DIPLAT consortium - Comparative analysis of tangentially laser-processed fluted polycrystalline diamond drilling tools : CIRP Annals -Manufacturing Technology - 23 June 2016

« 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 12ps, infrared laser source with an average power of 35W 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. « 

DIPLAT consortium -The influences of pulsed-laser-ablation and electro-discharge-grinding processes on the cutting performances of polycrystalline diamond micro-drills - CIRP Annals - Manufacturing Technology - 08 April 2016

« Geometrically complex micro-tools are manufactured via processes which can affect their cutting performances. This paper studies the effects pulsed-laser-ablation and electro-discharge-grinding on polycrystalline diamond matrices and their binder phases at nanometric scales, revealing distinct differences in the resulting substructures. The dissimilarities in micro-scale material removal phenomena of these manufacturing processes combined with their effects on the generated surface topographies and cutting-edge geometries can significantly influence the wear and cutting performance of micro-drills. A study on the micro-drilling of a ceramic matrix composite workpiece material confirms that pulsed-laser-ablation of composite diamond structures offers a step-change in the fabrication of micro-tools. »

DIPLAT consortium - A study of an improved cutting mechanism of composite materials using novel design of diamond micro-core drills-CIRP Annals - Manufactoring Technology -30.October 2014

« Core drilling at small diameters in carbon composite materials is largely carried out using diamond electroplated tools consisting of hollow shafts and simplistic geometries that are likely to work in an abrasional/rubbing mode for material removal. The paper reports a step change in the performance of small diameter core drilling by facilitating a shearing mechanism of the composite workpiece through the utilisation of a novel tool design. This has been achieved by laser producing core drills from solid polycrystalline diamond, incorporating controlled cutting edges where the geometries are defined. To evaluate the efficiency of the shearing vs. abrasion/rubbing cutting mechanisms, a critical comparison between the novel (defined cutting edges) and the conventional electroplated tools (randomly distributed micro-grains) has been made with reference to thrust forces, tool wear mechanisms and their influences on the hole quality (e.g. delamination, fibre pullout). This work has been augmented by studies using high-speed thermal imaging of the two tool types in operation. The examinations have shown that, based on the concept of defined cutting edges in solid diamond, there is the possibility to make significant improvements in core drilling performance, (ca. 26% lower thrust force, minimal tool surface clogging, lower drilling temperatures) resulting in improved cleanliness of fibre fracture and a reduced tendency of material delamination. »