Metal Precursor Slurry for Stereolithography Depth of Cure
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Solution Overview
Problem
The depth of cure in stereolithography processes for manufacturing three-dimensional metal objects is limited due to the high refractive index difference between metal particles and the photo-curable resin, leading to insufficient mechanical strength and potential defects in the final product.
Innovation Solution
A slurry comprising a polymerizable resin, photoinitiators, and a mixture of metal particles and metal precursors is used, where the metal precursors have a refractive index closer to the resin than the metal, increasing the depth of cure and mechanical strength of the resulting three-dimensional metal objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If metal particles are used in the slurry for stereolithography, then the final metal object is obtained, but the refractive index difference between metal particles and photo-curable resin limits the depth of cure
Solution Approach 1:
The patent introduces metal precursor particles as an intermediary material between the photo-curable resin and the final metal object. These precursor particles have a refractive index closer to the resin, reducing light scattering and enabling deeper radiation penetration during photopolymerization. After curing, the precursor particles are converted to metal through thermal treatment, thus achieving the desired metal object while overcoming the refractive index mismatch problem.
Solution Approach 2:
The patent changes the optical parameters of the slurry composition by replacing metal particles with metal precursor particles that have different refractive index properties. This parameter change (from high refractive index metal to lower refractive index precursor) reduces the refractive index difference with the photo-curable resin, thereby improving radiation penetration depth and cure quality.
2Quantity of substance
If high metal particle loading is used in the slurry, then the metal object density is improved, but the radiation penetration depth is reduced
Solution Approach 1:
Metal precursor particles serve as an intermediary that allows higher solid loading in the slurry without proportionally increasing light scattering. The precursors have optical properties closer to the resin, enabling the formulation of slurries with 50-70 vol% solid content while maintaining adequate radiation penetration depth for effective photopolymerization.
Solution Approach 2:
The patent changes the optical absorption and scattering parameters of the slurry by using metal precursors instead of metal particles. This allows increasing the solid particle concentration (improving metal content in final object) while the modified optical parameters maintain sufficient radiation penetration depth for complete layer curing.
3Productivity
If the layer thickness is increased to improve productivity, then the manufacturing speed is improved, but the interface curing between layers becomes insufficient
Solution Approach 1:
The metal precursor particles act as an optical intermediary that enables deeper and more uniform radiation penetration through thicker layers. This ensures adequate interlayer interface curing even when layer thickness is increased, maintaining bond strength while improving manufacturing productivity by reducing the number of layers required.
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 allows for the production of three-dimensional metal objects with improved mechanical strength and reduced defects, achieving a stress-free and homogeneous microstructure through increased radiation penetration and controlled polymerization.
Implementation Method 1
scanning voxels of said first layer of radiation-curable slurry with radiation in accordance with the CAD model to cause polymerization of the polymerizable resin in the radiation-curable slurry to an organic binder
Implementation Method 2
converting any remaining metal precursor in the brown body of step (g) to the corresponding metal
Data Source
AI summary
A radiation-curable slurry for additive manufacturing of 3D metal objects is provided, comprising: (a) 2-45 wt % of a polymerizable resin; (b) 0.001-10 wt % of one or more polymerization photoinitiators; and (c) 55-98 wt % of a mixture of metal-containing compounds, wherein the mixture of metal-containing compounds comprises, based on the weight of said mixture, 5-95 wt % of metal particles and 5-95 wt % of one or more metal precursors. An additive manufacturing method for producing a three-dimensional metal object using the slurry is provided, as well as three-dimensional metal objects obtainable by the method.