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The Shapes of Teeth of Circular Saw Blade and Their Influence on its Critical Rotational Speed

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Abstract

The main problems during cutting with circular saw blade are inaccurate cut, low quality of surface, high level of noise. These adverse effects are related to oscillation of circular saw blade. This oscillation cause adverse effects not only on workpiece but also on tool. In some case the circular saw blade reaches the value of critical rotational speed which leads to its instability and cause the oscillation of blade which may leads to destruction of tool. So the reduction of the amplitude of oscillation is essential for removing the adverse effects. This paper deals about influence of shapes of teeth as a type of modification that has positive effect oncritical rotational speed of circular saw blade. The parameters of studied models of circular saw blade were 42 number of teeth and the height of teeth with slice from sintered carbide was 14 mm. The variable parameter was the ratio between surface of teeth and surface of teeth gap. In this study was used computer software Creo Parametric 1.0 for obtaining natural frequencies of studied models. This software uses in analysis finite element method (FEM). There were done some steps to idealize the models. For calculating static and dynamics natural frequencies of modelswere used modal analysis. The critical rotational speed was calculated from obtained results by Creo Parametric 1.0 and compared on 5 models of tool. © 2015, Mendel University of Agriculture and Forestry Brno. All rights reserved.
399
ACTA UNIVERSITATIS AGRICULTURAE ET SILVICULTURAE MENDELIANAE BRUNENSIS
Volume 63 46 Number 2, 2015
http://dx.doi.org/10.11118/actaun201563020399
THE SHAPES OF TEETH OF CIRCULAR
SAW BLADE AND THEIR INFLUENCE
ON ITS CRITICAL ROTATIONAL SPEED
Adam Droba
1
, Ján Svoreň
1
, Ján Marienčík
1
1
Department of Manufacturing Technology and Materials, Faculty of Environmental and Manufacturing
Technology, Technical University in Zvolen, T. G. Masaryka 24, 960 53 Zvolen, Slovak Republic
Abstract
DROBA ADAM, SVOREŇ JÁN, MARIENČÍK JÁN. 2015. The Shapes of Teeth of Circular Saw
Blade and Their Infl uence on its Critical Rotational Speed. Acta Universitatis Agriculturae et Silviculturae
Mendelianae Brunensis, 63(2): 399–403.
The main problems during cutting with circular saw blade are inaccurate cut, low quality of surface,
high level of noise. These adverse eff ects are related to oscillation of circular saw blade. This
oscillation cause adverse eff ects not only on workpiece but also on tool. In some case the circular
saw blade reaches the value of critical rotational speed which leads to its instability and cause
the oscillation of blade which may leads to destruction of tool. So the reduction of the amplitude of
oscillation is essential for removing the adverse eff ects. This paper deals about infl uence of shapes
of teeth as a type of modifi cation that has positive eff ect oncritical rotational speed of circular saw
blade. The parameters of studied models of circular saw blade were 42 number of teeth and the height
of teeth with slice from sintered carbide was 14 mm. The variable parameter was the ratio between
surface of teeth and surface of teeth gap. In this study was used computer so ware Creo Parametric
1.0 for obtaining natural frequencies of studied models. This so ware uses in analysis fi nite element
method (FEM). There were done some steps to idealize the models. For calculating static and dynamics
natural frequencies of modelswere used modal analysis. The critical rotational speed was calculated
from obtained results by Creo Parametric 1.0 and compared on 5 models of tool.
Keywords: circular saw blade, modal analysis, natural frequency, critical rotational speed, FEM
INTRODUCTION
The main problems during cutting with circular
saw blade are inaccurate cut, low quality of surface,
high level of noise. These adverse eff ects are related
to oscillation of circular saw blade. This oscillation
cause adverse eff ects not only on workpiece but
also on tool. In some case the circular saw blade
reaches the value of critical rotational speed which
leads to its instability and cause the oscillation of
blade. which may leads to destruction of tool. So
the reduction of the amplitude of oscillation is
essential for removing the adverse eff ects (Svoreň,
2011). In the present circular saw blades are
constructed with variable modifi cations of body
– variable types of slots. These modifi cations are
aimed to reducing or eliminating adverse eff ects. So
this paper deals about infl uence of shapes of teeth
as a type of slot that have positive eff ect on critical
rotational speed of circular saw blade.
The phenomenon of oscillation was subject in
many scientifi c publications and for its reduction
were used any types of modifi cations of tool. It could
be excepted that teeth gap could be considered
as a type of slot and has an infl uence on natural
frequencies either statics or dynamics. In the past
the research based on diff erent types of slots, natural
frequencies and critical rotational speed was subject
in many scientifi c papers (HolØyen, 1987; Mote,
1965; Nishio and Mauri, 1996; Schajer and Mote,
1983; Yu and Mote, 1987; Svoreň, 2011; Stachiev,
1970; Veselý et al., 2012)
In the paper is used the fi nite element method.
Its applicationon oscillation and determination of
the natural frequencies of circular saw blade was
research area of many authors (Gogu, 1988; Leopold
and Münz, 1992; Michna and Svoreň, 2007; Ekevad
et al., 2009; Droba, Paulíny and Svoreň, 2013).
400 Adam Droba, Ján Svoreň, Ján Marienčík
The aim of this paper is to demonstrate
the infl uence of shapes of teeth on critical rotational
speed and design the model of circular saw blade
with the highest critical rotational speed with
respect of given parameters.
MATERIALS AND METHODS
The subjects of research were models of circular
saw blades with 42 teeth and the height of teeth with
slice from sintered carbide was 14 mm. Additional
static parameters of models are shown in Tab. I.
The variable parameter was the ratio between
surface of teeth and surface of tooth gap that is
shown in Tab. II. There were created 5 models of
blades with these parameters.
The geometry of tooth (angles – , , ) was in all
cases the same, ratio between gap and teeth was
achieved by variable angle as shows Fig. 1.
The models of circular saw blade have unbalanced
pitch, repeating a er 1/6 of circle. In the body of
circular saw blade were created two types of slots for
increasing the natural frequencies (Svoreň, 2011).
In this study was used computer so ware Creo
Parametric 1.0 for obtaining natural frequencies of
studied models. This so ware uses in analysis fi nite
element method (FEM). There were done some
steps to idealize the models.
Idealization
• Material;
• Mass defi nition;
• Constrain;
Density of mesh;
Type of elements.
For calculating static and dynamics natural
frequencies of models were used modal analysis.
The rotational speed in dynamic modal analyse
was n = 3600 min
−1
.The critical rotational speed
was calculated from results calculated by Creo
Parametric 1.0 on 5 models of tool.
For calculating centrifugal coeffi cient was used
equation (1) and the critical rotational speed was
calculated from equation (2). Both equations were
defi ned by (Mote, 1965; Nishio and Mauri, 1996):




stat
dyn
n
ff
2
22
60
, [Hz] (1)
stat
k
f
n
k
2
60
, [min
−1
] (2)
f
dyn
.....natural frequency of rotating circular saw
blade [Hz],
f
sta
.....natural frequency of non-rotating circular saw
blade [Hz],
n .......rotational speed [min
−1
],
k .......number of nodal diameters,
.......centrifugal coeffi cient,
n
k
......critical rotational speed [min
−1
].
I: Static parameters of model
Outer diameter [mm] 350
Inner diameter [mm] 30
Outer diameter of collars [mm] 110
Number of teeth [-] 42
Thickness [mm] 2.4
Height of teeth [mm] 14
Pitch of teeth Unbalanced
II: Variable parameter of shape of teeth
Surface of teeth Surface of teeth gap
CSB1
50 50
Ratio
[%]
CSB2
55 45
CSB3
52.5 47.5
CSB4
47.5 52.5
CSB5
45 55
1: Geometry of the tooth
2: Model of CSB5 used in modal analyses
The Shapes of Teeth of Circular Saw Blade and Their Infl uence on its Critical Rotational Speed 401
RESULTS AND DISCUSSION
The critical rotational speed was calculated for
5 models of circular saw blade. As a results from
modal analysis were obtained values of static
and dynamic natural frequencies of 5 models
of circular saw blades for k = 1, 2, 3, 4 which are
shown in Tabs. III and IV and graphical results of
displacement of models (for CSB1 is shown on
Fig. 3).
The obtained values of natural frequencies were
used for calculating centrifugal coeffi cients from
equation (1) and these results are shown in Fig. 4.
There were calculated values of critical rotational
speed for nodes k = 2, 3, 4 for each studied model
from equation (2). As the results show it was
decreasing dependence of critical rotational
speed from model with largest teeth gap to model
with smallest teeth gap. So the model with largest
teeth gap (CSB5) had the highest values of critical
rotational speed for all nodes. The lowest values
of critical rotational speed for all nodes had model
with the smallest surface of teeth gap (CSB2). So
it has been demonstrated that teeth gap could be
considered as a kind of slots and the tool with higher
proportionof teeth gap achieved higher critical
rotational speed than tool with lower(larger surface
of teeth than teeth gap). The infl uence of shapes of
teeth on critical rotational speed is shown in Fig. 5.
In the paper were used special types of slots
because of additional reduction of adverse eff ects
during sawing which was demonstrated by (Svoreň,
2011).
III: Values of the static natural frequencies of models for k = 1, 2, 3, 4
k
1234
CSB1
135.6 157 219.2 342.5
f
stat
[Hz]
CSB2
134.3 155.6 217.3 338.74
CSB3
134.7 156 218 340
CSB4
136.4 158 220.7 344.9
CSB5
137.3 159 222.4 347.44
IV: Values of the dynamic natural frequencies of models for k = 1, 2,
3, 4
k
1234
CSB1
156 180 241.45 361.94
f
dyn
[Hz]
CSB2
154.9 178.6 239.68 358.4
CSB3
155.32 179.1 240.26 359.4
CSB4
156.78 180.88 242.8 364.3
CSB5
157.58 181.84 244.4 366.78
3: The results of deformed model CSB5 from modal analyse for k = 2
1.50
1.80
2.10
2.40
2.70
3.00
3.30
3.60
3.90
4.20
CSB1 CSB2 CSB3 CSB4 CSB5
CentrifugalcoefficientȜ
k=1
k=2
k=3
k=4
4: Calculated centrifugal coefficient of 5 models
402 Adam Droba, Ján Svoreň, Ján Marienčík
CONCLUSION
The infl uence of shapes of teeth of circular saw blade on critical rotational speed was analysed using
pc so ware and equations defi ned by (Mote, 1965; Nishio and Mauri, 1996; Svoreň, 2011). Five models
of circular saw blades with variable ratio between teeth gap and surface of teeth were analysed on
which was demonstrated this infl uence.It has been shown that for achieving higher values of critical
rotational speed is better design the tool with larger teeth gap than surface of teeth. Using pc so ware
is in present very helpful in research while the properties of real tool are correctly defi ned on model.
It is necessary to do some idealizations on models. It has been shown that is better to created circular
saw blades with larger teeth gap than surface of teeth for obtaining higher critical rotational speed of
tool.
5: Comparison of calculated values of critical rotational speed of all models
REFERENCES
DROBA, A., PAULÍNY, D., SVOREŇ, J., 2013.
Porovnanie teoretických a experimentálnych
hodnô tvlastných frekvencií pílového kotúča. Acta
facultatis technicae, 18(1): 39–46.
EKEVAD, M., CRISTOVAO, L., GRÖNLUND, A.
2009. Diff erent methods for monitoring fl atness
and tensioning in circular – saw blades. In:
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Nanjing, 21.–23. October 2009. Jiangsu, China.
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GOGU, G. 1988. Berechnung der Eigenfreguenzen
von Kreissägeblätternmit der Finite-Element-
Methode. Holz als Roh- und Werkstoff , 46(3): 91–100.
HOLØYEN, S. 1987. Vibrations and natural
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Roh- und Werkstoff , 45: 101–104.
LEOPOLD, J., MÜNZ, V. V. 1992. Dynamische und
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mittels der Finite-Elemente-Methode. Holzbearbei-
tung, 6: 52–56.
MICHNA, S., SVOREŇ, J. 2007. Application of CAD,
CAE with FEM for estimation ranges of values of
critical rotational speed of circular saw blades. Acta
Facultatis Technicae, 9(1): 201–206.
MOTE, C. D. 1965. Free Vibration of Initially Stressed
Circular Disk. Journal of Engineering for Industry, 5:
258–264.
NISHIO, S., MARUI, E. 1996. Eff ects of Slots on
Lateral Vibration of Circular Saw Blade. In:
Proceedings of Tenth Wood Machining Seminar, 159–
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SCHAJER, G. S., MOTE, C. D. 1983. Analysis of
roll tensioning and its infl uence on circular saw
stability. Wood Sci. Technol., 17(4): 287–302.
SVOREŇ, J. 2011. The analysis of the eff ect of the
number o teeth of the circular-saw blade on the
critical rotation speed. In: 4
th
International Scientifi c
Conference – WOODWORKING TECHNIQUE,
2011. Prague, Czech Republic, 306–313.
The Shapes of Teeth of Circular Saw Blade and Their Infl uence on its Critical Rotational Speed 403
STACHIEV, J. M. 1970. Rezonansnyje kolebanija
diskovych pil. Izv.VUZ. Lesnoj žurnal, 13(5): 78–84.
VESELÝ, P., KOPECKÝ, Z., HEJMAL, Z., POKORNÝ,
P. 2012. Diagnostics of circular saw blade vibration
by displacement sensors. Drvna Industrija, 63(2):
81–86. DOI: 10.5552/drind.2012.1130.
Contact information
Adam Droba: adam.droba@gmail.com
Ján Svoreň: svoren@tuzvo.sk
Ján Marienčík: jmariencik@gmail.com
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Porovnanie teoretických a experimentálnych hodnô tvlastných frekvencií pílového kotúča
  • A Droba
  • D Paulíny
  • J Svoreň
DROBA, A., PAULÍNY, D., SVOREŇ, J., 2013. Porovnanie teoretických a experimentálnych hodnô tvlastných frekvencií pílového kotúča. Acta facultatis technicae, 18(1): 39-46.
Application of CAD, CAE with FEM for estimation ranges of values of critical rotational speed of circular saw blades
  • MICHNA
MICHNA, S., SVOREŇ, J. 2007. Application of CAD, CAE with FEM for estimation ranges of values of critical rotational speed of circular saw blades. Acta Facultatis Technicae, 9(1): 201-206.
Rezonansnyje kolebanija diskovych pil
  • J M Stachiev
STACHIEV, J. M. 1970. Rezonansnyje kolebanija diskovych pil. Izv.VUZ. Lesnoj žurnal, 13(5): 78-84.