scholarly journals Comparison of different mathematical models for prediction of self-excited vibrations occurance in milling process

2020 ◽  
Vol 3 (2) ◽  
Author(s):  
Aleksandar Kosarac ◽  
Cvijetin Mladjenovic ◽  
Milan Zeljkovic ◽  
Lana Sikuljak
Keyword(s):  
Machine Tools ◽  
Metal Cutting ◽  
Influencing Factor ◽  
Mechanical Vibration ◽  
Decisive Role ◽  
Milling Process ◽  
Stability Lobe ◽  
Excited Vibration ◽  
Stability Lobe Diagrams

In modern production, despite the existence of other production methods, metal cutting still plays an important role. The performance of machine tools has a decisive role in terms of productivity and quality of production increase. Undoubtedly, productivity and quality of production are two mail requirements which are key elements to stay on top in a competitive market. One of the most influencing factor that affect the machine tools are vibrations. The most unwanted vibrations that can appear during metal cutting process are self-excited vibrations, which are one of the three kinds of mechanical vibration, free vibration, forced vibration, and self-excited vibration. When it comes to improving the performance of machine tools, the analysis of the appearance of self-excited vibrations and their isolation occupy a significant place. The aim of this paper derives from trends and limitations exists in metal production. The way to isolate the self-excited vibrations is to predict their occurrence by defining the stability lobe diagram. The paper presents two popular analytical methods for identifying stability lobe diagrams in milling, which shows the boundary between stable and unstable zone of machining operations, depending on the number of revolutions of the spindle and cutting depth. First considered method is Fourier series approach and second one id average tooth angle approach. Lather, both stability lobe diagrams were compared with results obtained experimentally.

Dynamics of the processes in metal machining

1998 ◽  
Vol 2 ◽  
pp. 115-122
Author(s):  
Donatas Švitra ◽  
Jolanta Janutėnienė
Keyword(s):  
High Frequency ◽  
Machine Tools ◽  
Metal Cutting ◽  
Cutting Tool ◽  
Low Frequency ◽  
Metal Cutting Machine ◽  
Cutting Machine ◽  
Metal Machining

In the practice of processing of metals by cutting it is necessary to overcome the vibration of the cutting tool, the processed detail and units of the machine tool. These vibrations in many cases are an obstacle to increase the productivity and quality of treatment of details on metal-cutting machine tools. Vibration at cutting of metals is a very diverse phenomenon due to both it’s nature and the form of oscillatory motion. The most general classification of vibrations at cutting is a division them into forced vibration and autovibrations. The most difficult to remove and poorly investigated are the autovibrations, i.e. vibrations arising at the absence of external periodic forces. The autovibrations, stipulated by the process of cutting on metalcutting machine are of two types: the low-frequency autovibrations and high-frequency autovibrations. When the low-frequency autovibration there appear, the cutting process ought to be terminated and the cause of the vibrations eliminated. Otherwise, there is a danger of a break of both machine and tool. In the case of high-frequency vibration the machine operates apparently quiently, but the processed surface feature small-sized roughness. The frequency of autovibrations can reach 5000 Hz and more.

Dynamisches Verhalten von Gestellwerkstoffen in Werkzeugmaschinen*/Dynamic behavior of different machine frame materials

2015 ◽  
Vol 105 (05) ◽  
pp. 263-268
Author(s):  
P. H. Nebeling
Keyword(s):  
Dynamic Behavior ◽  
Machine Tools ◽  
Dynamic Behaviour ◽  
Influencing Factor ◽  
Complex Structures ◽  
Geometric Properties ◽  
Long Time

Das dynamische Verhalten von Werkzeugmaschinen ist für die Stabilität während der Bearbeitung sowie die Qualität der erzeugten Werkstücke von besonderer Bedeutung. Ein Einflussfaktor darauf ist die Dämpfung. Im Bereich der Maschinengestelle kommen seit langer Zeit unterschiedliche Materialien zum Einsatz. In diesem Fachbeitrag werden die Dämpfungskennwerte unterschiedlicher Gestellwerkstoffe an geometrisch gleichen Proben vergleichend gegenübergestellt. Als weitere Kenngröße wurde die Lage der (1. Biege-) Eigenfrequenz als Maß für die massebezogene dynamische Steifigkeit verwendet. Die Effekte beim Übergang von einfachen Bauteilen zu komplexen Strukturen runden den Fachartikel ab.   The dynamic behaviour of machine tools is of great importance for stability and quality of the machined work pieces. One influencing factor in this area is damping. In the field of machine bases different materials have been use since long time. In this article the damping values of different materials with equal geometric properties are compared. As further parameter the first bending Eigenfrequency as dimension for mass related stiffness is use. The transition from simple components to complex structures is touched at the end of the paper.

Machining a Micro-Scale Structure Using an in-House Developed Miniature Machine Tool

2011 ◽  
Vol 418-420 ◽  
pp. 1502-1506
Author(s):  
Abdul Shukor Syaimak
Keyword(s):  
Surface Quality ◽  
Machine Tools ◽  
Milling Process ◽  
Micro Milling ◽  
Batch Size ◽  
End Mill ◽  
Geometrical Accuracy ◽  
Custom Made ◽  
Solid Carbide

Custom-built Miniature Machine Tools (MMTs) are now becoming more popular with the demand for reduced energy consumption and workshop floor when machining small/medium batch size micro-components. This paper investigates the capability of a custom-built 4-axis MMT through machining a micro-component demonstrator. The experiments have been carried out in Titanium Alloyed (TiAL6V4) using 0.6mm solid carbide flat end mill cutters. From here, the surface quality and geometrical accuracy of the machined testpiece are evaluated and analysed. The investigation has shown that acceptable geometrical accuracies and surface quality of the machined micro-demonstrator can be achieved using the in-house developed MMT. These results show that the use of the custom-made MMT does not hinder the micro-milling process to produce a good and satisfactory surface quality and acceptable geometrical accuracy.

Regulation of an ovulatory cycle

1998 ◽  
Vol 2 ◽  
pp. 107-114 ◽  
Author(s):  
D. Švitra ◽  
R. Grigolienė ◽  
A. Puidokaitė
Keyword(s):  
High Frequency ◽  
Machine Tools ◽  
Metal Cutting ◽  
Cutting Tool ◽  
Low Frequency ◽  
Metal Cutting Machine ◽  
Ovulatory Cycle ◽  
Cutting Machine

In the practice of processing of metals by cutting it is necessary to overcome the vibration of the cutting tool, the processed detail and units of the machine tool. These vibrations in many cases are an obstacle to increase the productivity and quality of treatment of details on metal-cutting machine tools. Vibration at cutting of metals is a very diverse phenomenon due to both it’s nature and the form of oscillatory motion. The most general classification of vibrations at cutting is a division them into forced vibration and autovibrations. The most difficult to remove and poorly investigated are the autovibrations, i.e. vibrations arising at the absence of external periodic forces. The autovibrations, stipulated by the process of cutting on metalcutting machine are of two types: the low-frequency autovibrations and high-frequency autovibrations. When the low-frequency autovibration there appear, the cutting process ought to be terminated and the cause of the vibrations eliminated. Otherwise, there is a danger of a break of both machine and tool. In the case of high-frequency vibration the machine operates apparently quiently, but the processed surface feature small-sized roughness. The frequency of autovibrations can reach 5000 Hz and more.

Stability Modeling and Analysis of Orthogonal Turn-Milling with Variable Cutting Depth and Cutting Thickness

2014 ◽  
Vol 852 ◽  
pp. 419-426
Author(s):  
Yong Wang ◽  
Rong Yan ◽  
Fang Yu Peng ◽  
Feng Qiu
Keyword(s):  
Milling Process ◽  
Cutting Depth ◽  
Modeling And Analysis ◽  
Stability Lobe ◽  
Stability Model ◽  
The Stability ◽  
Turn Milling ◽  
Stability Lobe Diagrams ◽  
Better Than ◽  
Stability Modeling

In orthogonal turn-milling process, both of the workpiece and the cutter rotate at the same time, which causes cutting depth and cutting thickness to change instantaneously. In this paper, a new 2D stability model of orthogonal turn-milling is established, in which the effect of variable cutting depth and cutting thickness is considered. The stability lobe diagrams are obtained by using Full-discretization Method. By analyzing the stability of orthogonal turn-milling, it is found that it is better than that of ordinary milling in same machining conditions. It means that in orthogonal turn-milling process deep cutting depth can be chosen and high machining efficiency can be obtained compared to that in ordinary milling process.

Dynamic modeling and stability prediction in milling process of thin-walled workpiece with multiple structural modes

2020 ◽  
pp. 095440542093371
Author(s):  
Zhao Zhang ◽  
Ming Luo ◽  
Baohai Wu ◽  
Dinghua Zhang
Keyword(s):  
Dynamic Model ◽  
Dynamic Modeling ◽  
Milling Process ◽  
Test Results ◽  
Stability Lobe ◽  
Milling Tool ◽  
Thin Walled ◽  
The Stability ◽  
Structural Mode ◽  
Stability Lobe Diagrams

Regenerative chatter can easily occur in the milling process of thin-walled workpiece due to the inherently low stiffness. This article aims to predict the stability of thin-walled workpiece in the milling process with a complete dynamic model. First, multiple structural modes of thin-walled workpiece are taken into consideration, and a complete dynamic model of thin-walled workpiece milling system is developed. Then, a numerical integration method is used to achieve the stability lobe diagrams of the milling system and identify the chatter frequency. Besides, the major structural mode, which is responsible for the occurrence of thin-walled workpiece chatter in the milling process, is predicted. A series of milling tests concerning a general cantilever plate are conducted, and the test results agree well with the predicted results, which shows the effectiveness of the proposed method. Finally, the effects of milling tool and structural modes on milling stability are discussed separately, which could provide theoretical basis for the dynamic modeling of thin-walled workpiece in milling process.

Optimization of different parameters related to milling tools to maximize the allowable cutting depth for chatter-free machining

2020 ◽  
Vol 235 (1-2) ◽  
pp. 230-241
Author(s):  
Ali Mokhtari ◽  
Mohammad Mahdi Jalili ◽  
Abbas Mazidi
Keyword(s):  
Genetic Algorithm ◽  
Cutting Tool ◽  
Milling Process ◽  
Optimization Process ◽  
Micro Milling ◽  
Beam Model ◽  
Cutting Depth ◽  
Stability Lobe ◽  
Milling Tool ◽  
Stability Lobe Diagrams

Determination of optimal parameters of cutting tool is one of the most significant factors in any operation planning of metal elements, especially in micro-milling process. This article presents an optimization procedure, based on genetic algorithms, to optimize some parameters related to micro-milling tool including number of teeth, shank diameter, fluted section diameter, shank length, taper length, and length of fluted section. The aim of this optimization is maximizing the minimum value of cutting depth on the border of stability lobe diagrams, which is called allowable cutting depth, for chatter-free machining. Cutting tool is modeled as a three-dimensional spinning cantilever Timoshenko beam based on strain gradient elasticity theory. Structural nonlinearity, gyroscopic moment, rotary inertia, and velocity-dependent process damping are also considered in the cutting tool model. The values of natural frequency, damping ratio, and material length scale of the micro-milling tool are calculated using a system identification based on genetic algorithm to match the analytical response with recorded experimental vibration signal. Using beam model, the allowable cutting depth is increased in the optimization process for a specific range of spindle speed to avoid the chatter phenomenon. Analytical study of micro-milling process stability is carried out to determine the cost function of the genetic algorithm. A plot of the greatest fitness in each generation is sketched. In addition, stability lobe diagrams before and after optimization process are presented to show the efficiency of the optimized micro-milling tool. In the presented examples, the results of genetic algorithm may lead to design or find a micro-milling tool that its acceptable cutting depth increases up to 1.9313 times.

Design and Analysis of Disturbance Force Observer for Machine Tools Application

2015 ◽  
Vol 761 ◽  
pp. 148-152
Author(s):  
J. Jamaludin ◽  
Zamberi Jamaludin ◽  
T.H. Chiew ◽  
Lokman Abdullah
Keyword(s):  
Cutting Force ◽  
System Performance ◽  
Machine Tools ◽  
Material Removal ◽  
External Disturbance ◽  
Milling Process ◽  
Frequency Content ◽  
Positioning Accuracy ◽  
Fast Fourier Transform Analysis

In milling process, the quality of tracking performance is influenced by the characteristics of the cutting forces generated during the material removal process. The undesired frequency harmonics of the cutting force contributes negatively to the positioning accuracy. An effective compensation of these harmonics is desired. This paper presents and discusses a disturbance force observer as an approach to estimate and compensate effect of external disturbance forces on system performance. Knowledge of the properties of the disturbance signal is essential for the design of an observer. A Fast Fourier Transform analysis of the disturbance force reveals the harmonics content of the signal. The frequency harmonics is a function of the spindle rotational speeds. The results show effective compensation of the cutting force with reduced amplitudes of the harmonics frequency content.

Milling Force Modeling of Formed Milling Cutter for Turnout Processing and Experiment Validation

2012 ◽  
Vol 538-541 ◽  
pp. 921-926
Author(s):  
Li Gang Cai ◽  
Fang Yuan Pu ◽  
Yong Sheng Zhao
Keyword(s):  
Process Parameters ◽  
Metal Cutting ◽  
Milling Process ◽  
Force Model ◽  
Processing Quality ◽  
Milling Force ◽  
Milling Cutter ◽  
Study Results ◽  
Milling Force Model

Turnout is one of the key components of high-speed railway, which directly affects the maximum lateral allowable speed. The formed milling cutters are usually used in the processing of turnout, and the milling force is an active factor in the milling process which affects the functions of the machine tool and the enactment of process parameters, then the processing quality of turnouts is affected. In the paper, the theoretical milling force model for formed milling cutter is built based on the theory of metal cutting, and the working profile of curved switch rail is chosen as processing object in the milling process experiments, the validity of the milling force model is verified, The study results will provide theoretical basis for tool machine design and process parameters selection, and ensuring the processing quality of turnout.

Vibration Analysis Based on AR Trispectrum in Milling Process

2010 ◽  
Vol 97-101 ◽  
pp. 1895-1901
Author(s):  
Yu Yan Jiang ◽  
Yi Jian Huang ◽  
Xiu Cheng Ye
Keyword(s):  
Surface Quality ◽  
Vibration Analysis ◽  
Metal Cutting ◽  
Cutting Parameters ◽  
Milling Process ◽  
Cutting Fluid ◽  
Depth Of Cut ◽  
Machined Surface ◽  
Machined Surface Quality

This paper presents the use of vibration analysis based on autoregressive (AR) trispectrum in milling process to indicate the relationship between machined surface quality of workpiece and spectrum character under a variety of different cutting parameter settings, such as the depth of cut, the feed rate and the spindle speed. The metal cutting experiments were performed on steel A3 material without using any cutting fluid. The experimental results for slices analysis of trispectra indicated that the spectral peaks were abundant as the milling process went smoothly. The roughness value measured reflects the machined surface quality of workpice. According to the changes for spectral peak and roughness value, a conclusion was made that the proposed trispectrum slices method for choosing cutting parameters and monitoring the machined surface quality in milling process was practicable.

Sign in / Sign up

Export Citation Format

Share Document