In order to make the spraying equipment play a greater role in the automotive repair coating, after the equipment is selected, it should be regulated and maintained.
1. Control of spraying parameters
Things that often need to be adjusted during the spraying process include paint viscosity and flow rate, atomizing air pressure, and reducing the amount of mist and bounce paint.
(1) The viscosity of the paint is the key factor affecting the atomization effect of the paint, so it is necessary to choose the method of heating, increasing the temperature of the paint to reduce its viscosity and changing the solvent content in the paint to adjust the paint viscosity according to the actual situation. The most suitable paint viscosity for various paints in repairing and painting is nitro paint and thermoplastic acrylic resin paint, and it is painted with -4 cups of Viscosity Cups (20°C) for 16~18s. Amino alkyd and acrylic thermosetting synthetic resin coatings are 18~25s, and self-drying alkyd coatings are 25~30s.
(2) The flow rate of the paint can be increased by increasing the pressure of the paint and increasing the diameter of the nozzle, but in more cases, the method of increasing the diameter of the nozzle is used. Large paint flow and satisfactory spray effect.
(3) Air atomization pressure Although increasing the hydraulic pressure of the coating can obtain a better atomization effect, but try to achieve a satisfactory spray effect under a lower coating pressure, so it is very important to adjust the air atomization pressure. Proper spray air pressure is all that is needed to get the proper spray, material output and swath width. When the spraying air pressure is too high, it will cause excessive atomization and overspray of the paint. When the suction type or gravity Spray Gun is used, the amount of paint sprayed will be increased, and the utilization rate of the paint will be reduced. Moreover, the solvent has volatilized a lot before the paint reaches the surface to be coated, resulting in poor leveling and other coating defects. Therefore, the spraying air pressure cannot exceed 0.6~0.7MPa, but if the spraying air pressure is too low, the spray width will be reduced, the center of the spray pattern will become thicker, the atomization will be poor, and the solvent volatilization will slow down, which will affect the drying of the coating film and cause sagging and other disadvantages. Therefore, the spraying air pressure should be adjusted by checking the spray pattern before spraying. The principle is "as long as the atomization shape is correct, the atomization pressure is correct", that is, as long as the satisfactory atomization effect can be obtained, the pressure is sufficient at this time, and the atomization pressure should not be increased.
(4) Reducing flying paint and rebounding paint The paint particles that fail to reach the workpiece during the spraying process are called flying paint, and the paint mist particles splashed from the surface of the workpiece are called rebounding paint. Generally, the purpose of reducing flying paint and rebounding paint can be achieved by reducing the pressure of the compressed air in the system and the hydraulic pressure of the paint.
2. Cleaning and maintenance of equipment
Good maintenance of the equipment is an important guarantee for the good operation of the system, so after the spraying construction is completed, the equipment should be regularly maintained and maintained. In particular, carefully clean the painting equipment to effectively remove the residual paint before it is cured in the equipment. Especially in the case of using two-component paint, this will not only avoid the blockage of the equipment caused by the paint, but also avoid the pollution of the new paint used in the next spraying.
The procedure for cleaning the suction Spray Gun is to unscrew 2~3 buttons of the air nozzle first, pull the trigger, and squeeze the paint in the Spray Gun back into the paint cup. When the paint in the Spray Gun is exhausted, remove the paint cup, remove the residual paint in the cup, and then fill half a cup of cleaning solvent with good solubility for paint. Install the paint cup on the gun, tighten the air cap, pull the trigger to spray solvent to clean the paint channel of the Spray Gun, and repeat the operation until the sprayed solvent does not contain paint completely.
The steps to clean the pressure-fed air Spray Gun are: firstly remove the pressure in the pressure tank, unscrew the air nozzle on the Spray Gun, and then pull the trigger to make the paint return to the paint pressure tank. With the air nozzle removed, pour any remaining paint from the paint can back into the paint storage can. Then add a cleaning solvent with good compatibility with the paint to the paint pressure tank. To clean the paint tank and Spray Gun, it is not necessary to install the air cap at this time, and the gun is fired to spray the solvent until the clean solvent flows out completely.
After cleaning the Spray Gun, remove the air cap, soak the Spray Gun head in a clean solvent for cleaning, and use a soft brush dipped in solvent to clean the air cap and paint nozzle. If the nozzle is blocked by paint, do not use metal tools. To dredge, you can only use a brush or toothpick to clean, but do not soak the entire Spray Gun in solvent, so as not to damage the sealing gaskets of various parts and cause air leakage, paint leakage, etc., and check the sealing of needle valve gaskets and other If there is leakage, it should be replaced in time, and the sealing gasket should be oiled to facilitate sliding. Other mechanical parts should also be oiled frequently to ensure flexible activities.
After the work is completed every day, the Air Compressor and the air supply pipeline should be cleaned and the moisture removed, and the wearing parts should be replaced regularly to ensure the normal operation of the system.
