Papers by Keyword: Machinability

Abstract: Additive manufacturing by laser powder bed fusion (LPBF) is increasingly applied to aluminium alloys; however, the resulting surface quality and machining behaviour remain critical challenges, particularly when post-processing is required. In this context, the interaction between LPBF process parameters and advanced cooling strategies during machining remains largely unexplored.This study examines the impact of cryogenic machining on the surface integrity of LPBF-produced AlSi7Mg components, fabricated with varying layer thicknesses. Specimens were machined under fixed cutting parameters using either conventional flood cooling or cryogenic cooling. Cutting forces, surface roughness, defect morphology, and subsurface microstructure were systematically evaluated.Cryogenic cooling consistently reduced cutting forces and improved surface quality, effectively suppressing tearing formation. In contrast, under flood cooling, the influence of the microstructural differences induced by layer thickness remained significant, with increasing LPBF layer thickness further enhancing both surface and subsurface integrity. Overall, the results reveal a strong interaction between LPBF parameters and cooling strategy, highlighting the unexpectedly beneficial role of cryogenic machining in improving the surface integrity of LPBF-processed AlSi7Mg alloys.

Abstract: Abrasive Waterjet Machining (AWJM) has significant advantages, such as being environmentally friendly, used for machining hard-to-cut materials, and do not cause a heat-affected zone. More machining tests are needed to understand the concept of material machinability in AWJM to increase process flexibility and produce parts with higher productivity, better accuracy, and surface quality. This paper presents drilling and slotting experiments through different metallic materials at fixed machining conditions to evaluate their machinability using AWJM. It introduces new machinability indices that arrange the tested materials concerning their machinability rating. Drilling indices include volumetric removal rate (VRR), penetration rate (PR), specific removal rate (SRR), and taper angle (TA). The paper correlates VRR, PR, drilling power, and Young’s modulus of the tested materials. In the case of slotting, VRR, kerf taper angle (TA), and the average surface roughness, Ra, were measured and used as indices of machinability. Cost analysis was also performed to introduce an economical index of machinability for both AWJ drilling and slotting AWJM operations.

Abstract: Composites are being used since decades and imparting excellent properties comparatively. It may be used in numerous industries because of its light weight and specific strength. Machinability of these materials is a concerned aspect. Conventional and The composites have been machined using unconventional machining techniques. Conventional methods are less suitable than non-conventional quoting the best surface finish and ability to machine complex parts. This article investigates the suitability of thermo-electric process for the machining of composites for higher surface quality and material removal. It includes the study of machining by die sinking, wire cut, powder mixed electric discharge machine in different matrix based composites along with the variation of reinforcement. Electric Discharge Machining (EDM) finds its suitability in machining of different metal matrix composites (MMC) more than the Polymer Matrix Composite (PMC) and Ceramic Matrix Composites (CMC). Variation in input parameters listed as Pulse duration, Voltage, Peak Current and Polarity is studied to obtain the optimum resulting parameters as Material Removal Rate (MRR), Surface Roughness (SR), Electrode Wear Rate (EWR) and Kerf Width. Material removal in PMC is 16% more in parallel fibre direction than with perpendicular. Low electrical conductance and high hardness of CMCs limits the use of EDM while natural ceramics are found more suitable for machining. Gap voltage, pulse on time and current are found most crucial in machining MMCs while quantifying material removal and surface roughness.

Abstract: The 3D printing technology is being applied more and more every day, this is a consequence of its applicability and low waste generation, becoming one of the best options to obtain good quality pieces. Sometimes, post machining processes are necessary to fulfil tight tolerances or achieve complex geometries by means of the connection between different pieces printed using this technology. The field of knowledge and studies focused on 3D printing is in constant evolution. There are plenty of materials that can be used to apply 3D printing technology. Among them, PEEK is one of the best options when good mechanical properties are required. Being applied in aeronautic or automobile industry, is also used in biomedical applications, such as prosthesis or mechanical components among others. Within the machining processes, milling, turning, and drilling are the most widespread. Orthogonal cutting is a machining process in which the cutting edge of the tool is perpendicular to the cutting speed, and it is commonly used when a simple and pure study of the mechanism behind a material removal process is required. In this study, tests that analyze the orthogonal cutting on 3D printed PEEK samples using different orientations (0o and ±45o) have been conducted. The influence of cutting speed (30, 60 and 90 m/min) and depth of cut (50, 100 and 150 μm) is studied through the analysis of cutting forces and surface finish quality. As a general approximation, it can be seen that the fiber orientation affects significantly to the forces monitored but unexpectedly, lightly to the surface finish.

Abstract: This paper investigates the machinability of Selective Laser Melted 17-4 Precipitation Hardening Stainless Steel (17-4 PH SS). For this purpose, turning tests were carried out on wrought and SLM specimens and the results were compared. Wear tool, surface roughness, surface integrity and chip morphology were analyzed for both materials. For the tested cutting conditions, the machinability of the SLM material was inferior to that of the commercial material. Dissimilarities in machinability between both materials are a consequence of variations in their microstructures resulting from the manufacturing process.

Abstract: Aluminum matrix hybrid composites reveal excellent mechanical behavior compared to traditional materials for a wide range of conditions and applications. However, the machining of this kind of composite is a challenging job due to its improved mechanical hardness. The problems faced during the cutting of these composites are increased machining forces, poor surface quality, and increased tool wear. Many types of research are still in progress across the world to overcome these issues by using a variety of inserts and processing constraints. So, this paper is mainly focused on the study of the machinability of aluminum hybrid composites. The composites are synthesized by employing stir casting via varying the filler content, stirring duration, and speed. The fabricated composites are machined using coated and uncoated carbide inserts. Machining forces, surface roughness, and insert wear are assessed to learn the machinability of these materials by varying the machining constraints. Taguchi analysis was employed to assess the effect of the constraints on the retorts. Keywords. Aluminum Hybrid Composites, Stir Casting, Machinability, Taguchi Analysis.

Abstract: This work emphases on characterization and evaluation of machinabity characteristics of a novel hybrid Aluminum Metal Matrix Composite (AMMC) developed through two-step stir-casting method by reinforcing constant amount of Beryl (6%) and varying quantity of Graphene nanoPlatelets - GNPs (0%, 1% and 2%). Morphological analysis result shows the presence of dendritic arms and homogeneous distribution of the Beryl and GNPs in Al7075 matrix. Machinability (turning) characteristics of the developed hybrid composite were studied in detail besides optimizing the machining parameters employing Taguchi technique. The objective was to establish a correlation between cutting parameters such as cutting speed, feed rate and depth of cut with, tool wear, and surface roughness on work piece. In the present study, performance of multilayer hard coatings (TiC/TiCN/Al₂O₃) on cemented carbide insert for machining of Al7075-Beryl-GNPs. An attempt has been made to analyze the effects of process parameters on machinability aspects using Taguchi technique. Response surface plots are generated for the study of interaction effects of cutting conditions on machinability factors. The correlations were established by multiple linear regression models. The linear regression models were validated using confirmation test.

Abstract: The three cutting edge drills are not the most common drills, nevertheless, are characterized by superior stability, excellent precision and finishing, due to the intersection of three cutting edges at one point. In general, stainless steels are considered as difficult to machine materials due to their tendency to work harden, their toughness and relatively low conductivity, leading to poor surface finish, poor chip breaking and built-up-edge formation. In the case of duplex stainless grades, the high strength, and the very good corrosion resistance, only compared with austenitic steels, make these materials as an alternative to the austenitic stainless steels, with superior mechanical properties. In this study, the performance of the drills with two and three cutting edges were evaluated in the drilling of duplex stainless steels, when low-pressure external cooling or high-pressure internal cooling were applied. Whether used drills of two or three cutting edges, the most important factor to increase the number of holes made, is the use of high-pressure internal cooling, in detriment of external low-pressure external cooling. The drills of three cutting edges have better results in roughness and dimensional tolerance of the holes. However, these drills proved to be more fragile and more sensitive to the cutting parameters. The use of three cutting edges drills is recommended for situations where hole quality is more important, while two cutting edges drills is recommended for situations where productivity is the main objective.

Abstract: One of the critical physical and mechanical properties of metals and alloys is the suitability for abrasive machining. Machining by abrasive tools is the final operation that sets the desired macro-geometry parameters of processed blanks and microgeometry parameters of processed surfaces such as roughness and length of a bearing surface. Abrasive machining determines the most important physical and mechanical parameters of a blank surface layer, i.e. stresses, phase composition, structure. Machinability by abrasive tools depends on the machining performance affected both by the blank material properties and various processing factors. In our previous studies, we proved that during abrasive machining the metal microvolume affected by abrasive grains accumulates energy. This energy is used for metal dispersion and is converted into heat. According to the theoretical studies described herein, one may note the absence of a reliable and scientifically valid method as well as measuring instruments to determine the machinability of metals and alloys by abrasive tools. For this reason, we suggested a method simulating the effect the multiple abrasive grains produce in a grinding wheel, and enabling us to identify machinability of metals and alloys, select the most efficient abrasive materials for machining of the same, and form the basis for development of effective grinding operations.

Abstract: The mechanical properties like hardness, machinability and electrical conductivity of nanocomposites are analysed in current work. Inferable from its good castable property, A356 has been picked as matrix material and due to proximity with reference to density; nanosilicon carbide (SiC) is chosen as reinforcement material. A novel technique “Ultrasonic assisted cavitation” is followed for the synthesis of nancomposites for uniform dispersion and better properties. By keeping the size of reinforcement as 50 nm and varying the quantity from 0.1 to 0.5 by wt%; it is perceived that the hardness & drill thrust forces are increased and electrical conductivity is decreased when equated to pure alloy.