AMMC

This paper presents an approach to establish models for tool life in end milling of titanium alloy Ti-6Al-4V using uncoated carbide inserts under dry conditions. Small central composite design (CCD) was employed in developing the tool life model in relation to primary cutting parameters such as cutting speed, axial depth of cut and feed. Flank wear has been considered as the criteria for tool failure and the wear was measured under a Hisomet II Toolmaker's microscope. Further testing was stopped and an insert rejected when an average flank wear greater than 0.30 mm was achieved. Design-expert version 6.0.8 software was applied to establish the first-order and the second-order model and develop the contours. The adequacy of the predictive model was verified using analysis of variance (ANOVA) at 95% confidence level.

In this paper, the cutting of Tungsten Carbide ceramic using electro-discharge machining (EDM) with a graphite electrode by using Taguchi methodology has been reported. The Taguchi method is used to formulate the experimental layout, to analyse the effect of each parameter on the machining characteristics, and to predict the optimal choice for each EDM parameter such as peak current, voltage, pulse duration and interval time. It is found that these parameters have a significant influence on machining characteristic such as metal removal rate (MRR), electrode wear rate (EWR) and surface roughness (SR). The analysis of the Taguchi method reveals that, in general the peak current significantly affects the EWR and SR, while, the pulse duration mainly affects the MRR. Experimental results are provided to verify this approach.

Problem statement: Titanium alloys have been used widely in the aerospace, chemical and petroleum industry because of their high specific strength, fracture resistance and superior resistance to corrosion. Titanium alloys have a very high strength-to-weight ratio making them very suitable for aircraft engines and airframe manufacture. Approach: The use of titanium alloys as engine component materials is due to their ability to maintain their high strength at high operating temperatures of the engine. Titanium alloys exhibit exceptional resistance to corrosion, which provides savings on protective coating like paints that will otherwise be used in the case of steel. However, titanium alloys are difficult to machine due to their high temperature strength, low modulus of elasticity, low thermal conductivity and high chemical reactivity. Results: This study presented the investigation of tool life improvement in end-milling of Titanium Alloy Ti-6Al-4V through workpiece preheating. End milling tests were conducted on Vertical Machining Centre with full immersion cutting. Titanium alloy Ti-6Al-4V bar was used as the workpiece. Machining was performed with a 20 mm diameter end-mill tool holder fitted with one uncoated WC-Co carbide inserts. All of the experiments were run under room temperature and preheating condition at 315, 450 and 650°C. Induction heating was utilized during end milling with preheating. Flank wear has been considered as the criterion for tool failure and the wear was measured using a Hisomet II Toolmaker's microscope. Tests were conducted until an insert rejected when an average flank wear greater than 0.30 mm was recorded. Cutting force and torque measurements were conducted using the Kistler Rotating Cutting Force Dynamometer. Vibration during cutting was captured using an online vibration monitoring system. Scanning Electron Microscope (SEM) was also used to investigate the wear morphology. Conclusion/Recommendation: The results lead to conclusions that workpiece preheating significantly increases the tool life of uncoated WC-Co carbide inserts in end-milling of Titanium Alloy Ti-6Al-4V. An increase in tool life by 325 % was achieved while employing preheating at 650°C compared to the experiment at room temperature.

This paper presents a study on the development of an effective method to predict surface roughness for high speed end milling of AISI H13 tool steel using PCBN inserts. The response surface methodology (RSM) has been utilized for the postulation of a second order quadratic model in terms of cutting speed, axial depth of cut and feed. Sufficient numbers of experiments were run based on the Box-Wilson central composite design (CCD) concept of RSM in order to generate roughness data. The ANOVA technique has been used to verify the adequacy of the model at 95% confidence interval. From the model it was found that feed plays the most dominating role on surface finish followed by the cutting speed. However, axial depth of cut does not have significant effect on roughness value. The roughness tends to decrease with decreasing feed and increasing cutting speed.

Problem statement: The benefits of easier manufacture of hardened steel components can be substantial in terms of reduced machining costs and lead times compared to the traditional route involving machining of the annealed state followed by heat treatment, grinding/EDM and manual finishing. But machinability of hard material through conventional machining is hindered due to excessive wear of the cutting tools and differently in achieving desired quality of the machined surface. In end milling the cutting tool is not in constant operation and so undergoes a heat cycle during the intermittent cutting. This alternate heating and cooling of the inserts lead to the thermal cracks and subsequently failure of the tool. Approach: This study was conducted to investigate the effect of preheating through inductive heating mechanism in end milling (vertical milling center) of AISI D2 hardened steel (56-62 HRC) by using coated carbide tool inserts. Apart from preheating, two other machining parameters such as cutting speed and feed were varied while the depth of cut was kept constant. Results: Tool wear phenomenon and machined surface finish were found to be significantly affected by preheating temperature and other two variables. Preheating temperature of 335°C coupled with cutting speed of 40 m min −1 , depth of cut of 1.0 mm and feed of 0.02 mm/tooth resulted in a noticeable reduction in tool wear rate leading to a maximum tool life 188.55 min. In addition, cutting speed of 56.57 m min −1 together with feed of 0.044 mm/tooth and depth of cut 1.0 mm at which maximum VMR (9500 mm 3 ) was secured provides a better surface finish with minimum surface roughness 0.25 µm leaving a possibility of skipping the grinding and polishing operations for certain applications. Conclusion/Recommendation: Through the end milling of preheated AISI D2 hardened steel by using TiAlN coated carbide cutting tool it can be concluded that an overall enhanced machinability is achievable by preventing catastrophic damage of the cutting tool at higher levels of feed and cutting speed.

This paper presents the results of experimental investigations conducted on a vertical machining centre (VMC) using spindle speed, feed rate, and depth of cut as machining variables to ascertain the effectiveness of TiAlN insert in end milling of hardened steel AISI H13, under workpiece preheated conditions and hence a statistical model was developed using the capabilities of Response Surface Methodology (RSM) to predict the tool life. Sufficient number of experiments was conducted based on the small central composite design (CCD) concept of RSM to generate tool life data for the selected machining variables. The adequacy of the model was tested at 95% confidence interval. Meanwhile, a time trend was observed in residual values between model predictions and experimental data, reflecting little deviations in tool life prediction. A very good performance of the RSM model, in terms of agreement with experimental data, was achieved. The model can be used for the analysis and prediction of the complex relationship between cutting conditions and the tool life in flat end milling of hardened materials.

This paper presents the investigation of tool life improvement in end-milling of Titanium Alloy Ti-6Al-4V through workpiece preheating. End milling tests were conducted on Vertical Machining Centre with full immersion cutting. Induction heating was utilized during end milling for preheating. The titanium alloy Ti-6Al-4V bar was used as the workpiece. Machining was performed with a 20 mm diameter end-mill tool holder fitted with one PCD inserts. All of the experiments were run under room temperature and preheating condition at 315, 450, and 650ºC. Flank wear has been considered as the criterion for tool failure and the wear was measured using a Hisomet II Toolmaker's microscope. Tests were conducted until an insert was rejected when an average flank wear greater than 0.30 mm was recorded. Cutting force and torque measurements were conducted using the Kistler Rotating Cutting Force Dynamometer. Vibration during cutting was captured using an online vibration monitoring system. Scanning electron microscope (SEM) was also used to investigate the wear morphology. The results led to conclusions that workpiece preheating significantly increases the tool life of PCD inserts in end-milling of Titanium Alloy Ti-6Al-4V.

This paper presents the results of experimental investigations conducted on a vertical machining centre (VMC) to ascertain the effectiveness of brazed circular polycrystalline cubic boron nitride (PCBN) inserts in end milling of hardened steel AISI D2 (60–62 HRC), under room temperature and workpiece preheated conditions. Comparison was made in terms of intensity of chatter, chip formation instability, tool wear and metal removal capacity of the tool and surface roughness of the machine parts. It has been found that chips formed are composed of primary and secondary serrated teeth and their formative frequencies have definite relationship with the chatter frequencies. Though initial average flank wear of the tool during preheated machining is found to be slightly higher compared to that of room temperature machining, the extrapolated tool life appears to be higher in the case of preheating. The main mechanisms of tool failure are found to be superficial plastic deformation, diffusion and notching. It has been observed that feed per tooth, cutting speed, preheating and amplitude of chatter have direct bearing on the surface roughness. It has been observed that preheated machining of the material leads to surface roughness values well below 0.4 μm, such that the operations of grinding as well as polishing can be avoided at the higher cutting speeds.

A method of solid-state recycling aluminum alloy using hot press forging process was studied as well as the possibility of the recycled chip to be used as secondary resources. This paper presents the results of recycled AA6061 aluminium alloy chip using different operating temperature for hot press forging process. Mechanical properties and microstructure of the recycled specimens and as-received (reference) specimen were investigated. The recycled specimens exhibit a good potential in the strength properties. The result for yield strength (YS) and ultimate tensile strength (UTS) at the minimum temperature 430˚C is 25.8 MPa and 27.13 MPa. For the maximum operating temperature 520˚C YS and UTS are 107.0MPa and 117.53 MPa. Analysis for different operating temperatures shows that the higher temperatures giving better result on mechanical properties and finer microstructure. The strength of recycled specimen increases due to the grain refinement strengthening whereas particle dispersion strengthening has minor effects. In this study, the recycled AA6061 chip shows the good potential in strengthening as the comparison of using only 17.5% of suggested pressure (70.0/400.0) MPa, the UTS exhibit 35.8% (117.58/327.69) MPa. This shows a remarkable potential of direct recycling by using hot press forging process.

In this paper an attempt has been made to investigate the performance of an electrode made through powder metallurgy (PM) of copper tungsten during electrical discharge machining (EDM). Experimental results are presented on electrical discharge machining of AISI D2 hardened steel in kerosene with a copper tungsten (Cu35% -W65%) tool electrode made through PM method with a constant duty factor of 80%. In terms of high performance EDM process, higher peak current (>20A) and pulse duration (>400µs) with a high machining efficiency were applied. Experimental results have shown that machining at a peak current of 40A and pulse duration of 400µs yields the highest material removal rate (MRR) whereas machining at a peak current of 20A and pulse duration of 400µs yields the lowest tool wear rate (TWR). The surface characteristics of workpiece machined surface become more severe when shorter pulse duration be used at the constant duty factor. The optimum machining performance can be performed by the combination of pulse duration and peak current at 400µs and 40A respectively since the effect of TWR is so small at the varied parameters even at the highest MRR.

Surface topography plays an important part in understanding the nature of machined surfaces. This study is focused on surface topography of AISI D2 hardened steel (58-62 HRC) under dry milling process. Roughness, surface morphology and defects analysis were investigated. This study achieved R a in range of 0.18 to 0.30 µm which is acceptable in mould and die requirement. Moreover, surface roughness decreased as cutting speed increased. From the optical microscope observation shows that the milled surface is anisotropic in nature. The lay pattern is produced by the combination of tool movement during milling operation (cutting and feed speed directions). Meanwhile, the AFM images indicated that the milled surfaces are groovy constructed by low-amplitude topography (between peak and valley of the machined surface waves). Surface defects were found in this study were debris, groove and cavity, all of which affected the surface roughness value.

In this paper an attempt has been made to investigate the performance of an electrode made through powder metallurgy (PM) of copper tungsten during electrical discharge machining (EDM). Experimental results are presented on electrical discharge machining of AISI D2 hardened steel in kerosene with a copper tungsten (Cu35% -W65%) tool electrode made through PM method with a constant duty factor of 80%. In term of high performance EDM process, higher peak current (>20A) and pulse duration (>400µs) with a high machining efficiency were used. Experimental results have shown that machining at a peak current of 40A and pulse duration of 400µs yields the highest material removal rate (MRR) whereas machining at a peak current of 20A and pulse duration of 400µs yields the lowest tool wear rate (TWR). The lowest surface roughness appears at the lowest material removal rate which is at a peak current of 20A and pulse duration of 600µs. The optimum machining performance can be performed by the combination of pulse duration and peak current at 600µs and 40A respectively.

Hard milling of hardened steel has wide application in mould and die industries. However, milling induced surface finish has received little attention. An experimental investigation is conducted to comprehensively characterize the surface roughness of AISI D2 hardened steel (58-62 HRC) in end milling operation using TiAlN/AlCrN multilayer coated carbide. Surface roughness (R a ) was examined at different cutting speed (v) and radial depth of cut (d r ) while the measurement was taken in feed speed, V f and cutting speed, V c directions. The experimental results show that the milled surface is anisotropic in nature. Surface roughness values in feed speed direction do not appear to correspond to any definite pattern in relation to cutting speed, while it increases with radial depth-of-cut within the range 0.13-0.24 µm. In cutting speed direction, surface roughness value decreases in the high speed range, while it increases in the high radial depth of cut. Radial depth of cut is the most influencing parameter in surface roughness followed by cutting speed.

Majority of the published research works on modeling of tool life in machining of hardened steels are based mainly on the turning process, whilst the hard milling process has rarely been adopted. This work is aimed to determine the optimum cutting conditions leading to maximum tool life in end miling of AISI D2 hardened steel using PVD TiAlN coated carbide tool inserts using first and second order models. Analysis of variance (ANOVA) has been conducted for both the models to check the adequacy levels. It has been found that the models are valid for predicting the tool life in machining under specified condition with an average of error less than 10%.

In this paper, the tool life and tool wear performance of PCBN tool in end milling of AISI D2 hardened steel under room and preheated machining conditions is presented. The tool life and tool wear patterns were examined through tool maker microscope and scanning electron microscope. The results show that the dominant modes of tool wear observed were flank wear, chipping, and notch wear. The main wear mechanisms were abrasion, adhesion, and diffusion promoted by high stress and cutting temperature. It was also observed that longer tool life and higher volume metal removed could be achieved when employing higher preheating temperature.