MOEMS Vector Scanning Optical Unit for Stereolithography
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Solution Overview
Problem
Stereolithography machines using galvanometric mirrors are costly, bulky, and unsuitable for small series production due to high maintenance needs and inertia limitations, and single-axis MOEMS mirrors are inadequate for precise vector scanning, leading to inefficiencies in three-dimensional object fabrication.
Innovation Solution
A stereolithography machine employing a vector scanning optical unit with two micro-opto-electro-mechanical systems (MOEMS) mirrors, each rotating around a single axis, arranged orthogonally to each other, to achieve precise control and efficient scanning by moving the laser beam at velocities between 0.5 m/s and 3 m/s, allowing for quasi-static motion and optimized laser spot size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If galvanometric mirrors are used in the optical unit, then the light beam can be moved rapidly and the system is more reliable, but the cost is relatively high and the overall dimensions are considerable
Solution Approach 1:
The patent replaces galvanometric mirrors with a resonant scanner, substituting a mechanical system with higher inertia for one with lower inertia and resonant operation. This reduces the overall dimensions of the optical unit while maintaining rapid beam movement capability through resonant frequency operation.
Solution Approach 2:
The resonant scanner operates at its resonant frequency, utilizing periodic action to achieve rapid beam movement. The scanner is driven at resonance, allowing fast oscillations that move the light beam rapidly across the reference surface without requiring large mechanical dimensions.
2Measurement precision
If galvanometric mirrors are used in the optical unit, then the beam can be directed precisely, but the inertia is not negligible and affects the speed of deviation of the light beam
Solution Approach 1:
The resonant scanner has lower inertia compared to galvanometric mirrors, enabling faster acceleration and deceleration of the light beam. This substitution maintains positioning precision through controlled resonant oscillations while significantly improving beam deviation speed.
Solution Approach 2:
By operating the scanner at its resonant frequency, the system achieves maximum speed of beam deviation through periodic oscillations. The resonant operation allows rapid back-and-forth movement that increases beam deviation speed while maintaining precision through controlled motion patterns.
3Device complexity
If a single MOEMS mirror is used for scanning, then the device is simpler and cheaper, but the scanning precision and control are inadequate for vector scanning
Solution Approach 1:
The patent uses two separate MOEMS mirrors instead of one, dividing the scanning function into two independent components. Each mirror handles one axis of scanning, enabling precise vector scanning through coordinated operation of both mirrors while keeping each individual mirror simple and inexpensive.
Solution Approach 2:
The system extends from one-dimensional scanning with a single mirror to two-dimensional vector scanning using two mirrors arranged orthogonally. This adds a dimensional aspect to the scanning capability, allowing independent control along two axes for precise vector path following.
4Measurement precision
If two MOEMS mirrors are used for vector scanning, then precise control is achieved, but the production time increases due to higher inertia
Solution Approach 1:
Both MOEMS mirrors operate at their resonant frequencies, utilizing periodic action to achieve rapid oscillations. This resonant operation minimizes the time required for beam positioning and scanning, reducing production time while maintaining precise vector scanning control through coordinated resonant motion.
Solution Approach 2:
The system changes the operational parameters by operating the MOEMS mirrors at resonant frequencies rather than arbitrary speeds. This parameter optimization allows faster scanning motion that reduces production time while maintaining the precision required for vector scanning through controlled resonant oscillations.
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 configuration enables precise and efficient vector scanning, reducing production time and costs by using smaller, more controllable mirrors, improving surface characteristics, and maintaining a balance between scanning speed and single-pass solidification, making the machine suitable for the low-price market.
Implementation Method 1
a vector scanning optical unit configured to perform a vector scanning of a reference surface arranged inside said container according to a desired vector data image by means of said predefined radiation
Implementation Method 2
a source of predefined radiation suited to solidify the fluid substance
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a Stereolithography machine (1) comprising: • a container (2) for a fluid substance (15) suited to be solidified through exposure to predefined radiation (3a); • a laser source (3) apt to emit a beam of said predefined radiation (3a); • a vector scanning optical unit (4) configured to perform a vector scanning of a reference surface (5) arranged inside said container (2) according to a desired vector data image by means of said predefined radiation; • a memory to store said vector data image representative of an image to be scanned on said reference surface; • a logic control unit (6) configured for controlling said vector scanning optical unit (4) and/or said laser source (3) in such a way as to expose a predefined portion of said reference surface (5) to said radiation (3a) according to said vector data image; wherein said vector scanning optical unit (4) comprises a first and a second micro- opto-electromechanical systems (MOEMS) (7, 8) arranged in series one after the other with respect to a travelling path of said predefined radiation, each MOEMS system comprising: • a mirror (9) having a diameter comprised between about 2 mm and about 8 mm associated with a supporting structure (10) through articulation means (11) configured so as to define for said mirror (9) a rotation axis (X1, X2); • an actuator (12) suited to move said mirror (9) around said rotation axis (X1, X2) in a quasi-static manner at an angular speed so that a corresponding marking speed of said laser beam on said reference surface (5) is comprised between about 0.5 m/s and about 3 m/s when said laser source (3) is emitting said predetermined radiation (3a) during said vector scanning; and wherein • the rotation axis (X1) of the mirror (9) of the first MOEMS system (7) is incident to the rotation axis (X2) of the mirror (9) of the second MOEMS system (8).