real time chatter vibration control system in high speed ... · test tion tion ram ting ther or a...
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Journal of Materials Science and Engineering A 5 (5-6) (2015) 221-229 doi: 10.17265/2161-6213/2015.5-6.005
Real Time Chatter Vibration Control System in High Speed Milling
Hyeok Kim1, Mun-Ho Cho1, Jun-Yeong Koo1, Jong-Whan Lee2 and Jeong-Suk Kim3*
1. School of Mechanical Engineering, Pusan National University, Busan 609-735, Republic of Korea
2. Department of Mechtronics Engineering, Korea Aviation Polytechnic, Busan 616-741, Republic of Korea
3. Department of Mechanical Engineering, Pusan National University, ERC/NSDM,Busan 609-735, Republic of Korea Abstract: This paper presents the chatter vibration avoidance method in high speed milling. Chatter vibrations have a bad influence on surface integrity and tool life. So how to get the cutting conditions without chatter vibration is very important. In order to get stable cutting condition, too many parameters are required. So this paper focuses on simplification and real-time control of chatter avoidance program. The developed method uses only microphone signal for chatter vibration sensing. The measuring signal is analyzed by FFT (Fast Fourier transform) method to get whether or not the chatter vibration is generated on cutting condition. If chatter vibration occurs, the developed program suggests stable cutting speed in real time with tool teeth number, damping ratio and chatter frequency. This suggested that the program reliability is confirmed by dynamic cutting forces and surface profiles. Key words: Chatter vibration, milling, impact test, real-time control, frequency response function, lab view.
1. Introduction
Because of the acceleration and superior precision of machine tools, the numerous high-quality products are currently produced. However, chatter vibration, which degrades the quality of processed products, remains a problem to be solved. Chatter vibration, which causes problems during the manufacturing process, appears to be a self-excited vibration. When chatter vibration occurs, a chatter mark exhibits a wave pattern appears on the surface of the processed product, and thus, the processing grade is degraded. Additionally, the load on the axial system increases, the tool-life is reduced, and damage occurs owing to the vibration. Accordingly, the processing cost increases, resulting in a drop in productivity [1]. Thus, it is necessary to research a program that can detect chatter vibration and propose a stable spindle speed that can prevent chatter vibration according to the dynamic characteristics of the axial system. A lobe diagram is a graph illustrating the
*Corresponding author: Jeong-Suk Kim, tenure professor,
research fields: machine tools, dynamics and metal cutting. E-mail: [email protected].
relationship between the rotational speed and the depth of cut of the spindle [2]; this is the most fundamental theory. However, because it requires extensive parameters to be applied in the practical industrial field, it is not often used. Thus, in the present research, stable and unstable areas are not determined according to the lobe diagram [3]. Instead, this research aims to easily apply the stable cutting condition through the chatter frequency only when chatter vibrations occur so that chatter vibration can be prevented [4]. The purpose of this study is to develop a virtual dynamic system that proposes a virtual condition to analyze the signal characteristics when chatter vibration occurs during processing and to prevent chatter vibration by using lab view.
2. Virtual Dynamic Machining System
A VDMS (Virtual dynamic machining system) was developed to precisely detect chatter vibration that occur during processing, and to effectively reduced it.
In existing research on chatter vibration, numerous variables have been used to generate a model that is similar to practical chatter vibration [5].
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However,the occurrensimplified vFig. 1. The six modules(Fast Fourieforce acquismodule, a module, andmodule. Inpare samplingedges. Spindthe detected chatter frequnecessary inspeed.
The strucVDMS is shmodule is asnotification modules areand detectedmodule locacutting forcmicrophone the specificaselected. That Position 6
Fig. 1 Flowc
R
, the present rnce of chatter variables. Flow
present progs: a data filteer transform)sition modulchatter vibrad a stable sput values reqg rate, spindledle speed is rfrequency is
uency. And thnput value for
cture of the fhown in Figs follows: Thand stable sp
e located at Pd frequency aated at Positce signal. is located at
ations of thehe impact exc6.
chart of VDMS
Real Time Cha
research focuvibration in rwchart of VD
gram consists er processing) analysis mle, an impacation occurrepindle speed quired for runne speed, and nrequired to des a tool passinhe number of r calculating t
front panel og. 2 and the he chatter vibrpindle speed Position 1. Thare marked ation 3 is for The FFT at Position 4, ae filter for thcitation test m
S process.
atter Vibratio
used on detecreal time by uDMS is show
of the followg module, a
module, a cutct excitation ence notificarecommendaning the prognumber of cutetermine wheng frequency cutting edgesthe stable spi
of the developosition of eration occurrerecommendahe input vari
at Position 2. determining
analysis moand at Positiohe signal canmodule is loc
on Control Sy
cting using wn in wing FFT tting test
ation ation gram tting ether or a
s is a indle
oped each ence ation iable The
g the dule on 5 n be cated
2.1
Trespimptestexcin one
Tfreqdamplacwasdammodoccillu
2.2C
Tdetefromthrotranthe ampdetedetecertthe knofreqquaexpscopnatuscopocctwoaxicha
ystem in High
Impact Excit
This module wponse data of pact hammer t data, the maitation moduthe two-dim
e-dimensionalThen, by usquency of thmping ratio δ,ces at which s ± 1/√2 [6]. mping ratio dule, which wurrence of chstrated in Fig
Chatter Detec
The developedermining them the microough the Dnsmitted to thfilter. The freplitude of tected by usinermine the frtain value, a tfrequency co
own that chaquency of antitatively esperiment, chatpe between aural frequencpe, the preliurred only w
o and a half al system. Bat ter freque
h Speed Millin
tation Test Mo
was operatedf the axial systand accelero
agnitude valule, and the ma
mensional arrl array. sing the peahe primary m, was calculathe amplitudeThe calculat
were deliverwas used to dhatter vibratiog. 3.
cting Method
d VDMS cone cutting signophone is cAQ (Data ahe FFT analyequency contthe analyzedng the peak requency thatthreshold val
ontent could btter vibrationthe axial s
stablished. Btter vibration
approximatelycy of the axiiminary expe
within the scopf times the nBased on thency fc was
ng
Module
d by loading ttem, obtainedmeter. Amon
ue was used iagnitude valuray was con
ak detector, mode was calated after estae of the naturted natural frred to the Fdesignate the on. The prepar
d Constructed
nducts FFT annal. The sig
conveyed to acquisition)ysis module tent that has thd microphondetector. Addt has an amplue was desigbe detected. Gn occurs neaystem, but ecause of the
n occurred ony two and a hial system. Beriment, chatpe between apnatural frequhis scope, ths establishe
the excitationd by using theng the impactin the impactue configurednverted to a
the naturallculated. Theablishing tworal frequencyrequency andFFT analysis
scope of thered module is
d Module
nalysis whilenal obtainedthe VDMS
) board andafter passinghe maximumne signal isditionally, tolitude over a
gnated so thatGenerally, it isar the natural
nothing ise preliminarynly within thehalf times theBased on thistter vibrationpproximately
uency of thehe scope ofed by using
n e t t d a
l e o y d s e s
e d S d g
m s o a t s l s y e e s n y e f g
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Fig. 2 Front
Fig. 3 Block
the natural fin the impacdefined by u
Next, an content of tinputting thdetected in
R
t panel of VDM
k diagram of im
frequency fn, ct excitation tusing:
fn/2 <algorithm
the tool passhe spindle sthe FFT ana
Real Time Cha
MS.
mpact excitatio
of the axial sest module, a
< fc < 2fn that remove
sing frequencspeed value. alysis module
atter Vibratio
on test module.
system calculand the result
es the harmcy was added
The frequee falls under
on Control Sy
.
lated was
(1) monic
d by ency r the
scopthe freqas calcproare oneandthe opeaxiaaccmagmodtwoonedetewasaftethe natuthe the
ystem in High
pe of Eq. (1)threshold. Th
quency, not tthe chatter
culating the pcessed as fol
FFT cone-dimensionald magnitude.
maximum aerated by loadal system, obtelerometer. gnitude valudule, and the
o-dimensionale-dimensionalector, the nas calculated. er establishing
natural frequural frequencFFT analysisscope of the
h Speed Millin
and has the mhe frequency cthe harmonicr frequency.present proceslows. The signverted anl array after bAmong the
amplitude is ding the excittained by usinAmong thee was used e magnitude l array wl array. The
atural frequenThe dampin
g two places uency was ± cy and dampins module, whe occurrence
ng
maximum amcontent of the
c content, wa. The progss is shown ingnals that pasnd inserted being separatesignals, the detected. Thtation responsng the impact impact tesin the impavalue confi
was converen, by usinncy of the prng ratio δ waat which the 1/√2 [5]. Th
ng ratio werehich was used
of chatter vi
223
mplitude overe tool passingas establishedgram sourcen Fig. 3 and isssed the filter
into theed into f0, df,frequency of
his module isse data of thet hammer andst data, the
act excitationgured in therted to ang the peakrimary modeas calculatedamplitude ofhe calculatede delivered tod to designateibration. The
3
r g d e s r e , f s e d e n e a k e d f d o e e
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Real Time Chatter Vibration Control System in High Speed Milling
224
prepared module was illustrated in Fig. 2. through the peak detector and compared with the input machining speed to determine whether it was a tool passing frequency. Then, after confirming whether it occur near the natural frequency, the result was presented through the chatter vibration in the comparison operator. The chatter frequency detected in this process was conveyed to the indicator, which indicated whether chatter vibration had occurred. Additionally, the detected chatter frequency was used in the calculation of stable spindle speed, and the damping ratio δ required in this process is the value obtained by the impact excitation test module. The relationship between the chatter frequency fc and stable spindle speed N, which is calculated by Eq. (2) [7].
N = 60fc / (i(1 + δ)nt) (2) N: Stable cutting speed (revolution per min). fc: Chatter vibration frequency. i: Lobe number. δ: Damping ratio. nt: Number of cutting tool edge.
2.3 Cutting Force Acquisition Module
The cutting signal determined by the cutting force acquisition module is displayed in a graph in two ways: moving average method and resultant force method of each component of force. Resultant force FR is calculated through the component of force in the tri-axis direction, according to Eq. (3). When chatter vibration occurs, the resultant force largely increases compared to the stable machining; thus, the credibility of the chatter vibration detection is measured by using the size of the resultant force.
FR = (Fa2 + Fr2 + Ft2)1/2 (3) FR: Resultant force. Fa: Axial force. Fr: Radial force. Ft: Tangential force. The module is prepared to add a scale input, which is
the software amplifier, to the program, in addition to
the hardware amplifier of the cutting signal.
3. Experimental Setup
3.1 Impact Test Setup
Because the chatter vibration evasion process of the present research is conducted under the mechanism of detecting chatter vibration through the natural frequency of the axial system, it is prioritized to identify the dynamic characteristics of the axial system.
The impact hammer underwent excitation by using Type 8206-002 from Bruel & Kjaer, and an accelerometer obtained a response signal by using Type 4384 from Bruel & Kjaer. In the case of the shock excitation test, the proficiency of the experimenter largely affects the result; thus, the frequency response was obtained through 10 mean value calculations by using only the experimental data, which features the credibility of the coherence function.
A schematic diagram of the experiment equipment is shown in Fig. 4.
3.2 Cutting Experimental Setup
The present experiment was conducted at the MAKINO V55 tri-axis machining center. Regarding the signal during the cutting, data similar to the accelerometer were gathered, and for the sake of convenience in usage and signal measurement, the data were obtained by using the microphone (Bruel & Kjaer, Type 4189). Additionally, the distance between the areas at which the sensing and machining occurred was fixed at approximately 400 mm. The cutting force was obtained by using a Kistler 9257B-type dynamometer, and a Kistler 5019B130-type amplifier was used. The machined material was AISI 1045; the form of the machined product featured a low slenderness ratio, and thus, was machined to a bulk type so that vibration could not occur. Cutting fluid was not used here, and the filter used in determining the signal was a bandpass-type windowed FIR filter. The band was within 100 Hz to 5,000 Hz. The UT coating end mill from Unimax was used as the tool.
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Fig. 4 Block
Fig.5 Front
There were tThe length oestablished alonger, so theasily. The mand the sche
4. Results
4.1 Results o
In the cas
R
k diagram of F
panel of VDM
two cutting eof the tool inat approximahat chatter vibmachining conematic diagram
of the Impact
se of VDMS,
Real Time Cha
FFT module.
MS.
edges with dianstalled in theately 55 m, wbration couldnditions were m was shown
Excitation Te
the peak wa
atter Vibratio
ameter of 10 e tool holder
which was sligd occur relati
listed in Tabn in Fig. 6.
Test
as obtained at
on Control Sy
mm. was
ghtly ively le 1,
t the
Tab
SpiDepRadFeeCut
Fig.
pointestindithe grapfreqin th1,40.04deteto 2
4.2
Awheincrconspecutcondepwasof tthe
ystem in High
ble 1. Cutting
indle speed pth of cut (mm)dial of cut (mmed rate (mm/mintting method
.6 Experimen
nt of the inflet data; thus, iticated in Fig. impact test wph tool and quency, calcuhe impact exc16 Hz, and th41. The scopected through2,832 Hz.
Cutting Forc
As indicated en chatter vibrease compar
ndition. The ced of 5,830 Rting force o
nditions of 5,pth of cut, ws more than tthe stable mac
introductor
h Speed Millin
g conditions.
5,00) 1.0
m) 3.0 n) 1,00
Slot
ntal setup.
ection of magt was display7. The undis
was confirmedwas shown
ulated by loadcitation test mhe damping rpe in which h natural freq
ce Analysis
in Fig. 9, thebration occursred to that uncutting force aRPM and deof 556 N w,000 RPM sp
where chatter two times larchining condry and end
ng
00 513
00 1cutting
gnitude amoned in a distortorted magnitd through the
n in Fig. 8. ding the expermodule of theratio was calcthe chatter v
quency was w
e size of the s appeared to nder the stablaveraged 246epth of cut of
was measurepindle speed
vibration ocrger than the dition. The cu
portions of
225
,830 .0 .0 ,135
ng the impactrted graph, astude graph ofe Origin Pro*
The naturalrimental data
e VDMS, wasculated to be
vibration waswithin 703 Hz
cutting forceconsiderablyle machining
6 N at spindlef 1.0 mm. Ad under theand 1.0 mm
ccurred. Thiscutting force
utting force atf the cutting
5
t s f * l a s e s z
e y g e
A e
m s e t g
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226
Fig. 7 Impa
Fig. 8 Impa
Fig. 9 Cutti
R
act test result o
act test result o
ng forces depe
Real Time Cha
f VDMS.
f Origin Pro*.
ending on cutti
atter Vibratio
ing conditions.
on Control Sy
.
ystem in Highh Speed Millinng
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Fig. 10 Fron
increased ow
4.3 Front Pa
To evaluaVDMS, whsignal, was machining condition.
Chatter v5,000 RPM condition is frequency wsound was confirmed thof the machthe chatter inspindle spefrequency.
Spindle sspeed, calcthe previorecommende15,164 RPM
R
nt panel of VD
wing to the sh
anel Verificat
ate the validihich was ope
determined to verify th
vibration ocand depth of described in
was 2,630 Hz,generated in
hat a chatter hined productndicator lighted was calc
speed of 5,83culated by thous conditied spindle speeM; thus, 5,830
Real Time Cha
DMS (spindle sp
hock from rot
tion of VDMS
ity of the chaerated after in real time
he front pa
ccurred at spf cut of 1.0 mmn Fig. 10. The
and a high-pn the air. Mmark appearet. When the t activated (reculated throu
30 RPM is thhe chatter fion. The ed was betwee0 RPM, whic
atter Vibratio
peed 5,000 RP
tation [9].
S
atter detectiothe microph
e during milanel under e
pindle speedm; this machine detected chpitched chatteMoreover, it ed on the surchatter occur
ed), and the stugh the dete
he stable spinfrequency unscope of
en 5,830 RPM ch was the clo
on Control Sy
M, depth of cu
on of hone lling each
d of ning atter
ering was
rface rred, table ected
ndle nder
the and
osest
valucon
Cof 5andsurfwhiTheandwhilighnot
4.4
Wchaof Vthe RPMwhia chof Vindi
ystem in High
ut 1.0 mm).
ue to 5,000 Rndition. Chatter vibrat5,830 RPM spd the chatter mface. The peaich is the fife front panel od unlike the frich chatter viht remained gappear.
Machining S
When chatteratter mark appVDMS to dist
surface obsM and depth ich chatter vibhatter mark wVDMS. The icated in Fig
h Speed Millin
RPM, was s
tion did not opindle speed mark did not
ak frequency dfth content oof this conditi
front panel unibration occugreen and the
Surface
r vibration opeared on thetinguish chattservation. Atof cut of 1.0 bration was g
was confirmesurface stat
g. 12, which
ng
elected as th
occur under thand 1.0 mm
t appear on tdetected heref tool passinion is illustrat
nder the condurred, the chae stable spind
occurred, a ce surface; thuter was confirt spindle spemm, the con
generated, thed, as shown
tus of this coshows one su
227
he machining
he conditionsdepth of cut,
the machinede was 470 Hz,ng frequency.ted in Fig. 11
ditions duringatter indicatordle speed did
cross-stripedus, reliabilityrmed througheed of 5,000ditions undere existence ofin the resultsondition wasurface where
7
g
s ,
d , . ,
g r d
d y h 0 r f s s e
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228
Fig. 11 Fron
Fig. 12 Ma5,000 RPM, d
Fig. 13 Ma5,830 RPM, d
the machinishaking left of 5,830 RPare shown ingenerated, bpassed throu
4. Conclus
In the pre
R
nt panel of VD
achined surfacdepth of cut 1.0
achined surfacdepth of cut 1.0
ing was incand right we
PM spindle spn Fig. 13. He
but a subtle tugh.
sions
esent study, a
Real Time Cha
DMS (spindle sp
ce of workpie0 mm).
ce of workpie0 mm).
consistent anere generatedpeed and 1.0 ere, the chatttrace appeare
a dynamic m
atter Vibratio
peed 5,830 RP
ece (spindle s
ece (spindle s
nd the marksd. The conditmm depth ofter mark was
ed where the
machining sys
on Control Sy
M, depth of cu
speed
speed
s of tions f cut s not tool
stem
hadreal
TdeteImpspevibrexpspinvibrexpvibrperfdurmac
Ac
T
Re[1]
ystem in High
ut 1.0 mm).
d been develol time and avoThe developeermine cuttinpact excitatioed recommenration detecti
periment. Chandle rotation ration freque
periment. Furtration was noformed even ing the machining speed
knowledgm
This research
ferences Jung, N. S.Vibration in 210-17.
h Speed Millin
oped that can oid it during ed program ng force andon test, chattendation. By uon was confiratter vibration
speed was ency generatethermore, it wot generated a
if the depthachining to d.
ments
was supporte
2008. “AnalMilling Proc
ng
detect chatterthe cutting prVDMS was d conduct Fer detection,
using this progrmed throughn was detectecalculated oed during thwas confirmeand stable mah of cut was
modify the
ed by Doosan
lytical Predicticess.” KSME m
r vibration inrocess. designed to
FT analysis,and optimal
gram, chatterh a machininged and stablenly with the
he machiningd that chatterachining wasnot reduced
e calculated
n Infracore.
ion of Chattermech. 33 (3):
n
o , l r g e e g r s d d
r :
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Real Time Chatter Vibration Control System in High Speed Milling
229
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