Insufficient sealing is one of the common failures of continuous sealing machines. Insufficient sealing has three meanings: ① The sealing of the packaging bag cannot be sealed; ② Under the action of the sealing knife pressure, although the bag is sealed, it is slightly squeezed or After peeling, the seal will crack again; ③ When the peeling test is performed on the seal, half of the seal is strong and half is separated. The quality of the seal of such a bag is still unqualified because the contents are squeezed during storage and transportation. Easy to miss. This situation often occurs when the composite lining is OPP and blown PE.
First, the main causes of the * failures are as follows.
(1) Insufficient heat seal temperature
Under normal circumstances, when the total thickness of the bag made of OPP is 80 ～ 90μm, the heat-sealing temperature must reach 170 ～ 180 ℃; the total thickness of the bag made of PE as the lining is 85 ～ 100μm At this time, the temperature should be controlled at 180 ～ 200 ℃; as long as the total thickness of the bag is increased, the heat sealing temperature must be increased accordingly.
(2) Heat sealing speed is too fast
Sealing is not related to the speed of the sealing machine. If the speed is too fast, the seal can be heated in the future by the traction roller and sent to the cold press for cooling treatment, which naturally fails to meet the heat seal quality requirements.
(3) The pressure of the cold pressure rubber wheel is not suitable
There are one cold rubber wheel and one lower one, the pressure between them should be moderate, and only the spring is needed to adjust the pressure.
(4) There is a problem with the quality of the heat-sealing film
The sealing failure is also related to the quality of the heat-sealing film. If the corona treatment of the composite lining is not uniform, the effect is not good, and it happens to be at the sealing place, and it cannot be sealed. This situation is rare, but once it occurs, the product must be scrapped. Therefore, in the color printing and packaging industry, it is the next process to supervise the previous process. When a quality problem is found, the cause must be analyzed and resolved in time.
If there is moisture or dirt on the seal, it will also cause the seal to be weak.
In short, to solve the problem of inadequate sealing, generally the heat sealing temperature can be appropriately increased, the heat sealing speed can be reduced, and the pressure of the cold-pressed rubber wheel can be increased at the same time.
Second, the reasons leading to the second type of sealing failure are mainly the following:
(1) Insufficient heat seal temperature
Just increase the heat-seal temperature appropriately to solve the problem.
(2) The surface of the heat sealing knife is not flat enough
The heat-sealing knife is divided into upper and lower pieces, and usually thermocouples are installed therein to sense the temperature transmission. There are three screws on the heat sealing knife. The middle screw plays the role of supporting and reinforcing the blade. The other two screws are equipped with pressure springs and gaskets, which are mainly used to adjust the pressure of the heat sealing knife. The upper and lower blades each have two springs. . The main cause of the uneven surface of the heat-sealing knife is that the middle screw is inclined, not horizontal; or the pressure of the pressure spring of the upper heat-sealing knife is uneven.
The solution is to recalibrate the position of the middle screw so that it is horizontal. If the upper and lower heat-sealing knives are unbalanced, they must be adjusted by adjusting the pressure springs. When the spring is pulled back, the heat sealing knife will fall downward; when the spring of the lower blade is tightened upward, the heat sealing knife will move upward.
(3) Uneven pressure of cold pressure rubber wheel
The uneven pressure of the cold-pressed rubber wheel will also cause this kind of sealing failure. The solution is similar to the first case.
3. There are two main reasons leading to the third type of sealing failure:
(1) The pressure of the heat sealing knife or the pressure of the cold pressing knife is uneven, and the adjustments on the heat sealing knife and the cold pressing knife are completely the same;
(2) The surface of the heat sealing knife is not flat enough;
Refer to the corresponding solution for the second type of sealing failure.
(II) The fuse is blown
The main motor of the 900 type multi-functional plastic film continuous sealing machine is produced by Shanghai Shangwei Jinli Motor Co., Ltd. The main function of this motor is to drive the gearbox and the gear transmission of each component. Sometimes when the sealing machine is started, it will make a 'squeak' sound, which will not work properly, and even the fuse on the hot wire will blow out.
To troubleshoot the fault, first check whether the power supply is normal, then cut off the power supply, test whether the switch is damaged with a resistance file, and also carefully check the circuit and the motor for short circuits. Usually when the motor is short-circuited, the winding is damaged or the wire is disconnected, the fuse will blow as soon as the sealing machine is started. Another cause of this failure is that the fuse size is too small, and increasing the size accordingly can solve the problem.
(III) 'Squeak' sound during operation
This fault occurs during the operation of the sealing machine, and the 'squeak' sound often occurs suddenly. The next step is the uneven sealing speed, which causes the texture of the sealing seal of the packaging bag to be bad, which affects the appearance quality of the product. Occasionally it worked, but it was capricious.
This phenomenon occurs mostly due to severe mechanical damage or wear and poor lubrication.
Some time ago, the 900-type multi-functional plastic film continuous sealing machine used by our factory's Linyi packaging machinery Huzi has experienced this phenomenon when sealing. We first followed the sound to find the fault. Remove the back protection plate and find that the 'squeak' sound is transmitted from the gearbox. Remove the fixing screws one by one. It is found that the grease in the gearbox is dry and the gear is bright. This indicates that the cause of the failure is Out of oil. Mix the same type of oil and grease into the gearbox, and tighten the screws to recover. The 'squeak' sound disappears after the machine is turned on, and the seal is normal.
In addition, if the joints of the high-temperature belt are loose, seriously damaged, and are not clean and have dirt on the surface, they will not synchronize with the traction wheels during operation, and sometimes make a 'squeak' sound. The solution is to replace the high temperature belt of the same specification.
Changing the high temperature comes with certain skills. First compress the pressure wheel spring by hand, then place one end of the high-temperature belt on the rubber wheel, and the other end by hand against the other rubber wheel. Set the governor to low speed. Movement inertia, the high temperature zone is automatically installed. String 1
Sometimes a 'squeak' sound is also emitted by a DC parallel-motor. It may be caused by lack of oil in the motor bearings. If this is the case, it should be removed and lubricated, and the sound can be eliminated.
4. Sealing temperature is out of control
The fault manifested as the failure of the thermometer, the temperature could not be controlled, the heat-sealing temperature was not constant, the seal was either burnt or the seal was not tight, the seal was deformed, and it was difficult to see.
The main reason for this failure is that the thermometer is broken and must be repaired; in addition, the thermocouple may also be broken, and the induced temperature cannot be transmitted to the thermometer normally. Replace with thermocouples of the same model and specifications.
The mechanical reason is the uneven pressure of the heat seal, as long as the pressure spring of the heat seal knife is adjusted to make the pressure uniform. At the same time, the pressure contact surface of the heat sealing knife should be kept clean and free of dirt.
Another reason is that the heat seal quality of the composite material itself is not good, and the heat seal coefficient changes, resulting in inconsistent temperature.
5.Sealing machine stop and go
In production, we encountered the failure of the stopper to stop and stop and the speed was inconsistent. We removed the panel on the back of the sealer and found that the motor shaft connection and the gearbox connection have fallen off and loosened. Retighten the screws so that they all fit, and the problem is resolved. In addition, the main motor is operated by the contact of the carbon brush. If the carbon brush is severely worn, incomplete contact with the slip ring, or the friction is not good, it will also cause the sealer to stop and change, and replace it with new carbon of the same model. Swipe to solve the problem. String 2
6. Bubbles and irregular marks appear at the seal
This kind of failure is also more common, although it will not cause leakage of the packaging, but it will affect the aesthetics of the packaging and destroy the image of the product.
There are two main reasons for this failure.
(1) The equipment has been used for a long time. Dust and plastic debris are attached to the high-temperature belt, which causes the high-temperature belt to be uneven and uneven, resulting in uneven heating of the seal, and air bubbles appear after being pressed by the cold pressing wheel. Clean or replace the high temperature belt to eliminate the fault. The high-temperature zone is generally 1.5cm wide and about 22μm thick. If it cannot be washed off after attaching dirt, it has to be scrapped.
(2) There are irregular uneven marks on the cold-pressed rubber wheel, which are directly reflected on the packaging, so that there are more obvious marks on the seal. In order to ensure the beautiful appearance of the packaging bag, it is better to replace the cold-pressed rubber wheel.
7. Problems to pay attention to in equipment maintenance
(1) The sealing machine should be placed in a ventilated and dry place. Generally, the room temperature can be maintained at about 25 ° C.
(2) Every 48 hours of operation, 6 # oil should be added to each moving part, mainly in gears, bearings and gearboxes.
(3) Dust should be removed regularly to keep the whole machine clean. Unplug the power when not in use, and cover it with a cover cloth.
(4) If the running time is too long, the cooling fan should be turned on before shutting down, and then shut down after the temperature drops, because the shutdown is not allowed to cool down, the high temperature belt is easily damaged.
(5) The high temperature zone shall be regularly descaled to ensure the quality of the seal.
(6) The severely worn parts should be replaced in time to extend the life of the whole machine.