CC BY
7AUTOMATIC SLIVER SEPARATOR OF THE MODERN NEW HIGHSPEED DRAWING FRAME1
HUANG Jin1 , MEI Shunqi1* , DONG Yajie1 , JIA Yin1 , LI Handa1 , Zheng qiang2 1 - School of Mechanical Electronic Engineering and Automation, Wuhan Textile
University, Wuhan 430073, China;
2 - Tianmen Textile Machinery Co. , Ltd. , Tianmen 431700, Hubei, China 935523975@qq.com, meishunqi@vip.sina.com
1 Introduction 1.1 Background
Drawing is one of the bottleneck process in the spinning process. It is the last process which has joining effect and can improve the yarn unevenness and weight unevenness. In order to increase the quality of sliver and the speed to produce slivers, many manufactures widely used automatic control technology up to draw frame to develop modern high-speed drawing frame.
With the improvement of qualities of the drafting components, auto-leveling and on-line monitoring technology, the drawing frame has been improved in operation speed and degree of automation. Currently the speed to produce slivers of drawing frame has changed from 30 m/min in 1950 to today's 1100 m/min, increasing nearly 40 times. As the speed of the sliver-output is greatly improved, the time that the sliver-can is filled fully with sliver is significantly reduced.
Due to the increase of the frequency to can-doffing, the success rate of slivers-breaking directly restricts the machine's productivity. Nowadays, there are many foreign countries to produce drawing frame machines, such as Germany, Japan, Italy, Britain, Switzerland, and Rieter and Trutzschler has recently developed some new type of modern drawing frame.
The sliver-breaking is an important step in the process of drawing frame. The slivers regularly circle around in the can, when can is full of slivers it requires a device to cut off sliver and exchange the empty cylinder in order to drive the automatic machine running again. Improvement of the success rate and speed of sliver-breaking will directly improve the efficiency of sliver-breaking. Widely viewing the course of development of drawing frame machines in recent years, it is clearly that high-quality, high reliability, high automation and high efficiency are the development trend for drawing frame machines, and the automatic sliver-breaking device will become the standard configuration of high-speed drawing frame.
1 This paper was supported by the Chinese Research Foundation: 51175385; 2012AAA07-02; 2014BHE010
1.2 Common automatic sliver-breaking technology
To reduce the number of times of can-doffing and joints of slivers in subsequent process, the can diameter of the drawing frame is gradually increasing. Some manufactures developed some methods to increase the capacity of can, such as changing pressure capacity, chassis boost control, and rectangular can to adapt the needs of rotor spinning, for instance, we have increased capacity by 20% to the same area. In order to meet the needs of the automatic can-doffing efficiency , drawing frames with automatic can-doffing are normally set a automatic sliver-breaking device to cut slivers when can reaches the full capacity, otherwise it is needed to use artificial way which may increase the labor intensity.
The breaking slivers is the important step for can-doffing device. The different spun fibers need different methods to cut off slivers. Automatic sliver-breaking device can be divided into two kinds of active type and passive type.
(1)The passive way. By using a friction roller or a friction plate the sliver has friction with rollers or plates when can reaches the full capacity. This way is generally more common in domestic equipment, FA317A from Tianmen Textile Machinery Manufacture, some types of machines from Shenyang Hongda and Shanxi Baocheng are all using this way to cut off slivers.
(2)The positive type. The break of sliver is a necessary condition for automatic can-doffing, The positive type of break of sliver can drive a "Scissors" by an air can or motor to cut off slivers , such as TMFD80 from Tianmen Textile Machinery Manufacture. There were also clubbed type and push-type to complete the process of cutting. It can also be used gripping, stretching way to generate thin strips, such as Rieter RSB-D35.
The scissors-type: Through a complex gear train groups and linked the slider device, scissors cut the sliver automatically when can is doffing. Since the scissor-type mechanism of sliver-breaking has some disadvantage, such as complicated structure, high frequency of malfunction, inconvenient maintenance , greater noise by the automatic sliver-breaking device when it has a collision to panel, in the same time the collision will also cause damage to the device, the location of the sliver-breaking device may have some threats to personal safety , so nowadays many manufactures are generally not used in this way.
The clubbed-type: Some models use electromagnets combined serrated blades to cut off the sliver. Different spun fibers will use different methods to complete. In this way the rate is still slightly higher against blended material, while the rate is lower for acrylic spun and long fiber is harder to cut off.
The push-type: This type is suitable for long fiber. When can is pushed by the creels, the reciprocating transmission lever pushes sliver-breaking holder forward to make T-shaped plate press the sliver, and then T-shaped plate is follow the creel moving forward and cut off the sliver.
Of course, there are some another specific sliver-breaking devices to cut off sliver that can improve the production efficiency and automation of drawing frame, but sometimes it leads to increase the operating costs.
In some traditional cotton spinning mills the artificial means is still used to cut off sliver, which is inefficient and more time-consuming. Now part of the cotton spinning mills apply advanced high-speed machine to cut off sliver and it provides a high success rate. But taking into account the loss of various types of machine, personnel safety, noise pollution and other factors, there are some problems needed to be solved. Some cotton spinning mills are still using the old-fashioned machine in consideration of operating costs and covering area, and the rate is relatively low. In conclusion, to design a sliver-breaking device with a high rate of broken slivers, low cost, small covering area, high security and high-speed is urgently needed.
2 The theory of digital automatic sliver-breaking of drafting with fine-place
To design a sliver-breaking device of high speed drawing frame with a high rate of broken slivers , low cost, small covering area, high security and high-speed, we apply the digital control to sliver-breaking device by producing a fine-place of sliver. When can reaches the full capacity, PLC controls the motor to change the rotating speed of roller result in draft ratio increased. Then it will produce a part of fine-place of sliver. In the process of can-doffing, drawing frame will cut off sliver at the place of the fine-place of sliver.
To achieve roller drafting it is needed to meet the following basic requirements:
(1) The speed difference: surface speed of the output roller is greater than the surface speed of input roller ;
(2)Gripping force: put some pressure on leather roller (top roller) make the roller nip generate sufficient gripping force to fiber;
(3) Distance apart: gripping distance from front roller nip to back roller nip must greater than the distance of the fiber length or average length.
A drafting system often consists of several pair of rollers to form several draft zone. Drafting ratio between the two adjacent pairs of rollers called partial drafting ratio, the last pair of rollers and the preceding pair of rollers called the total drafting ratio. As shown in Figure 1, three pairs of rollers consisting of two draft zone,
V1>V2>V3
partial drafting ratio: E1=V1/V2
E2=V2/V3
total drafting ratio: E=E1*E2 =V1/V3
V1, V2, V3 are the surface speed of front roller, the middle roller, the back roller, respectively;
E1, E2 are drafting ratio of adjacent pairs of rollers between front roller and the middle rollers and drafting ratio of adjacent pairs of rollers between the middle rollers and back roller respectively;
E is the drafting ratio between the last pair of rollers and the preceding pair of rollers called the total drafting ratio.
Can coiler
Output cylinder
Leather roller(top roller)
_Q__Q—Q—Cl
OM V3B o
1 M B I
d C "u d ^ t
Input cotton •4-
©Main motor Servo motor
C
Constant speed\^^y Adjust the main drafting ratio
Fig. 1 The installation diagram of mechanical stretch of the drawing frame
In operation, the main motor drives front roller to rotate by belts and main axis, while the servo motor drives the middle roller and the back roller rotates respectively by the wheel train and belts, the sliver coiler screwed slider into can regularly to completed the coiling work. When can is full of slivers, drawing frame will stop temporarily. Then PLC will give a signal to restart drawing frame to control servo motor changing the rotating speed of the middle roller and the back roller. In the same time, the main motor maintains the rotating speed of front roller unchanged. As to the rotating speed of the middle roller and the back roller has released and the rotating speed of front roller unchanged, the total drafting ratio increase.
The sliver-breaking device produces a part of fine-place of sliver and it will be delivered to the place between coiler and can. In the process of can-doffing, drawing frame will cut off sliver at the place of the fine-place of sliver. During the process of exchanging the can, there are pulling force, pressure which sliver coiler exert and some friction on the sliver to make the fine-place of sliver to break.
3 Design of control system of the automatic sliver-breaking by drafting with fine-place
3.1 Hardware of control system of the automatic sliver-breaking by drafting with fine-place device
The structure and control system of automatic sliver-breaking device of the drawing frame includes the front roller, the middle roller, the back roller, the leather roller, PLC controller, digital touch screen, servo motor, main motor, etc. The front roller is connected to the main motor via the main axis and a belt. The middle roller and the back roller is connected to the servo motor via gear train set. PLC controller
is connected to the servo motor via a wire. The schematic diagram of hardware of control system is shown in Figure 2.
Operation direction
Fig.2 Schematic diagram of control system
We apply this new automatic sliver-breaking by drafting with fine-place to the drawing frame TMFD81L of Tianmen Textile Machinery Company Limited. On this machine, the main drive is three-phase frequency modulation motor FXP132S1-4g 4. 7KW, and Schneider ATV312HU55N4 standard frequency converter is used to change the characteristics of starting and stopping of the drawing frame. In normal driving, the drawing frame operates at set frequency. The external braking resistor of the frequency converter will stop the drawing frame quickly within the set time, so that the entire machine quickly stopped operating.
3.2 software section of the automatic sliver-breaking by drafting with fine-place
According to the requirements of the production process of the system, we can draw the software flow chart of the automatic sliver-breaking by drafting with fine-place, as shown in Figure 3.
The system can operate in the manual or automatic can-doffing working state according to the operator's choice. If the mode is selected for automatic can-doffing mode with the sliver-breaking of fine-place by drafting. After starting the drawing frame, operator can set the operating parameters, and then drive the drawing frame. When the count reaches setting length, the main driver of the machine is stopped for 2 seconds. And then The PLC gives a signal to restart drawing frame, and the fine-
place of sliver is produced. When the fine-place moves to the special place in setting time, the sliver is broken and the can fully filled with sliver can be doffed by new empty one.
Brea king
Resta rt
Produce
fine sliver
Operate
Stop breaking
Can-doffing
Fig.3 Work flow chart of "thin strip" strip-off In the process of can-doffing, drawing frame will cut off sliver at the place of the fine-place of sliver. When the entire can-doffing process has completed, the drawing frame will restart automatically if the empty can has already taken its place. The process of the drawing frame armed with automatic sliver-breaking by drafting with fine-place is shown in Figure 4.
Produce the
Catch bar Positioning Delay -► Restart
back system up
Fig.4 Work flow chart of drawing frame with "thin strip" strip-off In the control system of drawing frame TMFD81L armed with the technology of the automatic breaking of sliver , the Delta's DVP60ES00R2 programmable controller is used to control the operation of the machine, and the Delta's DOP-B07S411 programmable touch screen is used as human machine interface to complete the setup of the operating parameters, as shown in Figure 5. The communication type between the PLC and touch screen is RS232.
Fig. 5 Parameters setting interface of the break of fine-place of sliver
3.3 Characteristics of automatic sliver-breaking by drafting with fine-place
Above-mentioned system has some Characteristics.
(1) By using the system the main drive and drafting rollers can stop and restart when the can is reached it's fully capacity, and the drafting ratio can be changed, which can produce a fine-place of sliver that makes the cotton sliver prone to be cut off. These action processes carry out automatically by PLC control programming and the success rate of the break of sliver can reach 100%.
(2) The system is easy to operate, is high efficiency, stable and reliable operation, and it can be implemented on occupied area of existing drawing frame.
(3) To disuse the artificial breaking of sliver, replace mechanical breaking of sliver of drawing frame; simplify the structure of breaking sliver mechanism, reduce production costs and maintenance costs and improve the level of automation and production efficiency.
For these reasons, this paper provides the method and system to produce the fine-place of sliver to break sliver and to exchange the full can automatically controlled by PLC program, the system is installed with the drawing frame itself without any additional devices.
4 Experiment of the system
In our experiment the designed control system of automatic breaking of fine-place of sliver is installed on the drawing frame with type TMFD81L developed by Hubei Tianmen Textile Machinery Co. , Ltd.. The experiment materials are 4 kinds , such as: cotton, viscose, chemical fiber, and polyester cotton. The statistics and analysis of the experimental data are carried out. The experimental data are shown in Table 1.
Table 1 The efficiency of the breaking of fine-place of sliver
Objects of the break of sliver Success rate of the break of sliver(%) Set time of the break of sliver(s)
Cotton 100 0. 7
Viscose 98 1
Fiber 97 1
Blending 99 0. 9
The experiment of the breaking of sliver with fine-place by drafting were carried out 100 times with 4 kinds of materials, and the data was recorded and analyzed are shown in Table 2. It is indicated that with the changing of characteristics of the fiber, that is to say the changing of length and hardness of the fiber , the success rate of the break of sliver will be a corresponding difference.
From the table 2 we can see that the automatic breaking of the fine-place of sliver mode for cotton can achieve 100%. But the other three kinds of cotton material still can't achieve 100%. We have made the comparison of success rate and time of different ways of the breaking of sliver of cotton, as shown in Table 2.
Table 2 Comparison of efficiency of different ways of the breaking of sliver
Success rate of
The way of the break of sliver the break of sliver(%) Time(s)
the break of fine-place of sliver 100 Less than 1
Directional friction break of 95 Less than 1
sliver
Mechanical shear break of sliver 98 3
Artificial break of sliver 100 2~3
From this table, we can see that both the success rate of the breaking of fine-place of sliver and artificial breaking of sliver can achieve 100%. But the breaking of fine-place of sliver can be more efficient than artificial breaking of sliver in terms of time. Besides, artificial breaking of sliver depends on the proficiency of the workers. From a cost perspective, the breaking of fine-place of sliver is more affordable. Compared with directional friction breaking of sliver and mechanical shear breaking of sliver, the breaking of fine-place of sliver has higher success rate, thus the number of workers who break the sliver reduces, which improves factory automation production levels[5, 6]. In addition, the shorter operation time improves the efficiency of the breaking of sliver and avoid the costs consumption of equipment changing due to the mechanical loss and the time consumption of shutdown for replacement.
5 Conclusion
With the extensive applications of the new technology of the drawing frame, including the rapid development of computer control, PLC, IPC, servo control, frequency converter, USG Autolevel System, pneumatic pressure system, a high degree of automation, digitization, continuous and network can be achieved. The modern new high-speed drawing frame is an important part of the entire spinning system, the reliable online automatic breaking of sliver and can-doffing process is the indispensable key step in the working process of the drawing frame. The entire running of automatic sliver-breaking device is under control of PLC program. The automatic sliver-breaking of the modern new high-speed drawing frame is small footprint, and the HMI of it has showing clear and simple operation. The research of the technology of automatic sliver-breaking by drafting with fine-place has improved the automation level of the drawing frame.
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