Cutting Edge Rounding Research Articles

Redefinition of precision in finishing milling: Exploring the influence of tool margin and edge micro-radius on surface roughness

This article presents an analysis of microgeometry parameters, specifically the radius of cutting edge rounding, margin width, and rake angle influence on surface roughness in the milling of 7075 alloy. The study is underpinned by a set of 243 cutting tests conducted using 27 mills, each with a unique combination of geometry, feed, and radial infeed. Experimental mathematical models of the roughness parameters were developed. The findings reveal that while the influence of the cutting edge rounding radius on surface roughness is nonlinear and non-monotonic, the margin width has a monotonic effect and is the most significant factor impacting roughness.

Arc-enhanced glow discharge ion etching of WC-Co cemented carbide for improved PVD thin film adhesion and asymmetric cutting edge preparation of micro milling tools

Wear-resistant thin films on cutting tools require effective ion etching to enhance adhesion and thus extended tool service life. Arc enhanced glow discharge (AEGD) ion etching, characterized by high ionization degrees and high etch rates, was applied to ultrafine-grained WC-Co cemented carbide, commonly used for micromilling cutters. The effect of AEGD ion etching on the surface integrity of WC-Co and the resulting adhesion behavior of a TiAlSiN thin film was investigated by varying the etching time in comparison with conventional glow discharge (GD) ion etching. In addition, the impact of intensive etching on the cutting edge geometry of micro end cutters and, in turn, on the cutting performance in micromilling of hardened and annealed high-speed steel was evaluated.AEGD achieves remarkable etch rates of 12 nm/min at extended etching times, which are 100 times greater than conventional glow discharge (GD) ion etching. Prolonged AEGD ion etching for ≥30 min removes entire near-surface WC grains and exposes carbides beneath, resulting in increased surface roughness. After the etching process, polished WC-Co substrates exhibit a slight reduction in residual compressive stresses, which steadily decrease with increasing AEGD ion etching time. Furthermore, a TiAlSiN thin film demonstrates high adhesion on AEGD-etched surfaces compared to GD ion etching. Even a brief 5 min AEGD ion etching ensures the highest adhesion class according to the Rockwell C indentation test. Moreover, the intensive material removal results in significant changes in cutting edge geometry of micro end cutters, yielding substantial cutting edge rounding and an asymmetrical shape with form-factors Κ ≥ 2. In cutting tests, the resulting cutting edge geometries effectively reduce the wear formation and the associated wear-related increase in process forces during micromilling hardened and tempered powder metallurgical high-speed steel. In summary, AEGD ion etching emerges as a highly effective method for both enhancing thin film adhesion and preparing adapted asymmetrical cutting edge geometries for micromilling tools.

Preparation of asymmetrical cutting edge geometries on micro end mills using pressurized wet abrasive jet machining for hard micromachining of AISI M3:2

Cutting edge preparation is an established approach in the field of machining technology for optimizing the performance of cutting tools. However, the potential of asymmetric geometries has not yet been sufficiently utilized for filigree micromilling tools. In this regard, the study presents investigations on the adjustment of asymmetric microgeometries through the design of the pressurized air wet abrasive jet machining (PAWAJM). The study features results regarding the design of the preparation process as well as subsequent application tests in a hard micromilling process of the hardened high-speed steel AISI M3:2. The application tests focus on the effect of the conditioned cutting edge on the process forces and the surface quality as well as the tool life. The results show that asymmetrical microgeometries with small average cutting edge rounding and a form-factor of K > 1.2 can be achieved by PAWAJM. Machining tests revealed a potential reduction of the wear development and process forces for modified tools with low cutting edge rounding and asymmetrical microgeometry.

Analysis of subsurface damage during milling of CFRP due to spatial fibre cutting angle, tool geometry and cutting parameters

During machining of carbon fibre reinforced plastics the anisotropy of the material and the resulting cutting conditions can cause various types of damage such as delamination, burrs or subsurface damage. Subsurface damage can lead to a reduction in surface quality or component rejection. In this paper, a new method is used to detect subsurface damage caused by peripheral milling over the entire cut. This analysis, using a newly defined spatial fibre cutting angle θne, tool geometry and process parameter, provides a deeper understanding of the damage formation. While the damage area varies with the uncut chip thickness and the rake angle of the tool, the cutting edge rounding and the fibre cutting angle prove to be important in determining the depth of damage. The detected damage area is 44–65 % of the fibre cutting angle range from 0° to 90°, which can be extended up to 12 % due to the damage depth when milling an external radius.

Advanced approach of forming cutting edge radii on cemented carbide cutting tools using plasma discharges in electrolyte

The paper deals with the task of preparing cutting edge microgeometry. Unconventional methods for edge preparation are presented, and an overview of articles, patents, and reports that deal with modern and advanced approaches are stated. Moreover, an innovative cutting edge preparation method using plasma discharges in an electrolyte was examined. The main aim was to determine the effect of the process parameters, namely electrolyte concentration, the temperature of the electrolyte, the voltage between electrodes and the operating time, on the shape and size of the cutting edge rounding as well as surface roughness and topography. The tested type of cutting tool was cutting insert. The cutting inserts were made of cemented carbide (WC + Co). It was examined that cutting edge radius sizes were strongly affected by the process parameter of plasma discharges in electrolyte as well as the shape of rounding. However, specific types of defects can occur on the cutting edge after edge preparation using plasma discharges in electrolyte. These defects can be avoided by correctly setting the process parameters. From the results of the experimental research, it was confirmed that cutting edges can be rounded without defects in the entire range of electrolyte concentration, but the setting of voltage and temperature of the electrolyte must be simultaneously considered. Furthermore, decreasing the electrolyte concentration, the temperature of the electrolyte and the voltage between electrodes resulted in a larger cutting edge radius. Cutting edge preparation using plasma discharges in electrolyte takes only a few seconds, depending on the cutting edge radius sizes. Cutting edge radii with a value of 20 μm were manufactured in 30 s. This innovative advanced edge preparation method is one of the most productive edge preparation methods. An even more important aspect is not to burden the environment with hazardous waste such as acids because this electrolyte solution can be prepared by dissolving a small amount of salt in tap water. The issue of the topography of the surface of cemented carbides after PDE treatment should be expecially heeded.

Influence of cutting edge microgeometry on the cutting forces when machining difficult-to-cut materials

The paper presents research investigating the influence of cutting tools microgeometry on the cutting forces when milling difficult-to-cut materials. Austenitic stainless steel AISI 316L and nickel alloy Inconel 718 were machined with cemented carbide tools with various cutting edge rounding size while measuring the cutting forces during the process. From the standpoint of milling difficult-to-cut materials lowering the cutting forces load on the tool can be difficult to achieve without significant reduction of cutting parameters. Previous research into the cutting edge microgeometry suggests that modification of the cutting edge of milling tools can substantially extend the effective tool life, reduce cutting forces in the process and ensure higher quality of the machined surface. Results of long term wear tests of tools with cutting edge rounding sizes of 15, 30 and 45 µm are compared to the results of a sharp unprepared cutting tool, and the results of each machined material are also compared. Possible influence of cutting edge radius on the process for both materials was tested for cutting conditions constituting finishing operation. The most effective cutting edge radius size differed between the materials, with 15 µm rounding performing the best for AISI 316L and the sharp unprepared tool performing the best for the Inconel 718 alloy.

Influence of the cutting edge preparation of carbide punching tools for punching of ultra-high strength steel strips

In order to ensure a robust punching process of ultra-high strength steel spring strips using carbide punching tools, a high stability of the cutting edge is required. Here the cutting edge preparation process has a significant influence. In the presented study, high-pressure abrasive water jet technology for cutting edge preparation was designed, investigated and analysed. For defining the optimal cutting edge shape regarding stresses, a numerical analysis using LS-DYNA was conducted. Within this analysis, the influence of the cutting edge rounding and symmetry was numerically tested and evaluated. Based on the results, two cutting edge shapes were selected and prepared using the high-pressure abrasive water injection jet technology. The tools were applied in the punching process up to 50,000 strokes in order to analyse the cutting performance and tool wear. With regard to a highly wear resistant tool for punching, a combination of the abrasive water injection jet preparation routine and a CVD diamond coating are under further investigation and first insights are presented additionally.

Investigation of CFRP damages induced by the interface high temperature and mixed tool wear mechanism in drilling of thin-walled CFRP /Ti stacks

Due to the poor thermal conductivity and machinability of CFRP and Ti6Al4V, significant heat accumulation at the interface and rapid tool wear are considered the main factors restricting the hole quality. This study conducted a thin-walled CFRP/Ti stack drilling experiment to investigate the evolution of the thrust force, temperature and tool wear versus different drilled hole numbers and spindle speeds, affected by which the novel material removal behavior was revealed. Results showed that the thrust force and interface temperature increased with the hole number and spindle speed, causing a significant increase in the cutting edge rounding and flank face wear dominated by the many fiber bundles and metal debris. In turn, the various tool wear led radial interface temperature to alternately transfer between Φ = 45° and 135°. Under the cyclic thermo-mechanical function, the fibers underwent significant bending deformation as they lost the support of the degenerated matrix resin, forming severe subsurface damage when the interface temperature exceeded the matrix glass transition temperature (Tg = 110 °C). Combined with the comprehensive evaluation of exit damages, a relatively higher spindle speed was preferred for selecting the initial drilling of thin-walled CFRP/Ti stack and gradually reducing the spindle speed with increasing tool wear extent.

Study on Characteristics of Tool Wear and Breakage of Ultrasonic Cutting Nomex Honeycomb Core with the Disc Cutter

Ultrasonic cutting is an advanced technology for processing Nomex honeycomb materials. The disc cutter is one of the most commonly used tools, whose wear and breakage state have an important impact on the honeycomb material machining process. Currently, the disc cutter lacks systematic characterization methods, and its tool wear laws are not yet clear. This paper conducts a wear experiment of the disc cutter in an ultrasonic cutting Nomex honeycomb core and proposes the attributes of cutting edge rounding (CER), flank wear VB, diameter reduction, and cutting edge breakage width to characterize the tool wear and breakage forms quantitatively. Moreover, the tool wear and breakage forms of the disc cutter are categorized, and the variation laws of the disc cutter wear and breakage characteristics are studied. The experimental study reveals that the wear forms of the disc cutter are mainly cutting edge dulling and flank wear. The CER and flank wear VB increase with increasing cutting length, and the wear mechanism is mainly abrasive wear. The breakage forms are mainly chipping and cracking breakage. The diameter reduction changed slowly, and the cutting edge breakage width tended to increase. The surface quality of the honeycomb gradually deteriorates with the increase of tool wear and breakage. The experimental results are important to study the tool wear mechanism of ultrasonic cutting of the Nomex honeycomb core with the disc cutter as well as tool design and manufacture.

Identification of the process damping coefficient in dry and wet machining of steel

Flank face chamfers are an effective way to suppress vibrations and increase the productivity of milling processes. The underlying process damping mechanism is the so-called indentation effect. The effect describes the process damping as a result of an additional force due to the indentation of workpiece material under the flank face. In literature, this force is commonly modeled by the volume indented under the flank face and a process damping coefficient. To determine the process damping coefficient, various approaches with partly contradictory results exist. In this paper, a novel method to calculate the process damping coefficient based on process forces measurements in orthogonal cutting is applied for steel machining. The method considers ploughing effects of flank face chamfer and cutting edge rounding as well as plastic deformation effects. In the current investigation, the approach is applied to different cooling strategies, chamfer widths, and cutting speeds. The results show that the cutting speed has the most significant influence on the process damping coefficient. With increasing cutting speed, the process damping coefficient increases, which can be attributed to strain rate hardening effects.

Performance analysis of drills with structured surfaces when drilling CFRP/AA7075 stack under MQL condition

When drilling multi-stack materials, the dissimilar material response, severe tool wear, and long hot metal chips pose serious challenges in achieving the requisite hole quality. There is difficulty in effectively lubricating the cutting zone as the drill penetrates deep into the drilled hole. Structuring the surfaces of cutting tools is an approach to improve their tribological performance. Micro-textures are created on the drill flute and margin surfaces using laser micro-machining to improve the micro-pool lubrication effect and reduce the friction during machining CFRP/aluminum alloy stacks. The performance of four different textured drills - dimple on flute, groove on flute, perpendicular and parallel grooves on margin – is compared with that of the non-textured drill. The thrust force, hole quality (roughness, roundness and delamination), tool wear (BUE and cutting edge rounding), and chip morphology are analyzed. Among the four textured drills, the dimple textured drill results in the best performance due to the improved micro-pool lubrication effect of micro-dimples in the flute region, thereby producing short metal chips and best hole quality. It also retains the texture depth for a longer duration as compared to the other textured drills.

Estimation of Drag Finishing Abrasive Effect for Cutting Edge Preparation in Broaching Tool.

In recent years, cutting edge preparation became a topic of high interest in the manufacturing industry because of the important role it plays in the performance of the cutting tool. This paper describes the use of the drag finishing DF cutting edge preparation process on the cutting tool for the broaching process. The main process parameters were manipulated and analyzed, as well as their influence on the cutting edge rounding, material remove rate MRR, and surface quality/roughness (Ra, Rz). In parallel, a repeatability and reproducibility R&R analysis and cutting edge radius re prediction were performed using machine learning by an artificial neural network ANN. The results achieved indicate that the influencing factors on re, MRR, and roughness, in order of importance, are drag depth, drag time, mixing percentage, and grain size, respectively. The reproducibility accuracy of re is reliable compared to traditional processes, such as brushing and blasting. The prediction accuracy of the re of preparation with ANN is observed in the low training and prediction errors 1.22% and 0.77%, respectively, evidencing the effectiveness of the algorithm. Finally, it is demonstrated that the DF has reliable feasibility in the application of edge preparation on broaching tools under controlled conditions.

Analytical model for predicting tool wear in orthogonal machining of unidirectional carbon fibre reinforced polymer (CFRP)

Progressive tool wear due to abrasive carbon fibres is one of the main issues in machining of CFRP and responsible for the short tool life. Because of occurring wear during machining, the tool’s micro-geometry changes continuously resulting in higher process forces and an increasing risk for workpiece damages. In this paper, a novel analytical model is presented in order to predict the wear-related change of the micro-geometry in orthogonal machining of CFRP depending on the fibre orientation and the initial tool geometry. For this purpose, a concept called the wear rate distribution is introduced which represents a measure to quantify the wear rate along the active micro-geometry. Based on experimental investigation, it is shown that the shape of an arbitrary wear rate distribution between two closely spaced wear states can be approximated and parameterised with a “line - curve - line” approach. Using the authors’ previously published analytical force model, the wear rate distribution can be calculated as function of five wear parameters that are used to parameterise the active micro-geometry of an arbitrary wear state. Based on an iterative solver, this is used to simulate the tool wear progression during machining. For model validation, the simulation is compared to experimental data in terms of the cutting edge profiles, the amount of worn tool material and the process forces. Accordingly, the wear model is capable to reproduce the most important wear characteristics, e.g. the cutting edge rounding, the decreasing clearance angle and the increasing contact length at the flank face.

Analysis of the grinding wheel wear and machining result during cutting edge preparation with elastic bonded grinding wheels

Cutting edge preparation can be considered as one of the most effective methods for optimizing the cutting tool life and the machining result. In this article, a preparation technique using elastic bonded superabrasive grinding wheels is applied. This method proved to be highly flexible in terms of the achievable cutting edge geometry. However, very little knowledge exists about the grinding wheel wear behavior and therefore the process reliability during cutting edge preparation. In this article, the impact of the process kinematics and parameters on the grinding wheel wear and preparation result is investigated and discussed. For this purpose, the impact of the depth of cut (20, 40 and 60 μm) was investigated, because it serves as the major setting parameter for the size of the cutting edge rounding. However, it also impacts the contact conditions and thermo-mechanical loads in the grinding wheel. The experimental results show that this preparation method achieves a high preparation accuracy and repeatability at small and medium depths of cut (20 and 40 μm). For a depth of cut of 60 μm, the preparation result became more inappropriate (increased deviation of the cutting edge shape from an ideal radius) with an increasing number of prepared cutting edges. Here, the soft grinding wheel exhibited a higher process stability in terms of repeatable machining results. The machining results correspond to the experimental findings from the grinding wheel radial wear Δrs. At a depth of cut of 20 and 40 μm, the grinding wheel radial wear for the hard bond was lower than for the soft bond. At a depth of cut of 60 μm, the grinding wheel radial wear for the hard bond exceeds the value for the soft bond by 10%. However, the grinding (G) ratios for the hard bond were higher for all investigated depths of cut. The highest difference was observed at a depth of cut of 20 μm. Here, the G ratio for the soft grinding wheel was 7.92 and for the hard one 18.53. Furthermore, an application scenario was introduced using suitable dressing cycles, so that up to 138,000 cutting edges (equals 34,500 indexable inserts) could be prepared with one grinding wheel using this preparation technique in industrial tool manufacturing applications.

FE-Simulation Based Design of Wear-Optimized Cutting Edge Roundings

The performance of cutting tools can be significantly enhanced by matching the cutting edge rounding to the process and material properties. However, the conventional cutting edge rounding design is characterized by a significant number of experimental machining studies, which involve considerable cost, time, and resources. In this study, a novel approach to cutting edge rounding design using FEM-based chip formation simulations is presented. Based on a parameterized simulation model, tool temperatures, stresses and relative velocities can be calculated as a function of tool microgeometry. It can be shown that the external tool loads can be simulated with high agreement. With the help of these loads and the use of wear models, the resulting tool wear and the optimum cutting edge rounding can be determined. The final experimental investigations show a qualitatively high agreement to the simulation, which will enable a reduced effort design of the cutting edge in the future.

Numerical and experimental analysis of thermal and mechanical tool load when turning AISI 52100 with ground cutting edge microgeometries

Tools made of polycrystalline cubic boron nitride (PcBN) are usually prepared with a rake face chamfer to increase the performance in hard turning. This chamfer is produced by a tool grinding process. The preparation of the cutting edge itself considering the process and material properties offers further potential for increasing tool performance. In this paper, the rounding of the cutting edge is produced by the already established and highly productive tool grinding process instead of using conventionally processes such as brushing or drag finishing. Therefore, the rounding is approximated by multiple ground chamfers. The influence of the cutting edge microgeometry on the thermomechanical load is investigated by finite element method. By enlarging the microgeometry, the mechanical stress on the tool is significantly reduced. However, an increase in the size of the cutting edge rounding is also linked to an increase in the thermal tool load.

Influence of Cemented Carbide Composition on Cutting Temperatures and Corresponding Hot Hardnesses.

During metal cutting, high temperatures of several hundred-degree Celsius occur locally at the cutting edge, which greatly impacts tool wear and life. Not only the cutting parameters, but also the tool material’s properties influence the arising cutting temperature which in turn alters the mechanical properties of the tool. In this study, the hardness and thermal conductivity of cemented tungsten carbides were investigated in the range between room temperature and 1000 °C. The occurring temperatures close to the cutting edge were measured with two color pyrometry. The interactions between cemented carbide tool properties and cutting process parameters, including cutting edge rounding, are discussed. The results show that cemented carbides with higher thermal conductivities lead to lower temperatures during cutting. As a result, the effective hardness at the cutting edge can be strongly influenced by the thermal conductivity. The differences in hardness measured at room temperature can be equalized or evened out depending on the combination of hardness and thermal conductivity. This in turn has a direct influence on tool wear. Wear is also influenced by the softening of the workpiece, so that higher cutting temperatures can lead to less wear despite the same effective hardness.

Additive surface texturing of cutting tools using pulsed laser implantation with hard ceramic particles

In recent years surface texturing of the cutting tools has proved to improve tribological characteristics at tool/chip and tool/workpiece interface and help to reduce cutting and feed forces as well as tool wear. Most, if not all, of the studies have focused on subtractively made textures whereby the material is removed from the surface. This study investigates the performance of additively made surface structures whereby hard ceramic particles are dispersed in the form of dome shaped textures on the surface of the cutting tools using solid state millisecond pulsed laser (pulsed laser implantation). Dry cutting tests were performed on ductile cast iron. The results show a greater reduction of process forces with implantation of flank face as compared to rake face. Both cutting and feed forces were reduced by 10% compared to the non-structured tool. In addition, the tool life increased by a factor of 3 whereas the average flank wear reduced by as much as 80% and cutting edge rounding by up to 60%.

Studies on wear behavior of AlTiN-coated WC tool and machined surface quality in micro endmilling of Inconel 718

The recent developments in science and technology lead to the miniaturization of components in fields like aerospace, biomedical, and electronics. Due to the small tool dimensions and premature tool failure, the tool wear behavior is complicated in micro endmilling of difficult-to-cut materials. In this work, the influence of size effect on wear behavior of AlTiN-coated WC micro endmill and its effects on surface roughness, burr formation, and chip formation during machining on Inconel 718 was studied. It was found that adhesion, delamination, chipping, cutting edge rounding, and flank wear are the significant wear behaviors on AlTiN-coated WC micro endmill during machining of Inconel 718. Workpiece adhesion was observed to be severe in the plowing dominant region. The tool life with 6-μm feed/tooth was found to be 60% more than that with 0.5-μm feed/tooth. The tool failure criteria based on the width of flank wear and cutter edge radius were observed close to 27 and 9 μm, respectively. The feed/tooth adjacent to cutting edge radius was observed as the most favorable cutting condition for good tool life and surface quality.

Influence of tool material properties on the wear behavior of cemented carbide tools with rounded cutting edges

Tool wear and life of cutting tools are significant evaluation criteria of machining processes. However, the occurring wear mechanisms are influenced by a number of factors such as the process parameters, tool geometry and the material properties of the tool and workpiece. Previous research has shown a high potential for the use of adapted cutting edge microgeometries on cemented carbide cutting tools. The optimal cutting edge rounding is strongly dependent on the tool material properties. However, the influence and relation between the properties of the cemented carbide tool, the microgeometry and the resulting tool wear are not yet completely understood. In this study the tool wear is investigated by systematically varying the mechanical and thermophysical properties of the tool material, the tool microgeometry and cutting process parameters. Significant influencing variables of tool wear are identified and existing relationships quantified. Results show that the occurring wear mechanisms depend on the cutting edge microgeometry as well as the mechanical properties of the cemented carbide. During continuous machining the minimum required cutting edge rounding is a function of the cemented carbide’s fracture toughness. This knowledge allows an adaption of the cutting edge microgeometry depending on the substrate properties to reduce the tool wear and achieve a longer tool life.