End Mill Cutter Research Articles

断続切削における工具逃げ面温度 高速エンドミル加工に関する研究 １

The temperature of cutting tool in high speed endmilling is measured using a two-color pyrometer with an optical fiber. This pyrometer has a flat response for the square-wave signal up to approximately 400kHz, which is enough speed to measure the temperature of an endmilling cutter passing at a cutting speed of 628m/min. The influence of cutting speed v and feed per tooth f on the cutting temperature at the flank face of the cemented carbide insert is investigated. The heating and cooling characteristics of the cutting tool during an intermittent cutting cycle are also examined. In dry cutting of carbon steel, the cutting tool temperature θα rises rapidly with the increase of cutting speed and θα reaches approximately 770°C at v=628m/min. The feed per tooth, however, has less effect on cutting tool temperature. The temperature change during an intermittent cutting process is about 150°C when v=471.2m/min and f=0.047mm/tooth. The temperature distribution along the contact edge between a tool and workpiece is almost uniform although those at tool tip and boundary region are somewhat higher.

Texture prediction of milled surfaces using texture superposition method

It is difficult to evaluate surface error in three- or multi-axis milling due to the complexity of the machining geometry. This paper presents texture superposition method to evaluate the surface asperity of milled surfaces. In order to derive overall surface generation mechanism of three different types of endmill cutters including a ball endmill, a filleted (torus-shaped) endmill, and a flat endmill, a generalized cutter model is proposed by introducing the fillet radius as a variable. The surface roughness is determined by the maximum height of the effective scallop including the effects of cutter marks and conventional scallops. The runout effect caused by the geometric inaccuracy of a cutter is added to make the predicted surface closer to the actual machined surface. Through these steps, three-dimensional surface topography, according to given cutting conditions and cutter types, can be formed. From machining experiments with a three-axis machining center, validity of the developed method was verified. The method proposed in this paper can be used to improve the efficiency of three- or multi-axis milling and to generate optimal cutter paths and cutting conditions.

Mathematical modelling using different endmills and tool placement problems for 4- and 5-axis NC complex surface machining

This paper presents the mathematical methods and algorithms to compute milling cutter placement and machined surface error analysis problems for 4- and 5-axis finished-surface machining. Different types of endmill cutters, such as the torusshaped (filleted) endmill, flat-endmill and sphere-endmill, are used for multi-axis NC machining. A generalized tool description with tool orientation variables for variant types of cutters is developed for 5-axis machining. Methods of finding an instantaneous cutting profile and the local surface geometry to analyse machined surface errors are discussed for cutter location generation. A method of deciding tool orientation to avoid rear tool collision using global geometry information is also presented. The techniques presented in this paper can be used to eliminate errors of milling tool path generation in the area of simultaneous multi-axis NC complex surface machining.

Geometric Design and Machining of Variable Pitch Lead Screws with Swinging and Translating Meshing Rollers

The design of variable pitch lead screws with swinging and translating meshing rollers is proposed in this study. Mathematical expressions representing the surface geometry of the screw generated by an endmill cutter are derived for the purpose of calculating the meshing points on the threaded surface of the screw. This mechanism is modeled using a Silicon Graphics workstation for motion simulation. Two examples are given. Our results show that constant thickness of screw threads can be attained using the design proposed. Finally, the machining settings of a 5-axis CNC machine are provided for manufacture of the screws.

Model-Based Cutting Simulation System for Prediction of Cutting States.

This paper describes a cutting simulation system which has the function of physical simulations as well as geometrical simulations. In the geometrical simulation, changes in workpiece geometry in the course of cutting processes are evaluated based on a solid modeling system. In the physical simulation, physical parameters of cutting processes are evaluated based on physical models. Instantaneous cutting force can be estimated by composing cutting force vectors acting on infinitesimal parts of flutes. Cutting error is then estimated based on tool deflections induced by the cutting force. A system for simulating the cutting process using a square end mill cutter has been developed based on a geometric modeler with boundary representations. A number of cutting experiments were conducted for various tools and cutting conditions. The results of experiments proved the accuracy of estimations by the simulation system.

Detection of the Rotating Cutting Tool Failure with an Acoustic Emission Sensor.

This study focuses on the detection of rotating cutting tool failure and proposes a method using an acoustic emission (AE) sensor to detect chipping of the cutting edge on the end-mill cutter and cutting tool breakage of the twist drilling cutter. In order to detect the AE signal from the rotating cutting tool, the AE sensor is coupled with the cutting fluid supply system and the cutting fluid is used as the medium which transmits the AE signal. This sensor system was designed through a series of frequency response measurements of the AE signal in fluid flow. In the frequency characteristics of the AE signal when the chipped tool is used, characteristic peaks are observed at the frequency which is associated with the rotational frequency of the spindle and its harmonic frequency. Using this phenomenon, a practical algorithm for detecting cutting edge chipping has been developed. A practical method is also proposed to detect twist drill breakage.

Design and machining of cylindrical cams with translating conical followers

A simple approach to the profile determination and machining of cylindrical cams with translating conical followers is presented. On the basis of the theory of envelopes for a 1-parameter family of surfaces, a cam profile with a translating conical follower can be easily designed once the follower-motion program has been given. In the investigation of geometric characteristics, it enables the contact line and the pressure angle to be analysed using the obtained analytical profile expressions. In the process of machining, the required cutter path is provided for a tapered endmill cutter, whose size may be identical to or smaller than that of the conical follower. A numerical example is given to illustrate the application of the procedure.

アコースティックエミッションセンサを用いたフライス加工状態の自動監視

Automatic monitoring of cutting process is one of the most important technologies for increasing the stability and the reliability of unmanned manufacturing system. In this study, the methods which use acoustic emission (AE) signals are proposed to monitor chatter vibration, tool wear and cutting edge breakage in the milling process. All experiments were conducted on an NC-vertical milling machine. The ball endmill cutter with 2 cutting edges and the square endmill cutter with 4 cutting edges were used. Using these equipment, the single-sensor monitoring system was constructed.

A computer-aided prototype system for NC rough milling of free-form shaped mechanical part-pieces

A prototype computer-aided manufacturing module for rough milling of free-form mechanical moulds is proposed. The system allows direct modelling of the shape of the material to be removed, by starting from the geometry of the stock and of the final part-piece. A modelling engine, based on rational bivariate and trivariate tensor-product B-spline patches, was developed to ensure complete geometric coverage, allowing common analytic geometric items such as planes, quadrics, and blocks to be exactly modelled. Methods for the evolution of the milling layers, the choice of isoparametric NC tool-paths and their piecewise approximation are proposed; the procedures work in the context of three-axis machining by end-mill cutters. Technological considerations about the main cutting force the follow: it results that fine tuning of the milling feed rate can be computed by geometric evaluation of the depth and width of cut. To demonstrate the feasibility of the approach, an application example concerning mould manufacturing is reported.

Automated Rapid Prototyping Utilizing Laser Scanning and Free-Form Machining

The paper deals with the use of a laser based method for rapid prototyping of free-form and quadric surface multiple patch models. Integration of a triangulation based laser scanner with a CNC machining centre is discussed. Methods of analysis of the mass of irregular and unformatted positional data generated by the scanner are presented in order for a series of basic quadric and compound curved surfaces to be defined. The procedure for defining the CNC cutter path for a generalised shaped end-milling cutter is given with illustration of the applicability of the method to a variety of test objects. The work is a new approach utilising laser scanned data for direct machining of quadric and free-form surfaces.

Tool-path generation in manufacturing sculptured surfaces with a cylindrical end-milling cutter

This paper presents three kinds of algorithms for generating tool paths and the corresponding tool-centre paths in order to improve the surface finish in the machining of sculptured surfaces with a cylindrical endmilling cutter. B-splines are used to define the boundaries of Coons patches.

A Practical Mounting Device for an Acoustic Emission Sensor for the Failure Detection of Multipoint Cutting Tools

This paper will introduce a new sensor coupling device for milling machines, drilling machines and for the machine center. Within the industry there has always been the need for a practical application of the sensor coupling device to detect the cutting process related signals from the “tool side”. A mounting device which enables the sensor to be fixed close to the rotating multipoint cutting tool has been developed to meet this need. Thus a more practical method for detecting the tool fracture of twist drills and/or tool chipping of an end mill cutter becomes possible. The machining process associated signals are high frequency Acoustic Emission (AE) signals detected from the spindle top of the machine being used. In this study two kinds of AE-signals will be compared. The first are those detected from the spindle housing. The second are signals detected from the spindle top using the newly developed sensor coupling device. Furthermore, the structure of an AE-monitoring system for supervising multipoint cutting tools will be described. In addition, results of experiments which monitor the tool health coefficient, derived from the power spectrum of the machining signals, will be discussed.

Computer-aided Fairing and Direct Numerically Controlled Machining of Ship Hull Hydrodynamic Testing Models

A computer-aided method of defining and machining 2-metre ship hull forms for hydrodynamic testing is described. The hull shape is faired from the original table of off-sets using a minimum number of smooth three-dimensional parametric skeletal-lines along the length of the boat. A fine set of smoothly blending station-lines is therby formed. The hull shape is preformed in two halves through a lamination process and machined on a three-axis numerically controlled machining (CNC) centre. A carbide-tipped, end-milling cutter is directed along the closely spaced station-lines to rapidly form an accurate hull shape requiring a minimum of hand work. The fairing and machining programs, called G-surf, run on a personal computer and are used to transmit the data and control the CNC machine in real time. The resulting hull shape is symmetrical and far more accurate than manually lofted and preshaped models.

Modeling and measurement of wear of coated and uncoated high speed steel end mills

A research program was conducted to study tool wear on uncoated and coated (with TiN) high speed steel (HSS) for fluted end mill cutters. These cutters were used to machine AISI 4340 steel at axial and radial engagements of 12.7 mm (0.5 in.). All the machining was carried out using production conditions with the process periodically interrupted to carefully measure the wear condition of the cutting tool. Cutting conditions were carefully chosen so that a linear wear model for the useful life of the cutting tool could be statistically tested. One phase of testing used uncoated tools from 30 different suppliers and the nonstationary linear wear model provided a stochastic representation to determine tool quality using reliability and economic measures. Another phase used the coated tools and a stationary linear wear model to relate force, power, specific cutting energy, and mechanistic model parameters to service life measures. The cutters from each of these phases were carefully examined using optical and scanning electron microscopes so that the dominant wear mechanisms could be identified.

The definition and manufacture of compound curvature surfaces using G-surf

G-surf is a method for defining and machining the compound curvature surfaces encountered in many engineering applications. The surfaces are defined by orthogonal grids of B-spline space curves and machined with a cylindrical end-milling cutter inclined at predetermined angles to the surface normals. The approach proves to be very flexible and, as the cutter operates at a full and select cutting speed, gives an efficient means of material removal. Surface finish and cutter interference are both affected by cutter inclination to the surface normal and can be adjusted for optimum conditions. The interactive menu-driven package fits onto microcomputer installations and is suitable for small- to medium-size manufacturing companies.

Influence of Chatter of VMC Arising During End Milling Operation and Cutting Conditions on Quality of Machined Surface

Machine tool chatter is a dynamic instability of the cutting process. Chatter results in poor part surface finish, damaged cutting tool, and an irritating and unacceptable noise. Exten¬sive research has been undertaken to study the mechanisms of chatter formation. Efforts have been also made to prevent the occurrence of chatter vibration. Even though some progress have been made, fundamental studies on the mechanics of metal cutting are necessary to achieve chatter free operation of CNC machine tools to maintain their smooth operating cycle. The same is also true for Vertical Machining Centres (VMC), which operate at high cutting speeds and are capable of offering high metal removal rates. The present work deals with the effect of work materials, cutting conditions and diameter of end mill cutters on the frequency-amplitude characteristics of chatter and on machined surface roughness. Vibration data were recorded using an experimental rig consisting of KISTLER 3-component dynamometer model 9257B, amplifier, scope meters and a PC. Three different types of vibrations were observed. The first type was a low frequency vibration, associated with the interrupted nature of end mill operation. The second type of vibration was associated with the instability of the chip formation process and the third type was due to chatter. The frequency of the last type remained practically unchanged over a wide range of cutting speed. It was further observed that chip-tool contact processes had considerable effect on the roughness of the machined surface.Key Words: Chatter, Cutting Conditions, Stable Cutting, Surface Roughness.

Protection of reservoirs

The geometry of cutting flutes and the surfaces of end mills is one of the crucial parameters affecting the quality of the machining in the case of end milling. These are usually represented by two-dimensional models. This paper describes in detail the methodology to model the geometry of a flat end mill in terms of three-dimensional parameters. The geometric definition of the end mill is developed in terms of surface patches; flutes as helicoidal surfaces, the shank as a surface of revolution and the blending surfaces as bicubic Bezier and biparametric sweep surfaces. The proposed model defines the end mill in terms of three-dimensional rotational angles rather than the conventional two dimensional angles. To validate the methodology, the flat end milling cutter is directly rendered in OpenGL environment in terms of three-dimensional parameters. Further, an interface is developed that directly pulls the proposed three-dimensional model defined with the help of parametric equations into a commercial CAD modeling environment. This facilitates a wide range of downstream technological applications. The modeled tool is used for finite element simulations to study the cutting flutes under static and transient dynamic load conditions. The results of stress distribution (von mises stress), translational displacement and deformation are presented for static and transient dynamic analysis for the end mill cutter flute and its body. The method described in this paper offers a simple and intuitive way of generating high-quality end mill models for use in machining process simulations. It can be easily extended to generate other tools without relying on analytical or numerical formulations.