Three major issues of hydraulic cylinders: working principle, installation and maintenance
One, the working principle of hydraulic cylinder:
1. Piston-type hydraulic oil cylinder: When working, it is mainly to alternately deliver hydraulic oil to both sides of the piston in the oil cylinder, and use the pressure difference between the hydraulic oil on both sides of the piston to realize the reciprocating movement of the piston. If you want to speed up the forward speed of the piston, the return oil in the cylinder can be controlled by the valve and input into the oil inlet pipe to participate in the work of pushing the piston to realize the rapid movement of the piston, and the thrust of the piston is greatly reduced.
2. Plunger type hydraulic cylinder: The difference from piston type hydraulic cylinder is that the piston in the hydraulic cylinder is replaced by a shaft plunger. This type of cylinder is mostly used in hydraulic transmission that requires a long mechanical stroke, and it can only be used from one Input pressure oil in one direction and pressurize in one direction to form thrust to push the plunger to move. Some of the plunger's return stroke is down by the plunger's own weight, while others are pushed back to the original position by the elastic force of the spring.
3. Compound cylinder: The mold-moving cylinder is a plunger cylinder. When the hydraulic oil enters the cylinder from the plunger hole, the mold clamping device moves forward quickly; when the mold clamping is close to end, the mold clamping cylinder (piston cylinder) enters the hydraulic pressure After the oil cylinder, the stroke speed becomes slower, so that the clamping force reaches the required tonnage. This kind of plunger and piston cylinders are called composite hydraulic cylinders.
Two, precautions for the installation of hydraulic cylinders
1. The hydraulic cylinder and surrounding environment should be clean. The fuel tank must be sealed to prevent contamination. Pipelines and fuel tanks should be cleaned to prevent falling off iron oxide scale and other debris. Use lint-free cloth or special paper for cleaning. Can not try twine and adhesive as sealing materials. The hydraulic oil is designed according to the design requirements, pay attention to the changes of oil temperature and oil pressure. When no load, unscrew the exhaust bolt to exhaust.
2. There must be no slack in the piping link.
3. The base of the hydraulic cylinder must have sufficient rigidity, otherwise the cylinder tube will bow upwards when pressurizing, causing the piston rod to bend.
4. Before installing the hydraulic cylinder into the system, compare the parameters on the hydraulic cylinder label with the parameters when ordering.
5. The central axis of the movable cylinder with a fixed foot base should be concentric with the midline of the load force to avoid causing lateral force, which is likely to cause seal wear and piston damage. When installing the hydraulic cylinder of the moving object, keep the direction of movement of the cylinder and the moving object on the guide rail surface parallel, and the parallelism is generally not more than 0.05mm/m.
6. Install the sealing gland screw of the hydraulic cylinder, and its tightening degree is to ensure that the piston can move flexibly in the full stroke, without obstruction and unevenness of weight. Screws that are too tight will increase resistance and accelerate wear; too loose will cause oil leakage.
7. For hydraulic cylinders with exhaust valve or exhaust rosette, the exhaust valve or exhaust rose must be installed at the highest point to remove air.
8. The axial ends of the cylinder cannot be fixed, and one end must be kept floating to prevent the influence of thermal expansion. Due to the hydraulic pressure and thermal expansion in the cylinder, there is axial expansion and contraction. If both ends of the cylinder are fixed, all parts of the cylinder will be deformed.
9. The clearance between the guide sleeve and the piston rod must meet the requirements.
10. Pay attention to the parallelism and straightness of the cylinder and the guide rail, the deviation should be within 0.1 mm/full length. If the total length of the bus bar on the hydraulic cylinder is out of tolerance, scrape the bottom surface of the hydraulic cylinder support or the contact surface of the machine tool to meet the requirements; if the side bus bar is out of tolerance, you can loosen the hydraulic cylinder and the fixing screws, pull out the positioning lock, and correct the accuracy of its side busbar.
11. When disassembling and assembling the hydraulic cylinder, take care to prevent damage to the thread on the top of the piston rod, the thread of the cylinder port and the surface of the piston rod. It is strictly forbidden to hammer the surface of the cylinder and the piston. If the surface of the cylinder bore and the piston is damaged, it is not allowed to polish with sandpaper, but must be carefully polished with fine oil stone.
12. The hydraulic cylinder and surrounding environment should be clean. The fuel tank must be sealed to prevent contamination. Pipelines and fuel tanks should be cleaned to prevent falling off iron oxide scale and other debris. Use lint-free cloth or special paper for cleaning. Can‘t try twine and adhesive as sealing materials. The hydraulic oil is designed according to the design requirements, pay attention to the changes of oil temperature and oil pressure. When no load, unscrew the exhaust bolt to exhaust.
Three, the correct maintenance and maintenance of hydraulic cylinders
1. The hydraulic oil should be replaced regularly during the use of the cylinder, and the filter screen of the system should be cleaned to ensure cleanliness and prolong its service life.
2. Each time the cylinder is used, it must be fully extended and fully retracted for 5 strokes, and then run with load. Why do you do this? This can exhaust the air in the system and preheat the systems, which can effectively avoid the presence of air or water in the system, causing gas explosion (or scorching) in the cylinder body, which will damage the seals, Causing failures such as leakage in the cylinder.
3. Control the system temperature. Excessive oil temperature will reduce the service life of the seals. Long-term high oil temperature will cause permanent deformation of the seals or even complete failure.
4. Protect the outer surface of the piston rod to prevent bumps and scratches from damaging the seals. Frequently clean up the dust on the dust ring of the cylinder and the exposed piston rod to prevent sticking to the surface of the piston rod. Dirt enters the cylinder and damages the piston, cylinder or seal.
5. Frequently check the connections of threads, bolts, etc., and tighten them immediately if they are loose.
6. Lubricate the joints frequently to prevent rust or abnormal wear when there is no oil.