Claus Dold

Cable‐crawler – robot for the inspection of high‐voltage power lines that can passively roll over mast tops

Purpose – The purpose of this paper is to describe the design and prototype implementation of the “Cable Crawler”, a mobile teleoperated robot for the inspection of high‐voltage power lines which rides on the topmost ground cable. By not being limited to just moving from mast to mast, it implements an innovative mechanism that allows for crossing a set of mast tops as well as smaller obstacles autonomously.Design/methodology/approach – After a brief overview of the state‐of‐the‐art for this application, the basic concept of the robot is presented – which basically consists of a chassis and six motorized rubber‐coated rollers, two in a horizontal position to take the weight and four vertical ones. The four vertical rollers are pressed onto the wire by springs, which guarantees slip‐less propulsion in difficult situations. The detailed design of the most challenging components is presented, as well as the successful tests with the prototype.Findings – The feasibility of the concept is proven with a prototyp...

Picosecond laser fabrication of micro cutting tool geometries on polycrystalline diamond composites using a high-numerical aperture micro scanning system

The generation of microsized components found in LEDs, watches, molds as well as other types of micromechanics and microelectronics require a corresponding micro cutting tool in order to be manufactured, typically by milling or turning. Micro cutting tools are made of cemented tungsten carbide and are conventionally fabricated either by electrical discharge machining (EDM) or by grinding. An alternative method is proposed through a laser-based solution operating in the picosecond pulse duration whereby the beam is deflected using a modified galvanometer-driven micro scanning system exhibiting a high numerical aperture. A micro cutting tool material which cannot be easily processed using conventional methods is investigated, which is a fine grain polycrystalline diamond composite (PCD). The generation of various micro cutting tool relevant geometries, such as chip breakers and cutting edges, are demonstrated. The generated geometries are subsequently evaluated using scanning electron microscopy (SEM) and quality is measured in terms of surface roughness and cutting edge sharpness. Additionally, two processing strategies in which the laser beam processes tangentially and orthogonally are compared in terms of quality.

Influence of Picosecond Laser Touch Dressing of Electroplated Diamond Wheels on the Dressing of SiC Vitrified Bond Wheel

Touch dressing of electroplated diamond wheels is a challenging technique used for precision form grinding. This paper presents an investigation to explore the capabilities of modern laser technology for touch dressing. A pulsed picosecond laser (ps-laser) beam (Yb:YAG) is used to cut diamond grains within a definite grain protrusion without noticeable thermal damage neither on the nickel bond material nor the diamond itself. A systematic study on laser irradiation parameters on cutting quality is presented. Series of experiments by dressing of SiC wheels using an ultrashort pulsed laser source as well as conventional touch dressed diamond wheel are carried out and both methods are compared. Significant advantages of the novel laser method are presented.

Performance of Lasered PCD- and CVD-Diamond Cutting Inserts for Machining Carbon Fiber Reinforced Plastics (CFRP)

Carbon fiber reinforced plastics (CFRP) combine superior mechanical properties with a low weight. Consequently, this material is highly interesting for the aircraft as well as the automotive industry, leading to a massively increased application over the last years. However machining CFRP still faces different difficulties: The material is highly abrasive, most tool substrates and coatings face massive abrasive wear. Machining CFRP often results in many material defects like delamination, fiber pull-out, high surface roughness and burnt matrix material. Several technologies have been developed to combine ultra-hard tool surfaces and most adaptable cutting edge geometries. One of the most interesting approaches is laser machining of diamond cutting edges. The technology combines the wear resistance of thick layer diamonds with a geometrical flexibility so far known only for carbide tools. In the presented study, the wear resistance of different Polycrystalline Diamond (PCD) and Chemical Vapor Deposition (CVD)-Diamond grades machined with two different laser systems has been tested for machining CFRP. In comparison state-of-the-art grinded PCD cutting inserts are being tested. The comparison of machining characteristics is done by machining CFRP in a continuous turning process with a single fiber orientation. Machining forces are measured to evaluate tool wear. The resulting work piece quality is analyzed by measuring the surface roughness. The machined CFRP is a M21 resin system with an IMA-12K fiber from Hexcel

Relevance of laser touch-dressed diamond tools for the dressing performance of vitrified-bonded silicon carbide wheels

Touch dressing of electroplated diamond grinding and dressing tools enable the generation of well-defined profile modifications and grain protrusions. This paper contributes to the utilisation of ultra-short pulse laser in touch dressing technology and outlines the cutting performance of laser touch-dressed diamond tools in dressing operations of vitrified-bonded silicon carbide. Surfaces of abrasive diamond tools are cut using a picoseconds laser beam to generate a well-defined grain protrusion without thermal damage of either the nickel matrix or the diamond structure. Irradiation parameters were systematically varied in order to determine a process window. Dressing operations were carried out using conventional and laser touch-dressed dressing tools. Lower dressing forces and higher dressing force ratios outline the advantage of the laser touch-dressed diamond tools in terms of material removal efficiency. Additionally, no remarkable differences in wear progression of conventional and laser touch-dressed diamond tools were observed. Furthermore, the laser touch-dressing model is presented using stochastically-distributed grain morphologies.

Surface structuring of zirconium-based bulk metallic glasses using ultrashort laser pulses

A technique for structuring the surface of a bulk metallic glass (BMG) via scanning with a beam of laser pulses in the pico- and femtosecond time regime is presented. Specimens were characterized by various techniques to analyze the effects of ultrashort laser pulses on the amorphous matrix. Broadly varying surface structures, with roughness parameters in the range of Ra = 0:066 to 0:329 μm, measured using white light interferometry (WIM) and optical 3D microscopy, were produced. These techniques could be useful for fabricating biomedical implants from BMGs. As proof of principle, a patterned grid, designed for evaluating bone cell response to different surface structures, are produced.

The physics in applications of ultrafast lasers

High precision and high throughput material processing using ultrashort pulsed laser radiation of high average power requires a detailed understanding of the laser matter interaction on ultrafast time scales. In this paper, we will focus on energy transport mechanisms based on the two-temperature-model and the resulting ablation regimes for single pulses. Heat accumulation at high pulse repetition rates and spatial pulse overlap will be discussed. Additional, a novel nonthermal ablation mechanism for graphite and corresponding materials will be presented.