Automatic shrink packaging machine control principle and maintenance
December 17, 2022
The fully automatic shrink packaging machine is a highly automated equipment widely used in the pharmaceutical, food and beverage and home chemicals industries. The application of shrinking machines can greatly reduce the material and labor costs of the middle box packaging, which has important economic significance.
1. Equipment principle and structure The automatic shrink packaging machine is a kind of automatic packaging equipment controlled by PLC and other peripheral lines combined with pneumatic components and mechanical devices. The actuator of the device is a cylinder. It is controlled by the two-position five-way solenoid valve to advance and retreat. The working position of the cylinder is detected by the magnetic switch and the proximity switch and fed back to the PLC. The PLC sends a control command to the solenoid valve of the corresponding cylinder through the program, thereby controlling the movement of the cylinder.
2, fault repair 2.1 PLC fault PLC fault mainly has output point relay contact sticking. If the motor is controlled at this point, the fault phenomenon is that after the motor is started, the motor runs, but after the stop signal is sent, the motor does not stop running. When the PLC is powered off, the motor stops running. If this point controls the solenoid valve. The fault phenomenon is that the solenoid valve coil is continuously powered and the cylinder is not reset. If you use an external force to strike the PLC to separate the glue points, you can help determine the fault.
There are two ways to repair the PLC output point fault. One of the more convenient ones is to modify the program with the programmer to modify the damaged output point to the alternate output point and adjust the line at the same time. If the 1004 point of the control solenoid valve is damaged, it is changed to the standby point of 1105 points. The programmer can find the relevant statement of 1004 points, and keep(014)01004 is keep(014)01105. Control the motor's 1002 point damage, change to the standby point 1106, modify the 1002 point related statement out01002 to out01106, and adjust the line at the same time.
If there is no programmer, you can use the second, more troublesome, remove the PLC, open the PLC and remove the output relay of the standby point to the damaged output point. Then install it according to the original line number.
2.2 Proximity Switch Failure The shrinking machine has five proximity switches. Three for knife protection and two for controlling the upper and lower film release motor. Among them, the tool protection is controlled, and occasionally one or two misoperations will interrupt the normal operation process, and the number of failures is small and the time is short, which brings certain difficulties to the analysis and elimination of the fault. The fault is typically manifested by the occasional occurrence of a melter drop that is not in place and automatically raised. The reason for the failure is that the melt knives did not encounter the packaged material during the descent process, and the melt knives approached the switch to lose the signal, and the squeegee automatically returned upwards in the same manner as the razor plate contacted the packaged object.
The fault repair method can install a switch of the same type in parallel with the proximity of the melt knife to the switch, and the two switches work in parallel to improve the reliability.
2.3 Magnetic Switch Fault The magnetic switch is used to detect the position of the cylinder and control the stroke of the cylinder. The four cylinder actions of lamination, push pack, press pack and melt knife are interrelated and magnetic switches are used to detect and control their position. The main fault is that the subsequent cylinder does not move, because the cylinder speed is faster, and the magnetic switch cannot detect the signal. For example, if the speed of the push cylinder is too fast, the press pack and the melt knife cylinder will not operate after the push pack is reset.
The fault repair method can adjust the throttle valve on the cylinder and its two-position five-way solenoid valve, reduce the compressed air flow, and reduce the cylinder running speed until the magnetic switch can detect the signal.
2.4 Solenoid valve failure Solenoid valve failure mainly manifests as the cylinder does not move or does not reset, because the cylinder solenoid valve can not be reversed or helium. If the solenoid valve is suffocating, the air pressure of the machine will not reach the working pressure due to the communication between the inlet and outlet air lines, and the knives will not rise. The tool beam protection proximity switch does not work, the preconditions for full machine operation are not established, the machine cannot be operated, which is easily confused with electrical faults. There is a leaking sound in the solenoid valve helium. Listen carefully to the sound source and search for the leak point by hand. It is generally easy to find the solenoid valve of the helium gas.
