Trouble shooting for sealing machine
The seal is not strong
Insufficient sealing is one of the common failures of continuous sealing machines. Insufficient sealing has three meanings: ①The sealing part of the packaging bag cannot be sealed; ②Under the pressure of the sealing knife, although the mouth of the bag is sealed, it is squeezed or squeezed slightly. Tear and peel, the seal will crack again; ③When the seal is peeled off, half of the seal is firm, and the other half is separated. The quality of the seal of such a packaging bag is still unqualified, because the contents are very squeezed during storage and transportation. Easy to miss. This situation often occurs when the composite lining is OPP and blow-molded PE.
The main reasons for the first type of failure are as follows.
(1) The heat sealing temperature is not enough
Under normal circumstances, when the total thickness of the composite bag with OPP as the lining is 80～90μm, the heat sealing temperature should reach 170～180℃; the total thickness of the composite bag with 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) The heat sealing speed is too fast
The inability to seal is also related to the speed of the sealing machine. If the speed is too fast, the sealing part will be transported to the cold pressing part for cooling treatment before it can be heated in the future, and naturally it will not meet the heat sealing quality requirements.
(3) The pressure of the cold-pressed rubber wheel is inappropriate
There is one upper and lower cold-pressed rubber wheel, the pressure between them should be moderate, and only the spring needs to be clamped when adjusting the pressure.
(4) There is a problem with the quality of the heat-sealable film
The inability to seal the seal is also related to the quality of the heat-sealed film. If the corona treatment of the composite lining is uneven, the effect is not good, and it happens to be at the seal, it will definitely not be able to seal. This situation is rare, but once it occurs, the product must be scrapped. Therefore, in the color printing and packaging industry, the next process is to supervise the previous process. Once a quality problem is discovered, the cause must be analyzed and resolved in time. If there is moisture and dirt in the seal, it will also Cause for loose sealing effect
In short, to solve the first problem of weak sealing, generally increase the heat-sealing temperature appropriately, then reduce the heat-sealing speed, and increase the pressure of the cold-pressed rubber wheel at the same time.
The main reasons leading to the second type of failure of the seal are as follows.
(1) The heat sealing temperature is not enough
The problem can be solved by appropriately increasing the heat sealing temperature.
(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 in them to sense the temperature transfer. There are three screws on the heat-sealing knife. The screw in the middle plays the role of supporting and strengthening 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. There are two springs for the upper and lower blades. . The main reason for the uneven surface of the heat-sealing knife is that the middle screw is installed obliquely, not horizontal; or the pressure spring of the upper heat-sealing knife is uneven.
Maintenance information

The sealing machine is a kind of heat sealing equipment suitable for small businesses and families. Usually 220V AC power supply is used, and the heating power is hundreds of watts. The circuit of the sealing machine produced by various manufacturers is similar. Now take the FR-200 sealing machine as an example to analyze the working principle and maintenance examples of its circuit.
Circuit principle

The circuit is shown in the attached drawing. The machine has a nominal heating power of 350W and a maximum sealing length of 200mm. It has an operating handle, which has two functions: one is to press the plastic bag to be sealed on the heating strip after the operating handle is pressed down, and the other is to press the power switch K to close it. When the switch K is closed, the AC power is stepped down by R1 and R2, and the diode D1 is rectified. The capacitor C1 filters and provides working power to the machine. The power supply charges C2 through R4 and VR. At the initial stage of charging, the voltage on C2 is very small, the transistor Q is in the cut-off state, and its collector is at a high level. The triac SCR is triggered by the resistor R6 and the light-emitting tube LED, and the transformer T is energized. The second is to supply power to the heating element RL, and the plastic bag that is pressed on the RL is heated and sealed. When C2 is charged to cause the transistor Q to be turned on and the collector voltage drops and is not enough to trigger the thyristor, the RL stops heating, lifts the handle, takes out the plastic bag, and the sealing is completed. The handle is lifted, and after switch K is disconnected, C2 is quickly discharged through D2 and R3 to prepare for a charge. The luminous tube LED is used to indicate when the RL is energized. Adjusting the potentiometer VR can change the length of each additional sealing time. The specific adjustment range can be determined according to the power supply voltage at work and the thickness of the sealed plastic.
Repairing case:

The common failure causes of this machine are transformer burnout, thyristor damage, heating strip breakage, etc. Example 1: Depress the handle, switch K closed, RL is energized and heated continuously, and finally the sealing part of the plastic bag is heated and melted; the thyristor is welded during repair and measured with a multimeter, and it is found that the electrode between T1 and T2 has broken down. It can be repaired after replacing the thyristor. The thyristor chooses 3A/600V, such as TLC336A. Example 2: After pressing down the handle, BL cannot be heat-sealed. Open the casing and visually find that the transformer has been burnt out, and the primary coil of the measuring transformer has been broken. At this time, it can be repaired by replacing it with a transformer with a secondary voltage of about 25V and the same power as the original. The transformer of this machine works intermittently, so its power capacity is about 350W. If the temperature is too high, or the continuous use time is too long, it may cause damage to the transformer, which should be paid attention to during use.
Example 3: After pressing down the handle, the heating temperature cannot be adjusted when the electric heating is applied. When repairing, mainly check the potentiometer VR. Because VR is often rotated, the carbon diaphragm of VR is damaged. Replace it with the new VR.
technical parameter:
sealing head size: 850*710*160mm
Sealing length: 600mm*2
Sealing width: 8-10mm
Sealing line spacing: 720mm
Packaging capacity: 2-5 times/minute
Power supply: 380V/50HZ
Dimensions: 2230*1200*880mm

More information link part 1: what the sealing machine is

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