High Performance Machining Research Articles

Temperature and force measurements in single diamond scratch tests

Analysis of the highest temperature in the machining processes, namely the flash temperature, helps to understand the physics of the process, to improve cutting tool geometry, and to achieve high performance machining. In the present work, the interaction between cutting grain and workpiece material in grinding process is analyzed. Single diamonds are considered for machining, which operates in comparison to other measurements in the range of grinding speed. The highest temperature in the grain-material interaction and cutting forces are measured. In order to measure the flash temperature, an innovative method to measure and analyze the temperature through the diamond grain in the cutting zone by a two-color pyrometer is proposed. Furthermore, cutting forces are measured simultaneously. In order to measure the temperature in the cutting zone, an accurate connection between diamond and pyrometer fiber is required. Thus, the diamond tool holders are manufactured by electrical discharge machining (EDM) milling in deionized water. A 0.5-mm-diameter hole is drilled in each holder to connect the diamond precisely to the pyrometer fiber. Machining processes are performed with 30 {\mu}m depth of cut, cutting length of 20 mm, and cutting speed of 65 m/s on Ti6Al4V. The cutting tool is fixed, and the shape of the rotating workpiece is optimized. The diamond holder with the specific shape is designed and manufactured. Quasi-static, dynamic, modal, and harmonic response analyses are performed in order to reduce vibrations and chattering. The measured flash temperature is 1380 {\deg}C and cutting normal, tangential, and axial forces are measured.

High-performance machining of fiber-reinforced materials with hybrid ultrasonic-assisted cutting

A main approach for sustainable and efficient products is the application of innovative materials like fiber-reinforced plastics. Despite the excellent properties, the machining requirements, especially the hard cutting conditions, restrain the wide application of these materials. Thus a major task is the realization of the required part qualities combined with efficient machining strategies. The project ULTRASPAN, a joint venture of partners from industry and research institutes funded by the BMBF, attends to this challenge. The goal is the development of new hybrid machining concepts and process technologies for enhanced cutting of composite materials with ultrasonic-assistance. Prior condition is the development of novel robust actuators. Therefore, prototypic actuators for longitudinal and torsional vibration systems are developed in the project. Besides the novel actuator concepts, the results of ultrasonic-assisted drilling (UAD) on composite parts are presented in this paper. Machining tests in drilling of fiber-reinforced plastics with the novel prototype actuator systems were performed. Focus of the investigation was the influence of the ultrasonic vibration support on the bore quality. The superimposition of drilling with ultrasonic vibrations influences the process characteristics and engagement of the cutting edge. Machining tests showed the potential to enhance the bore quality with UAD in a certain parameter field.

A predictor-corrector-based holistic-discretization method for accurate and efficient milling stability analysis

Chatter vibration in milling has been one crucial factor hindering the realization of high-performance machining. The corresponding stability analysis is of great significance for obtaining chatter-free machining parameters. Based on the predictor-corrector scheme, this paper develops an accurate and efficient holistic-discretization method for the stability analysis of milling processes. According to the system state equation, the period of the time-periodic coefficient matrix is divided into two time intervals. The forced vibration time period is then equidistantly discretized. Working as a holistic unit, the time-periodic parameter matrix, the state term, and the delay term are approximated over two different subintervals by the second-order Lagrange interpolations. Finally, the Floquet transition matrix can be constructed by taking advantage of the predictor-corrector scheme, and the milling stability can be semi-analytically determined by utilizing the Floquet theory. The computational accuracy of the proposed method is analyzed theoretically and illustrated by making comparisons with the first-order semi-discretization method (1st SDM), the second-order, and the third-order updated full-discretization methods (2nd UFDM and 3rd UFDM). The stability lobes for two benchmark milling models and the computational efficiency of these methods are presented to further verify the effectiveness of the proposed method. Theoretical analysis and numerical results validate that the proposed predictor-corrector-based holistic-discretization method achieves both high computational accuracy and efficiency for milling stability analysis. In conclusion, the proposed semi-analytical algorithm has a high potential for industrial applications.

Optimization of machining process parameters in conventional turning operation of Al5083/B4C composite under dry condition

Experiments are performed on Al5083 metal matrix composite reinforcement of 7%B4C. The turning process is carried out by using HSS single point cutting tool under the dry condition. In the present experiment the turning parameters such as cutting speed, feed rate and depth of cut are being optimized by considering constant length of material being machined. In the metal cutting process the proper cutting parameter will affect the quality of the finished product, In Ex-situ form B4C particle used for reinforcing the material. The reinforced aluminium matrix composites have some special properties which make them use for various purposes. The presence of B4C particle in Al matrix makes them difficult in machining, for the achieving of industrial requirement. The influence of B4C particle in Al5083 was studied experimentally and optimal machining condition is studied in this experiment. In this present study, the BA, ABC and PSO algorithm is applied to determine the optimal parametric combinations and compare between them for achieving better and higher machining performance and it is observed that the among, PSO algorithm gives better results.

Effect of Process Parameters on Hole Diameter Accuracy in High Pressure Through Coolant Peck Drilling Using Taguchi Technique

Machining with pressurized coolant is nowadays widely accepted technique in the manufacturing industry, especially in high performance machining conditions. The data on the effects of variation of high coolant pressure in drilling operation is limited. This paper presents the effect of high coolant pressures along with spindle speed, feed rate and peck depth on hole diameter accuracy. Experiments were performed on EN9 steel with TiAIN coated through coolant drill on CNC vertical machining center. Taguchi technique was employed for design of experiments and analysis of results. Results showed that the higher values of optimal coolant pressure and spindle speed were demanded for drilling at bottom of hole as compared to that for drilling at top of hole. The optimal values of feed rate and peck depth were same for both the cases of drilling at top and bottom of hole. Use of high coolant pressure in drilling permits higher peck depth for better hole diameter control which results in reduced cycle time and hence production cost.

Influence of the Grinding Wheel Topography on the Thermo-Mechanical Stress Collective in Grinding

The grinding process is used for both high-performance machining and surface finishing of hardened steel. In addition to the grinding parameters and the grinding fluid supply, the topography of the grinding wheel mainly determines the grinding process behavior and the grinding process result. An alteration of the topography by a variation of the volumetric composition of the grinding wheel, by a variation of the grinding wheel conditioning, or by wear causes a change in the contact conditions. The state of the art shows a substantial knowledge deficit about the influence of the volumetric grinding wheel composition and the resulting grinding wheel topography on the thermo-mechanical stress collective acting on the workpiece external zone. Thus, it is not possible to make a quantitative statement about the influence of the volumetric grinding wheel composition on the external zone properties of a component after grinding. Therefore, the aim of the current research is an empirical-analytical model for the prediction of the thermo-mechanical stress collective as a function of the grinding wheel topography. For this purpose, a methodology is developed, which enables the prediction of the topography-dependent thermo-mechanical load in a grinding process. Therefore, the topography is characterized by means of quantitative parameters and the main influencing variables on the grinding process behavior are investigated. The findings are used to analyze the influence of a change in the topography on the grinding temperature and the grinding force. The obtained results are summarized and are used to explain the thermo-mechanical stress collective as a function of the grinding wheel topography.

Assessment on abrasiveness of high chromium cast iron material on the wear performance of PCBN cutting tools in dry machining

Polycrystalline Cubic Boron Nitride (PCBN) has been considered as the main cutting tool material for hard turning, which has the comparable surface finish quality as grinding, and high efficiency, economical technology in production. It is well known that the abrasiveness of the workpiece have the very important role of the machinability of the materials. Therefore, the tool wear of the PCBN insert correlates with abrasiveness of the materials very much. In the presented paper, the influence of the micro hardness distribution is used to explain the wear mechanism in machining of the high abrasive materials and proposed a model to predict the abrasiveness. The work material is high chromium cast iron and cutting tool material is PCBN. Abrasiveness are evaluated from the micro hardness distribution by nanoindentation for the distinguish microstructure with hardness. The mapping image of the micro hardness showed the matched features with microstructure images from the scanning electron microscope (SEM). The different chemical composition groups are presented as three heat treatment conditions in experiments, which are as-cast, annealed and hardened. Based on the hardness distribution, this paper presented a model to evaluate the abrasiveness index of the material. The high performance machining is done on six material. The wear mechanism is abrasion in tool wear dominantly and flank wear showed the linear relationship with abrasiveness index. The abrasive wear on the cutting edge suggests that sliding and chipping are the main wear modes which is caused by the combination effect of carbides and matrix. The four mechanisms of diffusion, chemical, abrasive and micro chipping are happening in the tool wear of hard turning. In the dry machining by PCBN insert, abrasiveness is correlated with abrasive and chipping very much and accelerated the crater wear in machining. Abrasiveness index of the material has ability to predict wear performance in dry machining of HCWCI materials by PCBN inserts. The application of the abrasiveness is a potential parameter of machinability to improve the machining efficiency and reduce the cost of machining.

Investigation of machinability in turning of difficult-to-cut materials using a new cryogenic cooling approach

A new cooling technique is proposed to improve effectiveness of the minimum quantity lubrication (MQL) and cryogenic carbon dioxide (CO2) cooling in high performance machining of hard-to-cut materials. The combination of minimum quantity carbon dioxide and oil (CMQL) supplied from the rake face are compared with CO2 and MQL supplied from rake and flank faces, respectively, as well as only CO2 supplied from rake face, in turning of Ti6Al4V and Inconel 718. Tool wear, surface roughness and temperature measurements were performed to quantify the cooling impact of the various methods. Based on the systematical test results, CMQL was identified as the most favorable cooling method considering environmental impact, tool wear, surface finish, chip formation and cutting forces.

TECHNOLOGY OF REPAIR AND RESTORATION OF LARGE-MODULAR GOLDEN GEAR WHEELS BY HIGH-SPEED WOOD PROCESSING

The subject of the research in the article are topical issues related to the development of technology for the repair and restoration of large-sized gears of drives of walking excavators, ore-grinding mills, ball mills. The goal is to develop a new technology for repairing and repairing large-sized gears with a module (m = 12-65 mm). The task is to obtain a guaranteed quality of restoration of gear rims after repair with high-performance machining of large wheels operating in an aggressive abrasive environment. The method of intermittent rolling with the use of disk non-modular cutters is proposed (the dimensions of the mill do not depend on the module of the treated teeth), equipped with ceramic plates and special milling calipers. The method of intermittent rolling is used on gear-grinding and gear grinding machines and has the advantage that at the time of the working stroke of the tool the workpiece is either stationary or makes a slight turn, i.e. The treatment proceeds in comparison with the running-in method, under more stringent conditions. Results of implementation. Two new directions were adopted for the implementation of the new high-speed dental processing technology. The first was the development of simple special milling calipers mounted on the chamfering machines of MAAG (Switzerland). The second accounted for the extremely small number of factories that had MAAG machines, and therefore envisaged the development, manufacture and introduction of special milling calipers to widely used vertically hobbing machines. The introduction of a new technology for repairing and rebuilding toothed wheels during the finishing of hardened wheels with the use of a gear-cutting machine was carried out in production conditions when machining the wheels of a pseudo-planetary gearbox with the following characteristics: m = 28 mm; ; ; ; b = 400; ; steel 34ХМЮАА; HRC 48 ... 54. In comparison with the process of gear grinding, in which tensile stresses are created in the surface layer of the part, the blade treatment is most favorable. Compressive stresses increase wear resistance of parts, contractual and flexural strength of gears. Conclusions. The industrial introduction of new technology of blade machining of repair and restored large-sized gear wheels makes it possible to reduce the labor intensity of a finishing operation 3-4 times, and also eliminates the need to purchase expensive and low-performance gear grinding machines for import. In this case, the surface quality of the teeth is higher than in the case of gear grinding, because Excludes defects such as burns, microcracks.

Modification of surface morphology to enhance tribological properties for CVD coated cutting tools through wet micro-blasting post-process

Coated cemented carbide tools have been widely applied in high performance machining due to their excellent heat resistance and anti-wear properties. However, as-deposited tool coatings are still challenged by the growing requirements to further enhance cutting performance. Wet micro-blasting post-process on coating tools has been proposed to improve mechanical properties and increase tool life. This paper aims to optimize the wet micro-blasting operating parameters for chemical vapor deposition (CVD) coated tools to strengthen their wear resistance. The surface morphology of three types of CVD coated tools including TiN/Al2O3/TiCN, thin Al2O3/TiCN and thick Al2O3/TiCN are inspected with EDS, SEM and AFM. Tribological properties for both as-deposited and wet micro-blasted tool coatings were evaluated by dry reciprocating sliding tests. The measured results indicate that the wet micro-blasting process can significantly decrease the surface roughness and improve the wear resistance. Among the wet micro-blasting operating parameters, the wet micro-blasting time and the abrasive particle size are found to play more important roles in the formatting of top surface morphology and the enhancement of the tribological behavior than the role played by blasting pressure. Based on the research results, the CVD tool coatings with improved anti-wear properties and surface topography can be fabricated with suitable wet micro-blasting process parameters.

The Effects of Milling Strategies on Forces, Material Removal Rate, Tool Deflection, and Surface Errors for the Rough Machining of Complex Surfaces

The high-performance machining of curved surfaces is a highly critical process that is crucial in modern engineering applications. Different methodologies and CAM tools have been developed by manufacturers to improve the efficiency of the sculptured surface milling. The determination of appropriate tool path strategies and milling conditions is crucial in ensuring a high productivity rate, meeting the bettersurface texture values, and lower cutting forces, tool deflection, and surface errors. The objective of this research is to analyse the effect oftool path strategies on dynamic tool deflection, cutting forces, machining time, effective cutter diameter (ECD), cutter/workpiece engagement (CWE) area, instantaneous material removal rate (IMRR), and machining errors in rough machining of a sculptured surface. The B-rep solid modeling-based simulation and the optimization system were developed and integrated with the commercial CAD/CAM software for 3-axis ball-end milling. The experimental results clearly show the influence of the cutter path strategies on machining times and their importance for reducing time needed and, consequently, costs. It was observed that the profiles of deflection, IMRR values, cutting forces, machining errors and ECD values match very well for cutting strategies. Machining strategies employed include various degrees of zig-zag, profiling, and spiral. The conclusion is that the 90° zig-zag strategy provokes the lowest cutting forces, tool deflection, and surface error values. The in-house NC simulation system performed well in determining values and the location of milling form errors on the surface.

Investigations on Additive Manufacturing of WCCo Hard Metals by Laser Beam Melting

Abstract Tungsten carbide-cobalt hard metal produced by additive manufacturing offers opportunities to meet the increasingly complex requirements of high-performance machining. Besides a high level of design freedom and the easy integration of functional properties, the additive manufacturing of hard metals also offers potential for cost savings and conservation of resources. A window of favorable process parameters for laser beam melting was established using commercially available carbide powder with 17 % Co content, which serves to build carbide samples by laser-based additive manufacturing. Compared to conventionally manufactured carbides, deviations can still be noticed with regard to microstructural and mechanical properties. However, bending strengths of > 1 000 MPa and fracture toughness in the range of 10–12 Mpa √m are promising for the future additive manufacturing of WCCo hard metals.

Numerical simulation of interaction of mode-coupling and regenerative chatter in machining

Chatter vibration is a major obstacle in achieving high performance machining. In order to present a realistic model of chatter vibration, in this research, a finite element simulation of orthogonal chip formation combined with a 2D model of machine tool dynamics is developed. The proposed approach has the ability to incorporate various, mostly nonlinear, phenomena affecting chatter occurrence. The dynamic allows the tool to vibrate as a result of chip load variation leading to chatter. The 2DOF model makes it possible to observe the occurrence of model coupling phenomenon, in addition to the regeneration of waviness mechanism. The investigation of mode-coupling and regeneration phenomena in turning demonstrate the interaction between these two major mechanisms of chatter. It is observed that with the inclusion of mode coupling, the process becomes unstable more quickly. The model is verified through comparison with experimental results.

An accurate and efficient approach to geometric modeling of undeformed chips in five-axis CNC milling

Many important and complex parts, such as aero-engine compressors and automotive punch dies, are often machined in five-axis computer numerically controlled (CNC) milling. To machine the parts with accurate dimensions and shapes and low machining costs it is necessary to construct 3D models of the finished parts in the geometric simulation and in-process workpiece models of the parts in the physical simulation of their five-axis milling. A kernel technique of the geometric and the physical simulations is to accurately and efficiently model the geometry of the workpiece material removed at every moment of the machining, which is the instantaneous, undeformed chip geometry. Although in the past decades much research has been conducted on modeling cutter swept volumes in CNC milling to represent the finished part geometry in the geometric simulation, it is very time consuming to calculate the instantaneous, undeformed chip geometries using the cutter swept volumes. Besides, the existing method of modeling undeformed chip geometry in three-axis milling cannot be used for that in five-axis milling. To address this problem, our work proposes an accurate and efficient approach. In this article, a generic theory about the boundary of the area covered by the instantaneous cutting edges on a workpiece layer at any moment is established, which is called the boundary theory. A simple diagram of determining the boundary is invented, which is called boundary construction diagram. This approach lays a theoretical foundation for the geometric and the physical simulations of five-axis milling and will significantly promote them for high performance machining in industry.

Effects of rolling bearing configuration on stiffness of machine tool spindle

Rolling bearings are widely used in the complex mechanical systems as important components. With the advancement in the manufacturing technology, the requirements of high-performance machining tool became essential. A bearing is one of the most important components of spindle, and it is a crucial factor in determining the overall quality. The configuration of bearings of spindle is the key problem during high-performance spindle design, which influences the performance of spindle, especially stiffness. This paper aims to develop a method to analyze various spindle stiffnesses with different configurations of bearing to support the optimization of spindle. Firstly, a quasi-static model is established to solve stiffness matrix of bearing, and then a spindle-bearing system mathematical model is established. Secondly, the stiffness matrix of bearing is added into the whole system to form an integrated spindle-bearings model. Finally, the spindle stiffness with different bearing configurations are analyzed. The results indicate that the number of bearings influences the spindle radial stiffness and bearing direction affects the spindle axial stiffness. Once the number and direction are specified, reasonable pre-load method, shorter overhang, and proper span can greatly improve the spindle dynamic characteristics. In addition, an experimental spindle is designed and fabricated to test various axial stiffnesses with different bearing configurations, and stiffness characteristics of commonly used bearing configurations are summarized from the experimental results and provide useful guide for the spindle design.

ПРИМЕНЕНИЕ МЕТОДА ВЫСОКОПРОИЗВОДИТЕЛЬНОГО ФРЕЗЕРОВАНИЯ ДЛЯ РЕЗАНИЯ КОНСТРУКЦИОННЫХ СТАЛЕЙ

The implementation of high-speed machining (HSM) allows minimizing the processing time, raising the specific volume cutting efficiency, and achieving the range of advantages having a positive effect on the economic efficiency of this method. However, to implement this technology in practice, it is necessary to follow the set of measures and requirements to the manufacturing system. In particular, the wide use of HSM negates the necessity of having the expensive equipment – specialized CNC machines (computerized numerical control machines). The research of HSM in practice resulted in the modifications of this type of processing – high-performance machining (HPM). The distinctive features of HPM are the reduced (as compared with HSM) spindle rotational speed (cutting speed) and the increased volumes of removed material (the depth and width of cutting). The goal of the research is the study of feasibility to apply HPM for cutting of structural steel using undedicated CNC machines widely used for traditional milling. When preparing and carrying out the research, the author took into account the mechanical properties of process material; MDTP (machine-device-tool-part) system stiffness; machine technical data; material, coating, and geometry of a cutting tool. The temperature in the cutting area and the work material and cutting tool temperature were recorded as well. The study determined the following mandatory parameters of the process: smooth, tangentially costate trajectories of a tool; angle of cutter spiral; cutter engagement angle. The calculation of cutting time and cutting specific volume showed the advantage of HPM as compared to the traditional CNC milling. The process parameters having a positive impact on tool wear are determined and the parameters constraining the process of HPM implementation are considered.

Block-Modular Principle of Build Composition Automatically Changeable Laser Modules for CNC Machines

The article is devoted to the development of plug-in modules for automatically implementing the standard technology of laser processing of materials on CNC machines using the element base of fiber lasers. The technical solution of the device in the form of an independent unit, composed of a single block, the parameters of each of which are determined by the production requirements, is suggested. This module is working machining cycles set in the tool magazine of the machine. In the operating mode, the module is installed in the machine spindle automatically command the control system, and a laser light source placed outside the working area of the machine. The proposed solution does not require purchasing a laser processing facility as part of ensuring the implementation of the technology of the desired product, while achieving high performance and precision machining, no additional transport items, reduced loss of time to process all the details. The paper presents the methodology of rearranging devices for laser treatment and the basics of the principle of modular build composition are suggested. The basis of this principle is the kinematic analysis devices, allowing, based on production requirements, determining the final version of the set of its constituent blocks. Using the proposed methodology it is shown that the options of the devices construction can be analyzed both at the stage of analysis and modernization of existing designs, and at the stage of development of advanced technological proposals.

Friction Coefficients on Surface Finish of AlTiN Coated Tools in the Milling of Ti6Al4V

The main constraints in high performance machining of the titanium alloys are mostly due to the friction induced thermal issues. In thermal analysis, the friction coefficient is the critical parameter for estimating the heat generation at the tool-chip interface. This paper provides a direct approach for determining the friction coefficient from slot milling of Ti6Al4V for uncoated solid carbide end-mills and AlTiN coated tools with magnetic, friction and sandblast finishing techniques. The effects of AlTiN coating and finishing techniques on friction coefficients are investigated.

The high-performance machining of the curved surfaces with the progressive cutting geometry of the end mill

There are some results of practical application of the solid carbide end mill developed in HALTEC Ltd company, using for high-performance machining of curved surfaces of workpieces, which have a complex spatial form. It’s shown how to get high-performance machining of curved surfaces with a multidirectional curvature in heat-treatable and high strength Ti alloy Ti-6Al-2Sn-2Zr-2Mo-2Cr-0.15Si [Ti-6-22-22]. The real experience of the implementation of proposed end mill in the technological process of compressor blade machining is described.

Современные тенденции применения смазочно-охлаждающих технологических средств при лезвийной обработке труднообрабатываемых материалов

Современные тенденции применения смазочно-охлаждающих технологических средств при лезвийной обработке труднообрабатываемых материалов