Guilherme Mallmann

Interferometric measurement of injection nozzles using ultra-small f iber-optical probes

The measurement of boreholes with diameters smaller than 500 ?m is a demanding task that cannot be performed using state-of-the-art production metrology. In this letter, a miniaturized fiber probe with a diameter of 80 \mu m is presented. A probe is used for low-coherence interferometry to conduct highly precise measurements of form deviations of small boreholes. Measurements conducted in nozzles are also presented. The results prove the potential of the fiber-optical sensor for quality inspection of high-precision parts, such as injection nozzles, for common-rail diesel engines.

Development of a FD-OCT for the inline process metrology in laser structuring systems

Laser structuring is a rapidly developing manufacturing technique with long-term technological impact on future economics and ecological challenges. Due to its high process flexibility, the laser structuring system permits the structuring of different work pieces (different forms and structure complexity) with the same machine configuration. A crucial fact is the process knowledge and its control. The state of the art in laser structuring has however a crucial deficit. Present structuring systems contain no metrology setup to detect the shape geometry and contour accuracy before, during or after the structuring process. Therefore no result feedback to the machine can be accomplished and consequently a process control based on the real machined surface is not possible. In order to close this technology gap and assure an automated and robust manufacture process, a metrological system needs to be integrated to the process. In this work the concept and the development of an adjustable optical coherence tomography measuring system based on the analysis of the frequency domain (FD-OCT) with sub-micrometer accuracy for the in process measurement in a laser structuring machine is described. Goal of the research presented here is the development of the measuring system, with special focus on the spectrometer development (optical and software) and machine integration (optical and mechanical), as well as the development of an innovative wideband source based on amplified spontaneous emission (ASE) in ytterbium-doped double-clad fiber.

Process-structure-property relationship of laser-joined thermoplastic metal hybrids

During the last years, several studies have been conducted to improve the laser-based heat conduction joining of thermoplastic metal hybrids. Most scientists tried to improve the joint quality by a prior surface enlargement of the metal in order to achieve a strong mechanical interlocking. Only a few authors investigated hybrids which consist of merely cleaned and not additionally enlarged metallic specimens. For merely cleaned specimens, Katayama et al. postulated the bubble theory which suggests that small bubbles near the metallic interface are very important for strong joints. The bubble formation leads to a high pressure between thermoplastic and metal so that the thermoplastic melt wets the metallic surface and an anchor effect occurs. Investigations by the author confirm the anchor effect theory, but the bubble theory itself cannot be verified since strong joints can be realized without the formation of bubbles. On the contrary, it seems rather advisable to avoid bubbles because they indicate a the...

Wideband and high-power light sources for in-line interferometric diagnostics of laser structuring systems

Laser structuring is rapidly developing manufacturing technique for broad spectrum of industrial branches, e.g. aerospace, power engineering, tool- and mould making, and automotive. It enables to prepare work pieces and products with very fine micro structures achieving a far better degree of details than conventional structuring techniques like etching or eroding. However, the state of art in laser structuring shows a crucial deficit. Used systems contain no metrology setup to detect the shape geometry (depth and length) and contour accuracy during the process. Therefore, an innovative in-line metrology technique based on low coherence interferometry for laser structuring systems has been investigated and described in the paper. In this contribution we present our results in the research of wideband and highpower light sources for the proposed low-coherence interferometric measurement system. The system can be incorporated into a structuring workplace equipped with a Q-switched ytterbium-doped fiber laser at 1064 nm for material processing. In the paper we focus on two wideband sources for such a measurement system. The first source is based on a superluminescent diode and the second one is based on an amplified spontaneous emission in a double-clad ytterbium-doped fiber. An example of results measured with the proposed in-line metrology system is presented.

Fiber-Optical Interferometer for Distance Measurements: Investigation of LinearityLinearitätsuntersuchungen eines faseroptischen Distanzmesssystems

Abstract Thoroughly investigated optical principles like interferometry can be very well combined with the advantages of light guiding fibers. Such a combination enables the realization of unique measurement systems with exceptional features. We present the extended investigation and compensation of the linear behaviour of our fiber-optical distance sensor.