Tool Rake Face Research Articles

Flank milling of compliant workpieces with chamfered tools

The use of chamfered tools is widely spread in cutting processes. Prior investigation show, that a chamfer on the rake face of a milling tool can increase the stability of cutting processes significantly due to a contact between the chamfer surface and the workpiece and the resulting damping forces. In addition to higher process stability, it is possible that the chamfer shows positive effects on the machined surface as well. A sufficient chamfer length can cut off the feed marks on the machined surface, but also damping effects on the process vibrations can lead to a better flank surface when milling compliant parts or tools as well. This paper describes an approach of simulation of machining of the flank surface with consideration of the chamfer geometry. In the experimental and simulative investigations it was found that by the reduction of extensive workpiece vibrations, the chamfer does have positive effect on the flank surface quality due to a contact between the chamfer and the workpiece. Furthermore, this contact does apparently occur earlier than a theoretical consideration would predict from the kinematics of the process. With increase of the chamfer length on the other hand, also augmented appearance of smearing effects on the surface, which decrease the surface quality, was observed.

Cutting data correction in Inconel 718 turning

The paper presents research work concerning difficult-to-cut materials turning and chipbreakers reliability in local operating features. Inconel 718 alloy was used as a sample material and two different chipbreakers were tested. The aim of the research was to check the efficiency of chipbreakers in the area of applications recommended by tool manufacturers. As a result, the algorithm for cutting data selection and correction which combines experiments and simulation processes concerning chip breakage effectiveness was built. To estimate chip forms in tests, the visual system equipped with a high-speed camera was used. The cutting forces measuring system provided information for verification of simulation results. The simulation based on the FEM was applied to estimate chip groove filling. Distributions of temperature and stresses on the tool rake face in the function of distance from the cutting edge were calculated. The paper gives recommendations for cutting data correction to achieve acceptable chip forms.

Analysis of transient average tool temperatures in face milling

The increased tool temperature has great effect on tool life, machining efficiency and even the quality of the products in face milling. The objectives of this study are to predict the transient average tool temperatures under different cutting conditions with fixed cutting velocity and metal removal rate, and investigate the evolution of tool temperature with cutting condition. Finite element simulations of orthogonal metal cutting are performed so as to predetermine the evolution process of the heat source on the tool rake face. An analytical model is proposed to calculate and analyze the tool temperatures under nine different cutting conditions. The results reveal that the minimum transient average tool temperature can be acquired by adopting suitable cutting condition. The proposed theoretical method provides insight into the complex evolution of tool temperatures. It also provides information for the search for the optimum cutting condition under which the longest tool life can be obtained.

A new experimental methodology to analyse the friction behaviour at the tool-chip interface in metal cutting

This paper investigates a new test to analyse the friction behaviour of the tool-chip interface under conditions that usually appear in metal cutting. The developed test is basically an orthogonal cutting process, that was modified to a high speed forming and friction process by using an extreme negative rake angle and a very high feed. The negative rake angle suppresses chip formation and results in plastic metal flow on the tool rake face. Through the modified kinematics and in combination with a feed velocity that is five to ten times higher than in conventional metal cutting, the shear and normal stresses are only acting in a simple inclined plane, allowing to calculate the mean friction coefficient analytically. In addition, the test setup allows to obtain the coefficient of friction for different temperatures, forces and sliding velocities. Experiments showed, that the coefficient of friction is strongly dependent on the sliding velocity for the example workpiece/tool material combination of C45E+N (AISI 1045) and uncoated cemented carbide.

Study on Fracture Performance of <i>In Situ</i> Growth Whisker Toughened Composite Ceramic Tool

Three kinds of whisker toughened composite ceramic tools were prepared by carbothermal reduction process and their fracture performance was investigated in cutting the quenched 45 steel. The results suggest that the ratio of C to N has an effect on the fracture resistance of ceramic tool, and the whisker in tool material can inhibit the crack propagation and desquamation of grains. At the low cutting speed, the main fracture mode was conchoidal desquamation on the tool rake face and severe oxidation wear and some diffusion wear happened. At the medium cutting speed or high cutting speed, a combination of mechanical load and thermal load applied on the tool and adhesion was caused between workpiece material and tool material, and so the fracture mode was break-off of the cutting edge.

Image Based Analysis Evaluation of the Elements of Secondary Adhesion Wear in Dry Turning of Aluminum Alloys

Minimizing downtime in machine tools is one of the factors that determine the performance increase of the production processes involved. This increase can be considered from different points of view: economic, energetic and environmental. Machining processes can be stopped by needing to change the tool as a consequence of the loss of their initial properties due to the wear process that suffer during machining. One of the wear processes which takes place in a wider range of temperatures in the machining of metal alloys is the adhesion wear, and specially in the case of light alloys, secondary adhesion wear, which can be placed in the tool rake face as a layer (Built-Up Layer, BUL) and in the tool edge (Built-Up Edge, BUE). This paper analyzes the influence of cutting parameters on the secondary adhesion wear effects in the dry turning of UNS A92024 (Al-Cu) alloy.

Experimental Study on High-Speed Turning of Free-Cutting Steel AISI 12L14 Using Multi-Layer Coated Carbide Tools

AISI 12L14 as a typical free-cutting steel has been widely employed in machinery, energy and metallurgy fields due to its excellent machinability. This research was concerned with the experimental investigation on high-speed turning of AISI 12L14 in terms of cutting force and tool wear with multi-layer (Al2O3/TiCN) CVD coated carbide tool. Results showed that: Depth of cut ap had the dominant effect on the main cutting force, and feed rate f followed. Increase of cutting speed vc was observed to decrease the turning forces. Optimal factor level combination (vc=500m/min, f=0.05mm/r and ap=0.5mm) was obtained through the method of extremum difference analysis. The cutting tool was observed to form sulfide lubricant zone along its rake and flank faces. Ascribed to the presence of sulfide lubricant zone the tool can obtain excellent protection and minor flank wear in the entire turning process. Crater wear was observed occurring on tool rake face and no BUE was found along the cutting edge. In addition, tool flank face suffered abrasive wear and adhesive wear.

Fluid Characteristics of Material Flow in High Speed Metal Cutting Process

In high speed metal cutting momentum would be large and the strain rate can be exceedingly high, the viscosity of material must take into account in studying the chip deformation. Model the high speed machining as fluid flow is much better than as solid. A laminar flow method is applied in this paper to analyze the velocity distribution, the pressure distribution, the temperature distribution and the strain rate distribution of high speed metal cutting. Analytical results showed that a speed stagnation point is located at some distance from the tool tip on the tool rake face, on which the maximum value of the pressure occurs, with zero speed; its location influences the life of the tool and the quality of the finished surface. The value of the pressure decrease along the rake face and reaches zero at some point away from the tool tip, which is the point of separation of the chip from the tool; The value of strain rate get a rapid increase from the tool tip to the free surface corner then decreased outwards.

Influence of Cutting Parameters and Tool Geometric Angles on TC4 Titanium Alloy Chip Shape

To select reasonable cutting parameters, improve the processing surface quality, and extend the tool life, this paper uses four solid carbide end milling tools to process TC4 titanium alloy, and analyses the influence of the difference cutting parameters and the geometric angles to chip shape. The experiment results indicate that the degree of serrated chip shape is increased by increasing the feed rate under the condition of certain spindle speed. But the degree of serrated chip shape may be decreased by the adoption of small axial and radial depth, or bigger rake angle and smaller helix angle. Select larger rake angle, cutting edge is sharp, the metal deformation of cutting layer is small, which can reduce the friction force when chip flowing through the tool rake face, so that the cutting force and cutting temperature decreases accordingly.The greater the helix angle is, the worse the chip removal conditions is, and the degree of serrated chip becomes larger, the blade is more sharp, easily crack, and the tool life decreases. So relatively small helix angle is better. The choice of angles is interrelated with each other, the selection of some angle separately cannot get the desired reasonable value.

A slip-line approach to the machining with rounded-edge tool

In this paper, a new slip-line model approach for modeling the orthogonal cutting process with rounded-edge tools and its associated hodograph are proposed. This model consists of eight regions, which include a dead region in front of the rake face of tool. Dewhurst and Collins’s matrix technique for numerically solving the slip-line problem is employed in the mathematical formulation of the new model. The experimental results show that a small dead region is seen in front of the rake face of tool during cutting with a rounded-edge cutting tool. The unknown slip-line angle pair was solved depending on the force data obtained experimentally and variation of the subregions with cutting edge radius was determined. Cutting force, thrust force, and dead zone grow as cutting edge radius increases in cutting edge-radiused tools.

An Investigation of Lateral Surface Hardness and Related Cutting Forces in One-Directional Ultrasonic-Vibration Assisted Turning

The experimental investigation of UAT shows that the movement of cutting tool edge relative to the workpiece results from the cutting speed, feed speed and tools vibration in tangential direction affects the lateral machined surface of workpiece and leaves a repeating pattern of toothed regions on it. In UAT process, because of constant feed rate of tool toward workpiece, the cutting tool never separates from workpiece, though the tool rake face may separate periodically from chip in every cycle of vibration. This results in an increase in the surface hardness of the lateral machined surface in comparison with conventional turning (CT). The results of the present study confirm the advantage of UAT as far as the lower cutting force is concerned compared with CT. The higher surface hardness of the lateral surface observed in UAT causes the maximum cutting force to increase but the average force decreases with respect to CT.

Chip/Tool Interaction during Dry Machining of the TA6V Alloy

During chip formation, material is subjected to high deformations and high strain rates which generate high pressures and temperatures. Cutting fluids have an important role but produce many constraints: cleaning of parts, environment quality degradation, cost increase, diseases as identified by the European Agency for Safety and Health at Work. Dry machining is one of the future challenges although its implementation remains delicate, in particular for TiAl6V alloy. This paper aims at correlating the contact conditions at the tool/chip interface with the tool wear to understand the wear mechanisms of carbide tools in dry machining. Numerical simulations, experimentally validated, allow pointing out that the temperature distribution at the tool/chip interface depends on chip type (continuous, serrated). For continuous chips, the temperature is fairly uniform and stationary throughout the interface. For segmented chips, a cold zone between two temperature peaks is observed and moves along the tool rake face during the formation of a chip segment. The evolution of the normal stress at the interface is similar for both types of chips at the beginning of the localization phenomenon. These pressure and temperature fields allow the titanium to diffuse into the tungsten carbide and form the mixed carbide (Ti, W)C, which is very sensitive to oxidation above 500°C. This could explain the attrition of the tool, due to the brittleness of the oxycarbides. Contact conditions and tool wear are finally correlated.

A Slip-Line Approach to the Micro-Cutting Process with a Rounded-Edge Tool

The effect of tool edge roundness attracts growing attention due to increasing applications of precision, micro-and nanomachining technologies. A new slip-line model and its associated hodograph are proposed for cutting with a rounded-edge tool in this paper. New model considers stagnant metal region called as dead metal zone formed in front of the rake face of tool during cutting process. Dewhurst and Collinss [ matrix technique for numerically solving the slip-line problem is employed in the mathematical formulation of the new model. The unknown slip-line angles were solved depending on the force data obtained from experiments and variation of the sub-regions with cutting edge radius was determined.

An experimental investigation of temperature and machinability in turning of compacted graphite irons

The life and the performance of an insert in metal cutting are mainly dependent on the heat that is generated in the contact zones on the tool rake face with chips and on the flank face with the transient and machined surfaces. According to tool life standard, the wear on the flank face is usually taken as a decision for tool life. This occurs because of contact stresses, temperature and friction between tool workpiece contacts. Hence, knowledge of temperature on the flank face becomes important. The temperature on the flank face has been measured in this work for different CGI materials having different microstructure and physical properties in a turning operation. It has been seen that there is no significant difference of flank temperature, while machining different CGI materials having hardness from (140 to 236 HBW). For temperature measurement, special inserts integrated with gold-platinum thermocouple on the flank face were used. It has been noticed that the materials having 31% resultant cutting force difference and six to eight times tool life difference have almost same temperature on the flank face measured at different distances from the edge line of the insert.

An Investigation of Lateral Surface Hardness and Related Cutting Forces in One-Directional Ultrasonic-Vibration Assisted Turning

The experimental investigation of UAT shows that the movement of cutting tool edge relative to the workpiece results from the cutting speed, feed speed and tools vibration in tangential direction affects the lateral machined surface of workpiece and leaves a repeating pattern of toothed regions on it. In UAT process, because of constant feed rate of tool toward workpiece, the cutting tool never separates from workpiece, though the tool rake face may separate periodically from chip in every cycle of vibration. This results in an increase in the surface hardness of the lateral machined surface in comparison with conventional turning (CT). The results of the present study confirm the advantage of UAT as far as the lower cutting force is concerned compared with CT. The higher surface hardness of the lateral surface observed in UAT causes the maximum cutting force to increase but the average force decreases with respect to CT.

A Slip-Line Approach to the Micro-Cutting Process with a Rounded-Edge Tool

The effect of tool edge roundness attracts growing attention due to increasing applications of precision, micro-and nanomachining technologies. A new slip-line model and its associated hodograph are proposed for cutting with a rounded-edge tool in this paper. New model considers stagnant metal region called as dead metal zone formed in front of the rake face of tool during cutting process. Dewhurst and Collinss [ matrix technique for numerically solving the slip-line problem is employed in the mathematical formulation of the new model. The unknown slip-line angles were solved depending on the force data obtained from experiments and variation of the sub-regions with cutting edge radius was determined.

切削工具すくい面上摩擦分力の予測法に関する一試案

切削工具すくい面上摩擦分力の予測法に関する一試案

Cutting temperature prediction in high speed machining by numerical modelling of chip formation and its dependence with crater wear

A study through a finite elements model using the AbaqusTM code is conducted to predict the interface cutting temperature and its dependence with the crater wear mechanism. Unlike the most previous researches, this work is focused on the domain of the high speed machining above 20m/s. The mechanical and thermal parameters that influence the temperature distribution at the tool rake face are analysed in details. A method based on some analytical preliminary calculations is proposed to determine the adequate values of the friction shear stress and the heat partitioning factor between the tool and the chip. A correlation between specific experiments and simulations is verified in the case of orthogonal cutting of mild steel up to a velocity of 60m/s. Cutting tests were carried out on a ballistic device equipped with an intensified CCD camera to measure the temperature field into the chip. A good agreement is found with respect to measurements of cutting forces, contact length and temperature. As application, a wear model is coupled with the finite element model through an iterative schema. At each step of calculation, the contact pressure and temperature are updated while the crater grows.

An investigation of multilayer coated (TiCN/Al2O3-TiN) tungsten carbide tools in high speed cutting using a hybrid finite element and experimental technique

Temperature and heat distribution in metal cutting are key factors that influence dry and/or high speed machining processes. In particular, during dry high speed machining these factors can lead to premature tool failure resulting in higher process cost. In this work, a hybrid methodology was employed in which finite element modelling (FEM) and experimental tests were used to evaluate the performance of multilayer functionally graded coated tools on the basis of heat partition into the tool and growth of flank wear. Cutting tests were conducted on AISI/SAE 4140 low carbon steel using multilayer coated tungsten carbide tools with TiCN/Al2O3 coatings on the rake face and TiCN/Al2O3/TiN coatings on the flank face. The tools were restricted contact length with a grooved profile. Cutting tests were conducted over a wide range of cutting speeds ranging from 200 to 879 m/min. The prediction of heat partition was carried out by matching finite element simulated temperatures to experimentally measured temperatures at 12 separate points on the tool. The study reveals that by using the functionally graded coating layouts, a significant reduction in heat distribution into the cutting tool can be achieved. Furthermore, the results suggest that in addition to the coating system, the tool rake face profile is also important in controlling heat flux and reducing flank wear.

Micro-texture at the coated tool face for high performance cutting

This paper describes the effect of micro surface texture on the lubrication conditions at the tool rake face in machining aluminum alloy. For this purpose, four types of micro surface texture were fabricated at the tool faces of cemented carbide through spattering, photolithography and wet etching, and the micro-textured tool faces were coated with diamond like carbon (DLC) or TiN. Then, orthogonal cutting experiments of aluminum alloy were conducted using the coated tools with and without micro-texture. The normal and friction forces and the coefficient of friction were obtained from the measured cutting forces. In addition, tool surface conditions were inspected with a CCD microscope after machining. As a result, it was found that parallel type and square-dot type of micro-textures improved effectively the lubrication conditions in machining aluminum alloy A6061-T6. It was also found that micro-texture was likely to improve the lubrication conditions more effectively as the pattern of texture became smaller and deeper.