Vibration Of Boring Bar Research Articles

Research on Intelligent Monitoring of Boring Bar Vibration State Based on Shuffle-BiLSTM.

Due to its low stiffness, the boring bar used in deep-hole-boring is prone to violent vibration during the cutting process. It is often inaccurate and inefficient to judge the vibration state of the boring bar through artificial experience. To detect the change of the vibration state of the boring bar over time, guide the adjustment of the processing parameters, and avoid wastage of the workpiece and the loss of equipment, it is particularly important to intelligently monitor the vibration state of the boring bar during processing. In this paper, the boring bar is taken as the research object, and an intelligent monitoring technology of the boring bar's vibration state based on deep learning is proposed. Based on grouping convolution, channel shuffle, and BiLSTM, a shuffle-BiLSTM NET model is constructed, which is both lightweight and has a high classification accuracy. The boring experiment platform is built, and 192 groups of cutting experiments are carried out. The three-way acceleration and sound pressure signals are collected, and the signals are processed by smoothed pseudo-Wigner-Ville distribution. The original signals are transformed into a 256 × 256 × 3 matrix obtained by a two-dimensional time-frequency spectrum diagram. The matrix is input into the model to recognize the boring bar's vibration state. The final classification accuracy is 91.2%. A variety of typical deep learning models are introduced for performance comparison, which proves the superiority of the models and methods used in this paper.

Nonlinear Dynamical Analysis of Composite Boring Bar with Nano-carbon Materials

Preventing resonance in boring bar vibration is the key to achieve high quality and efficiency. In this paper, using the three-dimensional nonlinear dynamic model of boring process, the cutter bar is simplified as a rotating non planar bending axis, starting from the constitutive relationship and stress displacement relationship of composite materials. Based on Hamilton principle, the nonlinear motion differential equation of cutting process is established. The nonlinear partial differential equations of bending vibration are discretized by Galerkin method. Using the multi-scale method, the frequency response functions of the system in the primary resonance and super resonance are obtained. Using this model, the effects of the length diameter ratio of nano-carbon materials and the content of nano-carbon materials on the vibration frequency response of the boring bar are studied. The results show that the steady vibration amplitude of the cutter bar can be reduced by adding nano-carbon materials to the fiber reinforced polymer composite (FRP) beam.

Modeling and analysis of boring bar vibration response in internal turning due to variation of the amount of DVA rubber in finish boring cut

Modeling and analysis of boring bar vibration response in internal turning due to variation of the amount of DVA rubber in finish boring cut

Vibration control in boring process using a constrained viscoelastic layer damper

A passive vibration control method is adopted to control vibrations of a boring bar. A viscoelastic layer sandwiched between main steel boring bar and aluminium tube, known to be constrained viscoelastic layer damper (CVLD), is designed and developed in order to reduce the vibration produced during the machining operations. The low density aluminium tube and natural rubber as viscoelastic layer are used in the boring bar to increase its natural frequency and damping property respectively. The finite element simulation of boring bar with and without CVLD are carried out using ANSYS and the results are used to develop a model to predict the influence of thickness of viscoelastic layer and aluminium tube on natural frequency of boring bar using full factorial design of experiments (DOE) and regression analysis. The DOE and regression analysis, carried using Minitab package, provides optimum thickness of viscoelastic layer and aluminium tube. These optimum thickness values are used to fabricate CVLD and its effectiveness to control boring bar vibration is tested by conducting machining experiments. The surface roughness of the machined components is also measured and the results show that the boring bar with CVLD is more efficient than conventional boring bar in controlling vibrations during machining. Moreover, stability lobes, which are plots of spindle speed vs. depth of cut of a machining process, are also constructed. Stability lobes indicate that the machining stability may be improved by 15 % by using boring bar with CVLD.

Improvement of chatter stability in boring operations with semi active magneto-rheological fluid damper

Boring is a machining process, which is used to enhance the size of a pre drilled hole. In boring operation the tool vibration is an unmanageable part of the machining process. This affects the tool life and surface finish of the workpiece. When the magneto rheological fluid subjected to an external magnetic field, which changes the stiffness and undergoes a phase transformation. The stiffness and energy dissipation properties of the MR fluid controlled boring bar can be adjusted by varying the strength of the applied magnetic field. In this paper, semi active radially arranged magneto rheological fluid dampers were adopted to suppress the boring bar vibration. Experiments were conducted for different spindle speeds with the HSS boring bar tool on a mild steel workpiece. Vibrational characteristics based on surface roughness and chatter reduction were studied. The experimental result shows that, tool chatter was reduced ineffectiveness with the use of radial arrangement of dampers.

Active damping of machine tool vibrations and cutting force measurement with a magnetic actuator

This paper presents a novel multifunctional magnetic actuator, which not only damp the vibration of machine tools but also measure the cutting force in real time. The actuator is composed of four identical electromagnetic units which are linearized with a novel design strategy. The magnetic force can be delivered in two radial directions for active damping of the flexible structures in the machine tools. Cutting force is estimated from the armature displacement and the control current of the actuator. The performance of both active damping and cutting force measurement are demonstrated on a boring bar which is clamped to the turret of a CNC lathe. Experimental results show that the boring bar vibration is damped significantly with a velocity feedback controller, resulting in a higher chatter-free depth of cut, while the measured cutting force from the actuator agrees with the reference force quite well.

Active Damping of Boring Bar Vibration With a Magnetic Actuator

Boring bars with a large length-to-diameter ratio chatter under productive cutting conditions, which leads to poor surface finish and violation of part tolerances. This paper presents an active damping method of boring bars with an in-house designed magnetic actuator. The actuator has been designed to have a linear force output relative to the input current, and instrumented to control boring bar vibrations. Four different H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> optimal controllers are designed to shape the boring bar dynamics and improve the chatter stability. The proposed active damping method is experimentally tested on a CNC lathe. The dynamic stiffness of the boring bar is increased considerably, leading to a significant increase in the chatter-free material removal rates.

Semiactive Magnetorheological Damper for High Aspect Ratio Boring Process

This paper aims to develop a new semiactive damper to attenuate chatter vibration of a high aspect ratio boring bar. Design of the damper utilizes magnetorheological (MR) fluid and an electromagnet to control a damping force by a current input during machining process so as to effectively attenuate the chatter vibration. Various aspects of research on MR fluid and dynamic characteristics of boring operation and the MR damper have been investigated; First of all, effectiveness of MR fluid on attenuating vibration has been investigated by various designs of the damper and magnetic field. Then, the behavior of the MR fluid is simulated and its result is utilized to estimate dynamic motion of the MR actuator. Furthermore, simulation of the boring tool, force, and stability model shows significant improvement in machine chatter particularly for a high aspect ratio boring bar. The results provide a fundamental understanding to estimate dynamic vibration of the boring bar and offers optimal conditions for effectively attenuating chatter vibration. Finally, various experiments have been demonstrated to identify parameters of the MR damper and the results of boring machining show damper attenuation capability for wide frequency band by various cutting conditions corresponding to chatter frequencies.

A novel magnetic actuator design for active damping of machining tools

Parts and cutting tools with large structural flexibility experience both forced and chatter vibrations during machining, resulting in poor surface finish or damage to the machine. This paper presents the design principles of a novel 3 degrees of freedom linear magnetic actuator which increases the damping and static stiffness of flexible structures during machining. The proposed actuator can deliver 248N force in two radial (x, y) directions and 34N×m (torque) in torsional (θ) direction up to 850Hz. The force and torque reduces to 107N and 14.5N×m at 2000Hz, hence it can actively damp a wide range of structural modes. The magnetic force is linearized with respect to the input current using magnetic configuration design strategy. Loop shaping controllers are designed for active damping of boring bar vibrations. The static and dynamic stiffnesses of the boring bar were considerably increased with the designed actuator, leading to a significant increase in chatter-free material removal rates during cutting tests.

Prediction of cutting tool wear, surface roughness and vibration of work piece in boring of AISI 316 steel with artificial neural network

Machining of stainless steel is difficult due to their hardening tendency. In boring of stainless steels, tool wear and surface roughness are affected by vibration of boring bar. In this paper, tool wear, surface roughness and vibration of work piece were studied in boring of AISI 316 steel with cemented carbide tool inserts. A Laser Doppler Vibrometer was used for online data acquisition of work piece vibration and a high-speed Fast Fourier Transform analyzer was used to process the acousto optic emission signals for the work piece vibration. Experimental data was collected and imported to artificial neural network techniques. A multilayer perceptron model was used with back-propagation algorithm using the input parameters of nose radius, cutting speed, feed and volume of material removed. The artificial neural network was used to predict surface roughness, tool wear and amplitude of work piece vibration. The predicted values were compared with the collected experimental data and percentage error was computed.

Study on Spring Rubber Parameter Optimization in Damping Boring Bar

Passive dynamic damping system in damping boring bar is made of rubber, damping blocks and damping liquid. These parameters ,which including the elasticity of the spring rubber, the mass of the damping blocks and the characteristic of the damping liquid, will have influence on damping property. This paper mainly studies the influence of spring rubber parameter on damping property. Frequency response curve of spring rubber can be got by simulation, spring rubber static analysis by ANSYS and damping boring bar vibration simulation by ADAMS. After verification by simulation, the model and resolving method of parameters can provide theoretical basis of actual application and design.

Suppressing boring bar vibrations by parametric excitation

Machine tool chatter causes an instability that can occur in tool-workpiece-machine system. Hence surface roughness and tool wear in metal cutting processes. This instability caused by interaction between current tool positions and surface left by previous tool passes. Many methods have been developed to minimize the effects of regenerative chatter in machine tools and to enhance the damping capability minimizing the loss in static stiffness through implementation of device uses PZT actuators or MR fluid. The possibility of suppressing selfexcited vibrations of boring process using parametric excitation is discussed. We consider a two-mass system of which the main mass is excited by a self excited force (cutting force). A single mass which acts as a dynamic absorber is attached to the main mass and, by varying the stiffness between the main mass and the absorber mass, represents a parametric excitation. Cutting experiments with an excitation current of different waveforms and diverse frequencies show that chatter can be significantly suppressed by the effect of parametric excitation.

基于经验模态分解和希尔伯特-黄变换的精密孔镗削颤振特征提取

For the chatter occured frequently in precise hole boring processing and resulted in low quality of finished surface,a chatter monitoring system was established to finish the feature extraction of the chatter to predict the chatter and gain the precious time for chatter suppression.Firstly,according to the characteristics of chatter signals,Empirical Mode Decomposition(EMD) and Hilbert-Huang Transform(HHT) were introduced to extract the chatter feature,and their basic theories were investigated.Then,the vibration of boring bar was picked up online during the process,and the vibration signal was decomposed by EMD and then transformed by HHT.Finally,the feature of chatter symptom was extracted by analyzing the Hilbert spectrum of each Intrinsic Mode Function(IMF).The experimental results show that extracting chatter feature from vibration of boring bar by EMD and HHT can gain the chatter symptom by 0.5 s ahead of the chatter outbreak,which can provide sufficient guarantee for follow-up chatter suppression and can provide the high quality surface for workpieces.

An Effective EMD-Based Feature Extraction Method for Boring Chatter Recognition

Chatter often occurs during precision hole boring, it results in low quality of finished surface and even damages the cutting tool. In order to identify chatter rapidly and gain the precious time for chatter suppression, a chatter monitoring system was established and an effective feature extraction method for boring chatter recognition was presented. According to the characteristic of chatter signal, empirical mode decomposition (EMD) was introduced into chatter feature extraction, and its basic theories were investigated. The vibration signal was decomposed by EMD, then the intrinsic mode functions (IMF) was got. Finally, the feature of chatter symptom was extracted by analyzing the energy spectrum of each IMF. The results show that feature extracted from vibration of boring bar by EMD can indicate chatter outbreak symptom, and it can be used as feature vectors for rapidly recognizing chatter.

Dynamic Modeling of a Boring Bar Using Theoretical and Experimental Engineering Methods Part 1: Distributed-Parameter System Modeling and Experimental Modal Analysis

Boring bar vibration is a common problem during internal turning operations and is a major problem for the manufacturing industry. High levels of boring bar vibration generally occur at frequencies related to the first two fundamental bending modes of a boring bar. This is the first of two companion papers that summarize the theoretical and experimental work carried out concerning modeling of dynamic properties of boring bars. This paper introduces the Timoshenko beam theory for the modeling of clamped boring bars. Also, the traditional Euler-Bernoulli beam theory is applied. These continuous system methods have been utilized to produce fixed-free beam models of the clamped boring bar. In order to improve accuracy of dynamic models of clamped boring bars, the modeling of the boring bar clamping is addressed by means of multi-span beam models with pinned boundary conditions. The derived boring bar models have also been compared with results obtained by means of experimental modal analysis, conducted on the actual boring bar clamped in a lathe. The multi-span beam boring bar models display higher correlation with experimental modal analysis results as compared to fixed-free beam models. For the fixed-free beams the Timoshenko model results in the highest correlation with the experimental results. On the other hand, the interval in frequency and the orientation of the two fundamental modes demonstrate differences, particularly between the continuous system models and the experimental results.

On the Development of a Simple and Robust Active Control System for Boring Bar Vibration in Industry

Vibration in internal turning is a problem in the manufacturing industry. A digital adaptive controller for the active control of boring bar vibration may not be a suficient solution to the problem. The inherent delay in a digital adaptive controller delays control authority and may result in tool failure when the load applied by the workpiece on the tool changes abruptly, e.g. in the engagement phase of the cutting edge. A robust analog controller, based on a lead-lag compensator, with simple adjustable gain and phase, suitable for the industry application, has been developed. Also, the basic principle of an active boring bar with embedded actuator is addressed. The performance and robustness of the developed controller has been investigated and compared with an adaptive digital controller based on the feedback filtered-x algorithm. In addition, this paper takes into account those variations in boring bar dynamics which are likely to occur in industry; for example, when the boring bars is clamped in a lathe. Both the analog and the digital controller manage to reduce the boring bar vibration level by up to approximately 50 dB.

Identification of dynamic properties of boring bar vibrations in a continuous boring operation

Vibrations in internal turning operations are usually a cumbersome part of the manufacturing process. This article focuses on the boring bar vibrations. Boring bar vibrations in alloyed steel, stainless steel and cast iron have been measured in both the cutting speed direction and the cutting depth direction with the aid of accelerometers. The dynamic response of a boring bar seem to be a time varying process that exhibits non-linear behaviour. The process is influenced by non-stationary parameters that are not under the control of the operator or experimenter. The vibrations are clearly dominated by the first resonance frequency in one of the two directions of the boring bar. The problem with force modulation in rotary machinery, which appears as side band terms in the spectrum, is also addressed. Furthermore, the resonance frequencies of the boring bar are correlated to an Euler–Bernoulli beam model.

Vibration damping systems using active negative capacitance shunt circuit with piezoelectric reaction mass actuator

Boring bar vibration damping is improved by a novel use of the electromechanical properties of the piezoelectric actuator material. A negative capacitance shunt circuit is provided in which a voltage-controlled voltage-source continuously simulates a negative capacitance that is substantially equal in magnitude but opposite in phase to the capacitance of the piezoelectric material. The negative capacitance is shunted across the piezoelectric device, effectively compensating for the capacitance of the device across a broad frequency band. The voltages generated in the piezoelectric element in response to mechanical deformation induced by broadband vibrations of the structure during damping operations, may then be completely resistively dissipated, thereby enhancing the mechanical damping.

Effect of the stiffness characteristics of the stuffing box on boring bar vibrations

This paper presents a study on the effect of the stuffing graphite sealant between the pressure head and the boring bar, on the dynamic response of the bar-tool assembly. The study was done using the experimental approach to determine the natural frequency distribution of the boring bar-tool assembly first, and then employing the modal analysis approach to determine the overall stiffness of the stuffing graphite sealant. Two end-conditions, namely the cutting edge side and the clamped side of the boring bar were approximated based on the cutting mechanics and clamp rigidity, respectively. The variation in the first three natural bending frequencies of the continuous system with respect to the penetration of the boring bar tool assembly is given in order to establish stable operating conditions of the system.

High-frequency strain-gauge installation

The strain-gauge equipment developed by us is used for studying bending and twisting vibrations in small-diameter boring bars of diamond-cutting lathes. This equipment served for registering boring bar vibrations at a frequency of 12–15 kHz and a relative deformation amplitude of 10−5−10−6. It has been found that these oscillations lower the quality of the machined surface and increase considerably the wear of the cutting tool.