When it comes to the auto spray gun, many people may not know it too well. In fact, the auto spray gun is also called auto atomizing nozzle. But due to its appearance, it is called auto spray gun in the professional term.
It should be known that the auto spray gun has a pneumatic piston mechanism inside. A stainless steel spray needle is installed above the piston, and a set of high tension springs are installed behind the piston. When the supply of compressed air stops, the spring pushes the piston and the spray needle forward. At this time, the spray needle and the nozzle are closely matched with high precision to block the passage of liquid. On the contrary, when the compressed air starts to be supplied, the pressure of the compressed air pushes the piston away, causing a gap between the spray needle and the nozzle to allow the liquid to pass. After spraying, the sprayed liquid immediately comes into contact with the atomizing air to produce an atomizing effect.
Today we will share with you more knowledge about the auto spray guns, including the adjustment methods, important parameters of the auto spray guns, and how to use auto spray guns to achieve the best atomization effect. Let's get to know it together!
The adjustment of the auto spray gun mainly refers to the adjustment of air output and paint output. These are two main factors that are interrelated. If the air output is too small, it is not easy to atomize the paint liquid, and the paint liquid will be dripped and the coating film will be uneven. The amount of paint output corresponds to the amount of air output. Before spraying, adjust the appropriate air output and the corresponding paint output to make the paint liquid can be atomized well and evenly sprayed on the surface. To adjust the auto spray gun, the first main point is listening (know the size of the airflow by listening to the sound of the airflow), and the second is seeing (see the degree of atomization of the spray gun nozzle and the size of the fan area).
① Air pressure: The air pressure for spraying is generally (0.4 to 0.6Mpa);
② Spray width: The width of spraying on the working surface is about 10cm;
③ Spray distance: When spraying, the distance between the nozzle and the object to be sprayed is 15 to 20cm;
④ Moving speed: The moving speed of the spray gun is generally 30 to 60 cm/sec;
⑤ Overlap range: The overlap range of each gun during spraying is 1/2 to 1/3 (except for cracked paint); Spraying angle: The angle between the nozzle and the object to be sprayed is generally 90.
When most spray engineers learn how to use auto spray guns to spray, they are only taught by others' personal example and verbal instruction in the way master teaches apprentices. There is no clear calculation formula to express it and only the experience gained from each failure. Once a technical expert from an Italian spray gun manufacturer visited China to exchange spray technology with technicians in the automotive repair industry in my country. Under the guidance of experts, the following data can be obtained to achieve the best atomization effect:
① The viscosity of the coating should be adjusted between 17 and 20 seconds (4 cups for simple coating), and the spray width knob should be turned to the maximum;
② Tighten the adjustment knob for coating flow rate, then turn it back 2.5 rounds and turn the adjustment knob for compressed air on the tail of the gun to the maximum;
③ The distance between the nozzle of the spray gun and the workpiece is 20cm. The nozzle of the spray gun and the workpiece should maintain a 90 degree right angle, and the running speed of the high quality spray gun is about 80 centimeters per second;
④ The overlap of the spray width is that fog spray and flat spray make up one third and wet spray accounts for two thirds. The interval time of paint (two-component coating) is generally ten to fifteen minutes. Due to the different facilities used and the local climate at the time, the interval time is different, depending on the actual situation.