The spray gun is the key component in the finishing system. Each type of gun is precision engineered and is specifically designed to perform certain, defined range of tasks.
Spray guns are available in gravity feed, siphon feed or pressure feed delivery systems. Gravity and siphon feed guns are used for low production or low fluid consumption applications. Pressure feed guns are designed for higher production rates using a pressure pot or pump system to deliver the coatings. Pressure feed spray guns are available for manual operations and automatic finishing systems.
Spray gun types include HVLP (High Volume Low Pressure), Airless, and Air Assist/Air Mix. Each gun type utilizes air atomization to mix with the material at the air cap in a controlled pattern. The type of gun will determine the transfer efficiency of the spray, either landing on its intended target or as over-spray that ends up on the floors, walls and filters.
HVLP spray guns are designed to deliver a high volume of air, at low pressure to atomize coatings into a soft, low velocity pattern. The design of HVLP is to meet new environmental regulations required for many applications for transfer efficiency and to reduce discharge levels. It may be a requirement with some governing authorities to have a test cap assembly available to verify that HVLP guns are being used within regulatory limitations of 10 psi at the tip. Typical transfer efficiency for HVLP is in the 65% range.
Airless spray guns tips breakup fluid pumped at high pressure, ranging from 500 to over 7000 psi. The fan pattern and amount of fluid per minute is determined by the tip size. Most airless spray guns can attain up to a 50% transfer efficiency. Airless spray guns are used for applications where speed is a higher priority than the finish.
Air Assisted or Airmix spray guns utilize high fluid pressure, ranging between 300 to 3500 psi, to atomize the coating through the tip. The air flow will range from 10-30 psi and is designed to assist in the atomization and to control the fan pattern. The technology on Airmix tips has yielded high transfer efficiencies, up to 75%, and better finishes than most HVLP spray guns. Most Air Assist units will yield an average of 60% transfer efficiencies.
Conventional Spray Guns rely on high air pressure for atomization. The conventional spray atomization air pressure creates the finest finish, but the turbulence yields a lot of over-spray and only about a 30% transfer efficiency. This transfer efficiency makes it difficult to comply with many industrial requirements, Conventional guns are a popular choice for applying spray adhesives.
Electrostatic spray guns offer the best overall transfer efficiencies. The coating is charged as it leaves the electrostatic gun, and the grounded parts attract the paint, producing a wrap-around effect reducing over-spray. In many instances, a properly set electrostatic system can achieve 90-95% transfer efficiency. With local regulations on discharge and the high cost of coating, this can yield tremendous savings. Note: the coatings must be formulated to accept the charge from the electrostatic gun. To obtain best results, proper grounding of the parts must be maintained. Manual and automatic electrostatic spray guns are available.
Spare Parts and Rebuilt Kits are available for all the spray guns. Ultrasonic cleaners are excellent for cleaning gun tips and fluid nozzles. Solvent free cleaners offer environmentally friendly options cleaning wet parts.
Spray Gun Care, if done properly, will protect the investment for years to come. The spray gun should never be soaked in solvent or other cleaners. Most of the gun body only has air pass through it. Soaking the gun will compromise the life and effectiveness of seals and other internal components. Wipe down the gun body exterior to prevent build up. The coating only enters the gun near the tip and this is the area that needs to be cleaned.
We are fortunate to be able to offer spray paint equipment and guns from the industry leading manufactures: Graco, EXEL Kremlin, Binks, DeVilbiss, and 3M.