Cutting Edge Microgeometry Research Articles

Influence of the thickness of TiAlSiN on the thermal properties as input parameter for FEM-simulation

Hard coatings deposited by physical vapor deposition are state of the art for wear and oxidation protection of cutting tools. The cutting performance depends on coating material and process as well as cutting edge microgeometries. Both have an influence on the thermomechanical tool loads resulting in tool wear. Therefore, a process adapted design for the consideration of the entire system is necessary. One approach to substitute costly machining investigations and save material resources is the use of finite element (FE)-based chip formation simulations. However, in order to perform these simulations, information about chemical, thermal and physical coating behavior in the temperature range relevant for machining is necessary. In the present study, nanocomposite TiAlSiN coatings with varying coating thicknesses were deposited on cemented carbide tools. The effect of coating thickness on coating morphology, chemical composition, thermal conductivity as well as indentation hardness at ϑ = 20 °C, ϑ = 200 °C, ϑ = 400 °C and ϑ = 600 °C was analyzed. Therefore, three coating variants with a coating thickness of ds = 2 μm, ds = 4 μm and ds = 6 μm were deposited. Additionally, the distribution of the heat, generated during turning 42CrMo4 + A, was simulated for the coated cutting tool. A columnar morphology with constant chemical composition was determined for the variants. While the arithmetic mean value of the coating roughness increased with increasing coating thickness, there was no influence of coating thickness on thermal diffusivity and high temperature coating hardness measurable. Nevertheless, an influence of the tool temperature can be observed in the application behavior in turning tests as well as in the simulation, possibly caused by a change in the contact conditions due to increasing cutting edge microgeometry by increasing coating thickness. Regarding the tested TiAlSiN hard coatings no significant influence of the coating thickness on properties such as thermal diffusivity and indentation hardness were observed. This leads to the assumption, that even when the coating thickness is changed no significant changes in the FEM simulation are needed, which makes modelling easier.

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.

An improved Lagrange-based numerical model for machining Ti-6Al-4V alloy concerning tool cutting edge microgeometry

Current Lagrange-based machining models usually involve a sacrificial layer (LAG-SL) to facilitate the chip formation. Otherwise, severe element distortion error arises especially when tool cutting edge microgeometry is considered. In view of this limitation, an improved Lagrange-based machining model is proposed that acquires no sacrificial layer (LAG-nSL) and can simulate completely the cutting, unloading and cooling process. Through comparisons with plenty of experimental measurements, the presented model is found not only applicable for machining using tool with various edge radii, but also yields better outcomes of chip morphologies, forces and residual stress distribution.

The influence of cutting edge microgeometry on the broaching of Inconel 718 slots

In aero-engine production, the dovetails (firtrees) of turbine discs are manufactured by broaching. Introducing innovative micro-geometry modifications to broaching tools can significantly influence cutting force, energy consumption, tool wear, and cutting edge temperature during broaching. Therefore, this study aims to study this influence by treating the cutting edge by brushing with ceramic bristles. The results reveal that the increase in cutting edge radius significantly influences the cutting force, particularly its component in the forward direction, equating it to the tangential component. Furthermore, during the experimental tests, considerable wear was observed on the cutting edge, which generated strong vibrations detected through the force signals, accounting to poor surface quality and a higher coefficient of friction close to 1. The 2D simulations generated information on temperature distribution along the cutting edge profile. On the other hand, was observed the presence of subsurface damage characterized by distorted grain boundaries aligned with the cutting direction, along with the formation of uninterrupted non-serrated chips due to thermoplastic deformation. Further, 12 µm cutting edge radius exhibits the best performance in terms of cutting force, temperature, and surface quality.

Selection of the numerical formulation for modeling the effect of tool cutting edge microgeometries in machining of Ti6Al4V titanium alloy

The Finite-element method (FEM) is often used to simulate the metal machining process. Currently, several formulations are used in metal cutting simulation, such as Lagrangian (LAG), Eulerian (EUL), Arbitrary Lagrangian–Eulerian (ALE), and Coupled Eulerian–Lagrangian (CEL). The selection of the numerical formulation that better reproduces the material separation in machining to form the chip is a critical issue. This is quite important when the ratio between the uncut chip thickness and the cutting edge microgeometry, often represented by a cutting edge radius, is very low. In this study, orthogonal cutting of Ti6Al4V titanium alloy using different tool edge microgeometries is investigated using LAG and CEL approaches. In the case of LAG approach, two types of cutting models were develop: one using a sacrificial layer (hereby called LAG-SL), and another without sacrificial layer (hereby called LAG-nSL). The cutting models have included a constitutive model (both plasticity and damage) considering the effects of strain, strain rate, temperature, and state of stress, which have proved to be accurate enough to represent the mechanical behavior of the Ti6Al4V alloy in machining. Comprehensive comparisons between CEL and LAG-based cutting models and experimental results are carried out in terms of chip morphology, forces, and residual stresses. When compared to the experimental results, LAG-nSL model gives the best predictions of the maximum chip compression ratio (CCRm) with an error of 9.5%, cutting force (12.8%) and thrust force (9.3%) than the other two models. In the case of the of residual stress profiles, LAG-SL offers good predictions of the maximum compressive residual stress by a preference ratio of 75%. Although CEL yields the worst predictions of chip morphology and forces, it is preferred from the perspective of the thickness of the layer affected by residual stress.

An improved approach to tool life promotion concerning cutting edge microgeometry

An improved approach to tool life promotion concerning cutting edge microgeometry

Effect of edge radius on forces, tool wear and surface integrity under edge radius dominated tool-chip contact conditions

Cutting-edge micro-geometry is a crucial factor influencing chip formation and tool performance. This paper investigates the effects of varying cutting edge radius (36–70 µm) on machinability and chip morphology during finish turning Ti6Al4V. An increase in edge radius decreases the cutting to thrust force ratio and produces lower chip thickness due to the increase in plowing zone depth. The machining temperature for the 48 and 52 µm edge radius tools is lower compared to all other tools. At the initial stage, the edge prepared tools exhibit larger flank wear, whereas subsequent flank wears progression is slower for the prepared tools as compared to the sharp tool. BUE and premature chipping is reduced for larger edge radius tool due to better edge stability provided by cutting edge preparation. Beyond the 59 µm edge radius, the process force, machining temperature, tool wear, and surface roughness increased steeply due to the increase in the size of the plowing zone. In addition to cutting force and machining temperature data, surface roughness, tool wear measurements and XRD analysis show that a radius range of 50–55 µm results in optimum performance for finish turning Ti6Al4V.

Modeling of stresses at the cutting wedge in the interrupted cut for the design of the cutting edge microgeometry

The wear behaviour of cutting tools can be significantly improved by a load-optimized design of the cutting edge microgeometry. Thereby, the knowledge of local mechanical stresses is necessary. The experimental-based modelling of mechanical stresses in the continuous cut was already investigated in previous work. In this paper, this method is adapted to the interrupted cut by considering contact lengths, process forces and process temperatures during tool entry and exit. The identified mechanical stresses and temperatures are used for a tool material specific cutting edge microgeometry design.

INCREASING TOOL LIFE THROUGH ADJUSTMENT OF CUTTING EDGE AND TOOLPATH DURING MILLING OF INCONEL 718

This paper focuses on analysis of tool life during milling of nickel alloy Inconel 718. Several modifications of one type of carbide tool with different cutting edge finish adjustments (lapping, drag finishing) were proposed for milling of Inconel 718. These finish adjustments significantly influence cutting edge properties (hardness, radius value, etc.). The toolpath geometry setup has a great influence on chip formation and tool load characteristics during milling strategies. The milling tests were performed by using the cutting tools with several adjustments of cutting edge in combination with the toolpath geometry setup. The paper therefore presents the analysis that tool life can be significantly increased through proper finish adjustment of cutting edge microgeometry and proper toolpath setup.

Design of tool grinding processes for indexable inserts made of rocks

Using natural rocks as alternative cutting tool material poses a possibility to meet actual environmental, economic and geopolitical challenges. The present state of knowledge, however, is not sufficient to allow a knowledge-based design of the tool grinding process of cutting tools made of rock. For this reason, this study presents an investigation of the significance of the grinding process parameters and grinding tool specifications for the flank face and cutting edge roughness as well as for the cutting edge microgeometry besides an analysis of the scatter of the grinding results in tool grinding of rock inserts. Thus, the study contributes to a knowledge-based design of tool grinding processes of rock tools. In this context, confocal and focus variation microscopes are used besides SEM images to investigate the above mentioned factors in the plunge face grinding of rock inserts from five different rocks. The results identify the axial feed velocity of the plunge face grinding process as a highly significant influence factor for cutting edge roughness and microgeometry, while cutting speed only shows a significant influence on cutting edge microgeometry. Besides that, highly significant influences of the used rock type and the abrasive grain size are identified for all three mentioned factors. Grinding result analyses show a scatter between 0.04 and 25.00 µm depending on the parameter and rock investigated. Additionally, recommendations for the design of the tool grinding process of rock tools are presented deduced from the obtained results.

The Precision Analysis of Cutting Edge Preparation on CBN Cutting Inserts Using Rotary Ultrasonic Machining.

This paper is focused on the issue of preparing the cutting edge microgeometry of cutting inserts made of cubic boron nitride (CBN). The aim of this research was to investigate the possibilities of rotary ultrasonic machining (RUM) for preparing asymmetric cutting edge microgeometries of various shapes (chamfers, circular, and elliptical rounding and their combinations) on a CBN cutting tool. In this article, a new type of advanced cutting edge preparation method is presented. CBN is relatively resistant to the most often used (abrasive) methods of cutting-edge preparation, due to its very high hardness (which is a prerequisite property for machining difficult-to-cut materials). Such hard materials could be processed using advanced manufacturing methods, and rotary ultrasonic machining (RUM) is one such method. Experiments have shown that RUM can be used for machining CBN. However, high hardness is not the only challenge here. For cutting edge preparation, it is necessary to achieve an adequate accuracy of size and dimensions. The presented paper analyzes the suitability of the RUM process for processing CBN inserts. The results of the experiment showed that this method can be used for preparing asymmetric cutting edge microgeometries with various shapes.

Tool wear when using natural rocks as cutting material for the turning of aluminum alloys and plastics

The growing challenges regarding climate-neutral and resource-saving manufacturing technology is forcing research and development to work out new cutting tool alternatives since the production of conventional cutting materials requires rare raw materials and huge amounts of energy. Natural rocks could be such an alternative since they are available in large quantities worldwide, have a potentially suitable property profile, and do not require energy-intensive processes to make them usable as cutting material. However, according to the current state of knowledge, there are only a few studies on the usability and suitability of natural rocks as cutting materials for machining processes. Therefore, in this article, inserts made of natural rocks are ground and used in turning operations. Their operational behavior is then described by the occurring tool wear and workpiece surface roughness. The influence of different natural rocks, process parameters as well as cutting edge microgeometries is compared after the machining of aluminum alloys and plastic. In the end, this made it possible to define process and tool properties in which natural rocks have application potential.

Analysis of abrasives on cutting edge preparation by drag finishing

Cutting edge preparation has become more important for tool performance. The micro-shape, radius and surface topography of the cutting edge play a significant role in the machining process. The cutting edge of solid carbide end mills has some micro-defects after grinding. For eliminating aforementioned problem, this study investigates drag finishing (DF) preparation for solid carbide end mills to reconstruct cutting edge micro-geometry. This paper is to present the design of DF experimental setup and analyze the characterization of various abrasive media (K3/600, K3/400, HSC 1/300 and HSO 1/100) on the evolution of the surface/roughness along the cutting edge. In parallel, the mechanism of material removal and the kinematics trajectory of the drag finishing are presented. In fact, the form factor (also called as “K-factor”) of the cutting edge micro-geometry is quantified. Comparing with four lapping media, the higher material removal rate (MRR) and the lower surface roughness are obtained by HSO 1/100 abrasive process. The results show that the cutting edge K-factor, MRR and surface topography are influenced by the abrasive particles size, composition and process time.

Effects of Orthogonal Cutting with Different Cutting Edge Microgeometry on the Surface Integrity of Unidirectional Carbon Fibre Reinforced Plastics

Effects of Orthogonal Cutting with Different Cutting Edge Microgeometry on the Surface Integrity of Unidirectional Carbon Fibre Reinforced Plastics

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.

Tool wear and spring back analysis in orthogonal machining unidirectional CFRP with respect to tool geometry and fibre orientation

Machining abrasive carbon fibre reinforced polymers (CFRP) is characterised by extensive mechanical wear. In consequence, the cutting edge micro-geometry and thus the tool/material contact situation are continuously changing, which affects process forces and machining quality. As a conclusion, a fundamental understanding of the tool wear behaviour and its influencing factors is crucial in order to improve performance and lifetime of cutting tools. This paper focuses on a fundamental tool wear analysis of uncoated tungsten carbide cutting inserts with different combinations of fibre cutting angles and tool geometries. For this purpose, orthogonal machining experiments with unidirectional CFRP material are conducted, where the wear progression of the micro-geometry is investigated by means of five wear parameters lα, lγ, γ*, α*, and bc. For detecting the actual contact zone of the cutting edge and to measure the elastic spring back of the material, the flank face is marked via short pulsed laser processing. Furthermore, the process forces and the wear rate are measured. It is shown that the material loss due to wear clearly varies along the tool’s contact region and is highly dependent on the clearance angle and the fibre cutting angle Φ, while the influence of the tested rake angles is mostly negligible. Especially in machining Φ=30° and Φ=60°, a strong elastic spring back is identified, which is more intense for smaller clearance angles. For all tested configurations, the material’s elastic spring back increases in intensity as wear progresses which, in combination with the decreasing clearance angle, is the main reason for high thrust forces.

Geometric empirical modelling of forces influenced by the cutting edge microgeometry in orthogonal cutting of unidirectional CFRP

In optimising the cutting of carbon fibre reinforced plastics (CFRP), increasing emphasis is placed on the cutting edge microgeometry. A significant challenge lies in understanding the engagement conditions between tool and workpiece, influencing tool wear mechanisms and performance. This paper aims to provide a more in-depth insight into the influence of cutting parameters on process forces when applying ideally rounded cutting edges in orthogonal cutting. A geometric empirical process model is developed for calculating the cutting force and the passive force, considering the cutting edge radius, the uncut chip thickness, and the fibre cutting angle. As a result, the minimum uncut chip thickness was determined, and process forces were calculated.

Effects of cutting edge radius on cutting force, tool wear, and life in milling of SUS-316L steel

Cutting edge micro-geometry plays an important role in machining operations. An appropriate shape and size of the cutting edges improve wear resistance, tool life, and process reliability. This study presents an experimental exploration to understand the rounded cutting edge of solid carbide end mills with CrTiAlN coating on milling SUS-316L steel, and the tool performance in terms of cutting force, tool wear, and tool life is investigated. The designed cutting edge radius (CER) from 4 up to 15 μm is prepared by drag finishing (DF). The results have indicated that the CER are remarkably significant on the cutting performances. With the CER increased from 4 to 15 μm, the cutting force Fc and feed force Ff increased 23% and 56% at uncut chip thickness h = 0.2 mm, respectively. The wear test results showed that chipping is the primary failure of milling cutter. The tool wear mechanism was depicted through scanning electron microscopy (SEM) and energy-dispersive spectrometer (EDS) analysis. In conclusion, the highest tool life was obtained with nominal CER of 12 μm in milling of SUS-316L steel.

Production-Related Surface and Subsurface Properties and Fatigue Life of Hybrid Roller Bearing Components

By combining different materials, for example, high-strength steel and unalloyed structural steel, hybrid components with specifically adapted properties to a certain application can be realized. The mechanical processing, required for production, influences the subsurface properties, which have a deep impact on the lifespan of solid components. However, the influence of machining-induced subsurface properties on the operating behavior of hybrid components with a material transition in axial direction has not been investigated. Therefore, friction-welded hybrid shafts were machined with different process parameters for hard-turning and subsequent deep rolling. After machining, subsurface properties such as residual stresses, microstructures, and hardness of the machined components were analyzed. Significant influencing parameters on surface and subsurface properties identified in analogy experiments are the cutting-edge microgeometry, S¯, and the feed, f, during turning. The deep-rolling overlap, u, hardly changes the residual stress depth profile, but it influences the surface roughness strongly. Experimental tests to determine fatigue life under combined rolling and rotating bending stress were carried out. Residual stresses of up to −1000 MPa, at a depth of 200 µm, increased the durability regarding rolling-contact fatigue by 22%, compared to the hard-turned samples. The material transition was not critical for failure.