Key Technology Research and Equipment Development of Automatic Spool Feeding Device

To solve the problems of high labour intensity and low efficiency of artificial spool feeding, an automatic spool feeding device is developed. SolidWorks is used for overall structural scheme design and determination of design parameters. The kinematic equation of the chain conveyor line is established, a mathematical model is solved with MATLAB, and sprocket, and chain parameters are selected. The clamping mechanism and turnover mechanism are designed, theoretical analysis of the key structure is completed. Dynamic simulation of the chain conveyor line is carried out by ADAMS, and preliminary operational stability is determined by combining motion curves. The test prototype is developed for feeding tests and measurement of the operating parameters. The test results show that the efficiency of machine feeding is 13% higher than that of manual feeding, the average feeding time is 43% lower, the halt waiting time is 43% lower, and the operating parameters are by the theoretical design and the work is reliable. The research results can provide a reference for similar spool-feeding devices.


Introduction
With the proposal of the concept of "Made in China 2025", a large number of manufacturing enterprises begin to carry out automation transformation.The textile industry, as a traditional pillar industry of China's national economy, is also a labour-intensive industry [1].As one of the indispensable steps in the textile process, spool feeding is still inseparable from manual labour.In order to improve production efficiency and reduce labour intensity, some textile enterprises begin to apply automation technology to spool feeding.Lu Jianhua [2] designs a spool branching feeding device.The cam drives the slider with two filling grooves to move from left to right.When the slider slides to the left and right, the spools in the filling groove can fall automatically into the feeding groove for feeding.Fei Xiaojie [3] fixes the spool horizontally through the feeding channel and the spool automatically falls into the clamping slot, which is then pushed by the cylinder to feed the spool into the designated feeding position.Shen Jianrong [4] invented a rotary automatic feeding device for spools, the spools are manually stacked in the material path horizontally first, then the mechanical arm is pushed to the feeding position by the cylinder, clamps the spool and moves to the feeding position.Cao Jingen [5] et al. fix the spool laterally in the middle of the conveyor belt where cross plate and inclined plate are installed, then the motor is controlled to drive the conveyor belt movement, then the spool is sent to the feeding channel.It can be seen that most of the spool feeding devices are semi-automatic, auxiliary equipment is developed according to the requirements, manual work cannot be completely replaced, and each feeding device can only be fixed for one machine, so the overall efficiency improvement is not obvious.
Therefore, it is necessary to develop an efficient and stable automatic feeding device for spool, which can be applied to different types of spools, release labour force and reduce labour intensity, fundamentally solve the difficult problem of huge workload in textile industry at present, and promote the modernization process of national industry [6][7].

Overall Workflow
The feeding object is a base-supported spool tube, whose shape and dimension parameters are shown in Fig 1 .The upper half is conical with a height of about 20 mm, the upper cone has a diameter of 74 mm, and the lower cone has a diameter of 30 mm, with a cylindrical length of 72 mm.Given the requirements of spool characteristics and production takt, according to different functions, the device is divided into four modules by modular design method [8]: transport module, fetching module, sending module and control module.The overall structure of the device is shown in Figure 2.
The transport module is mainly composed of the stepper motor, material box, hopper and chain conveyor line.When starting feeding, the chain conveyor line drives the spool upward and falls onto the conveyor at the outlet.The conveyor conveys the spool to the fetching module.
The fetching module can be divided into vertical and horizontal parts.The vertical fetching part mainly includes the clamping jaw cylinder, rotary cylinder, guide rail cylinder and conical clamping jaw.When fetching, the guide rail cylinder moves downward to drive the conical clamping jaw into the inner part of the spool, the clamping jaw cylinder works to open the conical clamping jaw upwards, and the spool is taken by friction force.Then, the guide rail cylinder rises to the specified position and stops working, and the rotary cylinder drives the clamping jaw to rotate 90°and sends the spool to the horizontal clamping point.
The horizontal part also includes a jaw cylinder and a rotary cylinder.The jaw clamps the cylindrical part of the spool tube from the outside.Linear module and rotary cylinder drive the whole movement to the sending position through the connection of the retainer plate.The rotary cylinder drives the whole mechanical arm to rotate 180°.After the spool is put into the feeding trough, the pneumatic clamping jaw relaxes, and the linear module and rotary cylinder return to their original position to be ready for the next feeding work.
The sending module consists of a feeding trough and turnover mechanism.When the winder is idle, the turnover mechanism takes a spool out of the feeding trough, clips it to the work position, and completes the feeding action.
The control module is composed of sensors, a PLC controller, and an HMI interface to complete the logical control of the whole device.The overall workflow of the device is shown in Figure 3.

Determination of Design Parameters
The general layout of the production site is shown in Figure 4.There are 5 workstations with a distance of 40 cm.The total length of the conveyor line is the same as that of the cross-feeding, which is 200 cm.Determine the production takt.Textile enterprises adopt the working system of "three shifts".The daily theoretical working time is 24 h, and the known winding time is 30 s for a single spool.According to the daily planned output of 2400 pieces per machine in the production centre, the production takt  is: Where his theoretical working time per day; Q is daily production quantity.During transport operation, sprockets drive the fixed hoppers on the chain line.Each hopper can hold 1-2 spools.In order to match the feeding quantity with the production efficiency of the device, it is necessary to select the appropriate feeding velocity.According to the design formula of the hopper: Where  is the distance between two hoppers, which is 400 mm;  is chain velocity;  0 is effective volume of hopper, its value is in 1 to 2;  is success rate of spool conveying, its value is 0.6;  is production efficiency of winder, its value is 10 per minute; If the fetching device needs to complete feeding for 5 times within one production takt, then its average feeding time  1 is: The pneumatic clamping jaw has small action and can be executed at the working end of the rotating cylinder.Its action time coincides with that of the rotating cylinder.Therefore, based on the working time of the rotating cylinder, the one round trip time of the rotating cylinder  2 is set for 3 s, combined with formula (1-2), linear module velocity  1 should satisfy the following formula: 4 Where   is average reciprocating distance of horizontal-fetching device, which is 2 m.To reduce the waiting time for horizontal fetching, the vertical fetching time should be less than the minimum working time for horizontal fetching, that is: Where   is shortest distance between feeding trough and fetching module.Its value is 20 cm.To reduce the waiting time for vertical fetching, the conveying time of conveyor line  4 should be less than the shortest time for vertical fetching  3 , then its conveying velocity  2 should satisfy the following formula: Where   the distance of conveyor line, which is 200 cm.Feeding process of the device is carried out simultaneously with production process, and spool can be transported to the feeding trough to wait in advance during the production process.Therefore, the turnover mechanism acts as the final executing mechanism of feeding action, and its action time also represents the feeding time.According to the average feeding takt 36 s, the winding time of single spool is 30 s, so the action time of turnover mechanism which is within 6 s can meet the production requirements

Dynamic Analysis of Chain Conveyor Line.
In a chain drive system, the forces acting on the chain are not equal before and after the engagement of sprockets, which results in a certain degree of vibration.The chain drive model is shown in Figure 5(a),  is the angular velocity of the driving sprocket,   and   are the speeds of the chain in direction of x-axis and y-axis respectively.According to functional principle, the distributed chain mass is condensed into a concentrated mass by discrete method [9].The equivalent chain drive model as shown in Figure 5 (b) can be established and then the dynamic response of the chain drive system can be studied.
Where:  is sprocket rotation angle;  1 is equivalent mass of tight edge;  2 is equivalent mass of loose edge;  is the number of close-edged hoppers;  is the number of loose edge hoppers;  0 is the mass of a single hopper.
The total kinetic energy of the chain drive system   includes the kinetic energy of equivalent mass in x-axis direction  1 , the kinetic energy of equivalent mass in y-axis direction  2 and the kinetic energy of driving sprocket  3 , which can be expressed as: where: 0  ̇2 , so: By deriving the kinetic energy of the system from its generalized coordinates, it can be concluded that: (2) System Potential Energy In the chain drive process, the matching between chain links can be equivalent to the model shown in Figure 6.Displacement of each chain link is generated by tension   、 −1 .According to the principle of potential energy function, the potential energy of system can be expressed as: Where  is equivalent stiffness of chain;  is chain pitch;  0 is sprocket rotational inertia;  is the number of links.By deriving the system potential energy from generalized coordinates, the dynamic differential equation can be derived as: (3) System Dissipation Function According to Figure 8, the stretch damping dissipated energy of chain drive system   is: By deriving the system dissipated energy from its generalized coordinates, it can be concluded that: Where C is chain link tensile damping.
(4) General force The general force acting on system mainly consists of the load in X and Y directions and the driving force of driving sprocket, which can be expressed as: Where   、  、  are the corresponding generalized forces for 、、 respectively;  0 is the driving torque of driving sprocket;  1 refers to chain drive efficiency;  is sprocket radius.
(5) Kinematic Equation Formulas ( 17), ( 18), ( 19) are substituted into the system motion equation established by Lagrange equation [10]: Where  is kinetic energy of system;  is potential energy of system. is dissipated energy of system.  is corresponding generalized force in each direction of generalized coordinate;   is generalized coordinate of system; ̇ is generalized velocity of system.The dynamic equation of the model in x-axis direction is obtained as follows: The dynamic equation in y-axis direction is: The dynamic equation of driving sprocket is: Conveyor System Response.The chain drive system can be represented by three second-order ordinary differential equations through the previous calculation.According to Runge-Kutta method [11,12], three variables are introduced and then equation ( 17)-( 19) are reduced to first-order differential equation group by MATLAB problem solving system (20).
After transforming this three-component second-order differential equation group into sixcomponent first-order differential equation group, the movement variation of the system can be solved by using the function ode45 of MATLAB [13].
According to the feeding process, spool is conveyed vertically along the chain conveyor line, so the movement curve of chain on the y-axis can be studied emphatically.When the initial conditions remain unchanged, the displacement curves of chain in the y-axis direction are obtained by substituting the chain pitch of 9.525 mm and 31.75 mm.As shown in Figure 7 and 8, the chain generally runs smoothly without obvious displacement fluctuation.According to velocity formula v=x/t, the chain velocity with pitch of 9.525 mm is about 0.1 m/s and is about 0.27 m/s with pitch of 31.75 mm.Therefore, the chain with 9.525 mm pitch can be selected and its ISO chain number is 06B, which meets the design requirements.
With a constant pitch, sprockets with 10 and 20 teeth respectively are taken and the velocities are calculated.As shown in Figure 9 and 10, it can be found that the smaller the number of teeth, the greater the velocity fluctuation generated by the chain, and the more unstable during the running, and the easier to fall for the spool tube and to stuff during conveying.Considering the wear uniformity of the sprocket, an odd number of sprocket teeth is usually selected.In this design, the number of sprocket teeth is 19. Figure 10.Chain velocity with 20 teeth

Clamping Mechanism
Clamping mechanism needs to fetch spools into the feeding trough of sending module after spools reach the end point of transport module.As the intermediate link of feeding work, the reclaiming process must be stable, so that the material will not loose and fall off during the process of overturning and conveying.
Considering the light plastic material of spool with a single mass of only 30 g and its low stiffness, as the key component of clamping mechanism, cylinder with a small output force should be selected to prevent excessive clamping force from plastic deformation and affecting the coordination between subsequent feeding actions.
The vertical fetching device is shown in Figure 11(a), and the component is shown in Figure 11(b).According to the cylindrical structure of the lower part of spool, the main part of the cylinder claw finger is also designed as a cylindrical shape.The two-cylinder claw fingers are opened in the inner part of the spool and take it out by friction.The diameter of the two claw fingers when shrinking is 4 mm smaller than that of the inner diameter of spool, and the head is designed as a conical shape for easy access to the inner part of spool.
The clamping jaw cylinder working principle is shown in Figure 11 (c).Cylinder has two air pipe connection ports A and B. according to the action requirement, when one is used as the intake port, the other is used as outtake port.When compressed air enters from A, it pushes the piston and piston rod to the left, which pushes the upper and lower wedge blocks and clamping claws to move outward along the radial direction.Conversely, when compressed air enters from B, the piston and piston rod move to the right, then clamping jaw restores to initial state under the action of spring tension.
As shown in Figure 11(d), the contact surface between push rod and wedge is 45° inclined.According to the analysis of clamping conditions, it can be concluded that: If the compressed air pressure  is 0.1 MPa, the cylinder piston stress area should satisfy the following formula: Where  is output force of a single pneumatic clamping jaw. is friction force between clamping jaw and spool wall, its value is 0.1;   is cylinder output force;  1 is the vertical component of wedge block;  is the spring stiffness coefficient with a value of 0.7 N/mm; ∆ is spring displacement;  is intake pressure;  is force area of piston.
The guide rail cylinder drives rotary cylinder and clamping jaw cylinder in vertical reclaiming device to move up and down by mounting plate.It is known that the rotary cylinder each working time is 1.5 s, and the guide rail cylinder stroke  is 200 mm, so the guide rail cylinder velocity  2 should satisfy the following formula: The rotary cylinder mainly drives the rotation of support rod and pneumatic clamping jaws.Here, the clamping jaw with large mass is taken as the design basis, the mass of rotating arm of the horizontal fetching part is 2.3 kg measured by SolidWorks, the distance between centre of gravity and rotating axis L is 100 m.The horizontal fetching device is shown in Figure 12(a).Its components are shown in Figure 12(b) and the motion sketch of cylinder is shown in Figure 12(c).The compressed air from port A pushes corresponding rack to right, which drives the gear to rotate counterclockwise.The compressed air from port B causes gear to rotate clockwise conversely.Rotation of the gear causes the arm attached to it to rotate; thus, the spool is put into feeding trough.According to the force formula of cantilever:  =  ′  = 2.3 •  (24) It is known that the teeth number of drive gear Z is 17, modulus   is 1.5.Since the rotary cylinder is driven internally by gear rack, the linear motion distance of the rack is equal to the rotation distance of the gear pitch circle.According to the design requirements, the rotating angle of rotary cylinder should reach 180, so the rack stroke  is: = 26/ (26) Similarly, the forced area of piston in rotating cylinder  1 is:  1 ≥ 920 2 .

Turning Mechanism
As shown in Figure 13(a), the turnover mechanism is mainly used to take the spool out of feeding trough and transport it to working position.The structure sketch is shown in Figure 13(b), which mainly includes three rotating pairs and one moving pair.The working process is shown in Figure 14.The push rod cylinder drives tilting plate to rotate clockwise around fixed shaft through the handle and the clamping jaw opens when meets the bar.As shown in Figure 14(a), the cylinder retracts after spool falls into the middle of the tilting plate and then clamping jaw closes, as shown in Figure 14 The mass of tilting mechanism assembly can be measured by SolidWorks evaluation module:  3 = 4.7, the distance between centre of mass and axis is 110 mm, distance between connection centre and axis is 20 mm, as shown in Figure 15.Therefore, the push rod cylinder output force  ′′ should satisfy the following formula: Overturning process is the last step of the whole feeding process, its action time represents the feeding time.It can be obtained that the theoretical feeding time is 6 s by formula (1-1), i.e. the cylinder meets the output force requirement and the single movement process should be within 3 s.Push rod cylinder type is selected according to SMC.Cylinder motion is about 2 s once, feeding time is about 4 s, which meets design requirements.Through the above theoretical analysis, the SMC software is used to complete the selection of cylinder type.Specific parameters are shown in Table 1.

Model Establishment
Chain drive system is a closed planar drive mechanism with intermediate flexible elements.Adams modelling function is not suitable for complex model establishment, so other three-dimensional software is needed to build the model [14].SolidWorks is used to establish the chain drive model as shown in Figure 16.This is a roller chain system consists of one driving sprocket and three driven sprockets.It relies on the engagement of the chain to realize the transmission of motion and torque.In order to reduce the running time of simulation, the chain conveyor can be simplified as a single-side chain drive system, and the hopper can be regarded as an equivalent load applied in the simulation model.The simulation mainly studies the velocity, acceleration and vibration of chain conveyor under the load, so as to avoid lagging or excessive velocity fluctuation during the transportation process.Adams contact force calculation models are divided into poison model and impact function model [15].The impact function model is more suitable for solving this continuous contact problem, which corresponds to impact method in contact setting module of ADAMS software.As shown in Figure 17, the impact function model can be equivalent to the elastic force from mutual contact between components and the damping force generated by relative velocity, and the equivalent calculation of contact force is made by using Impact function in Adams [16].
In this simulation, 45 steel is used for chain links and sprockets, and the setting parameters are shown in Table 2.

Analysis of Simulation Results
The simulation time is 5 s and the step is 500.After simulation, the movement curves of each component are obtained by Postprocessor.The blue line in Figure 18 is angular velocity curve of driving sprocket, with little variation and a tendency close to a straight line, which is less affected by the change of impact force.However, according to the angular acceleration and acceleration curves of the driven sprocket in Figure 18 and Figure 19, the driving sprocket rotates with the driven sprocket within 1 s in the initial stage, the angular acceleration and velocity fluctuations of driven sprocket are large.The velocity difference between driven sprocket and driving sprocket is about 25 mm/s, so the transmission efficiency is low.The velocity difference decreases gradually in about 1.5 s, but the meshing in and out of chain links will change the impact force to some extent, resulting in some obvious step points in acceleration curve, but the overall velocity is relatively stable and the difference between driven sprocket and driving sprocket is about 10 mm/s.

Prototype Test
According to the design drawings, a test prototype is developed as shown in Figure 22.After complete installation and commissioning, a one-week field test is carried out.A set of statistical data such as production takt and output is selected randomly every day to verify the design rationality compared with manual feeding.Specific test data are shown in Table 3.On the first day of test, the amount of feeding is small.According to formula (1-1), the average feeding time is 10.2 s, which is quite different from theoretical value.Through investigation, it is found that at the end of the transport process, some spools neither follow the chain to the fetching module nor fall back to the material box automatically.Jamat the outlet causes the subsequent spools to fail to be fed normally.Considering the light material of spool itself, an air blower is installed at the outlet.After next two days of observation, a sensor is installed at the place where jam is most likely to happen and the automatic air blower returns the spool to material box when the sensor detects jam.
After solving the problem of spool jam, the four-day test is continued.During the test, device operates smoothly, the running velocity of chain conveyor line is about 0.1 m/s, the running velocity of conveyor line is 0.55 m/s, the velocity of straight module is 0.5 m/s, the average feeding time of cross fetching device is 7.0 s, the running velocity of guide cylinder is 0.09 m/s, and the average fetching time of vertical fetching device is about 3.8 s, which basically corresponds to the theoretical design results.The modules of the device cooperate well.Sufficient spool can be steadily transported to filling trough without the occurrence of "machine waiting material".
According to the data statistics, the device completes 2413 spools feeding on average in 7 days, average feeding time is 5.8 s, average waiting time for halt is 2.1 h.Statistical analysis of the data sheet shows that the average feeding time per machine is 271 more than manual feeding per day, average feeding time is 4.5 s shorter than manual feeding time, average downtime per day is 2.3 h less, compared with manual data, automatic feeding device output is 13% higher than manual feeding.The feeding time is 43% shorter than manual time and the down time is 43% shorter than manual time.The test proves that the overall design of device is reasonable, the operation is reliable and meets the production requirements.

Conclusion
Aiming at the problems existing in spool feeding, an automatic spool feeding device is developed.The structure design and simulation analysis of key parts are carried out with modular design ideas.SolidWorks is used for overall structural scheme design and determination of design parameters.Dynamic simulation of the chain conveyor line is carried out by ADAMS and MATLAB.The field test is carried out by developing a test prototype and the following conclusions are drawn: 1) During the operation of the device, each module cooperates smoothly and there is no collision between the parts, which verifies the rationality of the device structure design.Operation parameters of feeding module and simulation data are almost the same, which verifies the correctness of kinematic analysis and simulation; 2) the problem of stuffing during conveying, can be solved by adding detection and blowing the device in a key position, which improves the success rate of feeding and reduces the downtime of the device; 3) Through the prototype experiment, compared with manual feeding, the automatic spool feeding device can increase the daily output by 13%, decrease the average feeding time by 43%, decrease the halt waiting time by 43%, improve efficiency and reduce labour intensity at same time, which provides a new idea for the research of similar automatic spool feeding device.
4) The operating efficiency of the device can still be further improved.The running velocity of conveyor line and the running velocity of guide cylinder can be designed using big-data algorithms to further improve the efficiency.

Figure 5 .
Chain conveyor line.(1) System Kinetic Energy According to Figure 5(b), the velocity and equivalent mass  1 、 2 of chain in  and  directions can be obtained:
25)Rack velocity  3 should satisfy the following formula:

Figure 15 .
Figure 15.Force analysis of turnover mechanism.

Figure 18 .
Figure 18.Angular velocity of driving and driven sprocket.

Table 2 .
Contact parameter settings.

Table 3 .
Test record table.