Laser Head Calibration for Beam Focus and Position Accuracy
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Solution Overview
Problem
Conventional additive manufacturing systems face challenges in maintaining constant focus and optimal beam positioning due to geometric deformations caused by the inclination of the optical beam and the geometry of the optical path, leading to suboptimal energy transmission and pattern deformation on the powder bed.
Innovation Solution
An automatic calibration method using a calibration plate with reference marks and a firing medium, where the radiation source generates a calibration pattern with varying focus commands to determine corrected commands based on the distribution of impact points, allowing for precise adjustment of the focus and position to achieve optimal beam alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a three-axis head system with galvanometers is used to control beam positioning and focus, then positioning precision and focus control are improved, but geometric deformations (inclination effects and pillow-shaped distortion) occur on the powder bed
Solution Approach 1:
The patent applies preliminary action by performing calibration before actual manufacturing. A calibration plate with known reference marks is used to pre-determine correction values for geometric deformations. The system measures the actual positions of impact points on the calibration plate and computes correction tables that compensate for pillow-shaped distortion and inclination effects before production begins.
Solution Approach 2:
The patent implements feedback by using a camera-based measurement system to detect the actual positions of impact points on the calibration plate. The measured positions are compared with theoretical target positions, and the differences are used to compute correction values. This feedback loop enables the system to automatically adjust and compensate for geometric deformations.
2Area of stationary object
If the beam is inclined to access different areas of the powder bed, then coverage area is improved, but focus varies across the working plane due to optical path length variations
Solution Approach 1:
The patent applies parameter changes by measuring the actual focus positions at different locations on the calibration plate and using this information to compute Z-axis correction values. The system determines the distribution of diameters of impact points to infer focus quality and adjusts the Z-position commands accordingly, compensating for focus variations caused by beam inclination across the working plane.
3Device complexity
If manual calibration methods are used to determine correction tables, then device complexity is reduced, but calibration precision and automation are worsened
Solution Approach 1:
The patent implements self-service by enabling the calibration system to automatically perform measurements, compute corrections, and generate correction tables without manual intervention. The camera-based measurement system automatically detects impact point positions, and the system autonomously computes the correction values and stores them in lookup tables for future use.
4Manufacturing precision
If correction tables are determined using calibration plates with reference marks and camera measurement, then manufacturing precision is improved, but loss of time occurs during calibration
Solution Approach 1:
The patent applies preliminary action by performing calibration once before production runs. The correction tables determined during calibration are stored and reused for subsequent manufacturing operations, so the time investment is made only once while achieving continuous precision benefits throughout production.
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 method enables improved calibration of the radiation source, ensuring consistent focus and position accuracy across the powder bed, enhancing the precision and efficiency of the additive manufacturing process by correcting for geometric deformations and optimizing energy transmission.
Implementation Method 1
Selective additive manufacturing consists in producing three-dimensional objects by consolidating selected zones of successive strata of pulverulent material (metal powder, ceramic powder). The consolidation is achieved, layer by layer, by partial or complete selective fusion carried out with a focused radiation source, such as an optical source (high-power laser for example)
Implementation Method 2
The more the laser beam is correctly focused on the powder bed, the higher and better controlled the energy transmitted to the fusion point
Implementation Method 3
Two galvanometers 1, 2 are used to guide two mirrors 3, 4 rotationally and to allow the path of the beam output from the head to be controlled, in order to control the positioning of the point of impact of the beam on the powder bed (work plane P)
Implementation Method 4
a DFM ('Dynamic Focusing Module')—comprising a galvanometer, a translating module and a lens—allows, by virtue of the translation of said lens, the focal length of the beam to be perfectly adjusted to the powder bed (command in Z)
Data Source
AI summary
An assembly for calibrating a head system of a power radiation source of an additive manufacturing apparatus comprises: a calibration plate comprising a plurality of reference marks, and a firing medium made of at least one material that is sensitive to the radiation of the source, this medium leaving visible the reference marks of the calibration plate when it is in place on the latter, characterized in that the firing medium comprises a plurality of windows that are distributed so as to be superposed with the various reference marks of the calibration plate and to leave said marks visible when the firing medium is in place on the calibration plate. There is also a method for calibrating such a system.