Maintenance method and improvement of common faults of wet sandblasting machine

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 frequent failures in the use of the sandblasting machine, based on a simple analysis of the working principle of the equipment, combined with the practical experience of use and maintenance to make some analysis and summaries.
1 Fault phenomenon and analysis, maintenance and improvement measures
1.1  Common failure one
The mixing nozzle or the rubber tube connected to the mixing nozzle is blocked. (In order to facilitate the analysis and explanation of the cause of the failure, the principle diagram of the main components of the wet sandblasting machine is attached to us, see Figure 1) The main reason for the clogging of the mixing nozzle or the rubber tube of the mixing nozzle is that the sandblasting machine will inevitably stop after working for a period of time. , The downtime is too long and there are more abrasive components in the grinding fluid ratio. After the shutdown, the water in the abrasive fluid enclosed in the hose will slowly flow into the storage tank, and the frost will accumulate in the hose and cause the hose to block. The mixing nozzle is fixed at the bottom of the storage tank. To unblock the hose, the tank must be emptied for grinding fluid and then drilled into the tank to pull out the entire hose for cleaning, which is very difficult to maintain. The sandblasting machines in our factory have now all used compressed air to replace the grinding fluid for mixing. The air source can be connected from the main compressed air pipe with a Φ 20 mm branch pipe to the hose. 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 failure two
The blockage of the spray gun in the swing sweeping gun group causes the grinding fluid to flow back from the compressed air pipe connected to the spray gun to the air supply main pipe, and then flows from the main pipe to the water filter cup in the air source three-connected piece, so that it is filled with frosting liquid. Except for a small amount of clogging of the spray gun, the grinding fluid pipe is blocked. In most cases, the compressed air pipe with a relatively small diameter is blocked. Because there is a one-way switch in the compressed air pipe of the spray gun. Figure 2), when working, compressed air is introduced into the air pipe of the spray gun, and the rubber plug is pushed open by the air pressure to overcome the spring force. When the compressed air stops, theoretically, the rubber plug should be lifted up under the action of the spring force to close the air inlet pipe when the compressed air stops. , Prevent the backflow of the frosting liquid from the air pipe. However, due to spring fatigue damage, reduced elasticity, or the interference of frosting fluid around the one-way switch, the rubber plug cannot completely seal the pipeline. At this time, the frosting fluid will flow back through the gap to the air pipeline with relatively low pressure. In order to prevent the backflow of the scrubbing liquid, it is necessary to: 1) When the sandblasting machine is working, pay attention to the spray gun compressed air and scrubbing liquid. If it is found that the air or scrubbing liquid is blocked and the flow rate is reduced, it should be cleared in time; 2) For the one-way switch The damaged spray gun should be replaced in time; 3) When starting up, turn on the compressed air and then start the grinding liquid pump (the random instruction manual stipulates that the sand pump is started first and then the air source is easy to block the spray gun). When shutting down, turn off the grinding liquid pump and then turn off the air. 4) Install a compressed air check valve on the compressed air intake pipe of the spray gun, which can effectively prevent the backflow of the abrasive liquid from the spray gun to the air source pipe.
1.3  Common failure three
The combined cylinder with valve and switch (see Figure 3) has no action. The spray gun cannot swing when the cylinder is inactive, and the air-abrasive liquid is sprayed at a narrow fixed point. The operator has to constantly move the parts, resulting in low production efficiency and high labor intensity. The machine uses the stroke signal switch to be directly installed on the cylinder, and a permanent magnetic rubber ring is set 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 reeds of the switch are magnetized to attract and contact each other. When the piston leaves, the reeds are demagnetized and the two reeds are disconnected, and the switch is disconnected. The energized working conditions of the two magnetic switches can be judged from the light-emitting diodes. The reversing of the cylinder is controlled by a double electronically controlled direct-acting three-position five-way electromagnetic reversing valve (model 4V 330C -l0 -AC 220V). The spool moves to change the gas path to achieve reversal. The role of RRSL-0 2 muffler throttle valve is to drive the plunger valve adjusted by the thread to adjust the opening of the orifice through manual rotation, thereby adjusting the speed of the piston rod movement. The valve muffler is directly installed on the exhaust port of the valve by means of rib connection, and the muffler element is made of metal sintered material.
There are two main reasons for the failure of the combined cylinder without action: 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 has to filter out moisture and fine dust through the water distribution filter in the three-piece air source. The filter element of the water distribution filter is sintered with bronze and resin. Dust particles and impurities are filtered out through the porous structure of the sintered filter element. When the surface of the filter element has a lot of dirt, the compressed air is blocked, causing the compressed air to not reach the electromagnetic reversing valve through the air source three-piece, so it is necessary to clean the water separation filter in time Filter element to remove dirt and moisture (can be blown with compressed air). After cleaning the filter element, check the pressure reducing valve of the three-piece air source. After removing the decomposition pressure reducing valve, use compressed air to purge the air outlet of the pressure reducing valve 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 to 4 kgf/cm2, the cylinder connecting rod can easily move back and forth. 2) The compressed air entering the solenoid valve is not clean. It causes dirt to accumulate in the valve core, increases the friction of the valve core, and destroys the smoothness of the valve hole, which not only roughens the cylinder, aggravates the wear of the piston ring, the guide ring, and the O-ring seal, but also affects the movement of the solenoid control valve. At this time, disassemble the solenoid valve as soon as possible, carefully clean and dry the valve core and other parts, and if necessary, carefully grind the valve hole with metallographic sandpaper to restore the smoothness. It is qualified when the valve core can be easily moved by gently pushing it by hand. After installation, if the movement of the piston rod is still intermittent and sluggish, check the cylinder, because dirty compressed air pollutes the solenoid valve and also pollutes the cylinder. Carefully clean and wipe off the dirt and other dirt in the cylinder, especially the piston. Whether the upper permanent magnetic rubber ring is dirty or damaged. Dirty and damaged magnetic rubber ring will make the magnetic switch unable to detect the cylinder stroke correctly. Check the dynamic seal between the piston ring and the cylinder, the static seal between the piston rod and the piston, and replace the piston ring, guide ring, and O-ring seal as appropriate. One of the best solutions is to directly separate the compressed air pipeline leading to the three-piece air source from the compressed air pipeline leading to the spray gun when there are multiple compressed air sources.
2  Conclusion
The above common fault phenomena are interrelated and mutually cause and effect. When repairing, be sure to find all the fault points. On the basis of clarifying the working principle of the machine, follow the repair and improvement methods of the sandblasting machine provided by us, and perform frequent inspections and maintenance to clear all faults. Hidden dangers can ensure that the equipment can work normally for a long time after maintenance.