Gear wheel measuring three
millimeters in diameter
mounted on a shaft, made
from a single block of fused
silica using the ISLE
technique;© Fraunhofer ILT
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 percent – which can seriously impact costs depending on the specific material. Given the tiny scale of micro components, transparent, for example “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.
The new laser manufacturing 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.
COMPAMED.de; Source: Fraunhofer Institute for Laser Technology ILT