Tool Inclination Research Articles

Study on the Effect of Tool Inclination Angle in Machining Process Based on Three-Dimensional Thermo-Elastic-Plastic Model

Based on large deformation theory and virtual work principle, a coupled three-dimensional (3D) thermo-elastic-plastic finite element model (FEM) was constructed to simulate the high speed cutting process of Al7050-T7451. The mechanical properties of workpiece material under conditions of high temperature and high strain rate were defined in the model. A shear friction model was involved at the interfaces of tool-chip, tool-workpiece. Based on the model, different 3D machining FEM with different inclination angles were established, and distributions of stress, strain and temperature were achieved. Further more, the effects of inclination angle on the chip curling direction, chip flow angle, cutting force and cutting temperature were studied.

Design of the Intelligent Turning Tool System with Adjustable Tool Geometry

The tool geometry such as rake angles and cutting edge inclination angles play significant roles in determining machining performance. The task of selecting cutting tool inserts and cutting conditions is traditionally carried out on the basis of the experience of process planners with the help of data from machining handbooks and tool catalogues. This situation urges the need for development of some intelligent tooling system to reduce these inefficiencies for optimum economic and technological machining performance. A model of turning tool mechanism having the function of controllability in changing the tool inclination angle and tool approach angle is described. The mechanism is realized through the use of three specific slopes which work simultaneously to compensate the tool tip deviation due to the change of inclination angles so that the tool tip always stays at working point in space. Based on the ‘classical’ oblique cutting operation, analytically simulated prediction of the tangential cutting forces were presented with MATLAB software.

Effect of Rotary Cutting Tool Posture on Machining Performance utilizing Multi-Tasking Lathe

In this report, a driven rotary tool's machining performance on SUS304 stainless steel was examined. The rotary tool was attached to a milling axis on a multi-tasking lathe which has B axis control. It is possible to adjust the tool's circumferential speed as the tool is controlled to rotate by a milling motor. As well, the contact angle between the work-piece and cutting point are controllable as the milling axis has four degrees of freedom of movement. The objective of this study is to clarify the influence of tool posture on the rotary cutting process. It was found that the tool temperature increase and also the chip flow angle increases, when the tool inclination angle increases.

Cutting process of glass with inclined ball end mill

Cutting processes with ball end mills are discussed for machining microgrooves on glasses. A surface is finished in undeformed chip thickness less than 1 μm at the beginning and at the end of the cut during the cutter rotation. The milling process is applied to glass machining. A crack-free surface can be finished in a large axial depth of cut more than 10 μm. Because glass undergoes almost no elastic deformation, roughness on a cutting edge in glass machining has a larger influence on surface finish than that of metal machining. The rotational axis of the tool is inclined to improve the surface finish. The cutting processes are modeled to show the effect of the tool inclination on the machined surface with considering the edge roughness. The tool inclination compensates for deterioration of the surface finish induced by the edge roughness in the presented model. The improvement of the surface finish is verified in the cutting experiments with the tool inclination. The orthogonal grooves 15–20 μm deep and 150–175 μm wide, then, are machined with the crack-free surfaces to prove efficiency and surface quality in the milling process.

Influence of tool inclination on brittle fracture in glass cutting with ball end mills

Glass milling is discussed with influences of tool inclination on brittle fracture. Cutting tests are performed to observe surfaces in the up-cut and the down-cut processes with a ball end mill inclined in the feed direction of the cutter. Brittle fracture occurs in the down-cut process at high feed rates. Then the machined surfaces in cutting with the ball end mills tilted in the vertical plane with respect to the feed direction are associated with those of the up-cut and the down-cut processes. The cutting forces are also measured to discuss brittle fracture with the change of the undeformed chip thickness. The scratches on the surface finished with the tilted ball end mill are shown in an analytical model with a notched edge shape. The maximum feed rates at which brittle fracture does not occur are shown with the tool inclination in the cutting tests.

Optimum orientation of a torus milling cutter: Method to balance the transversal cutting force

In this paper, a new method for tool positioning in milling on torus cutters with round inserts is presented. A new criterion associated with balancing of the transversal cutting force is used to compute a tool orientation. The considered tool inclination is towards the back of the tool. In this case, all inserts work simultaneously and generate a continuous cutting phenomenon. Each of the inserts produces a transversal cutting force; some being positive while others are negative. A small tool axis inclination angle leads to balancing the transversal cutting force exerted on the tool and then reducing deflection and vibrations in milling operations. Firstly, this approach to the dynamic aspects relating to cutting forces in the milling process is significant for mould and die manufacturing since it allows polishing time to be reduced. In addition, as vibrations are reduced, enhanced surface quality can be obtained directly on free-form surfaces such as aeronautic fittings.

Influence of Contineous Transversal Inclination of Tool on FSW Joints

The influence of roll angle of the FSW tool rotation axis on tensile properties of joints was examined to clarify the allowance of deviation from proper tool posture for three-dimensional friction stir welding. A5083-O plates of 3 mm in thickness were butt welded by three-dimensional controlled FSW machine. Transversal inclination of the tool (roll angle of the tool) was continuously changed from 0 degrees to 10 degrees for both sides. Butt joints ruptured at base metal within the range of roll angle of the tool plus/minus 2 degrees, and ruptured at the thin part made by inclined tool shoulder entering in the range by plus/minus 7 degrees. Over the range of plus/minus 7 degrees, butt joints ruptured at elongated cavities made by tool inclination at the border of stir zone and base material.

Gouging elimination through tool lifting in tool path generation for five-axis milling based on faceted models

Five-axis milling may be performed with a constant tool-orientation or varying optimal tool-orientation. When applying a constant tool orientation, the inclination angle, the angle between the tool axis and the normal vector of a contact point (cc-point), is kept constant along the tool path. On the other hand, when applying a varying optimal tool orientation, the tool inclination angle is dynamically optimized along the tool path in order to maintain the tool to be as close as possible to the surface without gouging. In both tool orientation methods, tool lifting is one of the crucial components and involved in tool path generation, especially when it is used for gouging elimination. For the constant tool orientation, the tool is lifted immediately when the specified inclination angle causes gouging with the part surface. In the case of varying optimal tool orientation, the minimum rotation angle (inclination angle) has to be found first to avoid gouging. If the gouging still occurs (e.g. due to limited rotational axes of the milling machine), then the tool is lifted. In this paper, gouging elimination through tool lifting for five-axis milling based on a faceted model is presented. The tool is lifted based on the types of gouging. These types of gouging are described and the tool lifting procedure has been developed and implemented for gouging elimination in both tool orientation methods.

Prediction of cutting force for self-propelled rotary tool using artificial neural networks

In this paper, a cutting force model for self-propelled rotary tool (SPRT) cutting force prediction using artificial neural networks (ANN) has been introduced. The basis of this approach is to train and test the ANN model with cutting force samples of SPRT, from which their neurons relations are gradually extracted out. Then, ANN cutting force model is achieved by obtaining all weights for each layer. The inputs to the model consist of cutting velocity V, feed rate f, depth of cut a p and tool inclination angle λ, while the outputs are composed of thrust force F x , radial force F y and main cutting force F z . It significantly reduces the complexity of modeling for SPRT cutting force, and employs non-structure operator parameters more conveniently. Considering the disadvantages of back propagation (BP) such as the convergence to local minima in the error space, developments have been achieved by applying hybrid of genetic algorithm (GA) and BP algorithm hence improve the performance of the ANN model. Validity and efficiency of the model were verified through a variety of SPRT cutting samples from our experiment tested in the cutting force model. The performance of the hybrid of GA–BP cutting force model is fairly satisfactory.

Tool path generation for five-axis NC machining using adaptive space-filling curves

We present the concept of an adaptive space-filling curve for tool path planning for five-axis NC machining of sculptured surfaces. Generation of the adaptive space-filling curves requires three steps: grid construction, generation of the space-filling curve, and tool path correction. The space-filling curves, adapted to the local optimal cutting direction, produce shorter tool paths. Besides, the tool path correction stage makes it possible to eliminate the effect of sharp angular turns which characterize standard space-filling curve patterns. Our space-filling curve method is endowed with a new modification of techniques for computing the machining strip width along with a modified formula for the minimum tool inclination angle to avoid gouging. Finally, we show that the adaptive space-filling curves are more efficient compared with the traditional iso-parametric scheme. The numerical experiments are complemented by real machining as well as by test simulations on Unigraphics 18.

A Geometrical Simulation System of Ball End Finish Milling Process and Its Application for the Prediction of Surface Micro Features

Finish milling with a ball end mill is a key process in manufacturing high-precision and complex workpieces, such as dies and molds. Because of the complexity of the milling process, it is difficult to evaluate the microcharacteristics of machined surfaces real time, which necessitates the simulation of the process. In this area, the existing related simulation researches mainly focus on scallop height evaluation, but few have presented a whole picture of the microcharacteristics of milled surfaces. This paper develops a comprehensive simulation system based on a Z-map model for predicting surface topographic features and roughness formed in the finish milling process and studies the effect of machining parameters. The adoption of the discretization concept of the tool’s cutting motion makes it possible to dynamically track the cutting tool-workpiece interaction with the tool movement and to describe the cutting edges-workpiece discrete cutting interaction more realistically and, therefore, the microcharacteristics of the machined surfaces more accurately. Also, the effects of the cutting tool run-out and wear are incorporated into the developed model through modifying the tool center motion and the cutting-edge shape, respectively. As a fundamental study, the tool-swept envelope has been simulated. The developed simulation system is applied to thoroughly study the surface features formed by the 2.5-axis finish milling process. The application for general three-axis machining is discussed. Additionally, this paper studies the effect of the tool inclination, which is the most common characteristic in 3+2- or five-axis milling processes, on the machined surface features. Experiments are carried out to study the milling process and to verify the simulation results. The difference between the simulated and experimental results is discussed, and the reason behind the difference is explored.

2607 硬脆材料のエンドミル加工における切削特性(S71-2 高速・高精度加工とエコマシニング(2),S71 高速・高精度加工とエコマシニング)

This paper discusses machining characteristics in the milling processes of glass with the feed direction. The machined surfaces are observed to determine the maximum feed rate where brittle fracture does not occur. It is shown that the feed direction has a large influence on the machined surface. Milling in a down-cut manner leaves brittle cracks on the machined surface. When the milling tool is fed against the inclination of the milling tool, the effect of contact area on the flank face of the edge with workpiece increases to leave brittle cracks. The critical feed rates are determined in the cutting tests with changing the feed direction. Crack free surfaces are made at a high feed rate in an up-cut manner.

Three-dimensional thermo–elastic–plastic coupled FEM simulations for metal oblique cutting processes

Metal oblique cutting processes are modelled by the three-dimensional finite element method (FEM) with thermo-elastic–plastic coupling. The model refers to some key aspects, including thermo-mechanical coupling effects for material flow in cutting and the rigid material model with thermal effects for tools. At the tool–chip and tool–workpiece interfaces, a shear friction model is involved. Authors simulated the machining process of the workpiece, chip, and tool from the incipient state to steady state. The detailed calculated results are presented, including the chip's geometric shape and its evolution, the stress, strain, and temperature distribution in the workpiece and chip, as well as the variations of cutting forces at four different tool inclination angles.

Mechanics of boring processes—Part I

Mechanics of boring operations are presented in the paper. The distribution of chip thickness along the cutting edge is modeled as a function of tool inclination angle, nose radius, depth of cut and feed rate. The cutting mechanics of the process is modeled using both mechanistic and orthogonal to oblique cutting transformation approaches. The forces are separated into tangential and friction directions. The friction force is further projected into the radial and feed directions. The cutting forces are correlated to chip area using mechanistic cutting force coefficients which are expressed as a function of chip-tool edge contact length, chip area and cutting speed. For tools which have uniform rake face, the cutting coefficients are predicted using shear stress, shear angle and friction coefficient of the material. Both approaches are experimentally verified and the cutting forces in three Cartesian directions are predicted satisfactorily. The mechanics model presented in this paper is used in predicting the cutting forces generated by inserted boring heads with runouts and presented in Part II of the article [1].

Development of a Five-axis Milling Tool Path Generation Algorithm based on Faceted Models

This paper describes the development of a 5-axis milling tool path generation algorithm based on faceted or tessellated models. In a first step, the developed algorithm optimises the tool inclination angle for maximal material removal rate in each cutter contact point. This is obtained by matching the tool profile of a flat end cutter with a temporary spline representing the curvature of the part surface in the tool contact point. In a second step, the elimination of gouging between the tool and the surface and a smooth behaviour of the tool inclination angle along the tool path is obtained by a combination of tool inclination angle adaptation and tool lifting along the normal vector. Finally, the paper describes some experimental results.

A study of oblique cutting for different low cutting speeds

In this paper, the finite deformation theory and an updated Lagrangian formulation (ULF) were used to describe the oblique cutting process. Either the tool geometrical location condition or the strain energy density constant was combined with the twin node processing method to be adopted as the chip separation criterion. An equation for 3D tool face geometrical limitation was established to inspect and correct the relation between the chip node and tool face. In addition, a 3D finite difference equation for heat transfer was derived. Based on this approach, a coupled thermo-elastic–plastic large deformation finite element model for oblique cutting was established, for which mild steel was used as the workpiece material and P20 as the tool. Under the different cutting speed conditions, the chip deformation process and the effect of different cutting speeds on the chip flow angle, cutting force and specific cutting energy were first explored. Then, the effect of different cutting speeds on the separation location of the chip node and the geometrical phenomenon at the instant of chip separation from the tool face, and on both stress and temperature distributions on the chip surface, were analyzed. Finally, the effect of different cutting speeds on the residual stress, displacement and temperature distributions on the machined surface after cutting were investigated to understand the relation between the cutting speeds and the integrity of the machined surface. During the chip deformation process, the simulated chip flow angles under the different low cutting speed conditions approximately matched with the designated tool inclination angle, which complied with the geometrical requirements of Stabler’s criterion. Further, the simulated specific cutting energy under a given low cutting speed condition was compared with the experimental data, the result of which was within an acceptable range, and the trend of specific cutting energies under the different low cutting speed conditions were the same as the experimental trends. It is obvious from the above findings that the model presented in this paper is consistent with the geometrical and mechanics requirements, which verifies that the proposed model is acceptable.

Elastic-plastic finite element analysis for oblique cutting with a discontinuous chip of 6-4 brass

If the workpiece material experiences tremendous strain during the chip formation process or brittle material undergoes fracture in the primary deformation zone when the chip is only partly formed, the segmented chip formed under the above conditions is called a discontinuous chip. With the introduction of the tool inclination angle geometry, an elastic-plastic finite element model is developed for oblique cutting of discontinuous chip. The tool is P20 while the workpiece is made of 6-4 brass. The initial crack location, the direction of crack growth and variations of discrete chips are examined under the condition of a low cutting speed. These predictions are made possible by application of the strain energy density theory. The initial crack was formed in the (d W/d V)maxmin region (i.e. the maximum region among many of the strain energy density minima) of the chip surface and grew progressively along the stationary values of the strain energy density function. The direction of crack growth was based on the maximum strain energy density curve along the surface. The fracture process on the other chip layers was identical with that on the chip surface and occurred in sequence until it reached the chip free surface. The plastic deformation and friction result in a high equivalent stress on the chip surface above the tool tip, especially at the place of crack formation. As more residual stress is present after cutting, degradation of the workpiece prevails and should be accounted for.

A new tooling mechanism for CNC lathes

The paper describes details of the development of a new CNC lathe tooling mechanism with on-line adjustable cutting edge inclination angle, which is one of the major tool geometry parameters in machining operations. The mechanism is based on the combination of (i) three linkages which adjust the tool inclination angle automatically and continuously, (ii) three curved slots which work simultaneously to compensate the tooltip deviations accurately, and (iii) an input link driven by a linear stepping motor that converts the linear stroke into tool angle rotation. The prototype developed provides a new tooling mechanism for the prospective open architecture-based CNC machines.

Application of a neural network for improving the quality of five-axis machining

As many operating parameters are involved in five-axis machining and significantly affect the machining results, use of either an analytical method or an experimental method can only solve the problem to a degree. Therefore, a concept for developing a database system using a neural network as the inference mechanism for the purpose of improving the quality of five-axis machining was addressed in this research. A database system was constructed on the basis of the VERICUT cutting simulation and experimental data from previous literature. The simulation data were put into an intelligent database for automatic generation of the suitable tool inclination angle for each cutting point on the machined surface. The tool inclination angle was the dominating factor for improving the surface quality in five-axis machining. The inclination angle was further entered into a post-processor to modify the cutter location file and to generate the numerical control (NC) program file for practical machining. The input data used in the database required for this system are basic operating parameters, quality requirements and the geometry of the designed sculptured surface. In this research, an intelligent database system for ball mills was successfully established for five-axis machining.

Fundamental modeling for oblique cutting by thermo-elastic-plastic FEM

In this paper, the finite deformation theory and updated Lagrangian formulation were used to describe the oblique cutting process. Either the tool geometrical location condition or the strain energy density constant was combined with the twin node processing method to act as the chip separation criterion. An equation of three-dimensional tool face geometrical limitation was first established to inspect and correct the relation between the chip node and the tool face. And, a three-dimensional finite-difference heat transfer equation was derived. Based on this approach, tool advancement was achieved in displacement increment step by step from the initial tool contact with the workpiece till the formation of steady cutting force. In this case, a large deformation thermo-elastic–plastic finite element model for oblique cutting was established. The mild steel was used as the workpiece, the tool was P20 and the cutting speed was 274.8 mm/s in this article. The chip deformation process and temperature effect on the strain energy density, chip flow angle, cutting force and specific cutting energy were studied first. Finally, the integrity on machined workpiece surface was explored from the variation of residual stresses and temperature distribution on it after cutting. During the chip deformation process, the chip flow angle obtained by this simulation result was approximately equal to the tool inclination angle, which confirmed with the geometrical requirement of Stabler’s criterion. Besides, the simulated specific cutting energy was compared with the experimental specific cutting energy value, the result of which was within acceptable range. It is obvious from the above findings that the model presented in this paper is consistent with the geometrical and mechanical requirements, which verifies the proposed model is acceptable.