Suppression Of Chatter Vibration Research Articles

Special Issue on Advanced Metal Cutting Technologies

Cutting technologies are utilized in many industrial sectors, such as automobile, aircraft, and medical-device manufacturing as well as dies and molds. Thus, the requirements for higher geometric accuracy, better surface integrity, and longer component service lifetimes have substantially increased. In addition, maintaining high machining efficiency while simultaneously reducing power consumption and CO2 emissions during machining is important for sustainable development. This special issue features 11 papers on the most recent advances in cutting technologies for metals and composite materials. - Reverse finishing characteristics of drilling surfaces - Machining error simulation for end milling - Visualization of cutting phenomena using a single-crystal diamond tool - Milling of TiB2 particle-reinforced high-modulus steel - Electrodischarge-assisted turning of carbon fiber-reinforced polymers - Suppression of chatter vibration during double-insert turning - Prediction of surface roughness components during turning - Microtome blades for high-precision tissue sectioning - Boiling of coolant near the cutting edge in high-speed machining - Residual stress during drilling of aluminum alloy - Effect of strain hardening on burr control during drilling This issue provides an understanding of recent developments in cutting technologies, aiming to inspire further research in this field. We deeply appreciate the careful work of all the authors and thank the reviewers for their diligent efforts.

Inner Modulation Controlled Process for Suppression of Chatter Vibration in Double Inserts Turning

A novel cutting manner is presented to control regenerative chatter vibration in double inserts cutting, in which the forward and the backward inserts cut workpiece simultaneously with phase difference in the modulation of finished surface. In double inserts cutting, the forward insert is clamped above the backward insert. Both the inserts are positioned symmetrically with a height offset with respect to the workpiece rotation center. The forward insert mainly removes the material; while the backward insert cuts a part of the inner modulation to lose the regular excitation. The exciting force is also reduced with the cutting thickness of the forward insert after a workpiece revolution. Because the theoretical position offset of the inserts in the feed direction is small, the side cutting edges of inserts are aligned in the same position. The process parameters are determined by estimating the removal volume of the backward insert with the phase shift. The range of the cutting speed and the height offset are given by the frequency of the chatter vibration, which is nearly the same as the natural frequency of the workpiece in single degree of freedom. The proposed cutting manner is validated using comparison between the single insert and double inserts cuttings.

Special Issue on Abrasive Technology for High-Precision and High-Efficiency Machining of High-Performance Materials

The demand for high-precision and high-efficient machining of high-performance materials and components has increased in various industries such as optical, automotive, communication, life sciences, and medical sciences. Certain difficult-to-machine materials can be reliably machined using deterministic precision cutting processes. However, hard and brittle materials such as ceramics, carbides, hardened steel molds, glassy materials, or semiconductor materials, require precision abrasive technologies with super abrasives like diamond, cBN, or new tool materials for machining. However, machining high-precision components and their molds/dies using abrasive processes is considerably more difficult due to their complex and non-deterministic nature and textured surfaces. Furthermore, high-energy processes such as laser technology can assist abrasive technologies in ensuring higher precision and efficiency. Precision grinding and polishing processes are primarily used to generate high-quality and functional components, typically made of difficult-to-machine materials. Thus, the surface quality achievable by precision grinding and polishing processes becomes more important for reducing machining time and costs. This special issue features 10 papers on the most recent advances in precision abrasive technologies. These papers cover the following topics: - Ultrasonic grinding of micro holes using cemented WC tools - Drilling holes in CFRP aircraft using cBN electroplated ball end mill - In situ evaluation of drill wear using tool images - Grinding belt based on modified information entropy - Radial directional vibration-assisted grinding of Al2O3 ceramics - Chatter vibration suppression using fixed superabrasive polishing stone - Free abrasive finishing of internal channels with different cross-sectional geometries - High-quality machining of cemented carbide using PCD ball end mills - Fixed-abrasive machining with magnetic brush for Ti-6Al-4V ELI alloy - High-efficient polishing of polymer surfaces using catalyst-referred etching This issue will provide an understanding of the recent developments in abrasive technologies, leading to further research. We deeply appreciate the careful work of all the authors, and we thank the reviewers for their incisive efforts.

Study on Temporary Unloading for Chatter Vibration Suppression Using Fixed Superabrasive Polishing Stone with Five-Joint Closed-Link Small Robot and Voice Coil Motor Thrust Control

In this study, an existing superfinishing method used for polishing glass surfaces was refined using a five-joint closed-link compact robot with fixed abrasive grains. In previous studies, a voice coil motor was used to control the constant-pressure pressing force while maintaining the polishing force for a relatively short period. However, maintaining the polishing force for long periods is imperative for achieving a high-quality polished surface. Thus, in this study, a strain gauge load cell was adopted in addition to a conventional piezoelectric force sensor to maintain the polishing force for a long period. First, the amounts of DC drift of the piezoelectric force sensor and strain gauge type load cell were compared to confirm the necessity of signal processing as well as the compatibility of long-term force measurement and high-frequency vibration measurement by application. Further, a method was proposed in which the change in the pressing force was recorded from the connected sensor; when the pressing force fluctuated, chatter vibrations were determined to occur, and the pressing force was temporarily set to 0 N. This method could obtain a better polished surface than the proportional-integral-differential (PID) control, which simply controls the pressing force at a constant value. Finally, chatter vibrations could be determined by detecting high-frequency sounds using a sound level meter. Notably, a finely polished surface could be obtained.

A Study on Chatter Vibration Suppression by Bringing a Damping Beam into Contact with Workpiece

A Study on Chatter Vibration Suppression by Bringing a Damping Beam into Contact with Workpiece

A Study on Bistability Analysis and Chatter Suppression for Roll Grinding Process

ABSTRACT As chatter vibration in roll grinding process is the largest limitation in surface quality of machined roll. In this paper, the bistability analysis and chatter suppression are performed for further discussion of patterns of the grinding chatter to reduce the cost of enterprises. A new three degrees of freedom dynamic model with both the regenerative effect and nonlinear stiffness of grindstone indicated by Duffing oscillator is presented, and its availability is validated by the experiment. By means of the DDE-BIFTOOL, a numerical calculation package, the effect of process parameters on grinding stability is studied extensively, proving that a large grinding width worsens the stability in roll grinding and the parameters locating in unsafe areas should be avoided for a stable grinding operation in practice. In addition, the control techniques involving both the nonlinear velocity feedback and the chaos perturbation are proposed for the suppression of chatter vibration in grinding operation to decrease the amplitude of its vibration. The results show that these techniques give a significant performance for reducing the amplitude of chatter vibration, namely, the stability of grinding process is augmented, which give a new idea for firms in chatter suppression.

Influence of flank texture patterns on the suppression of chatter vibration and flank adhesion in turning operations

In this paper, we propose a practical texture design on the tool flank face for suppressing chatter vibration and flank adhesion. To avoid chatter vibration during cutting, the process damping phenomena can be utilized, where the tool flank face contacts the surface of a finished workpiece to provide a damping effect. As a new technology for an effective process damping, the tool flank texture-assisted technique has been proposed, and its excellent performance in suppressing chatter vibration has been demonstrated. However, issues that can lead to adhesion and tool damage pose challenges from a practical viewpoint. To overcome such issues, this paper proposes new texture geometries that improve the practical performance: parallel line type, vertical line type, and dot type. The results of a series of finite element analyses showed that the effectiveness of process damping depends on the vibration amplitude and wavelength. The proposed flank textures were fabricated on tool flank faces, and turning tests were carried out. The experimental results showed that the proposed tool is stabler than the conventional untextured tool and that it can more effectively improve the critical cutting speed, reduce the vibration amplitude, and decrease the surface roughness after cutting. With the appropriate design of the texture distance, adhesion and tool damage were hardly observed, and a stable and practical cutting could be realized.

Identification and robust control for regenerative chatter in internal turning with simultaneous compensation of machining error

The motivation behind this study is the problem of regenerative chatter vibration in internal turning. Regenerative chatter is an extremely undesired phenomenon in machining. This is since, in addition to causing surface finish degradation and cutting tool wear, regenerative chatter imposes a fundamental limitation on the material removal rate. In internal turning, due to the relatively low internal damping of the boring bar, regenerative chatter is especially undesired. Another factor, which reduces the material removal rate, as well as surface accuracy, is machining error. Machining error is very common in internal turning due to low boring bar stiffness. At the same time, machining error compensation has received little attention in the literature hitherto. This study proposes a control methodology for chatter vibration suppression with simultaneous compensation of the machining error in internal turning. The proposed methodology consists of three components. The first component is a newly developed method for the identification of the cutting force model parameters. The second component, which utilizes the cutting force model parameters identified in the previous step, is a robust stabilizing controller synthesis developed to address the key issues arising in the context of regenerative chatter control in the internal turning process. In contrast to the corresponding control methods reported in the literature, the control approach developed in this study accounts explicitly for the time-delayed term associated with the regenerative feature of chatter, as well as uncertainty in both cutting force and the flexible boring bar models. The last third component of the presented control methodology is a novel approach for machining error compensation, which is based on a feedforward term designed to eliminate the bar tip deflection. Every single component of the proposed control methodology can be utilized separately in the context of active control in internal turning. The potential applicability of the control methodology presented in this study is demonstrated experimentally, using an active slender bar demonstrator imitating the internal turning process. In particular, it is demonstrated that: (i) given the identified model of the boring bar, the proposed method for cutting parameters estimation allows to obtain reasonable estimations of the cutting coefficient and the overlap factor, (ii) the presented robust control system synthesis procedure allows to obtain controllers which increases the chatter immunity of the actively controlled cutting process, and (iii) the presented method for machining error compensation counteracts successfully the error due to flexible bar deflection caused by the DC component of the cutting force model.

Surface finish improvement using a damping-alloy sleeve-insert tool holder in the end milling process

This study investigates the effect of a tool holder with a metallic damping alloy on both vibration reduction and surface finish improvement for use in an end-milling process. Two different configurations of damping alloys are designed: a collet and a sleeve inside a conventional tool holder. To determine the system characteristics including damping effects, an experimental verification was organized, after that actual machining tests are conducted. The damping effects of each tool holder are compared through machining tests on carbon-fiber reinforced plastics (CFRP) and mold steel respectively. Additionally, a chatter vibration suppression test using thin aluminum workpiece concludes that the metallic damping alloy is comparable to other damping methods. The results show that damping alloy can reduce machining vibration regardless of workpiece materials or the form of it, and the sleeve type tool holder improves the surface roughness significantly in an end-milling process for both workpiece materials.

Hybrid Edge–Cloud-Based Smart System for Chatter Suppression in Train Wheel Repair

The contact profile of a train wheel has a key role in its operation performance. Rolling smoothly and with reduced resistance results in an increase in the efficiency and safety of rail transport. The original shape and dimensions of the profile of the wheel are altered under operation of the train, especially due to braking events and the presence of external objects between the wheel and the railway. With the purpose of recovering the optimum contact profile, train wheels are periodically machined using special lathes. This repair operation is particularly critical in freight trains, which are only reshaped a few times throughout their service life and, therefore, high depths of cut are required to recover the wheel in a productive way. As the presence of chatter vibrations limits the productivity of these operations, a hybrid edge–cloud computing approach has been developed for chatter vibration suppression. An expert system based on automatic chatter detection and suppression has been developed in the edge. The expert system is based on continuous real-time vibration monitoring and combines continuous spindle speed variation (CSSV) and cutting speed reduction to suppress chatter. Cloud computing is used to extract wheel profile machining fingerprints and obtain insights from multiple aggregated machined wheels. An industrial implementation of the system is described in the present work.

Suppression of chatter vibration using parallel turning assisted with swing motion

Suppression of chatter vibration using parallel turning assisted with swing motion

推定切削力を応用した不等ピッチターニングによるびびり振動抑制

推定切削力を応用した不等ピッチターニングによるびびり振動抑制

Boring bar with constrained layer damper for improving process stability

Boring is one of the most common operations to enlarge or finish predrilled deep holes and is usually conducted in low spindle speed ranges. Due to low dynamic performances of conventional boring bar, boring operation is often hindered by drastic vibration. In this paper, a design and optimization method of a special boring cutter with constrained layer damping (CLD) bar is developed based on the CLD beam theory and finite element method (FEM). The boring cutter designed is composed of four modules: cutting head, substrate layer, damping layer, and constrained layer, which can greatly improve the dynamic performances in boring process. Meanwhile, the effectiveness and capability of boring cutter with CLD bar for forced- and chatter-vibration suppression are presented based on experimental and numerical methods. The results show that (1) the method for restraining forced vibration is different from that for chatter suppression. The former can be greatly avoided by shifting the natural frequency of boring system, e.g., changing dynamic stiffness. The latter, due to its complexity in low spindle speed range, on the other hand, cannot be entirely avoided and can only be eliminated by reducing the possibility of occurrence, e.g., increasing damping. (2) The boring cutter with CLD bar developed can change dynamic stiffness through constrained layer and improve damping performance through damping layer. So, it can avoid forced vibration and eliminate chatter to some extent. In the presented parameter domains, the capability of CLD bar for chatter suppression is improved five times corresponding to that of conventional bar.

Active chatter suppression in turning by band-limited force control

The suppression of chatter vibration is required to enhance the machined surface quality and to increase tool life. In this study, a new, conceptually active approach for chatter suppression in machining is proposed. The hybrid control method developed by applying sensorless force control with a disturbance observer enables the simultaneous and independent control of the position trajectory and band-limited forces. The proposed method is introduced to the carriage of a prototype desktop-sized turning machine, and the ability to suppress chatter is evaluated by end-face cutting tests. The results demonstrate that actively controlling a band-limited force leads to the avoidance of chatter.

A synthetic criterion for early recognition of cutting chatter

Cutting chatter is a violent self-excited vibration between a tool and a workpiece. Its negative effects mainly include poor surface quality, inferior dimensional accuracy, disproportionate tool wear or tool breakage, and excessive noise. Therefore, early recognition and online suppression of chatter vibration are necessary. This paper proposes a novel synthetic criterion (SC) for early chatter recognition. The proposed SC integrates standard deviation (STD) and one-step autocorrelation function (OSAF). Moreover, this paper revised the fast algorithm of OSAF. We can quantitatively divide a chatter vibration signal into three stages, which are stable stage, transition stage and chatter stage according to the SC. Compared with STD, the SC can improve the reliability of chatter recognition and the threshold of SC is not sensitive to variable cutting conditions. This paper presents an original algorithm of SC and its fast algorithm in detail. The fast algorithm of SC in this paper improves the computation efficiency compared with the original algorithm of SC. To validate the effectiveness of the proposed SC, a series of milling experiments were conducted under different cutting conditions. In these experiments, the vibration signals were acquired by two accelerometers mounted on the spindle house. The experimental results showed that the proposed SC could effectively recognize chatter vibration at an early stage of chatter vibration, which saved valuable time for online chatter suppression.

Disturbance Observer–Based In-process Detection and Suppression of Chatter Vibration

Chatter vibration can be monitored by using external sensors such as acceleration sensors and dynamometers. However, from the viewpoint of reliability, using external sensors leads to an increase in failure rate. Therefore, we developed a disturbance observer theory–based method for the detection of chatter vibration, and confirmed its validity experimentally. The developed method does not require the use external sensors. In this study, a system for the in-process suppression of chatter vibration is developed by applying the abovementioned detection method. In a milling test, conducted to verify the developed system, it was found that chatter vibration was successfully suppressed by automatic adjustments to the cutting conditions.

Suppression of Chatter Vibration by Fuzzy Sliding Mode Control in Machining Processes

Chattering elimination of machining processes is an important issue in turning operation, due to the damages caused by this phenomenon. Limited productivity rate, decrease in tool life, poor surface quality and noisy workplace are some adverse effects of the chatter vibration. In this paper two control strategies are developed to suppress chatter vibration in turning process including a worn tool. A single degree of freedom model of the turning process including tool wear is briefly described. In the first stage, sliding mode approach used to control the system, and in the second stage fuzzy sliding mode approach is used. The simulation results indicate that the fuzzy sliding mode performs better than the direct sliding mode controller.

Detection of chatter vibration in end milling applying disturbance observer

Suppression of chatter vibration is required to improve the machined surface quality and enhance tool life. For monitoring the chatter vibrations, additional sensors such as acceleration sensors are generally used, which results in high costs and low reliability of the machine tools. In this study, a novel in-process method to detect chatter vibrations in end milling is developed on the basis of a disturbance observer theory. The developed system does not require any external sensors because it uses only the servo information of the spindle control system. Self-excited and forced chatter vibrations are successfully detected.

Research on the Chatter Suppression During Machining Thin-Walled Complex Blades

This paper presents a new method for chatter suppression during finishing thin-walled blades. Traditionally auxiliary support is used to increase the stiffness of the structure, however, the shrink or dilate effect of the packing material, such as wax and rosin, is difficult to control, so the machining precision could not be assured. Based on the principle of stiffness optimization principle, the rigidity of the cantilever blade tip and leading/trailing edge region are improved with the non-uniform allowances distribution. The milling experiments have showed that the proposed strategy could be successfully used to realize the suppression of chatter vibration during flexible parts machining.

Suppression of chatter vibration of boring tools using impact dampers

In this study, improvement of the damping capability of boring tools and suppression of chatter vibration were attempted using impact dampers. Bending tests, impact tests and cutting tests were carried out, whilst widely varying the method of applying an impact damper to a boring tool. The effects of the amount of free mass and clearance, the overhang length of boring tools and their cutting condition were investigated. As a result, the following points were clarified. (i) The damping capability of boring tools is considerably improved using impact dampers. (ii) All three types of impact dampers used in the experiment can considerably suppress the vibration of boring tools in the vertical direction (principal force direction), but hardly suppress it in the horizontal direction (thrust force direction) where the amplitude is extremely small. (iii) In practical use, the method of equipping an impact damper on the flank face of a boring tool is desirable. (iv) Using an impact damper, it is possible to bore deeper holes in comparison with boring tools now on the market and to improve the efficiency of boring operations.