How to Select Air Compressor in Numerical Control Workshop

The main parameters of 1. air compressor selection

1. Exhaust volume

the traditional method of determining the compressed air requirements of a new plant: add up the gas consumption (m3/min) of all gas-using equipment, and then consider adding a safety, leakage and development factor.

Here, ten CNC machine tools are used to clean iron filings and turntable tool holders as an example, assuming that each CNC machine tool is equipped with an air gun. Since it is only used for cleaning, according to experience, the displacement required for each machine tool is about 0.2 m3/min. Therefore, the gas consumption of ten units is about 2 m 3/min. Considering the addition of a safety and leakage relationship, the system uses 2.4 m3/min of exhaust gas.

2. Exhaust pressure

when purchasing an air compressor, first determine the working pressure required at the gas end, add a margin of 0.1-0.2 MPa, and finally determine the pressure of the air compressor (the margin is to consider the pressure loss of the pipeline distance from the installation site of the air compressor to the actual gas end, and appropriately consider the pressure margin between 0.1-0.2 MPa according to the length of the distance). Of course, the size of the pipeline diameter and the number of turning points are also factors that affect the pressure loss. The larger the pipeline diameter and the fewer turning points, the smaller the pressure loss; on the contrary, the greater the pressure loss. Therefore, when the distance between the air compressor and each gas end pipeline is too far, the main pipe diameter should be appropriately enlarged. If the environmental conditions meet the installation requirements of the air compressor and the working conditions permit, it can be installed nearby at the gas end.

According to the gas requirements of CNC machine tools, the pressure is usually about 0.5Mpa. According to the installation requirements of the specific workshop, a pressure margin of 0.1-0.2MPa can be considered. Therefore, the exhaust pressure of the system is selected at 0.7MPa.

3. Power supply capacity

before determining the power supply capacity, first understand the relationship between power, working pressure and exhaust flow. Under the condition of constant power, when the rotation speed changes, the volume flow and working pressure also change accordingly. For example, for a 22KW air compressor, the working pressure is determined to be 7bar during manufacture, the rotation speed is calculated according to the technical curve of the compressor host, and the displacement is 3.8 m3/min; when the working pressure is determined to be 8bar, the speed must be reduced (otherwise the drive motor will be overloaded). At this time, the displacement is 3.6 m3/min; because the speed is reduced, the exhaust is reduced accordingly, and so on. The selection of power is to meet the working pressure and volume flow conditions, the power supply capacity can meet the matching drive motor power can be.

4. Quality requirements of compressed air

according to different uses, the requirements for compressed gas will also have corresponding quality requirements. Commonly used purification equipment is: gas storage tank, dryer (frozen and adsorption), filter and other three. When selecting purification equipment, the corresponding purification equipment can be selected according to the specific gas requirements. Here because our system requirements are only used to clean the machine tool, so the requirements for compressed gas is not very high, the choice of purification equipment, we only choose the gas tank. The size of the gas storage tank can be configured according to 20% of the exhaust volume.

The air storage tank is used to store compressed air; buffer pressure, because the pressure of the air discharged from the compressor fluctuates to a certain extent, the compressed air pressure at the air end can be used more stably after the air storage tank is installed; pre-dewatering, part of the water vapor in the air has formed liquid water droplets after being compressed by the compressor. Most of these water droplets will deposit at the bottom of the air storage tank. There is a drain valve at the bottom of the air storage tank, which can be manually or automatically.

5. Air-conditioning mode

the air-cooling method can be selected according to the specific installation environment. Since there is no special requirement, in order to facilitate installation and maintenance, the air-cooling method is selected here.

2. matching scheme and cost evaluation

there are many types of air compressors, which are roughly divided into piston type, sliding type and screw type. With the continuous updating of technology, the piston air compressor is gradually eliminated due to the shortcomings of low gas production quality and high noise. The screw type and thin film air compressor have been relatively mature in technology from the aspects of gas production quality and noise reduction, and are gradually occupying the main market. However, due to the relatively complex structure of the slide type, it increases the difficulty and cost of maintenance, so the screw type air compressor is more popular with customers in the market.