Abstract: Manufacturing companies define the qualities of thermal removing process based on the dimension and physical appearance of the cutting material surface. Therefore, the roughness of the surface area of the cutting material and the rate of the material being removed during the manual plasma arc cutting process was importantly considered. Plasma arc cutter Selco Genesis 90 was used to cut the specimens made from Standard AISI 1017 Steel manually based on the selected parameters setting. Two different thicknesses of specimens with 3mm and 6mm were used. The material removal rate (MRR) was measured by determining the weight of the specimens before and after the cutting process. The surface roughness (SR) analysis was conducted to determine the average roughness (Ra) value. Taguchi method was utilized as an experimental layout to obtain MRR and Ra values. The results reveal that for the case of manual plasma arc cutting machining, the SR values are inversely proportional to the MRR values. The quality of the surface roughness depends on the dross peak that occurred during the cutting process.
Abstract: In this investigation, electrical discharge machining (EDM) was done with Cu-TaC powder metallurgy (PM) electrode and urea solution dielectric fluid. The main objective is to improve the surface wear property of Ti-6Al-4V alloy through the formation of hard ceramic compounds on its surface during EDM. The experiments were conducted with peak current, Ip (3.5, 5.5 A) and pulse duration, ton (3.3, 5.3 µsec) as the machining variables. The outputs investigated are surface characteristics and micro-hardness. The formation of nitrides, carbides and oxides of tantalum and titanium on the EDMed surface was confirmed. The highest micro-hardness of 902.2 Hv was obtained with Ip of 5.5 A and ton of 3.3 µsec.
Abstract: Machining of silicon is an expensive affair because its inherent brittleness leads to subsurface crack generation. Research endeavours have therefore focused on ductile mode machining of silicon to obtain crack free machined surfaces with roughness as low as 0.22 µm or even below, hence eliminating the need for subsequent polishing/grinding operations. However, most of these research works utilized expensive ultraprecision machines and tools. This research aimed at determining the viability of using conventional milling machines with diamond coated tools, high speed attachments, and air blowing mechanisms in order to achieve ductile regime machining of silicon. Spindle speed, depth of cut, and feed rate, ranges: 60,000 to 80,000 rpm, 10 to 20 µm, and 5 to 15 mm/min respectively, were considered as the independent machining parameters. Compressed air at 0.35 MPa was also provided to prevent chip deposition on the finished surfaces. The resultant surfaces were analysed using Optical and Scanning Electron Microscopes. Then, the influence of each machining parameter on surface roughness was investigated. From the analyses it was concluded that all three machining parameters and air blowing had significant influence on the surface topography and integrity of silicon.
Abstract: Machining of metals is generally accompanied by a violent relative vibration between work and tool, known as chatter. Chatter is undesirable due to its adverse effects on product quality, operation cost, machining accuracy, tool life, and productivity. This paper presents an innovative approach to chatter control during end milling of titanium alloy Ti-6Al-4V using ferrite permanent magnets to reduce the unwanted vibrations. A special fixture was fabricated and mounted on a Vertical Machining Center‘s spindle for holding the permanent magnet bars, used in suppressing the vibration amplitudes. DASY Lab 5.6 was used for signal analysis and processing to compare the intensity of chatter under normal and magnet application conditions. Fast Fourier Transform (FFT) was subsequently used to transform the vibration data to a function of frequency domain. The experiments focused on monitoring the vibration amplitudes and analysis of chip formation process during metal cutting. It was observed that the magnetic fields contributed to reduction of chatter amplitudes. It was apparent that a reduction of chatter amplitude would result in improved surface finish of the work-piece and lead to uniform chip formation.
Abstract: Review of past research indicated that ductile mode machining of silicon can produce surface roughness values as low as 0.22 µm, which is about half of 0.40 µm, the usual standard roughness value to avoid fine grinding and rough polishing operations. The current research investigated and compared the surface roughness and integrity attained in high speed end milling of silicon (using diamond coated tools) under ductile mode machining conditions. Two different types of end milling machines were utilized, CNC and conventional milling machines. Additionally, the effect of compressed air on the resultant surface roughness was investigated. The air blowing fixture, designed for mounting the compressed air hose, consisted of fixed and movable jaws, air blower clamp, fasteners, and the air gun. Air blowing was used to prevent silicon chips from settling on the machined surface, since it was observed to be an acute problem in high speed ductile mode machining of silicon. The three machining parameters: spindle speed, depth of cut, and feed rate were varied within the ranges 60,000 to 80,000 rpm, 10 to 20 µm, and 5 to 15 mm/min respectively. The resultant machined surfaces were analysed using Wyko NT 1100 and SurfTest SV-500 profilometers in order to measure the attaine surface roughnesses and surface profile. The machined surfaces had almost no deposition and was of excellent finish.
Abstract: Soda-Lime glass is a very hard and brittle material which is commonly used as window panels and many other common applications. Due to its low fracture toughness it is very difficult to machine and obtain good surface finish under nornal cutting conditions. Hence, machining has to be done in ways to avoid brittle fracture on the finished machined surface. Such machining is only possible under ductile mode machining conditions when the removal of material is performed in the plastic state. However, ductile mode machining requires that during machining the temperature generated in the cutting zone in the working temperature range of glass to avoid crack formation during machining. This makes all types of machining of glass an extremely challenging affair, given the current state and mode of mechanical machining. This research paper elucidates the results of an experimental study for determination of critical depth of cut as a function of cutting parameters in high speed end milling of soda-lime glass. The critical depth is defined as the depth of cut at which crack formation the material is initiated for a given high speed attachment. In determining the critical depth as well as the ductile brittle transition depth, machining was performed on a tapered surface. Vibration signals from an accelerometer in time domain (amplitude vs. time display) and the surface characteristics were used in identifying the critical depth of cut. The new method has been found to be useful in online determination of the critical depth, as well as the brittle-ductile transition depth, for generating crack-free surfaces with good surface finish in high speed end milling of soda lime glass.
Abstract: This research demonstrated the use of conventional milling machines with diamond coated tools, high speed attachments, and air blowing mechanisms for ductile mode machining of silicon and subsequently modeling and optimizing the resultant surface roughness. Spindle speed, depth of cut, and feed rate, ranges: 60,000 to 80,000 rpm, 10 to 20 µm, and 5 to 15 mm/min respectively, were considered as the independent machining parameters for the modeling process. Compressed air at 0.35 MPa was also provided to prevent chip deposition on the finished surfaces. The resultant surfaces were analysed using Optical and Scanning Electron (SEM) Microscopes as well as Wyko NT 1100 and SurfTest SV-500 profilometers. The response, surface roughness, was then modeled using a small Central Composite Design (CCD) in Response Surface Methodology (RSM). The quadratic relation was found to be most suitable following Fit and Summary and ANOVA analyses. The relation was then optimized using Desirability Function (DF) in Design of Expert (DOE) software. The optimum attainable surface roughness, which was validated using experimental runs, was found to be 0.11 µm which may be considered quite satisfactory.
Abstract: One of the most challenging issues in machining process is understanding the chatter phenomenon. Chatter mechanics is still not fully understood. It is inconsistent in character, making it difficult to analyze and predict. This research work investigates the influence of permanent magnets on chatter suppression in end milling of Titanium alloy (Ti-6Al-4V) using uncoated WC-Co insert. The experiments were designed based on the Response Surface Methodology (RSM) approach using DESIGN EXPERT (DOE) software. The experiments were performed under two different conditions: under normal condition and under the application of magnetic fields from two permanent magnets located in opposite direction. Ti-6Al-4V was used as the work material. The resultant average surface roughness was found to be reduced by a maximum of 50% due to magnet application. Scanning Electron Microscope (SEM) was used to analyze the chip morphology. The microphotographs showed the evidence of more stable chip formation under the influence of magnetic fields.
Abstract: One of the most hard and brittle material is glass. Due to the properties of low fracture toughness it is very difficult to being machined having good surface quality. Hence it is required to be machined in such a way that brittle fracture does not appear in the new machined surface, which is only possible in ductile mode machining or the removal of material in the plastic state. Above all machining of glass is the most challenging in current state of mechanical machining. The experimental results show that the developed mathematical model can effectively describe the performance indicators within the controlled limits of the factors that are being considered. This paper presents the mathematical model and optimization results of an experimental study of high speed end milling by the consideration of amplitude time display (Time Domain), FFT Diagram (Frequency Domain) and surface characteristics to find out the maximum critical depth for higher material removal which is crack free surface having good surface finishes. Mathematical model of the response parameter, the critical depth is subsequently developed using RSM in terms of the machining parameters. The model was determined, by Analysis of Variance (ANOVA), to have a confidence level of 95%. The optimization was carried out by the optimization features of Design Expert software.