
         18 . The additive manufacturing apparatus of  claim 8 , wherein each area for which a representative temperature is determined comprises a plurality of the regions for which a replacement temperature is determined, each area corresponding to a different heat source among a plurality of heat sources. 
     
     
         19 . The additive manufacturing apparatus of  claim 8 , wherein temperature determination module is further programmed to determine each of the plurality of regions which comprise build material which is intended to fuse using control data that instructs distribution of print agents. 
     
     
         20 . The additive manufacturing apparatus of  claim 19 , wherein temperature determination module is further programmed to perform a second iteration of determining an average temperature value to replace a current temperature value for each pixel in a second sweep pattern from the opposite corner of the thermal image back to the first corner of the thermal image.