Additive Manufacturing Substrate With Segmented Protrusions
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Solution Overview
Problem
Conventional additive manufacturing processes face issues with residual stresses and distortion due to thermal constraints, leading to curling and cracking of parts, especially when using thick solid substrates, which increase system complexity and can be detrimental to certain alloys.
Innovation Solution
A powder bed system with a substrate featuring protrusions or slits that allow for high strain deformation in the build plane while maintaining stiffness perpendicular to the build surface, creating a sliding constraint to accommodate material shrinkage and reduce residual stresses, and enabling the use of a 'cold' processing environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick solid substrate is used to constrain the article during sintering, then the article is constrained against thermal residual stresses, but this applies additional constraint in the x-y plane resulting in high residual stresses that cannot be relieved, leading to bending of the substrate and distortion and cracking of the article
Solution Approach 1:
The substrate is segmented into a grid of protrusions separated by gaps, transforming the continuous solid substrate into discrete elements. This segmentation allows the substrate to constrain the article in the z-axis while permitting controlled deformation in the x-y plane, relieving residual stresses without compromising constraint effectiveness.
Solution Approach 2:
The substrate geometry is changed from a solid continuous structure to a grid of protrusions with specific aspect ratios (height to width/depth). This parameter change enables the substrate to provide constraint while accommodating thermal stress through controlled deformation, resolving the contradiction between constraint and stress relief.
2Stress or pressure
If a heated sintering chamber or heated substrate is used to reduce differential shrinkage, then the level of residual stress is reduced, but this results in significant increase in system complexity requiring heat shielding of sensitive electronics and changes cooling characteristics that can have severe detrimental effect on alloys like Scalmalloy
Solution Approach 1:
The patent replaces the thermal approach (heating the substrate or chamber) with a mechanical approach (designing the substrate geometry with protrusions and gaps). This substitution achieves stress relief through controlled mechanical deformation rather than thermal management, avoiding the complexity of heat shielding and preserving beneficial cooling characteristics for sensitive alloys.
Solution Approach 2:
The invention changes the fundamental approach from thermal parameter control to geometric parameter control. By optimizing the protrusion geometry (height, width, depth, spacing), the substrate achieves stress relief functionality without requiring thermal management systems, thereby reducing device complexity.
3Stability of the object's composition
If the substrate is constrained rigidly to prevent curling, then the article remains stable during build, but this prevents relief of residual stresses during the build process
Solution Approach 1:
The substrate is divided into discrete protrusions that independently deform under stress. This segmentation allows localized stress relief at each protrusion while maintaining overall article stability, as the grid structure provides distributed constraint rather than rigid uniform constraint.
Solution Approach 2:
The substrate transitions from a static rigid structure to a dynamic structure where protrusions can deform in response to thermal stresses. This dynamic capability allows the substrate to adapt to stress conditions during the build process, relieving residual stresses while maintaining article stability through the overall grid configuration.
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
The substrate design effectively reduces residual stresses and distortion, allowing for larger part builds without curling or cracking, while maintaining the benefits of a simpler, ambient-temperature processing environment that is suitable for various materials, including alloys like Scalmalloy.
Implementation Method 1
The larger the aspect ratio of the protrusions, for a given material, the greater their ability to deform as beams in the plane of the build surface
Implementation Method 2
A known ALM technique uses a power beam, such as a laser or an electron beam for example, to selectively sinter powdered material
Implementation Method 3
The power beam is used to selectively sinter the powder in a desired pattern by scanning across the surface of the powder bed
Implementation Method 4
After each cross-section is scanned and the melted powder has solidified
Data Source
Figure 1
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AI summary
A substrate for an additive manufacturing process, the substrate having a build surface for fusing to a part being formed on the substrate by the additive manufacturing process, wherein the substrate is configured to provide relatively high stiffness in a direction substantially perpendicular to the build surface, whilst having a low longitudinal stiffness in the plane of the build surface. Also, a method of forming the substrate, a system including the substrate, and use of the system for creating a part by an additive manufacturing process.