Papers by Keyword: High Speed End Milling

Abstract: This paper is related to the air jet assisted machining method for a titanium alloy, Ti-6Al-4V ELI. The air jet assisted machining method is a new machining method, in which jet of the compressed air is applied to a tool tip together with flood coolant for reducing tool wear and also for extending tool life. In this experimental study, the new method was used in high-speed end milling for confirming the effect on tool life extension. Also, the optimal position of the jet nozzle was found. It was spotted that the new method is highly effective in reducing tool wear even at a high cutting speed. It is particularly noticeable that flank wear near the corner land, which is often severely damaged, was considerably reduced by the method. It turned out that the cutting forces and the degree of surface roughness observed through this method were almost the same as those through an ordinary method with flood coolant alone.

Abstract: The aim of the present study is to investigate the influence of cutter engagement on cutting forces in end milling process of AISI H13 (48 HRc). The experiments were carried out on CNC vertical machining center. The machining conditions are as follows: V_c = 150, 200 and 250 m/min, f_z = 0.05, 0.1 and 0.15 mm/tooth; a = 0.1, 0.15 and 0.2 mm for every cutting process. Central Composite Design with 20 runs was employed. Data analysis showed that cutter engagement influence the cutting force for the end milling process of hard material H13 in the same pattern to the similar experiment of different material. The present study of cutter engagement will be useful in tool path creation which is important for mold and die machining. The cutter engagement study related to cutting force in high speed end milling of AISI H13 has not yet been established. This study will help the NC programmers in choosing the suitable tool path that will give stable, productive, and more efficient milling process

Abstract: Tool nose radius is an important geometrical parameter in the design of the tool. Due to its direct contact with the workpiece surface it have significant effect not only on the resulting surface quality but also on the tool life. Use of an end mill without nose radius can easily blend during machining due to a lot of stresses acting on the edge of the tool while the large nose radius end mill can increase the strength and rigidity of the tool but can also contribute in increasing the friction between the tool and the workpiece. Therefore careful selection of tool nose radius is important and especially important for Polycrystalline Diamond, PCD insert as this tool material has recently shown great success in terms of tool life, surface roughness and productivity over coated and uncoated carbide tools in high speed end milling of titanium alloy Ti-6Al-4V and with the use of correct tool geometry it can be further helpful in increasing tool life and surface quality. This study therefore investigates the effect of various nose radii’s (R0.1,0.2,0.4,0.8,1.2,1.6,2.4,3.2) and complete round insert end mill on cutting forces and heat distribution between tool and the chip for PCD insert and compare the results with multi-layer (Al₂O₃+TiAlN+TiN) coated carbide tool at high speed cutting conditions using 3-D finite element numerical simulations. Results have shown that both tools due to their difference in thermal and mechanical properties have different behavior under the conditions studied especially when the complete round insert tool is used. The use of small nose radius tool when nose radius r_n is less than the axial depth of cut a_p, the forces and the temperature remains quite low and slightly increases with the increase of radius until r_n is smaller than a_p but when r_n gets larger than a_p and only some portion of nose radius is involved in cutting, then forces and temperature increases considerably. While when complete round insert end mill is used the forces and temperature significantly drops (more than 50% than the largest nose radius tool studied) at the same a_p for PCD insert but for multi-layer coated carbide tool it drops only slightly (20% than the largest nose radius tool studied). The reason for this difference lies in the fact that PCD tool has lower toughness, high hot strength and is more brittle than carbide tools and therefore maximum advantage can be taken only when small nose radius is used or when complete round insert tool is used as complete round insert have uniform stress distribution and also provides more stability for PCD tool material while large nose radius tool increases friction and also has more heat penetration in the tool thus resulting in higher cutting forces and temperature thus ultimately contributing in high wear of tool. While on the other hand carbide tools are only beneficial when smaller nose radius tool is used rather than round shape because of lower hot strength of the material.

Abstract: An experimental study of high speed machining of soda lime glass using directional compressed air blowing for removal of the ductile chips from the machined surface, is presented. High speed end milling of soda lime glass is performed on a vertical CNC milling machine to observe the effects of machining parameters i.e. spindle speed, depth of cut and feed rate on the resultant surface roughness. The design of the experiments was performed following the Central Composite Design (CCD) of the Response Surface methodology (RSM) using the Design Expert Software. Optimization of machining parameters was conducted using desirability function of the Design Expert software based on minimum surface roughness criterion. Finally, experimental verification tests were conducted to validate the predicted optimized value.

Abstract: Glass materials play a vital role in advancement of science and technology. They have found wide spread application in the industry, in laboratory equipment and in micro-gas turbines. Due to their low fracture toughness they are very difficult to machine, moreover there are the chip depositions on the machined surface which affects surface finish under ductile mode cutting conditions. In this research, high speed end milling of soda lime glass is performed on CNC vertical milling machine to investigate the effects of machining parameters i.e. spindle speed, depth of cut, and feed rate on machined surface roughness. Design of experiments was performed following Central Composite Design (CCD) of Response Surface Methodology (RSM). Design Expert Software was used for generating the empirical mathematical model for average surface roughness. The model’s validity was tested to 95% confidence level by Analysis of Variance (ANOVA). Subsequent experimental results showed that the developed mathematical model could successfully describe the performance indicators, i.e. surface roughness, within the controlled limits of the factors that were considered.

Abstract: This paper presents the thorough experimental analysis on high speed end milling of single crystal silicon using diamond coated tools. Experiments were conducted on CNC milling machine. The design of the experiments was based on the central composite design (CCD) technique of Design Expert software. Response Surface Methodology (RSM) was used to develop mathematical imperial model to establish a correlation between machining parameters (cutting speed, feed and depth of cut) and machined surface roughness in high speed end milling of single crystal silicon using 2mm diameter diamond coated tools. The optimum machining parameters were determined using the optimization tool of Design Expert software based on the desirability function. Finally, confirmation tests were performed to validate the developed model.

Abstract: The majority of semiconductor devices are made up of silicon wafers. Manufacturing of high-quality silicon wafers includes numerous machining processes, including end milling. In order to end mill silicon to a nano-meteric surface finish, it is crucial to determine the effect of machining parameters, which influence the machining transition from brittle to ductile mode. Thus, this paper presents a novel experimental technique to study the effects of machining parameters in high speed end milling of silicon. The application of compressed air, in order to blow away the chips formed, is also investigated. The machining parameters’ ranges which facilitate the transition from brittle to ductile mode cutting as well as enable the attainment of high quality surface finish and integrity are identified. Mathematical model of the response parameter, the average surface roughness (R_a) 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 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.

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: 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: 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.