Tool In High Speed Milling Research Articles

Three-Stage Wiener-Process-Based Model for Remaining Useful Life Prediction of a Cutting Tool in High-Speed Milling.

Tool condition monitoring can be employed to ensure safe and full utilization of the cutting tool. Hence, remaining useful life (RUL) prediction of a cutting tool is an important issue for an effective high-speed milling process-monitoring system. However, it is difficult to establish a mechanism model for the life decreasing process owing to the different wear rates in various stages of cutting tool. This study proposes a three-stage Wiener-process-based degradation model for the cutting tool wear estimation and remaining useful life prediction. Tool wear stages classification and RUL prediction are jointly addressed in this work in order to take full advantage of Wiener process, as this three-stage Wiener process definitely constitutes to describe the degradation processes at different wear stages, based on which the overall useful life can be accurately obtained. The numerical results obtained using extensive experiment indicate that the proposed model can effectively predict the cutting tool’s remaining useful life. Empirical comparisons show that the proposed model performs better than existing models in predicting the cutting tool RUL.

Experimental Study on High-Speed Milling of SiCf/SiC Composites with PCD and CVD Diamond Tools.

Silicon carbide fiber reinforced silicon carbide ceramic matrix composite (SiCf/SiC composite) is characterized by a high strength-to-density ratio, high hardness, and high temperature resistance. However, due to the brittleness of the matrix material and the anisotropy of the reinforcing phase, it is a huge challenge for machining of the material. The milling method has advantages of a high material removal rate and applicability to complex surface geometry. However, no published literature on milling of SiCf/SiC composite has been found up to now. In this paper, high-speed milling of SiCf/SiC composites was carried out under dry conditions and cryogenic cooling using liquid nitrogen, respectively. Polycrystalline diamond (PCD) and chemical vapor deposition (CVD) diamond cutting tools were used for the milling work. The cutting performance of the two kinds of tools in high-speed milling of SiCf/SiC composites was studied. Tool failure modes and mechanisms were analyzed. The effects of the cooling approach on tool wear and machined surface quality were also investigated. The experimental results showed that under identical cutting parameters and cooling approaches, the PCD tool yielded better cutting performance in terms of a longer tool life and better surface quality than that of the CVD diamond tool. In dry machining, the failure modes of the CVD diamond tool were a large area of spalling on the rake face, edge chipping and severe tool nose fracture, whereas for the PCD tool, only a small area of spalling around the tool nose took place. Compared to the dry machining, the wear magnitudes of both PCD and CVD diamond tools were decreased in cryogenic machining. Additionally, the surface quality also showed significant improvements. This study indicates that the PCD tool is highly suitable for machining of SiCf/SiC composite, and that the cryogenic method can improve machining efficiency and surface quality.

Analysis of cutting responses of Sialon ceramic tools in high-speed milling of FGH96 superalloys

Powder metallurgy superalloy FGH96 is being extensively used to fabricate the hot section of the aeronautic and astronautic turbine engines owing to its superior mechanical properties maintained at high-temperature environments. However, machining such a difficult-to-cut material entails high cutting forces, excessive cutting temperatures and serious tool wear. Although Sialon ceramic tools have been successfully employed in the turning and milling processes for the Inconel 718, their application for the machining of powder metallurgy superalloys is very limited. In the current work, a series of high-speed milling trials were conducted to examine the influences of the milling parameters on the cutting response and tool wear mechanisms during the milling of FGH96 with Sialon ceramic mills under dry conditions. The milling forces and machining temperatures were studied with respect to the used process parameters. The quality of cut surfaces and wear signatures of ceramic tools were also discussed. Results indicate that the resultant cutting forces only decrease until the cutting speed exceeds 315 m/min. Furthermore, the Sialon tools seem more suitable for the rough machining of FGH96 considering the surface finish and large residual tensile stress existing on the milled surface. Finally, the adhesion wear is the primary wear mode occurring at the flank surface, while the edge chipping and flaking dominate the failure of the tool rake surface.

New observations on wear characteristics of solid Al2O3/Si3N4 ceramic tool in high speed milling of additive manufactured Ti6Al4V

Additive Manufacturing (AM) technologies applied to the titanium alloys have attracted attention from industries in recent years. Despite one of the main goals of AM is the reduction of manufacturing steps, semi-finish/finish machining operations are still required so as to obtain the desired geometrical tolerance and surface features. In this study, the solid end mill was manufactured by Al2O3/Si3N4 (Sialon) ceramic materials and employed in high-speed slot milling of Ti6Al4V alloy fabricated by the Direct Metal Laser Sintering (DMLS) AM technology to study the tool wear characteristics during processing. The Raman spectroscopic method was employed to characterize the molecular structures of Sialon ceramics for the manufacturing of the cutting tool. The morphologies and elemental maps of wear region of the ceramic tool were examined by scanning electron microscope and energy dispersive spectroscopy techniques. The results show that the adhesion wear and diffusion wear are the dominant wear mechanisms, and the chemical stability of Al2O3/Si3N4 (Sialon) ceramics fabricated as the solid ceramic tool to the attack of the atoms from additive manufactured Ti6Al4V is relatively weak under the atmosphere. The difference of thermal expansion coefficients of diffusion layer and tool substrate accelerates the initiation and propagation of thermal cracks formed on the diffusion interface. Moreover, fracturing and crater-like groves near the tool edge were finally formed due to the removal of adhered workpiece material.

Cutting Performance Evaluation of the Coated Tools in High-Speed Milling of AISI 4340 Steel.

The cutting performance of cutting tools in high-speed machining (HSM) is an important factor restricting the machined surface integrity of the workpiece. The HSM of AISI 4340 is carried out by using coated tools with TiN/TiCN/TiAlN multi-coating, TiAlN + TiN coating, TiCN + NbC coating, and AlTiN coating, respectively. The cutting performance evaluation of the coated tools is revealed by the chip morphology, cutting force, cutting temperature, and tool wear. The results show that the serration and shear slip of the chips become more clear with the cutting speed. The lower cutting force and cutting temperature are achieved by the TiN/TiCN/TiAlN multi-coated tool. The flank wear was the dominant wear form in the milling process of AISI 4340. The dominant wear mechanisms of the coated tools include the crater wear, coating chipping, adhesion, abrasion, and diffusion. In general, a TiN/TiCN/TiAlN multi-coated tool is the most suitable tool for high-speed milling of AISI 4340, due to the lower cutting force, the lower cutting temperature, and the high resistance of the element diffusion.

Cutting performances of MCD, SMCD, NCD and MCD/NCD coated tools in high-speed milling of hot bending graphite molds

Abstract The machining accuracy and service life of high-speed milling tools have a great influence on the surface roughness and dimensional precision of hot bending graphite molds used in the manufacture of 3D curved glass such as protective screens and rear covers of 3C electronic products. The microcrystalline diamond (MCD), submicrocrystalline diamond (SMCD), nanocrystalline diamond (NCD) and micro/nano-crystalline composite diamond (MCD/NCD) coatings were deposited on commercial corner radius end milling tools by using a hot filament chemical vapor deposition (HFCVD) equipment. The morphologies, phase structures and adhesive strength of various types of diamond coatings were systematically tested by Field emission scanning electron microscopy (FESEM), Raman spectroscopy and Rockwell indentation tests respectively. Besides, the tribological performances of various diamond coatings were assessed by the ball-on-disk rotational friction tester. Composite MCD/NCD coating exhibits good friction properties, superior wear resistance and satisfactory material removal rate during the process of sliding against graphite. Further high-speed milling experiments of graphite using bare WC-Co, MCD, SMCD, NCD and MCD/NCD coated milling tools were carried out to characterize their corresponding cutting performances and wear mechanism. Tool wear progressions of different kinds of milling tools with the cutting length were obtained. Moreover, tool wear morphologies were acquired by FESEM and machined surface roughness of graphite were measured by 3D surface profile meter. Results indicate that MCD/NCD coated milling tool exhibits excellent cutting performances compared to the other milling tools due to the comprehensive properties of better surface smoothness and higher adhesive strength with WC-Co substrates. What’s more, the machining dimensional accuracy and machined surface roughness during high-speed milling of hot bending graphite molds using MCD/NCD coated milling tool could meet the strict requirements of 3C electronic products even without the need or with less need for subsequent lapping and polishing.

Wear Mechanism of Cemented Carbide Tool in High Speed Milling of Stainless Steel

Adhesion of cutting tool and chip often occurs when machining stainless steels with cemented carbide tools. Wear mechanism of cemented carbide tool in high speed milling of stainless steel 0Cr13Ni4Mo was studied in this work. Machining tests on high speed milling of 0Cr13Ni4Mo with a cemented carbide tool are conducted. The cutting force and cutting temperature are measured. The wear pattern is recorded and analyzed by high-speed camera, scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). It is found that adhesive wear was the dominant wear pattern causing tool failure. The process and microcosmic mechanism of the tool’s adhesive wear are analyzed and discussed based on the experimental results. It is shown that adhesive wear of the tool occurs due to the wear of coating, the affinity of elements Fe and Co, and the grinding of workpiece materials to the tool material. The process of adhesive wear includes both microcosmic elements diffusion and macroscopic cyclic process of adhesion, tearing and fracture.

Tool determination and geometry parameter optimization of carbide tool in high-speed milling of third-generation γ-TiAl alloy

Gamma titanium aluminide alloys (γ-TiAl) are widely recognized as potential replacement for nickel-based superalloys in aerospace. However, along with brittleness at room temperature, poor surface quality and sever tool wear undermine their machinability, so that γ-TiAl alloy is considered as a typical intractable material. Tool selection and geometry optimization are encouraging strategies to improve the machinability of this kind of material. In this work, the cutting performance of six carbide grade tools is compared. And the cutting force, surface roughness and tool wear are selected as the evaluation criterion for the tool material determination. Then, the effects of tool geometry parameters including rake angle, primary relief angle and helix angle on surface roughness and tool wear are further studied. The sample dataset is utilized to formulate the first-order model with interaction. The predicted results of these models accorded well with the measured results. Due to the multi-performance characteristics, grey relational analysis method is introduced into the optimization of tool geometry parameters. The analysis of variance is employed to identify the most significant factor. And then, the confirmation test showed the improvement of the multi-performance characteristics.

Performance optimization for cemented carbide tool in high-speed milling of hardened steel with initial microstructure considered

Investigation on cutting parameter optimization was performed to enhance the cemented carbide tool life in high-speed milling of hardened steel. Image analysis of the tool material microstructure was conducted to determine the average grain diameter and the size of the representative element. The initial state of the tool material microstructure was evaluated based on micromechanics and damage mechanics. Finite element simulation of the milling process was performed to acquire the tool stress. The original damage of the tool and simulated tool stress were integrated based on the concept of damage equivalent stress. Distribution and evolution of the damage equivalent stress on the tool body was analyzed and a new indicator for cutting parameter optimization was brought forward. A cutting parameter optimization method was proposed on the basis of the new indicator. Experimental tests showed that the proposed optimization method can be used to identify the optimum cutting parameter combination and prolong the cemented carbide tool life in high-speed milling process.

Kinematical Smoothing of Rotary Axis near Singularity Point

This paper deals with singular configurations of a 5-axis machine tool in high speed milling which may lead to the appearance of large incoherent movements of rotary axes near singularity points. These movements generate slowdowns of the actual feedrate during the execution of the tool path, which affect quality and productivity. Thus, this paper proposes a method to detect these behaviors during machining simulation and correct the tool path. Unlike the literature methods, this correction consists in modifying the tool axis orientation by going through the singularity point while respecting maximum velocity, acceleration and jerk of the rotary axis. For that purpose, the initial articular positions of the rotary axis near the singularity point are fitted with B-spline curves, modified and finally discretized for linear interpolation. Experimental investigations on a test part are carried out to show the efficiency of the method.

Investigation of wear and tool life of coated carbide and cubic boron nitride cutting tools in high speed milling

The objective of the investigation was analysis of the wear of milling cutters made of sintered carbide and of boron nitride. The article presents the life period of the cutting edges and describes industrial conditions of the applicability of tools made of the materials under investigation. Tests have been performed on modern toroidal and ball-end mill cutters. The study has been performed within a production facility in the technology of high speed machining of 55NiCrMoV6 and X153CrMoV12 hardened steel. The analysed cutting speed is a parameter which significantly influences the intensity of heat generated in the cutting zone. Due to the wear characteristics, two areas of applicability of the analysed tools have been distinguished. For vc ≤ 300 m/min, sintered carbide edges are recommended; for vc > 500 m/min, boron nitride edges. For 300 ≤ vc ≤ 500 m/min, a transition area has been observed. It has been proved that the application of sintered carbide edges is not economically justified above certain cutting speed.

Robust Design of Using MWCNTs in Minimum Quantity Lubrication

This objective of this article is to present a new technique of nanofluids/MQL in high speed milling by using MWCNTs. In the past, studies have shown the MQL process can improve tool life and surface accuracy in high speed cutting. The purpose of using carbon nanotubes is to increase the thermal conductivity of cutting fluid and to reduce the temperature during the cutting and decrease the thermal wear of tool. The proposed study is to investigate the characterization of the MWCNTs/ nanofluids combined with MQL during the high speed milling of AISI 1050 and AISI P21 experimentally. The Taguchi robust design was also used to optimize the parameters of nozzle with respect to tool feed direction, such as spraying distance, angle of ejection, and relative locations for improving the MWCNTs/MQL cutting effect. Experimental results showed the MWCNTs/ nanofluid had the benefits of improving surface roughness and reducing wear of tool in high speed milling. The results were compared to dry cutting, and wet cutting in detail.

Effect of Cutting Speed on Wear Property of TiAlN PVD Coated Tools in High-Speed Milling of AISI P20 Mold Steel

High speed cutting is an important means to improve the efficiency and the quality of machining mold steel, but the tool wear is one of the key factors restricting the increase of the cutting speed, leading to higher requirements for cutting tool materials. At present the researches of high-speed cutting of mold steel are mainly on the hardness mold steel, but less on P20 mold steel which hardness is 30-42HRC. This paper mainly studies the effect of cutting speed on wear property of TiAlN PVD coated tools when high-speed milling of P20 mold steels. The experiment was conducted using two different high cutting speeds under dry condition, 320m/min and 500m/min. Wear characterization of the rake and the flank surfaces as well as the collected chips were performed using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). It was found that at high speeds, the dominant wear mechanisms were oxidation wear and diffusion wear, followed by adhesive wear and melt wear; as the cutting speed increased, the wear surface area of rake face will be closer to the main cutting edge.

Study on the Tool Wear of Coated Carbide Tool in High Speed Milling Titanium Alloy

The milling experiments were carried out using TiAlN and PCD coated carbide tools in high speed milling Ti6Al4V to compare and analyze tool wear and tool life of the two kinds of coating carbide tools. In addition, the effect of cooling and lubricating on tool wear is also studied. The results showed that fluid environment is not suitable for milling Ti6Al4V. PCD coating carbide tool can effectively increase the life of tool in high speed milling of Ti6Al4V.

Investigation of Cutting Force and Tool Wear in High Speed Milling of GH4169 Using Ceramic Tools

Experiments were carried out to investigate the cutting force and tool wear behavior of Sialon ceramic tools in high speed milling of GH4169 under different cutting parameters. The cutting speed exhibited the most significant influence on the cutting force. The cutting force decreased firstly then increased with the increasing of cutting speed. And the effect of feed speed and cutting depth on cutting force were also discussed. The worn surfaces of tool were examined and the elements on the tool surfaces were analyzed by employing scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), respectively. The analysis results of the SEM and EDS showed that the dominant wear pattern were rake face flaking and notching at the low cutting speed while flank wear was the main wear type at the high cutting speed of 1037m/min.

Wear mechanism and life prediction of TiN coated tool in high speed milling of ceramic–PTFE composite

With TiN coated solid carbide, a series of machining experiments were performed to define wear blunt criterion, and the recommended wear blunt criterion is 40 μm. Using orthogonal experiment method, multifactor and multilevel cutting experiments were designed. Based on the measuring results, forms of tool wear are discussed according to grain abrasion, diffusion abrasion, bonding abrasion, and crack and breakage. Tool wear mechanism was analysed in detail by micropattern scan and chemical element analysis. For dependent variable wear extent (VB), regression analysis was performed with independent variables such as cutting speed v, feed rate f, axial depth of cut ap, radial depth of cut ae and cutting length L. Based on the calculated result of VB, a method was proposed to predict tool life. Research results will provide a useful way of processing optimisation and quality improvement for high speed machining of ceramic–polytetrafluoroethylene composites.

PERFORMANCE OF A COATED CEMENTED CARBIDE TOOL IN HIGH SPEED MILLING OF TI-6AL-4V ALLOY

A series of experiments were conducted to study the performance of a coated cemented carbide tool in high speed milling of Ti -6 Al -4 V alloy. Experimental measurements of three components of the cutting forces were performed by using a three-component dynamometer. The cutting temperature was measured by using an infrared thermal imager. The variation of cutting forces and cutting temperature with the cutting parameters are investigated. The influence of cutting speed, axial depth of cut, and feed rate on the cutting forces and cutting temperature are analyzed and discussed. The wear patterns of the tool were investigated using scanning electron microscope (SEM) and analysis of energy spectrum, and the wear mechanism is discussed. It is found that abrasive wear and adhesive wear are the dominant wear mechanism of the tool.

Performance of Cutting Tools in High Speed Milling of SiCp/Al Composites

This paper presents an experimental study in milling of SiCp/Al composites on a high precision machine by using chemical vapor deposition(CVD) diamond coated tools and polycrystalline diamond (PCD) tools. The tool wear was observed and measured by an optical microscope and a scanning electron microscope (SEM). The results show that the coating rupture causes the failure of the CVD diamond coated tools. The PCD tools’ wear is less. At the relatively low cutting speed, the wear pattern of PCD tools is the flank wear which caused by the abrasion of SiC particles. Due to the low cutting temperature, the graphitization of PCD tools does not happen. The wear mechanism of PCD tools will be the abrasive and adhesive wear.

Tool Life and Surface Integrity in High-speed Milling of Titanium Alloy TA15 with PCD/PCBN Tools

Titanium alloys are widely used in aeronautics that demand a good combination of high strength, good corrosion resistance and low mass. The mechanical properties lead to challenges in machining operations such as high process temperature as well as rapidly increasing tool wear. The conventional tool materials are not able to maintain their hardness and other mechanical properties at higher cutting temperatures encountered in high speed machining. In this work, the new material tools, which are polycrystalline diamond (PCD) and polycrystalline cubic boron nitride (PCBN) tools, are used in high-speed milling of Ti-6.5Al-2Zr-1Mo-1V (TA15) alloy. The performance and wear mechanism of the tools are investigated. Compared to PCBN tool, PCD tool has a much longer tool life, especially at higher cutting speeds. Analyses based on the SEM and EDX suggest that attrition, adhesion and diffusion are the main wear mechanisms of PCD and PCBN tools in high-speed milling of TA15. Oxidation wear is also observed at PCBN tool/workpiece interface. Roughness, defects, micro-hardness and microstructure of the machined surface are investigated. The recorded surface roughness values with PCD/PCBN tools are bellow 0.3 μm at initial and steady cutting stage. Micro-hardness analysis shows that the machined surface hardening depth with PCD and PCBN tools is small. There is no evidence of sub-surface defects with PCD and PCBN tools. It is concluded that for TA15 alloy, high-speed milling can be carried out with PCD/PCBN tools.

Study on the Wear Mechanism of PCD Tools in High-Speed Milling of Al-Si Alloy

Polycrystalline diamond (PCD) tools have been obtained increasing application in aluminum alloy processing industry due to the excellent surface finish and tool life comparing with other traditional tools. Investigation of the wear mechanism of PCD milling tool for machining Al-Si alloy at cutting speed of 5000m/min (n=12732r/min) has been performed. The wear morphology of tool has been studied by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). Results show that PCD milling tool suffers from abrasive wear and diffusion wear on the flank face and adhesive wear on the rake face in the machining process.