Experimental studies on the cryogenic machining of biodegradable ZK60 Mg alloy using micro-textured tools

Reducing the contact area between the cutting tool rake surface and chip promotes the machining performance of the work material and increases the tool life. Magnesium alloys are ductile-lightweight materials that form continuous chips during machining. The present investigation discusses the orthogonal turning of ZK60 magnesium alloy with linearly textured cutting inserts under both dry and liquid nitrogen (LN₂) cooling conditions. Linear grooves that are parallel and perpendicular to chip flow direction were created using Nd-YAG laser on the tungsten carbide cutting inserts. The effect of texturing combined with the application of LN₂ cooling is studied by evaluating the machining temperature and forces, microhardness, surface roughness and tool wear. Textured tools considerably minimize the liaison area of the chip with the rake plane compared to non-textured tools, which resulted in favorable effects in machinability. In case of cryogenic machining, textured tools substantially minimize the friction by the coupled effect of micro-pool lubrication and the formation of thin-film lubrication between the tool–chip/tool–work interfaces. Parallel-textured tools aided with cryogenic cooling exhibit superior performance during machining among the different types of tools employed in the present investigation.     

Tool wear and tool life of PCBN,binderless cBN and wBN-cBN tools in continuous finish hard turning of cold work tool steel

The paper presents the results of comparative study of performance of cutting tools made of ceramic-bound, binderless cBN, and wBN-cBN tool materials. The tool performance was assessed by tool wear-resistance, values of cutting forces, parameters of machined surface quality, and the state of sub-surface layer generated in continuous turning of hardened cold work tool steel. The tests were carried out under conditions of high speed machining (v _c = 120–180 m/min) both with and without a coolant. The best tool performance by the above-mentioned criteria is provided by a low-cBN material with ceramic binder.     

Circular cutting strategy for drilling of carbon fiber-reinforced plastics (CFRPs)

The drilling process of carbon fiber-reinforced plastics (CFRPs) is the most commonly employed machining operation due to the necessity of joining these materials. However, these materials are prone to delaminate during the process, and the presence of this defect is the most cause of rejection for CFRP products, especially those produced for the aeronautic industry. Therefore, this article aims to study a drilling strategy (named circular drilling strategy) by using dedicated tools with different diameters, in order to reduce the extension of delaminations. Holes with different diameters (6, 8, and 10 mm) were obtained both with the conventional and with the proposed drilling strategy under distinct cutting conditions that mainly differ in the feed rates (62, 125, and 250 mm/min) and cutting velocities (50, 75, and 100 m/min). The effect of the cutting parameters and tool diameter on the cutting forces and delamination factor was studied for both the conventional and circular drilling process. The results proved that the proposed technique produces better hole quality and lower thrust forces than the conventional one under the same cutting conditions.     

Machining of high performance workpiece materials with CBN coated cutting tools

The machining of high performance workpiece materials requires significantly harder cutting materials. In hard machining, the early tool wear occurs due to high process forces and temperatures. The hardest known material is the diamond, but steel materials cannot be machined with diamond tools because of the reactivity of iron with carbon. Cubic boron nitride (cBN) is the second hardest of all known materials. The supply of such PcBN indexable inserts, which are only geometrically simple and available, requires several work procedures and is cost-intensive. The development of a cBN coating for cutting tools, combine the advantages of a thin film system and of cBN. Flexible cemented carbide tools, in respect to the geometry can be coated. The cBN films with a thickness of up to 2 µm on cemented carbide substrates show excellent mechanical and physical properties. This paper describes the results of the machining of various workpiece materials in turning and milling operations regarding the tool life, resultant cutting force components and workpiece surface roughness. In turning tests of Inconel 718 and milling tests of chrome steel the high potential of cBN coatings for dry machining was proven. The results of the experiments were compared with common used tool coatings for the hard machining. Additionally, the wear mechanisms adhesion, abrasion, surface fatigue and tribo-oxidation were researched in model wear experiments.     

Prediction of cutting force based on machining parameters on AL7075-T6 aluminum alloy by response surface methodology in end milling

Cutting forces modeling is the basic to understand the cutting process, which should be kept in minimum to reduce tool deflection, vibration, tool wear and optimize the process parameters in order to obtain a high quality product within minimum machining time. In this paper a statistical model has been developed to predict cutting force in terms of geometrical parameters such as rake angle, nose radius of cutting tool and machining parameters such as cutting speed, cutting feed and axial depth of cut. Response surface methodology experimental design was employed for conducting experiments. The work piece material is Aluminum (Al 7075-T6) and the tool used is high speed steel end mill cutter with different tool geometry. The cutting forces are measured using three axis milling tool dynamometer. The second order mathematical model in terms of machining parameters is developed for predicting cutting forces. The adequacy of the model is checked by employing ANOVA. The direct effect of the process parameter with cutting forces are analyzed, which helps to select process parameter in order to keep cutting forces minimum, which ensures the stability of end milling process. The study observed that feed rate has the highest statistical and physical influence on cutting force.     

Material selection for the tool holder working under hard milling conditions using different multi criteria decision making methods

Nowadays machining of materials in their hardened state, also called hard machining, is a challenge in production of tools and molds. It has some advantages such as lower process time and lower manufacturing cost when compared to conventional machining. In machining of hard workpiece materials, however, very high stresses act on the tool holder through the cutting tool. These stresses necessitate the tool holder to have some specific properties. Especially in hard milling, the tool holder should have high stiffness and should be able to dissipate the energy generated during interrupted cutting. Material cost of the tool holder is also important since lower costs provide a competitive advantage for manufacturers. The material selection for the tool holder should be conducted considering aforementioned requirements. To tackle the difficulty of the material selection with specific properties from a large number of alternatives, multi-criteria decision-making (MCDM) methods have been used. In this paper a decision model including extended PROMETHEE II (EXPROM2) (preference ranking organization method for enrichment evaluation), TOPSIS (technique for order performance by similarity to ideal solution) and VIKOR (VIšekriterijumsko KOmpromisno Rangiranje) methods were used for the selection of the best material for the tool holder used in hard milling. The criteria weighting was performed by compromised weighting method composed of AHP (analytic hierarchy process) and Entropy methods. The candidate materials were ranked by using these methods and the results obtained by each method were compared. It was confirmed that MCDM methods can be used for the solution of real time material selection problems. Tungsten carbide–cobalt and Fe–5Cr–Mo–V aircraft steel were found as the best materials for the tool holder production. The obtained results are found to be rather satisfactory and can be used in design stage of hard machining operations.     

Ultrasonic vibration-assisted machining:principle,design and application

Ultrasonic vibration-assisted(UVA) machining is a process which makes use of a micro-scale high frequency vibration applied to a cutting tool to improve the material removal effectiveness.Its principle is to make the tool-workpiece interaction a microscopically non-monotonic process to facilitate chip separation and to reduce machining forces.It can also reduce the deformation zone in a workpiece under machining,thereby improving the surface integrity of a component machined.There are several types of UVA machining processes,differentiated by the directions of the vibrations introduced relative to the cutting direction.Applications of UVA machining to a wide range of workpiece materials have shown that the process can considerably improve machining performance.This paper aims to provide a comprehensive discussion and review about some key aspects of UVA machining such as cutting kinematics and dynamics,effect of workpiece materials and wear of cutting tools,involving a wide range of workpiece materials including metal alloys,ceramics,amorphous and composite materials.Some aspects for further investigation are also outlined at the end.     

Design of hybrid steel/composite circular plate cutting tool structures

Substituting composite structures for conventional metallic structures has many advantages because composite materials have both high specific stiffness and damping characteristics compared to conventional metallic materials. In this study, circular plate cutting tools which are used for rough machining of bearing sites in crankshafts or camshafts were designed with the fiber reinforced composite material to reduce tool mass and to improve the dynamic stiffness of circular plate cutting tools. The hybrid steel/composite circular plate cutting tool was analyzed by finite element method with respect to material types such as composite and foam, stacking angles of the composite, adhesive bonding thickness, and dimensions of the cutting tool. Also, the constrained damping characteristics of the tools were experimentally investigated with respect to the adhesive bonding thickness and material type such as composite and PVC foam. From the finite element analysis and experimental results, optimal design parameters for the hybrid steel/composite circular plate cutting tool were suggested.     

Experimental study on the meso-scale milling of tungsten carbide WC-17.5Co with PCD end mills

Tungsten carbide is a material that is very difficult to cut, mainly owing to its extreme wear resistance. Its high value of yield strength, accompanied by extreme brittleness, renders its machinability extremely poor, with most tools failing. Even when cutting with tool materials of the highest quality, its mode of cutting is mainly brittle and marred by material cracking. The ductile mode of cutting is possible only at micro levels of depth of cut and feed rate. This study aims to investigate the possibility of milling the carbide material at a meso-scale using polycrystalline diamond (PCD) end mills. A series of end milling experiments were performed to study the effects of cutting speed, feed per tooth, and axial depth of cut on performance measures such as cutting forces, surface roughness, and tool wear. To characterize the wear of PCD tools, a new approach to measuring the level of damage sustained by the faces of the cutter's teeth is presented. Analyses of the experimental data show that the effects of all the cutting parameters on the three performance measures are significant. The major damage mode of the PCD end mills is found to be the intermittent micro-chipping. The progress of tool damage saw a long, stable, and steady period sandwiched between two short, abrupt, and intermittent periods. Cutting forces and surface roughness are found to rise with increments in the three cutting parameters, although the latter shows signs of reduction during the initial increase in cutting speed only. The results of this study find that an acceptable surface quality (average roughness R_a<0.2 μm) and tool life (cutting length L>600 mm) can be obtained under the conditions of the given cutting parameters. It indicates that milling with PCD tools at a meso-scale is a suitable machining method for tungsten carbides.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-020-00298-y     

Cost-effective way of hard turning with newly developed HSN2-coated tool

EN-31 (AISI 52100, hardness 55 HRC) is one of the difficult-to-cut steel alloys and it is commonly used in shafts and bearings. Nowadays, it is becoming a challenge to the cutting tool material for economical machining of extremely tough and hard steels. In general, CBN and PCBN tools are used for machining hardened steel. However, machining cost using these tools becomes higher due to high tool cost. For this purpose, carbide tool using selective coatings is the best substitute having comparable tool life, while its cost is approximately one-tenth of CBN tool. In this work, the newly developed second-generation TiAlxN super nitride (i.e., HSN²) is selected for PVD coating on carbide tool insert and further characterized using thermogravimetric analysis and differential scanning calorimetry for oxidation and thermal stability at high temperature. Later, HSN²-coated carbide inserts are successfully tested for their sustainability to expected tool life for turning of AISI 52100 steel. In the present study, forces, surface finish, and tool wear are used as a measure to appraise the performance of hard turning process. Experimentally, it is found that speed, feed rate, and depth of cut have considerable impact on forces, insert wear, and surface roughness of the machined surface.     

Rotary ultrasonic machining— a new cutting process and its performance

In conventional ultrasonic machining (USM), brittle materials are machined by using ultrasonic impacts on the workpiece, through a medium of abrasive slurry. In this paper a new cutting process that resulted due to introduction of an additional parameter, namely the rotation of the workpiece during the machining, is presented. This may be called ‘rotary ultrasonic machining’. The material removal rates (MRR) in rotary USM are up to four times those in conventional USM. The MRR increases with increase in speed of rotation of workpiece. An explanation for the superior performance of rotary USM is presented. The performance of rotary USM as a function of static load, abrasive grain size, concentration of abrasive slurry, diameter of tool and ratio of diameters of hollow tools, is studied and the parameters are optimized for minimum machining time or maximum material removal rate. Comparisons are made with conventional USM.     

Influence of Tool Coating,Tool Material,and Cutting Speed on the Machinability of Low-Leaded Brass Alloys in Turning

The influence of tool coating and material on the machinability of low-leaded brass alloys (Pb < 0.2%) was analyzed in external turning. Carbide tools with various coatings as well as polycrystalline diamond (PCD) tools were applied. As workpiece materials, three low-leaded brass alloys CuZn38As, CuZn42, and CuZn21Si3P were used. Their machining behavior was compared to the leaded (Pb < 3.32%) brass CuZn39Pb3. CuZn38As showed the worst machinability in terms of process forces, chip formation, and workpiece quality. This is due to the high volume fraction of α-phase with face-centered cubic lattice structure. The machining problems were reduced by the use of tool coatings, in particular by a diamond-like carbon coating. The latter is characterized by high hardness, diamond-like cubic-crystalline lattice structure, and low chemical affinity to brass, which reduced friction in the secondary shear zone. CuZn42 exhibited an improved machinability compared to CuZn38As due to the lower volume fraction of α-phase. The positive influence of the tool coating was similar to CuZn38As. Main machining problem of CuZn21Si3P is tool wear because of the hard silicon-rich κ-phase. In tool life tests, PCD showed higher performance than uncoated and coated carbide tools due to its high abrasive wear resistance and low adhesion tendency.     

Optimizing the performance of high speed steel circular saw blades machining cupro 107, Inconel 600L and Nimonic PK31 nickel based alloys

Nickel based alloys are machined by methods similar to those used to cut ferrous materials, however there are additional process requirements due to the poor machinability of these alloys. The current paper reports on work undertaken to optimize the cutting conditions for high speed steel circular saw blades machining materials from three of the principal categories of nickel based alloy.Techniques have been developed and verified that simulate the cutting characteristics of multi-point cutting tools by testing blade segments that contain representative teeth. The cutting behaviour of high speed steel circular saw blades have been simulated in this manner. Materials from three of the principal classifications of nickel based alloy; Cupro 107, Inconel 600L and Nimonic PK31, have been machined over a range of cutting feeds and speeds. Cutting and thrust forces were measured and the performance criteria, specific cutting energy (Esp) evaluated. Optimized cutting conditions for each material were determined from curves of Esp against feed rate at the selected cutting speeds.In an area of high product and material costs, the information contained within this paper will be of interest to the manufacturing engineer and end user when appraising the suitability of high speed steel circular saw blades as a tool for machining these materials.Inconel 600L and Nimonic PK31 are registered trademarks of the Inco Family of Companies.     

Effects of Filler Concentration and Cutting Parameters on Material Properties and Machinability of SiC-Filled Epoxy Tooling Board

An experimental study was conducted to examine the material properties and machinability of a silicon carbide (SiC)-filled epoxy conductive tooling system (RP4037 CAST-IT^TM). Specifically, the effects of SiC filler concentration and machining process parameters (cutting speed and feed) on the physical and material properties, resultant cutting force, surface integrity, and tool wear were studied. Machinability evaluation was carried out using the end milling process. The study showed that an increase in filler concentration significantly increased the density, thermal conductivity, resultant machining forces, surface roughness of the machined surface, and tool wear. However, it had insignificant impact on the glass transition temperature, strength, or hardness. A decrease in material strength was observed with increasing cutting speed and feed. Increasing filler concentration was also found to degrade the machined surface morphology. Possible explanations for the observed effects are discussed.     

Advanced ceramic tool materials for machining

Cutting tools made of advanced ceramics have the potential for high-speed finish machining as well as for high-removal-rate machining of difficult-to-machine materials. The raw materials used in these ceramics are abundant, inexpensive, and free from strategic materials. In spite of this, solid or monolithic ceramic tools are currently used only to a limited extent partly due to certain limitations of these materials and partly due to the inadequacy of the machine tools used. The advances in ceramic materials and processing technology, the need to use materials that are increasingly more difficult to machine, increasing competition, and the rapidly rising manufacturing costs, have opened new vistas for ceramics in machining applications. The development of ceramic tool materials can be broadly categorized into three types: monolithic forms, thin coatings, and whisker-reinforced composites. Such a classification provides a totally new perspective on ceramic tool materials and broadens their scope considerably, and is justified on the basis that it is the ceramic addition that makes the tool material more effective. A brief overview of these materials is presented in this paper.     

Investigating the Machinability of AISI 420 Stainless Steel Using Factorial Design

This work aims at studying the machining characteristics of high-strength materials using carbide cutting tool inserts at different cutting conditions. This is an essential step in building up an accurate machining information system. The tested material is high-strength stainless steel of the AISI 420 type. Machining tests were carried out using orthogonal cutting conducted to investigate the machining characteristics for high-strength stainless steel AISI 420 at different cutting conditions and tool rake angles. This assessment is achieved by investigating the effect of cutting parameters (cutting speed, feed, depth of cut, and tool geometry) on cutting forces, specific cutting energy, shear angle, coefficient of friction, shear stress, shear strain, and shear strain rate. Empirical equations and a correlation for the behavior of each of the output responses were investigated as a function of the independent variables. Main effect and interaction plot were presented for the most influential factors affecting the main cutting force and the power consumed.     

Experimental study on the wear evolution of different PVD coated tools under milling operations of LDX2101 duplex stainless steel

Duplex stainless steels are being used on applications that require, especially, high corrosion resistance and overall good mechanical properties, such as the naval and oil-gas exploration industry. The components employed in these industries are usually obtained by machining, however, these alloys have low machinability when compared to conventional stainless steels. In this work, a study of the wear developed when milling duplex stainless-steel, LDX 2101, is going to be presented and evaluated, employing four types of milling tools with different geometries and coatings, while studying the influence of feed rate and cutting length in the wear of these tools. Tools used have been provided with two and four flutes, as well as three different coatings, namely: TiAlN, TiAlSiN and AlCrN. The cutting behavior of these tools was analyzed; data relative to the cutting forces developed during the process were obtained; and roughness measurements of the machined surfaces were executed. The tools were then submitted to scanning electron microscope (SEM) analysis, enabling the identification of the wear mechanisms that tools were subjected to when machining this material, furthermore, the early stages of these mechanisms were also identified. All this work was done with the goal of relating the machining parameters and cutting force values obtained, identifying, and discussing the wear patterns that were observed in the coating and tools after the milling tests, providing further information on the machining of these alloys. The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00401-5     

Simulation and experimental investigation of finishing forces in magnetic field assisted finishing process

Finishing forces in magnetic field assisted finishing process are normal force responsible for indentation and tangential force responsible for removal of indented materials. Analysis of finishing forces helps to understand the process mechanism and to control the process precisely. Simulation of finishing forces in magnetic field assisted finishing process is conducted using two finite element method based software packages. The experimental study confirms the simulation results as the difference between the obtained results from both the study is very small. A model is simulated for material removal using magnetorheological fluid having diamond abrasive particles on Ti alloy workpiece surface to predict material dislodgement during finishing. The significance of each process parameters is found out with the help of statistical analysis. The significant process parameters for normal force are abrasive volume concentration, working gap and carbonyl iron particle (CIP) volume concentration and for tangential force are tool rpm, working gap, and CIP volume concentration. It is perceived that the normal force rises with a surge in CIP concentration and reduction in abrasive concentration in MR fluid, working gap and tool rpm. The magnitude of tangential force rises with increased tool rpm, CIP concentration, abrasive concentration and decreased working gap.     

Spanen metallischer Konstruktionswerkstoffe geringer Dichte

Machining of light metals Magnesium, aluminium and titanium are the only light metals that are also used in construction. They offer a significant prerequisite for weight reduction of workpieces. Especially the automotive and the aerospace industry have an increasing interest in using these lightweight materials as well as their alloys. The machining of light metals however is accompanied with several problems. With increasing the cutting speed high adhesive and abrasive effects between the cutting tool material and the workpiece material can occur. These effects lead to unsteady processes and also have a negative influence on the quality of functional surfaces as well as their subsurface properties. The influence of cutting tool materials, tool coatings and cutting conditions affecting the process when cutting magnesium, aluminium and titanium alloys is described. Adhesion can be reduced when machining magnesium and aluminium alloys in particular by the application of diamond-coated tools and by PCD-inserts. Diamond tools, due to their low coefficient of friction and the high thermal conductivity, furthermore contribute to the decrease of the thermal load within the contact zone between workpiece and cutting tool. Subsequently the danger of magnesium chip ignition can be minimized. For the machining of titanium alloys modern coatings based on (Ti,Al)N and TiCTiN are applied to reduce the adhesive and abrasive wear.