Wet sandblasting machine common fault maintenance method and improvement

The wet sandblasting machine produced by Belden Machinery is mainly used for polishing and rust removal of parts in order to reduce the operating noise of the gearbox. In view of the multiple faults in the use of sandblasting machine, on the basis of a simple analysis of the working principle of the equipment, combined with the use and maintenance of practical experience to make some analysis and summary.

1 fault phenomenon and analysis, maintenance and improvement measures

1.1 common fault one

The mixing nozzle or the rubber tube of the mixing nozzle is blocked. (In order to facilitate the analysis and explanation of the cause of the failure, the schematic diagram of the main components of the wet sandblasting machine is attached to us, as shown in Figure 1.) The main reason for the blockage of the mixing nozzle or the rubber tube connected to the mixing nozzle is that the sandblasting machine will inevitably stop after working for a period of time, and the downtime is too long and there are many frosting components in the grinding liquid ratio, after shutdown, the water in the sanding liquid enclosed in the hose will slowly flow into the storage tank, while the sanding will accumulate in the hose and cause the hose to be blocked. The mixing nozzle is fixed at the bottom of the storage tank. To dredge the hose, the grinding liquid in the storage tank must be emptied before drilling into the storage tank to pull out the whole hose for cleaning. Maintenance is very difficult. The sandblasting machine in our factory has all been stirred with compressed air instead of grinding liquid. The air source can be connected with a Φ20mm branch pipe from the main compressed air pipe to the rubber pipe. After the improvement, it has been used for more than a year, the equipment is used normally, and the mixing nozzle has never been blocked.

1.2 Common Faults II

The clogging of the spray gun in the swinging gun group causes the grinding liquid to flow back to the air supply main pipe from the compressed air pipe connected to the spray gun, and then flow from the main pipe to the water filter bowl in the three connected parts of the air source to fill the grinding liquid. Except for a small amount of grinding liquid pipe blockage, most of the cases are due to the blockage of the compressed air pipe with relatively small pipe diameter. Because there is a one-way switch in the compressed air pipe of the spray gun, this switch consists of a rubber plug and a spring (see Figure 2). When working, compressed air is introduced into the air pipe of the spray gun, and the rubber plug is pushed open by means of air pressure to overcome the elastic force of the spring, in theory, when the compressed air stops, the rubber plug should be pushed up under the action of the spring force to close the air inlet pipe to prevent the sanding liquid from flowing back through the air pipe. However, due to the fatigue damage of the spring, the decrease of the elastic force or the interference of the abrasive fluid around the one-way switch, the rubber plug cannot completely close the pipeline, and the abrasive fluid at this time will flow back to the air pipeline with relatively low pressure along the gap. In order to prevent the backflow of sanding liquid, it is necessary to: 1) pay attention to the spray of compressed air and sanding liquid from the spray gun when the sandblasting machine is working, and dredge the phenomenon of blockage and flow reduction of air or sanding liquid in time; 2) Replace the damaged spray gun with one-way switch in time; 3) Turn on the compressed air before starting the grinding pump (the random instruction manual stipulates that it is easy to block the spray gun before starting the sand pump and starting the air source), when shutting down, first turn off the grinding liquid pump and then turn off the air; 4) A check valve for compressed air is installed on the compressed air inlet pipe of the spray gun, which can effectively prevent the sanding liquid from flowing back into the air source pipe from the spray gun.

1.3 Common Faults III

The combined cylinder with valve and switch (see Fig. 3) has no action. When the cylinder does not move, the spray gun cannot swing. The gas-sanding fluid is injected at a narrow fixed point. The operator must continuously move the parts, which has low production efficiency and high labor intensity. The machine adopts the stroke signal switch is directly installed on the cylinder, and a permanent magnetic rubber ring is arranged on the cylinder piston to form a cylinder with a magnetic switch, so that the cylinder stroke detection is convenient and the cylinder structure is more compact. When the piston moves to make the magnetic ring close to the magnetic switch (model CSlF), the reed of the switch is magnetized and in contact with each other. When the piston leaves, the reed is demagnetized, and the two reeds are fragmented, the switch is disconnected. The power-on operation of the two magnetic switches can be judged from the light-emitting diodes. The cylinder reversing is controlled by a double-controlled direct-acting three-position five-way electromagnetic reversing valve (model 4V 330C -l0 -AC 220V). After the solenoid coil is powered on, the valve core of the reversing valve relies on increased air pressure to move the valve core to change the gas path to realize reversing. The function of the RRSL-0 2 type muffler throttle valve is to drive the plunger valve adjusted by thread to adjust the opening of the throttle hole by manual rotation, thereby adjusting the speed of the piston rod. The muffler for the valve is directly installed on the exhaust port of the valve by rib connection, and the muffler element is made of metal sintering.

There are two main reasons for the failure of the combined cylinder: 1) There is no compressed air or low pressure in the intake pipe of the electromagnetic reversing valve. This is because the compressed air first needs to pass through the water separation filter in the air source three-piece to filter out moisture and fine dust. The filter element material of the water separation filter is sintered with bronze and resin, and its pores are only 5μm. The solid dust particles and impurities suspended in the air are filtered out through the sintered filter element with porous structure. When there is more dirt on the surface of the filter element, the compressed air is blocked, resulting in that the compressed air cannot reach the electromagnetic reversing valve through the air, therefore, it is necessary to clean the filter element of the water separation filter in time to eliminate dirt and moisture (compressed air can be used to blow). After cleaning the filter element, check the pressure reducing valve of the three connected parts of the air source. After removing the pressure reducing valve, purge the air outlet of the pressure reducing valve with compressed air to make it unblocked. In this way, the intake pressure of the electromagnetic reversing valve can be effectively increased. After the intake pressure of the electromagnetic reversing valve reaches 3~4 kgf/cm2, the cylinder connecting rod can easily move back and forth. 2) The compressed air entering the electromagnetic reversing valve is not clean. Lead to the accumulation of dirt in the spool, increase the friction of the spool movement, destroy the smoothness of the valve hole, not only pull the cylinder, aggravate the wear of the piston ring, guide ring, and O-ring, but also affect the movement of the solenoid control valve. At this time, the solenoid valve should be disassembled as soon as possible, and the valve core should be carefully cleaned and dried. If necessary, the valve hole should be carefully ground with metallographic sandpaper to restore the smoothness. It is qualified when the valve core can be easily moved by gently pushing by hand. If the piston rod movement is still intermittent and sluggish after installation, check the cylinder, because the unclean compressed air will pollute the cylinder while polluting the solenoid valve. Carefully clean and dry the dirt such as scrub in the cylinder, especially check whether the permanent magnetic rubber ring on the piston is dirty and damaged. Dirty, broken magnetic rubber rings can cause the magnetic switch to not detect the cylinder stroke correctly. Check the dynamic seal between the piston ring and the cylinder barrel, and the static seal between the piston rod and the piston. Replace the piston ring, guide ring and O-ring seal as appropriate. A best solution is to directly separate the compressed air line leading to the air supply triad and the compressed air line leading to the spray gun in the case of multiple compressed air sources.

2 Conclusion

The above common faults are interrelated and cause and effect each other. All fault points must be found out during maintenance. On the basis of clarifying the working principle of the machine, according to the maintenance and improvement methods of sandblasting machine provided by us, frequent inspection and maintenance are carried out to remove all hidden faults. Only in this way can the equipment work normally for a long time after maintenance.