An experimental investigation of rotary ultrasonic face milling

Reliable and cost-effective machining of advanced ceramics is crucially important for them to be widely used in a number of critical engineering applications. The potential of Rotary Ultrasonic Machining (RUM) process has been recognized as one of the reliable and cost-effective machining methods for advanced ceramics and commercial machinery is available for the process. One limitation of the commercial RUM machines is that only circular holes can be efficiently machined. An approach to extend the RUM process to face milling of ceramics was proposed and the development of the experimental apparatus as well as the preliminary experimental results were published earlier in this journal. As a follow-up, this paper will present the results of an experimental investigation of the newly-developed Rotary Ultrasonic Face Milling (RUFM) process. In this investigation, a five-variable two-level fractional factorial design is used to conduct the experiments. The purpose of these experiments is to reveal the main effects as well as the interaction effects of the process parameters on the process outputs such as Material Removal Rate (MRR), cutting force, material removal mode and surface roughness.     

Minimization of exit burr in face milling of medium carbon steel by exit edge beveling

Elimination, or reduction, of burrs formed during machining is drawing focus of manufacturers and researchers since long or suppressing a burr regarding its formation or removal of it through a suitable deburring process. Deburring is an extra process often required to undertake, and it involves additional time and cost. Presence of burr may cause several problems, such as difficulty in assembly, dimensional inaccuracy, injury to the operator, etc. Like other industries, avoidance of burr on milled component surfaces in railways is of concern. In the present investigation, formation of burr in face milling is tried to reduce by beveling the exit edge of blocks of medium carbon steel (45C8) which is widely used in railways for manufacture of different components. Cutting conditions are also varied to observe the effect on burr formation. It is observed that at an exit edge bevel angle of 15°, negligible burr is formed at most of the cutting conditions undertaken, and hence, recommended.     

An experimental technique for the measurement of temperature on CBN tool face in end milling

An infrared radiation pyrometer with two optical fibers connected by a fiber coupler was developed and applied to the measurement of tool–chip interface temperature in end milling with a binderless CBN tool. The infrared rays radiated from the tool–chip interface and transmitted through the binderless CBN are accepted by the optical fiber inserted in the tool and are then sent to the pyrometer. A combination of the two fibers and the fiber coupler makes it possible to transmit the accepted rays to the pyrometer, which is set up outside of the machine tool. This method is very practical in end milling for measuring the temperature history at tool–chip interface during chip formation. The maximum tool–chip interface temperature in up milling of a 0.55% carbon steel is 480 °C when the cutting speed is 2.2 m/s and 560 °C at 4.4 m/s, and in the down milling, 500 °C at 2.2 m/s and 600 °C at 4.4 m/s.     

A study of high efficiency face milling tools

A new predictive force model for a single-tooth face milling cutter with a chamfered main cutting edge has been derived. Machining tests has been conducted for fly cutting with a chamfered main cutting edge tools on plane surfaces. An S45C medium carbon plate has been used as the workpiece matrial. Force data from these tests were used to estimate the empirical constants of the mechanical model and to verify its prediction capabilities. The results show a good agreement between the predicted and measured forces.Since tool manufacturers does not provide tools with selected combinations of chamfered main cutting edge, radial angle, axial angle and inclination angles, tool holders manufactured in-house were used in the tests. The tips were prepared to the required geometry using a tool grinder.     

A study on instantaneous cutting force coefficients in face milling

In this paper, the characteristics of instantaneous cutting force coefficients in face milling are studied. In order to estimate instantaneous cutting force coefficients in face milling, the relationships between instantaneous cutting force coefficients and measured cutting force signals are derived. A series of experiments are then conducted to study the natures of instantaneous cutting force coefficients. The relationships between instantaneous cutting force coefficients and other cutting parameters are also established. It is found that the normal force coefficient is mainly affected by chip thickness and cutting speed; the vertical force coefficient is mainly affected by chip thickness, cutting edge length and cutting speed; and that the horizontal force coefficient is not only affected by chip thickness, cutting speed and length of cut, but also the variation rate of chip thickness.     

Predicting cutting forces in face milling

It is shown how orthogonal machining theory can be applied to predict the cutting forces in face milling from a knowledge of the work material properties and cutting conditions. Predicted and experimental results are compared.     

Micro electric discharge milling process performance: An experimental investigation

Micro electric discharge milling (μED-milling) process is gaining lot of interest in the area of microfabrication specifically for hard to machine materials. Any complex shape can be generated with a controlled motion of cylindrical tool in a predefined path similar to conventional micromilling. In this method the material removal mechanism in tool and workpiece is complex and requires a detail study of the process parameters. Parameters such as tool rotation speed, feed rate and aspect ratio (AR) can play a vital role in μED-milling process along with the fundamental parameter such as energy. This research work aims to provide exhaustive study of parameters on material removal rate (MRR) and tool wear rate (TWR) by conducting general factorial experiments. A new method is proposed to measure the volume of material eroded from workpiece and tool with an aid of design software. The experimental result shows that the parameters have individual and combined effect on MRR and TWR. Among the parameters, tool rotation speed has a significant function in flushing away the debris to ensure stable discharge. Detailed surface morphology of the machined features has also been analyzed using scanning electron microscope (SEM). A regression analysis was carried out to establish models for MRR and TWR as a function of process parameters.     

Experimental studies of cutting force variation in face milling

The purpose of this paper is to present a developed cutting force model for multi-toothed cutting processes, including a complete set of parameters influencing the cutting force variation that has been shown to occur in face milling, and to analyse to what extent these parameters influence the total cutting force variation for a selected tool geometry. The scope is to model and analyse the cutting forces for each individual tooth on the tool, to be able to draw conclusions about how the cutting action for an individual tooth is affected by its neighbours.A previously developed cutting force model for multi-toothed cutting processes is supplemented with three new parameters; eccentricity of the spindle, continuous cutting edge deterioration and load inflicted tool deflection influencing the cutting force variation. A previously developed milling force sensor is used to experimentally analyse the cutting force variation, and to give input to the cutting force simulation performed with the developed cutting force model.The experimental results from the case studied in this paper show that there are mainly three factors influencing the cutting force variation for a tool with new inserts. Radial and axial cutting edge position causes approximately 50% of the force variation for the case studied in this paper. Approximately 40% arises from eccentricity and the remaining 10% is the result of spindle deflection during machining. The experimental results presented in this paper show a new type of cutting force diagrams where the force variation for each individual tooth when two cutting edges are engaged in the workpiece at the same time. The wear studies performed shows a redistribution of the individual main cutting forces dependent on the wear propagation for each tooth.     

Rotary ultrasonic machining for face milling of ceramics

Among the various material removal processes applicable to ceramic materials, rotary ultrasonic machining has the potential for high material removal rate while maintaining low machining pressure and resulting in less surface damage. The limitation of rotary ultrasonic machining is that only circular holes or cavities can be machined due to the rotary motion of the tool. Attempts have been made by other researchers to extend rotary ultrasonic machining process to machining flat surfaces or milling slots. However, these extensions either changed the material removal mechanisms or had some severe drawbacks. One of the reasons for this might be an insufficient understanding of the material removal mechanisms involved. In this paper, a new approach to extend rotary ultrasonic machining to face milling of ceramics is proposed, which keeps all the material removal mechanisms of rotary ultrasonic machining. The development of the experimental apparatus and the design of the cutting tool are described. Preliminary experimental results are presented and discussed.     

Improvement of workpiece quality in face milling of aluminum alloys

The compliance with the quality requirements of components is essential for the functionality of the whole product. With respect to parts with face-milled faces, the surface quality and the shape of the workpiece edges are of great interest. Frequently, these faces take over the function of seal faces where high demands on the surface integrity and burr formation exist. To ensure the workpiece quality that is required, nowadays additional processes for deburring are often necessary. To avoid deburring, the modification of machining processes is a promising approach. In this study, the influence of process cooling on workpiece quality is investigated. Using this approach, two effects are expected. The cooling is used to minimize a reduction of flow stress generated from the process heat, which than leads to a lower formability. The second effect relates to the kinetic energy of the snow blast for deburring by deformation and breakage of the burrs. Using a process cooling with carbon dioxide, the surface quality is enhanced and the burr formation is minimized.     

Micro milling of titanium alloy Ti-6Al-4V: 3-D finite element modeling for prediction of chip flow and burr formation

Cutting process of titanium alloy Ti-6Al-4V is considered difficult due to chemical affinity between tool and work material, adhesion, built-up edge and burr formation, and tool wear resulting in loss of productivity. Three dimensional (3-D) chip flow together with local field variables such as temperature, elastic/plastic strain, strain-rate and velocity in the shear zones during micro milling process can be predicted using continuum-mechanics based 3-D Finite Element (FE) modelling and simulation of elastic/viscoplastic work material deformations. This paper provides much needed process insight for chip flow, built-up edge and burr formation by using modeling work with experimental validation. Scanning electron microscopic (SEM) observation of the 3-D chip morphology and burrs demonstrate ductile fractured surfaces together with localized instability and failure behaviors. FE simulations are utilized to investigate the effects of micro milling operation i.e. up and down milling and tool edge radius on 3-D chip flow, built-up edge, and 3-D burr formation. Simulated results are compared with measurements of chip morphology, shape, and dimensions together with tool edge condition of built-up edge and chip adhesion yielding to good agreements.     

Chip formation in grinding: an experimental study

Due to high cutting speeds and low single grain chip thicknesses no reliable approach to interrupt the cut in grinding was realized so far. This paper presents a new method to experimentally obtain and analyze chip roots during up-grinding. By means of high resolution SEM-micrographs several chip roots are analyzed, classified and discussed with regard to the fundamental chip formation and material removal mechanisms. Furthermore, there are conclusions drawn about the distribution and number of the active grains, which are in a good correlation with the Abbott-curve of the grinding wheel layer and the process parameters.     

铣削力建模与计算机仿真

本文综合分析了切削过程中刀具几何参数对端铣铣削力的影响，对铣削力模型进行了修正，建立了适合端铣铣削力计算机仿真的铣削力模型。并对仿真结果与实际测试曲线进行了比较。     

Performance-based optimization of multi-pass face milling operations using Tribes

The paper proposes a new optimization technique based on Tribes for determination of the cutting parameters in multi-pass milling operations such as plain milling and face milling by simultaneously considering multi-pass rough machining and finish machining. The optimum milling parameters are determined by minimizing the maximum production rate criterion subject to several practical technological constraints. The cutting model formulated is a nonlinear, constrained programming problem. Experimental results show that the proposed Tribes-based approach is both effective and efficient.     

Tool breakage diagnosis in face milling by support vector machine

This paper introduces a new diagnosis technique for tool breakage in face milling using a support vector machine (SVM). The features of spindle displacement signals are first fed into the kernel-based SVM decision function. After the SVM learning procedure, the SVM can respond in real-time to automatically diagnose tool fracture under varying cutting conditions. Experimental results show that this new approach can detect tool breakage in a wide range of face-milling operations.     

An experimental study of tool wear and cutting force variation in the end milling of Inconel 718 with coated carbide inserts

Inconel 718 is a difficult-to-cut nickel-based superalloy commonly used in aerospace industry. This paper presents an experimental study of the tool wear propagation and cutting force variations in the end milling of Inconel 718 with coated carbide inserts. The experimental results showed that significant flank wear was the predominant failure mode affecting the tool life. The tool flank wear propagation in the up milling operations was more rapid than that in the down milling operations. The cutting force variation along with the tool wear propagation was also analysed. While the thermal effects could be a significant cause for the peak force variation within a single cutting pass, the tool wear propagation was believed to be responsible for the gradual increase of the mean peak force in successive cutting passes.     

Sensing tool breakage in face milling with a neural network

A new approach using a neural network to process the features of the cutting force signal for the recognition of tool breakage in face milling is proposed. The cutting force signal is first compressed by averaging the cutting force signal per tooth. Then, the average cutting force signal is passed through a median filter to extract the features of the cutting force signal due to tool breakage. With the back propagation training process, the neural network memorizes the feature difference of the cutting force signal between with and without tool breakage. As a result, the neural network can be used to classify the cutting force signal with or without tool breakage. Experiments show this new approach can sense tool breakage in a wide range of face milling operations.     

An experimental study of the formation of typical dislocation patterns in polycrystalline copper under cyclic shear

The typical slip patterns and dislocation substructures of polycrystalline copper under cyclic torsion were experimentally investigated. The cyclic stress–strain curve of the material consisted of three regions, resembling those of single crystal copper oriented for single slip. During the formation of persistent slip bands, cross slip bands between primary slip bands were often observed. Under cyclic torsion at a high shear strain amplitude, cross slip between slip bands of each slip system was an important process for the collapse of dislocation tangles into dislocation cell walls. During the transient stage of the formation of dislocation cells, the stress amplitude was inversely proportional to the average diameter of dislocation cells. This relationship is identical to that between the saturated stress magnitude and the corresponding dislocation cell size. The formation of typical dislocation patterns in copper under cyclic loading is closely associated with cross slip of screw dislocations.     

Optimization and control of drilling burr formation of AISI 304L and AISI 4118 based on drilling burr control charts

Control charts for drilling burr formation for stainless, AISI 304L, and low alloy steel, AISI 4118, were developed. Split point twist drills are used for the experiments of this work. A Drilling Burr Control Chart, based on experimental data, is a tool for prediction and control of drilling burrs. Burr classification was carried out based on the geometric characteristics, burr formation mechanisms and sizes of the burrs. New parameters consisting of cutting condition variables and drill diameter were developed, and used to show unique distributions of the burr types. Burr types and the resultant burr size showed great dependence on the new parameters regardless of the drill diameters. Through the chart, burr type can be predicted with given cutting conditions. Also cutting conditions that are believed to create preferred burr types can be selected.     

汽车钣金拉伤与开裂的形成机理研究

基于主机厂模具运行状态的系统管理与质量跟踪,阐述了钣金拉伤与开裂的形成机理,并从模具零件材质、硬度及表面粗糙度3个方面解析其产生拉伤与开裂的影响因素,并指出改善汽车覆盖件成形过程中表面拉伤与开裂缺陷的控制方向,可为冲模零件表面状态参数设计及主机厂生产运行管理提供参考。