Packaging machine pneumatic coil tension control mechanism design

Abstract : This paper introduces a new type of packaging machine mechanical tension control machine. The mechanism utilizes the flexible characteristics of pneumatic actuators to enable the packaging machine to achieve both high-speed unwinding and ensure that the tension of the packaging material is small and constant, thereby meeting the requirements of modern high-speed packaging institutions for unwinding the packaging material.

Foreword: In recent years, pneumatic technology has been widely used in the packaging machinery industry, which has made great progress in the packaging machinery industry. Due to the large number of advanced technologies such as pneumatics and computer control, the mechanical structure of modern packaging machinery has been greatly simplified, and the cost of equipment has been reduced. At the same time, the automatic ratio and reliability of the packaging speed and product appearance technicians have been improved. Has been greatly improved.
The pneumatic mechanism is light and does not pollute the environment. It can well meet the speed and environmental requirements of packaging machinery. Modern packaging machinery generally uses cylinders as the actuators, mainly utilizing the features of linear output and adjustable speed of the cylinders, thus filling the traditional deceleration and conversion mechanisms from rotary motion to linear motion, effectively simplifying the packaging machinery. The transmission mechanism reduces the cost and shortens the production cycle. In addition, using the cylinder as an actuator, the timing requirements for the coordination of the entire actuator can be solved by adjusting the control software. Compared with the traditional cam control mechanism, this can save a lot of installation and commissioning work. This is an important reason why pneumatic technology has gained popularity in the packaging machinery industry. Pneumatic actuators have good flexibility, or the speed and travel of the cylinder piston can be constrained by other mechanisms. By using this feature of pneumatic actuators, it is possible to design a pneumatically and mechanically combined compound mechanism to achieve accurate dynamic coordination and synchronization. It is also possible to design juice into flexible actuators. With this flexible mechanism, certain tasks can be accomplished. . Including the machine pneumatic tension control mechanism is an example of using the flexibility of the cylinder to work.
1. Brief introduction of pneumatic coil tension control mechanism of packaging machine The pneumatic coil tension control of packaging machine is divided into two periods:
1) Opening time: As shown in Fig. 1, the servo motor is not running, the vacuum sucker sucks the package material, and at the same time, the film roller brakes the cylinder to release the film roller brake disc, the film roller is in the free state, and the swing bar With the pull-film floating cylinder cooperating with the pull-down force, the swinging rod swings downwards, and the film roll is rotated through the wrapping material to open the film. When the swinging lever runs down to the position of the proximity switch, the sensor sends a signal, PLC controls the brake cylinder to brake the film feeding roller, and simultaneously controls the solenoid valve of the pull-film floating cylinder to swing downward, and the swinging rod acts on gravity. Sagging naturally.
2) Film pulling period: First, the vacuum sucker lifts the vacuum to unwind the package material, and simultaneously controls the pull-up film floating cylinder to operate the three-position three-way solenoid valve to generate electricity, so that the cylinder generates upwardly-running thrust. By adjusting the pressure reducing valve (Fig. 2), the upward thrust of the cylinder is smaller than the combined force of the swinging rod gravity acting on the cylinder rod (usually 1.5-2 Kg difference). At this time, the piston rod of the floating film floating film does not move, and the film pulls floating The role of the cylinder at this time is only to reduce the weight of the swing bar, and at the same time, the package material has a certain tension, and then the servo motor starts to pull the film. Servo motor pull film movement is intermittent, the length of each pull film is determined by the positioning color mark on the packaging material. The color code on the package material is equally spaced. When the color sensor detects the color code of the package material, a signal is sent to the PLC, and the PLC determines that the positioning film module controls the servo motor to quickly stop and realizes a rapid and fixed-length film pull. At the same time, the solenoid valve is controlled so that the vacuum sucker sucks the package material and reduces the package material preloading, and at the same time, the solenoid valve that controls the upward movement of the floating cylinder is turned off, so that the swinging rod is naturally sagging, otherwise, when the package material is rushed forward, the floating cylinder is upward. The thrust generated is smaller than the swinging rod's own weight, but because the lower chamber of the floating cylinder already has compressed air, the swinging rod cannot fully pull back and pull the pack rod by its own weight. Therefore, it is necessary to temporarily release the compressed air in the lower chamber of the floating cylinder, etc. After the swinging rod is fully retracted, the solenoid valve that controls the upward movement of the floating cylinder is opened to prepare for the next pulling of the membrane. This mechanism allows the package material to have a very small constant tension and at the same time has enough tension to open the film and increase the packaging speed. This type of mechanism utilizes the flexible operation of the pneumatic actuator, which allows the swinging rod to swing down and force the membrane to open, with a floating feature. The mechanism is applied to a 400g automatic nitrogen-filled milk powder packaging machine, and the use effect is very good.
2 Packing machine pneumatic coil tension control mechanism dynamics parameters calculation 2,1 unwinding tension calculation Package coil rolling moment of inertia consists of two parts, one is the rolling moment of inertia of the film expansion shaft itself, and the first one is the coil package's own moment of inertia . The rotational inertia of the expansion axis can be calculated as a cylinder with the formula J! == 1/2m·R12 (1)
In the formula; J1 - expansion axis of inertia, Aem2;
M1—the mass of the expansion shaft, Kg;
R1—The radius of the expansion axis, m.
The rolling moment of inertia of the film itself can be calculated according to the inertia of the cylinder. The formula is J2 == 1/2 m2 (R22+ r2 ) (2)
In the formula J2 - the rolling moment of inertia of the film, Kgm2;
M2--roll film quality, Kg;
R2 - outer diameter of the film, m;
r - the inner diameter of a roll, m.
It should be noted that the mass and the outer diameter of the film are gradually reduced during the work process, and the moment of inertia of the film roll is changed during the operation of the packing machine, and the tension radius of the package material is also changed. In order to determine the maximum tension of the unwinding, it should be calculated separately in the two extreme conditions. Take its maximum value as the basis for selecting system parameters. According to the action requirements of the packaging machine, the unwinding time t ≤ 0.4S; the unwinding length of the packaging material L ≥ 0.2m, and the tension F required for unwinding is calculated.

Packaging machine pneumatic coil tension control mechanism design

In order to simplify the calculation, the influence of the friction force is omitted, the unwinding process is considered as uniform acceleration circular motion, and the calculation formula for the length of each unwound coiled material is H == 1/4 л·R·at2 (3)
Where H - package length, m;
R - outer diameter of the film roll, m:
a - Acceleration, m/S2;
t - opening time, s.
The calculation formula for the acceleration of the circular motion is a==Mg/J==RF/J (4)
Where Mg == RF, where R - package outside diameter, m
F - tension of the package, N.
The formula (4) can be brought into (3) to obtain the tension formula of the package F == 2H·J/R2·t2 (5)
Where J = J1 + J2 - the total moment of inertia of the film roll, kgm2;
In order to determine the unwinding tension, the unwinding tension must be calculated separately for the maximum outer diameter of the packaging material and the minimum two for the outside diameter of the packaging material:
Decoiling tension at the maximum package diameter Fdmax==14.04N
Unwinding tension at minimum package diameter Fdmin==50.6N
According to the above calculation results, the maximum tension occurs when the package material is at a minimum. Therefore, the cylinder size can be determined according to the minimum tension of the package material.
2.2 Calculation of cylinder tension In Figure (3), the swing angle of the swing bar is ±10o, and the position of the swing bar varies with each direction of force relative to the direction of the swing center. The maximum cylinder tension required at the extreme position,
The cylinder bore diameter is calculated based on this pull force below.
Swing rod force balance equation is 4F·L1-F1F2 -F2L3==0 work (6)
Then the cylinder tension calculation formula is F2 == 4F·L1/L2-F1·L2/L2 (7)
Where F2 - the tension generated by the cylinder, N
F - the tension of the film. N;
F1—the mass of the swinging rod, Kg;
L2—the distance from the point of application of the force exerted by the tension of the package to the swinging rod to the swinging center of the swinging rod, m;
L1—the distance m from the center of mass of the swinging rod to the swinging center of the swinging rod;
L3 - The vertical distance between the point of application of the swing rod cylinder and the swing center of the swing rod, m.
Table 2 Geometric parameters and mechanical parameters of the swinging rod The working pressure of the packaging machine system is 0.65Mpa. In order to make the tension of the floating cylinder have a certain range of adjustment, the working pressure is preliminarily determined to be 0.5Mpa, and finally selected according to the working stroke and mechanical installation structure. SMC's CDM2B32-150 cylinder.
3 The installation, adjustment and use of pneumatic coil tension control mechanism for packaging machine The pneumatic coil tension control mechanism for packaging machine is specially designed for 400g automatic nitrogen filling milk powder packaging machine. It has been put into production formally and it is in good condition. During the debugging process, the pressure reducing valve (2) for controlling the working pressure of the pneumatic cylinder pulled downward by the floating cylinder is set to 0.45 MPa, and the floating cylinder pushes the pressure reducing valve upwards (1) The working pressure is set to 0.3 MPa. The actual measured decoiling time is 0.42s, the unwinding length is 0.23m, and the tension of the packaging material is 1.8kg during the film-pulling time. The tension control mechanism of the pneumatic coiling material of the packaging machine can meet the requirements of the packaging machine in the working process. The working requirements for open volumes illustrate the feasibility and accuracy of the above-mentioned structural solutions.
4 Conclusions 1) This article gives the design guidelines for the tension control mechanism of pneumatic coils for packaging machines. The production practice shows that the system has stable performance and reliable operation, and meets the requirements for modern high-speed packaging machinery to unroll its packaging materials.
2) Pneumatic control is flexible and clean. It is easy to form an electrical integrated system, which will further improve the overall level of the packaging machinery industry.