LPBF Supplemental Surface Heating for Microstructure and Stress Control
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Solution Overview
Problem
Laser powder bed fusion (LPBF) processes face significant challenges in controlling residual stresses and microstructure formation due to high temperature gradients, leading to mechanical property issues and potential cracking in additive manufactured parts, with existing methods being inefficient or requiring additional costly equipment.
Innovation Solution
An additive manufacturing system incorporating a supplemental heating subsystem that generates a wide area beam with controlled intensity to alter the microstructure and relieve stresses in the part, either before, during, or after the fusing process, using a computer-controlled primary and supplemental heat generating system, along with a beam steering and mask subsystem to precisely manage thermal history.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser powder bed fusion is used to manufacture parts, then manufacturing capability and productivity are improved, but residual stresses and microstructure control deteriorate due to high temperature gradients
Solution Approach 1:
The system applies preliminary heating to the powder bed before laser fusing to establish a controlled thermal baseline. This pre-heating action reduces the thermal shock and temperature gradient when the laser subsequently melts the powder, thereby controlling microstructure formation while maintaining manufacturing productivity
Solution Approach 2:
The system dynamically adjusts heating parameters including temperature, heating rate, and spatial distribution of heat during the manufacturing process. By changing these thermal parameters in real-time, the system optimizes both the manufacturing capability and the microstructure quality of the produced parts
2Productivity
If laser powder bed fusion is used to manufacture parts, then manufacturing capability is improved, but residual stresses increase leading to cracking and mechanical failure
Solution Approach 1:
The system performs preliminary heating of the powder bed and build plate before and during laser fusing to prevent excessive temperature gradients. This preliminary thermal conditioning reduces the formation of harmful residual stresses that would otherwise lead to cracking and part failure, thereby improving reliability while maintaining manufacturing capability
Solution Approach 2:
The system converts the inherently high temperature gradients of laser powder bed fusion from a harmful effect into a beneficial one by using controlled supplemental heating. The supplemental heat source transforms the abrupt thermal cycling into a more gradual, controlled thermal profile that reduces residual stresses while maintaining the productivity benefits of LPBF
3Reliability
If post-annealing is used to remove residual stresses, then residual stress is reduced, but processing time and equipment requirements increase
Solution Approach 1:
The system performs residual stress relief during the manufacturing process itself through integrated supplemental heating, eliminating the need for separate post-annealing operations. The build plate and chamber heating capabilities provide in-situ stress relief, saving considerable time and removing the need for additional post-processing equipment
4Manufacturing precision
If in-situ supplemental heating is used to control temperature gradients, then microstructure and residual stress control are improved, but device complexity increases
Solution Approach 1:
The system uses the build plate and chamber heating subsystems, which are already necessary for basic LPBF operation, to also provide supplemental heating for temperature gradient control. By making these existing components multi-functional, the system achieves improved microstructure control without adding significant complexity or requiring separate dedicated heating equipment
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for precise control over microstructure and residual stress formation, reducing thermal gradients and improving mechanical properties by controlling the thermal history of the part, resulting in reduced residual stresses and enhanced part quality without the need for extensive post-processing or costly equipment.
Implementation Method 1
A supplemental heating subsystem is included for generating a wide area beam to heat a portion of the powder layer
Implementation Method 2
The fusing beam is used for heating and fusing at least one of select portions of a powder layer
Implementation Method 3
The wide area beam has an intensity which is insufficient to fuse the powder and operates to alter a microstructure of the powder layer as the powder layer is at least one of fused, or as the powder layer cools
Implementation Method 4
The wide area beam has an intensity which is insufficient to fuse the powder and operates to alter a microstructure of the powder layer as the powder layer is at least one of fused, or as the powder layer cools, to relieve stress in the part
Data Source
AI summary
The present disclosure relates to an additive manufacturing system for forming a part using a powder material. In one embodiment the system makes use of a primary heat generating subsystem to generate a fusing beam for heating and fusing at least one of select portions of a powder layer, or an entire area of a powder layer, deposited on a build plate. The system also incorporates a beam steering subsystem for steering the fusing beam over the powder layer. A supplemental heating subsystem is used to generate a wide area beam to heat a portion of the powder layer either prior to fusing, along with the fusing operation, or subsequent to fusing of the powder with the fusing beam. The wide area beam has an intensity which is insufficient to fuse the powder, and alters a microstructure of the powder layer as the powder layer is at least one of fused or as it cools, to thus relieve stress in the part.