Technical Paper
Comparative analysis of tangentially laser-processed fluted polycrystalline diamond drilling tools

https://doi.org/10.1016/j.jmapro.2016.06.023Get rights and content

Highlights

Abstract

Ultrashort-pulsed laser ablation is increasingly applied in various fields of science and technology. For the purpose of processing ultra-hard materials, such as diamond and cubic boron nitride (CBN) composites, lasers have the decisive advantage of wear-free material removal. The availability of high-powered ultrashort-pulsed laser sources enables the efficient applications of tangential processing strategies to generate complex 3D geometries. Compared to the conventionally applied 2.5D volume ablation strategy, the resulting workpiece form tolerance, repeatability, and surface quality is increased significantly and does not depend on the quality of the initial surface. This makes tangential processing an ideal choice for high-precision finishing processes.

This paper presents a set of processes for the tangential ablation of characteristic twist drill features, such as helical grooves, flank faces and notches at the chisel edge. The processes have been implemented using a pulse duration of 12 ps, infrared laser source with an average power of 35 W average power for generating PCD tools. A comparative drilling study in zirconium dioxide (ZrO2) with diamond-coated tungsten carbide tools and solid PCD tools processed by electrical discharge machining is conducted to assess the performance of the laser-processed PCD tools.

Introduction

Ongoing industrial developments towards the applications of hard materials, such as tungsten carbide (WC) and ceramics, automated production, and tighter tolerance create a demand for ultra-hard tool materials, such as diamond and cubic boron nitride (CBN), for increased dimensional stability and tool lifetime. The properties of these materials force conventional tool production technologies, especially grinding, to their limits. Due to its wear-free nature, pulsed laser ablation offers the advantage of highly flexible and precise machining, independent of the mechanical properties of the processed material. This enables the development of new processes for generating ultra-hard tools in a wide range of industrial applications.

This paper demonstrates the applicability of high-powered ultrashort-pulsed laser ablation for the manufacturing of fluted cutting tools. This is achieved by applications of a novel tangential laser process that combines the flexibility of 5-axes CNC machines with the dynamics of galvanometer scanning systems, allowing the efficient laser ablation of complex geometries. The process is applied to produce composite polycrystalline diamond (PCD) drilling tools with a number of characteristic features, such as the flank face, notches at the chisel edge and the secondary cutting edge. The tools are compared to commercially available chemical vapour deposited diamond (CVD-D) coated tools and electrical discharge machined (EDM) PCD tools with respect to surface quality, cutting edge radii, cutting performance and tool life time while drilling zirconium dioxide.

The outstanding properties of zirconium dioxide, such as hardness, wear resistance, chemical and thermal stability, light-weight and biocompatibility, cause their increasing application as technical elements in various fields including biomedicine, metal forming, turbine construction, bearing technology, jet nozzles, etc. The introduction of laser-processed solid PCD tools with defined cutting edges, as presented in this paper, may significantly impact the use of these materials by enabling efficient and precise processing of small geometries, such as bores which cannot be ground due to limited accessibility.

Section snippets

Literature review

Fluted cutting tools are conventionally manufactured by grinding. The helical groove constitutes the most challenging feature both for the design and for the manufacturing of this tool geometry and is topic of extensive research efforts. Various models are introduced to support this process. Li et al. [1] applied a geometrical approach to determine the shape of the helical groove based on the machine kinematics and the grinding wheel profile. A method to optimise the helical groove geometry

Tangential laser processing

Compared to 2.5D volume ablation, the tangential laser process has the decisive advantage that the material removal takes place orthogonally to the beam direction with a comparatively well-defined and stable dimensional limit. Consequently, the resulting geometry is defined mainly by the relative motion between laser beam and workpiece. Timmer [8] described this characteristic as the ability for true profiling. After the target geometry is reached, the contour generated is independent of

Measuring and validation testing

The cutting edge radii and the surface quality of the PCD tools are measured using a variable-focus 3D-microscope. As shown in Fig. 4, the PCD tools are tested by drilling zirconium dioxide (ZrO2, TZP-A), supplied by METOXIT high tech ceramics, stabilised with Yttrium oxide (Y2O3 < 5 wt%) and reinforced with aluminium oxide (Al2O3 < 0.25 wt%). This structural ceramic material exhibits a hardness of 1200 HV. To compare the tool performance commercial CVD-D coated WC drills and a solid PCD tools

Conclusions and outlook

This paper introduces the use of ultrashort-pulsed laser ablation to generate characteristic features on fluted drilling tools. By using two optical and five mechanical axes and appropriate tangential strategies, its ability to process complex 3D tool geometries at high precision in ultra-hard materials is demonstrated. The method is applied to produce solid PCD drilling tools with a number of characteristic features. Achieved cutting edge radii and surface roughness are in the range of or

Authors contribution

Maximilian Warhanek: practical implementation of the tangential laser process, tool manufacturing, measurement and tool testing, main writer of the article.

Christian Walter: Theoretical basis of tangential laser process for complex tool geometries, support during process implementation and supporting writer of the article

Matthias Hirschi: Theoretical basis of tangential laser process for complex tool geometries, implementation of CAM and CNC-control software for the tangential laser process

Jens

Acknowledgements

The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 314731. The authors gratefully thank Gregory Eberle (ETH Zurich), Josquin Pfaff (ETH Zurich) and Marcel Henerichs (ETH Zurich) for their support in this study.

Maximilian Warhanek completed his studies of mechanical engineering at ETH Zurich focussing on production technology and logistics. In his PhD studies, he specialises on the ultrashort-pulsed laser processing of hard materials, such as diamond and CBN. He is the coordinator of the EU research project DIPLAT (www.fp7-diplat.eu).

References (23)

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Maximilian Warhanek completed his studies of mechanical engineering at ETH Zurich focussing on production technology and logistics. In his PhD studies, he specialises on the ultrashort-pulsed laser processing of hard materials, such as diamond and CBN. He is the coordinator of the EU research project DIPLAT (www.fp7-diplat.eu).

Dr Christian Walter completed his studies of mechanical engineering at the Technical University Ilmenau. After some industrial experience as R&D engineer at Bosch Rexroth, he completed a doctorate at ETH Zurich on the conditioning of CBN tools by different laser processes. To date, Dr Walter is an engineering project manager in the SHL Group.

Matthias Hirschi is a trained design engineer and software engineer graduated from a Swiss college of higher education. In his professional career, he specialised on CAD/CAM development, at first at ABB and currently at EWAG AG.

Jens Boos is a trained industrial mechanic and studied mechanical engineering at the college of higher education Aachen. After five years experience as research assistant at RWTH Aachen and ETH Zurich, he is a laboratory manager at inspire AG Switzerland.

Jean Francois Bucourt Born on 09.12.1951, after studying law, Mr Bucourt took over the family industrial diamond tools factory. After focusing mainly on grinding technology for a long period, he expanded the business to PCD and CBN cutting tool technology. He looks back on 42 years of experience in conception, development, test applications and performance improvement in diamond and CBN grinding, cutting and superfinishing tools.

Prof Dr Konrad Wegener studied mechanical engineering at the Technical University of Braunschweig and wrote his PhD thesis on constitutive equations for plastic material behaviours. After an industrial career in the Schuler group, where he managed the engagement of the company in laser technology, he became full professor of production technology and machine tools at ETH Zurich in 2003. He is head of the IWF (Institute of Machine Tools and Manufacturing).

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