Calculation method of cylinder speed The speed of the cylinder piston is related to the air pressure, cylinder diameter, friction, and external resistance during the entire movement process, so the speed changes. The relationship between the operating speed of the piston and the speed is the speed control valve (exhaust throttle valve), which is often used to adjust the speed of the cylinder. It is generally recognized that the maximum speed of the cylinder when there is no load is the theoretical reference speed, and the speed of the cylinder will gradually decrease with the increase of the load during use.
The average speed of the cylinder is divided by the movement stroke of the cylinder by the action time of the cylinder, so the action time of the cylinder should be measured first. It is almost impossible to calculate its average speed by borrowing the formula, but it can be approximated. The relationship between it and the speed is: the speed is 1.4 times the average speed. When the cylinder is not loaded, it is assumed that the exhaust side exhausts at the speed of sound (Note: the exhaust air flow is almost unobstructed), the theoretical reference speed of the cylinder: u0 =1920 * S/A (mm/s) S is the effective synthesis of the exhaust circuit The cross-sectional area, A is the effective area of the piston on the exhaust side. At this time, the speed of the cylinder is approximately equal to u0. The standard speed range of the cylinder is 50-500mm/s. Under normal circumstances, the speed of the cylinder is adjusted to the standard speed range through the throttle valve, which is related to the load on the cylinder.
When the speed is less than 50mm/s, which is estimated to be 20-30mm/s, due to the increased influence of the frictional resistance of the cylinder and the compressibility of the gas, the smooth movement of the piston cannot be guaranteed, and the phenomenon of stop and go will appear. for "crawling". In order for the cylinder to work at low speed, a gas-liquid damping cylinder should be used, or a gas-liquid combined cylinder should be used for low-speed control through a gas-liquid converter. When the speed is higher than 500mm/s, the friction and heat generation of the cylinder sealing ring will increase, which will accelerate the wear of the seals, cause air leakage, shorten the service life, and increase the impact force at the end of the stroke, which will affect the mechanical life. In order to work at higher speeds, it is necessary to lengthen the length of the cylinder barrel, improve the machining accuracy of the cylinder barrel, improve the material of the sealing ring to reduce frictional resistance, and improve the cushioning performance.
Therefore, it is not good to be too large or too small, and a very suitable one should be selected, and it should be within the specified range. Taking the SMC cylinder as an example, the ordinary CM2 cylinder runs at a speed of 50-750mm/s, the speed control valve is fully open, and can reach 750mm/s, and the speed control valve is closed smaller, and the speed can reach below 50mm/s, and then it will crawl (shakes and shakes). The air velocity is generally about 30m/s. The working pressure of the cylinder is generally 0.6 MPa, and it can be used normally at 0.3-0.8 MPa.