Flat End Mill Research Articles

Machinability Improvement by Workpiece Preheating during End Milling AISI H13 Hardened Steel

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.

A novel mechanics model of parametric helical-end mills for 3D cutting force prediction

Cutting force prediction plays an important role in modern manufacturing systems to effectively design cutters, fixtures, and machine tools. A novel mechanics model of parametric helical-end mills is systematically presented for three-dimensional (3D) cutting force prediction in the article, which is different from mechanistic approach and Oxley’s predictive machining theory in model formulation and shear stress identification process. The single-flute cutting edge and multiflute cutting edge of helical-end mills are modelled according to kinematic analysis with vector algebra. Based on Merchant’s oblique cutting theory, a new mechanics model of 3D cutting force with runout has been developed. Meanwhile, the asynchronous problem between predicted and measured curves is solved by adjusting phase angle to minimize the average deviation. After minimizing the asynchronous phase angle deviation, shear stress can be estimated directly using corresponding peak-to-peak ratio or valley-to-valley ratio of the predicted curves and the measured curves in X- and Y-directions of an arbitrary selected milling test. To assess the feasibility of the general model, over 100 milling experiments of aluminium alloy (7075) using flat-end mills and ball-end mills were conducted, respectively, and numerical tests implemented in time domain on MathWorks platform. The comparative results indicated that the predicted and the measured waveforms were quite satisfied in both pulsation pattern and period.

Comparative Study on 2A70 Aluminum Alloy High-Speed Milling Cutting Force Model

The mechanical properties of flat end mill is analyzed the high-speed milling, the linear model for milling force is established. And the 2A70 aluminum alloy four-factor four-level orthogonal milling tests are carried out, the nonlinear model of milling is set up by using regression analysis method. The comparative analysis is made between the linear model and nonlinear model, whose results show that the two models have good agreement on the value and trend of change, which is the basis of the follow-up tool path optimization, fault diagnosis and so on.

A Method of Automatic Detection and Avoidance of Local Interference in Five-Axis Machining with Flat-End Cutter

This paper presents a new method of automatic detection and elimination of local interference methodology for five-axis complex surface machining with a flat-end milling cutter based on the technique of curvature matching and square grid points. A diameter of milling cutter was chosen by curvature matching to ensure interference-free at the point where the cutter and part contact. In odder to detect if rear interference occurs at the adjacent domain of contact point, the square grid points were employed to quickly build checking area and checking points. A technology of automatically generating square grid points and the method of detection and avoidance of local interference were also presented in this paper. Finally, the proposed methodology and algorithms were tested and verified by an example of NURBS surface.

Design of a CAM System for End Mills Based on Solid Modeling

To facilitate the manufacturing of an end mill, this paper presents a manufacturing model of a flat-end mill using a five-axis computer numerical control (CNC) grinding machine. Using input data of end mill geometry, wheels geometry, wheel setting and machine setting, the NC code for machining will be generated directly from a solid modeling then used as input to simulate the end mill machining in 3 Dimension before machining. The 3D simulation system of the end mill grinding is generated by VBA and AutoCAD2008. Machining simulation consists of a sequence of Boolean operations on difference between the tool and the grinding wheels through NC code. Then the major design parameters of a cutter, such as relief angle and inner radius, can be verified by interrogating the section profile of its solid model. The manufacturing model presented in this paper provides a practical and efficient method for developing CAM software for the manufacture of an end mill.

Effective Determination of Feed Direction and Tool Orientation in Five-Axis Flat-End Milling

This paper addresses the challenging problem of determining feed direction and tool orientation at a given cutter contact (CC) point in five-axis free-form surface machining with flat-end mills. The objective is to efficiently determine a feed direction and tool orientation that will avoid both local and global tool gouging and yield a near maximum machining strip width at the CC point. Concurrent determination of the optimal feed direction and tool orientation is a very computationally intensive task and searching for the correct solution would involve exhaustive evaluations of the machining strip width at many feed directions and tool orientations. In this paper, the optimal feed directions and analytical solutions for the optimal tool orientations in five-axis flat-end milling of spherical, cylindrical, and toroidal surfaces are identified first. A toroidal surface inscription method is devised to approximate the local surface geometry at a CC point on a free-form surface by an inscribed toroidal surface. Analytical solutions for toroidal surface machining are then employed to position the flat-end mill at the CC point with the tool feeding in the best toroidal surface inscribing direction. Case studies have demonstrated that the proposed method can efficiently determine a feed direction and tool orientation, corresponding to a near maximum machining strip width.

Cutting force modeling for flat end milling including bottom edge cutting effect

This study proposes a novel mechanistic cutting force model for flat end milling. The prominent feature of this model lies in that the overall cutting forces contributed by both the flank edge and the bottom edge cuttings are simultaneously taken into consideration. In the model formulation, to reflect the size effect in flank cutting, the flank cutting force coefficients are treated as an exponent function of instantaneous uncut chip thickness and are identified by nonlinear least-square algorithm. With the help of the calibrated flank cutting force coefficients, the bottom cutting force coefficients are instantaneously calibrated by the force component that is obtained by subtracting the flank force component from the total measured force. It is shown that the bottom cutting force coefficients can be treated as constants. The validity of the proposed cutting force model is also experimentally demonstrated over a relatively wide range of cutting conditions. It turns out that the bottom edge cutting has a remarkable effect on total cutting forces, when the axial depth of cut is relatively small.

Tool path generation and modification for constant cutting forces in direction parallel milling

This paper presents an optimized path generation algorithm for direction parallel milling, which is commonly used in the roughing and finishing stages. First, a geometrically efficient tool path generation algorithm using an intersection points graph is introduced. Second, the generated tool path is modified as an optimized tool path that maintains a constant material removal rate to achieve a constant cutting force and avoid chatter vibration, and the results are verified. Additional tool path segments are appended to the basic tool path through a pixel-based simulation technique. The algorithm is implemented for two-dimensional contiguous end milling operations with flat end mills, and cutting tests are conducted by measuring the spindle current, which reflects the changing machining situations, to verify the performance of the proposed method.

Optimum tool path generation for 2.5D direction-parallel milling with incomplete mesh model

Many mechanical parts are manufactured by milling machines. Hence, geometrically efficient algorithms for tool path generation, along with physical considerations for better machining productivity with guaranteed machining safety, are the most important issues in milling. In this paper, an optimized path generation algorithm for direction-parallel milling, a process commonly used in the roughing stage as well as the finishing stage and based on an incomplete 2-manifold mesh model, namely, an inexact polyhedron widely used in recent commercialized CAM software systems, is presented. First of all, a geometrically efficient tool path generation algorithm using an intersection points-graph is introduced. Although the tool paths obtained from geometric information have been successful in forming desired shapes, physical process concerns such as cutting forces and chatters have seldom been considered. In order to cope with these problems, an optimized tool path that maintains a constant MRR for constant cutting forces and avoidance of chatter vibrations, is introduced, and verified experimental results are presented. Additional tool path segments are appended to the basic tool path by means of a pixel-based simulation technique. The algorithm was implemented for two-dimensional contiguous end milling operations with flat end mills, and cutting tests measured the spindle current, which reflects machining characteristics, to verify the proposed method.

Roughness improvement in machining operations through coupled metamodel and genetic algorithms technique

Due to the widespread use of highly automated machine tools, manufacturing requires reliable models and methods for the prediction of output performance of machining processes. The prediction of optimal machining conditions for good surface finish and dimensional accuracy plays a very important role in process planning. The present work deals with the study and development of a surface roughness prediction model for machining Al7075-T6, using Response Surface Methodology (RSM). Machining operations of work pieces made by Al7075-T6 covering a wide range of machining conditions have been carried out with by flat end mill with four teeth made by High Speed Steel. A RS model, in terms of machining parameters, was developed for surface roughness prediction using the Radial Basis Functions (RBF) technique. This model gives the process response sensitivity to the individual process parameters. An attempt has also been made to optimize the surface roughness prediction model using Genetic Algorithms (GA).

Tool Path Generation Method of Equal Approximation Error for Free-Form Surface in High Speed Machining

The development of surface high-speed machining has put forward higher demands for uniform cutting load and smooth cutting tool path. Most current tool-path planning methods are based on constant scallop height, but they have the disadvantage of path point redundancy during the path discretization process. To overcome the problem, a tool path generation method of equal approximation error in each step for free-form surface is presented based on geodesic principle and curvature judgment. In this method, the NURBS curve is employed to realize smooth transition for adjacent two tool paths in high-speed machining. A certain angle of inclination of flat-end milling cutter during multi-axis machining improves the machining efficiency. Because of the advantage of this machining condition, the cutter location point generation algorithm during the machining condition is given by the method. The method is verified and simulated by C++. Experiment results proved that it can obtain uniform cutting load and continuous smooth cutting tool path during surface high-speed machining by the proposed method.

A manufacturing model of an end mill using a five-axis CNC grinding machine

This paper presents a manufacturing model of a flat-end mill using a five-axis computer numerical control (CNC) grinding machine. The profile of the helical groove can be precisely calculated using a given wheel profile and the relative movements between the workpiece and the grinding wheel. The results of the calculation of the numerical control (NC) data for all the grinding processes of the end mill are fully presented in the paper. The NC data for the machining end mill were generated from the developed program by using the given design parameters of tool geometry, wheel geometry, wheel setting, and machine setting. The effects of the design and manufacturing of the end mill were analyzed based on the computer simulation and experiment results. This study provides a practical and efficient model for the manufacturing of an end mill using a CNC grinding machine with simple programming techniques. The prediction of the end mill geometry for the designing of the proper configuration of the end mill before manufacturing and generating the NC code for machining in a CNC machine is necessary to save time and to reduce the manufacturing cost.

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.

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.

A new accurate curvature matching and optimal tool based five-axis machining algorithm

Free-form surfaces are widely used in CAD systems to describe the part surface. Today, the most advanced machining of free from surfaces is done in five-axis machining using a flat end mill cutter. However, five-axis machining requires complex algorithms for gouging avoidance, collision detection and powerful computer-aided manufacturing (CAM) systems to support various operations. An accurate and efficient method is proposed for five-axis CNC machining of free-form surfaces. The proposed algorithm selects the best tool and plans the toolpath autonomously using curvature matching and integrated inverse kinematics of the machine tool. The new algorithm uses the real cutter contact toolpath generated by the inverse kinematics and not the linearized piecewise real cutter location toolpath.

Evaluation of machinability according to the changes in machine tools and cooling lubrication environments and optimization of cutting conditions using Taguchi method

This study analyze the effect of machine tools, cooling lubrication environments and cutting conditions on surface roughness and cutting force, and propose the combination of cutting conditions which minimizes the effect of machine tool variables on the dispersion of cutting force and surface roughness by treating the changes in machine tool itself and the installation environments as a noise factors. To do so, the Taguchi method is used to establish an experiment plan, and flat end milling is carried out to measure cutting force and surface roughness. The research results show that in the case of cutting force, the effect of cutting conditions is dominant, and changes in machine tools and cooling lubrication environments barely have effect on cutting force. However, in the case of surface roughness, all of the cutting conditions, machine tool and cooling lubrication environment variables have impact. In order to select a combination of cutting conditions insensible to changes in machine tools, considerations for feed per revolution and axial depth of cut turn out most important in the aspect of cutting force, and considerations for feed per revolution is most important in the surface roughness.

Experimental Characteristics of Aluminum Alloys in Dry End Milling

This paper describes the cutting characteristics of aluminum alloys in dry end milling experimentally. The tested materials are A1050, A2017, A2024, A5025 and A7075. The cutter is a flat end mill of Co-cemented High Speed Steel with the diameter of 20 mm. Through the experimental results of side milling, the following three aspects have been found out. Firstly, as to the machining error, A1050 showed smaller machining error than 15 μm in the cutting speed rage from 62.8 m/min to 251.3 m/min. Other Aluminum alloys showed greater values. Secondly, as to the cutting force, those of aluminum alloys except A2017 were generally proportional to their material hardness. The cutting forces of A1050 and A5052 were constant over the whole range of cutting speed. Thirdly, as to the machined surface roughness, A7075 showed the smallest surface roughness among the all materials with its arithmetical mean roughness Ra under 0. 2 µm and with its maximum height of profile Rz under 1 μm. The machined surface roughness of A2017 varied widely. Through the visual inspection of machined surface, A2017 and A2024 showed picked surface as generated by a built-up edge. This document explains and demonstrates how to prepare your camera-ready manuscript for Trans Tech Publications. The best is to read these instructions and follow the outline of this text. The text area for your manuscript must be 17 cm wide and 25 cm high (6.7 and 9.8 inches, resp.). Do not place any text outside this area. Use good quality, white paper of approximately 21 x 29 cm or 8 x 11 inches (please do not change the document setting from A4 to letter). Your manuscript will be reduced by approximately 20% by the publisher. Please keep this in mind when designing your figures and tables etc.

Three dimensional modeling and finite element simulation of a generic end mill

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.

Experimental Characteristics of Aluminum Alloys in Dry End Milling

This paper describes the cutting characteristics of aluminum alloys in dry end milling experimentally. The tested materials are A1050, A2017, A2024, A5025 and A7075. The cutter is a flat end mill of Co-cemented High Speed Steel with the diameter of 20 mm. Through the experimental results of side milling, the following three aspects have been found out. Firstly, as to the machining error, A1050 showed smaller machining error than 15 μm in the cutting speed rage from 62.8 m/min to 251.3 m/min. Other Aluminum alloys showed greater values. Secondly, as to the cutting force, those of aluminum alloys except A2017 were generally proportional to their material hardness. The cutting forces of A1050 and A5052 were constant over the whole range of cutting speed. Thirdly, as to the machined surface roughness, A7075 showed the smallest surface roughness among the all materials with its arithmetical mean roughness Ra under 0. 2 µm and with its maximum height of profile Rz under 1 μm. The machined surface roughness of A2017 varied widely. Through the visual inspection of machined surface, A2017 and A2024 showed picked surface as generated by a built-up edge. This document explains and demonstrates how to prepare your camera-ready manuscript for Trans Tech Publications. The best is to read these instructions and follow the outline of this text. The text area for your manuscript must be 17 cm wide and 25 cm high (6.7 and 9.8 inches, resp.). Do not place any text outside this area. Use good quality, white paper of approximately 21 x 29 cm or 8 x 11 inches (please do not change the document setting from A4 to letter). Your manuscript will be reduced by approximately 20% by the publisher. Please keep this in mind when designing your figures and tables etc.

Effect of tool tilt angle on machining strip width in five-axis flat-end milling of free-form surfaces

This paper examines the effect of tool tilt angle on machining strip width in the determination of optimal tool orientation and feed direction in five-axis flat-end milling. The machining strip width is evaluated using the swept profile of the flat-end mill, avoiding both local and global gouging of the tool. An optimization problem is formulated to maximize the machining strip width over feasible gouge-free tool orientations for a constant-feed direction. By solving the optimization problem and analyzing the geometry of the machining strip width, it is shown that identifying the optimal tool tilt angle, instead of following the common practice of setting the tool tilt angle as zero, can significantly increase the machining strip width, especially for 3D free-form surface machining. The optimization has also been extended to identify the optimal feed direction that maximizes the machining strip width at a given cutter contact (CC) point. The minimum curvature direction has been considered as the optimal feed direction at a CC point by researchers. Our results indicate that although the minimum curvature direction is mostly not the optimal feed direction in free-form surface machining, the minimum curvature direction does represent a good approximation of the optimal feed direction at a CC point, in particular for a free-form surface with low-curvature relative to the tool size.