Additive Fabrication Layer Separation Force Control
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Solution Overview
Problem
Additive fabrication techniques, such as stereolithography, face challenges in minimizing separation forces during layer separation, which can cause deformation, mechanical failure, incomplete curing, and structural instability due to non-homogeneities and insufficient curing of photopolymer resin.
Innovation Solution
An optimized process that includes calculating and applying forces in the x- and z-directions based on the geometry and properties of the layer being formed, with a cure delay period and a preload force to separate the layer from the container, while considering factors like overhangs, fragility, and wear degree of the resin container.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If separation force is applied to remove the layer from the container, then the layer can be separated from the container, but deformation and mechanical failure occur due to excessive force
Solution Approach 1:
The system dynamically adjusts the magnitude and direction of separation forces based on real-time monitoring of layer properties, container wear degree, and overhang geometry. This dynamic adaptation allows the separation force to be optimized for each specific situation, preventing both excessive force that causes deformation and insufficient force that fails to separate the layer.
Solution Approach 2:
The system changes multiple parameters simultaneously including force magnitude, force direction, cure delay duration, and preload force magnitude. By adjusting these parameters based on layer geometry and container wear, the system achieves effective separation while minimizing structural damage to the fabricated object.
2Strength
If actinic radiation is applied to cure the photopolymer resin, then the layer adheres to the build platform and previous layers, but incomplete curing occurs leading to structural instability
Solution Approach 1:
The system applies a preload force to the layer before actinic radiation curing is complete. This preliminary mechanical action ensures proper contact between the layer and the build platform, promoting uniform curing and preventing structural instability that would result from incomplete adhesion.
Solution Approach 2:
The curing process is made continuous by applying actinic radiation while simultaneously applying preload force and maintaining proper layer positioning. This continuous action ensures complete curing without interruption, preventing structural instability.
3Shape
If the layer geometry includes overhangs, then the fabricated object achieves complex shapes, but larger separation forces are required causing deformation
Solution Approach 1:
The system applies separation forces selectively based on the local geometry of each layer. Areas with overhangs receive different force magnitudes and directions compared to flat areas, optimizing separation while minimizing deformation of the complex geometric features.
Solution Approach 2:
The separation force parameters are dynamically adjusted according to the specific overhang geometry of each layer. This allows the system to handle complex shapes by adapting the separation process to the local geometric requirements rather than using a fixed force approach.
4Productivity
If the resin container is used repeatedly, then productivity is maintained, but wear degree increases leading to adhesion problems
Solution Approach 1:
The system continuously monitors the wear degree of the resin container and uses this information to adjust separation force parameters and cure delay duration. This feedback mechanism compensates for container wear, maintaining consistent adhesion quality and fabrication reliability over repeated use.
Solution Approach 2:
The system changes separation force magnitude and cure delay parameters based on the container's wear degree. As the container wears, the system adapts these parameters to maintain optimal adhesion and separation performance, ensuring consistent productivity and reliability.
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 minimizes deformation and mechanical failure, ensures complete curing, and enhances the structural integrity and precision of the fabricated object by dynamically determining and applying forces tailored to the specific geometry and properties of each layer.
Implementation Method 1
Exposure to actinic radiation cures a thin layer of liquid resin, which causes it to harden and adhere to previously cured layers or to the bottom surface of the build platform
Implementation Method 2
separating the first layer from the container by applying the calculated one or more forces to the first layer
Data Source
AI summary
According to some aspects, a method of additive fabrication is provided wherein a plurality of layers are formed on a build platform, each layer contacting a container in addition to the build platform and/or a previously formed layer, the method comprising calculating, using at least one processor, one or more forces to be applied to a first layer of the plurality of layers subsequent to the first layer being formed, said calculating being based at least in part on a determined area of at least one portion of the first layer that overhangs a second layer of the plurality of layers, forming the first layer, the first layer being in contact with the container and in contact with a previously formed layer of the plurality of layers, and separating the first layer from the container by applying the calculated one or more forces to the first layer.