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Procedia Engineering 174 (2017) 1276 – 1282
13th Global Congress on Manufacturing and Management, GCMM 2016
Design of Cutting Head for Efficient Cutting Machine of Thinwalled Stainless Steel Pipe
Ju Yi,Yingping Qian*,Zhiqiang Shang,Zhihong Yan,Yang Jiao
The School of Mechanical Engineering of Hubei University of Technology,Wuhan 430000,PR China
Abstract
A stainless steel pipe cutting device,which is for the diameter of about 130 - 150mm and wall thickness of 1.2mm stainless steel
pipe,is mainly used for the auto vent pipe. The problems existing in the traditional cutting methods and the part of core cutting
head are comprehensively analyzed in this paper. A kinematic scheme based on double-blade symmetrical and planetary cutting
machine was proposed.This scheme solved the problems of stainless steel pipe in machining incision that were caused by uneven
force, shrinkage, verticality and smoothness. The cutting technology was of great significance to improve the production
efficiency,save energy consumption and enhance the competitiveness of industry in the international market . The pipe cutting
machine has high cutting precision,making it economically feasible.
© 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
© 2016 The Authors. Published by Elsevier Ltd.
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-review under responsibility of the organizing committee of the 13th Global Congress on Manufacturing and Management.
Peer-review under responsibility of the organizing committee of the 13th Global Congress on Manufacturing and Management
Keywords: Pipe cutting machine,Thin-walled stainless steel pipe, Planetary cutting
1. Introduction
The so-called thin-walled stainless steel is a kind of stainless steel pipe that the ratio of the wall thickness and
external diameter is not more than 6%. In recent years,the thin-walled stainless steel pipe has been deployed
increasingly wider in machinery industry. With the rapid development of modern machical manufacturing
industry,the requirement of production efficiency and machining accuracy on the steel pipe cutting production are
simultaneously increased.The fators that affect the precision of thin-walled parts are summarized as follows [1]˖
precision of machine tool,thermal deformation of the tool, deformation of the tool, tool wear and deformation of
workpiece. Due to the poor rigidity of the thin-walled stainless steel pipe and clamping deformation, the
deformation of the workpieces is the most important factor affecting the machining accuracy.The research object of
this paper is 409 ferrite stainless steel with wall thickness of 1.0 - 1.5mm and diameter of 75 -135mm,which is
* Corresponding author.
E-mail address: qianyp98@163.com
1877-7058 © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-review under responsibility of the organizing committee of the 13th Global Congress on Manufacturing and Management
doi:10.1016/j.proeng.2017.01.302
Ju Yi et al. / Procedia Engineering 174 (2017) 1276 – 1282
mainly used in automotive exhaust pipe.The device adopted the steel pipe fixed, double symmetric rotating cutting
scheme.During the process of rotary cutting,the blades played the role of mutual support,which ensured that the
cutting section was absolutely vertical without burr.The feed movement and the main transmission were respectively
realized by the eccentric gears fixed on the planet gears and the planet gears meshing with the sun gear. At the same
time, the device adopted the method of automatic feed to guarantee completely cutting.
Because of its high heat resistance , good performance and lower price, the phenomenon of replacing cast iron
with ferritic stainless steel pipe is being a new trend in selection of exhaust pipe [2]. In recent years,with the
attention to the global environmental issues, the requirements of automotive energy-saving environmental protection
and lightweight have been put forward continuously. Meanwhile, the improvement of the level of automobile
exhaust emission is increased continuously.The casting metal of traditional exhaust system can not meet the
requirements of production and processing.Therefore,the high-performance 409 stainless steel is widely used in
components of automotive exhaust system. In addition, the cutting methods of China's thin-walled steel pipe are
mainly wire cutting, grinding wheel cutting,etc [3]. The traditional methods of machining can easily cause
machining deformation,which will reduce the dimensional accuracy of parts and surface quality.Thus,it is
particularly important that researches on cutting method of thin-walled stainless steel pipe should be conducted.
2. The motion principle and basic structure of cutting machine
2.1. The motion principle of cutting method
The main function of the planet type tube cutting machine is to complete the cutting workpiece of different
dimension,and accomplish continuous cutting. The pipe cutting machine mainly consists of feeding device,
clamping device, cooling device and cutting head device.The research object of this paper is the most important
part--cutting head device.
The cutting motion of the pipe cutting machine mainly includes two sections:(1) Main movement. It causes the
cutting edge of the tool and the surface of its adjacent tool to cut excess material onto the workpiece and transform it
into cutting,which forming a new surface of the workpiece. (2)Feed movement.It’s an additional relative movement
between the tool and the workpiece provided for the machine or human and material resources, which cooperates
with the main motion to cut off the machining redundancy on the workpiece with the desired geometrical
characteristics successively or continuously. A lot of experimental evidences have revealed that metal cutting is a
process of cutting the excess metal layer from the surface of the workpiece through the cutting motion to form a
qualified machined surface. And this is similar to metal material by extrusion with plastic deformation resulting in
shearing slip of the deformation process. When the cutting metal layer moves closer to the cutting edge, it is
subjected to the positive pressure FN and the friction force F1 of the tool, resulting in elastic deformation and plastic
deformation [4,5].
There are several problems occurred in traditional cutting method as follows: the difficult clamping,the big
deviation of the cutting size and the low production efficiency and material waste. In order to solve the problems
above, it is necessary to break the traditional thought patterns and adopt the method of fixing the pipe with two
cutting tools rotating at the same time. That is to say, the main movement and feed movement are both completed by
the cutting tool, which is called the planetary cutting operation. Selection of two milling cutter can not only ensure
the geometric accuracy of stainless steel pipe but also enhance the cutting efficiency. As shown in Fig. 1, the tools
cut through the steel pipe firstly, and then rotated around the steel pipe to cut it through by rolling the walls of pipes.
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Fig. 1. Cutting principle of pipe cutting machine.
2.2. The basic structure of pipe cutting machine
As shown in Fig. 2, the planetary cutting machine is maily composed of clamping device, frame, cutter head,
hollow shaft and eccentric gears,etc. The steel pipe was clamped by the jig device. The gear drives with the
advantages of a constant instantaneous ratio, high transmission efficiency, compact structure and long service
life,which adopted in the leading orbital revolution of blades. The tool movement was mainly divided into three
steps: (1)The servo motor drived the tool rotation.The cutting speed can be adjusted automatically according to the
material and the diameter of the steel pipe.(2)The symmetrica cutters were driven by reciprocal linear movement of
feed-in device (eccentric gears) to fulfill the cutting action. (3) The cutters were driven to rotate with the hollow
shaft by means of the main drive motor.
Fig. 2. Appearance of cutting head
3. Transmission scheme
The motion scheme based on tool rotating and tube fixed was adopted in the pipe cutting machine for thin wall
stainless steel pipe. In order to improve the cutting efficiency, realize the stepless speed regulation and save the cost,
one servo motor was finally adopted to control the rotation, feed movement and planetary motion of the blade. As
shown in Fig. 3,the cutting tools were fixed in the planetary gears by the eccentric gears, so as the eccentric gears
completed the linear feed motion.The formulated transmission scheme of cutting machine was as follows: the sun
gear was used as driving member.,the planet gears were used as follower and the annular gear was used as fixed part,
namely the power was input from the sun gear and output from the planet gear.
Ju Yi et al. / Procedia Engineering 174 (2017) 1276 – 1282
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Fig. 3. Appearance of cutting head
3.1. Analysis of feed scheme
The feed motion of the cutter was accomplished by the eccentric gear fixed on the planetary gear. The steel pipe
was passed through hollow shaft before cutting. The axis of the steel pipe should be consistent with the axis of the
hollow shaft. After starting the motor, the cutting tool rotated around its axis.The power was transferred to the
planetary gear by the motor. Furthermore, the eccentric gear was driven by the planetary gear.Then the cutting tool
was driven to fulfill linear feed by eccentric gear. That was to say, the transmission chain of feed movement
was :motorėreducerėhollow shaftėsun gearėplanet gearėeccentric gearėtool.
As shown in Fig. 4, the planetary gear rotated around the sun gear. Therefore, The center point of the planetary
gear movement can be seen as rotating around the center O of the steel tube.The motion trajectory can be considered
as a circle. As the tool was fixed on the eccentric gear, The trajectory of the tool’s center point can be regarded as
the track of the eccentric gear whose motion consists of two parts: (1) Rotating around the center of the sun gear,
that was, to complete the revolution of the tool movement. (2) Rotation around the center of the planet gear, that was,
to complete the feed movement of the tool.The two parts can be synthesized to trajectory diagram of tool. Based on
Fig. 4, the trajectory of cutting tool can be seen as a wave line rotating around the center of the steel tube. When it
was approaching the center, the tool contact with pipe wall.And the cutting operation of the steel pipe was
completed.When it was removed from the center, the movement of cutter-shaft backstroking was completed. In
addition, the sun gear was rotating with hollow shaft to achieve the transection of revolution.And then the blade and
the clamping device was reset in turn to complete one cutting process of the steel pipe and prepare for the next
cutting.
Fig. 4. Trajectory diagram of the centers of planet gear and cutting tool
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3.2. Principle analysis of main motion
The revolving cutting part of the device was the core part of the pipe cutting machine. External gearing
cylindrical gear with the eatures of large transmission power, wide scope of application, high working reliability,
long service life and high transmission efficiency was selected in the main drive system . When the motor was
started, the movement was transmitted to the drive gear via the reducer.And then the driven gear was driven to do
circular motion. The driven gear was connected to the hollow shaft which joined with the sun gear by a key
connection.Then the rotation speed was transmitted to the planetary gear. Continually, the cutting tool connected
with the planetary gear was rotated around the pipe to do rotary motion.
The main kinematic chain was: servo motor ė gear transmission ė hollow shaft ė sun gear ė cutting tool. The
servo motor can automatically adjust the cutting speed according to the different pipe materials and pipe diameters.
And the cutting tool was in contact with the workpiece to achieve continuous cutting throughout the process. In
order to improve the productivity,the scheme that the feed motion was completed ahead of the revolution of cutting
was raised. That was, the cutting tool was squeezed into the pipe wall by an external force.And the plastic
deformation of the tube wall arose, resulting in shear slip deformation.Then the cutting tools achieved revolution
with the sun gear, the pipe was cut off by the revolution movement subsequently. After the completion of a circular
cutting action, the feeding mechanism accomplished the next cut automatically.And the cycle cutting was completed,
and so forth.
4. Characteristics of cutting head
Countering the problems existing in the processing equipment of pipe, such as low degree of automation, low
production efficiency , serious waste of materials and so on, a double-blade symmetrical planetary pipe cutting
machine was put forward. On this foundation, the principle of cutting was analyzed and a feasible scheme of main
motion and feed motion was proposed.
4.1. Cutting method of two - blade symmetrical planetary
A scheme of steel pipe fixed and cutting tool rotating was presented. The pipe was fixed to a self-centering
clamping device.Two blades was symmetrically arranged with the cutting head. During the process of rotary
cutting,the blades played the role of mutual support,which ensured that the cutting section is absolutely vertical and
without burr. The free deformation of the pipe can provide fundamental guarantee for follow-on welding work.
4.2. The cutting transmission was completed by the planetary gear
The feed movement and the main transmission were respectively realized by the eccentric gears fixed on the
planet gears and the planet gears meshing with the sun gear. The designed devices has the advantages of smaller
dimension of ap power transmission.Above all, the transmission efficiency and cutting precision is higher,which is
conducive to the production and processing.
4.3. Automatic feed control system
The cutting device was driven by a servo motor to ensure strong driving force. The transmission ratio between
the main drive and the feed motion can be strictly ensured with one motor.And the advantages and disadvantages of
the existing pipe cutting machine were analysed and concluded. The scheme of machining was proposed to meet the
design requirements.The full automation cutting system was achieved by drive system of CNC with centralized with
centralized control mode. The control method was easy to implement and operate. The utility model has good
manufacturability,thus improving the quality of parts.
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4.4. High speed steel (HSS) cutting tools
High speed steel (HSS) is a kind of high-alloy steel with alloying elements,such as tungsten, molybdenum,
chromium and vanadium [5]. It has high strength, toughness, hardness , wear resistance and high thermal stability.
The object of this paper is 409 stainless steel with the characteristics of high coefficient of thermal conductivity and
small coefficient of expansion. To ensure that the cutting tool can complete normal cutting without plastic
deformation, high speed steel (HSS) W6Mo5Cr4V2 with merits of small and homogeneous carbide distribution,high
bending resistance and good mechanical properties was selected.
5. Determination of the main parameters of cutting head
5.1. Determination of planetary gear parameters
The object of this double-blade symmetrical planetary pipe cutting machine is the ferritic stainless steel 409 with
diameter of 75-135mm and wall thickness of 1.0-1.5mm. The inner diameter of the hollow shaft shall be greater
than the maximum diameter of the pipe to ensure that the steel pipe was favourable to go across the hollow shaft.
Therefore the diameter of the hollow shaft was selected to be 140 mm. In view of the bending resistance of gear
teeth, the modulus was selected as 2.5mm in the standard modulus series of GB1357-78, namely,m=2.5mm. In order
to facilitate the meshing between the sun gear and the planetary gear, the diameter of the graduated circle of the sun
gear was selected as 300mm, namely, d1=300mm. The planetary gears played the role of main movement and feed
movement in the entire process of cutting head.The transmission ratio was taken as 2 in accordance with the
requirements of the enterprise, namely, i=2. So the diameter of graduated circle was taken as 150mm, namely,
d2(d3)=150mm.
5.2. Determination of annular gear parameters
From the properties of gear meshing,it can be obtained that: the pitch circle diameter of the internal gear was
selected as d4 = d1 + d2 + d3 = 600 mm. The modulus was also chosen to be 2.5 mm. From the cylindrical spur gear
formula d = m • z, the number of teeth was z4=240.
6. Conclusion
A new type of planetary tube cutter was designed on the basis of the advantages of existing pipe cutting machine
equipment. The tool path was analyzed and a feasible motion scheme was proposed.The symmetrical double-blade
cutting scheme not only played the role of automatic centering,but also ensured the quality of incision and improves
production efficiency. The device was compact in structure,which can improve the processing efficiency of the pipe,
save the cost of raw materials and reduce the reject rate. In addition, the use of high-speed steel cutting tools can
reduce the dust and noise of production process in line with the ideals of green environmental protection. The
feeding and cutting parts of the pipe cutting machine were combined,and the whole control part was centrally
controlled by the programmable controller.The man-machine communication pattern can complete automatic
operation instead of manual operation with high production efficiency economically feasible[9] .
Acknowledgements
This work was supported by the Science and Technology Support Program of Hubei
Province(No.2014BAA020) ,the Project of Education Department of Hubei Province(No.2015293) ,the Science and
Technology Project of Hubei Province(No.2013BHE003) and the State Key Lab. of Mold & Die
Technology,Huazhong University of Science and Technology of China(No.2010-P03).
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