Transparent Sheet Planarity Control in Stereolithography
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Solution Overview
Problem
Stereolithography 3D printers face challenges in achieving high resolution and dimensional accuracy due to the distortion of transparent sheets caused by the weight of photocurable liquid columns, which affects the planarity and small feature size production.
Innovation Solution
A 3D printing system with a tensioned transparent sheet supported by a tension ring and rollers, combined with a light engine and pressurized gas, to maintain planarity and positional accuracy by constraining the sheet's vertical location and applying fluid pressure equal to or less than the photocurable liquid column pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a thin layer of photocurable liquid is used to enable small feature sizes, then manufacturing precision is improved, but the weight of the liquid column distorts the transparent sheet, worsening planarity
Solution Approach 1:
A roller is positioned between the transparent sheet and the photocurable liquid to apply an upward force that counteracts the downward distortion caused by the liquid column weight. This counterweight mechanism restores and maintains the planarity of the transparent sheet, enabling thin layer processing for small feature sizes without sacrificing sheet flatness.
2Shape
If the transparent sheet is tensioned to maintain planarity, then manufacturing precision is improved, but the vertical positional accuracy of the sheet is compromised
Solution Approach 1:
The roller serves as an intermediary element that transmits and distributes forces between the transparent sheet and the support structure. By positioning the roller between the sheet and the liquid column, it mediates the mechanical interactions to maintain both planarity and vertical positional accuracy through balanced force distribution.
Solution Approach 2:
The patent replaces complex mechanical tensioning systems with a simpler roller-based support mechanism. This substitution maintains planarity through the roller's contact support while improving vertical positional accuracy by eliminating the need for aggressive tensioning forces that would compromise positioning.
3Shape
If pressurized gas is applied to the transparent sheet to maintain planarity, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
Pressurized gas is introduced into the build vessel to apply uniform upward pressure on the transparent sheet, counteracting the downward distortion from the photocurable liquid column. This pneumatic approach maintains sheet planarity with a relatively simple system that adds minimal complexity compared to mechanical tensioning or active control systems.
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
The system effectively improves the planarity and vertical positional accuracy of the transparent sheet, enabling the production of 3D articles with features sizes as small as 10 microns by reducing bulge-induced errors and maintaining precise layer formation.
Implementation Method 1
The roller exerts an upward force on the transparent sheet and the two opposing sides of the tension ring. The upward force of the roller against the tension ring-with the transparent sheet therebetween-constrains a vertical location and improves planarity of a supported portion of the transparent sheet adjacent to the roller.
Implementation Method 2
A source of pressurized gas is configured to apply fluid pressure to a lower surface of the transparent sheet. The fluid pressure applied by the pressurized gas is equal to or less than a fluid column pressure exerted by a column of photocurable liquid within the build vessel.
Implementation Method 3
The light engine is configured to selectively apply radiation to a projected area of the build plane through the supported portion of the transparent sheet.
Data Source
AI summary
A 3D printing system includes a build vessel, a carriage, and a light engine. The build vessel includes a vessel base having a downward extending tension ring that tensions a transparent sheet. The transparent sheet laterally bounds a build plane that is defined over orthogonal lateral axis X and Y. The carriage includes a roller that extends between two opposing sides of the tension ring. The roller exerts an upward force on the transparent sheet and the two opposing sides of the tension ring. The vertical constraint of the roller biased against the tension ring provides a location and improved planarity of a supported portion of the transparent sheet adjacent to the roller. The light engine light engine is configured to selectively apply radiation to a projected area of the build plane through the supported portion of the transparent sheet.