Pixel Grid Orientation Control for Stereolithography Edge Alignment
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Solution Overview
Problem
In pixel-based additive manufacturing, such as stereolithography, the edge of the cured area often misaligns with the intended border due to the inherent square or rectangular shape of pixels, leading to 'stair stepping' errors, which cannot be fully eliminated regardless of pixel size.
Innovation Solution
The method involves independently setting the angular orientation of each build layer to align the edges of pixels with the workpiece edges by rotating the projector and platform about the build axis, allowing for a preferred angular orientation that minimizes stair stepping and optimizes pixel alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pixels are made smaller to reduce stair stepping, then manufacturing precision improves, but device complexity increases and productivity decreases
Solution Approach 1:
The patent changes the angular orientation parameter of the pixel grid relative to the workpiece edges. By rotating the pixel grid to specific angles (e.g., 45 degrees) or using non-uniform scaling, the invention achieves better edge alignment without reducing pixel size, thus maintaining build speed while improving manufacturing precision.
2Manufacturing precision
If pixels are made smaller to reduce stair stepping, then manufacturing precision improves, but device complexity increases
Solution Approach 1:
Instead of reducing pixel size, the invention changes the angular orientation and/or aspect ratio parameters of the pixel grid. This allows achieving sub-pixel edge alignment precision while maintaining the same physical pixel dimensions, thereby avoiding the need for higher resolution projectors and reducing device complexity.
3Manufacturing precision
If angular orientation is independently controlled for each layer, then manufacturing precision improves, but device complexity increases
Solution Approach 1:
The patent implements dynamic angular orientation control where the pixel grid angle can be independently adjusted for each layer or group of layers. This dynamic adjustment capability allows optimization of edge alignment for different geometries while maintaining a relatively simple implementation through software-controlled projector rotation or platform rotation.
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 enhances the fidelity and surface quality of manufactured components by ensuring precise alignment of pixels with workpiece edges, reducing variability and stair stepping, and increasing the ability to produce complex geometries, thereby lowering part costs and improving yield.
Implementation Method 1
Stereolithography is a type of additive manufacturing process which employs a vat of liquid ultraviolet ('UV') curable photopolymer 'resin' and an image projector to build components one layer at a time. Exposure to the ultraviolet light cures and solidifies the pattern in the resin
Data Source
AI summary
A method of making a workpiece in an additive manufacturing process includes determining a preferred angular orientation of the grid array about a build axis extending perpendicular to a layer to be built for a first layer of a workpiece. The preferred angular orientation is selected to align an edge of one or more pixels with an edge of the layer of the workpiece being built. The method further includes orienting a patterned image of radiant energy to the preferred angular orientation by rotating a projector before solidifying a portion of a resin that forms the first layer of the workpiece.