Papers by Author: Julfikar Haider

Abstract: Broaching is a precision multipoint metal removal operation normally employed for manufacturing variety of complex parts having either internal or external features. Broaching can produce high precision and good surface finish at a high metal removal rate. The unique feature of a broach tool is that the feed/depth of cut for the teeth is built into the broach unlike other cutting tools. The tool design (e.g., rise per tooth and tooth geometry) play a vital role in the broach performance. A specially adapted machine tool modified to investigate a single broach tooth has been used. Cutting forces and material removal rate have been measured during experimental work for different combination of broaching parameters and broach tool geometry. The effect of the parameters on the surface quality produced has been established. The characteristics of chips formed have also been defined. Finally, optimum tooth geometry and rise per tooth have been recommended for tool performance, broached surface quality and efficient chip formation. The information provided in this paper will be beneficial for broach tool designers and manufacturing engineers.

Abstract: The benefits of applying advanced coatings on both single point and multipoint cutting tools such as improvement of productivity, tool life, machined surface quality etc. have been realised by the surface engineering researchers [1], commercial coaters [2-4] and end users [5]. The demand for advanced coatings in cutting tool industries is continually growing to meet the challenges of high speed machining, dry machining, near net-shape machining, machining of hard-to-cut materials etc.. Advanced coatings with excellent properties on flat coupon in a laboratory deposited by modern deposition technologies should not be taken for granted in improving the performance of complex shaped cutting tools [6] in aggressive cutting environments. This is because the end performance of coated cutting tools is not only dependant on the coating itself but also on the tool substrate material, geometry, surface finish and cutting edge conditions prior to coating deposition. The paper presents case studies with examples of successes and failures of advanced coatings on different multipoint cutting tools (e.g., milling cutters, bandsaws, circular saws, holesaws etc.). The future strategy for developing successful coating technology for cutting tools should be directed towards adopting a systems approach to bridge the communication gap amongst the cutting tool manufactures, tool coaters and end users.

Abstract: Physical Vapour Deposition (PVD) technology, particularly magnetron sputtering process, enjoys the competitive advantages of depositing different new generation coatings (e.g., multicomponent, multilayer, graded, composite etc.) on three-dimensional objects (substrate) with excellent mechanical and tribological properties. In an industrial-scale sputtering chamber with a limited number of active magnetron sources (target) on the chamber wall, the density of coating species from different sources would not be uniform everywhere around the chamber. As a result, at a constant speed of rotating substrate table in a single revolution, the instantaneous deposition rate will be highest in front of the active targets and lowest when the substrate moves away from the active targets. In this work, a method of controlling the rotational speed (i.e., slower speed in front of active targets and faster speed in front of inactive targets in a revolution) of a substrate table installed in a magnetron sputtering chamber has been developed in order to improve the deposition rate of a multicomponent TiN+MoSx coating. The mechanical and tribological properties of TiN+MoSx coating have also been characterised to assess the beneficial effects of adding solid lubricant (MoS2) in hard TiN coating.