End-milling Operation Research Articles

An experimental study of the response characteristics of end milling operations and their finite element simulation

The present study investigates the effect of milling parameters on cutting forces and performance characteristics in end mill operations using two different types of end milling tools. The end milling experiments were performed on AA7075-T6 grade aluminium alloy using a vertical milling machine fitted with a Kistler dynamometer to acquire the data of cutting forces during the milling operation. A matrix of process parameters was created by varying spindle rotational speed in the range of 500–1200 rpm while the feed rate was kept between 10 and 30 mm/min, keeping a maximum depth of cut of 4 mm. The data obtained from the experimental results were analysed and validated by simulation using the DEFORM-3D software facility. The experimental results reflect that with the increase in cutting speed, the cutting force first increases and then decreases, while an increase in feed rate enhances the cutting forces. The combination of high cutting speed with low feed rate was found to be suitable as the force required in this case exhibits a minimum to achieve both efficiency and machinability for a tool. Validated experimental results can be useful for finding new combinations of parameters in the defined parameter range for milling applications.

Analysis and optimization of machining parameters of AZ91 alloy nanocomposite with the Influences of nano ZrO2 through vacuum diecast process

The magnesium alloy composite is a vital material for automotive applications due to its features like high stiffness, superior damping resistance, high strength, and lightweight. Here, the motto of research is to establish the AZ91 alloy nanocomposite with the exposures of 0, 1, 3, and 5 volume percentages (vol%) of nano zirconium dioxide (ZrO2) particles (50nm) through fluid stir metallurgy route associated with 1x105 Pa vacuum die cast process. Exposures on structural morphology, hardness, and impact toughness of composite are analyzed and identified as the nano AZ91 alloy composite enclosed with 5vol% is homogenous particle dispersion, enhanced hardness (97.6HV), and optimum toughness of 21.2J/mm2. However, composite faces machining difficulties due to the hard abrasive particles with higher hardness, resulting in tool wear. This experiment predicts the optimum mill parameters during the end mill operation of magnesium alloy nanocomposite (AZ91/5vol%) by using a tungsten carbide coated end mill cutter to attain the maximum metal removal rate with low surface roughness and tool wear analyzed via the general linear model (GLM) ANOVA approach. The input conditions for end milling operation vary, like feed rate (0.1 -0.4mm/rev), depth of cut (0.05 -0.2mm), and spindle speed (250-1000rpm). During the ANOVA GLM approach, the L16 design experiment is fixed for further interaction analysis. The results predicted by the depth to cut and feed rate were dominant and played a major role in deciding the tool wear, surface roughness, and MRR.

Swift feedback and immediate error control using a lightweight simulation approach – A case study of the digital-twin-in-the-loop for machining thin-wall structures

The field of Digital Twins is rapidly growing, with an emerging trend of using virtual representations to directly control process-related errors in manufacturing operations. This paper introduces the Digital-Twin-in-the-Loop that uniquely integrates the Digital Twin (DT) into the direct feedback loop of a notoriously error-prone machining operation of low-rigidity structures. The proposed approach bypasses the need for post-process workpiece measurements by utilizing the twin to estimate 3D deformations caused by machining forces and correcting the toolpath automatically. For the first time, a fast and process-oriented simulation method, based on a mass-spring-lattice model for “on-the-fly” monitoring of workpiece deflections, as well as a comparative scaling method are presented as the backbone of the Digital-Twin. As a case study an end-milling operation is considered, focusing on the correction of the toolpath to improve the surface profile of low-stiffness components which are prone to dimensional errors. Experimental results show that the proposed method significantly improves the geometrical accuracy of the machined surface with a good repeatability, reducing errors by 78.96%. This establishes the Digital-Twin-in-the-Loop as a relevant tool for the implementation of time-efficient machining environments, while maintaining rigorous accuracy through in-process monitoring.

A HYBRID ENSEMBLE LEARNING MODEL FOR EVALUATING THE SURFACE ROUGHNESS OF AZ91 ALLOY DURING THE END MILLING OPERATION

In metal-cutting operations, the surface roughness of the end product plays a significant role. It not only affects the aesthetic appearance of the end product but also signifies the product’s performance in the long run. Products with a high surface finish have higher endurance limits with negligible local stresses. On the other hand, products with rough surfaces are subjected to high stresses when they are engaged in various mechanical operations with varying loads. Surface roughness depends on various machining factors such as feed rate, depth of cut, cutting speed, or spindle speed. Therefore, it is required to predict surface roughness for the given machining parameters to reduce the cost and increase the life of the end product. In this work, an attempt has been made to evaluate the surface roughness of AZ91 alloy during the end milling operation. In this regard, various state-of-the-art ensemble learning models have been adopted and compared with the proposed hybrid ensemble model. The proposed hybrid ensemble model is the integration of random forest, gradient boosting, and a deep multi-layered neural network. In order to evaluate the performance of the proposed model, comparative analyses have been made in terms of mean square error, mean average error, and [Formula: see text] score. The result shows that the proposed hybrid model gives minimum error for surface roughness.

Design and evaluation of an MRF damper for semi-active vibration control of the machining processes

Cutting forces and vibrations generated during machining significantly affects the cutting tool and the integrity of the workpiece surface. Therefore, it is necessary to control or reduce those vibrations. Among the different vibration control methods, semi-active and active vibration control approaches are more effective than traditional methods. Also, with recent advancements in smart fluids and materials, the Magnetorheological fluid has gained attention in semi-active vibration control. In the present study, the novel monotube MRF damper is designed, fabricated, and evaluated for use in an end-milling process. The MRF damper has higher radial dimensions to develop a large damping force and reduce system complexity. The performance of a developed MRF damper is analyzed using the Bouc-Wen model, whose parameters are tuned for the developed MRF damper and validated experimentally under the different excitation currents, frequencies, and amplitude. The experimental and simulated damping forces are well agreed with each other, having a range of 13%–17%. The damper provides a maximum damping force of 1700 N under the excitation current of 2 A, and a frequency of 1 Hz at the amplitude of 8 mm. Moreover, it was also observed that the excitation current has a higher influence on the damping force than the frequency and amplitude. Thus, the developed MRF is further used in end-milling to reduce the cutting forces generated during the material removal, which shows that vibration damping significantly reduces 40%–65% of the cutting forces generated during the normal end-milling operation.

Parametric Study and Optimization of End-Milling Operation of AISI 1522H Steel Using Definitive Screening Design and Multi-Criteria Decision-Making Approach.

End-milling operation of steel grade material is a challenging task as it is hard-to-cut material. Proper selection of cutting tools, cutting conditions, and cutting process parameters is important to improve productivity, surface quality, and tool life. Therefore, the present study investigated the end-milling operation of AISI 1522H steel grade under minimum-quantity lubrication (MQL) conditions using a novel blend of vegetable oils, namely canola and olive oil. Cutting process parameters considered were spindle speed (s), feed rate (f), depth of cut (d), width of cut (w), and cutting conditions (c), while responses were average surface roughness (Ra), cutting forces (Fc), tool wear (TW), and material removal rate (MRR). Experimental runs were designed based on the definitive screening design (DSD) method. Analysis of variance (ANOVA) results show that feed rate significantly affects all considered responses. Nonlinear prediction models were developed for each response variable, and their validity was also verified. Finally, multi-response optimization was performed using the combinative distance-based assessment (CODAS) method coupled with criteria importance through inter-criteria correlation (CRITIC). The optimized parameters found were: s = 1200 rpm, f = 320 mm/min, d = 0.6 mm, w = 8 mm, and c = 100 mL/h. Further, it was compared with other existing multi-response optimization methods and induced good results.

Influence of cutting parameters on end milling of magnesium alloy AZ31B

Magnesium alloys are having the characteristics like light weight, wear, and corrosion resistance. Mg alloys find usage in a wide range of applications such as engine block of automobile parts, laptop cases, aircraft fuselages and mobile outer cases. However, in dry machining, many challenges restrict its development during fitment. In this research work, conventional vertical milling machine was used to conduct end milling operation on Mg AZ31B alloy with coated carbide insert. End milling operations were performed by varying spindle speed, feed per tooth, and constant cutting depth. The chip morphology and tool chip interface temperature were investigated for various cutting conditions. Also, feed force (Fx), thrust force (Fy) and cutting force (Fz) was analyzed to understand the proper material deformation characteristics.

An abaqus-based 3D computer aided design, modelling and simulation of the end-milling operation of stainless steel 301

The need to improve the quality of products, to reduce the machining costs, and to maximize the profit rate calls for deployment of accurate optimisation model for predicting various parameters during milling operation in the manufacturing industries. Incorrect selection of cutting conditions often leads to most defects in milling operations such as inaccuracies in a feature's dimensions or surface roughness, thus compromises the quality of the work-piece being produced. To address the above mentioned issues, this research work employs a computer-aided based modelling and simulation approach to investigate the stress, strain, displacement and thermal distributions during the end milling operation of duplex stainless steel 301. The computer-aided design, modelling and simulation of the milling operation of the material was performed using the commercial software code ABAQUS. A dynamic coupled temperature-displacement computation was employed in the explicit module of the ABAQUS software. The cutting tool and the work piece was first modelled and their computer aided design (CAD) models were imported into the module that is meshed with structured 8-node thermally coupled brick, trilinear displacement and temperature (C3D8RT) mesh elements with reduced integration and hourglass control. The mechanical loading step was carried out from which the thermal step propagates. The result obtained indicate that the stress induced in the work piece was insufficient to cause effective shearing and material removal while the magnitude of the average heat flux was found to be sufficient. The maximum values of the cutting conditions obtained include stress (9.051 MPa), average heat flux (2.102×109w/m2), cutting speed (7700 m/min or 128.359 m/s), strain (3.12×10−13), resultant force (2.147×1010N) and nodal temperature (25°C). It is envisaged that the findings of this work will assist machinist in effective milling operation of stainless steel AISI 301.

Extended classification of surface errors shapes in peripheral end-milling operations

The prediction of form surface error represents the basis of many approaches, which aims at increasing the productivity and reducing the costs of a milling operation. In peripheral end-milling the form error caused by the tool/workpiece static deflection is not constant along the axial depth of cut, and it presents different shapes due to the cutting forces, which change according to the cutting strategy, end-mill geometry and cutting parameters, making the surface error prediction complex and time consuming. This paper presents a comprehensive classification of the shape of the cutting forces which cause the surface form errors, in both up and down-milling. The proposed classification includes analytical equations to obtain the axial position of key points (also known as kinks) defining the surface error shape in any cutting condition and tool geometry. The results given by the developed classification were experimentally validated trough different cutting tests to prove the reliability and the effectiveness of the proposed approach. The proposed classification and formulations manage to identify the surface error shapes both when several flutes are involved in the process and aggressive axial depths of cut are adopted, extending the knowledge about surface errors in peripheral milling. Furthermore, the proposed formulations could be exploited to ease error prediction methods based on simulations or drastically reduce the surface measuring time in quality control.

An experimental investigation on the effects of combined application of ultrasonic assisted milling (UAM) and minimum quantity lubrication (MQL) on cutting forces and surface roughness of Ti-6AL-4V

Ti-6Al-4V is widely used in aerospace, medical and defense industries where materials with superior characteristics are needed. However, Ti-6Al-4V is categorized as a difficult-to-cut material, and machining of this alloy is highly challenging. Ultrasonic Assisted Milling (UAM) is a quite recent method to facilitate the machining of difficult-to-cut materials. This method has numerous advantages over the Conventional Milling (CM) method, such as reduced cutting forces and increased surface quality. Besides, Minimum Quantity Lubrication (MQL) is an alternative cooling method to enhance the process efficiency with respect to conventional cooling methods. Cutting force and surface roughness are essential measures to evaluate the cutting performance of a machining process. However, the simultaneous effects of implementing MQL and ultrasonic vibrations in milling operations are not much researched yet. In this study, the combined effects of UAM and MQL on cutting forces and surface roughness during the machining of Ti-6AL-4V are investigated. Results show that the combination of MQL and UAM enhances the cutting forces in rough cutting operations and the surface roughness in both finish and rough cutting operations significantly compared to conventional processes. Consequently, it is concluded that simultaneous implementation of UAM and MQL enhances overall cutting performance in end-milling operation of Ti-6Al-4V.

Some Relationships among Residual, Micro-Structure, and Micro-Hardness Ensued due to Vertical End Milling Operations.(Dept.M)

The study residual stresses due to machining is a very important facet industrial applications such as in aircraft of the components. End milling tests were performed on free machining brass plates. Compressive residual stresses were left within the machined surfaces. Assessments of the distribution of resisdual stresses underneath the machined surface have been given via a post removal technique. Microstructural examinations were made utilizing an optical microscope. Nitric acid of 32.5% concentration was used as etchant for the sides of the plates to reveal the proper grain boundaries. The change in the average grain size with the sub-surface depth, after milling was determined. The milled sides of the free machining brass specimens were subjected, as well, to micro-hardness examinations via a 100 gram load starting from the specimen surface till no change in micro-hardness were noted. Relationships between the knop micro-hardness values and the sub-surface depth were, then, obtained. All the test results indicated that maxima for residual stresses and micro-hardness together with minima for average grain size occurred near the surface of the plates . Moreover, it was found that starting off such locations values of residual stresses and micro-hardness decreased while grain size increased inter-relations among these three variables under such conditions were, then, deduced.

Effect of Vertical End-Milling Operations up on some Mechanical Properties of Free Machining Brass Plates.(Dept.M)

Test sp ecimens made of as-received free machining brass plates having dimensions of (10x180x100) x 10-3m were vertical end milled from one or from two sides in some cases. Milling conditions varied from (0.1 to 1.2) x 10-3m depth of cut, and feed speed ranging between (0.4 to 1.58) x10-3 m/s for spindle speeds of (2.67 to 13.30) rev./s. Flat tensile test sp ecimens were made out of the same milled plates having 10x10-3m thickness and 50x10-3m gauge length. It was found, for cases of one side milling, that the increase of depth of cut from 0.1x10-3 m to 1.2x10-3m led to increases in the values of the maximum true tensilestrength from (600 to 650) MPa. On the other hand, the corresponding values. for double sides milling cases,varied from (620 to 670) MPa. The corresponding fracture strains ranged from 0.16 to 0.20 for cases ofmilling from one side to 0.125 to 0.175 for double sides milling cases. In all cases, slight decreases in the material true ultimate tensile stresses with noticeable increases in the fracture strains were noted upon the increase in spindle sp eeds. No change in the material strain-hardening exponents were noted through all the conducted tests. Material fatigue strength was taken to be equal to 0.3 of the true ultimate strength.

Automated Process Planning System for End-Milling Operation by CAD Model in STL Format

A method for extracting the machining region from a 3D CAD model in Standard Triangulated Language (STL) format and automatically generating a tool path is proposed. First, a method is proposed for extracting the machining region and obtaining the geometrical features such as a convex or concave shape from only the 3D CAD model in STL format. The STL format uses only triangular mesh data and drops all information, which is necessary for extracting the removal volume for the machining and geometrical characteristics. Furthermore, the triangular mesh size is non-uniform. A contour line model is proposed in which the product model is minutely divided on the plane along any one axial direction and is represented by points at intervals below the indicated resolution obtained from the contour line of the cross section of the product. Subsequently, a method is proposed to determine the machining conditions for each extracted machining region and automatically generate a tool path according to the geometrical features of the machining region obtained. A machining experiment was conducted to validate the effectiveness of the proposed method. As a result of the machining experiment, it was confirmed that the tool path automatically generated from the 3D CAD model in STL format can be machined without any problems and with a practical level of accuracy.

Investigation into the surface quality and stress corrosion cracking resistance of AISI 316L stainless steel via precision end-milling operation

This study presents a two-fold investigation on precision end-milling of stainless steel (AISI 316L). First, the impact of end-milling variables (cutting speed and feed rate) on the surface quality (surface roughness, microhardness, and surface morphology) was analyzed. The best surface quality with surface roughness (Ra) 0.65 ± 0.02 μm was observed for cutting speed of 140 m/min and 0.025 mm/tooth of feed rate. Microhardness was increased with increment in cutting speed. Second, the impact of surface roughness (Ra) on the stress corrosion cracking under two different mediums, i.e., body solutions (Hank’s solution) and 1 M hydrochloric acid solution, was studied. The investigations showed that the samples with higher surface roughness values were more prone to stress corrosion cracking.

Minimizing Flute Engagement to Adjust Tool Orientation for Reducing Surface Errors in Five-Axis Ball End Milling Operations

AbstractSurface errors due to force-induced tool and workpiece deflections are one of the major errors in multi-axis machining of parts especially with thin-walled structures. Dominant approaches to reduce these surface errors are re-machining the part, feed scheduling, and tool path modification. These methods are time consuming and computationally costly, and they rely on experimental data which is used in cutting force and deflection predictions. The present paper introduces a pure geometrical approach to reduce surface errors drastically by minimizing the engagement lengths of flutes’ cutting edges when a point on the flute’s cutting edge is in contact with the design surface. The total engagement length of the flutes’ cutting edges when one of them generates a contact point on the workpiece surface is formulated and considered as the minimization objective function of an optimization problem. Tilt and lead angles, which define the tool orientation, are the design variables of the optimization problem subjected to constraints based on the geometrical requirements of the ball end milling process. The optimization problem uses the nominal tool path to generate an optimal tool path with adjusted tool orientations. The presented method is computationally inexpensive and does not need any experimentally calibrated coefficients to predict cutting forces because of the pure geometrical nature of the approach. The method is experimentally validated through five-axis ball end milling experiments in which more than 90% surface error reduction is achieved.

Non-Invasive Estimation of Machining Parameters during End-Milling Operations Based on Acoustic Emission.

This work presents a non-invasive and low-cost alternative to traditional methods for measuring the performance of machining processes directly on existing machine tools. A prototype measuring system has been developed based on non-contact microphones, a custom designed signal conditioning board and signal processing techniques that take advantage of the underlying physics of the machining process. Experiments have been conducted to estimate the depth of cut during end-milling process by means of the measurement of the acoustic emission energy generated during operation. Moreover, the predicted values have been compared with well established methods based on cutting forces measured by dynamometers.

Mechanics of milling 48-2-2 gamma titanium aluminide

Accurate and fast prediction of cutting forces is important in high-performance cutting in the aerospace industry. Gamma titanium aluminide (γ-TiAl) is a material of choice for aerospace and automotive applications due to its superior thermo-mechanical properties. Nevertheless, it is a difficult to machine material. This article presents the prediction of cutting forces for Ti-48Al-2Cr-2Nb (48-2-2) γ-TiAl in milling process using orthogonal to oblique transformation technique. The novelty of this paper lies in reporting the orthogonal database of 48-2-2 γ-TiAl. Fundamental cutting parameters such as shear stress, friction angle and shear angle are calculated based on experimental measurements. Friction coefficients are identified for two different coating conditions which are AlTiN, and AlCrN on carbide tools. Predicted results are validated with the experimental cutting forces during end milling and ball-end milling operations for different cutting conditions. The simulated results showed good agreement with the experimental results, which confirms the validity of the force model.

Dynamic Modeling and Stability Studies on a Retrofitted Drill Spindle Using a Sensor-Based System

For the past decade, very few research had been carried out for the utilization of in-house machines such as the drilling, milling for several applications. For simple machining operations like slotting, grooving, etc., the use of CNC end-milling is a costly concern. This paper presents an optimized modeling concept for drill spindles employed for economical milling practices. To this end, a realistic spindle tool unit of a bench drilling machine is first analyzed to obtain the tool-tip frequency responses by both analytical and experimental approaches. To enhance the use of the drill spindles effectively for end-milling operation, its geometrical topology is modified by adding an additional bearing with a collar system, which improves its dynamic rigidity during the milling operation. Using the Timoshenko beam theory with the rotational and shear deformation affects the tool-tip frequency responses are arrived both numerically and experimentally. Further, a portable X–Y table is also fabricated as per the existing dimensions of the drilling machine to carry out the cutting tests for assessing the stability. Analytical stability lobe diagram is plotted for the modified optimal spindle, and further online detection of chatter during the machining process is identified by the sensors such as the accelerometer and microphone. The data acquisition methodology used in this work confirms the relevance of chatter monitoring at the earliest stages.

Applicability assessment and adaptation method of cutting conditions based on acceptable area to select cutting conditions for end-milling operation

Applicability assessment and adaptation method of cutting conditions based on acceptable area to select cutting conditions for end-milling operation

Effect of milling parameters on surface roughness: An experimental investigation

Milling is the very well-known machining technique; it is widely adopted in industries in the current age. The machining of Aluminum Alloy AA6062 based on a high-speed milling machine is very essential because of its applications in various industries i.e. Automobile, Shipbuilding etc. This paper deals with three main process parameters which affect the end milling process these are Feed rate, Depth of cut and spindle speed which influence the surface roughness of Aluminum Alloy AA6062 during end-milling operation. Different levels of surface roughness are measured through the Stylus profile meter of a surface roughness measuring machine Surftest SJ-210.