Anayet Ullah Patwari

Dynamic Modal Analysis of Vertical Machining Centre Components

The paper presents a systematic procedure and details of the use of experimental and analytical modal analysis technique for structural dynamic evaluation processes of a vertical machining centre. The main results deal with assessment of the mode shape of the different components of the vertical machining centre. The simplified experimental modal analysis of different components of milling machine was carried out. This model of the different machine tools structure is made by design software and analyzed by finite element simulation using ABAQUS software to extract the different theoretical mode shape of the components. The model is evaluated and corrected with experimental results by modal testing of the machine components in which the natural frequencies and the shape of vibration modes are analyzed. The analysis resulted in determination of the direction of the maximal compliance of a particular machine component.

Enhancement of Machinability of Inconel 718 in End Milling through Online Induction Heating of Workpiece

Abstract. This paper presents the outcome of a study on heat assisted end milling of Inconel 718 using inducting heating technique conducted to enhance the machinability of the material. The heating temperature maintained below the phase transformation temperature was aimed at softening the top removable material layers. The experimental results of both conventional and heat assisted machining were compared. The machinability of Inconel 718 under these conditions was evaluated in terms of tool life, tool wear morphology and chatter. The advantages of Induction heating is demonstrated by an longer tool life and lower chatter. The study showed that preheated machining facilitates up to 80% increase of tool life over conventional machining conducted using TiAlN coated carbide inserts.

Surface Roughness Prediction in High Speed Flat End Milling of Ti-6Al- 4V and Optimization by Desirability Function of RSM

High Speed Machining is applicable for producing parts that require little or no grinding / polishing operations within the required machining tolerances. For achieving required level of quality, selection of cutting tools and parameters in high speed machining is very important. In this study, small diameter flat end milling tool was used to achieve high rpm to facilitate the application of low values of feed and depth of cut to achieve better surface roughness. Machining was performed on a Vertical Machining Centre (VMC) with a high speed milling attachment (HES 510), using cutting speed, depth of cut, and feed as machining variables. Statistical prediction model of average surface roughness was developed using three-level full factorial design of experiments. It was observed that depth of cut is the most dominating factor followed by cutting speed and feed. The developed model was used for optimization by desirability function approach to obtain minimum Ra. Maximum desirability of 95.63% was obtained.

Prediction of Tool Life and Experimental Investigation during Hot Milling of AISI H13 Tool Steel

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 work-piece 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.

Prediction and Investigation of Surface Response in High Speed End Milling of Ti-6Al-4V and Optimization by Genetic Algorithm

In this study, statistical models were developed using the capabilities of Response Surface Methodology (RSM) to predict the surface roughness in high-speed flat end milling of Ti-6Al-4V under dry cutting conditions. Machining was performed on a five-axis NC milling machine with a high speed attachment, using spindle speed, feed rate, and depth of cut as 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 surface roughness prediction. A very good performance of the RSM model, in terms of agreement with experimental data, was achieved. It is observed that cutting speed has the most significant influence on surface roughness followed by feed and depth of cut. The model can be used for the analysis and prediction of the complex relationship between cutting conditions and the surface roughness in flat end milling of Ti-6Al-4V materials. The developed quadratic prediction model on surface roughness was coupled with the genetic algorithm to optimize the cutting parameters for the minimum surface roughness.

Development of a Passive Damping Tool Holder for the Improvement of Surace Roughness in Turning Operation of Stainless Steel

One special type of passive damping setup has been used to investigate the surface responses with the variation of different process parameters. In this study, a special design capsule type tool holder has been used to investigate the process parameters effect in machining of stainless steel during turning operations under different cutting condition such as-RPM, feed, depth of cut. Inside the capsule high viscous fluid is used as damping materials and its effects has been investigated accordingly. The effect of damping during turning process is investigated by studying generated surface profile for both with and without damping system. It has been observed that surface roughness is better in the newly designed passive damping tool holder compared to normal cutting conditions.

Prediction of Surface Roughness in High Speed Machining of Inconel 718

Surface finish and dimensional accuracy is one of the most important requirements in machining process. Inconel 718 has been widely used in the aerospace industries. High speed machining (HSM) is capable of producing parts that require little or no grinding/lapping operations within the required machining tolerances. In this study small diameter tools are used to achieve high rpm to facilitate the application of low values of feed and depths of cut to investigate better surface finish in high speed machining of Inconel 718. This paper describes mathematically the effect of cutting parameters on Surface roughness in high speed end milling of Inconel 718. The mathematical model for the surface roughness has been developed in terms of cutting speed, feed rate, and axial depth of cut using design of experiments and the response surface methodology (RSM). Central composite design was employed in developing the surface roughness models in relation to primary cutting parameters. Machining were performed using CNC Vertical Machining Center (VMC) with a HES510 high speed machining attachment in which using a 4mm solid carbide fluted flat end mill tool. Wyko NT1100 optical profiler was used to measure the definite machined surface for obtaining the surface roughness data. The predicted results are in good agreement with the experimental one and hence the model can be efficiently used to predict the surface roughness value with in the specified cutting conditions limit.

Statistical Approach for the Development of Tangential Cutting Force Model in End Milling of Ti6Al4V

Dynamic change in cutting force is one of the major causes of chatter formation in metal cutting which affect machining accuracy. Thus, accurate modeling of cutting force is necessary for the prediction of machining performance and determination of the mechanisms and machining parameters that affect the stability of machining operations. The present paper discusses the development of a mathematical model for predicting the tangential cutting force produced in endmilling operation of Ti6Al4V. The mathematical model for cutting force prediction has been developed in terms of the input cutting parameters cutting speed, feed rate, and axial depth of cut using response surface methodology (RSM). Effects of all the individual cutting parameters on cutting force as well as their interactions are investigated in this study. Central composite design was employed in developing the cutting force model in relation to the primary cutting parameters. The experimental results indicate that the proposed mathematical models suggested could adequately describe the performance indicators within the limits of the factors that are being investigated.

Chip serration frequency-the primary cause of chatter during end milling operation

Chatter is an unwanted but sometimes unavoidable phenomenon in machining. The term defines the self-excited violent relative dynamic motion between the cutting tool and work-piece. Chatter is undesirable due to its adverse effects on the product quality, operation cost, machining accuracy, tool life, machine-tool bearings, and machine-tool life. It is also responsible for reducing output. This paper includes the findings of an experimental study on instabilities of the chip formation process during end milling of Ti6Al4V alloy at different cutting conditions with two different two holders and its influencing factors on chatter formation. The instabilities of chip formation process are expressed as primary or secondary serrated frequency. The chip formed at different cutting conditions is analyzed and its frequency was calculated. It is observed that the primary serrated frequency is more prominent in end milling of Ti6Al4V alloy and its chip serration frequency has significant interaction effect with the with the prominent natural mode frequency of the system components. The vibration signals in frequency domain (FFT) have been analyzed to identify the chatter frequencies which have been compared with the chip serration frequencies in different cutting conditions for two different tool holders. It has been fairly concluded from the experimental findings that chatter is the outcome of resonance, in between the frequency of primary or secondary serrated frequency with the „prominent natural frequency‟ modes of the system components.

Investigation of surface parameters during hot air streaming turning process of mild steel

Different types of coolant are widely used in different metal cutting processes to improve the machining responses. But the suitability of using the correct cutting fluid is very important considering the concept of green environment. In this study, hot air is used as an alternative approach for hot machining process and coolant. Hot air is considered to initially heat the work-piece for easy machining operation. In this study, two different velocities of hot air has been applied during the machining of mild steel in turning process and its effect is investigated in terms of surface roughness. With the variation of different process parameters, it has also been observed that surface roughness at different cutting conditions using hot air is improved significantly. A clear comparison has been made to investigate the responses of surface roughness at different cutting conditions in between the hot air and normal machining processes. This procedure may be used as an alternative approach in the dry cutting re...