Transparent Confining Element Thickness for Photopolymerization Accuracy
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Solution Overview
Problem
In photopolymerization-based 3D printing, the use of diffusely reflecting materials with varying refractive indices leads to light redistribution and attenuation, causing geometry errors in the solidified layers due to total internal reflection and diffuse reflection, resulting in inaccuracies such as magnification, cavity misalignment, and fusion of separate parts.
Innovation Solution
Adapting the thickness of the transparent material confining element and the coated surface to minimize the reflection of radiation back into the material, with the thickness of the confining element being at least ¼ to ½ of the diameter of the coated surface, and using antireflection or radiation-absorbing properties on the side walls to reduce total internal reflection and enhance image contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a diffusely reflecting material with varying refractive indices is used for additive manufacturing, then the material can be cured by position-selective radiation, but light redistribution and attenuation occur causing geometry errors in the solidified layers
Solution Approach 1:
The patent changes the optical parameters of the system by introducing a transparent material confining element with specific optical properties (low refractive index, antireflection coating) to control light propagation. This modifies how radiation interacts with the diffusely reflecting material, reducing unwanted light redistribution while maintaining the ability to cure layers position-selectively.
Solution Approach 2:
The transparent material confining element acts as an intermediary between the radiation source and the photopolymerizable material. It mediates the light transmission by reducing total internal reflection and diffuse reflection, thereby controlling the radiation distribution that reaches the material and improves geometry accuracy during layered construction.
2Device complexity
If the transparent material confining element has small thickness, then the device is simpler and more transparent, but total internal reflection causes significant radiation to be reflected back into the material reducing image contrast
Solution Approach 1:
The patent optimizes the thickness parameter of the transparent material confining element to a specific range (0.5-5 mm) where it is thick enough to reduce total internal reflection and improve image contrast, yet thin enough to maintain simplicity and transparency. This parameter optimization resolves the contradiction between device simplicity and image quality.
Solution Approach 2:
The transparent material confining element is designed as a composite structure combining a transparent base material (acrylic, polycarbonate, or glass) with an antireflection coating layer. This composite structure provides both the mechanical stability needed for the confining element and the optical properties to minimize total internal reflection, improving image contrast without significantly increasing complexity.
3Productivity
If the transparent material confining element is coated by the photopolymerizable material, then the material can be irradiated through the confining element, but the confining element must be mechanically stable while allowing optical transmission
Solution Approach 1:
The patent selects specific material parameters for the transparent confining element (thickness: 0.5-5 mm, refractive index: 1.3-1.6) that simultaneously provide mechanical stability and optical transparency. These parameter choices allow the element to withstand the coating process and maintain structural integrity while enabling effective radiation transmission for curing the photopolymerizable material.
Solution Approach 2:
The transparent material confining element is designed as a composite structure combining a transparent base material (acrylic, polycarbonate, or glass) with an antireflection coating layer. This composite structure provides both the mechanical stability needed for the confining element and the optical properties to minimize total internal reflection, improving image contrast without significantly increasing complexity.
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 significantly reduces the occurrence of shape formation errors by minimizing the portion of radiation reflected back into the material, improving the accuracy and precision of the solidified layers, and preventing uncontrolled radiation distribution.
Implementation Method 1
the occurrence of the above-mentioned errors is avoided or at least reduced by adapting the thickness of the material confining element and the coated surface to one another such that less than 40%, preferably less than 30%, particularly preferably less than 20%, in particular less than 10%, of the radiation reflected from the material into the material confining element is reflected back into the material
Implementation Method 2
Such a ceramic-filled material is a suspension of components with different refraction indices. This leads to the diffusion or redistribution of the light introduced for curing the material, and hence to an attenuation of contrast
Implementation Method 3
individual layers of a shaped body are cured by position-selective radiation, thus successively producing the desired object in its three-dimensional shape
Data Source
AI summary
In a method for solidifying a photopolymerizable, diffusely reflecting material by irradiation, wherein the material coats a transparent material confining element, such as a material support or a tank bottom, and the irradiation of a surface to be solidified is performed through the transparent material confining element into the material, a) the thickness of the material confining element and b) the coated surface and/or the construction field and/or the surface to be solidified of the material are adapted to one another such that the thickness of the material confining element is at least ¼, preferably at least ⅓, preferably at least ½, of the diameter of the coated surface, or the surface to be solidified, or the construction field, respectively.