Vibration measurement is one of the most widely used indirect methods of tool condition monitring, but vibration signal features may be affected by overhang lenght. In turning process, it is known that for the best overall machining results, tool overhang should be kept to a minimum. However, a longer tool overhang may be required depending on the geometry of the workpiece and in situations such as internal turning process. The long overhang increases vibration. In this paper the relations between tool overhang and the most commonly used signal features is investigated

K. Khalili

M. Danesh

Journal of Measurements in Engineering

  © VIRBROENGINEERING. ISSN PRINT 2335-2124, ISSN ONLINE 2424-4635, KAUNAS, LITHUANIA 171 
27. Investigation of overhang effect on cutting tool 
vibration for tool condition monitoring 
K. Khalili1, M. Danesh2 
1, 2The University of Birjand, Birjand, Iran 
2Corresponding author 
E-mail: 1kkhalili@birjand.ac.ir, 2mdanesh_ir@yahoo.com 
(Received 20 September 2013; accepted 26 September 2013) 
Abstract. Vibration measurement is one of the most widely used indirect methods of tool 
condition monitring, but vibration signal features may be affected by overhang lenght. In turning 
process, it is known that for the best overall machining results, tool overhang should be kept to a 
minimum. However, a longer tool overhang may be required depending on the geometry of the 
workpiece and in situations such as internal turning process. The long overhang increases 
vibration. In this paper the relations between tool overhang and the most commonly used signal 
features is investigated. 
Keywords: vibration, condition monitoring, cutting tool. 
1. Introduction 
Several kinds of sensors and signal processing techniques have been developed for the direct 
or indirect detection of tool wear and breakage and the identification of chatter in machining 
process. Sensors are subjected to analogue and digital signal conditioning and processing with the 
aim of generating functional signal features correlated with tool state. Sensor signal features are 
then fed to and evaluated by cognitive decision making support systems for the final diagnosis [1]. 
Vibration measurement is one of the indirect methods of tool condition monitring [1]. Metal 
cutting processes can entail three different types of mechanical vibrations that arise due to the lack 
of dynamic stiffness of one or several elements of the system composed by the machine tool, the 
tool holder, the cutting tool and the workpiece. These three types of vibrations are known as free 
vibrations, forced vibrations and self-excited vibrations [2]. The nature of the vibration signal 
arising from the metal cutting process is such that it incorporates facets of free, forced, periodic 
and random types of vibration [3]. Several machining variables, such as cutting speed, depth of 
cut, feed rate, workpiece material, and cutting tool geometry have significant effects on the 
machining process and vibrations [1, 4]. A large number of research works has been carried out 
on the influence of these parameters on turning process. Tool overhang is also a machining 
parameter in turning process which has significant effect on metal cutting. Tool overhang (ܮ) is 
defined as the distance that the tool extends from the end of tool holder (Fig. 1). The overhang is 
a variable that can be used to tune the turning process and infuences on vibration signal features 
that is used for tool condition monitoring, Any variation in the overhang length during machining 
process may misleads the decision making process about the tool state. In this paper the relations 
between tool overhang and vibration signal features is investigated. Although various signal 
features have been employed in the literatures, we focused on the Peak, Max-min and RMS in the 
time domain, Powr Spectral Density in the frequency domain and STFT in the time – frequency 
domain, since they are the most commonly used features.  
2. Vibrations in metal cutting 
In a machining process, three different types of mechanical vibrations are present due to a lack 
of dynamic stiffness/rigidity of the machine tool system comprising tool, tool holder, work piece 
and machine tool itself. These are the free, forced and self-excited vibrations. Free or transient 
vibrations, are induced by shock, such as impulses transferred to the structure of machine tool or 
from the initial engagement of cutting tools. Forced vibrations, resulting from periodic forces 
27. INVESTIGATION OF OVERHANG EFFECT ON CUTTING TOOL VIBRATION FOR TOOL CONDITION MONITORING.  
K. KHALILI, M. DANESH 
172 JOURNAL OF MEASUREMENTS IN ENGINEERING. DECEMBER 2013, VOLUME 1, ISSUE 4  
within the system such as unbalance defects in machine tool components ( like gears, spindles and 
bearings), and vibration transmitted through the foundations from other machinery in the shop. 
Self-excited chatter vibrations, usually resulting from a dynamic instability of the cutting process 
(such as cutting with large tool-work engagements), are still not fully understood due to its 
complex nature. They are most harmful for any machining process. Free and forced vibrations can 
be easily identified and sources of vibration can be removed, but chatter vibrations are less easily 
controlled. It is important to suppress vibrations of the machine tool structure as their presence 
results in poor surface quality, unacceptable inaccuracy, tool wear and machine tool damage [7-9]. 
Typically, chatter arises from a lack of stiffness in the tool in the direction of the tool-holder or in 
a normal direction. Indeed, the most common cases represented in the literature usually involve 
facing operations where the tool vibrates in the feed direction (called type A chatter by Tobias 
et al.). However, there is another type of chatter (type B chatter) where the cutting edge vibrates 
parallel to the cutting speed direction or to a component in this direction. Type A chatter arises for 
short overhangs, generally in the radial direction, whereas type B chatter occurs for large tool 
overhangs. Fig. 2 shows chatter due to a tangential mode for longitudinal turning operations [10]. 
 
Fig. 1. Tool holder deflection due to tangential force [5, 6] 
 
Fig. 2. Chatter due to a tangential mode for longitudinal turning operations [10] 
3. The Effect of tool holder overhang on cutting tool vibration 
It is known that for best overall machining results, tool overhang should be kept to a minimum, 
however a longer tool overhang may be required depending on the geometry of the workpiece and 
in situations such as internal turning process. The long overhang increases vibration. Increasing 
the vibration of cutting tool through increasing the tool overhang will cause the increase in 
irregularity of surface texture of work piece and decrease in tool life and productivity of turning 
process. The surface roughness of work piece is proportional to cutting tool acceleration [11]. 
Abouelatta and Madi in their research developed a mathematical model for surface roughness 
prediction based on cutting parameters and tool vibration. They used tool overhangs as input 
variable and selected 38 and 70 mm tool overhangs [12]. Kassab and Khoshnaw in their study to 
find correlation between surface roughness and cutting tool vibration in turning process conducted 
27. INVESTIGATION OF OVERHANG EFFECT ON CUTTING TOOL VIBRATION FOR TOOL CONDITION MONITORING.  
K. KHALILI, M. DANESH 
 © VIRBROENGINEERING. ISSN PRINT 2335-2124, ISSN ONLINE 2424-4635, KAUNAS, LITHUANIA 173 
some cutting test on the lathe machine and examined the ranges of process cutting parameters 
(cutting speed, depth of cut, and feed rate) and tool overhanging. They selected 25, 30, 35 and 
40 mm overhangs. Their results show that surface roughness increased with an increase in tool 
vibration [11]. The cutting tool can be considered as a cantilever beam (Fig. 1). In cantilever 
beams deflection which is calculated by the Eq. 1 is a function of length of overhang: 
ߜ = − ܨ௖ܮ
ଷ
3ܧܫ . (1)
Here, ܨ௖ is the cutting force, ܮ is the tool overhang, ܧ is the modulus of elasticity, and ܫ is the 
moment of inertia.  
It can be seen that deflection is a function of length of overhang in cantilever beams, so a small 
change in overhang length can greatly change deflection and vibration tendencies. The tool holder 
is also subjected to the effect of the bending momentum and torque. Since the cutting force is not 
applied in the symmetry axis, Eq. 1 cannot exactly represent the actual deflection. To determine 
the displacement of the tool tip more accurately, Kiyak et al. used Castigliano’s Theorem such 
that the effects of bending momentum and torque are taken into consideration. Although the static 
coefficient can be easily derived from the formula for a cantilevered beam in Strength of materials, 
the dynamic factor is the real key to constructing precise stability charts. In chatter due to a 
tangential mode of a tool, the stability of the system is strongly determined by this coefficient, 
which differs notably from its static value [10]. For this reason Urbikain et al. proposed a non-
dimensional parameter (߭) not only on the dynamic features of the system, but also on the cutting 
geometry of the tool and will have a decisive influence on the chip thickness. Indeed, this 
parameter is built from the modal stiffness (݇) and the natural frequency (߱௡) of the system, the 
cutting coefficient (݇௖௬ ), the cutting edge engaged during machining (ܾ ) and the vibration 
frequency (߱): 
ݒ = ݇݇௖௬ܾ ቈ൬
߱௖
߱௡൰
ଶ
− 1቉. (2)
Although evaluation of cutting tool deflections due to increase in tool overhang is important 
but it is also necessary to investigate how the increase in tool overhang affect the vibration and 
stability of cutting. 
4. Experimental setup and procedure 
For the current study, the cutting tests were carried out on a TN50D lathe machine under dry 
cutting conditions. Figure 3 shows the experimental set-up. A digital microscope was attached to 
the carriage of the lathe by means of a specially prepared stand to observe foot print of cutting 
vibration on surface of workpiece. Experiments with different overhang were conducted on the 
lathe machine and an accelerometer was attached to the shank of cutting tool for measuring 
vibrations in tangential direction. The experimental instruments and cutting conditions are shown 
in Table 1. 
5. The Effect of tool overhang on vibration signal features of cutting tool  
There are several signal features that have been extracted from signals for tool condition 
monitoring. The most common features are the statistical features in the time domain, amplitude 
of dominant spectral peaks, signal power in specific frequency ranges, energy in frequency bands, 
statistic features of band power spectrum such as mean frequency, variance, frequency of the 
spectrum highest peak , Short Time Fourier Transform (STFT) and wavelet transform [1, 13]. For 
example Fig. 4 shows the Power Spectral Density (PSD) diagram of the vibration signals in feed 
27. INVESTIGATION OF OVERHANG EFFECT ON CUTTING TOOL VIBRATION FOR TOOL CONDITION MONITORING.  
K. KHALILI, M. DANESH 
174 JOURNAL OF MEASUREMENTS IN ENGINEERING. DECEMBER 2013, VOLUME 1, ISSUE 4  
direction with respect to tool wear in turning process and Fig. 5 shows the peak of displacement 
and acceleration of cutting tool with respect to tool wear in milling process. 
 
Fig. 3. Experimetal set up 
Table 1. The experimental instruments and cutting conditions 
TN50B Lathe Machine 
Brass bars of ݂ diameter 30 mm Workpiece
Coated Carbide Insert
Global Test AP98 Accelerometer 
Advantech 4704 Data Acquisition System
InsizeDigital microscope 
MarSurf M 300 CRoughness meter
Depth of Cut = 1 mm 
Machining Conditions Spindle Speed = 1000 rev/min 
Feed rate = 0.20 mm/rev 
40, 50, 60, 70, 80, 90, 100, 110 Overhang Length (mm)
 
Fig. 4. The PSD diagram of the vibration signal in feed direction [14] 
In this research the anaysis of time-domain waveform of acceleration signal, which shows how 
the amplitude of the signal changes over time in tangential direction is performed by several 
vibration level measurements. Peak, Max-Min and RMS of acceleration signal for diffrent tool 
overhang lengths are compared. The RMS level of a signal is the square root of the mean value of 
the squared signal: 
27. INVESTIGATION OF OVERHANG EFFECT ON CUTTING TOOL VIBRATION FOR TOOL CONDITION MONITORING.  
K. KHALILI, M. DANESH 
 © VIRBROENGINEERING. ISSN PRINT 2335-2124, ISSN ONLINE 2424-4635, KAUNAS, LITHUANIA 175 
݃௥௠௦ = ඩ
1
ݐଶ − ݐଵ න ݃
ଶ
௧మ
௧భ
ሺݐሻ݀ݐ, (3)
where ݐଶ– ݐଵ is the integration time or measurement time. Fig. 6 shows the effect of tool overhang 
on vibration level measurements. The figure indicates that the Peak, Max-Min and RMS level of 
acceleration signal increases with the increase of tool overhang.  
 
Fig. 5. Relationship between the vibration amplitude and the tool wear:  
(a) displacement, (b) acceleration [15] 
 
Fig. 6. The effect of tool overhang on vibration level measurements 
 
Fig. 7. Power spectral density function for diffrent tool overhangs 
27. INVESTIGATION OF OVERHANG EFFECT ON CUTTING TOOL VIBRATION FOR TOOL CONDITION MONITORING.  
K. KHALILI, M. DANESH 
176 JOURNAL OF MEASUREMENTS IN ENGINEERING. DECEMBER 2013, VOLUME 1, ISSUE 4  
Frequency domain analysis of vibration is performed using PSD function. The maximum value 
of PSD is a reliable indicator of the overal stability of the machining process [16]. PSD describes 
how the power of a signal or time series is distributed over the different frequencies. In Fig. 7 the 
waterfall graph displays the power spectral density function of accelertion signal for diffrent tool 
overhangs  
Fig. 8 which is derived from Fig. 7, indicates that the maximum of power spectral density 
(ܲܵܦ௠௔௫) in the tangential direction increases with the increase of tool overhang and frequency 
at maximum of power spectrum density (ܨݎ݁ݍ௉ௌ஽) decreases.  
Fig. 9 shows the STFT of the signals related to different overhang lengths, STFT uses a 
window sliding along the time axis to characterize the change of frequency components at 
different time intervals. 
Fig. 10 shows the effect of tool overhangs on surface roughness and texture of workpiece. It 
is observed that increasing the vibration of cutting tool through increasing the tool overhang will 
cause the increase in roghness and irregularity of surface of work piece. 
 
Fig. 8. Effect of overhang on maximum of PSD (ܲܵܦ௠௔௫) and frequency at maximum of PSD (ܨݎ݁ݍ௉ௌ஽)  
a) b) 
Fig. 9. STFT of the signals related to different overhangs: (a) ܮ = 40mm (b) ܾ = 110 mm 
 
Fig. 10. The effect of vibration resulting from increasing tool overhangs  
on surface roughness and texture of workpiece 
27. INVESTIGATION OF OVERHANG EFFECT ON CUTTING TOOL VIBRATION FOR TOOL CONDITION MONITORING.  
K. KHALILI, M. DANESH 
 © VIRBROENGINEERING. ISSN PRINT 2335-2124, ISSN ONLINE 2424-4635, KAUNAS, LITHUANIA 177 
6. Conclusions 
In this study, the relations between tool overhang and vibration signal features are investigated. 
Although various signal features have been employed in the literatures, we focused on the Peak, 
Max-Min and RMS in the time domain, Powr Spectral Density in the frequency domain and STFT 
in the time – frequency domain, since they are the most commonly used features. The resaults 
show that Peak, Max-Min and RMS level of vibration signal increase with increased tool overhang. 
The resaults also indicate that the maximum of power spectral density in the tangential direction 
increases with the increase of tool overhang but the frequency at maximum of power spectrum 
density decreases. The resaults are similar to tool wear, therefore varying the overhang length 
during machining process may misleads the decision making process of monitoring system about 
the tool state. Based on this study, it can be concluded that vibration signal features in tangential 
direction are highly affected by overhang length. The surface image of workpiece clearly shows 
the effect of vibrations resulting from increasing of the tool overhang.  
References 
[1] Teti R., Jemielniak K., Donnell G. O, Dornfeld D. Advanced monitoring of machining operations. 
CIRP Annals – Manufacturing Technology, Vol. 59, 2010, p. 717-739. 
[2] S. A. Tobias Machine Tools Vibrations (Vibraciones en Ma ´quinas-Herra- mientas). URMO, Spain, 
1961. 
[3] Dimla E. Dimla Snr. Sensor signals for tool-wear monitoring in metal cutting operations – a review 
of methods. International Journal of Machine Tools & Manufacture, Vol. 40, 2006, p. 1073-1098. 
[4] G. Litak, R. Rusinek Vibrations in stainless steel turning: multifractal and wavelet approaches. 
Journal of Vibroengineering, Vol. 13, Issue 1, 2011, p. 102-108. 
[5] Kiyak M., Kaner B., Sahin I., Aldemir B., Cakir O. The dependence of tool overhang on surface 
quality and tool wear in the turning process. Int. J. Adv. Manuf. Techno., Vol. 51, 2010, p. 431-438. 
[6] Sandvic Switch to hard-part turning, http://www2.coromant.sandvik.com/coromant/pdf/Switch 
toHard_part_ turning/C-1040-069.pdf 
[7] Siddhpura M., Paurobally R. A review of chatter vibration in turning. International Journal of 
Machine Tool & Manufacture, Vol. 51, 2012, p. 27-47. 
[8] Quintana G., Ciurana J. Chatter in machining processes: A review. International Journal of Machine 
Tools & Manufacture, Vol. 51, 2011, p. 363-376. 
[9] Boothroyd G., Knight W. A. Fundamentals of Machining and Machine, 2006. 
[10] Urbikain G., Fernandez A., Lopez de Lacalle L. N., Gutierrez M. E. Stability lobes for general 
turning operationswith slender tools in the tangential direction. International Journal of Machine Tools 
& Manufacture, Vol. 67, 2013, p. 35-44. 
[11] Kassab S. Y., Khoshnaw Y. K. The effect of cutting tool vibration on surface roughness of workpiece 
in dry turning operation. Eng. Tech., Vol. 25, Issue 7, 2007, p. 879-889. 
[12] Abouelatta O. B., Madi J. Surface roughness prediction based on cutting parameters and tool 
vibrations in turning operations. J. Mater. Process. Technol., Vol. 118, 2001, p. 269-277. 
[13] Zhu Kunpeng, Wong Yoke San, Hong Geok Soon Wavelet analysis of sensor signals for tool 
condition monitoring A review and some new results. International Journal of Machine Tools & 
Manufacture, Vol. 49, 2009, p 537-553. 
[14] Jiang C. Y., Zhang Y. Z., H. J. Xu In-process monitoring of tool wear stage by the frequency band-
energy method. Annals of the CIRP, Vol. 36, Issue 1, 1987, p. 45-48. 
[15] Sadettin Orhan S., Ali Osman Er, Necip Camus-cu, Ersan Aslan Tool wear evaluation by vibration 
analysis during end milling of AISI D3 cold work tool steel with 35 HRC hardness. NDT&E 
International, Vol. 40, 2007, p. 121-126. 
[16] Tsai S. Y., Eman K. F., Wu S. M. Chatter suppression in turning. NAMRC proceedings, 1980, 
p. 389-402. 


English

Investigation of overhang effect on cutting tool vibration for tool condition monitoring

https://www.jvejournals.com/article/14705/pdf

Investigation of overhang effect on cutting tool vibration for tool condition monitoring

Abstract

Similar works

Full text

Available Versions

Journal of Measurements in Engineering