Vat Photopolymerization Viscosity Control via Torque Measurement
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Solution Overview
Problem
In vat photopolymerization 3D printing, determining the viscosity of resins is challenging, especially during the printing process, as it affects the quality of the printed articles, with existing methods not effectively addressing the need for real-time viscosity measurement and control.
Innovation Solution
A method and system that utilize a torque meter to measure the force required to raise and lower a build plate within the resin tank, correlating this torque with known viscosities using a table, allowing for pre-build and real-time viscosity determination, and adjusting viscosity by heating the resin using the light source or independent heaters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If low viscosity resin is used, then rapid replenishment in build area is achieved, but shrinkage and warping occur during post-curing
Solution Approach 1:
The patent changes the temperature parameter of the resin dynamically during the printing process. By heating the resin to elevated temperatures, the viscosity is reduced to enable rapid replenishment, while the system maintains control over the heating process to prevent excessive shrinkage and warping that would occur with uncontrolled low-viscosity resin.
Solution Approach 2:
The patent implements dynamic viscosity control by adjusting the resin temperature in real-time during the printing process. The system transitions from static viscosity conditions to dynamic viscosity adjustment, allowing the resin properties to be optimized at different stages of the printing process to balance replenishment speed and dimensional stability.
2Manufacturing precision
If high viscosity resin is used, then shrinkage and warping are reduced, but replenishment in build area becomes slow
Solution Approach 1:
The patent applies temperature parameter changes to resolve the contradiction between high viscosity (for dimensional stability) and slow replenishment. By controlled heating, the system achieves optimal viscosity levels that maintain dimensional stability while enabling adequate replenishment speed.
3Productivity
If heating is applied to reduce viscosity, then replenishment speed improves, but temperature control complexity increases
Solution Approach 1:
The patent makes the light source serve multiple functions: it performs both the primary function of curing the resin and the secondary function of heating the resin to control viscosity. This multi-functionality eliminates the need for separate heating systems, reducing overall device complexity while achieving temperature control.
Solution Approach 2:
The resin curing process itself generates heat that is utilized to maintain optimal viscosity. The system leverages the exothermic nature of the photopolymerization reaction to help heat the resin, reducing the need for external heating infrastructure and simplifying the temperature control system.
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
Enables accurate and dynamic viscosity measurement and control, reducing shrinkage and warping issues, and improving the quality of printed articles by ensuring optimal resin viscosity throughout the printing process.
Implementation Method 1
a measure of a torque required to raise the build plate is recorded by a torque meter
Implementation Method 2
adjusting viscosity by heating the resin using the light source or independent heaters
Implementation Method 3
selective curing of resins contained in a vat using (typically) ultraviolet (UV) light sources. The resin is cured layer by layer
Data Source
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Figure 2
AI summary
Methods and systems for forming 3D articles by vat photopolymerization processes in which resin viscosities are determined both prior to the commencement of the build process and, optionally, during the build process by measuring the torque required to raise and lower a build plate within the resin in the vat. The resin may be heated, and its viscosity thereby altered, by heating the resin in the vat using a light engine employed for fabricating the 3D articles.