LMD Process Control for Prefabricating Poor Fusion Defects
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Solution Overview
Problem
Current methods for prefabricating poor fusion defects in additive manufacturing (AM) processes, such as laser melting deposition (LMD), fail to accurately simulate the defects generated in the actual solidification process, leading to incomplete representation of structural characteristics and mechanical property impacts, which hampers the evaluation of defect reliability in AM parts, especially in aerospace applications.
Innovation Solution
A method is developed to control the LMD process by adjusting shaping process parameters, including scan pitch, powder feed rate, and laser energy input, to prefabricate poor fusion defects with specific dimensions and positions, ensuring continuous and complete structural characteristics, and simulating the defects generated in the actual solidification process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the welding process is controlled to create poor fusion defects, then defects with certain dimensions can be generated, but the structure and properties of the samples are damaged to varying degrees
Solution Approach 1:
The patent applies preliminary action by designing and embedding poor fusion defects into the 3D model before the additive manufacturing process. The defect model is created in advance with precise dimensional control, and then manufactured as an integral part of the sample through LMD or SLM processes, avoiding post-processing damage to sample structure and properties.
2Ease of manufacture
If selective laser melting is used to design poor fusion defect contours, then parts with poor fusion defects can be directly shaped, but the defects do not have a continuous structure and are only applicable for partial poor fusion defects
Solution Approach 1:
The patent applies parameter changes by systematically varying LMD process parameters (laser power, scanning speed, hatch spacing, powder feed rate) to control the formation and characteristics of poor fusion defects. This enables precise control over defect dimensions, shape, and structural continuity, allowing defects to accurately represent actual manufacturing conditions.
3Manufacturing precision
If the dimension of poor fusion defects is small, then the defects can be precisely controlled, but they are easily filled by the molten metal at the boundary contour
Solution Approach 1:
The patent applies local quality by implementing localized process parameter optimization in the defect regions during LMD manufacturing. Different parameters (lower laser power, adjusted scanning speed, modified hatch spacing) are applied specifically to areas where poor fusion defects are intended, while maintaining optimal parameters in non-defect areas. This ensures small defects are formed with precise dimensional control while preventing them from being filled by molten metal from boundary contours.
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 enables the accurate prefabrication of poor fusion defects, improving the detection and analysis of their impact on mechanical properties and reliability, enhancing the evaluation and application of AM parts in critical fields like aerospace.
Implementation Method 1
uses a high-energy laser beam to melt the synchronously transported and collected metal powder to form a moving unsteady metal molten pool
Implementation Method 2
uses a high-energy laser beam to melt the synchronously transported and collected metal powder
Implementation Method 3
The small molten pool solidifies rapidly under high temperature gradient
Implementation Method 4
solidifies rapidly under high temperature gradient
Implementation Method 5
LMD technology (e.g. by means of synchronous powder feeding) is a common AM technology
Data Source
AI summary
A method for prefabricating a poor fusion defect by controlling a LMD process, including: obtaining a model, with a shaping zone and a defect prefabricated zone that has a preset defect; and performing a layerwise slicing process on the model. For each deposition layer of the defect prefabricated zone, the preset defect has a maximum dimension a0 in a perpendicular direction; for the shaping zone, performing a shaping process under predetermined shaping process parameters of the LMD process; and for the defect prefabricated zone, controlling shaping process parameters as follows: when a0<D, with respect to the shaping zone, changing a scan pitch between shaping paths and a powder feed rate in the deposition layer, thereby prefabricating the poor fusion defect; and when a0≥D, with respect to the shaping zone.