Tool Life Research Articles

Five-Axis Finish Milling Machining for an Inconel 718 Alloy Monolithic Blisk

Blisks subjected to rough machining for channel creation must undergo finishing processes, and such processes must achieve the required tolerance limits. A high-quality surface finish and predictable long tool life are critical for the finish milling of blisks. Accordingly, the aim of this study was to optimize parameters for the finish machining of an Inconel 718 alloy monolithic blisk. Ball-cone mills were used to machine the blade surface at a constant depth. A sensory tool holder was used to collect cutting force signals during machining, and a digital microscope was used to examine tool wear. The surface texture measuring instrument was used to measure blisk blade surface roughness to evaluate processing quality. This study manipulated two cutting parameters, namely cutting speed and feed per tooth, and investigated their effects. The relationship between cutting conditions and machining efficiency was analyzed. According to the experimental results, we identified a set of optimal parameters at effective cutting speeds of 46.53 m/min, feed per tooth of 0.1 mm/tooth, and depth of cut of 0.05 mm for marginal tool wear and fast cutting speeds. Then the corresponding tool life was estimated by using the derived parameters.

Optimizing tool life in SiCp/Al composites milling with acoustic emission analysis: A comprehensive monitoring and implementation strategy

The machining of SiCp/Al composites is hampered by tool wear monitoring challenges. SiCp/Al composites are used in industries like aerospace where tool wear can lead to workpiece loss, necessitating real-time monitoring. Acoustic emission (AE) sources during machining are complex due to SiC particles. This paper attempts to isolate AE frequencies for plastic deformation and silicon carbide particle behavior through scratch experiments at different depths. The relationship between signal energy distribution and tool wear during milling is analyzed using the wavelet packet method. The frequency band correlating best to tool wear is identified outside the scratch experiment's frequency range. A monitoring strategy is proposed based on this, and the effect of machining parameters on AE monitoring is analyzed, with refinements to the monitoring model. The proposed strategy's effectiveness has been validated through experimental trials, resulting in an average tool utilization rate of 85 % during milling.

Effect of metallic substrate and rubber elastic materials over passive constrained layer damping on tool vibration during boring process

Tool vibration is a key factor that affects surface finish, generates noise, and reduces the tool life during conventional boring because of the excessive overhanging length of the tool holder. The interaction between the dynamics of the machine tool and the boring process led to progressive vibration. The creation of appropriate mechanisms in reducing tool vibration will help manufacturing industries to become more productive. In this research, in order to control vibration in the overhanging boring bar, a passive vibration control method was employed. Constrained layer dampers consist of boring bar, substrate, and elastic materials and it is used to minimize tool vibration produced during boring operation. The investigation utilized computational analysis through the ANSYS Workbench platform, employing key parameters such as the overhanging length of the tool holder (100, 150, and 200 mm), substrate material (aluminum, brass, and copper), and elastic material (Nitrile rubber, Natural rubber, and polyurethane). A comprehensive series of 27-run boring experiments were conducted to assess the impact of the constrained layer damper on tool vibration and cutting properties. The results of the study revealed remarkable improvements in various performance metrics. The constrained layer damper demonstrated an impressive 98% reduction in tool vibration, signifying its efficacy in dampening vibrational forces during the boring operation. Furthermore, a substantial 83% decrease in surface roughness was observed, indicating enhanced machining precision and surface finish. The constrained layer damper also exhibited a noteworthy 97.5% reduction in tool wear, highlighting its ability to significantly prolong tool life under challenging machining conditions.

Milling of TiBbm2 Particle Reinforced High-Modulus Steel

TiB2 particle reinforced high-stiffness steel is one of the composite materials that aim to improve Young’s modulus by compositing TiB2 particles into a stainless steel base phase. This material is designed to exhibit higher rigidity and strength than conventional iron-based materials by using TiB2 particles as the reinforcing phase, and is expected to reduce the weight of high-load components in engines. For this reason, tool life is very short when machining this material. Therefore, high Young’s modulus steel containing TiB2 particles is known to be one of the most difficult-to-cut materials. The purpose of this study was to investigate how to extend tool life in the milling of high-Young’s-modulus steel. Cutting speed dependence of tool life was investigated by end milling using a binderless CBN tool with excellent hardness and bending strength. In addition, the tool damage mechanism was also investigated. The results showed that tools composed of binderless CBN tool have a longer life than conventional CBN tool. In this type of binderless CBN tool, the tool wear rate tended to increase with increasing cutting speed. In addition, the longest tool life was obtained at a cutting speed of 1.25 m/s, though wear rate increased at a boundary cutting length of 1300 m. The wear rate was found to increase with increasing cutting speed. Temperature measurement results indicate that the primary cause of tool damage was mechanical wear, as the temperatures were much too low for a reaction between cBN and Fe. Friction tests revealed scratch marks on the tool originating from crushed cBN particles produced by the crushing of the cutting edge. This indicates that wear is accelerated by the high frictional energy of the cBN powder rubbing against the flank face.

Boiling of Coolant Near the Cutting Edge in High Speed Machining of Difficult-to-Cut Materials

This study investigates film boiling of coolant as a cooling inhibitor in a narrow wedge-shaped space between the tool flank face and the machined surface of a workpiece, observed during high-speed turning of stainless steel SUS304 and nickel-based superalloy Inconel 718. The boiling, likely triggered by high surface temperatures at both the face and surface close to the cutting edge, impedes coolant access to the tool tip area and efficient cooling. Therefore, the impact of coolant pressure on the boiling zone size was initially explored across pressures ranging from 0.1 to 20 MPa. A burn mark band due to coolant boiling, distinctly visible on the flank face of an insert with a yellow hard coating, expanded over cutting time. The film boiling area width, or the distance from the flank wear area to the band, decreased with increasing coolant pressure, reflecting the enhanced cooling ability and tool life with high-pressure coolant. Applying Boyle–Charles’ law to film boiling indicated that vapor pressure was directly related to coolant velocity rather than pressure. In contrast, the boiling area width increased with increasing cutting speed.

Influence of Reverse Finishing on Characteristics of Drilling Surface

Aluminum alloys are often used in automobile and aircraft parts that require higher dimensional accuracy and durability. Drilling is often used in the machining process of these products and accounts for about 60% of the machining performed on these products. Deterioration of finishing surface accuracy in drilling causes problems such as decreased tool life due to wear and increased cost due to the introduction of the finishing process. The objective of this study is to evaluate the finished surface characteristics in the drilling of aluminum alloys using reverse finishing, with a focus on the cutting direction of finishing, with respect to the roughing direction. The torque and thrust force are smaller in reverse finishing than in forward finishing. The reduction effects of cutting force in reverse finishing were more significant when the finishing depth of cut was smaller in relation to the roughing-affected layer. Under conditions where the finishing depth was equal to or greater than the roughing-affected layer, it was possible to reduce cutting forces and improve surface roughness while obtaining compressive residual stresses equivalent to forward finishing.

Investigation of tool life in the single-crystal diamond turning of AISI 420 using high-frequency ultrasonic vibration

Investigation of tool life in the single-crystal diamond turning of AISI 420 using high-frequency ultrasonic vibration

Investigating the Wear Mechanism of TiAlN/TiN PVD-Coated WC Inserts in End Milling of Incoloy 925 Under Synergy of Bio-Degradable Fatty Acids and Nano-Metallic Solid Lubricant

Abstract Rapid tool wear in machining difficult-to-cut material is a significant challenge since it is related to tool cost, surface integrity of machined components, and power consumption. The reduction in tool wear may be accomplished by cutting fluids, especially in modern biodegradable fatty acids. Because of its high lubricity, coconut oil is the best choice for lubricating fatty acids. However, this oil has poor heat transfer properties. Hence, to further improve its properties, copper (Cu) nanoparticles (NPs), which have a high thermal conductivity to cost ratio compared to other nanoparticles in addition to anti-frictional and anti-wear properties (due to self-repairing properties caused by their low shear strength and easy deposition on contacting surfaces), have been dispersed in coconut oil, thus creating a nano-lubricant (nanofluid). It is found that synthesized nano-lubricants perform better in thermo-physics and tribology than pure coconut oil. Further, research has been carried out on the combined effects of coconut oil and 0.3 vol% Cu-NPs on Incoloy 925's end milling performance and tool wear mechanism (viz., coating delamination, adhesion, abrasion, and oxidation). It is found that tool wear-rate is reduced, which in turn increases tool life, due to effective cooling and lubrication when nanofluid-based minimum quantity lubrication (NMQL)-assisted machining is performed rather than dry and pure oil-based minimum quantity lubrication (MQL) conditions. Consequently, energy consumption in machining and surface quality of machined components are improved.

Research on Fault Diagnosis Method of CNC Machine Tools Based on Integrated MPA Optimised Random Forests

INTRODUCTION: Intelligent diagnosis of CNC machine tool faults can not only early detection and troubleshooting to improve the reliability of machine tool operation and work efficiency, but also in advance of the station short maintenance to extend the life of the machine tool to ensure that the production line of normal production.OBJECTIVES: For the current research on CNC machine tool fault diagnosis, there are problems such as poorly considered feature selection and insufficiently precise methods.METHODS: This paper proposes a CNC machine tool fault diagnosis method based on improving random forest by intelligent optimisation algorithm with integrated learning as the framework. Firstly, the CNC machine tool fault diagnosis process is analysed to extract the CNC machine tool fault features and construct the time domain, frequency domain and time-frequency domain feature system; then, the random forest is improved by the marine predator optimization algorithm with integrated learning as the framework to construct the CNC machine tool fault diagnosis model; finally, the validity and superiority of the proposed method is verified by simulation experiment analysis.RESULTS: The results show that the proposed method meets the real-time requirements while improving the diagnosis accuracy.CONCLUSION: Solve the problem of poor accuracy of fault diagnosis of CNC machine tools and unsound feature system. 

Machining of Ni-based superalloys using CAPVD coated carbide tools

The ever-increasing demand for cost-effective machining of Ni (Nickel) based superalloys has made it necessary to explore nanocomposite coatings as a potential surface engineering solution. The present study aims to investigate the variation in machining performance of new-generation hard wear-resistant coatings in milling of IN 718 (Inconel 718), IN 625 (Inconel 625), and IN 617 (Inconel 617). TiAlSiN and CrAlSiN coatings were grown in-house over tungsten carbide (WC) milling inserts through the cathodic-arc PVD route. The TiAlSiN coating improved the tool life by 80% and 60% in the case of IN 718 and IN 625, respectively. However, in the case of IN 617, the TiAlSiN-coated tool could not even reach the uncoated tool life. The CrAlSiN coating, on the other hand, improved the tool life by more than 200% in the milling of IN 617. Tool-chipping was the dominant failure mode among all observed, which included flank wear and workpiece adhesion. The repeated adhesion and removal of the workpiece layer from the tool surface was a major cause of tool failure. The coating layer delayed the initiation of the chipping and prolonged the flank-wear-dominated machining time, resulting in improved tool life. The wear resistance of coatings in machining different workpiece materials was greatly influenced by the relative affinity of constituting elements of workpieces for employed coatings. The machining chips exhibited shear bands and saw-tooth (serrated/segmented) morphology in almost all cases. The degree of segmentation showed a direct correlation with tool life.The present work helps identify the optimum coating and machining conditions for three different grades of Ni-based superalloys. Additionally, the underlying mechanisms were analyzed and discussed with scientific observations.

Influence of clean cooling medium on the hard drilling performance and machined surface integrity of 42CrMo steel

42CrMo ultra-high strength steel has high strength and fracture toughness, which is widely used in key components, such as gears, connecting rods and molds. This type of workpiece material, especially after quenching and hardening treatment, still has prominent issues with hole machining. In this work, the clean cutting media, including dry, cold air and liquid nitrogen (LN2), are selected to investigate the hard drilling performance and machined surface integrity of 42CrMo steel. The feasibility of extending tool life and improving hole machining quality is explored through clean cooling medium. The cutting force and cutting temperature are lower under cold air and LN2 conditions than that under dry cutting conditions. The tool life is extended under cold air and LN2 conditions. The low temperature brought by LN2 promotes the transformation from folded to lamellar for chip free surface. The degree of chip curling becomes larger and easier to break and discharge, which reduces the unfavorable effects of chip clogging. The thermal damage phenomenon on the hole wall surface is disappeared. The surface roughness is reduced by 37.3%, and the maximum microhardness is increased by 6.6%, which significantly improves the machined surface integrity of holes. This work demonstrates the feasibility of improving the machinability of harnessed ultra-high strength steel by LN2 cooling.

Theoretical and experimental investigation of ultrasonic cutting kinematics and its effect on chip formation and surface generation in high-frequency ultrasonic vibration-assisted diamond cutting

Ultrasonic vibration-assisted cutting (UVAC) is regarded as a feasible technology to machine difficult-to-cut materials. High-frequency ultrasonic vibration-assisted cutting (HFUVAC), with a working frequency of more than low and medium frequency (20-60kHz), has been reported to improve material machinability and prolong tool life. This paper presents a comprehensive investigation of the ultrasonic cutting kinematics and the generated chip/surface formation process in HFUVAC of a 316l stainless steel workpiece. First, the ultrasonic cutting kinematics was analyzed and verified by comparing the experimental and theoretical surface texture under different nominal cutting speeds. Based on the ultrasonic cutting kinematics and the simulated strain/stress distributions, the chip and surface formation between conventional cutting (CC) and HFUVAC was analyzed. More importantly, the incremental cutting mode was defined when the cutting stroke, namely the effective cutting length in one vibration cycle was less than 800 nm. The results show that in the incremental cutting mode, defect-free surface was achieved due to suppressed large deformation and friction action. Finally, HFUVAC of the sinusoidal microstructure was performed under the incremental cutting mode, achieving optical requirements with nanometer-scale surface roughness and submicrometric form accuracy, which validates the technical feasibility in HFUVAC of micro-structured surfaces.

Iron ion detection and life cycle assessment of cutting fluid based on photoluminescent nitrogen-doped carbon quantum dots

Cutting fluid (CF) ensures machining accuracy and improves tool life in machining, which is of great significance for its impurity content detection and life cycle evaluation. In this paper, citric acid and arginine were used as carbon and nitrogen sources, photoluminescent (PL) nitrogen-doped carbon quantum dots (N-CDs) with a particle size ranging from 8 to 14 nm and well dispersion in water-based CF were synthesized by a one-pot hydrothermal reaction method. The N-CDs have the best signal under 360 nm ultraviolet light excitation, which well avoids the autofluorescence of the CF. The N-CDs dispersion have good selectivity and linearity in the Fe3+ concentration range of 2 to 80 μM, and the detection limit is 1.2 μM. The N-CDs were used to detect the concentration of Fe3+ in CF with different working hours, and the results were consistent with the results of coupled plasma emission spectroscopy. This study provides an intelligent sensing platform for the highly sensitive and selective detection of Fe3+ in the CF environment, and provides a promising strategy for the evaluation of the CF lifetime.

A State of the Art on Sustainable Metal Working Fluids in Machining Applications

Metalworking fluids (MWFs) play a crucial role in machining processes by lubricating and cooling cutting tools, reducing friction, and improving overall machining efficiency. These fluids can be classified into various types, including cutting oils, water-based fluids, and semi-synthetic or synthetic fluids. Cutting oils are often mineral-based, providing excellent lubrication in heavy-duty applications. Water-based fluids, on the other hand, are more environmentally friendly and commonly used in light to moderate machining operations. Semi-synthetic and synthetic fluids offer a balance between performance and eco-friendliness, incorporating additives to enhance their properties. Proper selection and management of MWFs are essential for optimizing tool life, surface finish, and overall productivity in metal machining applications. Research has shown that the cost of cutting fluid in machining constitutes 17% of the total production cost. In the same research, it was stated that the cutting tool cost was around 4%. This review provides an overview of the current advancements in sustainable MWFs within machining applications. It explores state-of-the-art technologies, formulations, and practices aimed at minimizing environmental impact while maintaining optimal performance in metalworking processes. The review encompasses eco-friendly additives, recycling methods, and emerging trends in the development of MWFs, emphasizing the importance of sustainable practices in the manufacturing industry.

Analysis of Tool Load Concerning the Cross-Sectional Size of Removed Material

High-feed milling (HFM) represents a progressive manufacturing technology that has recently found widespread application across various industries. HFM is characterized by high machining speed, reduced cycle times, increased overall productivity, and increased tool life. Due to its versatility, HFM is a suitable technology for the application of various materials. The study deals with experimental analysis of cutting forces, machined surface integrity, and statistical evaluation in high-feed machining. In the present study, nickel-copper-based alloy (Monel) was chosen as the machined material, employing HFM with a monolithic ceramic milling cutter. The Monel material is characterized by its excellent mechanical properties and chemical resistance in harsh environments. During machining, cutting forces were recorded in three mutually perpendicular directions. This paper delves into the analysis of the impact of the depth of cut (ap), width of cut (ae), and lead-in angle (ε). The chosen evaluation characteristics encompass the tool load, primary profile, and the attained roughness of the machined surface. It is noteworthy that the technology under consideration predominantly aligns with the roughing phase of the manufacturing process. Additionally, the investigation incorporates a statistical analysis of the response surface pertaining to the cutting force components, namely Fx, Fy, Fz, and the resultant cutting force F.

Orthogonal array and artificial neural network approach for sustainable cutting optimization machining of 17-4 PH steel under CNC wet turning operations

Sustainable manufacturing strives to increase output while minimizing resource usage, costs, and environmental impact. Tool longevity is crucial, considering material, power, and resource consumption. Challenges like chip removal, heat, and friction necessitate effective solutions. Cutting fluids, like rice bran oil, reduce temperatures, friction, and enhance tool life and surface quality. Research focuses on using rice bran oil with a TiAlN tipped tool to minimize friction and cutting forces. Taguchi's robust design and L-9 orthogonal array reduce experimental trials. Controllable factors include speed, feed, depth of cut, and rice bran oil flow rate, with surface roughness as the performance metric. Taguchi analysis improves turning performance, particularly with 17-4 PH stainless steel. Rice bran oil reduces frictional forces, enabling improved surface quality across all samples, promoting sustainability. Surface roughness (Ra) is notably influenced by feed rate and rice bran oil, contributing 58.06% and 49.5%, respectively. This research underscores the potential of optimizing cutting fluid and process parameters to enhance sustainability in manufacturing.

Digital Twin in Process Planning of the Additive and Subtractive Process Chain for LMD and Micro Milling of Stainless Steel

Abstract Additive and subtractive (Add/Sub) manufacturing processes are increasingly being combined to produce complex parts with unique geometries and properties. However, the design of such combined processes is often challenging as it requires a deep understanding of the interaction between the different processes. On the other hand, digital twin (DT) technology has become a powerful tool in recent years for optimizing manufacturing processes. This paper explores the use of the digital twin technology for a holistic process planning of combined additive and subtractive processes. The paper describes the integration of laser metal deposition (LMD) and micro-milling prediction models of resulting geometry (width and height), hardness and surface roughness into the digital twin. This is then used for combined process planning to achieve different target values regarding resulting geometry and surface roughness. For the planning of this combined process chain, further criteria such as tool life, energy and process time are considered in the optimization, showing the potential for sustainable and efficient production. Sensorless cutting force estimation is also used to detect small cutting forces, with the potential to use this as a soft sensor for roughness estimation. The measured width, height and roughness as a result of the process parameters suggested by the optimization algorithms showed a Mean Absolute Percentage Error (MAPE) of 4%, 17% and 16% respectively.

Technical review on design optimization in forging

AbstractForging is a traditional and important manufacturing technology to produce various high strength products and is widely used in engineering fields such as automotive, aerospace and heavy industry. To produce highly accurate product, underfill that the material is not filled into the cavity should strongly avoided. For material saving and near-net product, flash should be minimized. To make the tool life long, it is preferable to produce product with low forging load. It is also preferable to uniformly deform the billet as much as possible for high strength product. Crack is a crucial defect and should strongly be avoided. Therefore, many requirements are taken into account in order to produce the forged product. To meet the requirements, design optimization in forging coupled with computer aided engineering (CAE) is an effective approach. This paper systematically reviews the related papers from the design optimization point of view. For the billet or die shape optimization, the papers are classified into four approaches. The process parameters optimization such as the billet temperature, the die temperature, the stroke length and the friction coefficient is conducted, and the related papers are also classified into four categories. The design variables and the objective function(s) used in the papers are clarified with the design optimization technique. The multi-stage forging including the hammer forging for producing complex product shape is also briefly reviewed. Finally, major performance indexes and the future outlook are summarized for the further development of design optimization in forging.

Tool Coating Development: A Historical Overview

The development of tool coatings over time is evidence of human inventiveness and the ongoing effort to enhance machining techniques. Tool performance, tool life, and machining operation optimization have been the driving forces behind the development of tool coatings from the dawn of civilization to the present day of advanced materials research. The development of tool coatings from antiquity to the present is covered in detail in this research paper's extensive history. An analysis is conducted of significant turning points, discoveries, and technical developments in the tool coatings sector, emphasizing the revolutionary influence these developments have had on a range of industries

Fundamental investigation on the time-variance of process stability

AbstractDisturbance factors, such as self-excited tool vibrations, limit the performance of modern machining processes and thus restrict the quality, productivity and sustainability of industrially manufactured components. The dynamic process stability is subjected to significant variances especially at the beginning of the tool life. To precisely quantify these variances, series of milling tests were conducted and analyzed using tools made of high speed steel (HSS) and cemented carbide for the machining of EN AW-7075. In all test series, a critical initial decrease of the stability limit was detected directly at the beginning of the tool life. In the following, a significant increase and subsequent almost constant stability limit was observed. In the case of the HSS cutters the achieved stability limit exceeded the initial level substantially. An increase in the process forces and flank wear was also measured over tool life but the progression cannot directly explain the extend and characteristics regarding the stability limit. The findings described have a considerable impact on the appropriate design of manufacturing processes and experiments to determine the dynamic stability of cutting operations.