Correction of non-imaging thermal measurement devices
A system and a corresponding method of correcting temperature data from a non-imaging optical sensor involve collecting temperature data generated using the optical sensor. The temperature data describes temperature changes across a surface of a material during an additive manufacturing operation in which the material is heated by a heat source. The method includes estimating a size of a hot spot corresponding to a hottest region formed on the surface by the heat source; and estimating a size of a heated region corresponding to a locus of points within the field of view that contribute to the temperature data. The method further includes correcting the temperature data based on the estimated sizes of the hot spot and the heated region.
1. An additive manufacturing method, comprising:
heating a powder distributed across a powder bed, using a heat source;
measuring temperature across a surface of the powder bed using a non-imaging optical sensor having a defined field of view;
estimating an area of a hot spot corresponding to a hottest region formed on the surface by the heat source;
estimating an area of a heated region corresponding to a locus of points within the field of view that contribute to the measured temperature, wherein the estimate tracks changes in the area of the heated region caused by temporal and spatial variations in operating parameters of the heat source; and
scaling the measured temperature by a correction factor calculated based on a ratio of the estimated area of the hot spot and the estimated area of the heated region.
2. The additive manufacturing method of claim 1 , wherein the correction factor is
φ
CORRECTION
=
A
HEATED
REGION
A
HOT
SPOT
,
where A HEATED REGION is the estimated area of the heated region and A HOT SPOT is the estimated area of the hot spot.
3. The additive manufacturing method of claim 1 , further comprising:
applying operating parameters of the heat source and physical properties of the powder as inputs to a model that estimates a thermal field that describes, as a function of space and time, a temperature distribution produced in the powder by the heat source.
4. The additive manufacturing method of claim 3 , further comprising:
estimating the area of the heated region by calculating radiated power for different points within the thermal field, and identifying points for which the radiated power is within a specified proportion of a peak radiated power of the thermal field.
5. An additive manufacturing method comprising:
depositing a layer of powder;
fusing one or more regions of the layer of powder using a heat source;
collecting temperature data describing temperature changes across a surface of the layer of powder during the fusing, wherein the temperature data is generated using a non-imaging optical sensor having a defined field of view;
estimating a size of a hot spot corresponding to a hottest region formed on the layer of powder by the heat source;
estimating a size of a heated region corresponding to a locus of points within the field of view that contribute to the temperature data; and
correcting the temperature data, wherein the correcting is performed by scaling the temperature data by a correction factor that is based on a ratio of the estimated size of the hot spot and the estimated size of the heated region.
6. The additive manufacturing method of claim 5 , wherein the size of the hot spot is estimated to be equal to a size of an energy beam output by the heat source.
7. The additive manufacturing method of claim 5 , further comprising:
estimating a thermal field that describes, as a function of space, a temperature distribution produced in the layer of powder by the heat source.
8. The additive manufacturing method of claim 7 , wherein the heated region is estimated by calculating radiated power for different points within the thermal field, and identifying points for which the radiated power is within a specified proportion of a peak radiated power of the thermal field.
9. The additive manufacturing method of claim 7 , wherein the thermal field is estimated as a function of space and time based on operating parameters of the heat source and physical properties of the layer of powder.
10. The additive manufacturing method of claim 9 , wherein the operating parameters include at least one of a power output of the heat source, a travel speed of the heat source, a scan pattern of the heat source, a spatial orientation of the heat source relative to the layer of powder, or a size of an energy beam output by the heat source, and wherein the physical properties include at least one of a density of the layer of powder or a thermal conductivity of the layer of powder.
11. The additive manufacturing method of claim 5 , wherein the temperature data is corrected by scaling an observed temperature by a correction factor
φ
CORRECTION
=
A
HEATED
REGION
A
HOT
SPOT
,
where A HEATED REGION is an estimated area of the heated region and A HOT SPOT is an estimated area of the hot spot.
12. The additive manufacturing method of claim 5 , wherein the optical sensor is a photodiode or a pyrometer.
13. An additive manufacturing system, comprising:
a heat source;
a layer of powder;
a non-imaging optical sensor configured to measure temperatures across a surface of the layer of powder during an additive manufacturing operation in which the layer of powder is heated by the heat source, wherein the optical sensor has a defined field of view; and
at least one processor configured to collect temperature data from the optical sensor, the at least one processor being further configured to:
estimate a size of a hot spot corresponding to a hottest region formed on the layer of powder by the heat source;
estimate a size of a heated region corresponding to a locus of points within the field of view that contribute to the temperature data; and
correct the temperature data by scaling the temperature data with a correction factor that is based on a ratio of the estimated size of the hot spot and the estimated size of the heated region.
14. The additive manufacturing system of claim 13 , wherein the at least one processor estimates the size of the hot spot to be equal to a size of an energy beam output by the heat source.
15. The additive manufacturing system of claim 13 , wherein the at least one processor is configured to estimate a thermal field that describes, as a function of space, a temperature distribution produced in the layer of powder by the heat source.
16. The additive manufacturing system of claim 15 , wherein the at least one processor estimates the heated region by calculating radiated power for different points within the thermal field, and identifying points for which the radiated power is within a specified proportion of a peak radiated power of the thermal field.
17. The additive manufacturing system of claim 15 , wherein the at least one processor is configured to estimate the thermal field as a function of space and time based on operating parameters of the heat source and physical properties of the layer of powder.
18. The additive manufacturing system of claim 17 , wherein the operating parameters include at least one of a power output of the heat source, a travel speed of the heat source, a scan pattern of the heat source, a spatial orientation of the heat source relative to the layer of powder, or a size of an energy beam output by the heat source, and wherein the physical properties include at least one of a density of the layer of powder or a thermal conductivity of the layer of powder.
19. The additive manufacturing system of claim 13 , wherein the at least one processor corrects the temperature data by scaling a measured temperature by a correction factor
φ
CORRECTION
=
A
HEATED
REGION
A
HOT
SPOT
,
where A HEATED REGION is an estimated area of the heated region and A HOT SPOT is an estimated area of the hot spot.
20. The additive manufacturing system of claim 13 , wherein the optical sensor is a photodiode or a pyrometer.