Application of compressed air in sandblasting equipment

Application of compressed air in sandblasting equipment

For a long time, the compressed air produced by the air compressor unit is not only widely used in machine tool equipment in the machining industry, but also widely used in the metal surface processing industry. For example, sandblasting equipment is a more obvious example. Remove the surface oxide scale (corrosion), residual salt and welding slag of metal parts, welded parts, castings, forgings, etc. after heat treatment; clean up small burrs, burrs, and surface residues of machined parts; change the surface roughness Ra value of the workpiece; Pretreatment processing before spraying and electroplating on the surface of the workpiece can obtain an active surface and improve the adhesion of spraying and electroplating; it is used for the finishing of parts with high precision and complex shapes that are difficult to complete by other processing methods; old parts refurbishment and other machinery Sandblasting equipment is required for surface treatment between processes in the processing industry. The main power source of sandblasting equipment is compressed air.

Application of compressed air in sandblasting equipment

The working principle of the sandblasting equipment is to use compressed air to flow in the spray gun at high speed to form negative pressure to produce the ejection effect. The abrasive in the sand separator is sucked into the spray gun through the sand pipe, and then sprayed to the surface of the workpiece by the nozzle at high speed along with the compressed air flow. , To achieve the purpose of sandblasting. In the working state, the compressed air and sand are sprayed while mixing, so that the compressed air can be fully utilized. The air flow and the sand flow can be adjusted appropriately to obtain an ideal mixing ratio, so that the ideal metal surface processing can be obtained with less energy and sand consumption.

　　The main components of the sandblasting equipment are composed of the main engine, cyclone separator, spray gun swing system, dust removal system, electrical system, air compressor (user-provided), and control box.

　　Compressed air pressure adjustment:

　　Adjust the regulating valve to control the pressure of compressed air entering the spray gun according to the work needs. The working pressure can be selected in the range of 3 to 7 bar.

Application of compressed air in sandblasting equipment

　　 It can be seen from the above table that in the production process of sandblasting equipment, the use of compressed air is relatively large. High pressure and sufficient air volume are the prerequisites to ensure the normal use of sandblasting equipment. It needs dry compressed air with a pressure of 0.4～0.7MPa and a flow of about 1m3/min/gun.

The specific steps of sandblasting equipment: turn on the power and lighting before sandblasting, adjust the position and angle of the swing gun-load the workpiece on the turntable-close the door-adjust the sandblasting parameters (turntable speed, gun swing speed) -Start sand blasting work-The sprayed sand falls into the bottom of the main engine and passes through the sand return pipe-Cyclone-The useful sand is temporarily stored in the sand storage box-At the same time, the dust is sucked into the filter element dust removal system under the negative pressure of the fan for filtration After the clean air is discharged into the atmosphere-after the sandblasting is completed, it is automatically blown off-the hatch is opened-the workpiece is unloaded and the workpiece to be sprayed is placed on the turntable for the next round of work cycle. With manual sandblasting mode, manual sandblasting is also possible. Compressed air enters the spray gun, and the abrasive will be ejected from the bottom of the separator tank into the spray gun according to the adjusted spray volume, and sprayed on the surface of the workpiece at high speed under the action of the compressed air.

　　 What are the quality requirements for compressed air for sandblasting machines?

　　1. The pneumatic system of the sandblasting machine should meet the requirements of GB/T7932 and the "Pressure Vessel Safety Technical Supervision Regulations";

　　2. The working pressure, applicable nozzle opening and air consumption of the sandblasting machine should be clearly defined;

　　3. The sandblasting machine should clearly define the applicable abrasive types and abrasive particle size range;

　　4. The sandblasting machine should be able to work normally under the ambient temperature of -10℃ to 45℃ and relative humidity not more than 90%;

　　 5. The noise sound pressure level of the sandblasting machine should not exceed 85 decibels;

　　 6. The air supply of the air compressor should be greater than 1.25 times the maximum air consumption of the sandblasting machine;

　　 7. The compressed air used by the sandblasting machine must be dry and oil-free.

　　 8. The sandblasting machine should be equipped with safety protection devices.

Therefore, first of all, compressed air is required to have a certain pressure and sufficient flow. Without a certain pressure, the electromagnetic valve cannot be opened, and the control mechanism will not work normally; without sufficient flow, the abrasive of the sandblasting machine cannot be sprayed on the metal surface with the gas. It is difficult to form impact strength. Secondly, compressed air has certain cleanliness and dryness requirements. Cleanliness requires that the oil content in the gas source, the quality of dust and impurities, and the particle size should be controlled within a small range. Dryness refers to the amount of moisture contained in compressed air. The lower the water content of the sandblasting machine, the better. Although the compressed air discharged by the compressor meets certain pressure and flow requirements, the compressed air contains moisture and dust. After being compressed by the air compressor, it is mixed with lubricating oil to form a gaseous mixture In the sandblasting machine, it is mixed with the sprayed abrasive to blast the metal surface of the workpiece, which will cause the surface roughness of the workpiece to fail to meet the quality requirements of the workpiece.

　　 The hardness of the machined parts is high, and compressed air with higher pressure is required. For some special materials or heat-treated workpieces, in order to achieve the specified roughness, in addition to the compressed air with higher pressure, a high-hardness abrasive is also required. For workpieces made of aluminum alloy, titanium alloy, magnesium alloy and other materials, the compressed air pressure should be lowered, because high pressure will damage the surface of the workpiece. Tests are required to determine the process parameters of sandblasting, including compressed air power, abrasive types, particle size, particle shape, and the distance between the nozzle and the workpiece.

　　Sandblasting technology can meet many surface treatment requirements, such as cleaning, texturing, matting, strengthening, deburring, polishing, etc. Different surface treatment requirements require different compressed air. There are many types of abrasives. Some abrasives have very good mechanical properties, high hardness and good toughness. Even if the pressure of compressed air reaches 0.7MPa or more, they still have good impact resistance, such as steel grit. The impact resistance of plastic abrasives is far inferior to that of steel grit. For the main purpose of plastic abrasives and economic considerations, the pressure of compressed air can only be 0.2～0.3MPa, or even lower.

　　 Generally, in order to ensure the surface quality of the processed parts, the air compressor of the sandblasting machine needs to be adjusted from the following aspects:

　　 1. Increase the pressure. Every time the exhaust pressure is increased by 0.01MPa, the flow rate will decrease by 0.04m3/min. If the discharge pressure of 0.7MPa and the discharge pressure of the air compressor unit with a flow rate of 10m3/min are increased to 0.8MPa, the displacement will be reduced to 9.6m3/min.

　　 2. Use time and working conditions of the air compressor. The imported filter is too dirty, which will greatly reduce the displacement of the air compressor unit. Therefore, any air compressor used for sandblasting must be routinely maintained.

　　 3. The influence of altitude. The discharge volume and discharge pressure of an air compressor are usually measured under sea level conditions. Every time the altitude increases by 300m, the discharge volume will decrease by 0.042m3/min. At an altitude of 1500m, the displacement of an air compressor with a displacement of 10m3/min is only 9.8m3/min.

　　 4. Pipeline specifications. If you choose improperly, it will cause severe pressure drop.

　　 In short, the pressure of compressed air has a great influence on the effect and economy of the sandblasting machine, and it needs to be taken seriously. In the absence of reliable basis and grasp, it is best to determine the main process parameters through experiments.