Tool Life Tests Research Articles

Bi-layer cBN-based composites reinforced with oxide and non-oxide microfibers of refractory compounds

Research into new composites utilizing cubic boron nitride (PcBN) shows promise for enhancing cutting tool performance. The unique properties of these materials stem from the addition of microfibers made of refractory compounds to their structure. This study looks at developing two-layer composites based on cBN group BL, reinforced with SiCw and Al2O3w microfibers. The goal is to improve tool stability when cutting hardened steels with impact loads. PcBN composite samples were made by sintering a mixture of cBN powder with bundles and microfibers under 7.7 GPa pressure. Bond material selection was based on analyzing the relationship between Poisson's ratio (η) and plasticity parameter (G/B). The density, Young's modulus, Poisson's ratio, and hardness of the composites were determined, and the microstructure of samples with TiCN bond was studied. Tool-life tests were conducted on two-layer cutting inserts made of PcBN reinforced with SiCw and Al2O3w microfibers during the machining of hardened KhVG steel (HRC 55) under impact loads at cutting speeds of 100 and 200 m/min.

Reliability analysis of PVD-coated carbide tools during high-speed machining of Inconel 800

Predicting the cutting tool life is crucial for effectively managing machining costs, ensuring product quality, maintaining equipment availability and minimising waste in machining processes. When machining heat-resistant superalloys such as Inconel, the concern for tool life becomes even more pronounced. Cutting tool failure is a complex phenomenon that depends on several variables, including tool type and material, workpiece material, machine tool type and machining parameters. Traditional run-to-fail tests to predict tool life are costly and time-consuming. To address these challenges, accelerated degradation testing (ADT) offers a promising solution. ADT involves subjecting the component to higher levels of parameters, causing it to fail faster than under normal conditions. This approach saves time and reduces expenses associated with tool life tests for valuable workpieces. In implementing the concept of ADT, the experimental cutting speed [Formula: see text] values are selected much higher than the normal usage levels in the present study. The tool life tests are performed at three levels of [Formula: see text], feed rate [Formula: see text], depth of cut [Formula: see text] and tool nose radius [Formula: see text] using the Taguchi L9 orthogonal array. Parametric statistical approaches, that is, accelerated failure time (AFT) models, are applied with distributions, namely the Weibull, lognormal and log-logistic distributions, to analyse the cutting tool’s reliability based on predictor variables. Various tool wear modes are considered criteria for tool failure. The comparison is made among the mean time to failure (MTTF) of cutting tools as predicted by various fitted models. Additionally, a favourable tool failure pattern is observed when using the middle level of [Formula: see text] and operating at relatively higher [Formula: see text] values while ensuring that [Formula: see text] and [Formula: see text] values fall within the recommended range. The proposed approach has the potential for diverse applications, including assessing the reliability of cutting tools and tool condition monitoring.

A New Architecture Paradigm for Tool Wear Prediction during AISI 9840 Drilling Operation

In conventional machining processes based on the chip removal mechanism, the progressive wear of the tool determines a change of the geometric characteristics of the cutting edge. Tool wear is a complex phenomenon and related tool life depends on several factors, such as cutting parameters, lubrication, and tool-workpiece relative trajectories. Tool wear progression affects the quality of the machined parts, making the tool replacement necessary even before its breakage. Moreover, in industrial practice, tool replacement cannot depend on the subjectivity of the operator, thus, the definition of an optimized strategy for cutting tool wear monitoring before tool failure is mandatory. This work compares Random Forest and Neural Network models for predicting tool wear in drilling. For the development of predictive models, tool life tests were performed by drilling through holes on AISI 9840 steel parts, with a coated tungsten carbide drill of 8 mm of diameter and by using constant cutting parameters. Flank wear of the tool was monitored. A set of statistical features computed from the vibration signals, the acoustic emission signals, the power signals and the torque signals constitute the input of the algorithms. The classification accuracy was 88% and 91% for Neural Network and Random Forest models respectively. In order to correctly define the tool replacement policy during production, the developed Random Forest model has been implemented in an industry, through production management software, achieving promising results.

Evaluation of tribo-vibration characteristics of the finishing turning process of heat-resistant structural steel 20MnMoNi5-5

This article is devoted to determining the rational range of cutting speeds during longitudinal finish turning of heat-resistant steel 20MnMoNi5-5 based on a set of tribological and vibration parameters of the cutting process. Turning workpieces with diameters D=120 mm made of 20MnMoNi5-5 steel with T15K6 carbide plates without cooling at finishing feeds and allowance values at cutting speeds of 100-220 m/min was carried out and studied. It was experimentally established that the local minimum for vibration energy was located within the speed range of 190-220 m/min. According to the results of tool life tests in this speed range, the wear rate of the cutting inserts was also minimized and the operating time of the tool was increased, making it possible to ensure the required surface roughness Ra≤1.6 μm.

Research solution for automatic hole quality analysis when drilling fiber-reinforced composites

Fiber-reinforced polymers are highly demanding composites in aerospace and automotive areas because of their excellent mechanical properties such as stiffness and strength-to-weight ratio. The drilling remains the major machining operation applied to composites to provide high-quality holes for joints between parts. Due to composites plied structure, the drilling is accompanied with unusual form metal cutting defects such as delamination and uncut fibers around the drilled hole. Considering that the tool life of some drills reaches over thousands of holes, the research of composites machinability becomes difficult due to demanded labor intensity in manual inspection of the hole quality. Therefore, this paper develops the research solution for automatic analysis of the hole quality in drilled fiber-reinforced materials. The paper proposes a complex of solutions aimed to speed up the analysis of the hole quality when composites drilling. The solution consists of the developed vacuum table, robot arm with high-speed camera, developed top and bottom lightning systems, and Image Processing algorithms for defect detection from captured images. The paper results show how the developed solution can be used for high routine research activities. The output data, including tested 72 cutting data parameters and full-size tool life test, allowed identifying the operational window for high-speed steel drills and the range of tool life, where drill ensures a certain hole quality. The paper shows the efficiency of the developed research solution can reach 5 s per hole including drilling and full cycle of measurements having measurement error of 1–3%.

Comparative study of drilling super austenitic stainless steel with external applications of reduced quantity nanofluid and flooded bio-lubricant

AISI 904L is a super austenitic stainless steel (SASS) with excellent corrosion resistance and good mechanical strength at high temperatures that can be applied in extreme operational conditions. Consequently, it has low machinability. Research involving SASS drilling is scarce in the literature. Thus, this work aims to evaluate the TiAlN-coated carbide drill life associated with thrust force and torque in the full-hole drilling of the Ultra® 904L under external lubrication with a 100-mm/min feed rate. Nanofluid-based reduced quantity lubricant (2.0 L/h) at 840-rpm spindle speed and flood bio-lubricant conditions (540 L/h) at 840- and 1260-rpm spindle speeds were applied, totaling three tool-life tests. Digital image analysis showed that the failures in the main cutting edges occurred due to chipping resulting from the rupture of the built-up edge. The drill wear did not reach expressive values. Low tool life was observed with nanofluid in reduced quantity (E1 test, 0.67 min) and flood condition with 1260 rpm (E3 test, 1.34 min). The longest drill life was registered for 840 rpm with flood biofluid (E2 test, 8.04 min). Lastly, a growth of 11% in thrust force and 9% in torque were noted when increasing the lubricooling flow from the E1 to E2 test; however, there was a reduction of 31% and 42% when raising the spindle speed from E2 to E3 test. The flood condition resulted in a longer drill life and smaller thrust force and torque values (at least 20% lower), which are associated with chip deformation, hardness, and friction coefficient reductions due to increased cutting speed and temperature. Moreover, built-up edges were formed during the drilling of all the holes.

Cutting tool remaining useful life prediction based on robust empirical mode decomposition and Capsule-BiLSTM network

In industrial production, effectively predicting the remaining useful life (RUL) of cutting tools can avoid overuse or underuse, which is of great significance for ensuring the processing quality of products and reducing enterprises’ production costs. This paper proposes a new method for RUL prediction of cutting tools based on robust empirical mode decomposition (REMD) and capsule bidirectional long short-term memory (Capsule-BiLSTM) network to improve accuracy. On one hand, new state features are extracted using REMD as the input of the deep learning network. On the other hand, a Capsule-BiLSTM network structure is designed to achieve RUL prediction of cutting tools by connecting the four layers. Finally, the effectiveness of the proposed method is verified by a series of cutting tool life tests. Comparison with some mainstream methods indicates that the proposed method has more advantages in RUL prediction of cutting tools with the average accuracy reaching up to 93.97%.

Potential of high-feed milling structured dies for material flow control in hot forming

Hot forming processes of complex parts with small cavities demand high-performance tools made of hardened steels. Their surface can be tribologically modified in order to control the material flow for improving the mold filling of functional elements. Surface structuring here offers great potential for adjusting the frictional properties and thus controlling the material flow in forming processes. In this study, high-feed milling (HFM) of surface structures in hot work tool steel (HWS) components is investigated. The process performance was determined by cutting force measurements and tool life tests. The achievable surface topography was measured and evaluated in terms of structure quality and roughness parameters, and friction properties were derived based on the results. In a hot ring compression test, the influence of certain structure variants on the material flow was analyzed. The results conclude that HFM is a suitable process for structuring HWS components with constant structure quality and low tool wear. In addition, a variety of structures showed significant influence on the hot ring compression test. This indicates a relevant potential of HFM for the modification of hardened tool surfaces to improve the performance of hot forming processes and increase the manufactural quality and productivity.

A holistic approach for gear skiving design enabling tool load homogenization

Gear skiving is a highly productive manufacturing process for internal gears. Due to its challenging cutting conditions often insufficient tool life is achieved and localized wear occurs. There is a lack of tool parameters in process design that allow for an uniform and comparable characterization of the process kinematics and tool geometry. In this paper, a new method for calculating process kinematics and tool profile based on parameters of profile-shifted conical gears and an approach for tool load homogenization are presented. The high potential of the methods is demonstrated by comparative tool life tests with an improvement of 300%.

Machinability analysis in high speed turning of Ti–6Al–4V alloy and investigation of wear mechanism in AlTiN PVD coated tungsten carbide tool

Titanium alloys are one of the most critical and prominently used materials in automotive, aerospace, and biomedical application due to their superior strength to weight ratio. The very property that makes it a suitable material for such applications also makes it challenging to machine. In this study, an attempt has been made to understand the machinability of Ti–6Al–4V titanium alloy at high cutting speeds in turning. A full factorial method and Analysis of Variance (ANOVA) technique were used to conduct 18 different experimental runs and determine the significance of variables that are responsible for the variation in average surface roughness (Ra) and forces. The results show that feed rate is the single most significant factor for Ra, whereas the contribution of feed and depth of cut are more for the forces, followed by cutting speed. Tool life tests were conducted with AlTiN PVD coated tools at three different cutting speeds, and SEM analysis to evaluate the wear mechanism revealed that abrasive wear, notching, and diffusion were predominant which accelerated the wear rate. Although machining studies on Ti6Al4V at low cutting speeds are well established, the novelty of the study is to perform a comprehensive analysis to evaluate the machinability and study wear mechanism using AlTiN coated tungsten carbide tool at high cutting speeds.

Development of generalized tool life model for constant and variable speed turning

In this research, a generalized tool life modelling for considering non-stationary cutting conditions was developed . In particular, for the first time in literature, the model was conceived for predicting the life of the tool when spindle speed variation SSV, one of the most effective techniques for suppressing regenerative chatter vibrations, is used. The proposed formulation takes into account the main cutting parameters and the parameters associated to the SSV. A dedicated experimental campaign of turning tests was executed and the data were used for modelling purposes. The model validation was carried out performing additional tool life tests. According to the analyzed technological scenario, it was found that the generalized formulation can be used for predicting the tool life both at constant spindle machining CSM and adopting SSV with the maximum estimating error of 6%.

Optimisation of cutting fluid concentration and operating parameters based on RSM for turning Ti\u20136Al\u20134V

The paper details experimental and optimisation results for the effect of cutting fluid concentration and operating parameters on the average surface roughness (Ra) and tool flank wear (VB) when flooded turning of Ti-6Al-4V using water-miscible vegetable oil-based cutting fluid. Cutting fluid concentration, cutting speed, feed rate, and cutting tool were the control variables. Response surface methodology (RSM) was employed to develop an experimental design and optimise Ra and VB using linear models. The study revealed that cutting fluid concentration has a little influence on Ra and VB performance, while Ra was strongly affected by feed rate and cutting tool type. The developed empirical model also suggested that the best parameters setting to minimise Ra and VB are 5%, 58 m/min and 0.1 mm/rev for cutting fluid concentration, cutting speed, and feed rate, respectively, using H13A tool. At this setting, the predicted surface roughness and tool wear were 0.48 and 30 μm, respectively. In the same vein, tool life and micro-hardness tests were performed at the suggested optimum cutting condition with different cutting speeds. A notable decrease in tool life (82.3%) was obtained when a higher cutting speed was used.

Experimental investigation of the effects of cryogenic cooling on tool life in Ti6Al4V milling

In this paper, the results of an experimental campaign of cryogenic milling are presented and discussed. For this purpose, a specific experimental setup that allowed to feed the liquid nitrogen LN through the tool nozzles was used. Tool life tests were carried out at different cutting speeds. The tool duration data were collected and used to identify the parameters of the Taylor’s model. Different end-of-life criteria for the tool inserts were even investigated. The achieved results are compared to those obtained using conventional cooling. It was observed that at low cutting velocity, conventional cooling still assures longer tool lives than in cryogenic condition. Since in cryogenic milling the increasing of the cutting velocity is not so detrimental as in conventional cutting, at high cutting speed (from 125 m/min) longer tool durations can be achieved. Statistical analyses on the model parameters were carried out to confirm the presented findings. The analysis of the effect of the cooling approach on the main wear mechanisms was also reported. At low cutting speed, adhesion and chipping phenomena affected the tool duration mainly in cryogenic milling.

Machinability Analysis of Inconel 718 Superalloy with AlTiN-Coated Carbide Tool Under Different Cutting Environments

Inconel 718 superalloy is hard-to-machine materials due to low thermal conductivity, high hardness, and chemical reactiveness with high-temperature tool materials. Despite these negative material characteristics, it is widely used in gas turbine engine manufacturing and aviation, where dimensional accuracy and surface integrity are very important. Finish turning, the last machining process, helps to determine the material's working life and surface quality. Thus, this study focused on improving the Inconel 718 superalloy's machinability performance, and finish turning processes were performed using different cutting environments with AlTiN-coated carbide tool. Using dry, minimum quantity lubrication and vortex tube as cooling methods aim to reduce operating costs and develop environmentally friendly methods that will affect employees and the environment less. The experiments were carried out based on Taguchi L9 experimental design. The effects of cutting conditions and machining parameters on tool wear, cutting zone temperature, cutting forces, and surface roughness were evaluated separately. Then, multiresponse optimization was performed using Grey-Taguchi Relational Analysis for the cutting zone temperature, cutting force, and surface roughness. According to the experimental results, the optimum cutting conditions were established by the MQL cooling method, 70 m/min cutting speed, and 0.05 mm/rev feed rate. Besides, SEM images were taken from the tools to investigate the performance of the cutting tools. SEM and EDS analyses were conducted to identify the variations onto cutting tools due to the tool life tests performed with three cooling methods concerning the optimum cutting parameters.

Turning machinability of alloyed ductile iron compared to forged EN 1.7131 steel

Abstract Recently, many applications have used austempered ductile iron due to its high hardness, strength, toughness, and wear resistance. These superior properties make austempered ductile iron an alternative material to forged steels. However, machining of austempered ductile iron is challenging because of its high hardness and strength. In this study, machining operations were performed on the alloyed ductile iron workpiece to investigate the machinability of the material prior to the austempering process. This experimental study was carried out on EN 1.7131 alloy steel and alloyed ductile iron using single point carbide inserts under dry cutting conditions. A constant feed of 0.1 mm × rev-1, constant depth of cut of 1 mm, and variable cutting speeds were selected as input parameters, whereas tool life is considered as a response parameter. The tool life tests were accomplished considering flank wear as tool life criterion according to ISO 3685. The results of this study indicated that although the machinability of ductile iron is 88 % of the normalized forged EN 1.7131 steel for a 60 minutes’ tool life, identical tool life was observed for both materials at 96 m × min-1cutting speeds.

Turning machinability of alloyed ductile iron compared to forged EN 1.7131 steel

Abstract Recently, many applications have used austempered ductile iron due to its high hardness, strength, toughness, and wear resistance. These superior properties make austempered ductile iron an alternative material to forged steels. However, machining of austempered ductile iron is challenging because of its high hardness and strength. In this study, machining operations were performed on the alloyed ductile iron workpiece to investigate the machinability of the material prior to the austempering process. This experimental study was carried out on EN 1.7131 alloy steel and alloyed ductile iron using single point carbide inserts under dry cutting conditions. A constant feed of 0.1 mm × rev-1, constant depth of cut of 1 mm, and variable cutting speeds were selected as input parameters, whereas tool life is considered as a response parameter. The tool life tests were accomplished considering flank wear as tool life criterion according to ISO 3685. The results of this study indicated that although the machinability of ductile iron is 88 % of the normalized forged EN 1.7131 steel for a 60 minutes’ tool life, identical tool life was observed for both materials at 96 m × min-1cutting speeds.

Investigation of cutting conditions on tool life in shoulder milling of Ti6Al4V using PVD coated micro-grain carbide insert based on design of experiments

Tool life prediction is generally of great importance in all metal cutting processes, including milling titanium. In this paper, tool life testing was performed based on full factorial design. The cutting speed and width varied between 100 and 120 m/min, and 10 and 70 percent of tool diameter, respectively. All cutting tests were performed in Ti6Al4V under wet conditions using Physical Vapor Deposition (PVD) coated milling inserts. The wear limit was set to 0.2 mm. The data were analyzed using multiple regression analyses, where the method of least squares was applied. A mathematical tool life model was established. Roughly, for each one percent increase in cutting width, tool life decreases on average by one percent, and an increase in cutting speed by a percent leads to a decrease in tool life by four percent. The adequacy of the model was verified using analysis of variance at 95% confidence level. Tool life contour in cutting width and speed was generated from the model. The results can be used for selecting optimum cutting parameters for providing a desired tool life or maximum metal removal rates for a favored tool life.

Study on Technological Effects of a Precise Grooving of AlSi13MgCuNi Alloy with a Novel WCCo/PCD (DDCC) Inserts.

The WCCo/PCD (Diamond Dispersed Cemented Carbide—DDCC) manufactured with the use of PPS (pulse plasma sintering) are modern materials intended for cutting tools with the benefits of tungsten carbides and polycrystalline diamonds. Nevertheless, the cutting performance of DDCC materials are currently not recognized. Thus this study proposes the evaluation of technological effects of a precise groove turning process of hard-to-cut AlSi13MgCuNi alloy with DDCC tools. The conducted studies involved the measurements of machined surface topographies after grooving with different cutting parameters. In addition, the tool life and wear tests of DDCC inserts were conducted during grooving process and the obtained results were compiled with values reached during machining with cemented carbide tools. It was also proved that grooving of AlSi13MgCuNi alloy with DDCC inserts enables 5 times longer tool life and almost 3-fold increase of cutting path compared to values obtained during grooving with H3 and H10 cemented carbide inserts. Ultimately, the feed value of f = 0.15 mm/rev and cutting speed in a range of 800 m/min ≤ vc ≤ 1000 m/min during grooving with DDCC inserts can be defined as an optimal machining parameters, enabling the maximization of tool life and improvement in surface quality.

Effects of cryogenic treatment types on the performance of coated tungsten tools in the turning of AISI H11 steel

This study investigated the effects of the cryogenic treatment on cutting tool performance in the turning of AISI H11 steel. In the experiments, TiCN/Al2O3/TiN-coated tungsten carbide tools were used. Shallow cryogenic treatment was applied for 6h at −80°C (SCT6), deep cryogenic treatment at −196°C for 6h (DCT6), and deep cryogenic treatment at −196°C for 24h (DCT24). Turning tests were conducted at three cutting speeds (200, 240, and 280m/min), three feed rates (0.15, 0.18 and 0.21mm/rev), and a 0.6-mm depth of cut under dry cutting conditions. Experimental results showed that the cryogenic treatment increased the abrasion resistance of the cutting tool. The best cutting tool wear and surface roughness performance was obtained with the DCT24 tool. As a result of the tool life test, DCT24 tool wore 14.5% less than U tool. In terms of surface roughness, DCT24 tool improved up to 16.5% compared to the U tool. Moreover, it was determined that the cryogenic treatment provided an increase in the hardness of the cutting tools. The highest hardness increase also occurred in the DCT24 tool (10.87%). In addition, cryogenic treatment types were optimized for flank wear and surface roughness using the Taguchi method, and the effect levels of the cutting tools and cutting parameters were determined via analysis of variance. According to ANOVA results, for flank wear, the parameter having the most effect was the cutting speed, with an ratio of 56.811%, while for surface roughness it was the feed rate, with 95.827%.

EFFECTS OF DIFFERENT CRYOGENIC TREATMENTS ON DRILLING PERFORMANCE OF HSS DRILLS

Cryogenic processing is a heat treatment which has been widely used in recent years to improve the properties of tool materials. This process has been reported in the literature as it provides significant contributions to wear resistance and tool life of tool steels. This study presents the differences in tool performance between untreated and cryogenically treated M2 high speed steel (HSS) drill bits in terms of their tool wear, tool life, hardness and chip formation properties. Also, the effects of two different tempering temperatures (200 oC and 250 oC) in cryogenic treatment on tool performance are discussed. Drilling performances were studied on different workpieces of SAE 1050, lamellar cast iron and sphero cast iron, and the type of wear is characterized by a high resolution camera. Moreover, fracture tests were performed on a steel workpiece using a constant drilling speed of 1100 m/min and a feed rate of 0.5mm/rev. The microstructures of the samples were characterized using optical microscopy and SEM. The Vickers micro-hardness tests of the samples were performed using 100 g load. Microstructural studies showed that cryogenically treated samples exhibit better microstructure with finer and more homogeneous carbides which yields better tool wear and hardness properties. In paralel, cryogenically treated drills showed improved tool life than untreated drills during fracture tests. When tempering temperatures are compared, tempering at 250 °C resulted in better performance than 200 °C of tempering temperature. Also, the reduction in diameter values during drilling tests were consistent with the tool life tests.