Tool Radius Research Articles

Experimental investigation on influence of engagement angle and tool geometry on plunge milling

Taking advantage of the superior cutter axial stiffness, plunge milling provides a higher material removal rate in rough milling for components with deep cavities. Tool wear depending on cutting parameters of radial cutting width, axial cutting depth, step interval, feedrate, and spindle speed has been studied by several researchers. For a more comprehensive understanding of the wear mechanism, this study investigates the influences of tool engagement angle and tool geometry on tool wear based on multiple sets of machining tests. The development of tool wear during plunge milling is monitored. Results show that tool wear of insert with large engagement angle mainly exists on minor edge, which is caused by increased tool deflection. When the radial distance equals to tool radius, optimal engagement angle can be achieved while considering both tool life and machining efficiency. The experimental results show that tool life of insert with rake angle of 22° is 6.5% higher than rake angle of 15°. Smaller corner radius has positive influences on tool life improvement. Surprisingly, tool life of insert without cutting edge chamfer is 3.6 times than insert with cutting edge chamfer. The best tool geometric parameters of plunge insert can then be identified among a variety of inserts. This work is useful for cutting tool producers and manufacturers to optimize tool geometry and machining parameters.

The influence of tool-path strategies and cutting parameters on cutting forces, tool wear and surface quality in finish milling of Aluminium 7075 curved surface

The curved parts of Aluminium 7075 alloy are extensively used in automotive and aircraft structures. In curved surface milling, the tool-workpiece contact changes continuously varying effective tool radius, active cutting speed and cutting forces all the time during machining. These variations lead to a change in metal removal mechanism from shearing to ploughing and vice-versa that determines the final product quality. In the present work, the tool-path strategies are investigated in the first phase wherein 3D offset found to be the best finishing strategy. Latter, the parametric analysis is performed by conducting the statistically designed experiments with 3D offset strategy to highlight the input-output correlations. The Khattree–Naik’s equation/plot is used to analyse the multivariate data in milling and accordingly the better input parameters are selected. A ball-end tool imparting the entire tool face and cutting the surface from all-around with consistent cutting conditions enhances the tool life with a better finish. The results show that along with the magnitude of the force, a time lag (Δt) and nature of force profile are equally significant in determining the tool wear and surface roughness.

Error control of non-equal diameter machining of globoidal cam profile based on adaptive method

In order to effectively tackle the machining error of globoidal cam profile, an adaptive compensation method of tool position error was proposed. The actual profile equation of the non-equal diameter machining of globoidal cam was constructed through the space meshing principle and the rotation transformation tensor method. To minimize the maximum deviation of the actual tool axis was regarded as an objective, and then the adaptive compensation of the tool position was performed through searching the optimal tool offset amount and direction during the machining process. When tool radius compensation amount $$\Delta_{r}$$ was the value optimized by the adaptive method, the theoretical maximum value of the normal error of globoidal cam was closest to the simulation result. The validity of the error control technique of tool position of the adaptive method was verified by the simulation results and calculation. Consequently, the machining accuracy of the globoidal cam in non-equal diameter machining is improved greatly.

Research on Parameter Optimization of Micro-Milling Al7075 Based on Edge-Size-Effect.

In the process of micro-milling, the appearance of the edge-size-effect of micro-milling tools cannot be ignored when the cutting parameters are smaller than the cutting edge arc radius (r0) of the micro-milling tool or close to it, and it could easily lead to low cutting efficiency and poor surface quality of the micro-slot. Through micro-milling experiments on Al7075-T6 materials, the change of milling force in the plough zone and shear zone during micro-milling was studied, and the minimum cutting thickness (hmin) range was determined to be 0.2r0–0.4r0 based on r0 of the micro-milling tool. Subsequently, the effect of fz/r0 (fz denotes feed rate per tooth) on the top burr formation of the micro-slot, the surface roughness (Ra) of the micro-slot bottom, and the milling force was studied, and a size-effect band of micro milling was established to determine the strong size-effect zone, transition size-effect zone, and the weak size-effect zone. Finally, two different fz/r0 in the strong size-effect zone and the weak size-effect zone are compared, which proves that the main purpose of the cutting parameters optimization of micro-milling is to avoid cutting parameters locating in the strong edge-size-effect zone. The above conclusions provide a theoretical basis for the selection of micro-milling cutting parameters, and an important reference in improving the surface quality of micro-milling.

Diffraction efficiency evaluation for diamond turning of harmonic diffractive optical elements.

Single point diamond turning is a commonly used method for manufacturing harmonic diffractive optical elements (HDOEs). Diffraction efficiency of HDOEs is sensitive to surface-relief profile errors, and a half-round tool can reduce the profile error obviously. Furthermore, the diamond tools also create surface roughness errors. The two errors will produce shadowing and scattering effects. In this paper, the two kinds of errors, especially the surface roughness, are described accurately. A mathematical model is proposed to reveal the relationship among diffraction efficiency, cutting tool radius, feed rate, microstructure zone period widths, and the refractive index of the substrate material and balance the influence of shadowing and scattering effects. The simulation results show that the model can guide the acquisition of high-precision surface topography and high diffraction efficiency, which improves the imaging quality of the optical system.

Study of Parameters during Aluminum Cutting with Finite Element Method

The authors analyzed the force and stress values in the simplified cutting model and compared the results with the literature. For the study a 2D model was created in DEFORM 2D finite element software, using the temperature depended multilinear flow stress material model. The model was compiled according to the literatures. In this analysis were the effects of relief angel, tool angle, tool radius, depth of cut, and the cutting velocity examined. The values of forces, strain, temperature, stress and shear plane angle were examined at different values of geometry and machining parameters. For these examinations were used 28 parameter combinations. As a result of the study, the results for forces are similar to the results of examined literature at every parameter. The force results were checked on a simple tool geometry.

Determination of Ceramic Cutting Tool Performance on Machining of Steel (PMD23) Produced by Powder

This study aimed to determine optimum cutting parameters for recovering the best surface roughness during PMD 23 powder metal machining with ceramic sharp cutting tool at CNC turning center. Experiments for this aim were carried out on 27 samples in 80 mm diameter and 200 mm length prepared at turning center by application of cutting parameters determined with Taguchi method. Three different cutting speeds (200, 350, 500 m/min.), three different feed rates (0,1–0,2–0,3 mm/rev) and three different tool nose radius (0,4-0,8-1,2 mm) were used and depth of cut was applied stable as 0,8 mm in the experiments. Later, surface roughness of experiment sample and the roughness change was evaluated with respect to cutting speed, feed rate and tool nose radius. Variant analysis (ANOVA) were used to investigate characteristics of the processes. As a result of the experimental study, it was found out that feed rate and tool radius of cutting parameters had an effect on surface roughness, but the effect of cutting speed was not significant.

An investigation of cutting parameters effect on sound level, surface roughness, and power consumption during machining of hardened AISI 4140

In recent years, the necessity for energy in the manufacturing industry has become an important problem because fossil fuel reserves are decreasing in order to produce energy. Therefore, the efficient use of energy has become an important research topic. In this study, energy efficiency is investigated in detail for sustainable life and manufacturing. AISI 4140 material with high hardness of 50 HRC hardness has been applied cryogenic process to improve mechanical and machinability properties. In this experiment study, the effects of feed rate (0.04, 0.08, 0.12 mm/rev), cutting speed (140, 160, 180 m/min), depth of cut (0.05, 0.10, 0.15 mm) and tool radius (0.4, 0.8) on energy consumption, surface roughness and sound intensity were investigated. Then, a new mathematical model with high accuracy was developed. Total power consumption was calculated by considering the instantaneous current value and machining time. As a result, it is found that good surface quality obtained when the feed rate is low, and the tool radius is high and the machining time is shortened, the energy consumption is reduced due to the increase in cutting speed, depth of cut and feed rate. Also, it is found that the tool radius has a limited effect on energy consumption, but low feed value increases energy consumption.

Investigations into edge radius and point angle on energy consumption during micro drilling of titanium alloy

In aircraft industries, micro holes need to be provided on gas turbine blade to improve cooling and efficiency of aero engines. Generating micro features in gas turbine blade materials are tedious task due to enhanced thermal, mechanical and metallurgical properties of aero engine alloy. So in this paper a finite element simulation is developed to comprehend the process mechanics of micro drilling process and study the influence of point angle and edge radius on energy consumption. The model has been developed by considering size effect, point angle and drill tool edge radius. The modified JC model is used to delineate the flow stress during micro drilling process. The simulations are done by varying drilling speed, feed rate, point angles and edge radius of the micro drill tool. The results obtained are calibrated with various friction shear factors and finally verified with experimental outcome in the literature. Thrust force is observed to decrease when the drill speed increases because of low thermal conductivity of an aero engine alloy generate thermal softening more predominant than strain hardening in the micro drill zone. When the point angle of micro drill decreases, there is less energy consumed for the generation of hole. Higher edge radius tool results in variation of dimension and form of hole, whereas for lower edge radius comparable to uncut chip thickness result in nonlinear increase in power consumption. The average thrust force prediction error is 15.17%.

Planar tool radius compensation for CNC systems based on NURBS interpolation

This paper introduces the realization of a tool radius compensation algorithm for NURBS trajectory. First, a single-segment NURBS trajectory tool radius compensation algorithm is developed. Different from the straight line and arc trajectory, the self-intersection phenomenon is prone to happen when calculating a single NURBS tool center trajectory, and the self-intersection will cause the overcut of workpiece. To avoid this situation, the algorithm introduced in this paper can detect whether the NURBS tool center track has caused overcut, and deal with the self-processing. Second, the tool radius compensation algorithm with multi-segment NURBS trajectory is implemented. The focus of this part is the tool radius compensation of the trajectory transfer, and the trajectory transfer is divided into two types: the extension type and the shortened type. For the shortened type transfer, cross-processing is needed to avoid the overcut of workpiece at the transfer. When calculating the tool radius compensation of the shortened type, we not only need to find the intersection of the tool center trajectory of two adjacent NURBS curves, but also need to select the intersection we need when a number of intersections exist. For the extension type transfer, in order to ensure the continuity of the tool center trajectory, we need to extend the tool center trajectory or add arc-segment at the transfer. The proposed algorithm can automatically decide where to extend the tool center trajectory or add arc-segment to achieve the best efficiency. Finally, the algorithm can output the calculated NURBS tool center trajectory in the form of linear segment interpolation G code or NURBS interpolation G code according to the processing needs. Simulations on VERICUT and experiments on three-axis CNC machine tool shows the effectiveness and validation of the tool path compensation algorithm.

Cutting Force Simulation in Milling of Tapered Wall with Barrel End Mill

The machinings of aircraft parts and die molds highly require fine surfaces at high production rates in terms of reliability. Barrel end mills having excessively large curvatures on the side cutting edges have recently been applied to finishing of tapered workpiece walls with respect to the cutter rotation axes. Because a large curvature of the cutting edge reduces the cusp height, the tools finish surfaces with small cusp heights in large axial pick feeds. However, in milling with the barrel tool, the cutting force loading in the direction of tool radius increases with the cutting area along the edge. The machining accuracy is deteriorated by tool deflection due to a large cutting force. The wave form is also left on a surface with the tool vibration. Therefore, the cutting parameters should be determined with controlling the cutting force and its direction in milling with the barrel tool. The paper discusses the cutting forces in milling of tapered walls with a barrel end mill in the cutting simulation. The cutting forces are analyzed in the chip flow models interpreted as a piling up of orthogonal cuttings. The shear angle, the shear stress and the friction angle in the cutting model are discussed with the chip flow model. The cutting force characteristics are discussed for the taper angle of the workpiece.

Effect of Process Parameters on Plastic Formability and Microstructures of Magnesium Alloy in Single Point Incremental Forming

In this paper, using a combination of simulated and experimental results and macroscopic and microscopic observations, we explain the effect of three process parameters: the forming temperature, forming tool radius, and the forming feed rate on the plastic formability of single point incremental forming of AZ31 magnesium alloy sheet in single point incremental forming from macroscopic and microscopic perspectives. The results show that the forming temperature and the tool-head radius strongly affect the macroscale experiment and the microstructure of AZ31 magnesium alloy sheet, whereas the effect of the feed rate is small. At a forming temperature of 250 °C, tool-head radius of 5 mm, and a feed rate of 0.7 mm, the magnesium alloy sheet exhibits a relatively good forming state, the thickness variation of the formed part is uniform, which is favorable for achieving uniform sheet forming, reducing stress concentration, and reducing the possibility of cracking. Under these conditions, the grain size of the magnesium alloy is relatively uniform; compared with the grain size in the microstructure of 6061 aluminum alloy, the grain size of the magnesium alloy is smaller.

Prospects for CNC Machine Tools

The main global trends in the production of high-technology CNC systems are identified. Topics analyzed include system architecture; the use of high-speed industrial networks based on fieldbus technologies; the potential of multiple-channel and multiple-axis machining; spline interpolation in the machining of complex contours and free surfaces; and five-coordinate machining with 3D correction of the tool radius and length. In the light of global trends, decisions are made regarding the development of the AksiOMA Kontrol CNC system.

Investigation of machining and wear performance of various diamond micro-grinding tools

The wear of micro-grinding tools less than 1 mm in diameter is crucial for achieving acceptable surface quality and accurate dimension of the workpiece. To control wear behavior of the micro-grinding tools, an investigation through experiments was conducted on the machining and wear performance of various (D-shaped PCD, CVD, electroless plated, and electroplated) diamond micro-grinding tools on monocrystalline silicon workpiece in this study. The experiments showed that a CVD diamond micro-grinding tool had excellent machining performance, but its relatively large diameter limited its application range. An electroplated diamond micro-grinding tool had a good machining performance but displayed severe wear. To comprehensively understand its wear mechanism, a series of grinding experiments were further done. Its mechanism was analyzed through investigating the tool and machining process parameters. In order to accurately evaluate tool wear, the ratio of tool radius loss to average grain diameter (δ) and the ratio of the lost grain number to the total grain number (η) were proposed. The δ-ratio and η-ratio related to the wear limit of 600 mesh size micro-grinding tools having a diameter of 0.5 mm were 0.16–0.18 and 11.50–13.88%, respectively.

Modelling of the effects of process parameters on energy consumption for incremental sheet forming process

Incremental sheet forming (ISF), as a flexible rapid prototyping technology, has great potential in the production of small-volume complex sheet parts. The research on the energy consumption of ISF is beneficial to the determination of the most energy-saving process parameters. First, the total power of the machine tool is broken down into standby power, feed axis power and sheet forming power, which is also theoretically analyzed, respectively. Apart from the modeling of the standby power and feed axis power, a theoretical mechanism model for sheet forming power during the ISF process is established based on the contact area and the flow condition of sheet. Then, experiments at the standby state, idle feed state, air forming state and actual processing state are carried out respectively to determine the essential coefficients of the theoretical model. In addition, the processing power prediction model in ISF is obtained and the prediction accuracy is verified through experiments. The results confirmed that the power prediction error of the processing power is below 5%. Moreover, the effects of process parameters (forming tool radius, step down, sheet thickness, feed rate) on processing power, power efficiency, processing energy and energy efficiency are comprehensively analyzed. Finally, the optimal combination of process parameters for the lowest energy consumption is obtained.

Effects of Tool Edge Geometry on Chip Segmentation and Exit Burr: A Finite Element Approach

The effects of different tool edge geometries (hone and chamfer (T-land)) on quantitative measurement of end (exit) burr and chip segmentation (frequency and degree) in machining of AA2024-T351 are presented in this work. The finite element (FE) approach is adopted to perform cutting simulations for various combinations of cutting speed, feed, and tool edge geometries. Results show an increasing trend in degree of chip segmentation and end burr as hone edge tool radius or chamfer tool geometry macro parameters concerning chamfer length and chamfer angle increase. Conversely, the least effects for chip segmentation frequency have been figured out. Statistical optimization techniques, such as response surface methodology, Taguchi’s design of experiment, and analysis of variance (ANOVA), are applied to present predictive models, figure out optimum cutting parameters, and their significance and relative contributions to results of end burr and chip segmentation. Various numerical findings are successfully compared with experimental data. The ultimate goal is to help optimize tool edge design and select optimum cutting parameters for improved productivity.

Research on Machining Error of Globoidal Cam Profile Based on Adaptive Algorithm

In order to effectively control the machining error of globoidal cam profile, an adaptive tool position error compensation algorithm is proposed. According to the space meshing principle and the rotation transformation tensor method, the actual working profile equation of the non-equalization diameter machining globoidal cam is established. The objective is to minimize the maximum deviation of the actual tool axis, and search the optimal tool offset and direction during machining to achieve adaptive compensation of the tool position. When the tool radius compensation amount Δr=3mm, the theoretical value of the maximum normal error of the cam profile is close to the simulation value. The result validates the effectiveness of the tool position control technique of the adaptive algorithm for machining error compensation, thereby the machining accuracy of the globoidal cam is improved greatly.

Improved bendability characterization of UHSS sheets

Bendability characterization of UHSS sheets is often limited by punch-sheet-liftoff during standardized bending tests. This phenomenon is characterized by a smaller radius on the bent sheet than the desired tool radius and might lead to a misinterpretation of the admissible bending radii from such tests. An alternative bending setup is proposed suppressing punch-sheet-liftoff. The proposed setup aims at imitating bending in multistage stamping processes and to some extent also roll forming. The target bending radius to sheet thickness ratios of the investigated UHSS sheets were chosen to be 2.0. Alternative tool geometries are investigated as well. Short segments of an Euler spiral between the tool parts exhibiting the target curvature and the linear neighbor regions are used to avoid triggering strain localizations at these curvature discontinuities, further decreasing the admissible bending ratios. Finite element simulations of the proposed bending test were conducted in order to identify the optimal tool shape. All results were compared to corresponding results from standardized bending tests of the respective UHSS sheets. The proposed setup succeeded in suppressing punch-sheet-liftoff for the desired bending ratios and was able to provide smaller bending ratios for the investigated UHSS sheets as compared to the ratios from standardized bending tests.

Modeling the effects of Undeformed Chip Volume (UCV) on residual stresses during the milling of curved thin-walled parts

With the increasingly popularized curved thin-walled parts, the control of curved surface residual stress in machining has become more and more demanding. However, it remains to be a major challenge to predict and control curved surface residual stress in the present aerospace research areas. Amidst this backdrop, this paper introduces a residual stress volume model to evaluate the effects of sequential cuts for the generated surface and subsurface residual stresses. Additionally, based on the proposed modeling and calculated results, quantified method is used for superposition of residual stress under different machining conditions. The superposition rates in feed, vertical feed and depth of cut directions are about 10%, 11% and 7%, respectively. In addition, this paper presents a newly constructed mathematical model between the curved surface maximum tensile residual stress and the Undeformed Chip Volume (UCV) (fz, R, ap and ae) of the ball end milling cutter. Through polynomial fitting for the proposed mathematical model, the influence coefficients α and β can be obtained, which act as the influence factors of machining parameters on residual stress generation. The values of α vary from 0.0018 to 0.0087, while the values of β vary from −3.99 to 0.72. That means that the depth of cut and tool radius can exert the greatest influence on the curved surface maximum tensile residual stress. Finally, with larger tool radius and smaller depth of cut, an experiment of machining curved thin-walled part proves that curved surface residual stress and deformation can be effectively reduced.

EFFECT OF SPRINGBACK IN DP980 ADVANCED HIGH STRENGTH STEEL ON PRODUCT PRECISION IN BENDING PROCESS

Springback is a common phenomenon in sheet metal forming, in which the material undergoes an elastic recovery as applied loads are removed. Springback causes the forming shape to deviate from the intended design geometry. This phenomenon, which can be influenced by several factors, effects on both bending angle and bending curvature. The aim of this study is to determine the influence of different tool radius and the gap between punch and die on springback in bending of DP980 Advanced High-Strength Steels (AHSS) sheet. Experimental studies are combined with FEM method in commercial ABAQUS software to determine the bending angle after springback. To predict springback in bending process, the material properties are defined by Ludwik - Hollomon law, combined with the Hill’48 criterion. Experimental results are in good agreement with numerical simulations in case of bending in the rolling direction.