Papers by Keyword: Machinability

Abstract: Machining hard to machine materials using conventional method of machining has proved to be very costly as these materials greatly affect the tool life because of poor machinability. One material that requires considerable study is Titanium which is a relatively lightweight material and provides excellent mechanical properties. The major problems in machining Titanium Alloys are the high cutting temperatures and rapid tool wear. Machining of Titanium using techniques like Laser Assisted Machining and Plasma Assisted Machining have proven to give high productivity rates, but the costs associated are very high. The main objective of this work is to develop a method for improving the machinability of Ti-6Al-4V using Work Piece Pre-Heating technique by using Conventional Machining with standard tools. Design of experiments was performed using Taguchi’s robust design. The machining operation was performed at elevated temperatures using oxy-acetylene flame. The tools used are Coated and Uncoated Carbide Tools. Based on the tool wear values obtained with different cutting conditions, it is concluded that this technique is feasible with the coated and uncoated carbide tools to machine titanium components commercially.

Abstract: The knowledge about machinability indices for distinct machining processes allows finding the most appropriate values of the relevant factors for definite machining operations. Several criteria can be used to characterize machinability, such as the tool wear, the magnitude of the cutting forces, the roughness of the machined surfaces, or the shape of the chips that are formed during the machining process. One of the methods for studying the machinability is based on the analysis of drilling operations that are made under constant feed force. A drill press is probably the most readily available device to implement an experimental setup for drilling machinability tests. In normal operation, however, the chip accumulation at the dead end of the machined hole has a detrimental impact on the results of machinability tests, so that an improved setup was designed. A two-level, full factorial experiment with three independent factors (the drilling tool diameter, the rotational speed of the spindle and the feed force) has proven the suitability of the new experimental setup. Using it, we could find a power-type empirical model that explains the impact of the input factors in the depth of a hole that is machined in a pre-defined time interval.

Abstract: Parametric optimization model was made by now for abrasive water jet process, only for materials with uniform hardness. Pieces, subject to deep carburized treatment with high hardness in layer and softened in core, have a different behaviour and it is necessary to estimate new values of the system processing. Experiments consisted in cutting with abrasive water jet of rectangular samples with 10 mm thickness and deep carburized layers with 8 mm thickness, obtained as a result of deep carburized heat treatment. Abrasive water jet, initially meets the carburized layer with 62 HRC, after perforation followed the layer with fine sorbite structure (30 HRC). The different hardness causes a change in the trajectory of abrasive particles, determining deformations and micro cracks in materials to the limits of carburized layers. Choosing an optimal cutting regim becomes important not only economically, as well as qualitative. Measurements allow drawing conclusions that can be generalized to the materials with different hardness.

Abstract: While machining a material, it is essential to understand the characteristics of work material for choosing the favorable condition of the material, appropriate cutting tool, machining parameters to achieve desired optimum output. Accordingly, researchers always devise their studies to improve the machining processes resulting in enhanced product quality and increased production rate simultaneously. Such machining studies on super-alloys attract significance, since they are oriented towards overcoming the difficulties involved in machined out a component. Generation of heat in the cutting zone and high cutting forces on the tool being experienced while machining super-alloys, are due to poor thermal conductivity and work hardening characteristics. Above factors contribute to two basic problems viz. the inability of the tool materials to give long tool life and the metallurgical damage to the machined components due to induced stresses. Among the super-alloys, Inconel 718 is the widely used heat resistant super alloy (HRSA), which withstands stringent operating conditions in high and cryo temperature environments for longer duration. Studies on understanding the behavior and the relationship between work piece material, cutting tool materials, cutting conditions and the process parameters is an essential requirement for establishing and optimizing the machining process and the present work is tailored towards this objective. In this work, Inconel 718 alloy was subjected to turning experiments and the experimental data collected was used for constructing empirical models whose performance was assessed through statistical approach. It is established that the models developed could be used for predicting the output parameters for a set of input of parameters through 2-D (surface) and 3-D (contour) plots.

Abstract: This investigation was done to study machinability during drilling on sandwichlaminates. Vetiver and jute were used as natural fibers and glass was used as synthetic fibers in vinyl ester matrixin the form oflaminatesby varying the fiber content in each laminate.The laminateswere drilled during which spindle speed, spindle feed rate, tool point angle and sample laminate weremodified using D-optimal design technique. During drilling of each hole, thrust force impressed and torque developedwere noted as outputs.The outputswere optimized to observe best drilling conditions.A fuzzy model was created and its predictions for trialconditionswere noted. A comparison between trial values, regression values and fuzzy values was made. Confirmatory trialswere madefor optimumset of runs and outputswere again noted.The percentage of error between the model, confirmatory trials and fuzzy were found to be meagre and hence concluded that the optimization was satisfactory.

Abstract: CFRP and Titanium alloy, which are known as difficult-to-cut materials have been widely used as structural material in aviation industries. The orbital drilling is one of an effective drilling technique for the industries. However this technique has some disadvantages such as increase of cutting force due to cutting with tool center point, inertial vibration generated by revolution and high installation cost. In order to improve the disadvantages, we have invented a new drilling technique which is called inclined planetary motion milling. The inclined planetary motion milling and the planetary mechanism drilling has two axes of cutting tool rotation axis and revolution axis. Cutting tool rotation axis of the orbital drilling is moved parallel to the revolution axis in eccentric. On the other hand, in the case of the inclined planetary motion milling, eccentric of the cutting tool rotation axis is realized by inclination of a few degrees from the revolution axis. Therefore, the movement of eccentric mechanism can be reduced by comparison with the orbital drilling because inclined angle is smaller than eccentricity of the cutting tool tip. As a result, eccentric mechanism can be downsized and inertial vibration is reduced. In the study, a geometrical cutting model of inclined planetary motion milling was set up. The theoretical surface roughness of the inside of drilled holes by use of two types cutting tool geometry were calculated based on the model. And cutting experiments using the new prototype for CFRP were carried out in order to evaluate the effect on machinability with change of cutting point atmosphere. In addition, optimal cutting condition was derived according to cutting experiments for titanium alloys utilizing the orthogonal array.

Abstract: Recently, carbon fiber reinforced plastics (CFRP) are expected to be used more in the aerospace and automotive industries, because of their outstanding lightweight material characteristics and tensile strength [1][2]. Underlying this are problems closely related to improvement of the earth’s environment. However, a mechanical property is influenced by the difference in the distribution state of the carbon fiber, and the adhesion intensity of the binding material. Moreover, they have the characteristic of intense anisotropy, strength wise depending on the orientation of the carbon fibers [3][4]. Therefore, CFRPs are considered difficult-to-machine materials [5], because the surface finish deteriorates according to the carbon fiber orientation. Establishing the optimal cutting conditions to solve such problems also from an economical viewpoint is essential. In our study, end milling operations of different carbon fiber orientation CFRP composite material were investigated with three kinds of different helix angle end mills. Evaluations were based on the surface finish, cutting force and cutting temperature. Moreover, the relationships between the carbon fiber orientation and the machining operations were determined. We earlier evaluated the machinability from the relationship between carbon fiber orientation and tool helix angle by down-cut milling to solve these problems [6]. In this study, machining operations of different carbon fiber orientation CFRP composite material were investigated with three kinds of different helix angle end mills by up-cut milling. Evaluations were based on the surface finish, cutting force and cutting temperature. Moreover, the results of this experiment were compared with the results of down-cut milling.

Abstract: A fret-saw blade is commonly used in micromachining or curve machining of various woods. However, there is a curvature limit for machining of free-form surfaces because a fret-saw blade has a thickness of several hundred microns and a width of several millimeters. Additionally, cutting with a fret-saw blade produces much wood meal as chips. If a fine wire cutting tool is used, more flexible machining, such as machining of high curvature free-form surfaces, is possible and the quantity of chip production drastically decreases. The main purpose of this study is to clarify the fundamental machinability of anisotropic materials cut with a fine wire tool. In this report, we describe the machinability of various woods that are naturally anisotropic materials using a fine wire cutting tool that has electrodeposited diamond grains on its surface. In addition, this report discusses the performance of a trial manufactured hand tool employing the same wire cutting tool. The main conclusions obtained in this study are as follows. Acceptable machining of anisotropic woods is possible using a fine wire cutting tool, and the kerf width produced with this wire tool is narrower than that produced with a fret-saw blade. Additionally, the wood species and the cutting direction with respect to the wood grain have a significant influence on the machinability of various woods. Moreover, a relatively smooth cross section is provided when wood is cut by the hand tool using the fine wire tool.

Abstract: This research characterizes flow of micromist for machining purpose. Liquid lubricant with contact angle less than 5° is chosen for best wetting on workpiece and tool materials. A high nozzle air speed of 100 m/s produces micromist with 20° spherical cone angle containing droplets of 4 μm average diameter, but smaller droplets might raise an environmental concern. Preliminary comparative tests show a significant reduction of tool wear when machining 4140 steel in minimum quantity lubrication.

Abstract: In the present paper, the experimental investigations on drilling characteristics of cenosphere reinforced epoxy composites with cemented carbide drill have been presented. The drilling aspects such as thrust and hole surface roughness have been performed as function of four process parameters, namely, spindle speed, feed rate, drill diameter and % weight of the filler. Composite specimens were prepared with 20%, 40% and 60% by weight of cenosphere filler in epoxy resin as the matrix. The full factorial design (FFD) has been employed for conducting drilling experiments and the proposed drilling characteristics were analysed using response surface methodology (RSM) based quadratic models. The response surface analysis reveals that the addition of cenosphere as filler in epoxy resin appreciably decreases with the thrust and hole surface roughness for the developed composites.