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1

An analysis and modeling of the dynamic stability of the cutting process against self-excited vibration

Motallebia A., Doniavi A., Sahebi Y.

Mechanics and Mechanical Engineering

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2019

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Vol. 23, nr 1

28--35

EN

Chatter is a self-excited vibration that depends on several parameters such as the dynamic characteristics of a machine tool structure, the material of work piece, the material removal rate, and the geometry of tools. Chatter has an undesirable effect on dimensional accuracy, smoothness of work piece surface, lifetime of tools and machine tools. Thus, it is useful to understand this phenomenon in order to improve the economic aspect of machining. In the present article, firstly, the theoretical study and mathematical modeling of chatter in the cutting proces were carried out. Then, by performing modal testing on a milling machine and drawing chatter stability diagrams, we determined the stability regions of the machine tool operation and recognized the parameter that had the most important effect on chatter.

2

Application of the finite element method in the milling process stability diagnosis

Dunaj Paweł, Marchelek Krzysztof, Chodźko Marcin

Journal of Theoretical and Applied Mechanics

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2019

|

Vol. 57 nr 2

353--367

EN

The article presents results of both experimental and FEM model-based investigations on chatter phenomena that occur in the end milling process. On the basis of chatter symptoms observed during machining, the mechanism of its occurrence has been identified. Then, a FEM model has been built to indicate machine tool elements responsible for loss of stability. Afterwards, experimental modal analysis has been conducted in order to validate the FEM model. Finally, on the basis of the validated model, the structural changes have been proposed and applied in the real object resulting in increased stability.

3

Influence of linear feed drive controller setting in CNC turning lathe on the stability of machining

Grau Jan, Sulitka Matej, Soucek Pavel

Journal of Machine Engineering

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2019

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Vol. 19, No. 2

18--31

EN

The paper deals with the influence of linear feed drive controller setting of a CNC turning lathe on the stability of machining. A coupled simulation model of feed drive control and ball screw drive mechanics with a transmission belt was created and validated by the feed drive diagnostic measurements. The influence of drive control on the overall dynamic compliance at the TCP and the limits of stable depth of cut was examined. Impact of the feed drive actual kinematics configuration on the stability limits was studied as well.

4

An analysis and modeling of the dynamic stability of the cutting process against self-excited vibration

Motallebia A., Doniavi A., Sahebi Y.

Mechanics and Mechanical Engineering

|

2018

|

Vol. 22, nr 4

1287--1299

EN

Chatter is a self-excited vibration which depends on several parameters such as the dynamic characteristics of the machine tool structure, the material of the work piece, the material removal rate, and the geometry of tools. Chatter has an undesirable effect on dimensional accuracy, smoothness of the work piece surface, and the lifetime of tools and the machine tool. Thus, it is useful to understand this phenomenon in order to improve the economic aspect of machining. In the present article, first the theoretical study and mathematical modeling of chatter in the cutting process were carried out, and then by performing modal testing on a milling machine and drawing chatter stability diagrams, we determined the stability regions of the machine tool operation and recognized that witch parameter has a most important effect on chatter.

5

In-process monitoring and analysis of dynamic disturbances in boring and trepanning association (BTA) deep drilling

Steininger A., Bleicher F.

Journal of Machine Engineering

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2018

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Vol. 18, No. 4

47--59

EN

This paper presents an approach to monitor the dynamic disturbances of a BTA (boring and trepanning association) deep drilling system. High length to diameter ratios are the key characteristic of deep drilling processes compared to conventional drilling applications. Since length to diameter ratios of up to 150 for slender tool-boring-bar assemblies are common, the deep drilling process is sensitive to dynamic disturbances such as chatter and whirling vibrations. Whirling vibrations usually effect the shape of the hole and cause holes with several lobes. To gain a deeper understanding of the dynamic state of the process, a sensor application has been developed and was tested in practice. Experimental investigations on BTA deep drilling with continuous multi-sensory monitoring were conducted. The used setup allowed the determination of the frequencies of chatter and whirling vibrations during the cutting process by analysing the logged data using a continuous short-time Fourier transformation (STFT).

6

In-process control with a sensory tool holder to avoid chatter

Bleicher F., Schörghofer P., Habersohn C.

Journal of Machine Engineering

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2018

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Vol. 18, No. 3

16--27

EN

Hydro-, steam- and gas- turbines, aircraft components or moulds are milled parts with complex geometries and high requirements for surface quality. The production of such industry components often necessitates the use of long and slender tools. However, instable machining situations together with work pieces with thin wall thickness can lead to dynamic instabilities in the milling processes. Resulting chatter vibrations cause chatter marks on the work piece surface and have influence on the tool lifetime. In order to detect and avoid the occurrence of process instabilities or process failures in an early stage, the Institute for Production Engineering and Laser Technology (IFT) developed an active control system to allow an in-process adaption of machining parameters. This system consists of a sensory tool holder with an integrated low cost acceleration sensor and wireless data transmission under real time conditions. A condition monitoring system using a signal-processing algorithm, which analyses the received acceleration values, is coupled to the NC- control system of the machine tool to apply new set points for feed rate and rotational speed depending on defined optimisation strategies. By the implementation of this system process instabilities can be avoided.

7

Stable and unstable milling process for nickel superalloy as observed by recurrence plots and multiscale entropy

Weremczuk A., Borowiec M., Rudzik M., Rusinek R.

Eksploatacja i Niezawodność

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2018

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Vol. 20, no. 2

318--326

EN

This paper discusses the stability of high-speed machining processes. The problem of harmful vibrations can usually be detected based on measured signal forces. Nevertheless, the chatter effect may be unrevealed and hence some alternative approaches of signal monitoring must be taken to detect it. In the discussed case of machining, process stability is determined by means of stability diagrams. The measured milling force components are investigated by various signal analysis methods. In addition to this, the analysis also uses recurrence plots, recurrence quantifications, composite multi-scale-entropy and as well the statistical approach. Results obtained by the different methods are presented and discussed.

PL

W niniejszym artykule omówiono stabilność procesu obróbki szybkościowej. Problem szkodliwych drgań zwykle może zostać wykryty na podstawie sygnału mierzonych sił. Niemniej jednak drgania samowzbudne mogą nie ujawnić się w sposób wyraźny, a niekiedy do ich wykrycia potrzebne jest alternatywne podejście do monitorowania sygnału. W przedstawionym procesie obróbki stabilność procesu oszacowano za pomocą wykresów stabilności. Zmierzone siły frezowania badano różnymi metodami analizy sygnału. W analizie wykorzystano wykresy rekurencyjne, wskaźniki rekurencyjne, entropię wieloskalową, a także podejście statystyczne. Przedstawiono wyniki różnych metod i omówiono ich porównanie.

8

Chatter detection using principal component analysis in cold rolling mill

Usmani N. I., Kumar S., Velisatti S., Tiwari P. K., Mishra S. K., Patnaik U. S.

Diagnostyka

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2018

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Vol. 19, No. 1

73--81

EN

Most cold rolling mills are prone to chatter problem. Chatter marks are often observed on the strip surface in cold rolling mill leading to downgrade and rejection of rolled material. Chatter impact product quality as well as productivity of mill. In absence of online chatter detection no corrective action can be taken immediately and whole campaign gets affected. Most conventional approach for online chatter detection is by using vibration measurement of mill stands in time & frequency domain. Present work proposes two approaches to detect chatter in cold rolling mill using a statistical technique called Principal Component Analysis (PCA). In this paper two methods are used for chatter detection. First method applies PCA on Fast Fourier Transform (FFT) to differentiate between chatter and non-chatter condition. Second method applies PCA on statistical parameters calculated from raw vibration data to detect chatter.

9

Identification of dynamic cutting force coefficients by direct measurement of cutting forces during vibratory cutting

Jemielniak K., Nejman M., Sniegulska-Gradzka D.

Journal of Machine Engineering

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2016

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Vol. 16, No. 3

47--57

EN

This paper presents the methodology of measuring the instantaneous cutting forces during vibratory cutting. It is based on elastically supported dynamometer vibrating with the tool during chatter. Acceleration of the dynamometer measured simultaneously allows for evaluation and elimination of inertia forces acting on the oscillating dynamometer. Displacements of the dynamometer and the tool in the feed direction during orthogonal cutting are measured by the contactless inductive sensor. The measurements allow for determination of averaged or instantaneous dynamic cutting force coefficients and their dependence on cutting conditions.

10

Analysis of chattering phenomenon in industrial S6-high rolling mill. Part 2: Experimental study

Papini S., Valigi M. C.

Diagnostyka

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2016

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Vol. 17, No. 4

27--32

EN

The paper represents an extension of a previous work where the problem of chatter in a rolling mill producing advanced high-strength steels (AHSS) was investigated by a combination of a linear lumped parameter model and the slab analysis. In this paper the authors show the detailed experimental study of the problem with a complete description of all the phases related to the vibrational investigation that lead to the solution of the problem. Furthermore, a different model based on the Orowan’s method together with a nonlinear model of the rolling mill is presented and simulations are performed.

11

The search for weak elements affecting the vibrostability of the system consisting of the machine tool and the cutting process, based on symptoms observed during operation

Chodźko M.

Problemy Eksploatacji

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2015

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no. 1

5--23

EN

The paper presents a methodology for the search of a “weak element” in the mass-damper-spring system of the machine tool under operating conditions, using experimental modal analysis. The subject matter of this ressearch was inspired by specific machining problems that occured in the industrial operation machine tolls. It became necessary to identify the reasons of the loss of stability, establish the self-excited vibrations mechanism, indicate the “week element” in the mass-spring-damping system, then specify the required changes in design, and verify them in practice. Athe paper also presents examples showing effectiveness of the proposed research method.

PL

W artykule przedstawiono metodologię poszukiwania „słabego ogniwa” w dynamicznym systemie, składającym się z obrabiarki oraz procesu skrawania, z użyciem metod eksperymentalnej analizy modalnej. Prace te zostały zainspirowane koniecznością rozwiązania rzeczywistych problemów obróbkowych, które miały miejsce w przemysłowej eksploatacji obrabiarek różnego typu. Koniecznym stało się zidentyfikowanie przyczyn utraty stabilności obróbki oraz wskazanie „słabego ogniwa” w układzie masowo-dyssypacyjno-sprężystym obrabiarki. W konsekwencji określono zakres wymaganych zmian konstrukcyjnych oraz zweryfikowano ich skuteczność. W artykule wykazano również praktyczną efektywność zaproponowanej metodyki prowadzenia badań obrabiarek.

12

Weryfikacja dynamicznej charakterystyki procesu skrawania przez porównanie teoretycznej i doświadczalnej granicy stabilności

Śniegulska-Grądzka D., Nejman M., Jemielniak K.

Mechanik

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2015

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R. 88, nr 12CD3

65--67

PL

Jedną z metod unikania drgań samowzbudnych podczas skrawania polega na wyznaczeniu i uwzględnieniu granicy stabilności. W pracy przedstawiono wstępną weryfikację zaproponowanego modelu dynamicznej charakterystyki procesu skrawania poprzez porównanie granicy stabilności wyznaczonej teoretycznie z uzyskaną doświadczalnie.

EN

Avoiding of self-excited vibrations during cutting involves the determination of the stability limit. The paper presents preliminary verification of the proposed model of the dynamic characteristics of the machining process by comparing the stability limit theoretically determined and experimentally obtained.

13

Symulacja numeryczna drgań samowzbudnych przy frezowaniu ze zmiennymi w czasie parametrami skrawania

Bąk P. A., Jemielniak K.

Mechanik

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2015

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R. 88, nr 12CD3

10--13

PL

W artykule przedstawiono wykorzystanie symulacji numerycznej nieliniowych drgań samowzbudnych w dziedzinie czasu w analizie stabilności procesu obróbki. Łącząc metodykę wykrywania drgań samowzbudnych z odczytem kodów maszynowych powstało narzędzie do symulacji numerycznej i walidacji programu obróbki, które jest tematem niniejszego artykułu.

EN

The paper presents utilization of numerical simulation of non-linear chatter in the time domain in stability analysis of machining process. By combining all the above in one and enabling G-code reading, a tool for numerical simulation and validation of entire machining operation was created which is a subject of this paper.

14

Badanie dynamicznych współczynników sił skrawania podczas ortogonalnego toczenia stali

Jemielniak K., Nejman M., Śniegulska-Grądzka D.

Mechanik

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2015

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R. 88, nr 3CD

16--22

PL

W artykule przedstawiono metodę bezpośredniego pomiaru chwilowych sił skrawania podczas obróbki, w czasie występowania drgań samowzbudnych. Metoda ta polega na wykorzystaniu dynamometru zamocowanego na elementach podatnych, który drga równocześnie z narzędziem, jednoczesnym pomiarze siły i przyspieszenia jak też pomiarze przemieszczenia siłomierza i narzędzia podczas skrawania ortogonalnego, mierzone na kierunku posuwu. Przyjęta metodyka pomiaru pozwala na wyznaczenie uśrednionych lub chwilowych dynamicznych współczynników siły skrawania oraz ich zależności od parametrów skrawania i zużycia narzędzia.

EN

The paper presents the method of the direct measuring the instantaneous cutting forces during chatter. This method is based on elastically supported dynamometer vibrating with the tool, on measuring the force and acceleration simultaneous, as well on measuring the displacement of the dynamometer and cutting tool during orthogonal turning, measured in the direction of feed. The measurements allow for determination of averaged or instantaneous dynamic cutting force coefficients and their dependence on cutting conditions and the tool wear.

15

Wpływ charakterystyki toru pomiarowego na bezpośredni pomiar siły skrawania w czasie występowania drgań

Nejman M., Śniegulska-Grądzka D., Jemielniak K.

Mechanik

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2014

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R. 87, nr 8-9CD1

400-407

PL

W artykule przedstawiono istotność wpływu charakterystyki toru pomiarowego na wyniki pomiarów wielkości dynamicznych. Zagadnienia te omówiono na przykładzie stanowiska do pomiarów chwilowych wartości sił skrawania w czasie drgań narzędzia względem przedmiotu obrabianego. Istotę pomiaru oparto o zamocowany na elementach podatnych siłomierz, drgający wraz z zamocowanym w nim narzędziem w czasie występowania drgań samowzbudnych lub drgań swobodnych powstałych w skutek uderzenia młotkiem modalnym. Jednoczesny pomiar siły, przyspieszeń oraz przemieszczeń siłomierza wraz z narzędziem pozwala na eliminację siły bezwładności oddziaływujące na przetworniki siłomierza i pomiar jedynie zewnętrznych sił skrawania.

EN

The paper presents relevance of the measuring chain characteristic to results of dynamic features measurements. The issue was discussed using an example of the stand for measuring of instantaneous cutting forces during vibratory cutting. The measurements are based on a dynamometer supported by elastic elements, vibrating with the tool fixed on top of it during the self - excited or free vibrations initiated by a modal hammer. Simultaneous measurement of the force, acceleration and displacements of the dynamometer and the tool allows for elimination of the inertial forces acting on the force transducers and measurement the external cutting forces.

16

Analytical time-domain model for tool point dynamics in turning

Berglind L., Ziegert J.

Journal of Machine Engineering

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2014

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Vol. 14, No. 4

75--94

EN

An analytical time domain solution is developed to model the dynamic response of a tool during a simple turning operation. The time domain solution developed in this paper relies on the superposition principal under the linear assumption to construct the time response of single mode, single degree of freedom cutting tool. The results from the analytical solution are compared with those generated using numerical time domain simulations and it is found that the two solutions converge as the time step used in the numerical simulation decreases.

17

A method of identification of complex cutting forces acting in unstable cutting process

Bach P., Polacek M., Chvojka P., Burian D., Drobilek J.

Journal of Machine Engineering

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2014

|

Vol. 14, No. 4

18--28

EN

The calculations of machining stability limit currently known do not provide a precise prediction of chatter-free cutting conditions. The inaccuracy is probably caused by mathematical models of dynamic forces acting on the cutting process during unstable machining. These models need to be modified. A new analysis of experimental data measured by one of the authors, M. Poláček, in the 1968-1974 period, forecasted an existence of several dynamic forces, which are mutually phase-shifted, thus complex. This fact has not been thoroughly investigated previously. As the assumed forces cannot be calculated from any equations, they must be identified experimentally. This research paper proposes a theoretical method of an experimental identification of these forces. The new model is intended to be used in the future for the development of a more accurate calculation of stability diagram.

18

Position paper - fundamental issues in self-excited chatter in turning. Appendix – research into process damping by Altintas et al

Ito Y.

Journal of Machine Engineering

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2013

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Vol. 13, No. 3

7--25

EN

Although observing a considerable number of new interesting behavior in dynamic states of machining, nearly all researches into the chatter vibration have been based on those conducted by Tobias, Tlusty and Merritt. In fact, we have established myriad remedies for the chatter suppression on the strength of their achievements; however, some crucial issues remain still in uncertainties, e.g., validity of penetration effects, definition duly what are the essential features of the chatter vibration. This position paper describes the facing problems of the chatter vibration in detail, aiming at the establishment of a generalized chatter loop. By this chatter loop, we may unveil synthetically the deterioration and improvement of the stability chart by all the influencing attributes, such as forced vibration and non-linearity within the machine-tool-work system.

19

Multiple regenerative effect governing chatter behaviour after onset

Sato H.

Journal of Machine Engineering

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2013

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Vol. 13, No. 3

51--76

EN

Chatter is the self-excited vibration that occurs during cutting. The entire structure of a self-excited vibration comprises two core mechanisms, i.e., stability limit and sustained vibration with finite amplitude after onset. The latter mechanism remained unnoticed until the discovery of the multiple regenerative effect (MRE) in 1980. However, its effects have not yet been recognized correctly. This paper summarizes the problems that could be resolved by considering the MRE in the analysis from the theoretical and practical viewpoints. In conventional stability limit analyses,tool traces never intersect; however, after the onset of chatter in an actual system, traces immediately intersect. This resultsin tool-workpiece separation, chip thickness variation during the separation period, and chip breakage. A solution for equation of motion considering the MRE agrees well with chatter behaviour in actual applications. In addition, the solution yields the phase relationship between the displacement of work motion and the cutting force, although this relationship is not considered in the equation of motion. Further, the relationship between the penetrating cutting speed and the resistive force, confirmed experimentally, is introduced in equation of motion, which verifies the widening of the stability region at low cutting speeds.

20

Improving machining performance against regenerative tool chatter through adaptive normal pressure at the tool clamping interface

Fu Q., Rashid A., Nicolescu C. M.

Journal of Machine Engineering

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2013

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Vol. 13, No. 1

93--105

EN

Chatter in machining process is one of the common failures of a production line. For a cantilever tool, such as a boring bar, the rule of thumb requires the overhang length of the tool to be less than 4 times the diameter. The reason is because longer overhang will induce severe tool vibration in the form of chatter during machining. When a longer overhang than 4 times diameter is necessary for performing special machining operations, damping methods are needed to suppress tool chatter. One of the methods is the constrained layer damping method. Materials, such viscoelastic material, are applied in the vibration node regions of the structure to absorb the concentrated vibration strain energy and transform the mechanical energy to heat. With a cantilever tool clamped in a tool holder, the clamping interface is usually the vibration node region. The friction in the joint interface with low normal pressure became another source of damping and can be used for tool chatter suppression in mechanical structures. Joint interfaces are well known to possess normal pressure dependent stiffness and damping. The normal pressure's effect on the structures frequency response function had been observed by H. Akesson [1] et al, and L.Mi [2] et al. However, the direct effect of the joint interface normal pressure on machining process stability hasn't been investigated. In this paper, a cantilever tool with 6,5 overhang length to diameter ratio is investigated. The direct effect of the tool clamping interface's normal pressure on the machining process stability is studied. Three different levels of clamping normal pressure are tested with an internal turning process. The machining results indicate another adaptable solution on shop floor for suppressing tool chatter.