Tool Displacement Research Articles

Enhancement and analysis of multidimensional characteristic diagrams for correction of TCP-displacements caused by thermal tool displacement

In the present paper former developed characteristic diagram approaches for the correction of thermo-elastic TCP-displacements during cutting processes are extended. Input variables linked with the resulting deformations are estimated by Design of Experiments (DoE). Deformations are computed by means of FEA via the estimation of heat fluxes in the system workpiece – chip – tool – clamping device and the temperature field in tool and clamping device. Multidimensional characteristic diagrams are derived to enable real-time correction of tool paths within the machine tool control. These correction approaches are of crucial importance especially in the field of precision machining and difficult-to-cut material generating large heat amounts. With the obtained correction values the effect of the different cutting parameters on the TCP-displacement is investigated in a sensitivity analysis.

The Effect of Torsional Vibrations on Metal Cutting Dynamics

The effect of torsional vibrations on the dynamics of metal cutting processes is studied. An extended dynamic process model is presented, where the spindle angle and the time delay are dynamic variables resulting in delay differential equations with state-dependent delay. Stability lobes are calculated based on the new extended process model and compared with results from the classical chatter theory with constant spindle speed and delay. For an ideal symmetric tool, stable cutting is characterized by a periodic spindle speed but still a constant delay. In this case, the main difference between the new extended and the classical model is a different periodic solution to periodic torsional tool displacements, which results only in slight modifications of the stability lobes. However, the new theory shows that it is important to consider tool asymmetries (e.g. runout), because this would result in periodically varying delays during stable cutting and larger stability changes due to torsional vibrations.

Analysis of vibration signals to quantify displacement amplitude in the monitoring of vibration-assisted turning

Vibration-assisted machining combines precision machining with small-amplitude tool vibration at high frequency to improve the fabrication process. It has been applied to a number of processes from turning to drilling to grinding. This work presents the validation of tool condition monitoring system based on vibration parameters. For this purpose, an experimental investigation is planned to acquire vibration signal data during the machining. This work primarily focuses on quantifying the presence of relative vibrations between the cutting tool and a workpiece during vibration-assisted turning process which helps in predicting tool life. For this purpose, an online acoustic optic emission-based vibration transducer, i.e. Laser Doppler Vibrometer, is used as a component of a novel approach. Cutting force and vibration signals were recorded and analyzed. Machine dynamic effects such as cutting force and tool wear are taken into account during the dry machining of Ti-6Al-4V alloys specimens. Identifying the correlation among tool wear, cutting forces and displacement due to vibration is a critical task in the present study. Real-time experimental findings are used to predict the evolution of displacement and tool wear in the experiment. Efficacy of a logical relationship among the process variables such as displacement, feed rate, spindle rotational speed, and depth of cut is critically examined. Results of the present study are used to establish a strategy for real-time efficient tool monitoring systems for vibration-assisted turning operation. The wear mechanisms of DNMA 432 coated carbide and uncoated carbide insert tools were examined at different combinations of feed rate, spindle speed, and depth of cut for turning of Ti-6Al-4V workpiece material.

3D analysis of surface topography in vibratory turning

High quality of machined surfaces is an important requirement in production industries. Therefore, different methods such as ultrasonic vibrations are implemented to improve this parameter. In this study, it is tried to specify some of effective parameters on surface improvement in ultrasonic-assisted turning. Accordingly, a series of experiments in the way of conventional and vibratory turning are conducted where surface roughness and surface topography are evaluated as main objectives of this work. Furthermore, analysis of tool wear and radial displacement of tool and workpiece are carried out for explanation of surface enhancement in vibratory turning. As a result, it is shown that generated typical peaks and valleys in conventional turning are flattened and reduced in vibratory turning which is explained by existence of lower radial force.

Simulation of Cold Extrusion of Hollow Parts

The finite-element method is used to study the effect of the design parameters of the die on the production of hollow brass parts by cold direct extrusion and expansion on a cone punch. The results are compared with data on conventional indirect extrusion. The elastic deformation and increase in the temperature of the metal during cold extrusion are taken into account. Intermediate and final shapes and dimensions of workpieces are determined by simulation. The dependence of the extrusion force on the tool displacement and the distribution of normal stress over the tool–workpiece contact surface under the maximum force is established. The stress-strain state of the workpiece during extrusion is determined. The distribution of stress intensity, strain intensity, and temperature over the deformed workpiece at the final stage of extrusion is plotted. Rational design parameters of a die for direct extrusion and expansion are proposed.

Online compensation of force-induced deformation for high-precision riveting machine based on force–displacement data analysis

Press working causes structural deformation of the machine tool, especially the machine tool with large-span gantry or double columns used for the large-sized workpiece. The structural deformation makes the press tool out of accurate positioning, which leads to dimension deviation of the pressed workpiece. Even more, for thin-walled panel riveting, the structural deformation of the riveting machine will cause local deformations of the panel at rivet joints; this accumulated deformation will make the panel out of tolerance. An online deformation measurement and compensation method is developed for adaptive riveting with high accuracy and efficiency in this paper. During the process of servo driving riveting combined with force measurement, the force–displacement data points can be online obtained, and the recognized feature data points by a robust algorithm can represent the critical points during rivet deformation. Combined with the analytical springback of the rivet joint, the deformation of the machine tool can be accurately solved and compensated to the displacement of press tool for high­precision riveting. Simultaneously, with this innovative measurement method, the online quantity inspection for rivet joints can be realized synchronously. Also, a contrast experiment is conducted to validate the effectiveness of the online adaptive deformation compensation based on force–displacement data analysis. The results demonstrate the feasibility of the proposed method in riveting error compensation and riveting quantity inspection.

Reduction of tool wear by systematic design of the tool clamping situation

As a result of the cutting impact, shear cutting processes initiate intensive vibrations in cutting presses and tools. With the aim to improve the press accuracy and tool lifetime, damping systems for reducing the press vibration are state of the art. However, only small attention is given to the tool vibration. Due to its mounting condition in a high-speed press, the lower tool can vibrate like a bending plate. The amplitude of the tool displacement depends on the clamping situation of the plate edges. Moreover, the displacement amplitude correlates with the tool wear. Against this background, it is possible to reduce the wear of a shear cutting tool by systematic design of its clamping situation. In this paper, a methodology for modelling the dynamic behavior of the tool is given. This approach allows a systematic design of the tool clamping situation with the objective to minimize the vibration and thereby the tool wear. Furthermore, the effect of the clamping situation on different process and tool parameters is given by experimental investigations.

Improving FEM model of low immersion milling process using multi-objective optimization of tool elastic support dynamic properties

The accurate prediction of tool displacement on elastic support is always considered a crucial problem in metal cutting process simulation. Static and dynamic properties of a machine tool structure which are the function of boundary conditions of a tool-tool holder, modal parameters of an end mill, and interface of cutting edge with a workpiece can affect the displacement of the end mill. In this paper, the receptance coupling substructure analysis (RCSA) and multi-objective optimization algorithm, NSGA-II, are combined to determine the elastic support properties. The investigated effective parameters include the tool-tool holder contact length, clamping torque, and the tool length ratio to diameter. In order to evaluate the accuracy of results and simulate the low immersion end milling process, a novel FEM model is created in which the constant stiffness and damping have a linear relationship along the elastic support. The frequency response function-obtained FEM models have good accordance with experimental data. Using this model and linking the FEM model with MATLAB software, cutting forces and tool displacements are simulated. The accuracy of the suggested method is evaluated by simulating two case studies based on different cutting conditions. Comparison between simulation and experimental results indicates that the suggested model can precisely predict the cutting force and tool displacement. The proposed model can be used to simulate the milling processes for various tool boundary conditions in forced and free vibration states, and the consumed time for simulation of process is significantly reduced.

Attractive manifolds in end milling

The attractive manifolds formed in end milling are analyzed. Such states are formed if the trajectories of steady periodic deformational tool displacements are unstable overall or in individual sections. In the dynamic milling system, attractive manifolds in the form of limit cycles, invariant tori, and strange (chaotic) attractors may appear. Bifurcations of attractive manifolds in parameter space are analyzed at length, with examples. Interest centers on how attractive manifolds affect manufacturing quality.

Влияние биений шпиндельной группы на притягивающие множества деформационных смещений инструмента при точении

Влияние биений шпиндельной группы на притягивающие множества деформационных смещений инструмента при точении

The analysis of instantaneous tool displacements during precise ball end milling

The paper presents the quantitative and qualitative analysis of monolithic ball end mill’s instantaneous displacements generated during precise milling of inclined surfaces. The conducted experiment involves the measurements of tool’s joining part displacements with the application of laser displacement sensor and cutting forces with piezoelectric dynamometer. The milling tests were carried out for the hardened alloy 55NiCrMoV6 steel in a range of variable feed per tooth and surface inclination angle values. The obtained results can be applied for the selection of effective milling parameters allowing the improvement of machined surface finish.

Two degree of freedom frequency domain surface location error prediction

This paper presents a two degree of freedom (DOF) closed-form frequency domain solution for surface location error prediction, including both the tool and workpiece flexibility. The cycloidal tool path is incorporated in the solution and the machined surface geometry is described by combining the tool path with the tool and workpiece displacements in two directions. For prediction validation, a two DOF flexure stage with tunable dynamics was constructed and milling tests were performed over a range of spindle speeds. Time domain simulations were also completed and a comparison between the closed-form frequency domain surface location error predictions, time domain predictions, and experimental results is provided.

Plunge milling time optimization via mixed-integer nonlinear programming

Plunge milling is a recent and efficient production mean for machining deep workpieces, notably in aeronautics. This paper focuses on the minimization of the machining time by optimizing the values of the cutting parameters. Currently, neither Computer-Aided Manufacturing (CAM) software nor standard approaches take into account the tool path geometry and the control laws driving the tool displacements to propose optimal cutting parameter values, despite their significant impact. This paper contributes to plunge milling optimization through a Mixed-Integer NonLinear Programming (MINLP) approach, which enables us to determine optimal cutting parameter values that evolve along the tool path. It involves both continuous (cutting speed, feed per tooth) and, in contrast with standard approaches, integer (number of plunges) optimization variables, as well as nonlinear constraints. These constraints are related to the Computer Numerical Control (CNC) machine tool and to the cutting tool, taking into account the control laws. Computational results, validated on CNC machines and on representative test cases of engine housing, show that our methodology outperforms standard industrial engineering know-how approaches by up to 55% in terms of machining time.

Experimental Investigation to Predict Tool Wear and Vibration Displacement in Turning – A Base for Tool Condition Monitoring

AbstractIn the present work investigation primarily focuses on identifying the presence of cutting tool vibrations during face turning process. For this purpose an online non-contact vibration transducer i. e. laser Doppler Vibrometer is used as part of a novel approach. The revisions in the values of cutting forces, vibrations and acoustic optic emission signals with cutting tool wear are recorded and analyzed. This paper presents a mathematical model in an attempt to understand tool lifeunder vibratory cutting conditions. Tool wear and cutting force data are collected in the dry machiningof AISI 1040 steel at different vibrationinduced test conditions. Identifying the correlation among tool wear, cutting forces and displacement due to vibration is a critical task in the present study. These results are used to predict the evolution of displacement and tool wear in the experiment. Specifically, the research tasks include: to provide an appropriate experimental data to prove the mathematical model of tool wear based on the influence of cutting tool vibrations in turning.The modeling is focused on demonstrating the scientific relationship between the process variables such as vibration displacement, vibration amplitude, feedrate, depth of cut and spindle speed while getting into account machine dynamics effect and the effects such as surface roughness and tool wear generated in the operation. Present work also concentrates on the improvement in machinability during vibration assisted turning with different cutting tools. The effect of work piece displacement due to vibration on the tool wear is critically analyzed. Finally, tool wear is established on the basis of the maximum displacement that can be tolerated in a process for an effective tool condition monitoring system.

Synergetic approach to study forming path stability of the end cutdown milling by side faces (case of high speed cutting)

The work objective is to consider the stability problem of steady-state paths of the elastic deformational tool displacement under the longitudinal end milling. The authors analyze the case of high speed cutting in contrast to the previously discussed stability problems that analyze the case of slow movements for which the system parameters can be considered frozen in the equations in variations relative to the stationary path. In this case, the stability analysis must consider the linearized system in variations with periodically varying coefficients. With speeding-up the tool rotation in many cases there is a parametric self-excitation of oscillations. Therefore, the main attention is paid to studying the parametric excitation conditions of a dynamic endmilling system. It is shown that the parametric excitation condition is affected by the technological cutting modes, both the tool rotation frequency and the tool geometry which determines the matrix angular coefficients of the cutting forces orientation. Examples of stability areas depending on changes in the system settings are given.

Precision surface characterization for finish cylindrical milling with dynamic tool displacements model

In this work a new approach to surface roughness parameters estimation during finish cylindrical end milling is presented. The proposed model includes the influence of cutting parameters, the tool’s static run out and dynamic phenomena related to instantaneous tool deflections. The modeling procedure consists of two parts. In the first stage, tool working part instantaneous displacements are estimated using an analytical model which considers tool dynamic deflections and static errors of the machine – tool-holder – tool system. The obtained height of the tool’s displacement envelope is then applied in the second stage to the calculation of surface roughness parameters. These calculations assume that in the cylindrical milling process, two different mechanisms of surface profile formation exist. Which mechanism is present is dependent on the feed per tooth and the maximum height of the tool’s displacement envelope. The developed model is validated during cylindrical milling of hardened hot-work tool steel 55NiCrMoV6 using a stylus profiler and scanning laser vibrometer over a range of cutting parameters. The surface roughness values predicted by the developed model are in good agreement with measured values. It is found that the employment of a model which includes only the effect of static displacements gives an inferior estimation of surface roughness compared to the model incorporating dynamic tool deflections.

Effects of Process Parameters on White Layer Formation and Morphology in Hard Turning of AISI52100 Steel

Hard turning is becoming increasingly considered by industry as a potential substitute for grinding. However, it is greatly hurdled by surface integrity problems such as tensile residual stress and white layer, which are generally found to have negative effects on the stress corrosion, wear resistance, and fatigue life of the machined parts. This paper investigates white layer formation and morphology in hard turning process using various process parameters, taking into account the effects of heat treatment which results in microstructure and hardness differences on bulk materials. Samples undergone three typical heat treatment processes are prepared and then machined using different cutting speeds and radial feed rates. Optical microscope, scanning electron microscope (SEM), and X-ray diffraction (XRD) are employed to analyze the microstructures of white layer and bulk materials after varies heat treatments and cutting processes. Through the studies, we find the existence of a cutting speed threshold, below which no white layer forms for both the low and medium-temperature tempering. The threshold value increases; however, the white layer thickness decreases under the same cutting conditions, for the low and medium-temperature tempering, respectively. Also, we find that the white layer thickness and the scattering of it along the cutting direction on the surface increases with cutting speed and radial feed rate. White layer with wavy morphology can be found in samples after quenching at high cutting speed. We first discover that the pitch of the white layer with wavy morphology is similar to the displacement of tool at the time a segment of the serrated chips forms. Also, the surface residual stresses of the samples are measured. Relationship between white layer and residual stresses is presented. Based on the relationship we reveal that high temperature is more dominant than volume expansion for white layer formation.

Investigation on Direction Dependency of Tool-Workpiece Compliance of Machine Tool

The direction dependency of tool-workpiece compliance of machine tool was investigated in three dimensions. The tool-workpiece compliance is defined as the frequency response of the relative displacement between the tool and the workpiece to the cutting force. The tool-workpiece compliance of a vertical type machining center was measured. The direction dependency of the compliance magnitude was discussed using the polar plot. The compliance in the Z (vertical) direction was smaller than that in the XY (horizontal) directions. The maximum value of the compliance in the X direction was almost twice as large as those in the Y and Z directions. The influence of the frequency on the direction dependency was also discussed. The direction dependency in the XY plane was small in the frequency range higher than 250Hz. This can be explained by the symmetry of the spindle about the X and Y directions because the tool-workpiece relative displacement was dominated by the tool displacement in the high frequency range.

Measurement of thermal influence on a two-dimensional motion trajectory using a tracking interferometer

Conventional thermal deformation tests in ISO 230-3:2007 only measure the tool displacement when it is positioned at a single point. This paper proposes the application of a tracking interferometer to the evaluation of the thermal influence on two-dimensional motion trajectory. The full multilateration algorithm requires at least four tests repeated at different tracking interferometer positions, when only one tracking interferometer is available. This paper proposes the identification of 2D geometric errors of linear axes by single-setup tests. Since the measurement time is significantly reduced, it can be applied within a thermal test. The uncertainty analysis is also presented.

Analysis of Lead-Free Piezoceramic-Based Power Ultrasonic Transducers for Wire Bonding.

Since the 1950s, lead zirconate-titanate (PZT) has been the dominant transduction material utilized in power ultrasonics, while lead-free piezoceramics have been largely neglected due to their relatively poor piezoelectric and electromechanical properties. However, the implementation of environmental directives that regulate and control the use of hazardous materials, such as lead, triggered a search for new high-performance lead-free piezoceramics. Recent advances have led to lead-free piezoceramics exhibiting properties similar to PZT, but despite this, reports utilizing these novel piezoceramics in practice are limited. This research employs a modified variant of bismuth sodium titanate (BNT) in a power ultrasonic transducer used for metal welding during the manufacture of semiconductors. The important factors for transducer reliability and performance are investigated, such as piezoceramic aging and stack preload level. It is reported that BNT-based transducers exhibit good stability, and can withstand a stack preload level of 90 MPa without depoling. Although the BNT-based transducers exhibited larger dissipative losses compared to identical PZT8-based transducers, the tool displacement gain was larger under constant current conditions. Semiconductor wire bonds which satisfied the commercial quality control requirements were also formed by this BNT-based transducer.