High accuracy, quality and throughput are key factors in laser micro machining. To obtain these goals the ablation process, the machining strategy and the scanning device have to be optimized. The precision is influenced by the accuracy of the galvo scanner and can further be enhanced by synchronizing the movement of the mirrors with the laser pulse train. To maintain a high machining quality i.e. minimum surface roughness, the pulse-to-pulse distance has also to be optimized. Highest ablation efficiency is obtained by choosing the proper laser peak fluence together with highest specific removal rate. The throughput can now be enhanced by simultaneously increasing the average power, the repetition rate as well as the scanning speed to preserve the fluence and the pulse-to-pulse distance. Therefore a high scanning speed is of essential importance. To guarantee the required excellent accuracy even at high scanning speeds a new interferometry based encoder technology was used, that provides a high quality signal for closed-loop control of the galvo scanner position. Low inertia encoder design enables a very dynamic scanner system, which can be driven to very high line speeds by a specially adapted control solution. We will present results with marking speeds up to 25 m/s using a f = 100 mm objective obtained with a new scanning system and scanner tuning maintaining a precision of about 5 μm. Further it will be shown that, especially for short line lengths, the machining time can be minimized by choosing the proper speed which has not to be the maximum one.
In earlier work the capabilities of synchronizing a galvo scanner or a polygon line scanner with a picosecond laser system in MOPA arrangement were presented. However these systems only enabled precise positioning of laser pulses on the target relatively to each other. Since then a novel approach to increase the absolute precision in positioning has been developed. This improvement enables new and more efficient process strategies such as bidirectional processing or high precision structuring of large areas in combination with additional mechanical axes. These improvements represent a major step towards large scale industrial applications in laser based micromachining.
To be competitive in laser micro machining, high throughput is an important aspect. One possibility to increase
productivity is scaling up the ablation process i.e. linearly increasing the laser repetition rate together with the average
power and the scan speed. In the MHz-regime high scan speeds are required which cannot be provided by commercially
available galvo scanners. In this work we will report on the results by using a polygon line scanner having a maximum
scan speed of 100 m/s and a 50 W ps-laser system, synchronized via the SuperSync™ technology. We will show the
results concerning the removal rate and the surface quality for working at the optimum point i.e. most efficient point at
repetition rates up to 8.2 MHz.
KEYWORDS: Pulsed laser operation, Scanners, Laser systems engineering, Laser ablation, Laser scanners, 3D scanning, Scanning electron microscopy, Copper, Applied sciences, Control systems
For surface and 3D structuring ultra-short pulsed laser systems are used in combination with mechanical axes, whereas the mechanical axes can include electrical motor as well as beam deflecting systems like a galvo scanner. The motion of the axes is synchronized with the clock of the laser pulses, which is usually in the range of 100 kHz and above, by a modification of the electronic axes control. This work shows the scalability of the ablation process up to MHz-regime in relation to surface quality and ablation efficiency. Furthermore the transfer of the machining strategy from a synchronized galvo scanner to a rotating cylinder setup is shown.
For surface and 3D structuring the ultra short pulsed laser systems are mostly used in combination with galvo scanners.
This work reports on the synchronization of the scanner mirror motion with the clock of the laser pulses, which is usually
in the range of 100 kHz and higher, by a modification of the electronic scanner control. This synchronization facilitates
the placement of the small ablation craters from single pulses with the precision of about 1 μm relative to each other. The
precise control of the crater positions offers the possibility to test and optimize new structuring strategies. Results of this
optimization process with respect to minimum surface roughness, steepness of wall, accuracy to shape and efficiency
will be presented.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.