More rapid and efficient manufacturing of three-dimensional, transparent micro components

Thanks to this technique, it is now possible for the first time to manufacture even assembled components made of transparent materials such as glass from a single block – with micrometer accuracy. In contrast to ablative techniques, in-volume selective laser etching (ISLE) is exceptional for its efficient use of material.

Fused silica tubes with a diameter of one millimeter and a wall thickness of nine micrometers, hole arrays with bore diameters of 50 micrometers, microfluidic components for medical diagnostics with channels that are less than 10 micrometers in diameter: the components used in precision mechanics, medical engineering, and metrology are getting smaller and smaller as their complexity increases.

Take the example of the clock- and watchmaking industry, where so-called jewel bearings have to be precisely manufactured and subsequently mounted. At present, experienced specialists manually produce and mount these micro components by means of grinding and polishing, which takes a lot of time. Moreover, ablative techniques always entail a loss of material –typically as high as 80% – which can seriously impact costs depending on the specific material.

Given the tiny scale of micro components, transparent, i.e. “colorless”, materials are not amenable to manual processing, as the craftsman cannot see them well enough. Consequently, manufacturers revert to using rubies, which in addition to their hardness also have the advantage of being a red color that is easily visible.

In-volume selective laser etching speeds up the manufacturing process and removes the need for assembly

In cooperation with the Chair for Laser Technology LLT at RWTH Aachen University, a new laser manufacturing technique was developed at Fraunhofer ILT. The technique shortens the manufacturing process for micro components made from transparent materials and reduces the amount of material and energy used. Now the experts have applied in-volume selective laser etching (ISLE) to the manufacture of composite and assembled parts. This means there is no longer any need to adjust and assemble the individual components in micromechanical systems. The exposure time for a gear wheel already mounted on a shaft and fitted inside a housing is only around 15 minutes using the ISLE technique.
The process works as follows: using ultrashort pulsed laser radiation, a transparent work piece is exposed in the volume with 3D resolution at precisely the areas where material is to be removed. The material is chemically and physically changed and therefore gets selectively etchable. In the subsequent wet-chemical etching process, the exposed material is removed, while the unexposed material is scarcely affected by the etching process. This process makes it possible to manufacture micro channels, shaped holes, structured parts, and complex, composite mechanical components and systems. The ISLE technique can also be used for sapphire and glass as well as ruby. It is reproducible and ensures that components are geometrically identical in series production, while also offering a high degree of geometric and design freedom. Particularly impressive are its ability to produce shapes with micrometer accuracy, as well as kerfs and bores with extremely large aspect ratios, thanks to the small focus volume. The ISLE technique enables a level of material and energy efficiency that is simply not possible to obtain mechanically using even the most advanced ablative processes.

Scaling the laser manufacturing technique for industrial application

The main challenge facing the researchers in Aachen now consists in developing the ISLE technique so that it can be used by the manufacturers of micro components. “We are constantly working on improving the scalability of our technique so that a transfer from the lab to industrial-scale production can take place sometime in the future,” explains Dr. Dagmar Schaefer, group manager at Fraunhofer ILT. “The ISLE technique is individually adapted to the customer’s requirements according to the specific application. The biggest challenge for us is to achieve both the required component specifications and a sufficiently rapid structuring process at the same time.”
The exposure speed is currently several hundred millimeters a second. The goal is to increase this to several meters a second. At present, exposing a mounted gear wheel with a diameter of three millimeters would take 15 minutes; the higher exposure speed would reduce this time by a factor of 10.
In the medium term, efforts will be aimed at exploiting the potential of the technique within individualized mass production. This entails improvements to the present state of development that include increasing laser power and repetition rates and the use of faster beam deflection systems . ISLE promises greater cost-effectiveness and flexibility in the production of micro components in small and large batches, as well as in the mass production of individualized components.

Further Contacts

Dr. Dagmar Schaefer
Head oft he Group In-Volume Structuring
Phone +49 241 8906-628
dagmar.schaefer@ilt.fraunhofer.de
Fraunhofer Institute for Laser Technology ILT
Steinbachstraße 15
52074 Aachen, Germany

Akad. Oberrat Dr. Ingomar Kelbassa
Acad. Director of the Chair for Laser Technology LLT at the RWTH Aachen University
Phone +49 241 8906-143
ingomar.kelbassa@ilt.fraunhofer.de
Fraunhofer Institute for Laser Technology ILT
Steinbachstraße 15
52074 Aachen, Germany