Created on:2021-06-30 14:18

Shaking fault of punching cylinder of automatic press for glass shell

Shaking fault of punching cylinder of automatic press for glass shell

In the production process, the stamping cylinder of the automatic press for producing the glass shell trembles in the action process, and the shaking action is strong and weak, but it can basically complete all the actions. The control system adopts the SCVP series electro-hydraulic servo valve of oilgas company. Its structure is permanent magnet force feedback two-stage servo valve, and the working pressure is 9Mpa.

(1) Cause analysis

According to the phenomenon that the failure is the bad action of the hydraulic cylinder, it is judged that the servo valve spool has shaking action in the process of action. The reasons can be divided into electrical and hydraulic parts. Due to the fast processing of electrical fault, in order to repair as soon as possible, we should start with electrical treatment.

① If the electrical part assumes that there is a fault in the electrical part, it may be caused by the control signal cascading into the AC signal, loose terminals, poor connection, signal circuit hardware fault, servo amplifier circuit hardware fault and so on. After inspection, it can be ruled out that the control signal can be connected in series with the AC signal. The wiring terminal is firm without looseness, and the wiring is not in bad contact. The signal generation circuit hardware module and the servo amplifier circuit hardware module are replaced. The fault phenomenon is still the same, and the signal is normal when the oscilloscope is used for measurement. So far, the electrical part of the basic troubleshooting.

② The hydraulic part eliminates the possibility of the following faults in turn: air in the hydraulic pipe and hydraulic cylinder, hydraulic oil pollution, serious leakage in the hydraulic cylinder, unstable pressure of control oil circuit and main oil circuit. Finally, the servo valve body fault was identified. The pilot part of the servo valve was replaced and the machine started normally.

It is found that there are many metal chips in the gap between the magnet and the armature of the torque motor, which is equivalent to reducing the length g of each air gap when the armature is in the middle position. According to the analysis of hydraulic control system, when | X / g | is greater than 1 / 3 (x is the displacement of the end of the armature from the middle position), the armature is always unstable. Therefore, it is considered that the metal chips in the hydraulic system are adsorbed on the permanent magnet, which reduces the air gap length g and destroys the original static characteristics of the torque motor.

(2) Maintenance measures

In view of the causes of the failure, and other possible analysis, the following measures are taken.

① Replace the filter element of oil circuit regularly and clean up the deteriorated oil. As the fault is caused by metal contamination in hydraulic oil, replacing the filter element in the oil circuit of the system regularly and discharging the oil stored in the oil filter can prevent dirt from entering the servo valve, effectively prevent the fault and prolong the operation time of the servo valve. The torque motor and pilot valve are completely immersed in the oil which is connected with the return oil, and the position is at the blind end of the pipeline, where the oil almost does not flow and is easy to be oxidized and deteriorated, so it is necessary to drain the deteriorated hydraulic oil regularly.

② Regular replacement of hydraulic oil, strengthen the management of hydraulic oil. The hydraulic oil will oxidize and coking in the long-term work, and the wear of pumps, valves and cylinders in the hydraulic system will produce some metal chips, which will reduce the quality of the hydraulic oil and cause faults. According to the service cycle of hydraulic oil and the test results of oil products in recent years, the hydraulic oil should be replaced every 10 months to ensure the unplanned shutdown of the equipment.

③ Replace the servo valve regularly. The direct cause of this fault is that the servo valve is not working properly due to the contamination of the torque motor. Therefore, the torque motor and the pilot valve should be cleaned and replaced regularly to prevent contamination and eliminate the fault. The assembly and disassembly of the servo valve should be carried out in a clean environment as far as possible. During the operation, the electrical signal received from the servo valve should be removed first, then the pressure of the hydraulic system should be removed, and then the servo valve should be removed. Clean all parts in a clean, compatible commercial solvent. The parts can be air dried or blown dry with a soft air pipe in clean, dry air. The cleaned servo valve can be used in turn as spare parts to reduce the cost.

④ Regularly replace and check the electrical signal, fasten the wiring terminal to prevent loosening, and check the wiring to prevent poor contact. Servo valve is a precision mechanical and electrical integration product, with high precision and sensitivity to pollution. It has high requirements in maintenance, cleaning and understanding of the importance of maintenance work, so it must be paid enough attention in practical use.

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