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This article deals with the influence of some cutting parameters (geometry of cutting edge, wood species, and circular saw type) and cutting conditions on the wood crosscutting process carried out with circular saws. The establishment of torque values and feeding power for the crosswise wood cutting process has significant implications for designers of crosscutting lines. The conditions of the experiments are similar to the working conditions of real machines, and the results of individual experiments can be compared with the results obtained via similar experimental workstations. Knowledge of the wood crosscutting process, as well as the choice of suitable cutting conditions and tools could decrease wood production costs and save energy. Changing circular saw type was found to have the biggest influence on cutting power of all factors tested.
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Krilek et al. (2014). “Crosscutting analysis,” BioResources 9(1), 1417-1429. 1417
Wood Crosscutting Process Analysis for Circular Saws
Jozef Krilek, Ján Kováč,* and Marián Kučera
This article deals with the influence of some cutting parameters
(geometry of cutting edge, wood species, and circular saw type) and
cutting conditions on the wood crosscutting process carried out with
circular saws. The establishment of torque values and feeding power for
the crosswise wood cutting process has significant implications for
designers of crosscutting lines. The conditions of the experiments are
similar to the working conditions of real machines, and the results of
individual experiments can be compared with the results obtained via
similar experimental workstations. Knowledge of the wood crosscutting
process, as well as the choice of suitable cutting conditions and tools
could decrease wood production costs and save energy. Changing
circular saw type was found to have the biggest influence on cutting
power of all factors tested.
Keywords: Circular saw; Cutting power; Torque; Cutting edge geometry
Contact information: Technical University in Zvolen, Faculty of Environmental and Manufacturing
Technology, Department of Forest and Mobile Technology, T. G. Masaryka 24, 960 53 Zvolen, Slovakia;
*Corresponding author: kovac@tuzvo.sk
INTRODUCTION
Crosscutting of wood is often used during the exploitation of forest resources. It is
used to cut down trees, shorten trunks, and produce assorted wood products. Research
performed regarding the optimum wood machining conditions (Eyma et al. 2004;
Méausoone 2001) has shown that there are generally three basic factors affecting the
cutting process: factors attributed to the device, factors associated with wood species, and
the moisture content of the wood.
Factors that are considered to have a significant effect on the torque are the depth
of cut, the rake angle, and the edge radius. The torque increases with depth of cut,
increases with edge radius, and decreases with rake angle. Furthermore, cutting the wood
end grain yields the largest torque, while the lowest is observed when cutting along the
fiber direction. Work-piece parameters have been used as predictors in statistical
modeling to describe torque trends. Often used parameters are density, moisture content,
and grain direction. The density does not dramatically change with respect to moisture
content as a result of this change in volume. It is generally accepted that tool forces
decrease with increasing work-piece moisture content, although an exception to this rule
has been found for frozen wood samples. Increased moisture content for frozen wood
leads to an increase in tool forces. Furthermore, work-pieces at decreasing sub-zero
temperatures are subject to increasingly higher tool forces.
The reason torque increases with increasing cutting speed is that the feed per tooth
decreases and the chip thickness consequently decreases. It is known that cutting
resistance is greater for small chip thicknesses; as a result, the torque increases when the
chip thickness decreases (Barcík et al. 2008).
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A tool is considered worn when the wedge has reached a critical state
accompanied by an intolerable degradation in quality of the work-piece surface, an
undesirable increase in cutting power, burning, or dimensional inaccuracy of the work-
piece (Šustek and Siklienka 2012). In this study, extensive and accurate measurements
and evaluations of torque in various types of solid wood were carried out. The results
obtained can help in dimensioning the machine and tool equipment of dimension saws
and at the same time, in optimizing technological conditions of machining in order to
prevent unnecessarily high energy consumption and damage to machines and tools
(Kopecký and Rousek 2005).
THEORETICAL BACKGROUND
Crosscutting Wood with Circular Saws
Figure 1 shows the reciprocal relations between wood and the cutting wedge
generated when wood is penetrated by the tooth of a circular saw (Kováč and Mikleš
2010). The cutting wedge presses on the resisting wood. The result is a load on the
frontal, rounded, and back surfaces of the cutting wedge. The cutting resistance is created
as the chip is separated by the wedge. The cutting resistance is a reaction to the cutting
force; it has the same size but is in the opposite direction.
Fig. 1. Illustration of a circular saw cutting wood: fz feed per one tooth [m.s-1], ae cutting
height [m], vf feeding speed [m.s-1], vc cutting speed [m.s-1], ψ1 incoming angle of a circular
saw [°], ψ2 outgoing angle of a circular saw [°], φm mean angle of cutting fibres [°], hm mean
thickness of a chip [mm]
The resistances acting against the cutting wedge of a circular saw tooth can be
summed as one resultant force F, the cutting resistance. F consists of the following:
forces necessary for cutting a work piece using a cutting wedge via deformation
of the piece surrounding the cutting edge,
forces necessary for the deflection of chips and the overcoming of the chip’s
friction against the leading edge of the tooth, and
forces necessary for suppression of friction on the back and leading surfaces in
contact with the machined surface.
Defining the values of individual parts of the force F is quite difficult and depends
on many factors. The component of the force F in the direction of cutting feed is called
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the cutting force and is used for practical calculations of energy expenditure during the
cutting process.
The cutting force F on a tooth of a circular saw acts on chips of width b and
thickness h regarding to the cutting resistance for disintegrated material K:
c
f
v
vhbK
F.60
...
[N] (1)
The cutting power Pc is defined as the product of cutting force F and cutting speed:
1000
C
cvF
P
[W] (2)
It is also possible to calculate the cutting power Pc via torque Mk, and the diameter
of a circular saw D as:
D
vM
Pck
c
2
[W] (3)
Cutting Conditions during Woodcutting Performed by Circular Saws
Modern circular saw blades for crosscutting wood-based materials are equipped
with various adjustable components (Vesely et al. 2012). The following are types of
circular saws, classified by the shape of their cut: flat, relieved, concurrent, and saddle.
They differ in tooth profile and the method of sharpening. The tooth profile and the
method of sharpening depend on the required performance of the saw and the required
quality of the machined surface. They must be varied according to the type of work piece
(soft/hard wood and other types of work pieces) and the material of the cutting edge (tool
steel/cemented carbide plates).
On each circular saw, there is marked a maximum revolution speed of 100 m.s-1.
This speed is not the maximum functional speed; instead, it represents the maximum
operationally reliable speed guaranteed by a producer. To achieve the optimal
performance of a circular saw, it is necessary to choose cutting conditions based on the
material to be cut. The recommended cutting speeds for circular saws are 60 to 100 m.s-1
for softwood and 50 to 85 m.s-1 for hard and exotic wood.
The recommended cutting speed for a chosen material depends on the
requirements of cutting surface quality, the technological state of the machine, and other
factors. Deviating from the recommended cutting speed is economically impractical.
Circular saws are used in the manipulation of trunks with diameters in the range between
400 and 500 mm. Their advantages include a high cutting ability, maintainability, and
long lifetime.
In practice, it is important to carry out the whole cutting process with the lowest
energy consumption possible. Many factors influence torque, including the choice of a
suitable cutting tool material, its geometry, and the optimal cutting conditions (cutting
speed vc and feeding speed vf). The cutting power is a very important factor affecting
energy consumption. The cutting-wedge angle β determines the performance of a tool
and a machine, machined surface quality, and dimensional exactness of a work piece.
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When the cutting-wedge angle, (i.e., the angle of the cutting part of a tool)
increases, the cutting resistance of a material also increases. Cutting resistance is lowest
when the cutting angle is as small as possible, but when the cutting angle is under a
certain value, the hardness of a cutting edge is very low and it quickly wears out. To
define a cutting-wedge angle, there must be defined values of the angles α and γ.
Friction between the cutting surface and the processed surface influences the
cutting clearance angle, α. When this angle is small, the friction is high. This effect is
caused by decreasing the cutting clearance angle between the cutting clearance and the
processed surface directly behind the cutting edge. This surface gradually increases with
higher wear of the cutting edge because a rounded, worn cutting edge does not cut
material efficiently. It is mainly in the plane passing the lowest point of a cutting edge
but it is also in the plane lying a little bit higher. The cutting clearance angle has direct
influence on the dimension of cutting resistance and the work required to cut a piece.
Typically, the cutting clearance angle is between 10 and 30°.
The cutting-edge side rake influences the chip creation process and the size of
chips. The optimal value also depends on the type of processed material, direction of
fibers, and dimension of feed on the piece’s edge or the thickness of a chip.
EXPERIMENTAL
Materials and Methods
The experimental measuring device was developed for studying crosswise
woodcutting parameters performed mainly by circular saws. It is shown in Fig. 2 (Kováč
and Mikleš 2009). The measuring equipment consists of a cutting and a feeding part. The
cutting part provides energy and transfers torque to a circular saw. The feeding part
provides work to clamp the wood down and feed it into the cutting part.
Fig. 2. Illustration of the experimental measuring device: 1 - a working table, 2 - a sliding line, 3 -
a trunk of round timber, 4 - belts to drive the circular saw, 5 - an electric engine to drive the
circular saw, 6 - a bearing cover, 7 - an electric engine to push the material to the cut, 8 - a
spindle head of a circular saw, 9 - a circular saw, 10 - a T20WN recording device for torque and
rotational speed, 11 - a GFLL-28 clutch, 12 - an S2 force recorder
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As shown in Fig. 2, there is a three-phased asynchronous 7.5 kW electric engine.
Its torque is transferred through the spindle head to a tool (circular saw). The wood
sample is held on the plate within the holder by a lever system. The crosswise feeding
force for of the work-piece is provided by a 5.5 kW electric engine with a safety clutch
and a feed screw. Between the nut and the plate, there is an HBM S2 force sensor. Cables
transfer measured force and torque signals to the SPIDER-8 measuring center, which is
connected to a PC. The HBM T20WN torque sensor measures the rotational speed of the
circular saw. Frequency converters with vector control regulate the rotational speed and
the power of the electric engines.
In the experimental tests, wood trunk freshly cut (green) samples with dimensions
of 150 x 150 mm and lengths of 1.5 m were used. The wood samples were prepared
directly before the measurement. The samples with the mentioned dimensions were cut
from the trunk at the diameter of 250 mm. The wood trunk samples were beech and
spruce. Their moisture was approximately 45% (spruce) and 50 to 60% (beech). The use
of these conditions is also supported by experimental work of Klement et al. (2010).
The samples were cut by circular saws with cemented carbide plates and with
high-speed steel blades. The used circular saws were designed in SolidWorks 3D CAD
solutions by authors of the paper and produced by STELIT, Ltd. The technical
parameters of the circular saws are shown in Table 1).
Table 1. Basic Parameters of Circular Saws
Basic dimensions
Diameter
of saw
D (mm)
Thickness
of saw
B (mm)
Cutting-
clearance
angle (°)
No. of
teeth
Circular saw made
of high speed steel
(HSS)
600
3.5
20
56
Circular saw made
of cemented
carbide plates
(CCP)
600
3.5
15
54
The material properties of circular saw blades according to grades are shown in
Table 2.
Table 2. Material Properties of Circular Saw Blades
Circular saw blade type
Material definition
Circular saw made of high speed
steel (HSS)
Grade
HS 18-0-1
EN ISO 4957 : 2000 - High-speed tool steel
Circular saw made of cemented
carbide plates (CCP)
Grade
ISO Code K20
All observed circular saw blades had convex construction of the clearance surface
of the circular saw blade teeth, concave construction of the rake surface of the circular
saw blade teeth, and concave construction of the side surface of the circular saw blade
teeth. More precise information about of the circular saw blade teeth for both types of
observed materials is shown in Figs. 3 and 4.
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Fig. 3. Teeth parameters for a circular saw blade made of cemented carbide plates (CCP)
Fig. 4. Teeth parameters for a circular saw blade made of high speed steel (HSS)
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The measurements for beech and spruce were performed at 1900, 2230, and 2550
min-1, with cutting speeds (vc) of 60, 70, and 80 m.s-1 and feeding speeds (vf) of 6, 8, 10,
and 12 m.min-1.
Every cutting test was performed 30 times for every observed item, i.e. each wood
species (beech and spruce), each type of a circular saw, and each cutting and feeding
speed. The thickness of the cutting layer (i.e. chip thickness) was the same for all circular
saws, and it was 5.4 mm.
One purpose of the experiments was to determine the influence of different
cutting-edge side rakes on the torque value and compressive force of the cut. The results
were analyzed in the CONMES SPIDER program.
RESULTS AND DISCUSSION
The cutting-edge side rake influences cutting resistance and therefore the whole
process of crosswise woodcutting. Figure 5 shows a great increase of measured value at
the beginning of the tool’s penetration of the wood, followed by a decrease as a result of
inertia of the circular saw and completion of the cutting process. Afterwards, the cutting
process runs at a constant value (the torque value is changed very little), only rotating
without any loading at the end of the process. The course of torque Mk during the cutting
process of circular saws made of high-speed steel (Fig. 6) is characterized by a rapid
increase to a maximum value, a small decrease to an intermediate value, and a rapid
decrease as the cut is completed.
Fig. 5. The course of Mk during the crosscutting process of beech sawn by a circular saw made of
cemented carbide plates with a cutting-edge side rake of 20°
The output of the experimental measurement represents measured values of
torque recorded during the experiment and are shown in Tables 3 and 4. Obtained values
are defined according to different criteria like wood species, cutting-edge side rake,
cutting speed vc, feeding speed vf, and mean torque values Mk. Mean torque values for
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individual feeding speeds were calculated from 30 measurements for individual feeding
speeds. Graphs were created on the basis of values worked out by ANOVA from the
previous measurements. Graphical and statistical evaluations are shown in Figs. 7, 8, 9,
and 10.
Fig. 6. The course of Mk during the crosscutting process of beech sawn by a circular saw made of
high speed steel with a cutting-edge side rake of 20°
The experiment was designed to consider three values of cutting angles (-5°, 0°,
and 20°) for evaluating cutting performance because there is thought to be a negative
value of cutting angle with the smallest values of Mk.
In Figs. 7 and 8 there is shown an influence of feeding speed vf on torque Mk in
the case of the circular saw blade type. It is clear from the graphs that feeding speed vf
did not exhibit significant influence on the torque Mk during evaluation of individual
cutting speeds vc.
Fig. 7. The influence of feeding speed vf on torque Mk for different wood species
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Table 3. Measured Values of Torque during Wood Crosscutting Process
Performed by Circular Saw Made of High Speed Steel (HSS)
No.
Wood
species
Cutting-
edge
side
rake
[°]
Cutting
speed
vc
[m.s-1]
Feeding
speed
vf
[m.min-1]
Mean
torque
values
Mk
[N.m]
No.
Wood
species
Cutting-
edge
side
rake
[°]
Cutting
speed
vc
[m.s-1]
Feeding
speed
vf
[m.min-1]
Mean
torque
values
Mk
[N.m]
1.
Beech
-5
60
6
15.805
37.
Spruce
-5
60
6
15.398
2.
8
14.825
38.
8
16.003
3.
10
14.712
39.
10
16.022
4.
12
15.002
40.
12
15.948
5.
70
6
18.173
41.
70
6
15.295
6.
8
14.91
42.
8
15.583
7.
10
14.158
43.
10
15.567
8.
12
14.405
44.
12
15.903
9.
80
6
14.845
45.
80
6
14.808
10.
8
15.122
46.
8
15.367
11.
10
14.603
47.
10
15.437
12.
12
14.515
48.
12
15.6
13.
0
60
6
15.605
49.
0
60
6
15.592
14.
8
15.612
50.
8
16.068
15.
10
15.185
51.
10
15.942
16.
12
15.338
52.
12
15.862
17.
70
6
16.477
53.
70
6
14.602
18.
8
16.198
54.
8
15.105
19.
10
16.378
55.
10
15.357
20.
12
16.012
56.
12
15.203
21.
80
6
14.478
57.
80
6
14.17
22.
8
15.18
58.
8
14.285
23.
10
15.203
59.
10
14.39
24.
12
15.745
60.
12
13.975
25.
20
60
6
15.367
61.
20
60
6
17.058
26.
8
15.663
62.
8
13.65
27.
10
15.617
63.
10
13.342
28.
12
15.715
64.
12
13.697
29.
70
6
17.083
65.
70
6
13.692
30.
8
16.655
66.
8
13.45
31.
10
16.79
67.
10
13.37
32.
12
15.768
68.
12
13.392
33.
80
6
15.888
69.
80
6
13.528
34.
8
15.555
70.
8
13.593
35.
10
15.575
71.
10
13.905
36.
12
15.347
72.
12
14.06
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Table 4. Measured Values of Torque during Wood Crosscutting Process
Performed by Circular Saw Made of Cemented Carbide Plates (CCP)
No.
Wood
species
Cutting-
edge
side
rake
[°]
Cutting
speed
vc
[m.s-1]
Feeding
speed
vf
[m.min-1]
Mean
torque
values
Mk
[N.m]
No.
Wood
species
Cutting-
edge
side
rake
[°]
Cutting
speed
vc
[m.s-1]
Feeding
speed
vf
[m.min-1]
Mean
torque
values
Mk
[N.m]
1.
Beech
-5
60
6
16.133
37.
Spruce
-5
60
6
14.967
2.
8
16.19
38.
8
15.627
3.
10
16.305
39.
10
15.39
4.
12
16.417
40.
12
14.985
5.
70
6
16.342
41.
70
6
14.968
6.
8
17.
42.
8
15.375
7.
10
17.28
43.
10
15.282
8.
12
17.168
44.
12
15.343
9.
80
6
16.277
45.
80
6
14.81
10.
8
16.38
46.
8
14.83
11.
10
16.702
47.
10
14.775
12.
12
16.748
48.
12
15.025
13.
0
60
6
14.802
49.
0
60
6
14.603
14.
8
16.47
50.
8
15.097
15.
10
16.412
51.
10
15.32
16.
12
18.413
52.
12
15.235
17.
70
6
16.015
53.
70
6
14.487
18.
8
16.658
54.
8
14.272
19.
10
16.5
55.
10
14.293
20.
12
16.922
56.
12
13.96
21.
80
6
16.163
57.
80
6
12.713
22.
8
16.248
58.
8
13.132
23.
10
16.775
59.
10
13.343
24.
12
16.668
60.
12
13.408
25.
20
60
6
15.963
61.
20
60
6
12.128
26.
8
15.933
62.
8
12.093
27.
10
15.883
63.
10
12.323
28.
12
15.95
64.
12
12.832
29.
70
6
15.297
65.
70
6
12.058
30.
8
15.51
66.
8
12.065
31.
10
14.478
67.
10
12.295
32.
12
14.828
68.
12
12.517
33.
80
6
14.883
69.
80
6
12.503
34.
8
15.303
70.
8
12.348
35.
10
15.077
71.
10
12.302
36.
12
14.758
72.
12
12.157
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Fig. 8. The influence of cutting-edge side rake on torque Mk for varying feeding speeds vf
Figures 9 and 10 present statistical dependency of torque Mk on the type of the
circular saw blade, wood species, cutting speed vc, and cutting-edge side rake.
In Fig. 9 it is clear that the values of torque measured in the case of spruce cut by
circular saw made of high speed steel (HSS) were higher than values of torque Mk
measured at beech cut by circular saw made of cemented carbide plates (CCP). This
difference was attributed to faster tool wearing.
Figure 10 shows the influence of circular saw blade type on the cutting-edge side
rake on torque Mk. This case represents the most suitable cutting-edge side rake angle,
having a value of 20°.
Fig. 9. The influence of circular saw type on torque Mk for different wood species
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Fig. 10. The influence of circular saw type on torque for different cutting-edge side rakes
The mentioned statistical evaluations of torque Mk for individual measurement
variables show that the most convenient cutting-edge side rake for crosscutting wood by
circular saw blades made of HSS and CCP is a positive value (20°). These results are
supported by other authors (Siklienka et al. 2013) and a tool producer PILANA Saw
Bodies, Ltd. (1999).
CONCLUSIONS
1. The cutting rake angle (e.g. 20o) of a circular saw is an important factor influencing
torque Mk.
2. Changing circular saw type (with the same geometry) had the biggest influence on
torque Mk of all tested factors.
3. Feeding speed vf has a significant influence on torque Mk. For deciduous wood, it is
more suitable to use a higher feeding speed at positive cutting angles. For coniferous
wood, it is more suitable to use slower feeding speeds due to the presence of reaction
wood.
4. According to the research, the cutting speed vc has more significant influence on
torque Mk in the cutting of spruce than beech. It is sure that torque Mk decreases when
cutting speed vc increases. This result was found to be valid for both observed types
of circular saw blades i.e. a circular saw made of high speed steel (HSS) and a
circular saw made of cemented carbide plates (CCP).
ACKNOWLEDGEMENTS
This article was created as a part of project VEGA No. 1/0403/11 named “The
Chain Saws Research of Technical Parameters Regarding to Ergonomics and Ecology
Work, by the Ministry of Education, Science, Research, and Sport of the Slovak
Republic.
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cutting output power by cross-cutting of beech wood, Aacta Facultatis Xylologiae
Zvolen 55(1), 91-99.
Šustek, J., and Siklienka, M. (2012). “Effect of saw blade overlap setting on the cutting
wedge wear, Aacta Facultatis Xylologiae Zvolen 54(1), 73-80.
Article submitted: November 11, 2013; Peer review completed: December 16, 2013;
Revised version received: January 16, 2014; Accepted: January 17, 2014; Published:
January 28, 2014.
... Cutting force behavior is also affected by cutting speed and feed rate. Krilek et al. mentioned that the cutting force increased with the increase of feed rate [14]. Schmidt et al. indicated that the increase of cutting force can be explained by the reduction of feed force. ...
... Krilek et a mentioned that the cutting force increased with the increase of feed rate [14]. Schmidt e al. indicated that the increase of cutting force can be explained by the reduction of fee force. ...
... Krilek et al. [14]. The influence of the interaction of various factors on the cutting force was shown in Figure 7. ...
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... When using forest resources, cross-cutting to a preliminary dimension is often used, such as when cutting trunks to planks and producing various wood products. Krilek et al. [1] report that lower values of cutting power were measured in the transverse cutting of prisms from (soft) coniferous tree species (spruce) than in the case of (hard) broadleaved tree species (beech). The face angle (γ = −5 • ; 0 • ; 20 • ) has a great influence on the cutting power. ...
... The bending properties were determined according to the STN EN 310 [42] and density according to the STN EN 323 [43]. Notes: (1) MOR is bending strength; (2) MOE is modulus of elasticity; (3) ko is coefficient of bendability; (4) 1/ko is unit coefficient of bendability. ...
... A lower coefficient of determination between the cutting power and the average chip thickness was achieved in the case of lightweight plywood compared to classic plywood using a circular saw blade CSB1 (r 2 = 82% and 90%). Equation (1) shows that in the case of both materials, an increase in the feed speed corresponds to an increase in the chip thickness, which results in higher cutting power. Average chip thickness, as a critical factor in the sawing process, significantly affects the cutting power. ...
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... Research on reducing energy consumption in wood processing machines is carried out by introducing innovations in cutting mechanisms [3][4][5], drives [6][7][8], or control system. The authors of [9] reported that lower values of cutting power were measured in transverse cutting of balks of coniferous (Spruce) than in deciduous wood (Beech). The rake angle (−5 • ; 0 • ; 20 • ) has a great influence on the cutting power. ...
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... These factors also affect measurement deviations (Sandak and Martino 2006). This statement fully corresponds with Krilek et al. (2014), Droba and Svoreň (2012) as well as Nasir and Cool (2019), who found that the design of the saw blade directly affects the force relationships in the cutting process, which is subsequently reflected in the quality of the created surface. ...
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... The wood cutting parameters (energy consumption, dust level, and noise level), the emerging product parameters (dimensional accuracy and created surface quality), and the produced chip parameters (dimensions and particle size composition) depend on the teeth shape, teeth dimensions and number, cutting tool geometry, sharpness, and technological conditions of the process, such as feed speed, feed force, and cutting speed (Barcík and Gašparík 2014;Krilek et al. 2014;Gaff et al. 2015;Kvietková et al. 2015;Gaff et al. 2016;Kminiak and Kubš 2016). ...
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... Higher cutting forces are registered with species having higher wood density, which also raises the energy consumption (Aguilera and Martin 2001). Further, higher torque values were recorded by Krilek et al. (2013) for beech during cross-sectional cutting. These findings are in coherence with the higher triboelectric charges obtained when cutting beech wood cross-sectionally. ...
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Basic characteristics of wood species -Wood processing in forestry
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