US-12623288-B2 - Predictive defect model for highly productive laser powder bed fusion additive manufacturing

Abstract

This disclosure is directed to a method for modeling additive manufacturing of a part, including a number of steps. The steps include constructing a model for estimating output of a simulated additive manufacturing process, followed by entering process operating parameters for an additive manufacturing system into the model to produce an output. The output is compared to acceptance criteria to determine whether the output is acceptable or unacceptable. Next regions of operating parameters that support production of the part with acceptable quality characteristics are determined based upon the output. Regions of operating parameters that support production of the part with acceptable quality characteristics are added to a process map for additive manufacturing the part. The steps are repeated for different operating parameters until the process map is complete.

Inventors

• Parisa Farahmand
• Masoud Anahid

Assignees

• RAYTHEON TECHNOLOGIES CORPORATION

Dates

Publication Date

20260512

Application Date

20230525

Claims (20)

1. 1 . A method for modeling additive manufacturing of a part, comprising the steps of: (i) constructing a model for estimating output of a simulated additive manufacturing process based upon powder composition, part design, physical properties of a melt pool channel, Bernoulli's equation, energy and mass conservation equations, a laser attenuation coefficient that represents a power loss ratio of the laser to its incident power on a powder bed, wherein the laser attenuation coefficient is a function of recoil pressure, vapor jet velocity and temperature and vapor-driven gas flow; (ii) entering process operating parameters for an additive manufacturing system into the model to produce an output as a defect status, wherein the operating parameters include: (1) laser beam spot size, build plate temperature, and layer thickness; (2) temperature-dependent thermophysical properties of the powder; (3) feedstock properties including average powder particle size; and (4) laser hatching strategy including hatch distance, hatch delay time, and stripe width; (iii) comparing the output to acceptance criteria to determine whether the output is acceptable or unacceptable; (iv) determining, based upon the output, regions of operating parameters that support production of the part with acceptable quality characteristics; (v) adding regions of operating parameters that support production of the part with acceptable quality characteristics to a process map for additive manufacturing the part; and (vi) repeating steps (ii) through (v) for different operating parameters until the process map is complete, wherein the complete process map includes: (1) at least one single-track map that indicates regions for an unstable melt pool; and (2) at least one single-stripe map that indicates regions for vapor-induced lack-of-fusion defects.
2. 2 . The method of claim 1 , wherein the acceptable quality characteristics include at least one of residual stress, microstructure, porosity, crack propensity of the part.
3. 3 . The method of claim 1 , wherein the part is a complex near-net-shaped part.
4. 4 . The method of claim 1 , wherein the physical properties of a melt pool channel are computed based a radius and length of the melt pool channel and backward flow velocity in the melt pool channel, wherein the radius, length and backward flow velocity of the melt pool channel are expressed as functions of laser power and scan speed.
5. 5 . The method of claim 1 , further comprising using the process map to produce a physical part on a powder bed fusion additive manufacturing (LPBF) system.
6. 6 . The process of claim 5 , further comprising validating and calibrating the process model based upon characteristics of the physical part.
7. 7 . The method of claim 1 , wherein unacceptable output is not added to the process map.
8. 8 . The method of claim 1 , wherein unacceptable output is added to the process map to set boundaries related to unacceptable parts.
9. 9 . The method of claim 1 , wherein the operating parameters comprise laser power and laser scan speed.
10. 10 . The method of claim 1 , wherein the part is produced from an alloy.
11. 11 . A method for additive manufacturing of a part, comprising entering a part design into an additive manufacturing system programmed with a process map developed from the method of claim 1 and producing a part according to the part design and the process map.
12. 12 . The method of claim 11 , wherein the part is a complex near-net-shaped part.
13. 13 . The method of claim 11 , wherein the part is produced from an alloy.
14. 14 . The method of claim 11 , wherein the process map defines regions of additive manufacturing system operating parameters that produce parts with acceptable quality characteristics.
15. 15 . The method of claim 14 , wherein the operating parameters comprise laser power and laser scan speed.
16. 16 . A system for additive manufacturing of a part, comprising an additive manufacturing system comprising a control unit programmed with a process map developed from the method of claim 1 wherein the control unit is further programmed to operate an additive manufacturing machine at process parameters within the process map.
17. 17 . The system of claim 16 , wherein the part is a complex near-net-shaped part.
18. 18 . The system of claim 16 , wherein the part is produced from an alloy.
19. 19 . The system of claim 16 , wherein the process map defines regions of additive manufacturing system operating parameters that produce parts with acceptable quality characteristics.
20. 20 . The system of claim 19 , wherein the operating parameters comprise laser power and laser scan speed.

Description

BACKGROUND The present disclosure relates generally to laser powder bed fusion additive manufacturing and, more particularly, to a method of modeling a laser powder bed fusion additive manufacturing process to determine operating regions that support high productivity operations. Laser powder bed fusion (LPBF) additive manufacturing is an additive manufacturing, or 3-D printing, technology that uses a laser to sinter or fuse metallic or polymeric particles together in a layer-by-layer process. LPBF is typically used as an industrial process to make near net shape parts. Some LPBF processes sinter the powder particles, while others melt and fuse the powder particles. LPBF is also known as direct metal laser sintering (DMLS). Similar to other additive manufacturing processes, an operator loads a 3-D CAD file of a desired part into the LPBF machine before the manufacturing process begins. The process usually starts by heating a powder bed to a desired temperature. A laser then scans the powder bed to fuse a first layer of the part. The scanned laser sinters or fuses the powder particles to form a solid shape. The LPBF machine then distributes a new layer of powder over the completed first layer of the part and the laser scans the powder bed to form the next layer of the part on top of the completed first layer of the part. This process continues, layer-by-layer, until the part is completed. A LPBF process like this can produce high quality, defect-free parts, but the time required to make parts, particularly complicated parts, can be very long resulting in low productivity. Accordingly, there have been many efforts to find approaches to increase the rate of production on LPBF machines. One way to increase the rate of production in a LPBF process is to the increase the speed of the laser scan across the bed. This requires increasing the laser power as well to provide sufficient laser energy input to the powder bed. Increasing scan speed and laser power, however, can create instability in the melt pool and flaws in the parts made with the LPBF process. On large format parts, finding defects after the part is built results in time lost and materials wasted. SUMMARY One aspect of this disclosure is directed to a method for modeling additive manufacturing of a part, including the steps of: (i) constructing a model for estimating output of a simulated additive manufacturing process; (ii) entering process operating parameters for an additive manufacturing system into the model to produce an output as a defect status; (iii) comparing the output to acceptance criteria to determine whether the output is acceptable or unacceptable; (iv) determining, based upon the output, regions of operating parameters that support production of the part with acceptable quality characteristics; (v) adding regions of operating parameters that support production of the part with acceptable quality characteristics to a process map for additive manufacturing the part; and (vi) repeating steps (ii) through (v) for different operating parameters until the process map is complete. The model for estimating output of a simulated additive manufacturing process is based upon powder composition, part design, physical properties of a melt pool channel, Bernoulli's equation, energy and mass conservation equations, a laser attenuation coefficient that represents a power loss ratio of the laser to its incident power on a powder bed, wherein the laser attenuation coefficient is a function of recoil pressure, vapor jet velocity and temperature and vapor-driven gas flow. The operating parameters include (1) laser beam spot size, build plate temperature, and layer thickness; (2) temperature-dependent thermophysical properties of the powder; (3) feedstock properties including average powder particle size; and (4) laser hatching strategy including hatch distance, hatch delay time, and stripe width. The output includes: (1) at least one single-track map that includes regions for an unstable melt pool; and (2) at least one single-stripe map that includes regions for vapor-induced lack-of-fusion defects. Another aspect of this disclosure is directed to a method for additive manufacturing of a part. A part design is entered into an additive manufacturing system programmed with a process map. The process map is developed from a model for estimating output of a simulated additive manufacturing process and operating parameters for the additive manufacturing system. The model is based upon powder composition, part design, physical properties of a melt pool channel, Bernoulli's equation, energy and mass conservation equations, a laser attenuation coefficient that represents a power loss ratio of the laser to its incident power on a powder bed, wherein the laser attenuation coefficient is a function of recoil pressure, vapor jet velocity and temperature and vapor-driven gas flow. The operating parameters include (1) laser beam spot size, build plate temperature, and l