Do You Know The Maintenance Example Of Continuous Band Sealer?

Continuous band sealer is a heat sealing device suitable for small businesses and households. 220V AC power is usually used, and the heating power is hundreds of watts. The circuit of continuous band sealer produced by various manufacturers is similar. Now take FR-200 sealing machine as an example to analyze the working principle and maintenance example of its circuit.

First, the circuit principle

See the figure for the circuit. The machine has a nominal heating power of 350W and a maximum sealing length of 200mm. It has an operation handle, which has two functions: one is to press the operation handle and then press the plastic bag to be sealed on the heating bar; 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. Capacitor C1 is filtered to provide working power to the machine. This power source charges C2 via R4 and VR. In the initial charge, the voltage on C2 is very small, the transistor Q is in the off state, and its collector is at a high level. The triac SCR is triggered by the resistor R6 and the LED of the light emitting tube, and the transformer T is powered. The second is to supply power to the heating element RL, and the plastic bag pressed on the RL is heated and sealed. When C2 is charged, the transistor Q is turned on, and the collector voltage is reduced, which is not enough to trigger the thyristor. RL stops heating, raises the handle, removes the plastic bag, and the sealing is completed. After the handle is lifted and the switch K is turned off, C2 is quickly discharged through D2 and R3 to prepare for a single charge. Light-emitting tube LED is used for indication during RL power-on. Adjusting the potentiometer VR can change the length of each sealing time. The specific adjustment range can be determined according to the power supply voltage at work and the thickness of the sealed plastic.

Second, maintenance examples

Common causes of continuous band sealer are burned out transformers, damaged thyristors, and broken heating bars.

Example 1: Depress the handle, switch K is closed, RL is continuously heated, and the plastic bag sealing part is finally heated and fused. When repairing, the thyristor is welded and measured with a multimeter. It is found that the T1 and T2 electrodes have broken down. It can be repaired after replacing the thyristor. Triac is 3A / 600V, such as TLC336A.

Example 2: After pressing the handle, BL cannot heat the seal. Open the casing and visually observe that the transformer has burned out, and the primary coil of the measuring transformer has been broken. At this time, it can be repaired by replacing the transformer with the secondary voltage of about 25V and the same power as the original. The local transformer 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 Transformer is damaged, this should be noticed in use.

Example 3: After the handle is depressed, the heating temperature cannot be adjusted when the power is heated. During maintenance, mainly check the potentiometer VR. Because the VR is often rotated, the carbon membrane of the VR is damaged. Use the new VR instead.