Width Of Flank Wear Land Research Articles

Reducing the cutting tool wear in diamond turning of Zerodur glass-ceramic by the mechanical cleaning effect of ultrasonic vibration assistance

The effects and mechanisms of using ultrasonic vibration assistance (U.V.-assisted machining) combined with straight-nosed cutting tools on reducing the cutting tool wear in single-point diamond turning (SPDT) of Zerodur glass-ceramic are analysed and experimentally investigated. Aiming at the predominant abrasive wear in machining hard and brittle materials, analyses have shown that applying appropriate ultrasonic vibration to the cutting tool can induce considerable inertial acceleration to the wear particles residing on the tool-work interface for promoting their ejection from the contact area to reduce the abrasion. Meanwhile, the high thermal conductivity of diamond can prevent the possible excessive temperature elevation of the cutting tool surface that may result from the in-plane vibration components. To verify these, a longitudinal ultrasonic vibrator that works together with the Poisson's effect was designed for the SPDT processes with straight-nosed cutting tools. Machining tests on Zerodur optics have shown that the assistant ultrasonic vibration is able to decrease the tool flank wearland width by about 30 %, and the groove-like scratches on the tool flank wearland surface were reduced, which is consistent with the analytical deductions. Besides, no significant traces of structural change, element diffusion, and oxidation were found on the worn cutting tool surfaces under either the assisted or unassisted cutting conditions. The experiments have also shown that the enhanced durability of cutting tools has extended the cutting tool life for maintaining good machined surface quality, which is particularly beneficial to the ultra-precision machining of large-size optical parts.

Oxidation and wear behavior of CrAlMoN with varied Mo-content for cutting Ti6Al4V

The cutting of difficult to machine materials such as titanium alloys is challenging for the machining industry. In case of the titanium alloy Ti6Al4V, the properties of the material cause high temperatures, mechanical loads as well as high frequency vibrations at the cutting edge, leading to premature tool failure. The use of uncoated carbide tools is very common for machining of Ti based alloys. However, temperature active, self-lubricating physical vapor deposition (PVD) coatings like CrAlMoN showed promising results to reduce friction and wear during turning of Ti6Al4V. In the present study, self-lubricating (Cr34Al41Mo25)N, (Cr29Al36Mo35)N and (Cr25Al31Mo44)N coatings were investigated on cemented carbide tools. These were deposited by a hybrid process combining direct current Magnetron Sputtering and High Power Pulsed Magnetron Sputtering. Coating morphology, thickness, chemical composition, indentation hardness and modulus at ϑ = 20 °C, ϑ = 200 °C, ϑ = 400 °C and ϑ = 600 °C as well as the oxidation behavior were analyzed. Moreover, wear development after cutting tests using a CNC-lathe was investigated. Independent of Mo-content, all coating variants possessed a dense morphology and a smooth surface topography, as well as a coating adhesion class of HF1 to the cemented carbide substrate in Rockwell indentation tests according to DIN 4856. With an increasing amount of Mo, heat treatment temperature and time, more self-lubricating molybdenum oxides such as MoO3 and Mo4O11 were detected by Raman spectroscopy. Therefore, the coating with the highest amount of Mo possessed the highest amount of molybdenum oxides. After cutting tests, molybdenum oxides were also found on the tool flank face by Raman spectroscopy. The level of flank wear land width decreased with increasing amount of Mo.

Built-up edge formation and flank wear evolution in conventional machining of AZ91 magnesium alloy

Magnesium alloys are largely desirable in numerous industries today because of their intrinsically attractive properties. Low density and high strength coupled with significant biocompatibility are the main advantages. Machining of magnesium alloys is challenging as a result of the persistent chip ignition risk as well as material build-up on the tool due to their softness. Therefore, magnesium alloys’ machinability has not been fully assessed in the available literature. The present work aims to address this aperture by assessing flank wear progression and the prevalence of adhesion-driven built-up edge (BUE) and built-up layer (BUL) in different tool coating materials during the dry short-interval conventional orthogonal turning of AZ91 magnesium alloy. A higher and lower combination of feed rates and cutting speeds were utilized for all tools to compare the possible range of maximum flank wear land width, average flank wear land width, and chip contact length while capturing and assessing said parameters through digital and optical microscopy. The data presented a large prevalence of adhesion wear across all tool coating types which is portrayed by the cyclic behaviour of the flank wear land width plots, which resulted from the repeated accumulation and wear of deposited workpiece material. The TiCN-coated tool presented the least amounts of BUL and BUE throughout both levels of testing, while the TiN-coated tool presented the largest amounts of average flank wear land width due to recurrent aberrative local deposition accumulation and extended streak line depositions. TiN-coated, Al2O3-coated, and uncoated tools presented higher average flank wear land width than the TiCN-coated tool by 8.5%, 3.1%, and 27.2% during level 1 cutting conditions and 84.8%, 21.3%, and 37.2% during level 2 cutting conditions. This implies the TiCN coating's increased resistance to elevated cutting temperatures, and in turn, reduced deposition of material through adhesion.

Simulation-based design of flank face modification for the milling of Ti-6Al-4V and Inconel 718

The milling of titanium and nickel-based alloys leads to high tool wear due to the high thermomechanical load on the tool. By modifying the flank face on end mills, it is possible to limit the increase in the width of flank wear land, thus increasing tool life, component quality and increasing the allowable productivity of the tools. The flank face modification is characterized by the width and depth of the undercut and the rounding in the undercut of the modification. Through a simulation-based approach, a method is created to design the flank face modification in a load-optimized way and thus to use the full potential in the respective application cases.

Tool Wear and Milling Characteristics for Hybrid Additive Manufacturing Combining Laser Powder Bed Fusion and In Situ High-Speed Milling.

We report on milling and tool wear characteristics of hybrid additive manufacturing comprising laser powder bed fusion and in situ high-speed milling, a particular process in which the cutter mills inside the powder bed without any cooling lubricant being applicable. Flank wear is found to be the dominant wear characteristic with its temporal evolution over utilization period revealing the typical s-shaped dependence. The flank wear land width is measured by microscopy and correlated to the achievable surface roughness of milled 3D-printed parts, showing that for flank wear levels up to 100 m a superior surface roughness below 3 m is accessible for hybrid additive manufacturing. Further, based on this correlation recommended tool, life scenarios can be deduced. In addition, by optimizing the finishing tool start position and the number of afore-built layers, the milling process is improved with respect to the maximum millable angle for undercut surfaces of 3D-printed parts to 30° for the roughing process and to 40° for the entire machining process including finishing.

In-process monitoring and empirical modeling of the tool wear in turning of aluminum alloys using thermoelectric signals

Tool wear is an important criterion for economic machining. It does not only determine the tool life, but also affects the surface layer properties of metallic components and thus their performance. In addition to the machining parameters, there are numerous other influencing factors like batch variations, workpiece inhomogeneities, process vibrations, or the formation of built-up edges that can impact the wear progression. Consequently, it is difficult to predict the tool wear analytically. Therefore, the determination of the tool condition during machining is of great importance. The tool-workpiece thermocouple enables the in-process measurement of a thermoelectric voltage and current during machining generated by the Seebeck effect at the interface between two electrically conductive materials. Thus, the thermoelectric signals are sensitive for the changing contact interface between the tool and the specimen. To allow for an in-process characterization of the tool wear, finding an empirical relationship between the flank wear land width of cemented carbide indexable inserts and the thermoelectric signals in turning is aspired. To vary the flank wear land width in a reproducible manner, tools with a flank face chamfer resulting in a clearance angle of 0° and five different flank face land widths (80 µm – 280 µm) are used. These geometrical properties are measured with a 3D laser scanning microscope. Afterwards, cylindrical specimens of the aluminum alloy EN AW-2017 are machined by turning applying the modified tools and cutting speeds in the range of 300 m/min to 550 m/min. The depth of cut (0.4 mm) and the feed (0.04 mm) are kept constant. Besides the tool-workpiece thermocouple, the components of the resultant force are measured by a dynamometer. The geometrical properties of the machined surfaces are characterized using a stylus measurement instrument.The experimental investigations show an increase of the temperature and the components of the resultant forces with increasing flank wear land width, which impacts the geometrical properties of the surface. An empirical regression model derived from the in-process measurement results depicts the relationship between the thermoelectric signals, the force components, and the changing area of the tool which is in contact with the specimen. Consequently, the combined in-process measurement of the process forces and thermoelectric signals allows for an in-process determination of the tool wear progression and therefore enables the prevention of a strong impairment of the surface-layer properties by a timely tool change or a controlled adjustment of the machining parameters.

Fundamental investigations on wear evolution of machining Inconel 718

Nickel-based superalloys are often used in aerospace industry for different applications, e.g., blisks or turbine blades. Due to its high strength and corrosion resistance, materials like Inconel 718 lead to a poor machinability and, thus, to a high amount of tool wear. In this paper, the influence of different process parameter values on the tool wear is analyzed. For the fundamental investigations, the tool wear evolution was examined for two different path strategies with and without coolant. To identify suitable process parameter values, the width of flank wear land and process forces were analyzed based on a screening design of experiments.

Development of thin-film based sensors for temperature and tool wear monitoring during machining

Abstract The development of thin-film sensors for temperature and wear measurement in machining operations is presented in this work. A functional thin-film system, consisting of an Al2O3 insulation layer, a chromium sensor layer structured by photolithography and an Al2O3 wear-protection and insulation layer, is deposited by physical vapor deposition (PVD) processes onto the surface of cemented carbide cutting inserts. First specimen of the sensors are successfully fabricated and tested in laboratory experiments as well as in machining operations to demonstrate their functionality. These tool-integrated sensors can be used as an in-process monitoring device to determine the temperatures on the rake face at or close to the tool-chip contact area and to measure the progress of the flank-wear land width. The knowledge of these important process parameters opens up the possibility to develop new in-process control mechanisms in order to modify and improve the surface integrity of manufactured components. Thereby, their performance and lifetime can be enhanced.

Analytical modelling and experimental validation of micro-ball-end milling forces with progressive tool flank wear

In this paper, an analytical model for estimating the micro-ball-end milling forces is presented based on experimental investigation of progressive tool flank wear. The wear form and wear mechanism of the micro-ball-end mill are revealed through a series of micro-ball-end milling experiments. The effecting laws of cutting parameters such as feed per tooth, cutting speed, and inclined angle on tool flank wear are investigated. The experimental results indicate that the progressive tool flank wear has significant influence on cutting force in micro-milling of NAK80 steel. To assure the prediction accuracy of micro-ball-end milling force, an analytical methodology is presented to estimate cutting forces which considers not only the shearing force resulted from chip formation but also ploughing and rubbing force resulted by combined elastic contact and plastic flow at enlarged flank wear land. To verify the validity of the developed analytical model, a series of experiments are carried out on high-precision machine by using micro-ball-end mill with different flank wear lands. The comparisons of theoretical and experimental cutting forces indicate that the developed model can provide acceptable predicted accuracy. The proposed analytical cutting force model could be employed to monitor progressive tool flank wear land width in micro-ball-end milling of complex surface in future work.

A comprehensive study on flank wear progression of polycrystalline diamond micro-tool during micro end-milling of SiCp/Al composites

SiCp/Al composites are extremely difficult to process due to the existence of reinforced particles and the associated severe tool wear. The conducted experiments indicate that abrasive and adhesive wear are main flank wear types of PCD micro-tools in micro slotting end-milling of 45vol% SiCp/2024Al composites. Then, an analytical methodology incorporating two-body/three-body abrasive wear and adhesive wear is presented to estimate the PCD micro-tool flank wear land width in micro end-milling of SiCp/Al composites. The results show that adhesive wear is dominant at the initial machining stage, and two-body abrasive wear becomes the main tool flank wear mechanism at the later machining stage which takes about 60% of the tool flank wear under the given machining conditions. Besides, the effects of reinforced particles and machining/tool parameters on the tool flank wear progressions are analyzed.

Simulation-based feed rate adaptation considering tool wear condition

The process forces generated in machining are related to a deflection of the milling tool, which results in shape deviations. In addition to process parameters like feed rate, width and depth of cut or cutting speed, the wear condition of the tool has a significant influence on the shape deviation during flank milling. In process planning it is important to take the tool condition and the ideal time for tool change into account when selecting the process parameters. An assistance system is being researched at the Institute of Production Engineering and Machine Tools (IFW) in cooperation with Kennametal Shared Services GmbH to support this task. The assistance system adjusts automatically the feed rate considering a predefined maximum shape deviation. Additionally, it identifies an optimal moment for tool change. The advantages of the system are particularly evident in planning of individual milling processes. The assistance system is based on a combination of a material removal simulation and empirical models of the shape error. For this purpose, spindle currents as well as measured shape errors are stored in a database. These data are extended by the actual local cutting conditions calculated by a process-parallel material removal simulation. Afterwards, the data is transferred into process knowledge via a Support Vector Machine (SVM). Within a technological NC simulation before the start of manufacturing, the generated knowledge is applied to predict the shape error of the workpiece and to automatically adjust the feed rate. By adapting the feed rate, it is possible to control the tool life. The required tool change is defined by specifying a limit for the permitted width of flank wear land. The presented assistance system enables the prediction of the shape error parallel to the manufacturing process and the automatic determination of the feed rate as well as the ideal time for tool change.

A New Flank Face Design Leading to an Improved Process Performance when Drilling High-Temperature Nickel-Base Alloys

In previous investigations, the concept of a modified flank face design with a retraction behind the cutting edge was developed. Based on fundamental investigations regarding the mechanical and thermal loads, combined with simulation-based analyses, a new design of the flank face has been created with the largest possible free volume behind the cutting edge while maintaining the mechanical stability required for the challenging machining of nickel-base alloys. This flank face modification allows a greater amount of cutting fluid to flow along the back of the cutting edge at higher velocities while at the same time creating the potential of a friction reduction between the tool tip and bore hole ground. The described concept was implemented on solid carbide twist drills which were then used to machine Inconel 718. The results show that, while tools equipped with a flank face retraction perform up to four times longer compared to standard tools, they tend to reach the end of tool life rather suddenly due to cutting edge chipping. This typically occurred when the maximum width of flank wear land equalled the width of the remaining cutting edge. Since then, further investigations have been carried out in order to refine the concept of the flank face modification. A new design was implemented with regard to a more effective cooling of the flank face, presumably caused by an improved cutting fluid flow velocity particularly at the cutting edge corners. Simulation-based findings, combined with experimental tests of the new prototypes, could reveal that the improved cutting fluid flow in the area of the cutting edges leads to significantly extended tool life and machining performance when drilling Inconel 718.

Semi-analytic modelling of cutting forces in micro ball-end milling of NAK80 steel with wear-varying cutting edge and associated nonlinear process characteristics

Cutting edge of miniature ball-end mill is one of decisive importance for the machining performance by affecting the thermal and mechanical load in cutting process. In this paper, a semi-analytic model is proposed to estimate the cutting forces in micro ball-end milling of NAK80 steel considering wear-varying cutting edge and the associated nonlinear process characteristics. The wear-varying cutting edge geometry under the different wear stage is obtained by 3D optical profilometer. The measured results indicate that cutting edge of miniature ball-end mill under the different wear stage includes not only the enlarged cutting edge radius but also the extended flank wear land, which can be described by a combination of edge radius and flank wear land width. The influence laws of the edge radius and flank wear land width on tangential and feed force coefficients are investigated, and the enlarged edge radius and extended flank wear land under different wear stage could be separated from each other by utilizing the cutting force coefficients data based on their different sensitivity on cutting forces. A semi-analytic method is developed to predict the shearing/plowing/friction forces in primary and tertiary shear zones based on classical oblique cutting and slip-line field model. The nonlinear tool-chip friction behavior with the phenomenon that the ratio of tool-chip contact length to uncut chip thickness and friction factor nonlinearly change with the ratio of uncut chip thickness to edge radius are investigated and employed to estimate rake/shear/friction angles, and the nonlinear strain gradient plasticity effect with the fact that effective strain gradient is affected by not only rake angle and shear angle, but also primary shear zone thickness that obviously increases with reduce of the ratio of uncut chip thickness to edge radius are considered to estimate the shear flow stress. The nonlinear behavior derived from the tool-chip/workpiece friction and material constitutive affects the contribution level of size effect on cutting forces in micro ball-end milling. Finally, to calibrate and validate the effectiveness of the proposed cutting forces model, a set of micro ball-end milling of NAK80 steel experiments are performed on a three axis ultra-precision machine by using same solid carbide tool with wear-varying cutting edge under different wear stage. The comparisons between the predicted and measured results show that the proposed model can provide higher accuracy and better understanding for micro ball-end milling of NAK80 steel.

Analytical Model of Progression of Flank Wear Land Width in Drilling

In multipoint operations like drilling, cutting velocities and cutting-edge geometries vary along cutting lips so is the rate of progression of flank wear. Analytical evaluation of flank wear land width in the case of complex tools has received a limited attention so far. This work evaluates progression of flank wear in orthogonal machining and adopts it to drilling. An abrasive flank wear has been modeled, wherein, cutting speed determines the rate of abrasion, and the feed rate determines the chip load. The model considers stress distribution along rake surfaces, and temperature-dependent properties of tool and work materials. Assuming that the flank wear follows a typical wear progression as in a pin-on-disk test, the model evaluates cutting forces and the consequent abrasive wear rate for an orthogonal cutting. To adopt it to drilling, variation in cutting velocity and dynamic variation in rake, shear, and friction angles along the length of the cutting lips have been considered. Knowing the wear rate, the length of the worn-out flank (vb) has been evaluated. The model captures progression of flank wear in zones (i), (ii), and (iii) of a typical tool-life plot. It marginally underestimates the wear in the rapid wear region and marginally overestimates it in the steady-state region.

Dynamika zużycia płytek skrawających podczas toczenia niejednorodnego materiału na przykładzie polimerobetonu

The article presents the results of studies on the dynamics of wear of five different cutting inserts (for machining difficult-to-cut materials, for finishing cast iron machining, for roughing cast iron machining, for steel machining and for stainless steel machining) during turning a non-homogeneous material such as polymer concrete. Polymer concrete is a difficult-to-cut, anisotropic, composite material. During the tests, a record of the components of the cutting force in real time was made. After each machining pass, the Ra and Rz surface roughness values were measured in the direction perpendicular to the machining marks and photos were taken under the microscope of the inserts corners, on the basis of which the width of major flank wear land and the width of minor flank wear land were measured. The view of each insert after the tests was also presented. Finally, the conclusions about the dynamics of wear of inserts taking part in the study as well as their applicability during polymer concrete turning were formulated.

Relation between tool wear and workpiece modal vibration in ultra-precision raster fly cutting

Tool wear is a key factor affecting machined surface quality; numerous methods have been adopted to reflect tool wear features online. In the present research, workpiece modal frequencies were employed to present tool wear level in ultra-precision raster fly cutting (UPRFC) process. In time domain, cutting force composition and the relation between cutting force amplitude and tool wear level were explored. In frequency domain, the relation between workpiece modal frequencies as a response of cutting force stimulus and tool wear level was investigated. Theoretical and experimental results reveal that the peak power spectrum density (PSD) values of the workpiece modal vibration (especially the first order workpiece modal vibration) grow with the progress of tool wear, the width of flank wear land and the first order workpiece modal vibration has a linear relationship, which could be used to predict tool wear in UPRFC and even other intermittent cutting process.

Precision cutting of single crystal silicon using CBN tool with large top corner radius

A lot of studies on the ultra-precision cutting of single crystal silicon have been reported and they used the diamond cutting tools. However, the diamond cutting tools are very expensive. Therefore, if the single crystal diamond tools were replaced with sintered CBN tools, the cost of machining could be fairly reduced. However, it is easily expected that the CBN tools wear out faster than the diamond tools. Therefore, it is very important to find out the optimum cutting conditions in order to reduce tool wear. In this study, precision cutting of single crystal silicon was machined with using CBN cutting tools having chamfer at cutting edge and large nose radius, and the effect of feed rate, cutting speed, depth of cut and nose radius on the tool wear were studied. As a result, the local minimum of width of flank wear land appeared at the feed rate of 30~50 µm/rev.

Precision cutting of single crystal silicon using CBN tool with large top corner radius

A lot of studies on the ultra-precision cutting of single crystal silicon have been reported and they used the diamond cutting tools. However, the diamond cutting tools are very expensive. Therefore, if the single crystal diamond tools were replaced with sintered CBN tools, the cost of machining could be fairly reduced. However, it is easily expected that the CBN tools wear out faster than the diamond tools. Therefore, it is very important to find out the optimum cutting conditions in order to reduce tool wear. In this study, precision cutting of single crystal silicon was machined with using CBN cutting tools having chamfer at cutting edge and large nose radius, and the effect of feed rate, cutting speed, depth of cut and nose radius on the tool wear were studied. As a result, the local minimum of width of flank wear land appeared at the feed rate of 30~50 µm/rev.

An investigation into the behavior of the cutting forces in precision turning

A mechanistic model of precision turning, in which the depth of the cut is made considerably smaller than the tool nose radius, based on Merchant’s analysis in 3D cutting, has been developed. Reasons were deduced to the increase of the radial force component to be greater than the tangential component. The friction coefficient at the tool chip interface during precision turning has been calculated. The developed model was verified experimentally using both annealed and hardened HSS. Moreover, due to the obsoleteness of empirical formulae established by previous investigators in the case of precision turning, new empirical formulae based on the mechanistic model are presented. In this machining operation, the behavior of the cutting forces in relation to the cutting variables, revealed their high sensitivity to tool nose radius and flank wear land width.

Evaluation for tool flank wear and its influences on surface roughness in ultra-precision raster fly cutting

The occurrence of tool flank wear certainly affects the machined surface roughness in ultra-precision machining. The in-process evaluation of tool flank wear and its effects on machined surface roughness is significant, since it helps to find tool flank wear timely and reduce tool wear effect on surface roughness by further actions. However, little attention has been paid to the evaluation of tool flank wear and its effects on machined surface roughness in ultra-precision raster fly-cutting (UPRFC) process especially by using cutting chips. In the present research, evaluation of tool flank wear and its effects on surface roughness is conducted in UPRFC by examination of cutting chip morphologies. Based on the relations between chip morphologies and tool flank wear, a mathematical model was established to identify the width of flank wear land and the theoretical surface roughness under tool flank wear effects. Theoretical and experimental results show that: (1) Tool flank wear occurrence causes the formation of shutter-like structure rather than feather-like structure at the tool entry of cutting chips. (2) Cutting chips are truncated where chip thickness is comparable to the width of wear land. (3) The smooth tool flank wear increase the tool nose radius and therefore reduce the surface toughness theoretically.