Spray tip size are a critical factor in the spray finishing process. The size of the spray tip determine the amount of material that will exit an nozzle of the spray gun and the way in which the material will atomize. If the spray tip that is used with the material have the incorrect size, then the material will not even coat the object and will create texture like orange peel.
Choosing the correct spray tip is essential to the process, as the spray tip will dictate a fan pattern of the material and the amount of material that is released from the spray gun. A spray tip has two specific number associated with it. The first number represent the orifice diameter of the tip, and the orifice diameter is measured in thousandths of an inch.
How to Choose the Right Spray Tip Size
This diameter act as a gate for the liquid material that is released from the tip. If the liquid that is to be sprayed has a low viscosity, a small orifice diameter are required to provide fine control of the liquid. However, if the liquid have a high viscosity, such as a primer, a larger orifice diameter is required for the spray gun to not clog.
The second number on a spray tip represent the fan width of the tip, and the fan width is measured in inches. The fan width of a spray tip will determine the amount of area that the spray gun will cover. A narrow fan width, such as a four-inch fan width, will allow the spray gun to direct the liquid to small areas and to have fine control over the direction of the material.
Spray guns with a wide fan width, such as an eight inch or ten inch fan width will allow the liquid to cover large areas of an object quickly. The fan width and the orifice diameter of a spray gun must be matched to the viscosity of the material that is to be sprayed. Materials with a low KU measurement will require small orifice diameter to avoid the formation of drips of material.
However, materials with a high KU measurement will require larger orifice diameters to allow the material to flow smooth from the spray gun. The type of coating that will be sprayed will also affect the size of the spray tip. Clear coats and urethanes will require smaller spray tips.
Primers contain solids that is suspended within the liquid, and these solids will clog the spray gun if it has a small orifice; thus, primers will require larger spray tips. Stains will also require smaller spray tips because the flow of the liquid will need to be controlled on vertical surfaces. Marine coatings and sealants contain high amount of pigment, so the liquid will clog the nozzle of the spray gun if the opening is too small.
Thus, marine coatings and sealants will require large spray tips. If the user use the wrong type of spray tip with the wrong type of material, then the material will be wasted. Additionally, the results of the spraying will be poor and the coating will have to be stripped off of the object and applied again.
The fan width will also affect the way in which the material is sprayed. The wider the fan width, the less control that will be provided to the spray gun operator; however, the larger areas will be covered in less passes of the spray gun. A narrow fan width will allow the operator of the spray gun to control the material that is being sprayed but will take longer to complete spraying of the object.
To properly spray an object with a spray gun, the spray gun should be held six inches from the object being sprayed and should be held perpendicular to the object. Additionally, each pass of the spray gun should be overlapped with the next pass by 50 percent so that stripe will not form on the object being sprayed. There are a few common error in the spraying process.
Using a spray tip that is too small for the material will cause the material to sputter and will dry up as it is sprayed. If the spray tip is too large for thin materials, the material will sag from the spray gun. Tilting the spray gun when spraying will warp the material of the spray tip.
Lastly, stationary triggering of the spray gun will cause the material to form blob. The type of spray gun that is used can also impact the size of the spray tip that should be used. HVLP spray guns use low level of pressure to allow the material to exit the nozzle of the spray gun.
Because the pressure is low, the spray tips for HVLP guns have slightly larger openings than those that is used with high pressure models of spray guns. LVLP spray guns are designed to save air; thus, they have spray tips with large openings so that less air is pushed through the nozzle. Airless spray guns are used for high volumes of material; thus, these type of spray guns will have even larger openings for the same reasons.
Understanding the type of spray gun that is being used is essential to properly spray an object. The specifications of a spray gun must align with the specifications of the spray tip. Using the correct spray tip will allow the material to properly flow from the spray gun and will ensure that the material forms an even spray pattern.
