In Situ Heating Control for Residual Stress in Additive Manufacturing
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Solution Overview
Problem
Additive manufacturing processes, such as Laser Freeform Manufacturing Technology, face significant internal residual stresses and distortion due to material shrinkage, which can lead to cracking or separation from the build plate as parts increase in size, requiring frequent interruptions for external stress relief.
Innovation Solution
An integrated system with a build plate, deposition system, sensor system, and heater system that monitors and controls temperature gradients during the manufacturing process to provide in situ stress relief by heating the workpiece between the melt pool and the build plate, using multiple temperature sensors and heaters to maintain a reduced thermal gradient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the additive manufacturing part size is increased, then the manufacturing capability and productivity are improved, but the internal residual stresses and distortion increase significantly
Solution Approach 1:
The system performs preliminary stress relief heating during the additive manufacturing process itself, before the part is completed and removed from the build plate. Temperature sensors continuously monitor the part temperature, and heater elements apply heat to specific regions to prevent stress accumulation before it becomes problematic.
Solution Approach 2:
The system incorporates temperature sensors that continuously monitor the thermal state of the part during manufacturing. This feedback is used by the control system to adjust heater element operation in real-time, maintaining optimal temperature distribution to minimize thermal gradients and resulting residual stresses as the part grows in size.
2Reliability
If external stress relief operations are performed frequently to reduce internal stresses, then the reliability of the part is improved, but the manufacturing time and productivity deteriorate
Solution Approach 1:
The stress relief heating is performed continuously during the additive manufacturing process rather than requiring separate interruption cycles. The heater elements operate concurrently with material deposition, maintaining thermal conditions that prevent stress accumulation without stopping production.
Solution Approach 2:
The system performs stress relief on the part while it remains on the build plate during the manufacturing process itself. The integrated sensors and heaters enable the part to undergo stress relief treatment as an inherent part of the manufacturing process, eliminating the need for external post-processing operations.
3Reliability
If the temperature gradient between the melt pool and build plate is reduced through in situ heating, then the thermal shock and cracking risk are minimized, but the system complexity and energy consumption increase
Solution Approach 1:
The system uses selectively actuated heater elements that apply heat only to specific regions of the part where thermal gradients are most severe. Rather than heating the entire part uniformly, the system targets localized areas between the melt pool and build plate, reducing overall energy consumption while effectively mitigating stress in critical regions.
Solution Approach 2:
The heating system is integrated directly into the additive manufacturing apparatus, combining the manufacturing and stress relief functions in a single system. The heater elements are positioned within the build chamber and controlled by the same system that manages material deposition, eliminating the need for separate external stress relief 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 reduces the risk of cracking and separation by mitigating thermal shock and internal stresses, allowing for larger parts to be manufactured without interruptions, while ensuring uniform temperature distribution and effective stress relief during the additive manufacturing process.
Implementation Method 1
a heater system operable to selectively heat the workpiece between the melt pool and the build plate during the additive manufacturing
Implementation Method 2
at least one of the multiple of temperature sensors is an infrared camera
Implementation Method 3
a deposition system operable to dispense material as a melt pool to additively manufacture a workpiece on the build plate
Data Source
AI summary
An additive manufacturing system includes a build plate; a deposition system operable to dispense material as a melt pool to grow a workpiece on the build plate; a sensor system operable to determine a temperature of the workpiece being grown on the build plate adjacent to the melt pool; and a heater system operable to selectively heat the workpiece between the melt pool and the build plate.