The occurrence of cavitation in the hydraulic pump of the cutting machine is another important cause of the fluid noise of the hydraulic pump. It can be seen from the oil suction process of the pump that after a partial vacuum is formed at the inlet of the hydraulic pump, the oil can be pressed into the pump under the action of atmospheric pressure. Therefore, when the hydraulic pump of the hydraulic press is working, a partial vacuum state is present at the suction port. However, if the vacuum of the suction port is too large for some reason and the pressure of the suction port drops below the air separation pressure of the oil, the dissolved air in the oil will escape a lot, resulting in a cavitation of the hydraulic pump. The hydraulic pump produces a lot of noise. The telescopic hydraulic cylinder has two or more stages of pistons. The order of the pistons in the telescopic hydraulic cylinders is from large to small, and the order of empty retraction is generally from small to large. The telescopic cylinder can achieve a long stroke, while the retraction length is shorter and the structure is more compact. Such hydraulic hydraulic cylinders are commonly used in construction machinery and agricultural machinery.
When the PLC controls the electromechanical equipment, the switch quantity sensors such as pressure, temperature, liquid level, travel switch and operation button are connected to the input terminals of the PLC. Each input terminal is assigned a “bit” in the data area of the PLC. A "bit" is an address in memory. Enter the working principle of "bit", as shown in Figure 1. In the figure, IN represents the digital input and COM is the common signal. When IN is ON, the photosensitive three-stage tube is saturated and turned on, otherwise it is turned off. Therefore, the internal circuit of the PLC can "perceive" the presence or absence of the switching signal. Reading the status value of the PLC input bit can be used as a basis for identifying the switch fault signal.
As a kind of high-efficiency and energy-saving motor speed control device, hydraulic compressor frequency converter has been widely used in factories due to its high performance and price ratio. Maintenance, repair, and testing of the frequency converter have become increasingly important, making the inverter test and test platform an indispensable device in the application field. In 2002, Laigang Automation Department designed and set up a frequency converter maintenance test platform. The frequency converter maintenance test platform is mainly composed of two parts, the maintenance part and the test part.
Logic analyzer: The logic analyzer has multiple input channels, reflecting the logic state of the measured signal level and the corresponding time, that is, the binary code of the measured point. The logic analyzer can simultaneously signal the logic level signal, data bus signal, address. The logic relationship between the bus signal, the input and output of the chip, and other digital signals is tested and compared. The transient timing test function of the test instrument itself is used to capture the interference of the narrow pulse and the waveform before and after the test point. The logic analyzer is especially suitable for the pair. Digital logic circuits are tested and analyzed.