Extend Tool Life Research Articles

Tool wear in ultrasonic vibration–assisted drilling of CFRP: a comparison with conventional drilling

Carbon fiber reinforced polymers (CFRPs) are becoming increasingly prevalent in the industries including automobile, aerospace, and military due to their light quality, high specific strength, high corrosion resistance, excellent thermodynamics performance, etc. However, these excellent properties easily result in intensive tool wear, short tool life, and reduced machining accuracy. Although ultrasonic vibration–assisted drilling (UVAD) was considered an effective drilling method to reduce tool wear, most reported studies focused on machining kinematics or mechanics, and very few studies systematically explored the tool wear behaviors in UVAD of CFRP. To fill this gap, this paper aims to investigate tool wear of high-speed steel (HSS) twist drill in UVAD of CFRP and compares these wear behaviors with those in conventional drilling based on the experimental observation of the worn drill morphologies. The effects of cutting parameters on tool wear were discussed with the special focus on the differences in tool wear between conventional drilling (CD) and UVAD. The observed wear behaviors can include abrasion, adhesion, oxidization, or the combination of them. The introduction of UVAD can effectively reduce the average width of tool flank wear with a maximum reduction of 13.0% when compared with CD. Both increased feed rate and decreased spindle speed can lead to decreased tool wear. The findings in this paper might offer guidance on the selection of cutting parameters for extending tool life in UVAD of CFRP.

Investigation on the tool worn surface morphology and machining characteristics of the Hardox steel using minimum quantity lubrication

Abstract In recent years, minimum quantity lubrication machining has played a critical role in extending tool life, improving surface finish, and reducing tool wear during the machining of hardened steel. The reported investigation involved the utility of Hardox 500 steel for the machining process while the cubic boron nitride coated tool performed the function of removing the material. The investigation was carried out by adopting two different techniques to predict the responses, viz., the response surface methodology and the artificial neural network. These techniques have been employed to predict the possible responses in investigating machining characteristics. Also, due consideration has been made concerning the reduction of tool-tip temperature and surface roughness. The entire investigation was carried out using three different environments. They are dry machining, wet, and minimum quantity lubrication. A scanning electron microscope was used for examining the morphology of the worn tool surface.

Empirical study on ultrasonic assisted turn-milling

Turn-milling process has been paid attention in order to be used in multi-task machining processes. Moreover, looking for new machining techniques aimed at reducing cutting force is of important. Reducing cutting force in machining processes has the benefits of extending tool life and improving surface quality. One of the new concepts for reducing the cutting force is applying ultrasonic vibration. In this paper, effects of ultrasonic vibration under different machining parameters in turn-milling process of Al-7075 alloy will be investigated. In this order, a special mechanism was designed to apply ultrasonic vibration during machining process. Ultrasonic vibration exertion on the tool reduced cutting force and surface roughness up to 75% and 35%, respectively. Also tool rotational speed increment induced cutting force and surface roughness increment. In addition, tool feed rate and workpiece rotational speed increment caused cutting force and surface roughness increment. Although, feed rate was more influential.

Energy, Environmental, Economic, and Technological Analysis of Al-GnP Nanofluid- and Cryogenic LN2-Assisted Sustainable Machining of Ti-6Al-4V Alloy

The quest for advanced cooling/lubrication approaches for energy-efficient, eco-benign, and cost-effective sustainable machining processes is garnering attention in academia and industry. Electrical and embodied energy consumption plays an important role in reducing CO2 emissions. In the present study, new empirical models are proposed to assess sustainable indicators. The embodied energy, environmental burden, and cost of coolant/lubricant have been added in the proposed models. Initially, optimal levels of minimum quantity lubrication (MQL) oil flow rate, liquid LN2 flow rate, air pressure, and nanoparticle concentration were found. Based on optimal technological parameters, experiments were performed under the same cutting conditions (machining parameters) for MQL and cryogenic LN2-assisted external turning of Ti6-Al-4V titanium alloy. The electric power and energy consumption, production time/cost, and CO2 emissions were assessed for a unit cutting-tool life. Later, specific responses were measured and compared between both cooling and lubrication approaches. Results showed that hybrid Al-GnP nanofluid consumed 80.6% less specific cumulative energy and emitted 88.7% less total CO2 emissions. However, cryogenic LN2 extended tool life by nearly 70% and incurred 4.12% less specific costs with 11.1% better surface quality. In summary, after Energy–Economy–Ecology–Engineering technology (4E)-based analysis, cryogenic LN2 is sustainable economically but not environmentally and there is a need to improve the sustainable production of LN2 at an industrial scale to achieve environmental sustainability. The present study provides useful information to establish clean machining processes.

Performance increase by process parameter variation during turning of AISI 4140

Usually, constant process parameters are used for turning. These process parameters result in a thermomechanical load of the tool, which leads to a specific wear pattern. Varying the process parameters along the toolpath, e.g. linear or sinusoidal, can extend tool life by distributing wear over a wider area and reducing the thermal tool load. In this paper, a method for designing process parameter variations during turning is presented. It is shown that tool wear can be reduced using process parameter variation. This reduction in wear is due to a decrease in thermal tool load. In addition, a method for designing processes with modulated process parameters is being developed.

Assessment of decision-making algorithms for adaptive drilling of aerospace stacks

When drilling multi-material aerospace stacks, adaptive drilling can allow for parameter optimisation for each individual layer of the workpiece, resulting in improved borehole quality and extended tool life. This work investigates the effectiveness of different decision-making strategies in determining the occurrence of process incidences when drilling CFRP/Aluminium stacks. Cutting force signals acquired at different tool wear stages with different machining equipment were fed to three decision-making algorithms, allowing for an assessment on their responsiveness and reliability in detecting the occurrence of three process incidences: tool engagement, material transition and tool disengagement.

High-speed milling Inconel 718 using Electrostatic Minimum Quantity Lubrication (EMQL)

Inconel 718 superalloy is widely used in the aerospace and nuclear industries. It is a difficult-to-cut material representing short tool life and high machining costs. Minimum Quantity Lubrication (MQL) is adopted to extend tool life and minimize machining costs. However, it is not effective in high-speed milling processes. A new Electrostatic Minimum Quantity Lubrication (EMQL) nozzle design is presented. The performance of the EMQL system in end milling Inconel 718 is assessed in terms of tool life, specific cutting energy and, surface roughness; and is benchmarked against MQL.

Sustainable milling of Ti–6Al–4V: A trade-off between energy efficiency, carbon emissions and machining characteristics under MQL and cryogenic environment

The urgent need for an innocuous and sustainable machining system is essential in this modern manufacturing era. Therefore, a study is devoted to fulfilling a missing bridge between sustainability measures (process time, specific cutting energy, energy efficiency, carbon emissions) and machining characteristics (tool wear, surface roughness, cutting temperature) in the milling of Ti–6Al–4V. The experiments are organized by implementing the minimum quantity lubrication (MQL), CO2-snow, and cryogenic-LN2 under varying end-mill geometries and cutting conditions. The results obtained have underscored the outperformed CO2-snow followed by cryogenic-LN2, MQL, and dry cutting conditions regarding sustainability measures and machining characteristics. The up-milling of 42° helix angle cutter and CO2-snow outperformed by reducing 47% of surface roughness, 50% extended tool life compared to dry cutting. The cryogenic-LN2 provided minimum cutting temperature flowed by CO2-snow, MQL, and dry cutting, respectively. Besides, the up-milling tool of the 42° helix angle provided better machining characteristics than the down-milling tool of the 30° helix angle. The feasibility of CO2-snow was comprehensively expressed and implemented in the milling process to extend the advanced analysis.

Machinability maps – Towards a mechanistic understanding of the machining of TI-6AL-4V and TIMETAL 407

In recent years, new titanium alloys with improved “machinability” have been developed, to provide manufacturers with alloys that can be machined to final dimensions at higher metal removal rates. One such alloy, TIMETAL® 407 (Ti-407), was developed to replace Ti-6Al-4V (Ti-64) in applications where energy absorption prior to failure is a key property requirement. In this study, a combination of large scale turning trials was used to characterise the full range of machining criteria, including: (1) tool life, (2) chip formation and (3) subsurface microstructural deformation. The machining response of the two alloys was summarised in easy-to-visualise machinability maps: to aid the machining supply chain in selecting feed rates and cutting speeds to generate certain chip forms, to extend tool life and minimise subsurface deformation for specific titanium alloys. Assessment of these key characteristics has provided an understanding of the effects of mechanical twinning on the poor chip control through increasing the accommodation of strain prior to fracture.

Experimental and computational investigations on the effects of deep-temperature emulsion on the turning of Inconel 718 alloy

Nickel-based superalloys, for instance Inconel 718, are applied in extreme conditions due to their excellent high-temperature strength. However, the same thermomechanical properties make the machining of Inconel 718 a challenge. Cutting fluids play a vital role in extending tool life as well as preserving surface integrity. Nevertheless, their effectiveness is naturally restricted by the fluid’s heat capacity. In order to improve cooling effectiveness, a new approach has been developed that combines high-pressure fluid supply and high cooling performance through the use of a deep temperature emulsion (DTE). Experimental and computational investigations were carried out on the high-speed turning of Inconel 718. Cutting forces, tool wear, chip formation and surface integrity were monitored. The experiments revealed that the addition of monoethylene glycol (MEG) reduces a cutting fluid’s freezing temperature but negatively affects the machining performance. However, the observed deficiencies are compensated by the benefits of cooling the cutting fluid. The cutting fluid at a temperature of T=−10°C leads to comparable results to those of the reference process and even to further improvements in process performance. Therefore, the application of DTE could potentially outperform and ultimately replace conventional cooling strategies.

Real-time tool wear monitoring using thin-film thermocouple

Due to harsh environment in the cutting area, access to the cutting region is still limited for the existing temperature sensors. As such, measuring temperature signals remains a challenge for real-time tool wear monitoring. In this paper, a polycrystalline cubic boron nitride (PCBN) cutting tool embedded with thin-film thermocouple (TFTC) was devised and used for tool wear monitoring during the cutting of hardened AISI O2 tool steel. A detailed manufacturing process of the smart tool was introduced. Performance tests for the smart insert were evaluated and results showed that the embedded TFTC had a sensitivity of 14.4 μV/℃, good dynamic response, and functional validity. Wear experiments were implemented under two sets of cutting parameters to explore the relationship between cutting temperature and tool wear. The results showed that the increased maximum cutting temperature could well reflect the progression of flank wear. Obvious fluctuation in temperature signal could also well reflect the abnormal condition of the tool. The devised smart tool will be useful for determining optimum cutting parameters and extending tool life.

Initial tool wear behavior in high-speed turning of Inconel 718

Three distinctive regions of tool wear, known as initial wear, steady-state wear, and accelerated wear, are well understood. However, the effects of cutting parameters on the initial tool wear mechanism, morphology, and size have received less attention as compared to the other two regions. Knowing that adequate control of initial tool wear may lead to extended tool life, in particular in hard-to-cut metals such as superalloys, this topic has become a source of attention. Amongst superalloys, Inconel 718 is considered as one of the most difficult to cut materials, which has a wide range of industrial applications. This study intends to evaluate the effects of cutting parameters on initial tool wear, as well as tool wear progression, when turning Inconel 718. Therefore, microstructural evaluation of the initial tool wear mode under various cutting conditions, as well as tool wear measurements, were conducted. It was observed that certain elements of the workpieces were migrated to the insert flank face. This is evidence of adhesion at the initial moments of the cutting process. In contrast to many other easy-to-cut materials, the steady-state wear period when turning Inconel 718 is significantly short under a higher level of cutting speed and feed rate.

Outside Help Delivers

Two companies have changed their coolants, bringing in outside help to investigate and manage the change. Both have discovered a single product that has the versatility to cope with a broad range of processes and materials, while delivering consumable cost reductions and extended tool life

Enhanced carbide tool life by the electromagnetic coupling field for sustainable manufacturing

The effective extension of tool life while maintaining machining quality is an important research topic in advanced machining and sustainable manufacturing. Cemented carbide is widely used as the tool material in different manufacturing processes, and it has various forms and work ranges. However, the internal flaw in the tool material can induce a micro-crack which could result in the decrease of tool strength and toughness, and affect the tool life. Improving the tool cutting performance, slowing down the tool wear, and enhancing production efficiency are the eternal themes of cutting tool research. This research focused on a P10 cemented carbide tool. The influences of the electromagnetic coupling field (TEMCP) on the carbide tool life and the maximum of tool force are investigated. The correlation analysis between the TEMCP parameters and the tool life index is conducted using SPSS. The experiment proves that the TEMCP can significantly prolong the cemented carbide tool life, and that the magnetic intensity is a dominant factor. The TEMCP enriches the field technology theory and provides technical support for the sustainable manufacturing and research and development of a high-performance tool with important scientific meaning and research potential.

Enhanced wear performance of laser machined tools in dry turning of hardened steels

Polycrystalline boron nitride cutting tools are currently used for precision machining of automotive components made of hardened steel due to their high wear resistance and long durability, however adhesion of workpiece to the cutting tool can reduce cutting tool lifetime. Laser surface engineering of polycrystalline boron nitride single point cutting tools using a nanosecond fibre laser is proposed to improve their wear properties and extend tool life in turning of continuous hardened steel components. The effect of different designs on the wear properties was investigated in turning tests under dry conditions and compared to benchmark cutting tools made of the same material. Condition monitoring of machining forces revealed a 20% reduction of cutting force and 30% reduction of feed force for tools with crosshatch design and grooves perpendicular to chip flow direction, when benchmarked to commercial cutting tools. The number of grooves in contact with the forming chip contributed to the creation of three distinguished interfacial secondary deformation areas. Texturing the chamfer proved to alter the dynamic of chip formation in the secondary deformation zone, while engineering the formation of laser-induced solid lubricant h-BN improved the heat dissipation rate in the secondary and tertiary deformation areas.To the best of authors’ knowledge, this paper reports for the first time the possibility of simultaneously engineer geometry and chemistry of PcBN cutting tools so to enhance their service life by up to 20%.

Chemical–Mechanical Polishing of Cemented Carbide Insert Surface for Extended Tool Life in Turning of GH4169 Nickel-Based Superalloy

To extend the tool life of conventional uncoated grinding cemented carbide inserts (CUG inserts) in turning GH4169 nickel-based superalloy, chemical–mechanical polishing (CMP) is applied to appropriately treat the rake face of the CUG insert to address the defects including grinding burn, crack, and thermal deformation. The material removal rate (MRR) and the rake face roughness Ra of YG10 chemical–mechanical polished cemented carbide inserts (CMP inserts) corresponding to the six types of abrasives particles are investigated by applying the single factor method, and the diamond powder is the most suitable to polish YG10 inserts. Thus, CMP parameters are optimized using Taguchi method coupled with both the grey relation analysis and fuzzy inference. Furthermore, the comparison experiments of the cutting performance of the CUG insert and the CMP insert in turning GH4169 are carried out, under the same cutting condition, compared with the CUG insert, the average tool life of the CMP insert is increased by 35.92%. This study demonstrates that the CMP technique is an effective potential method to improve the surface integrity, the cutting performance and the tool life of conventional uncoated grinding cemented carbide inserts & tools in the machining of difficult-to-cut materials.

Friction modeling of tool-chip interface based on shear-slip theory for vibration assisted swing cutting

The vibration assisted swing cutting is a promising machining technology with characters of pseudo intermittent cutting and reverse friction. It can greatly extend tool life, reduce cutting forces and improve the surface accuracy of workpiece. In the cutting process, the tool-chip friction characteristics have a significant impact on the surface quality and machining accuracy of the work-piece. However, in the process of vibration-assisted swing cutting, the friction characteristics of tool-chip interface is not clear yet. In this paper, a new tool-chip friction model is proposed which takes into account the chip conversion layer is proposed based on shear slip theory. Moreover, the shear strain rate and chip particle velocity of the three friction regions of the tool-chip contact interface are described. the results show that the cutting speed increases from 75 m/min to 600 m/min, the cutting force decreases by 20 %, the thrust force decreases by 41 %, and the normal stress and shear stress decrease from 5.9 pa and 1.8 pa to 0, respectively. The increase of cutting speed leads to the increase of the temperature at the tip and the sticking at the tip. Comparing with the experimental results in existing references, the simulation results have good consistency and great prediction ability.

Evaluation of the effect of cryogenic treatment of HSS drills at different holding time in drilling AISI 316-SS

Cryogenic treatment has been acknowledged as an effective means of extending tool life of many cutting tool materials, thus improving productivity significantly. However, the real mechanisms which guarantee better tool performance have not been very clearly understood. This work aims to study the effect the effect of different holding time during cryogenic treatment on M2 high speed steel (HSS) drills. The performance of these cryo-treated tools were compared on the basis of thrust force, surface roughness, tool wear and chip formation by drilling on AISI 316 SS. The thrust force was least at 600 rpm and the rapid deep cryogenic treated (DCT) drills had much less thrust force (45%–55% lower) compared to untreated drills. From the various parameters involved it was observed that the cryo-treated tool bit at holding time of 24 h and at a cutting speed of 600 rpm and feed rate of 0.06 mm rev−1 showed better performance. The relative wear resistance of the cryo-treated drill at 24 h was at least two times better than the untreated drill while the surface roughness of the holes drilled with this drill was half that of those drilled with untreated drills. This investigation was further extended by gradual shallow cryogenic treatment (GSCT) and gradual deep cryogenic treatment (GDCT) of drills at the optimum holding time of 24 h. Both GSCT and GDCT treated drills showed 35% and 15% less thrust force respectively when compared to DCT. The better performance can be attributed to the lack of internal residual stresses. Microstructure SEM images and Rockwell hardness testing was done to support the findings.

Coolant boiling and cavitation wear – a new tool wear mechanism on WC tools in machining Alloy 718 with high-pressure coolant

In recent years, research interest in liquid coolant media applied to the tool–workpiece interface (the tertiary shear zone) has grown considerably. In particular, attention has increased for work where the media has been applied under high-pressure. This is most likely triggered by the positive results reported on similar applications, but with coolant media directed towards the rake face of the cutting tool (the secondary shear zone). The most typical applications have not surprisingly been related to the machining of Heat Resistant Super Alloys (HRSA) or other “difficult to machine” alloys where the main intention has been to extend tool life and improve surface finish through reduced shear zone temperatures.Concurrently, these achievements have revealed a knowledge gap and unlocked a new research area in understanding the effects and influences of coolant media applied on super-heated surfaces under high-pressure conditions. The aim of this study is to investigate the “coolant boiling and cavitation” phenomena that emerges during the application of coolant under high-pressure to the flank face of an uncoated WC tool while turning Alloy 718. The experimental campaign was conducted in three aspects: varying flank (coolant media) pressure; varying spiral cutting length (SCL); and varying cutting speed.The results revealed that the location and size of the coolant-boiling region correlated with flank wear, coolant pressure and vapour pressure of the coolant at the investigated pressure levels. Further, the results showed that coolant applied with a lower pressure than the vapour pressure of the coolant itself caused the “Leidenfrost” effect. This then acts as a coolant media barrier and effectively reduces the heat transport from the cutting zone.Further, erosion pits were observed on small areas of the cutting tool, resembling the typical signs of cavitation (usually found in much different applications such as pumps and propellers). The discovered wear mechanism denoted as “Cavitation Wear” was used as base for the discussion aimed to deepen the understanding of the conditions close to the sliding interface between the tool and the workpiece. Even though “Cavitation Wear” has been widely reported in hydraulic systems like pumps and water turbines, it is a new phenomenon to be seen on cutting tools while using high-pressure flank cooling.

Performance Assessment of Ni-Coated Titanium Alloys Under Wet Conditions

Since its first introduction in the 1950s, Ti6Al4V became the most sympathetic titanium alloy due to its attractive mechanical and physicochemical properties and is currently extensively used, for e.g., in machining, automotive, aerospace, as well as biomedical industry. However, its poor tribological properties limit its use in machining, automotive, aerospace, and orthopedic applications. Hence, a variety of attempts have been made in order to improve tribological performance of titanium alloys, especially focusing on surface modification. This paper represents an overview of significance of surface modification applied on Ti6Al4V alloy. Several solutions have been followed to improve the machinability of these alloys: development of new machining techniques, tool geometries, and protection of tools??? surface with coatings to yield high productivity, good surface finish of the work-piece, and extended tool life. In this work, Ni coating on Ti-based alloys is tested to evaluate their potential for machining as well as for biomedical applications. The tribological behavior is evaluated at room temperature in wet lubricated conditions on pin-on-disk equipment, by testing Ni-coated pins of 10 mm diameter and 30 mm long against EN-31 flat plate. Friction coefficient of coated pins in wet condition is observed to be less, as compared to the tests performed with uncoated pins. Coated sample tested in lubricated condition showed much more reduction in wear and friction coefficient than their performance under uncoated condition. From experimental investigation, it is observed that the Ti alloys with Ni coating show improved wear rate and friction coefficient as compared to without coating.