Fluid-Air Products Inc. | Tech Tips

TECH TIPS - ELECTROSTATICS

What is the advantage and disadvantage of electrostatic / conventional airless and air spray? Does electrostatics work only when spraying metal pieces? Why should I choose an electrostatic spray gun over a conventional spray gun? How does a rotary atomizer work and where should I consider using one? Why should I need to purchase equipment geared specifically for a waterborne paint? Can electrostatics be used to paint something other than metal? Will painting electrostatically provide better adhesion? Can waterborne paints be sprayed electrostatically? What needs to be grounded when using electrostatic guns? What is the best way to check the voltage of an electrostatic gun? What is the difference between a cascade and a classic type power supply? Preventative Maintenance for your Ransburg REA Guns; REM Guns, No. 2 Process Guns Is your powder coating operation a dusty mess? Do I need to maintain 45 to 60% relative humidity for ideal powder coating conditions?
Q.	What is the advantage and disadvantage of electrostatic/conventional airless and air spray?
A.	The finish required between an airless gun and an Electrostatic Air Spray gun are significant. Even ambient conditions can make a large difference. In general, the electrostatics works best on small particles such as are common with an Air Spray product. Conventional airless produces larger particles and a high directional velocity and usually have a much higher fluid delivery than does Electrostatic Air Spray. In basics, the Electrostatics Air Spray offers more gain in efficiency and a much higher finish quality than airless. If the product is currently sprayed airless and a higher efficiency is needed, the best route is to go to an Electrostatic Air Assisted Airless technology. The operator can use the same pump/system as his old Airless and all that is needed is a small air compressor for the gun.
Q.	Does electrostatics work only when spraying metal pieces?
A.	No, nearly any piece can be sprayed electrostatically. If the electrostatically charge paint "sees" a conductive grounded surface it will be attracted to it. A nonconductive piece can be sprayed electrostatically by either putting it between the applicator and a conductive grounded surface or spraying the piece conventionally with a conductive primer.
Q.	Why should I choose an electrostatic spray gun over a conventional spray gun?
A.	Although an electrostatic gun may cost more, it has many advantages over a conventional spray gun. An electrostatic gun has a very high transfer efficiency (40-98%) which results in a lower paint cost, less VOCs, less cleanup and faster production.
Q.	How does a rotary atomizer work and where should I consider using one?
A.	If you're looking for high fluid delivery (up to 1500 cc/min), an even finish, and automation, you may want to consider a rotary atomizer. A rotary atomizer works by spinning a bell or disk at high speed (up to 40,000 RPM). This high speed, along with the serrated edge of the bell or disk, provides an excellent means for atomization.
Q.	Why should I need to purchase equipment geared specifically for a waterborne paint?
A.	Waterborne paints are highly conductive. As a result, the paint supply and fluid lines must be isolated. Power supplies must also be designed to accommodate for the inherit high current draw of waterborne paints. Spraying waterborne paint through a solvent-borne system is dangerous and may result in equipment damage.
Q.	Can electrostatics be used to paint something other than metal? If so, will you get the same benefits as spraying metal electrostatically?
A.	Almost any product can be finished electrostatically. Some may require pretreatment with chemical sensitizers to produce a conductive surface. With some products, a metal object may be placed behind the part to create a ground image for attraction. Many black rubber items have enough carbon content to be sprayable. Others, such as wood parts, sometimes have enough moisture to produce a ground sufficient to spray electrostatically. The many advantages and savings associated with electrostatic spraying justify the application of a pretreatment or preparation product. Material, maintenance, labor and filter savings alone help justify an electrostatic application, not to mention increased production.
Q.	Will painting electrostatically provide better adhesion?
A.	Painting electrostatically will give better transfer efficiency (more paint on the part) but not better adhesion. Adhesion depends on the condition of the substrate and the properties of the paint. Painting, in general, electrostatic or conventional, requires the same type of properly prepped surface before applying paint. Proper preparation is an important key to a good paint job.
Q.	Can waterborne paints be sprayed electrostatically?
A.	Yes. Waterborne paints are the most conductive paints made. This makes them ideal for electrostatic applications. However, when spraying waterborne paint electrostatically, the charge will be carried back to the fluid-supply system. Therefore, spraying waterborne paint electrostatically requires isolating the paint-supply system from contact with people. Special hardware is required, such as an isolation stand and cage or voltage-blocking system. Various types of isolation devices are available, depending on the application and manufacturer.
Q.	What needs to be grounded when using electrostatic guns?
A.	All of the equipment, personnel and target parts in the spray booth area must be grounded. Any ungrounded object, or person, in the spray area can become electrically charged. Improper grounding can result in static sparking which can cause fire or electric shock.
Q.	What is the best way to check the voltage of an electrostatic gun?
A.	There are several ways to check the voltage of an electrostatic gun. The best way to check the voltage is to have a PRO Electrostatic test equipment kit. Included in this kit are the high voltage probe and meter, the PRO Cartridge and Alternator test fixture, and the alignment sleeve for use with all of the Pro Guns and power supplies. With this kit, you are assured of accurate voltage measurements of both the electrostatic gun and power supply.
Q:	What is the difference between a cascade and a classic type power supply?
A:	A cascade type power supply sends out a low voltage that is then stepped up at the transformer on the gun. A classic type immediately sends out the required high voltage.
Q.	Preventative Maintenance
A.	Click on this link for a chart of essential maintenance procedures for electrostatic guns.
Q.	Is your powder coating operation a dusty mess?
A.	Are you wasting time and powder scooping your coating materials by hand from the box into your hopper? One way you can reduce the amount of dust accumulation into your work environment is to use a specially designed unit that moves powder from the supplier's container into your hopper automatically - no dust, no mess, no waste! Powder coatings are typically a mixture of pigments, resins and additives that are processed and ground to a fine powder. When conveying the powder, it becomes a mixture of air and dust that can be difficult to control. Using a dense phase powder feed unit to assist you might be the answer to help you create a cleaner, safer, dust-free powder coating environment. The FPS-14 Fresh Powder System from ITW Gema was designed for just this purpose - to convey powder with minimal dust and waste. This type of feeder unit takes powder from the supplier's shipping container and pumps it directly into your coating system with minimal air. It does not use the typical venturi style pump, which mixes powder and air, creating significant amounts of process dust. Instead, it features a dense phase pump that loads the material in dense form through the hose with minimal compressed air behind it. This dense delivery allows the powder to be deposited into the container without creating excessive dust, helping you bust the dust for a smoother, cleaner operation.
Q.	Do I need to maintain 45 to 60% relative humidity for ideal powder coating conditions?
A.	The relative humidity of 45 to 60 percent is important for a few reasons. First, we are creating a corona field of charge around the gun via the electrode on the front of the gun. The moisture in the air is necessary to facilitate the ion bombardment on the particle to be charged. We are ionizing the powder particles and moisture in the air. if the moisture content is too low, the corona filed is not as effective and results in lower transfer efficiency of the application process. Also, if the humidity is too low, there is a tendency for the material to create a tribo charge, which strips away negative ions and leaves the powder with a positive charge. We typically use negative charge for our corona guns. Relative humidity of the environment is important because if it is too humid, the powder will not fluidize as well or will create impact fusion. Too much moisture may seem obvious, but the powder will agglomerate when too moist. Therefore, maintaining 45 to 60 percent relative humidity is most effective in creating the ideal powder coating environment for most powders. As in most manufacturing processes, controlling variables within the process produces fewer rejects and reduces costs associated with rework and scrap. The bottom line is that changes in humidity can cause fluctuations in application deposition weights, thus increasing your reject rate. Maintaining relative humidity of 45 to 60 percent contributes to a consistent finish and reduced rejects.