Ball-end Milling Research Articles

Surface texture topography evaluation and classification by considering the tool posture changes in five-axis milling

Surface texture topography affects the performance of industrial parts, such as precision and service life. Different tool postures may lead to various texture topographies in five-axis milling. In this paper, surface texture topography quality and texture trend evaluation indexes are proposed considering the influence of tool posture in five-axis milling. Based on the evaluation, the ranges of tool posture angles corresponding to surface texture topographies of different characteristic are obtained through surface texture topographies classification. The result can provide reference for singularity avoidance in path planning and machining error compensation in five-axis milling. The influence of tool posture change on the surface texture quality could be avoided while adjusting the tool posture angle in the determined range. Firstly, the general tool cutting edge point expression with the typical structure parameters of the end mills is proposed. The general digital model of surface texture topography is established with the improvement of the unit time calculation and computing vertex judgment in simulation. Secondly, several evaluation indexes are proposed to represent the quality and the overall trend of the surface texture topography with digital extraction of indexes realized on the surface digital model. On this basis, the classification of the surface texture topographies and the determination of the range of tool posture angle for each class of textures are proposed. Thirdly, the evaluation and classification of the ball-end milling plane texture topographies are carried out, which divide the texture topographies into zero-inclination angle textures and non-zero inclination angle textures. The surface textures are further divided to detailed five categories with the tool posture angle range determined. Different tool posture angles of the same class are used to generate a texture topography for the comparison to verify the evaluation indexes and the classification result. Finally, the plane cutting orthogonal experiments are carried out. The general surface digital model is verified by the comparison in surface texture characteristic of different types of mills between digital model and machined surface. Based on the ball-end milling plane classification result, the machined surface textures and extracted indexes are compared to verify the effectiveness of the proposed evaluation indexes and the classification result. The fillet-end milling surface textures are further classified and verified based on the method above. In addition, the spherical surface textures of ball-end milling are carried out for further verification.

Design and milling performance investigation of a new PCBN multi-edge ball milling and grinding composite tool

The structure and material of micro tools have a significant impact on their machining performance. To improving the machining performance and wear resistance of micro milling tools, a new PCBN multi-edge ball milling and grinding composite tool (ME-BMGT) with multi-edge and spherical flank is proposed. The micro milling experiment results show that, compared with the cemented carbide double-edged ball-end milling tool (OMBMT), the micro groove morphology machined by the ME-BMGT has grinding texture characteristics, the micro groove surface quality is better, and the burr height is smaller. The wear morphology shows that the wear form of ME-BMGT is adhesive wear, while the wear form of OMBMT is cutting edge fracture and adhesive wear. The ME-BMGT provides superior wear resistance.

A Numerical Analysis for Ball End Milling Due to Coupling Effects of a Flexible Rotor-Bearing System Using GPEM

In this paper, the tool-tip responses for ball end milling, due to the coupling effects of a flexible rotor-bearing system, are investigated numerically. The milling machine tool spindle is modelled as the flexible rotor-bearing system. The critical speeds, natural modes, and unbalance responses of the system are calculated by applying the generalized polynomial expansion method. This generalized polynomial expansion method expresses the displacement as a series formed by the product of generalized coordinates and axial coordinate polynomials. According to the dynamic cutting force obtained by some scholars in the past, combined with the characteristics of the flexible rotor, the dynamic response of the tool-tip for ball end milling is numerically analyzed. The responses, including time histories, orbits, and FFT diagrams, are plotted to analyze the dynamic behaviors of the tool-tip. The coupling effects of the flexible rotor-bearing system on the system for ball end milling are first studied using the generalized polynomial expansion method. Unlike previous studies, the natural frequency varies with spindle speed and which of the different modes are included in the tool-tip response depends mainly on the spindle speed. Thanks to the gyroscopic effect, the critical speeds and responses of tool-tips can be discussed with respect to various spindle speed and tool flutes. The natural modes are accurately determined, and will excite critical speeds for certain modes, including forward and backward modes, thereby significantly affecting tool-tip response. In addition, the cutting force component associated with the tool-tip response affects the rotor-bearing system parameters, complicating the issue. Milling at higher spindle speed (2160–19,950 rpm), an important new result is found that the tool-tip oscillates with the cutting-force frequency, accompanied by a longer period vibration of the first backward mode of the rotor-bearing system. It can also be seen from the frequency spectrum analysis that, as the spindle speed increases, the peak amplitude of the first backward mode becomes larger. Milling at lower spindle speed (960, 1320 rpm), the in-plane vibration trajectory of the tool-tip gradually expands outwards clockwise around the origin until a stable loop is reached. This is because only the first backward mode of the rotor-bearing system is excited. Considering the coupling effect of the rotor-bearing system to perform the vibration analysis of the milling machine system, the parameters of the system can be designed or the spindle speed can be selected to avoid severe vibration during machining.

Study on the milling performance of ball-end milling cutter under the combined action of micro-texture of rake and flank face

PurposeIt was verified that the micro-texture in the front and back of the tool at the same time had a positive effect on improving the milling behavior and surface quality of the tool. The purpose of this study is to explore the rationality of simultaneous placement of micro-textures on the front and rear surfaces of ball-end milling cutters, analyze the influence of micro-texture parameters on tool milling behavior and workpiece surface quality, reveal its internal mechanism, and obtain the best micro-texture parameters by optimization.Design/methodology/approachFirst, the mechanism of micro-texture is studied based on the energy loss model. Second, the orthogonal experiment is designed to analyze the influence of micro-texture parameters on tool milling behavior and reveal its mechanism by combining simulation technology and cutting experiment. Finally, the parameters are optimized based on the artificial bee colony algorithm.FindingsThe results show that the simultaneous placement of micro-texture on the rake face and flank face of the tool has a positive effect on improving the milling behavior and surface quality of the tool. Taking milling force, tool wear and surface roughness as the evaluation criteria, the optimal parameter combination is obtained: the rake face micro-texture diameter is 50 µm, the distance from the micro-texture is 200 µm and the distance from the cutting edge is 110 µm; the diameter of the micro-textured flank is 40 µm, the distance from the micro-texture is 170 µm and the distance from the cutting edge is 130 µm.Originality/valueTaking milling force, tool wear and surface roughness as the evaluation criteria, the optimal parameter combination is obtained: the rake face micro-texture diameter is 50 µm, the distance from the micro-texture is 200 µm and the distance from the cutting edge is 110 µm; the diameter of the micro-textured flank is 40 µm, the distance from the micro-texture is 170 µm and the distance from the cutting edge is 130 µm, which provides theoretical support for the further study of the micro-textured tool.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2023-0022/

Effect of ball end mills errors on cutting forces

Effect of ball end mills errors on cutting forces

Study of quadrifoliate tool-setting method for diamond milling of microlens array

Rotary milling was used in this study to fabricate a microlens array (MLA) with diamond ball-end milling tools. Tool-setting error determines the positional accuracy of each lenslet during rotary milling. The position error of a single lenslet overlaps with adjacent lenslets, creating an adjacency defect in the MLA; the tool-setting error can be directly evaluated according to the MLA adjacency defect. We developed a quadrifoliate tool-setting method for machining a specific MLA, where tool-setting error can be calculated and corrected according to the adjacency ridge. The effects of tool-setting error on the type, length, and direction of the ridge were investigated. The proposed method was found to reduce setting error of the diamond ball-end milling tool to less than 1 μm. An MLA with low position error can be fabricated by rotary milling after applying the proposed quadrifoliate tool-setting method.

Generation of Textured Surfaces by Vibration-Assisted Ball-End Milling

Textured surfaces have been widely applied in many fields due to their excellent functional performances. Although several micro-scale surface texturing techniques have been used to fabricate surface textures, most are either very expensive, have material limitations, or lack flexibility. In this study, a novel textured surface generation method using vibration-assisted ball-end milling with a non-resonant vibrator is proposed. Firstly, the configuration of the vibration-assisted ball-end milling system is introduced. Then, the trajectories of the cutting edges are modeled and analyzed. Furthermore, an analysis of a non-resonant vibrator is conducted. Finally, surface texture machining experiments are conducted, and the feasibility of the proposed vibration-assisted ball-end milling method for surface texture fabrication is verified.

Study on the Ball-End Milling Cutter Design and the Performance of Milling SiCp/Al

The ball-end milling cutter is widely used in the machining of various complex curved surfaces and grooves. In order to meet the machining requirements of SiCp/Al, the mathematical model of ball end milling cutter, grinding track of grinding wheel and parameters in the actual machining process are optimized, and the experiment of milling SiCp/Al is designed. The results show that the surface roughness processed by the grinding tool is small. In the process of milling SiCp/Al, the main wear position of ball end milling cutter is the flank.

Model-based feed rate optimization for cycle time reduction in milling

Feed rate is an important determinant of the cutting force and cycle time. Selection of an appropriate feed rate can increase the processing quality and production efficiency. To determine an optimized feed rate, many methods have been developed to maintain a constant cutting force by applying a real-time feedback system constructed with data such as the tool condition, temperature, and cutting load of the spindle. However, these methods have low reliability because of difficulty in accurately measuring the spindle load. Moreover, real-time changes in the feed rate alter the cycle time. This study optimized the feed rate to a value that maintains the cutting force based on a cutting force prediction model and an algorithm to extract the cutting conditions from each line of the G-code. The feed rate optimization was applied to a flat end mill and ball end mill. An interpreter for the G-code was configured to calculate the tool center point and cutting condition. A real-time spindle power measurement system was constructed to measure the cutting force in each line of the G-code by identifying the parameters of the cutting force prediction model. The cutting force criterion was selected as the highest value among the predicted cutting forces. The optimized feed rate that maintains the cutting force was extracted based on the cutting conditions in other lines and the cutting force prediction model. The extracted feed rate was applied to the G-code by modifying only the feed rate command. Experimental results obtained with a commercial machining tool show that the proposed feed rate optimization significantly reduces the overall cycle time and effectively maintains the cutting force.

Modelling and analysis of the micro-milling of micro-dimpled structures with copying method on glow discharge polymer (GDP)

The surface with micro-dimpled structures on the target ball is helpful for improving nuclear fusion efficiency in inertial confinement fusion. Micro ball-end milling with copying method can provide a simple and effective option in machining micro dimples with high surface finish and geometry (dimension and shape) accuracy. In this paper, based on the established geometric error model, the influence of geometric errors and structural parameters of the machine tool on the dimple dimension and shape was first studied. Next, a model expressing the trajectory of cutting edge for simulating dimple geometry generated by ball-end milling was built. The model was used to analyze the effect of the spindle attitude, tool run-out and deflection deformation on the dimple dimension and shape. Micro ball-end milling tests were carried out, and the dimension, shape and cross-section profile of simulated and milled dimples were compared. A good correspondence between the simulated and milled dimple was observed, the largest error is 6.87%. Finally, from surface morphologies and surface roughness of the milled dimples, it was found that spindle attitude, axial feed rate are the main factors affecting the surface quality of micro dimple machined using micro ball-end milling with copying method. In particular, the axial feed rate need being optimized, reducing the effect of cutting edge quality and avoiding the deterioration of dimple surface and contour caused by a high feed rate. This research is of great significance for fabricating micro-dimpled functional surfaces by surface texturing based on milling methods.

Study on the Matching of Surface Texture Parameters and Processing Parameters of Coated Cemented Carbide Tools

Placing micro-textures on a tool surface can play an anti-wear and friction-reducing role and capture impurities and improve the tool-chip friction state, thus improving the cutting performance of the tool and the quality of the workpiece. To ensure the processing quality in the micro-texture-coated tool-cutting process, the process parameters and micro-texture parameters are limited to smaller parameters, which reduces the processing efficiency and increases the cost. Aiming at this problem, this paper designs orthogonal experiments of the cutting process and micro-texture parameters, builds an experimental platform for milling titanium alloy with a micro-texture-coated ball-end milling cutter, analyzes the influence of cutting parameters on tool milling performance and workpiece quality, establishes a high fitting prediction model, and optimizes parameters. The results show that the cutting parameters significantly affect the milling force, tool wear, and workpiece surface roughness, which are in the first response level, and the micro-texture parameters, which are in the second response level. It is proven that micro-texture has anti-wear and anti-friction effects, and it is found that micro-texture parameters affect the evaluation index by changing the distribution state of the micro-texture. It is found that the multiple linear regression model fits better. Parameter optimization results are: v = 159.4232 (m/min), ap = 0.211 (mm), f = 0.06 (mm/r), micro-pit diameter D = 62.3429 (μm), distance from blade L = 121.5184 (μm), and micro-pit spacing L1 = 235.6443 (μm). It provides some guidance for the selection of micro-texture parameters and cutting parameters on a micro-texture-coated tool.

Dynamics and stability analysis of five-axis ball end milling with low radial immersion considering cutter runout

The inevitable cutter runout has an important influence on the cutter dynamic properties and transient cutting condition, whereas it is usually neglected in analyses of mechanics and dynamics in five-axis ball end milling for lack of efficient mechanism modeling methods. This paper presents a novel mechanical and dynamic model considering runout to develop stability analysis suitable in five-axis ball end milling with low radial immersion. Firstly, the mathematical modeling of the cutting edge trajectory is derived from the cutting process considering runout effect. The impact of runout on the motility pattern of the cutter center and cutting edge is clarified. Then, the optimized tool coordinate system independent on runout parameters is defined to decompose the cutter complex elliptical or quasi elliptical motion caused by runout into two regular circular motion combinations. One is the center of cutter rotates around spindle, and the other is the cutting edge of cutter rotates around cutter center. Taking advantage of this strategy, the mechanics and dynamics of five-axis ball end milling considering runout are determined. A new analytic method is developed to extract the cutter and workpiece engagement (CWE) for five-axis ball end milling considering runout effect based on the transient cutting force signal. The superiority of the proposed dynamic and CWE models are both immune from the runout parameters. Thereafter, generalized precise integration method (GPIM) is presented to deduce dynamic system with multiple time delays into the state transition matrix. The axial angle of cutting edge acts as a bridge between transition matrix and the limit cutting positions defined by the analytic CWE to develop stability analysis for five axis ball end milling. The accuracy and efficiency of the GPIM is validated by the classic benchmarks and experimentally verified examples. Finally, five-axis ball-end milling experiments are performed to confirm the effectiveness of the proposed mechanical and dynamic models.

The Study of Radius End Mills with TiB2 Coating When Milling a Nickel Alloy

Nickel alloy high-speed processing technology using ball-end mills is characterized by high contact temperature and leads to accelerated tool wear. One of the effective ways to increase its reliability and service life is to modify the surface by applying functional antifriction layers in addition to wear-resistant coatings. Diamond-like carbon is often used as the latter. However, at cutting speed, when a cutting-edge temperature exceeding 650 °C is reached, the material of this coating reacts actively with oxygen in the air, and the sharply increasing adhesive component of wear quickly incapacitates the milling tooth, limiting its performance. Applying a coating of titanium diboride as an antifriction layer on top of nanocrystalline composite nitride coatings with good resistance to abrasive wear can be a solution to this problem. Our experiments have shown that such technology makes it possible to obtain a twofold increase in durability compared to a tool with a diamond-like antifriction coating in conditions when the cutting edge of the tool is subjected to cyclic thermal shocks above 800 °C, and the durability period of the radius end mill is about 50 min.

Effect of Coating Thickness on Abrasion and Cutting Performance of NCD-Coated Ball Endmills on Graphite Machining

Nano-crystalline diamond (NCD) coating to improve the performance of cutting tools, as the coating thickness varies, the cutting performance and lifespan of the tool varies because the radius of its cutting edge and coating surface roughness are altered. Therefore, an in-depth analysis on the impact of the variations in coating thickness on the cutting tool abrasion and quality of machined surface is necessary. In this study, two NCD ball endmills were coated with 8 and 12 μm thicknesses, and the tool abrasion and roughness of the machined plane were observed after milling. Furthermore, the morphology of the coated surface and abrased cutting edge were observed using a 3D confocal microscope. Consequently, we observed that individual nodules were formed on the continuous aggregates as the coating thickness increased, which increased the coated surface roughness. The two damage modes of the aggregation determined the dominant abrasion that occurred on the cutting edges of both types of coating thicknesses. Delamination and crater wear caused a sharp increase in the roughness of the machined surface. In summary, the increase in coating thickness delayed the delamination of the coating but increased the roughness of the cutting edge, which reduced the machined surface roughness.

Knowledge-based neural network for surface roughness prediction of ball-end milling

Theoretical modeling for surface roughness of ball-end milling generally results in low prediction accuracy due to the lack of machining information, excessive computational costs, and uncertainty of manual adjustment parameters. Besides, data-driven methods are limited in practical applications due to the lack of theoretical support or ‘black-box problems’ of neural network. To deal with these problems as mentioned above, this paper presents a coupling model for surface roughness prediction by combining the theoretical model of surface roughness and the data-driven approach. The core process is the secondary modeling with regard to the predictive result of theoretical model, which is realized by utilizing the knowledge-based neural networks with radial basis functions (KBaNN_RBF). Firstly, a theoretical model is established for the surface roughness prediction of ball-end milling by using the tool parameters and machining parameters. The output of the theoretical model is embedded into KBaNN_RBF as a priori knowledge. Secondly, low-dimensional features are extracted from the monitoring signals and adopted as the input of KBaNN_RBF for secondary modeling. And, the network structure is optimized by utilizing particle swarm optimization (PSO). Finally, ball-end milling experiment is carried out to verify the effectiveness of the presented KBaNN_RBF. Experimental results show that KBaNN_RBF is highly effective in improving the prediction accuracy and compressing the confidence interval (CI). Moreover, the comparison results show that the effectiveness of KBaNN_RBF is far superior to the traditional methods, such as back propagation neural network (BPNN) and support vector machine (SVM). This paper provides theoretical guidance for accurate monitoring of surface roughness in real industrial settings.

Research on Double-Arc Cutting Tool Design and Cutting Performance

With the increasing complexity of the workpiece surfaces in aerospace and automotive molding and other areas, an increasing number of cutting tools with different shapes and performance have become necessary. A new kind of cutting tool is developed with a double-arc revolving surface at the tool’s end to improve the processing quality in numerical control milling, referred to as a double-arc cutting tool (DACT) in this paper. The parametric geometric model of the DACT is established. Three types of cutting-edge curves are proposed (a cutting edge with a constant helix angle, a cutting edge with a constant pitch, and an orthogonal spiral cutting edge). Corresponding numerical simulation results are also provided as graphical representations. A DACT is manufactured and tested to verify its feasibility. Finally, two contrast experiments are conducted to prove that DACT has a higher processing quality than a ball-end mill (BEM). The advantage of the DACT is verified, which provides a theoretical basis for higher quality machining. The parametric design and application research provides a new method and theoretical basis for other new types of cutting tools.

Investigation of the cutting force and surface profile error when free form milling

Machining free-form shaped surfaces is a widespread task. Aerospace, automotive, mould making and many other sectors are challenged by ever increasing demands for precision and economy. In ball-end milling, the constantly changing cutting conditions affect the shape and volume of the chip, as well as the tool load and the quality of the resulting surface. It is important to know the cutting force for a given surface characteristic, because this makes it easier to plan the machining process. The prediction of cutting forces is very important for optimising machining strategies and parameters to achieve the required accuracy. In the experiments, the forces on the tool and the surface geometric accuracy were measured by milling test surfaces of 42CrMo4 with different cutting parameters. Based on the measured values, the average cutting force was determined, the variance of the force variation was investigated and the force momentum, which takes into account the machining time. The aim of this paper is to investigate and compare the cutting force and the surface profile error of the resulting surface during finishing milling with a ball-end milling cutter.

Fractal Analysis on Machined Surface Morphologies of Soft-Brittle KDP Crystals Processed by Micro Ball-End Milling.

The micro-defects on KH2PO4 (KDP) optic surfaces are mainly repaired by the micro-milling technique, while it is very easy to introduce brittle cracks on repaired surfaces, as KDP is soft and brittle. To estimate machined surface morphologies, the conventional method is surface roughness, but it fails to distinguish ductile-regime machining from brittle-regime machining directly. To achieve this objective, it is of great significance to explore new evaluation methods to further characterize machined surface morphologies. In this study, the fractal dimension (FD) was introduced to characterize the surface morphologies of soft-brittle KDP crystals machined by micro bell-end milling. The 3D and 2D fractal dimensions of the machined surfaces and their typical cross-sectional contours have been calculated, respectively, based on Box-counting methods, and were further discussed comprehensively by combining the analysis of surface quality and textures. The 3D FD is identified to have a negative correlation with surface roughness (Sa and Sq), meaning the worse the surface quality the smaller the FD. The circumferential 2D FD could quantitively characterize the anisotropy of micro-milled surfaces, which could not be analyzed by surface roughness. Normally, there is obvious symmetry of 2D FD and anisotropy on the micro ball-end milled surfaces generated by ductile-regime machining. However, once the 2D FD is distributed asymmetrically and the anisotropy becomes weaker, the assessed surface contours would be occupied by brittle cracks and fractures, and corresponding machining processes will be in a brittle regime. This fractal analysis would facilitate the accurate and efficient evaluation of the repaired KDP optics by micro-milling.

Study on surface integrity enhancement of titanium alloy milling with ball end mill by micro-texture

Study on surface integrity enhancement of titanium alloy milling with ball end mill by micro-texture

Geometric modeling of the rubbing zone limits in 3-axis ball-end milling

Geometric modeling of the rubbing zone limits in 3-axis ball-end milling