What are the common problems and maintenance methods of film wrapping machines?

Fault 1: PLC malfunction:

The main fault of PLC is the adhesion of output point relay contacts. If the motor is controlled at this point, the fault phenomenon is that after a signal is sent to start the motor, it runs, but after a stop signal is issued, the motor does not stop running. The motor only stops running when the PLC is powered off.

If this point controls the solenoid valve. The fault phenomenon is that the solenoid valve coil is continuously energized and the cylinder does not reset. If external force is used to impact the PLC to separate the adhesive points, it can assist in determining the fault.

[Maintenance Method]:

There are two repair methods for PLC output point faults. The more convenient one is to use a programmer to modify the program, change the damaged output point to a backup output point, and adjust the wiring at the same time. If the 1004 point of the control solenoid valve is damaged, it should be changed to the spare 1105 point.

Use the programmer to find the relevant statements for point 1004, keep (014) 01004 is keep (014) 01105.

The 1002 point of the control motor is damaged, and it should be changed to the backup point 1106. Modify the related statement ‘out01002′ to ‘out01106′ for the 1002 point, and adjust the wiring at the same time.

If there is no programmer, the more complicated second method can be used, which is to remove the PLC and replace the output relay of the backup point with the damaged output point. Install according to the original wire number again.

Fault 2: Proximity switch malfunction:

The shrink machine packaging machine has five proximity switches. Three are used for knife protection, and two are used to control the upper and lower film placement motors.
Among them, those used for controlling knife protection may occasionally interrupt the normal operation process due to one or two misoperations, and due to the low frequency and short time of faults, it brings certain difficulties to the analysis and elimination of faults.

The typical manifestation of the fault is occasional occurrence of the melting knife not falling into place and automatically lifting. The cause of the malfunction is that the melting knife did not encounter the packaged object during the descent process, and the signal of the melting knife lifting proximity switch was lost, just like the knife guard plate contacting the packaged object, the melting knife automatically returned upwards.

[Maintenance Method ]: A switch of the same model can be installed in parallel with the melting knife lifting proximity switch, and the dual switches can work in parallel to improve its reliability.

Fault 3: Magnetic switch malfunction:

Magnetic switches are used to detect the position of cylinders and control the stroke of cylinders.

The four cylinders of stacking, pushing, pressing, and melting are interrelated, and their positions are detected and controlled using magnetic switches.

The main manifestation of the fault is that the subsequent cylinder does not move, due to the fast speed of the cylinder, which causes the magnetic switch to not detect the signal. If the speed of the pushing cylinder is too fast, the pressing and melting cylinder will not move after resetting the pushing cylinder.

[Maintenance Method ]: The throttle valve on the cylinder and its two position five way solenoid valve can be adjusted to reduce the compressed air flow rate and decrease the cylinder operating speed until the magnetic switch can detect the signal.

Fault 4: Electromagnetic valve malfunction:

The main manifestation of solenoid valve failure is that the cylinder does not move or reset, because the solenoid valve of the cylinder cannot change direction or blow air.

If the solenoid valve blows air, due to the communication of the inlet and outlet air paths, the air pressure of the machine cannot reach the working pressure, and the knife beam cannot rise in place.

The proximity switch of the knife beam protection does not work, and the prerequisite for the operation of the entire machine is not established. The machine cannot operate, which is easily confused with electrical faults.

【 Maintenance Method 】: There is a leakage sound when the solenoid valve is leaking. By carefully listening to the sound source and manually searching for the leakage point, it is generally easy to identify the leaking solenoid valve.