Papers by Keyword: Drilling

Abstract: Carbon fiber-reinforced plastic has been applied in various industrial areas due to outstanding mechanic characteristics including high strength and hardness as well as light-weight. For the mechanic combination after the CFRP molding, hall processing is required. In this study, generally used carbide drill and TiAIN coating carbide drill were used to proceed the experiment. Afterwards, carbide drill where point angle was changed into 90° was manufactured while evaluating thrust force and tool wear. In the experiment of carbide drill and TiAIN coating carbide drill, thrust force was reduced when major axis rotating speed increased. However, it was not much influenced by changes in moving speed. In addition, TiAIN coating has not much influenced on the processing feature. Tools with point angle changed into were measured 90° with lower tool wear and thrust force compared to two other tools while obtaining outstanding tool performance.

Abstract: Graphitized steels are claimed to perform excellent in machining processes. They therefore can be considered as environmental friendly alternatives to the widely used Pb-alloyed steels. Due to liquid metal embrittlement and in-situ lubrication Pb improves machinability in a narrow tool-chip interface temperature window corresponding to low machining speeds. Although graphite inclusions are also supposed to generate in-situ lubrication, the mechanism and the corresponding optimum working zone is not very clear. The present work applies a new test methodology (including in-situ tribology, analysis of material flow and chip formation, optimum working zone analysis) to investigate the effects of graphite inclusions on turning and drilling operations. A Pb-alloyed low carbon free-cutting steel and Pb-alloyed case hardening steel were used as reference steels.

Abstract: The preparation, characterization and machinability of resin hybrid GFRP composites are presented in this paper. It is made up of Glass fiber and the mixture of epoxy and polyester resin. It was prepared by the traditional layout technique with the usage of Glass fiber. The weight percentages of GFRP are 0, 20 and 40 having the composition of polyester and epoxy resins. The study of ASTM revealed the variation of break loads and shear strength for three different combinations of epoxy and polyester resins. The main disadvantage of this method is that it resulted in poor dimensional stability and surface roughness. Our main goal was to minimize the surface roughness. There are certain drilling parameters such as composite material, point angle, spindle speed and feed rate during drilling of resin hybrid GFRP which are to be focused to minimize the surface roughness. The experiments were conducted and the results were obtained using Taguchi’s L9 orthogonal array design. It was further analyzed using Signal-to-noise Ratio. Investigating the cutting characteristics of Resin hybrid GFRP proved to be mandatory. This was done by using the Analysis of variance (ANOVA). The Minitab 15 software was used to determine the correlation by linear Regression methods. The value obtained was subjected to a recheck to check the percentage error. The percentage error between the experimental and theoretical value was minimal.

Abstract: There have been few reports on the drilling of microholes on rod end faces by cutting, which can be employed for fabricating micronozzles or microneedles. Such drilling was therefore attempted in the present study using a micro turn-milling machine with the tool and workpiece axes being parallel. The drilling was performed on the end faces of brass rods with cemented tungsten carbide micro-cutting tools processed by electrical discharge machining (EDM). As a result, a microhole 12‍ μm in diameter was successfully drilled using a 10-μm-diameter tool at a feed speed of 0.5‍ μm/s. The feed speed could be increased to 25 μm/s for a tool with a diameter of 20 μm and body length of 50 μm.

Abstract: In this research work, an attempt is made to develop the on-line wear state monitoring system during drilling process on Vertical Machining Centre (VMC). The main objectives of the present work is to predict the drill wear states of High Speed Steel (HSS) drill bit during the drilling of a AISI 1040 Steel work piece using standard data acquisition software Lab VIEW by the application of Virtual Instrumentation (VI). The drill bit wear states were analyzed using spindle motor cutting current signals. The effective drill wear model have been developed using spindle motor cutting current signals and the various cutting parameters through Lab VIEW, to predict wear states of the drill-bit. The developed on-line drill wear process monitoring system has been used for the continuous monitoring of the drill-bit status, and to exhibit the drill wear states. It was found that the developed model show a good agreement with the experimental data where the deviation in drill-bit wear is less than 7% for varying cutting conditions.

Abstract: Natural Fiber-reinforced epoxy composites have a potential of lightweight structural materials used in various engineering applications owing to its excellent properties. Present paper investigates the mechanical properties of glass fibre, coconut fibre and human hair reinforced epoxy hybrid composite. In this work, epoxy resin with various layers of reinforcement added by using hand layup technique. The composite is subjected to mechanical testing. Machinability studies were performed based on the drilling experiments. TiAlN coated solid carbide (SC) and High speed steel (HSS) drills were used in the drilling experiments and made a comparative study on the output parameter. Solid carbide tool has a lower thrust force with feed rate being the most influential parameter on thrust force.

Abstract: The need for eco-friendly materials and non-polluting processing techniques has made natural fibre reinforced polymer composites as potential candidates to replace GFRPS and CFRPS in semi structural applications. Ground nut shell and luffa fibre are easily available in the market at low cost. Polymer composites consisting of 30%, and 40% volume fractions of a hybrid reinforcement containing groundnut shell and luffa fibre in epoxy resin were fabricated by hand lay-up technique with varying process parameters, the variation in the mechanical properties such as tensile, compressive, flexure and impact strength are studied. The optimum mechanical properties were obtained in 40% of fiber volume fraction of treated fiber composites the machinability study was performed by drilling experiments using a drilling machine with drill tool dynamometer. Two input parameters, cutting speed and feed rate and the one output parameter, thrust force, were used for the drilling process. TiAlN coated solid carbide and hss drills were employed in the drilling experiments and a comparative study was made based on the output parameters. Solid carbide resulted in lower thrust force values and feed rate proved to be the most influential parameter on thrust force.

Abstract: Based on the analysis of trends in the development of aviation and rocketry and ground transportation, the prospect of use of high-alloy steels, and titanium-based alloys with high strength, heat-and corrosion-resistant properties is established. It is shown, that high strength and elasticity of mentioned alloy groups adversely affect the dynamics of cutting process and the resistance of the cutting tool. Processing of small diameter holes is especially difficult due to the small longitudinal stability of the instrument, chip evacuation problems, grooves sticking to the surface almost zero cutting speed near the core. The results from the analysis of works of domestic and foreign scientists have shown that the message sent to the drill by ultrasonic vibrations of the small amplitude reduces axial force and cutting moment due to reduced friction caused by local thermal effects and relief of dislocation motion. At the same time, it is stated that the stable results of the effectiveness of ultrasound were not received in relation to the small diameter end tools until recently because of additional dynamic loads reducing the longitudinal stability and therefore it is impossible to report the instrument optimal oscillation amplitude to facilitate cutting. The working hypothesis of increase of efficiency of the ultrasonic drilling of small diameter holes proposes to consider correlation frequency supplied to the ultrasonic instrument, structural parameters and physical and mechanical properties of the material and to drive oscillations in the plane of the main cutting edges which would significantly reduce the magnitude of the oscillation amplitude. Experimental studies on ultrasound indentation, micro cutting and drilling titanium alloys have confirmed this hypothesis. It was established that at the moment the drill receives a message with the oscillation frequency of 30 kHz when machining titanium alloys, the axial cutting forces decrease by 70 – 80 % and the tool life increases by 2.2 times.

Abstract: In the context of high tool wear concerning machining of carbon fiber reinforced plastic (CFRP), it is desirable to study new processes and techniques which are able to lower the wear and thus induced costs. Therefore, this article presents a novel minimum quantity dry lubrication (MQDL)-process. It delivers minimal amounts of graphite powder, using compressed air as a conveying medium to its operating area between the tool and workpiece. For this purpose a prototypical fluidisation device for conditioning, dosing and conveying the graphite powder was built. The investigations have shown that the constructed prototype is already able to deliver tiniest amounts of graphite mass flows (less than 3 g/h) reliably. Furthermore, first results of drilling tests with internal MQDL-supply are presented. The cutting edge radius of the solid carbide drilling tools has been chosen as the wear measuring quantity. With the use of MQDL at drilling CFRP, a clear reduction in wear is shown, in comparison to pure compressed air. Finally the article shows further research and application areas of this new MQDL-technology.

Abstract: The modelling of machining operations aiming at the compensation of thermal effects regarding workpiece distortion requires detailed knowledge of the thermal impact of the examined process. The objective of this paper is therefore to form an empirical basis for the modelling of the heat flux into the workpiece in drilling of steel. In order to achieve this goal the temperature matching technique in combination with two dimensional thermographic measurements was utilised. The moving heat source was characterised as a primary heat source with a constant heat flux density near the cutting zone and a secondary declining heat source on the bore hole wall. With an iterative approach it was possible to match the simulated temperature fields very closely to the measured temperature fields. The evaluation of the thermal impact of the drilling process with varying machine parameters yielded additional insight into the generation and distribution of thermal energy in drilling. The lowest overall heat partition to the workpiece was observed at the higher feed rate in combination with the lower cutting speed where the heat partition in the cutting zone as well as heat transfer to the bore hole wall are minimal.