Higher Tool Life Research Articles

Analyzing the Effectiveness of Microlubrication Using a Vegetable Oil-Based Metal Working Fluid during End Milling AISI 1018 Steel

Microlubrication minimizes the exposure of metal working fluids to the machining operators leading to an economical, safer, and healthier workplace environment. In this study, a vegetable oil-based lubricant was used to conduct wear analysis and to analyze the effectiveness of microlubrication during end milling AISI 1018 steel. A solid carbide cutting tool with bright oxide finish was used with varying cutting speed and feed rate having a constant depth of cut. Abrasion was the dominant wear mechanism for all the cutting tools under consideration. Other than abrasion, sliding adhesive wear of the workpiece materials was also observed. The scanning electron microscope investigation of the used cutting tools revealed microfatigue cracks, welded microchips, and unusual built-up edges on the cutting tools flank and rake side. A full factorial experiment was conducted and regression models were generated for both the sides of tool flank wear. The study shows that with a proper selection of the cutting parameters it is possible to obtain higher tool life.

Surface roughness model in turning hardened hot work steel using mixed ceramic tool

This experimental study is conducted to determinestatistical models of surface roughness criteria inhard turning of high alloyed steel X38CrMoV5-1. Thissteel is hardened to 50 HRC, machined by a mixed ceramictool (insert CC650 of chemical composition70%Al2O3+30%TiC), free from tungsten on Cr-Mo-V basis,insensitive to temperature changes and having a highwear resistance. It is employed for the manufacture ofhighly stressed diecasting moulds and inserts with hightool life expectancy, plastic moulds subject to high stressand forging dies.Based on 33 full factorial design, a total of 27 testsare carried out. The range of each parameter is set at threedifferent levels, namely low, medium and high. Mathematicalmodels were deduced by the software Minitab(multiple regression method) in order to express the influencedegree of each cutting regime element on surfaceroughness. These models would be helpful in selectingcutting variables for the required surface roughness criteria.They can also be used for the optimization of hard cuttingprocess.The results indicate that feed rate is the dominantfactor affecting surface roughness, followed by cuttingspeed. As for the depth of cut, its effect is not very important.

CFRPの高能率トリミングを実現する2分割傾斜エンドミル加工法

This paper presents a simple machining method for trimming of CFRP (Carbon Fiber Reinforced Plastic) with an end mill, which can realize significantly high machining efficiency and long tool life with good surface finish. It seems that the conventional problems in the trimming process, such as delamination of trimmed edges, machining efficiency and tool wear, are caused by applying conventional milling conditions for metals without considering strong anisotropic material property of CFRP. In the proposed method, lead and helix angles of the end mill are selected appropriately so that the milling force suppresses the delamination. In order to finish the upper and lower edges on this concept, the upper and lower surfaces are machined separately at different lead angles. It is confirmed experimentally that the delamination is suppressed and tool life is extended at appropriate lead/helix angles, even when the feed rate (machining efficiency) becomes more than ten times higher than the conventional rate.

Investigation of Tool Wear, Tool Life and Surface Roughness when Machining AISI D2 Hardened Steel Using PVD TiAlN Coated Carbide Tools

This paper discussed the behavior of cutting tool in terms of tool wear, tool life and surface roughness when machining an AISI D2 hardened steel. An experimental test was conducted at different cutting speeds (Vc) and radial depth of cut (ae) using PVD TiAlN coated carbide tool under dry condition. Tool failure modes and tool wear mechanism for all cutting tools were examined at various cutting parameters. Flank wear was found to be the predominant tool failure for cutting tools. The highest volume material removal (VMR) attained was 3750 mm3 meanwhile the highest tool life (TL) was 9.69 min. The surface roughness (Ra) values from 0.09 to 0.24 μm can be attained in the workpiece with a high material removal. The relationship of tool wear performance and surface integrity was established to lead an optimum parameter in order to have high material removal, maximum tool life as well as acceptable surface finish.

An Experimental Study on the Cutting Tool Performance during Milling of Carbon Fiber Reinforced Polymer

Carbon Fiber Reinforced Plastic (CFRP) is widely used in aerospace field as an advanced composite material. Recently, more and more studies are focused on milling of CFRP with its increasing applications. In this paper, three different milling tools were chosen, and a systematic analysis on cutting force, surface quality and tool wear has been carried out to evaluate the tools. Experimental results indicate that the multi-flute tool with diamond coating has a better performance than the double spiral compression tool and the multi-tooth tool with AlTiN coating, with a lower cutting force, a better surface quality and a higher tool life than others, which would be a better tool for cutting of CFRP.

Surface Layer States of Worn Uncoated and TiN-Coated WC/Co-Cemented Carbide Cutting Tools after Dry Plain Turning of Carbon Steel

Analyzing wear mechanisms and developments of surface layers in WC/Co-cemented carbide cutting inserts is of great importance for metal-cutting manufacturing. By knowing relevant processes within the surface layers of cutting tools during machining the choice of machining parameters can be influenced to get less wear and high tool life of the cutting tool. Tool wear obviously influences tool life and surface integrity of the workpiece (residual stresses, surface quality, work hardening, etc.), so the choice of optimised process parameters is of great relevance. Vapour-deposited coatings on WC/Co-cemented carbide cutting inserts are known to improve machining performance and tool life, but the mechanisms behind these improvements are not fully understood. The interaction between commercial TiN-coated and uncoated WC/Co-cemented carbide cutting inserts and a normalised SAE 1045 steel workpiece was investigated during a dry plain turning operation with constant material removal under varied machining parameters. Tool wear was assessed by light-optical microscopy, scanning electron microscopy (SEM), and EDX analysis. The state of surface layer was investigated by metallographic sectioning. Microstructural changes and material transfer due to tribological processes in the cutting zone were examined by SEM and EDX analyses.

Study on Extending Tool Life of Micro WC Drills by Various Protective Coatings

As the trend of electronic industry is fast moving towards miniaturization, diversity, high efficiency and high throughput, the devices to be mounted onto a PCB are increasingly densely packed so are the holes needed to keep all elements in place. To effectively and economically generate so many holes of small diameter and high aspect ratio, the drilling process has to be done in a high speed manner and tool life has to be kept as long as possible. This study aimed to improve the tool life and the quality of the obtained holes by applying various hard coatings on the drills. The results showed that tool life could be effectively improved from 2500 hits to around 11000 hits at 155Krpm and 3.5m/min when proper hard coating was applied. It was found that wear of drill was resulted mainly from abrasive wear and adhesion wear. It was also showed in the research that while non-coated drills suffered serious deformation after 500 hits those coated with Al2O3 could finish 11000 hits with very limited wear land on the drills.

Micro Hole Elliptical Supersonic Boring Quality Research

In this paper a method of ultrasonic elliptical vibration cutting has been applied to precision boring of micro hole due to its superior performances such as low cutting force, high quality surface finish and long tool life. A transducer with the longitudinal excitation is carried out to machining(boring) micro hole of 1Cr18Ni9Ti workpiece. The cutting force and surface quality are studied in detail.The workpiece with surface roughness of Rz 0.4μm is achieved.The results showed that the ultrasonic elliptical vibration transducer can be applied rationally in micro hole precision boring.

The effects of cutting parameters on tool life and wear mechanisms of CBN tool in high-speed face milling of hardened steel

High-speed face milling of AISI H13 hardened steel is conducted in order to investigate the effects of cutting parameters on tool life and wear mechanisms of the cubic boron nitride (CBN) tools. Cutting speeds ranging from 400 to 1,600 m/min are selected. For each cutting speed, the metal removal rate and axial depth of cut are fixed, and different combinations of radial depth of cut and feed per tooth are adopted. The tool life, tool wear progression, and tool wear mechanisms are analyzed for different combinations of cutting parameters. It is found that for most of the selected cutting speeds, the tool life increases with radial depth cut and then decreases. For each cutting speed, the CBN tool life can be enhanced by means of adopting suitable combination of cutting parameters. When the cutting speed increases, the normal wear stage becomes shorter and the tool wear rate grows larger. Because of the variations of cutting force and tool temperature, the tool wear mechanisms change with different combinations of cutting parameters even at the same cutting speed. At relatively low cutting speed, in order to acquire high tool life of the CBN tool, the tool material should possess sufficient capability of resisting adhesion from the workpiece. When relatively high cutting speed is adopted, retention of mechanical properties to high cutting temperature and resistance to mechanical impact are crucial for the enhancement of the CBN tool life.

Tool Wear Performance of TiAlN/AlCrN Multilayer Coated Carbide Tool in Machining of AISI D2 Hardened Steel

This paper presents the results of experimental investigation conducted on a vertical machining centre (VMC) to ascertain the effectiveness of TiAlN/AlCrN multilayer coated carbide inserts in end milling of AISI D2 hardened steel (58-62 HRC) In high-speed dry hard milling, different cutting speed (v) and radial depth of cut (dr) were applied. Tool failure modes and wear mechanisms were examined at various cutting parameters. Flank wear, chipping and breakage at cutting edge were found to be the predominant tool failure for the cutting tools. Built-up edge, adhesion and abrasive are the wear mechanisms observed on the cutting tools. The highest volume of material removed, VMR attained was 1500 mm3, meanwhile the highest tool life (T) was 4.97 min. The surface roughness, Ra values from 0.20 to 0.45 μm can be attained in the workpiece with a high volume material removed. The relationship of tool wear performance and surface integrity was established to lead an optimum parameter in order to have high volume material removed, maximum tool life as well as acceptable surface finish.

On the honed cutting edge and its side effects during orthogonal turning operations of AISI1045 with coated WC-Co inserts

The design of the cutting tool microgeometry influences the thermo-mechanical load profile on the wedge. Applying the appropriate hone design stabilizes the cutting edge, leads to improved wear behavior and higher tool life. Higher process forces and temperature, induced by larger hone, can be described as a side effect of cutting edge preparation, which should also be observed. This paper presents the quality oriented cutting edge preparation via abrasive brushing. The influence of the hone design on process forces, wear behavior and tool life of coated inserts will be analyzed within a wide range of cutting edge microgeometries and process parameters.

Polycrystalline Cubic Boron Nitride (PCBN) Tool Life and Wear in Turning of Amorphous-Crystalline Iron-Based Coatings

The paper presents PCBN-Ciborit cutting tools life and wear test results. The effects of the machining regime when turning amorphous-crystalline Fe80B20 and Fe79Cr16B5 coating systems applied to conventional workpiece materials were assessed. It has been shown that the observed tool wear mechanisms are complex in their character and are dominated by abrasive-mechanical, adhesive and chemical effects in the cutting zone. Under changing turning conditions tool life is affected by the structural-phase composition and by the non-homogeneous structure of the coating. Specifically, when turning gas-flame coatings deposited with a Fe80B20 electrode and electro-arc coatings with a Fe79Cr16B5 electrode the lowest wear and the highest tool life was achieved at cutting speeds of v = 1.1 to 1.2 m/s and a back rake angle of γ = –10o. It has been demonstrated that a change of the back rake angle from γ = 0 to –10o does not have a great effect on tool life contrary to the case with γ = -20o.

Application of response surface methodology for determining cutting force model in turning hardened AISI H11 hot work tool steel

This experimental study is conducted to determine statistical models of cutting forces in hard turning of AISI H11 hot work tool steel (∼ 50 HRC). This steel is free from tungsten on Cr–Mo–V basis, insensitive to temperature changes and having a high wear resistance. It is employed for the manufacture of highly stressed diecasting moulds and inserts with high tool life expectancy, plastic moulds subject to high stress, helicopter rotor blades and forging dies.

A study on the influence of bond material on honing engine cylinder bores with coated diamond stones

A consistent increase in demand for special tools designed to enhance an efficient honing of engine cylinder bores is observed. Metallic Bonded Diamond Stones (Dia-M) are more and more used for their wear resistance and their high tool life. However, the hardness of this Metallic Bond leads to the degradation of the honed surface aspect by the formation of smudgy grooves edges (blechmantel). This torn and folded metal affects the required functional performances of the cylinder bore. In this study, two new diamond coated abrasive stones with Vitrified and Resinoid Bonds (respectively Dia-V and Dia-R) are tested and compared to the Dia-M sticks. The influences of bond material on the honing reliability are studied in terms of honed surface aspect, material removal rate and wear properties. Results reveal that the stiffness and the openness structure of the Resinoid Bond leads to a better trade off between surface aspect and tool life.

Evaluation of critical parameters in micro machining of hardened tool steel

Micro mechanical milling plays a significant role in fabrication of miniature features in a variety of materials with capability for producing three dimensional (3D) freeform surfaces. A major challenge for micro machining of hardened material is a high tool wear rate and unpredictable tool life. In addition, surface roughness and burr formation are factors to be closely controlled. In this paper, the statistical analysis of critical parameters for micro milling of hardened tool steel is presented. The parameters included spindle speed, depth of cut, ratio of undeformed chip thickness to cutting edge radius and lubrication/environment conditions. The significance of these parameters on surface finish, burr formation and tool wear are reported. The study shows that machining environment is the most significant factor in controlling surface finish and tool wear. While, selection of appropriate spindle speed and the ratio of undeformed chip thickness to cutting edge radius is more critical in limiting burr size. The work reported in this paper is important, because industry needs to know key process variables (KPVs) that are critical in the control of micro machining performance. Additionally, the methodology enabled identification of optimum cutting values for these cutting parameters within the identified process window.

Prediction of drill-bit breakage from degradation signals using Mahalanobis-Taguchi system analysis

Drilling is a widely used machining process. As the hole drilling operation progresses, a drill-bit gradually degrades until it breaks at the end of its life. Replacing a drill-bit after it is breakage can be costly in certain special applications. At the same time an early tool replacement decision may lead to lower tool life utilisation. This calls for methods that enable accurate prediction of tool failures. In such situations degradation signals using appropriate features are utilised to arrive at the tool replacement decision. In this paper we study two such degradation signals viz., thrust force and torque using 20 derived features (10 features per degradation signal). The methodology used involves a successful application of Mahalanobis-Taguchi System (MTS) analysis that enables an accurate prediction of drill-bit breakage ensuring high tool life utilisation.

High cycle fatigue life prediction of cold forging tools based on workpiece material property

Abstract The present investigation is focused on high cycle fatigue life prediction based on material property of the workpiece. A new approach based on industrial tool life data was introduced for estimation of fatigue properties of the tool material. The effect of the strength coefficient K and strain hardening exponent n of four different workpiece materials was included in the local stress and strain approach to derive a simple relationship between the high cycle fatigue life and material property of the workpiece. According to this relationship, a reasonably reliable high cycle fatigue tool life can be estimated.

Ultrasonic elliptical vibration transducer driven by single actuator and its application in precision cutting

The ultrasonic elliptical vibration cutting has been successfully applied to precision cutting due to its superior performances, such as low cutting force, high quality surface finish and long tool life. This paper presented an asymmetrical structural model of the ultrasonic elliptical vibration transducer with only the longitudinal excitation. Based on the modal and static analysis with finite element method, various parameters of the model were modified to meet the needs of the vibration modality and the inherent frequency. A cutting system of the ultrasonic elliptical vibration driven by single longitudinal actuator was developed and the effect of the transducer amplitude and cutting depth on the cutting force was studied in detail. A part with surface roughness of R a 0.08 μm was achieved. The results showed that the ultrasonic elliptical vibration transducer can be designed rationally with finite element method and single driven ultrasonic elliptical vibration machining can be used in precision cutting.

Influence of preheating on performance of circular carbide inserts in end milling of carbon steel

Circular inserts have much higher tool life as compared to conventional rectangular inserts because of their capability to be indexed through small angles for repeated use. Their only limitation is high chattering tendencies due to high contact length in conjunction with small uncut chip thickness. Experimental investigations were conducted to investigate the influence of preheating on performance of circular cemented carbides inserts in end milling operation of mild steel performed on vertical machining center (VMC) with rigid structure. Three TiN-coated circular cemented carbide inserts fitted on a 32 mm diameter tool were used in the experiments. Variable cutting parameters were cutting speed and feed. Depth of cut was kept constant at 1 mm. Performance of the inserts under room temperature and preheated machining was compared in terms of vibration stability, surface roughness, tool life and chip integrity. Vibration signals were recorded using an accelerometer type transducer and a Dual Channel Portable Signal Analyzer. The recorded signals were analyzed using the PULSE Labshop software. Surface roughness values were measured using a surface roughness measuring instrument—Mitutoyo Surfacetest model SJ-400. Worn tools and pitches of serrated chip teeth were studied under a scanning electron microscope (SEM). It was observed that during machining with and without preheating the main chatter frequencies remained practically constant and close to the natural frequencies of the system components while the amplitudes varied with cutting conditions. The amplitudes of chatter during preheating were found to be much lower than those during room temperature machining, as a result of which the surface roughness and tool wear were found to be much lower during preheated machining. The effect of chatter was also reflected on chip serration and segmentation. It was also observed that feed rate and cutting speed have considerable effect on surface roughness and tool wear in the cases of both hot and room temperature machining.

Tribological properties and dry machining characteristics of PVD-coated carbide inserts

Tools for cutting operation are subject to very high abrasive, adhesive, and thermal loads. Process security and preparation quality as well as a sufficiently high tool life demand for the development of hard coatings with reduced seizure tendency, high hot hardness, and increased wear resistance especially under dry machining conditions. TiAlN coatings are the state-of-the-art coatings for machining operations. Hard materials on chromium basis like CrN or CrAlN are preferably used for bending and stamping tools. Thus, these coatings could have a high potential in machining operations. The aim of using chromium-based coatings is to redirect the heat from the workpiece and tool into the chip, thus acting as a thermal barrier. Due to their high oxidation resistance, CrN and Cr x Al y N coatings were deposited on WC/Co inserts. In order to find improved coatings for dry machining operations, mechanical characterizations and turning tests were performed. The characterization of the coatings includes fundamental properties such as thickness, hardness, and critical load. With Glow Discharge Optical Emission Spectroscopy (GDOES), depth profile analyses were executed. SEM analyses supplemented the picture of the scratch tests. Turning operations were performed in model tests to characterize the dry machining characteristics. The wear properties of CrN and Cr x Al y N coatings were compared with industrially coated (Ti,Al)N carbide inserts. Calculations of the friction coefficient supplemented the tests.