PBLM Laser Scanner Calibration Using a Movable Virtual Reference
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Solution Overview
Problem
Current calibration methods for powder-bed-based laser melting (PBLM) systems are inadequate for real-time calibration during the build process, as they either reduce the build area or are limited to the working plane, failing to account for thermal and mechanical drifts, and cannot calibrate multiple laser scanner units simultaneously without compromising component quality.
Innovation Solution
A calibration method using a virtual reference mark projected onto a vertically movable reference surface, allowing for independent calibration of beam source deflection units regardless of the reference surface's position, enabling precise orientation and adjustment of laser beams to minimize overlap and ensure micrometre-precision in three-dimensional component production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a physical calibration unit is introduced into the process chamber for calibration, then calibration can be performed, but the build area is reduced and component quality may be compromised
Solution Approach 1:
The patent uses a virtual reference mark (optical copy) projected onto the reference surface instead of a physical calibration unit. This virtual mark is created by projecting calibration patterns through the laser scanner system, allowing calibration measurements to be performed without occupying physical space in the build area, thus resolving the contradiction between calibration precision and build area availability.
Solution Approach 2:
The patent introduces a reference surface (such as the build plate or a dedicated calibration surface) as an intermediary medium. The virtual reference mark is projected onto this surface, and the laser beam position is calibrated relative to it. This intermediary allows calibration to occur without requiring physical calibration objects within the build volume, maintaining both calibration accuracy and build area.
2Device complexity
If calibration is performed using methods limited to the working plane, then calibration setup is simple, but thermal and mechanical drifts cannot be compensated
Solution Approach 1:
The patent extends calibration from the two-dimensional working plane to three-dimensional space by projecting virtual reference marks at different positions and orientations on the reference surface. The laser scanner calibrates beam positions, angles, and focal points in 3D space, enabling compensation for thermal and mechanical drifts that affect spatial geometry, while maintaining relatively simple setup procedures.
3Productivity
If multiple laser scanner units are calibrated simultaneously using external calibration structures, then calibration efficiency improves, but the coverage area must extend outside the build area reducing available build space
Solution Approach 1:
The patent creates a universal calibration reference system where virtual reference marks are projected onto the reference surface within the build area, serving as a common calibration target for multiple laser scanner units. This multi-functional reference system allows simultaneous calibration of multiple scanners without requiring external calibration structures, thus improving calibration efficiency while preserving build area.
4Measurement precision
If relative calibration of laser scanner units is performed using camera evaluation, then calibration between units is possible, but drifts through thermal influences or mechanical setting cannot be allowed for and calibration is limited to the working plane
Solution Approach 1:
The patent replaces the mechanical/optical camera evaluation system with a computational approach. Virtual reference marks are projected and their positions are detected by analyzing the laser scanner's own beam position data and the known projection geometry. This substitution eliminates the need for separate camera systems, allows 3D calibration beyond the working plane, and enables drift compensation through repeated measurements and coordinate transformation calculations.
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 allows for precise calibration of multiple laser scanner units during the build process, compensating for thermal and mechanical drifts, and ensuring high-quality components by maintaining a larger build area and enabling focus and position calibration independently of the working plane, thus improving the accuracy and reliability of PBLM systems.
Implementation Method 1
beam source deflection unit which, in particular in the case of an PBLM system, is designed as a laser scanner unit
Implementation Method 2
by means of a detector a target-actual deviation between the virtual reference mark and a beam of the beam source deflection unit is determined
Data Source
AI summary
A calibration method for a system for powder bed-based generating of three-dimensional components by means of electromagnetic radiation, in particular such as a PBLS system, having a radiation source deflection unit and a raisable and lowerable carrier plate, above which a component is built, where, in order to calibrate the radiation source deflection unit, at least one virtual reference mark is used and, by means of a detector, a target-actual deviation between the virtual reference mark and a beam of the radiation source deflection unit is determined. An improved calibration method is achieved in that the at least one virtual reference mark is projected on a reference surface, which can travel vertically by means of the raisable and lowerable carrier plate, and independently of the vertical position thereof.