Tool Radius Research Articles

Machining Technology and PVD Coatings for Milling Thin Structural Parts of Inconel 718

To improve the machining process of thin, susceptible structural components made of Inconel 718, the milling process for trochoide roughing and finishing was analyzed. In addition to the validation of cutting material, tool micro-geometry and the coolant supply, new PVD hard coatings including the coating post-processing were developed. These PVD coatings were used to modify the heat distribution during the cutting process and to improve the tool life. To reduce machining effort, in coating development micro-impact tests and vibrational wear tests at higher temperatures were used to identify trends with regard to the fatigue behavior of the coatings and the affinity for built-up edges. Optimized cutting results for both trochoide roughing and finishing can be reached by the combination of a carbide substrate with an average grain size of approx. 0.8 µm and a cobalt content of 10% as well as a cutting edge radius of the milling tools of about 8 µm. A suitable coolant and the effective coolant supply also have a very high influence on the tool life and the wear behavior of the milling tools. During machining tests, the convenient PVD coatings were also determined. Due to the longer tool life, a TiSiN-based coating shows the best results for rough milling. In finish milling processes, boron-containing coatings lead to reduced tool wear and the lowest surface roughness of the machined structural parts.

Study on the crack formation mechanism in nano-cutting of gallium arsenide

Gallium arsenide is a typical brittle material, and crack formation is one of the most serious issues in the nanometric processing. This paper majors in studying crack formation mechanism in nano-cutting of gallium arsenide. In the molecular dynamics simulation of nano-cutting process, the main damage changes from dislocation to phase transformation with the increasing cutting speed. The amount of cracks increases with the higher cutting depth, and the deformation mode turns from ductile to a combination of ductile and brittle. Cracks appear at the boundary between amorphous layer and single crystal in the subsurface and tensile stress concentration is observed around the crack tip. The crack area is polycrystalline in the models with large tool radius. Brittle-ductile transition is observed by taper-cutting experiment of gallium arsenide, and the cutting depth is measured as 25 nm where the initial surface crack forms, which proves the low brittle-ductile transition depth of gallium arsenide. Micro cracks and polycrystals are found in the subsurface of transition area by cross section TEM, which is consistent with simulation results.

Prediction of Tool Force in Two Point Incremental Forming by Slab Analysis

Two-Point Incremental Forming (TPIF) method is a novel technique for producing free form shell parts. The main purpose of this study is to analyze the TPIF process, and, by approximate calculation, to find the force applied to the tool. One of the limitations of an incremental forming process is that during this process force applied to the tool is born by the machine. In this research, an equation for approximate prediction of the force applied to the tool is presented using the values of the yield stress of the sheet, friction coefficient, tool radius and thickness of the sheet; hence, the applied force can be calculated. By increasing the forming angle, the amount of the created local strain increases and the change in thickness and the force applied to the tool is enhanced. However, by increasing the angle of punch wall, less compressive stress is applied to the metal sheet due to the reduction in contact between the surface of the tool and punch wall. Analytical equations presented are validated by the results from experimental tests.

Pengaruh Parameter Pemotongan Dan Nose Radius Pahat Insert W-Style Pada Pembubutan Baja S45c

In the manufacturing industry, the cutting process, especially lathes, has developed rapidly, one of which is in the rail transportation industry sector. The purpose of this study was to determine the effect of cutting parameters and the nose radius of the W-style insert tool on the level of surface roughness in the turning process of S45C steel. This research uses experimental research methods. In this study, using a variation of cutting parameters and nose radius. Variations in cutting parameters using cutting speeds of 195 Rpm, 300 Rpm and 440 Rpm. Variation of the depth of cut 1 mm and 2 mm. Variation of feed speed 0.1 mm / rev, 0.2 mm / rev and 0.3 mm / rev. While the variation of the nose tool radius for inserting W-style is 0.4 mm and 0.8 mm. After turning the surface roughness test was carried out using the Surface Roughness Tester. The results of this study indicate that the increasing cutting speed and nose radius of the insert tool, decreasing feeding velocity and cutting depth results in good surface quality.
 
 Keyword: W-series insert tool, nose radius, surface roughness.

Analysis of the influence of tool radius on single crystal silicon cutting process based on Molecular dynamics

In this paper, a molecular dynamics method is used to construct a simulation model for cutting single crystal silicon with a tool. Through the analysis of phase transition, instantaneous atomic position, temperature, Wigner-Seitz defect and other variables, the influence of tool radius on material deformation is studied. The results show that in the process of cutting single crystal silicon, the contact area between the cutting edge and the single crystal silicon workpiece is the main area of cutting heat generation, and the phase change process from the atomic crystalline state to the amorphous state is reflected in the cutting process of different tool radii The difference is that the amorphous atoms are removed in the form of chips during the cutting process of the sharp-angle tool, while the amorphous atoms are further compressed directly under the tool in the round-angle tool, causing subsurface damage. The chip removal mechanism of sharp tools is shear, and the chip removal mechanism of round tools is shear and extrusion. As the radius of the tool increases, the more atoms are compressed directly below the tool, the worse the surface quality of the machined surface.

Numerical and experimental investigation of tool geometry effect on residual stresses in orthogonal machining of Inconel 718

Residual stress has become more important than ever with the increasing performance requirement of components especially for those applied in safety-critical areas. As the machining process is fundamentally correlated with the acquired component properties, it is essential to fully understand the formation mechanism of residual stresses in the cutting process and its influence on the performance of the component. This paper presents results based on numerical and experimental analysis on the effect of tool geometry on thermal-mechanical load and residual stresses in orthogonal machining Inconel718 alloy. The Coupled Eulerian-Lagrangian (CEL) method is used to simulate the effect of tool geometry on temperatures, forces, equivalent plastic strains, and residual stresses. The local normal/tangential stress is introduced to determine the degree of the tensile plastic deformation induced by the tool. It is observed that a negative rake angle and a sharp edge radius tool tend to generate more compressive stress on the machined surface than the ones generated with positive rake angle tools and/or lager edge radius. Besides, an increase in flank wear produces less magnitude of compressive stress in subsurface due to a decreased local normal stress caused by increased flank contact length.

Ultra-precision machining of a large amplitude umbrella surface based on slow tool servo

Due to its excellent optical performance and system integration property, micro-nano structure function surface has been widely used in optical apparatus and energy collection equipment. But using traditional processing method can’t obtain a mirror-like surface with high form accuracy and low roughness for sake of its complex micro-nano structure. In this paper, a large amplitude umbrella surface is special designed and single point diamond turning (SPDT) technology based on slow tool servo (STS) is used for umbrella surface machining. The tool path generation, tool radius compensation and tool geometry optimization are detailed for fabricating the desired surface. A new method combined with constant angle and analytical mathematical optimization is proposed for tool path optimization. A large amplitude umbrella surface with the maximum amplitude 0.2 mm and period 8 per cycle is designed, and the machining experiment is carried out on Nanoform 250 ultra-precision machine tool. From the form accuracy 1 μm in surface residual error and 279.12 nm in RMS and the surface roughness 230.10 nm in Ra for the machined surface, it can be seen that a large amplitude umbrella surface is easily fabricated by SPDT under STS controlling.

Robustness of the HFMI techniques and the effect of weld quality on the fatigue life improvement of welded joints

Robustness of HFMI treatment in different weld qualities according to ISO 5817 was studied, and fatigue testing of the treated samples was carried out in order to investigate the effect of the weld quality prior treatment. The results show that HFMI-treated welds with weld quality level D shows fatigue life improvements that fall within the IIW recommendations for HFMI. No significant influence from the HFMI operator or HFMI equipment on the fatigue life was found. However, the scatter in fatigue testing results varied with HFMI operator and indicated that different HFMI operators could produce consistent treatment results. A considerable effect on fatigue life from HFMI tool radius was found, where the 2-mm tool radius showed considerably greater fatigue life compared with the 1.5-mm tool radius. According to IIW (Marquis and Barsoum 2016), for steel grade SY = 700 MPa, the fatigue strength recommendation is FAT 160 (m = 5) for transverse stiffener–welded joints with as-welded quality B according to ISO 5817 (ISO/TC 44/SC 10 2011), prior to treatment. It can be observed in the current study that fatigue-tested HFMI-treated welded joints, welded with weld quality D, are in good agreement with the IIW recommendations.

Influence of Diamond Smoothing on the Surface Layer of a 30ХГСН2А-ВД High-Strength Steel Workpiece

The influence of the smoothing force, the tool radius, the machining speed, and the supply on the distribution of azimuthal and axial residual stress, the microhardness, and the depth of strain hardening is analyzed for the machining of 30ХГСН2А-ВД steel by ASB-1 synthetic diamond. Empirical equations for these parameters are presented.

A comparative analysis of characteristics of cutting forces at micro-milling of hardened steels

Micro-milling is one of the most important technologies to produce miniature components. Mainly due to the size reduction, the process has many special characteristics, such as the relatively large tool run-out, the relatively large deformation and the cutting edge radius of the micro-milling tool. The cutting force is often correlated to the phenomena mentioned above, its analysis is therefore often required. The main objective of the present paper is to analyse and compare the characteristics of cutting forces in micro-milling of different hardened steels. A systematic series of experiments were conducted on a hardened AISI H13 hot-work tool steel and a Böhler M303 martensitic corrosion resistance steel. The hardness of both materials is 50 HRC. A 500 µm diameter two fluted carbide micro end mill and a five-axis micromachining centre were applied. The effects of the cutting parameters are analysed by the analysis of variance (ANOVA). Experimental results show that the workpiece material has a significant influence on the cutting forces.

High-Precision Cutting Edge Radius Measurement of Single Point Diamond Tools Using an Atomic Force Microscope and a Reverse Cutting Edge Artifact

This paper presents a measurement method for high-precision cutting edge radius of single point diamond tools using an atomic force microscope (AFM) and a reverse cutting edge artifact based on the edge reversal method. Reverse cutting edge artifact is fabricated by indenting a diamond tool into a soft metal workpiece with the bisector of the included angle between the tool’s rake face and clearance face perpendicular to the workpiece surface on a newly designed nanoindentation system. An AFM is applied to measure the topographies of the actual and the reverse diamond tool cutting edges. With the proposed edge reversal method, a cutting edge radius can be accurately evaluated based on two AFM topographies, from which the convolution effect of the AFM tip can be reduced. The accuracy of the measurement of cutting edge radius is significantly influenced by the geometric accuracy of reverse cutting edge artifact in the proposed measurement method. In the nanoindentation system, the system operation is optimized for achieving high-precision control of the indentation depth of reverse cutting edFigurege artifact. The influence of elastic recovery and the AFM cantilever tip radius on the accuracy of cutting edge radius measurement are investigated. Diamond tools with different nose radii are also measured. The reliability and capability of the proposed measurement method for cutting edge radius and the designed nanoindentation system are demonstrated through a series of experiments.

An analytical and experimental investigation considering the effect of material flow velocity on tensile strength of a steel alloy joint produced by friction stir welding process

In this paper, the effects of linear speed, rotational speed, and tool radius of the pin and shoulder are investigated on the material flow velocity in friction stir welds. To obtain the maximum material flow velocity by an analytical method, a suggested relation is introduced for the rotational speed and tool optimum radius. The derived relation is based on the assumption of a velocity field in the stirring region. Besides, the effect of the linear speed on material flow velocity is investigated based on continuity and momentum equations. Finally, by using the experimental method and checking the mechanical properties of the welded parts obtained with different rotational speed, linear speed, and tool dimensions, the proposed analytical model is validated. The results indicate that in the friction stir welding process, the significant component effect on the stirring process is generated through the tool pin radius size. Besides, increasing the material flow velocity in the boundary layer increases the yield and ultimate strength of welds. To achieve the high-quality welds, rotational speed and other tool dimensions must be selected considering the equation extracted from the analytical method. Also, to make the maximum life for the pin and its components in friction stir welding of high melting point metals such as steel alloys, the operation is adjusted at a lower linear speed to prevent the destruction of the tool and improve the quality of the joint.

Modeling Dynamic Stability and Cutting Forces in Micro Milling of Ti6Al4V Using Intermittent Oblique Cutting Finite Element Method Simulation-Based Force Coefficients

Abstract Tool breakage is a significant issue in micro milling owing to the less stiffness of the micro tool. To cope up with such limitation, precise predictions of dynamic stability, and cutting force have the utmost importance to monitor and optimize the process. In this article, dynamic stability and cutting force are predicted precisely for micro milling of Ti6Al4V by obtaining force coefficients from a novel 3D intermittent oblique cutting finite element method (FEM) simulation considering the influence of tool run out. First, the stability model is modified by incorporating the appropriate values of limiting angles obtained analytically accounting the trajectories of the flutes due to tool run out. This stability model is utilized to select chatter-free parametric combinations for micro milling tests. Next, an improved cutting force model is developed by incorporating the force coefficients obtained from oblique cutting simulation in the mechanistic model and differentiating the whole machining region into three distinct region considering size effect. The force model also considers the effect of increased edge radius of the worn tool, run out, elastic recovery, ploughing, minimum undeformed chip thickness (MUCT), and limiting angles, cumulatively. The proposed dynamic stability and cutting force models based on the oblique cutting simulation show their adequacy by predicting the stability limit and cutting force more precisely, respectively, as compared to those obtained by orthogonal cutting simulation. Besides, the proposed force model for the worn tool is found to be viable as it is closer to the experimental forces, whereas force model without the incorporation of tool wear underestimated the experimental forces.

Optimization of Milling Parameters for Energy Savings and Surface Quality

Enhancing energy efficiency and product quality by means of optimal inputs is a cost-effective solution, as compared to the drastic investment. This paper aims to optimize the machining inputs to enhance energy efficiency (EF) as well as the power factor (PO) and decrease the surface roughness (Ra) for the milling process. The factors considered are the feed (f), depth of cut (a), milling speed (V), and tool radius (r). The machining operations were executed on the vertical milling under the dry condition for the stainless steel 304. A type of neutral network entitled the radius basic function (RBF) was used to render the relationships between milling inputs and performances measured. The adaptive simulated annealing (ASA) algorithm was applied to obtain the optimal values. The outcomes indicated that the milling responses are primarily influenced by a, f, V, and r, respectively. The reduction in Ra is approximately 39.18%, while the improvements in EF and PO are around 22.61% and 26.47%, respectively, as compared to the initial parameter settings. The explored findings are expected as a prominent solution for the industrial application of the dry machining. The combination of the RBF models and ASA could be considered as an efficient approach for modeling dry machining processes and generating reliable as well as feasible optimal results.

Ultraprecision laser-assisted diamond machining of single crystal Ge

In this paper we present an experimental study on ultraprecision machining (UPM) of single crystal Ge using the μ-LAM process. The material is oriented with the cutting plane normal to the <111> direction. It is shown that increased hydrostatic pressures on the surface during cutting by increasing the tool radius and negative rake angle can aid in enhancing ductile material removal from the surface. It is shown that the cutting performance can be increased by approximately 400% using the optimal tool geometry. It is also shown that the optimal tooling geometry with a steep negative rake angle, i.e. −65°, is capable of producing repeatable surface form and finish over long cutting distances. Finally, it will be shown that the laser beam used for μ-LAM, with the right amount of power, produces surfaces that are under less post machining residual stresses.

A novel multi-step strategy of single point incremental forming for high wall angle shape

Single point incremental forming (SPIF) is a die-less manufacturing technology using a numerical controlling system for complex and customized parts. However, single-step SPIF cannot achieve high wall angle shapes due to the formability limit of the material. As wall angle gets larger, local thinning becomes severe, and cracking occurs easily. Generally, a multi-step strategy is used to get a hard-to-form deep drawing shape. However, inappropriate multi-step strategies can cause a stepped feature (corrugation). In this study, a novel parameterized multi-step strategy is proposed to solve the local thinning and stepped feature issues of forming high wall angle shape. Both experimental and simulation results showed this strategy not only improves the formability of a high wall angle, by avoiding over-thinning in the local region and redistributing the thickness of the material, but also minimizes geometric deviation by stepped feature. The multi-step strategy made the local thickness increase from 0.47 mm to 0.68 mm, preventing both cracking observed in a single-step strategy and the occurrence of the stepped feature. With the good agreement between experimental and simulation results, simulations with different parameters in a parameterized multi-step strategy were carried out to compare thickness distribution at each step, the stepped feature at the bottom and the ductile failure tendency. The comparison reveals that the locally large plastic strain, which was caused by the mismatch between the tool radius and vertical displacement, is the main reason for uneven thickness distribution, obvious stepped feature, and high failure tendency. With appropriate parameters, a multi-step strategy results in a more uniform thickness distribution, higher geometric accuracy, and lower failure tendency.

Ball End Mill—Tool Radius Compensation of Complex NURBS Surfaces for 3-Axis CNC Milling Machines

In order to extend the 2D-TRC (tool radius compensation) function of 3-axis CNC milling machines to ball end mills (BEMs), a new TRC named BEM-TRC is proposed to achieve successful milling of complex surfaces without over-cut. The implementation of the BEM-TRC for complex surfaces depicted in NURBS model is divided into three steps. The first one is to search the cutting point (CP) on a NURBS surface using equi-arc length interpolation in u or v direction. The second one is to accomplish BEM-TRC at the CP through offsetting the CP to the cutter center point (CCP) of a BEM along the normal vector at CP. The third one is to compute the cutter location point (CLP) of the BEM according to the BEM-CCP. The simulation and experiment verifies that the BEM-TRC is feasible and effective, and can avoid over-cut phenomenon successfully. The BEM-TRC extends the ability of the traditional 2D-TRC function, and makes 3-axis CNC milling machines to accomplish the milling process of complex NURBS surfaces.

Local Laser Particle Fusion: Fusing of Hard Particles for the Reduction of High Contact Pressures in MMC Tool Surfaces

Lubrication-free deep drawing with metal matrix composite (MMC) tool surfaces leads to scores and grooves due to particle penetration into the formed sheet metal, and results in high local contact pressure in the radius of the deep drawing tool. To improve on this, the ratio of contacting area to total area must locally be increased in high-load regions of the tool surface. Multi-stage laser melt injection (LMI) and local laser particle fusion (LLPF) were carried out to increase the hard particle content of the MMC tool surfaces. LLPF is a novel two-step LMI process whereby hard particles are locally fused together under additional powder feeding after a regular LMI. The resulting nugget was shown to grow in height and width with an increase in the pulse duration. The substrate temperature prior to the particle fusion had an influence on the defect-free nugget growth. Whilst the chemical composition of the fused tungsten carbide (FTC) nuggets was similar to FTC particles, their hardness was slightly reduced compared to literature values for tungsten carbide. For the first time, FTC nuggets could be successfully applied on MMC tool surfaces to realize an increased hard coating area.

Effect of diamond burnishing parameters on the state of the processed surface layer of billets made of high-strength "30ХГСН2А-ВД" steel

The influence of the burnishing force, tool radius, processing speed and feed on the distribution of circumferential and axial residual strses, microhardness and the depth of strain hardening in the surface layer when pr ssing of "30ХГСН2А-ВД" steel with synthetic diamond "ACB-1" is considered. Empirical dependencies determining these parameters are given. Keywords diamond burnishing, strain hardening depth, circumferential residual stresses, axial residual stresses, microhardness. shvecovalexey@yandex.ru, skuratov.sdl56@yandex.ru

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

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