Innovative 7-axis synchronization strategy for enhanced laser texturing of freeform surface

A novel manufacturing strategy of 7-axis synchronization on-the-fly laser surface texturing, proposed by Harbin Institute of Technology researchers, enables simultaneously achieving high efficiency, high accuracy and large-scale without stitching error in patterning of freeform surface. 

The work, reported in the International Journal of Extreme Manufacturing, has great prospects in enhancing the quality and performance of laser micromachining of freeform surface.

While laser surface texturing is a promising manufacturing technique for surface functionalization, there is an emerging demand for the precise and efficient texturing of complex curved surface.

"There are some challenges: how to make laser beam always coincident with ablated surface normal, how to achieve large size texturing without stitching error, and how to accelerate the texturing process without compromising accuracy." said Junjie Zhang, corresponding author on the paper and Professor in HIT's School of Mechatronics Engineering. "Apparently, there is urgently needing an innovative strategy for those challenges."

Existing techniques can only partially solve the challenges. For instance, the 5-axis linkage mechanical platform has been widely used for curved surface texturing, but there are inevitably stitching errors due to the “step-and-scan” segmentation principle. Alternatively, combining 2-axis motion platform with galvanometer can achieve ‘Infinite field of view’ on-the-fly large-scale laser texturing of planar surface without stitching errors, but the corresponding kinematics for curve surface texturing is far complicated because of nonlinear trajectory assignment, laser pose deviation and motion solution.

To overcome these limitations, The researchers developed a 7-axis synchronization algorithm of laser texturing for freeform surface, which decomposes the original spatial texture trajectory into high-frequency trajectory for galvanometer and spatial low-frequency trajectory for 5-axis linkage motion platform, without violating the laser-matter incidence deviation permitted by the machining process. Based on the kinematic model, the displacement of the five-axis mechanical platform and the synchronous galvanometer displacement are calculated respectively. 

To realize this 7-axis synchronized laser texturing approach, corresponding setup of mechanical stages integrated with optical path, configuration of numerical control unit and processing software are developed. A Case study shows the absence of stitching errors in the large size freeform surface with ultrasmall deviation of 0.8% of fabricated texture spacing from designed value, and a 559% improvement of processing efficiency, due to the 60% significantly reduced following errors of mechanical stages for accommodating microscale motion. 

"The great improvement of the laser surface texturing efficiency and accuracy makes this method having obvious industrial application prospect." said the author Wenqi Ma, “This technology may contribute to popularizing the application of laser surface texturing of functional curved surface.”

The researchers are continuing this work with the hope of providing a general method for translating the proven planar functional surface texture onto curved surfaces. 

About IJEM:

International Journal of Extreme Manufacturing (IF: 16.1, consecutive 1st in the Engineering, Manufacturing category) is a multidisciplinary and double-anonymous peer-reviewed journal uniquely publishing original articles and reviews of the highest quality and impact in the areas related to extreme manufacturing, ranging from fundamentals to process, measurement, and systems, as well as materials, structures, and devices with extreme functionalities.

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