Chip Flow Direction Research Articles

Performance analysis of tools with rake face textures produced using wire-EDM in turning AISI4340

ABSTRACT Tool–chip interface friction significantly affects the machining characteristics like cutting forces, machining temperature, tool wear, and surface finish. Structuring the tool rake face using micro-textures is a recent method adopted to reduce tool–chip interface friction. The effect of varying the depth of these rake face micro-textures on the machinability of AISI4340 is studied. Textures of uniform width but with depth varying from 60 to 145 μm are created on the tool rake face using wire-EDM process perpendicular to the chip flow direction. The performance of these tools is compared with a non-textured tool in terms of cutting forces, cutting zone temperature, flank wear, chip trace area and surface finish. It is found that by optimizing the texture depth, it is possible to get improved performance from the cutting tool for the same machining conditions as compared to a non-textured tool. Further, it is found that for all the tools, the chip morphology changes during each pass from regular, closely curled helix at the beginning of the pass to randomly coiled chips at the end of the pass length with simultaneous increase in temperature.

Cutting Force in Milling of Additive Manufacturing AISI 420 Stainless Steel

In manufacturing, hybrid systems of metal additive manufacturing and cutting in the same platform have been attractive in terms of low volume production of customized parts, complex shape, and fine surface finish. Milling is conducted to finish rough surface fabricated in additive process. The fundamental machinability of the additive workpiece should be studied because the material properties are different from metals produced in the conventional process. The paper discusses the cutting forces in milling of AISI 420 stainless steel fabricated in additive process. The cutting tests were conducted to measure the cutting forces and the chip morphologies for tool geometries. The cutting forces were also analyzed in an energy-based force model. In the analysis model, three-dimensional chip flow is interpreted as a piling up of orthogonal cuttings in the planes containing the cutting velocities and the chip flow velocities, where the cutting model is made by the orthogonal cutting data acquired in cutting tests. The chip flow direction is determined to minimize the cutting energy. The cutting forces, then, were predicted in the determined chip flow model. The cutting force model was validated in comparison of simulated forces with the actual ones.

Development of a novel boring tool with anisotropic dynamic stiffness to avoid chatter vibration in cutting: Part 2: Analytical and experimental verification of the proposed method

In this study, we developed prototypes of boring tools with anisotropic dynamic stiffness, and their chatter stability was investigated analytically and experimentally. In Part 1, a novel design of boring tools with an anisotropic structure was proposed to improve the nominal stiffness in boring operation, thus resulting in higher chatter stability in simulation. In this part (Part 2), anisotropic boring tools with a holder length-to-diameter ratio (L/D) of 4 and 10 designed in Part 1 were prototyped, and their frequency response functions were evaluated. Then, the chatter stabilities were evaluated through turning experiments. With respect to a L/D4 boring tool with anisotropic structure, the nominal dynamic stiffness was significantly improved within the range of machining conditions that satisfies the appropriate combination of cutting force ratio and chip flow direction, compared to a conventional tool with isotropic structure. We confirmed that the proposed boring tool with an anisotropic structure increases the critical radial depth of cut by approximately 17 times compared with conventional tools. Even with an L/D10 anisotropic boring tool, a similar effect was observed wherein the dynamic stiffness of the tool was improved. In contrast, the effect of improving the dynamic stiffness was insufficient; thus, chatter free cutting could not be realized. Analytical investigations verified the importance of further improvement of dynamic characteristics. To realize stable boring with L/D10 boring tools, it is necessary to further reduce the system compliance while also improving the similarity of the frequency response function.

Investigation on PCD cutting edge geometry for Ti6Al4V high-feed milling

Some new research challenges are connected to new high-feed milling tools, developed recently to reduce the cutting time. The main objective of this article is to analyze if PCD tools could be used for high-feed face milling of Ti6Al4V. As its performance depends significantly on cutting edge geometry, different tool geometries were evaluated regarding tool life and cutting forces. Experimental investigations demonstrate that the tool profile, which has a discontinuity on chip flow direction along the cutting edge, presents an intense local tool wear and, consequently, a smaller tool life. The PCD tool having a straight edge has a longer tool life but, contrarily to the carbide tool theory, local wear behavior on the cutting edge is not constant when depth of cut increases. The cutting force magnitude, and its dynamic, affects drastically the tool life of PCD tools in milling and it is a limitation to the increase of the material removal rate. In conclusion, it is possible to use specific PCD tools for milling titanium alloy in high feed with low depth of cut (smaller than 1 mm), which is not economically practicable.

Study of Cutting Forces and Prediction of Surface Quality Analysis Using Neural Network Model, Support Vector Regression Model by Various Textured Tool Condition for Ti-6Al-4V Alloy

To evaluate the performance of the textured tool on surface quality with three different types of the textured pattern using Wire-Cut Electrical Discharge Machining (W-EDM) on tungsten carbide cutting tools with two different groove depth dimensions 100 μm& 200μm respectively and the tools are coated with both TiN and TiAlN using Physical Vapour Deposition (PVD) technique. Surface roughness is predicted using the Support Vector Regression, multilayer Artificial Neural Network model (ANN) model. ANN training is carried out with a pure line transfer function and backpropagation algorithm. Easy off machining and good surface finish are achieved through TiAlN coated tool with linear texture along the perpendicular to chip flow direction than the tools considered for experimental and predicted conditions.

Concept of energy efficient technological system: Machine tool – cutting tool – workpiece

AbstractThis study deals with the concept of increasing energy efficiency by means of decreasing the energetic losses by using advanced composite machine tool components and interfaces characterized by low friction, and high wear resistance. Moreover, this study provides experimental results of damping property measurements and characteristic time domain curves of the fibre, particle, and sandwich composites, underlining the advantages of such composite types in terms of dynamic loading. Furthermore, it provides an analysis on the usage of thin films (coatings) and energy consumption in terms of cutting conditions. The study analyses the cutting tool geometry and shape of cutting edge that positively affect the cutting forces and chip flow direction, and avoid the energy‐intensive restricted cutting effect. Respecting the results of the analyses of mentioned effects contributes to increasing the energy efficiency of the machine tool‐cutting tool‐workpiece system.

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%.

Effect of laser texturing on the performance of ultra-hard single-point cutting tools

This paper investigates the cutting performance and anti-adhesive properties of textured single-point polycrystalline diamond (PCD) cutting tools in machining Aluminium 6082 alloys. The micro/nano textures were first milled using a fibre laser (1064-nm wavelength) at different power intensities, feed speeds and pulse durations, and finally characterised using scanning electron microscopy, white light interferometry and energy dispersive X-ray spectroscopy. The effect of different textures on the cutting performance was investigated in turning tests under dry cutting conditions. The test was stopped at regular lengths of cut to allow analysis of height of adhesion through 3D white light interferometry. The data processing of the cutting forces and the microscopical characterisation of the tested cutting tools enabled the evaluation of the effects of texture design, friction coefficient and adhesive properties. The results indicated that feed force in tools with grooves perpendicular to the chip flow direction (CFD) was more stable (20–40 N) than the benchmark (6–41 N). Similarly, the thrust force for tools with grooves parallel to CFD and grooves perpendicular to CFD showed a homogeneous trend fluctuating between 60 and 75 N as compared with the benchmark (ranging between 73 and 90 N). For texture depth in the order of 260 nm and post process roughness in the order of tens of nanometers, a reduction of average friction coefficient (0.28 ± 0.14) was reported when using lasered inserts with grooves parallel to the chip flow direction compared with the benchmark tools (0.34 ± 0.26) corroborated by reduced stiction of workpiece material on the rake face. In machining via textured tools with grooves perpendicular to CFD, the cutting forces were reduced by 23%, and the surface quality of the machined workpiece was improved by 11.8%, making this geometry the preferred choice for finishing applications. Using grooves parallel to CFD reduced the cutting forces by 11.76%, adhesion by 59.36% and friction coefficient by 14.28%; however, it increased the surface roughness of the machined workpiece, making this geometry suitable for roughing operations. For the first time, laser manufacturing is proposed as a flexible technique to functionalise the geometrical and wear properties of PCD cutting tools to the specific applications (i.e. roughing, finishing) as opposed to the standard industrial approach to use microstructurally different PCDs (i.e. grain size and binder %) based on the type of operation.

Mechanical analysis of local cutting forces and transient state when drilling of heat-resistant austenitic stainless steel

In the present research work, mechanical aspect of transient state in drilling operation is investigated by analyzing together the cutting forces and the chip formation. Particularly, a sudden peak occurring on cutting forces during transient state is observed and deeply studied. To do so, new experimental methodologies to analyze local cutting forces when drilling heat-resistant austenitic stainless steel are introduced. The chisel edge and the cutting edge of each studied drill are numerically discretized as series of elementary cutting edges. Therefore, local cutting force evolution is correlated with the local cutting geometry variation along the cutting edge. On one hand, results have shown that for high ductile materials, local cutting geometry affects deeply not only the chip shape but also the chip flow direction. This strongly disrupts the monotony of the cutting forces evolution in transient state and lead to a sudden peak occurrence on cutting forces. On the other hand, linear local cutting forces could be determined by numerical decomposition of the global cutting forces measured during the drill tip engagement.

Performance of surface textured tools during machining of Al-Cu/TiB2 composite

During machining of Al-Cu/TiB2 composite, the friction between the face of the cutting tool and chip formed during machining causes wear on the tool which strongly affects the surface characteristics of machined surface. The interface friction can be managed by limiting the contact-area between the tool-chip interface and also by means of providing better lubrication between contacting surfaces. In the present work, areal and linear textures were created on rake surfaces of tungsten carbide cutting tools. Machining experiments were carried out using the above prepared textured tools under oblique cutting conditions on Al-Cu/TiB2 composites. Experimental results were used for the evaluation of machining forces and specific cutting energy consumption under dry and semi-solid lubrication condition. The tool wear analysis was carried out with different type’s tools for the machining of Al-Cu/TiB2 composite using optical micrographs and Scanning Electron Microscope (SEM) images. The chip formation was also analyzed during machining with different types of tools. Based on the present investigation, the cutting tool with linear texture in the perpendicular to the chip flow direction exhibits a better reduction in machining forces, specific energy consumption and tool wear.

Bio-inspired fabrication, mechanical characterization and cutting performance evaluation of Al2O3/TiC micro-nano-composite ceramic with varying microscopic surfaces

Bio-inspired fabrication, mechanical characterization and intermittent cutting performance evaluation were conducted for Al2O3/TiC micro-nano-composite ceramic with varying microscopic surfaces. Functions and geometry features of the epidermis were analyzed for two biological species, namely, catharsius molossus and bullhead shark. The biomimetic microscopic texture on ceramic tool surface was designed and fabricated considering tool-chip contact area and chip flow direction. Varying combinations of laser beam angle and spacing were utilized in the fabrication of biomimetic microscopic texture. Microscopic hardness, fracture toughness and fractal dimension of the indentation-induced crack were analyzed and compared for the textured ceramics. A tool performance indicator CP was proposed. Ceramic tool stress in cutting process, mechanical features of the intrinsic microcrack and fractal dimension of the indentation-induced crack were reflected in the indicator. The indicator CP was employed to evaluate the intermittent cutting performance of ceramic tools with different biomimetic microscopic textures. The optimum combination of laser beam angle φ and spacing Ld was found to be 60° and 105 μm. The lowest CP and the lowest experimental tool wear VB appeared at this optimum combination. A proper balance between external loads, micromechanical properties and fracture resistance can be achieved for the textured ceramic tool by using the optimum combination of φ and Ld.

Influence of wire-EDM textured conventional tungsten carbide inserts in machining of aerospace materials (Ti–6Al–4V alloy)

ABSTRACTImportance of this present investigation is to identify the influence of modified tool (tool with texturing) on the process of orthogonal turning of Ti–6Al–4V work material. To achieve the enhanced turning conditions, four different types of textures (plain conventional, cross, perpendicularly textured and parallel textured tool to the chip flow direction) were fabricated on the rake face of the tool insert and the lubricant used during the machining process is molybdenum disulfide (MoS2). Machining forces (the force of cutting and feed), angle of shear, chip morphology, temperature distribution between tool and chip were measured. Shear strain and strain rate were also computed and compared with all type of cutting tools. Experimental results revealed that the cross-textured cutting tool exhibit an effective reduction in cutting force, friction, shear strain and strain rate. The favorable metal removal condition of curling chip with low diameter was achieved through cross-textured tool.

Direction of chip flow for milling of shaped surfaces by ball end mill

There investigated the direction of chip flow on the front surface by machining with non-cylindrical original instrumental surface end mills.

Analysis of the minimum chip thickness during turning of duplex stainless steel

The goal of this study has been to establish a method for quantifying the minimum chip thickness, h1 min, during longitudinal turning of duplex stainless steel, and explore how the value of h1 min changes with varying process parameters. Based on experimental results, it was found that the tool edge radius only has a limited influence on the size of h1 min up to a certain feed level after which the chip flow direction close to the nose radius will have an increasingly pronounced effect. Experimental results show that h1 min may be as large as 40% of the theoretical chip thickness when machining duplex stainless steel, results which were corroborated by an finite element method (FEM) analysis. Thus, it can be concluded that a substantial amount of workpiece material will only be deformed onto the machined surface or will form the side flow and not removed as a chip.

Study of the Shear Strain and Shear Strain Rate Progression During Titanium Machining

Machining is among the most versatile material removal processes in the manufacturing industry. To better optimize the machining process, the knowledge of shear strains and shear strain rates within the primary shear zone (PSZ) during chip formation has been of great interest. The objective of this study is to study the strain and strain rate progression within the PSZ both in the chip flow direction and along the thickness direction during machining equal channel angular extrusion (ECAE) processed titanium (Ti). ECAE-processed ultrafine-grained Ti has been machined at cutting speeds of 0.1 and 0.5 m/s, and the shear strain and the shear strain rate have been determined using high speed imaging and digital image correlation (DIC). It is found that the chip morphology is saw-tooth at 0.1 m/s while continuous at 0.5 m/s. The cumulative shear strain and the incremental shear strain rate of the saw-tooth chip morphology can reach approximately 3.9 and 2.4 × 103 s−1, respectively, and those of the continuous chip morphology may be approximately 1.3 and 5.0 × 103 s−1, respectively. There is a distinct peak shift in the shear strain rate distribution during saw-tooth chip formation while there is a stable peak position of the strain rate distribution during continuous chip formation. The PSZ thickness during saw-tooth chip formation is more localized and smaller than that during continuous chip formation (28 versus 35 μm).

Phenomenological study of chip flow/formation and unified cutting force modelling during Ti6Al4V alloy turning operations

Mechanistic approach for prediction of cutting forces are showing limits when it comes to enhance the cutting force modelling for specific applications of high-value added and thin parts, which are made of difficult-to-cut materials such as titanium alloys. This is the reason why precise cutting force modelling is needed in order to avoid deflection during machining. Therefore, this contribution aims to improve the description of the chip formation in cutting force modelling thanks to an original experimental set-up built up to observe in-situ the chip flow and measure the cutting forces during Ti6Al4V turning. This study highlights the fact that the chip flow direction has a significant effect on cutting forces and can be influenced by several parameters. In view of the results obtained, a generalised chip flow direction model is suggested. Chips morphology observation is also conducted with the purpose of providing experimental observations physical meaning. Afterwards, a cutting force model is proposed which takes into account the chip flow direction influence.

Chip Morphology and Chip Formation Mechanisms During Machining of ECAE-Processed Titanium

Severe plastic deformation (SPD) processing such as equal channel angular extrusion (ECAE) has been pioneered to produce ultrafine grained (UFG) metals for improved mechanical and physical properties. However, understanding the machining of SPD-processed metals is still limited. This study aims to investigate the differences in chip morphology when machining ECAE-processed UFG and coarse-grained (CG) titanium (Ti) and understand the chip formation mechanism using metallographic analysis, digital imaging correlation (DIC), and nano-indentation. The chip morphology is classified as aperiodic saw-tooth, continuous, or periodic saw-tooth, and changes with the cutting speed. The chip formation mechanism of the ECAE-processed Ti transitions from cyclic shear localization within the low cutting speed regime (such as 0.1 m/s or higher) to uniform shear localization within the moderately high cutting speed regime (such as from 0.5 to 1.0 m/s) and to cyclic shear localization (1.0 m/s). The shear band spacing increases with the cutting speed and is always lower than that of the CG counterpart. If the shear strain rate distribution contains a shift in the chip flow direction, the chip morphology appears saw-tooth, and cyclic shear localization is the chip formation mechanism. If no such shift occurs, the chip formation is considered continuous, and uniform shear localization is the chip formation mechanism. Hardness measurements show that cyclic shear localization is the chip formation mechanism when localized hardness peaks occur, whereas uniform shear localization is operative when the hardness is relatively constant.

Effect of WEDM surface texturing on Al2O3/TiCN composite ceramic tools in dry cutting of hardened steel

Micro scale textures were fabricated on the rake surface of Al2O3/TiCN composite ceramic cutting tools using WEDM process. The cutting performance of ceramic cutting tools with plain and textured rake surfaces was investigated in the dry cutting of hardened AISI 52100 steel (62 HRC). The performance of cutting tools was evaluated by chip-tool contact length, tool wear, machining forces, cutting temperature, frictional coefficient and chip morphology. Further, a 3D finite element model has been used to study the temperature and stress distribution in the cutting tools. Application of textures obstructing the chip flow direction resulted in uniform stress distribution, and higher groove sliding area ensured maximum reduction of machining forces, material adhesion, cutting and tool temperature. However, the textures parallel to the chip flow direction resulted in bending and curling of chips on the rake face causing an increase of chip-tool contact length and material adhesion as compared to the tools with textures obstructing the chip flow resulting in an increase of friction. The textured tool with textures inclined at an angle to the chip flow direction exhibited the best machining performance as compared to other textured cutting tools. Moreover, this tool exhibited superior anti-adhesion behavior as compared to the conventional cutting tool owing to the reduced chip-tool contact length and area, friction and chip flow angle.

Modeling and experimental verification of chip flow deviation in oblique cutting

ABSTRACTThe reasons for chip deviation from the orthogonal direction in machining are (i) restricted cutting effect, (ii) nonzero inclination angle, and (iii) tool-nose radius. The present article has incorporated the concept of effective inclination angle in the models for predicting chip flow direction in oblique cutting. Model 1 takes into account the role of the effective principal cutting edge angle (as point function) and the concept of effective inclination angle has been incorporated in the model. Model 2 addresses the same roles but determined as path functions. Models 1 and 2 do not address the variation in the chip load along the width of cut. This has been addressed in Model 3 along with effective inclination angle. The models have been validated against the experimental data while turning two different medium carbon steels with uncoated carbide inserts over a wide domain of depth of cut, feed, cutting velocity, nose radius, rake angle, inclination angle and principal cutting edge angle. The major contribution of this work is the introduction of effective inclination angle along the effective cutting edge.

Defining the effects of cutting parameters on burr formation and minimization in ultra-precision grooving of amorphous alloy

Amorphous nickel phosphorus (Ni-P) alloy is a suitable mold material for fabricating micropatterns on optical elements for enhancing their performances. Ultra-precision cutting is preferred to be used to machine the mold material for high precision in a large workpiece. However, burrs and chippings always form and are detrimental especially when fabricating micropatterns. The formation mechanisms of burrs and chippings have not yet been revealed precisely in the cutting processes of amorphous alloys, because their cutting behavior is more complex and less discussed in existing researches than that of crystalline metals. In the present study, the burr formation process of amorphous Ni-P is defined and a three-dimensional cutting model using energy method is proposed to predict and minimize burrs and chippings. Microgrooving experiments were conducted with different undeformed chip geometries using three types of cutting tools to observe burr formation processes. Large burrs and chippings were formed when cutting with a tapered square tool and a tilted triangle tool. These large burrs and chippings were found to be induced by large slippages that are unique to amorphous alloys. It was revealed that burrs and chippings appear when the angle between the chip flow direction and the groove edge is less than a critical value. Energy method was used to predict the chip flow directions and the calculated results agree with the experimental ones, which proved that the energy method is valid for designing an appropriate undeformed chip geometry to reduce burrs and chippings in ultra-precision grooving.