Papers by Keyword: Dry Drilling

Abstract: In past few decades, a lot of research has been done in the field of machining to improve the quality of machined surface. Out of these machining operations, drilling is widely used in the areas of marine and aerospace for assembly requirements. Titanium alloy Ti-6Al-4V, owing to its vast applications, is regarded as an important material for these industries. Ti-6Al-4V is categorized as difficult to machine material. Based on above stated facts, an experimental study was conducted on the dry drilling of Ti-6Al-4V. The objective of this study was to establish the correlations between drilling parameters such as feed rate and spindle speed, and quality of machined surface which is evaluated in terms of drill hole diameter deviation, exit burr height and surface roughness.

Abstract: Near-net shape austempered ductile iron (ADI) castings can be considered as a significant economic advantage to the increasing industrial demand for cost and weight efficient materials. However, due to microstructure induced inherent properties, ADI is considered as hard to machine material. The present paper thus investigates the interaction between the microstructural characteristics of ADI and wear mechanisms of PVD-coated carbide tools. The inherent properties of ADI materials are the function of its microstructural characteristics (retained austenite volume content and its carbon content, ferritic cell size, etc.) which can be controlled by the austempering parameters. Experimental studies of dry drilling of different ADI materials with the PVD-coated carbide tools were carried out at a cutting speed of 60 m/min and at a feed of 0.15 mm/rev. The wear mechanisms of the cutting tools were studied by using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis techniques. The obtain results revealed the evolution of crater wear as the main wear mode. In addition, it provides the key findings aims to correlating the machining characteristics of ADI with its microstructure and production conditions.

Abstract: Currently, Carbon Fiber Reinforced Non-Metal Composites (CFRC) are commonly applied in structural components of aircrafts. Frequently, these elements need to be drilled for their assembly in the final product. Chips close to powder are formed when this kind of material is machined. Because of this, drilling processes are mostly performed in absence of cutting fluids. High quality requirements are demanded for holes due to the fact than those elements are placed in key components of the aircrafts. The most relevant defects that can be produced in the dry drilling of CFRC are located in the both tool input and tool output. These defects are known as Break-IN (B-IN) and Break-OUT (B-OUT). This paper reports on the results of a comparative study of different methodologies for evaluating those defects. First of them is based on the analysis of the diameter deviation. Second procedure is based on the damaged area. Both parameters have been measured making use of image analysis techniques. Obtained results have revealed that damaged area based method is more sensitive to hole changes.

Abstract: In this work, the energy required during the dry drilling of PEEK GF30, a thermoplastic material, polyether-ether-ketone, reinforced with glass fiber, is analyzed. Three different types of drills are used, respect to material and geometry, under nine cutting conditions based on cutting speed of 6000, 7000 and 8000 rpm, and feed rate of 300, 400 and 500 mm/min. The results show that similar outcomes are obtained with two drills, one of them, wolfram carbide with coating of TiAlN and another of wolfram carbide with point of diamond. This aspect is important due to the economic advantages of the first drill respect to the second one. An analysis of variance, ANOVA, shows that the drill type is the more influent factor, and that the optimal situation can be given with drill of WC and point of diamond with the higher cutting conditions. The energy required, assigned to the torques, is superior to 98%, in each case, question that could be taken in account in the tools design.

Abstract: Aluminum alloy is widely used in industry and various researches has been done on machiability of this material mainly due to its low weight and other superior properties. Dry machining is still interesting topic to reduce the cost of manufacturing and environmental contaminations. In present study dry machining of Al 2024 investigated on tool life, tool wear mechanisms, hole quality, thrust force and torque. Different types of high speed steel (HSS) tools utilized at constant feed rate of 0.04 mm/rev and cutting speeds within the range of 28 and 94 m/min. Experimental results revealed that HSCo drills, performed better than HSS drills in terms of tool life and hole quality. The main wear mechanisms which analyzed by scanning electron microscope found abrasive and adhesion wear on flank face, besides, BUE observed at chisel and cutting edges. However tool wear and BUE formation found more significant at high cutting speed. In terms of thrust force, two facet HSCo tools, recorded higher thrust force than four facet HSS drills.

Abstract: Drilling experiments of CFRP/Ti6Al4V laminated stack board were carried out use of a TiAlN-coated cemented carbide drill and a TiAlCr/TiSi-coated cemented carbide drill. In the experimental conditions described herein, tool life is longer for lowered feed speed, and a TiAlCr/TiSi-coated cemented carbide drill has longer life than the other. Additionally, the cooling performance between dry process and water-mist-cooling were compared. Regarding water-mist-cooling, although the thrust is smaller, chips are much harder. They also adhere to the drill margin and impart damage to the CFRP wall of the hole. For a number of holes less than 50, water-mist-cooling reduces tool abrasion. However, the abrasion increases suddenly for hole numbers greater than 50. Accordingly, for the number of holes drilled well over 50, tool life is longer in dry processing than in water-mist-cooling.

Abstract: Secondary tool adhesion wear is commonly provoked by two effects, whose nature depends on the placement of the adhered material. The so-called Built-Up Layer (BUL) is formed on the tool rake face and the Built-Up Edge (BUE) is developed on the cutting tool edge. These effects can be developed by different causes depending on both the cutting conditions and the material to be machined. In this work, X-Ray Photoelectron Spectroscopy (XPS) has been used to analyze the built-up layers formed during the dry drilling processes of aeronautical Ti-6Al-4V alloy. Changes in the Ti oxidation state in each layer have allowed proposing a BUL formation mechanism based on chemical reactions of the workpiece material during the drilling process. Effects of these reactions have been contrasted through the XPS analysis of the chip generated in the process. In parallel, SEM and EDS have been used as complementary techniques for obtaining further information about the BUL nature.

Abstract: The graphite-like carbon (GLC) coating was deposited onto high-speed steel (HSS) twist drills by magnetron sputter ion plating technique. The drilling tests were performed on the ferrous metal under dry cutting conditions. By the analysis and comparison of the flank wear and the drilling forces on drills, the cutting performance of GLC coated HSS tools was researched. The results show that GLC coating with high hardness and low friction coefficient, due to its good adhesion and match with HSS substrate, can significantly improve the cutting performance of HSS twist drills, prolong the tool life, decrease the drilling forces in drilling the ferrous metal. And its cutting performance is better than the hard coated drills in the lower speed, but its thermal stability is inferior to the hard coated drills in the higher speed.

Abstract: This paper presents a study of the thrust forces in the aluminium alloy, UNS A97050-T7. The measurement of these forces during the dry drilling in plates is evaluated under cutting different conditions and in through and blind holes. The experiments have been performed in a CNC milling and HSS Co drills have been utilised with unlike diameters (6.3 mm and 4 mm). The thrust forces have been measured by means of a piezoelectric dynamometer. In addition, the results have been compared with theoretical forces, obtained by the Kronenberg equation. The ANOVA study has allowed confirming the similitude between the forces obtained, independently of number of holes drilled, with the exception of through holes of 4 mm, in whose case the Kruskal-Wallis test has corroborated the dissimilitude. Moreover, the comparison with Kronenberg forces is coherent for diameters 6.3 mm, but it is very different for diameter 4 mm. Thus, the results respect to through and blind holes are dependent of diameter of drill, and also the differences found in the theoretical forces. The high variability of the forces for minor drills, in through and blind holes, points to an inadvisable use in this material.

Abstract: Carbon Fiber (CF)/Metallic Alloy (MA) laminar structures, also known as Fiber Metal Laminates (FML) allow diminishing the airship weight. Because of that the use of these materials is growing continuously in the aerospace industry. These composites materials need to be drilled because of the assembly requirements in the different airship elements. The most common problems that can appeared when those structures are machined are related with the interaction of the tool with dissimilar materials, which need different cutting parameters for the optimized machining process. This work reports on the results about a study of the dry drilling processes of hybrid composites Carbon Fiber/aluminum alloy, and especially CF/AA2024.