IN PAINTING PROCESS TECHNOLOGY
It is the oldest system of using spray paint. Had its development in the U.S. by the year 1920 with the growth of mobility and automotive industry.In Brazil, this system is simply known as “spray gun”. In this type of painting (with compressed air) the automation of the product is due to the impact the flow of air, which takes the product to the surface. Next to the piece, the air undergoes a rebound, returning with the ink particles, causing a waste. This is given the name of “over spray”.With standard pistols you can apply a wide range of products, and make surfaces smooth and uniform.There are three types of conventional painting equipment, a product to the atomizing air pressure (35-80 PSI) and moderate flow: • suction guns; • Guns of gravity; • Pistols fed under pressure.
Finishing quality low efficiency
High power spray High material waste
Standard range and flow variables Elevated “over spray” and rebound
Easy handling, operation and maintenance Large air intake
easy maintenance Easily used incorrectly
Transfer efficiency of 25-45%
AIRLESSCreated in 60 years to meet new processes of atomization, now known as airless system.
It is a method of spraying the product of which is perfectly atomized without the need for air.It consists of a pump that generates high pressure (500 to 7000 psi), spraying the product through a special nozzle, attached to the gun.
In this system, you get a better distribution of paint, less pollution in the area of work, and ability to apply thicker layers of coating.Substantially reduces waste, faster application, allowing all kinds of painting (in the cabin, in the open air in the area of work) using all sorts of products (low, medium, high) viscosity, even with high solids (high solid) , and on any surface.
TYPES OF EQUIPMENT AIRLESS
• TYRE: consists of a piston pump to the double effect, driven by an air motor. They are used in industries in general (from the small to the industry);
• ELECTRICAL: due to the greater ease of transport, energy and the possibility of power anywhere, is in use in the favorite works of Construction.
AIRLESS SPRAYING SET COMPLETE
It consists of: pump, hose, gun and nozzle
Pump: aims to get the pressure needed to transfer the desired product (500 to 7000 PSI) to the suction of ink directly from the original container and send it to the gun high pressure;
Hose: is the driver of the product to be applied to high pressure (internally with nylon tubes), varying in length according to each user;
Pistol: its function is to open and close the ink exit (does not have settings), is light
and able to withstand high pressures (usually up to 500 bar);
Nozzle: usually done in tungsten carbide, has a calibrated orifice diameters from 0.007 to 0.072 “in which there is a more or less deep groove that determines the size of the “range” (of3 to 21 inches).
The quality of the nozzle in an airless pump, so obviously determines the quality and distribution of particles inside the spray fan. This influences so remarkable aspect of the final painting.
There are also adjustable nozzle that varies the flow rate and size of the “fan.”
Speed of application extremely
high High flow of product
Fast coverage of large areas Lack of an easy flow control
High deposition Product Industrial quality finish
Reduces the mist of paint, reducing the waste It operates with qualified personnel
Reduces labor costs
Apply high-viscosity materials and high solids
Transfer efficiency : 55-70%
In 70 years, there were various combinations of irrigation systems. The airless seen a system that was developed to fill the need of the escalating costs of material and the EPA regulation (regulator of pollution in the U.S.).
The within airless -assisted ideally combines the best qualities of spraying the air with the best in the airless.
Spray guns System airless-assisted spray the liquid part with a special nozzle similar to an airless spray nozzle.
Moreover, the complete spraying pistols with small amounts of air compressed in the face and / or the tip of the nozzle of air they use. The result is a thin layer of spray similar to the compressed air system.
Finishing quality They are not as flexible as the pistols conventional
High power spray Require training of operators
High rates of application
Low fog and rebound
Transfer efficiency of 65-85%
HVLP (HIGH VOLUME LOW PRESSURE)
The concept of global environmental pollution, there was need for numerous changes including how we give our finishing products.
What is HVLP?
It is a paint system, as its name indicates, it applies a coat of paint using low air pressure 0.1 psi and 10 (at the nozzle of the gun) and high volume (greater than 40 cfm).
This technology significantly improves the control of the spray, resulting in a range therefore more uniform and higher transfer efficiency (amount of ink spray / amount of ink lost), which can range from 65 to 90%. Systems that use conventional guns can lose the overspray (waste) and bounce around 2 / 3 of each gallon).
In HVLP paint system, the user applies paint more evenly on each layer.
The HVLP paint system can be used with most materials of low and medium viscosity, including here, two-component paints, urethanes, acrylics, epoxies, enamels, lacquers, varnishes, primers, etc..
WHAT ARE THE ADVANTAGES OF THE SYSTEM HVLP?
High transfer efficiency, increasing productivity, and quality of finish.
Less overspray, which improves visibility, limiting the possibility of errors operator.
High transfer efficiency provides a less aggression to the environment because it allows lower emissions of paint and more accurate applications. Reduces deposits on adjacent surfaces decreasing finishing imperfections.
Reduces ink consumption, therefore reducing the maintenance of cabin painting
High rates of application Requires high pressure pump
Apply high-viscosity materials Require skilled operators
Less flow than the airless spray Small hole for passage of fluid, easily blocked
Low fog and rebound Restricted possibility of variation
Transfer efficiency of 50-85%
II During the World War, paints and solvents were scarce or too expensive. To fill the need and maximize the use of these materials, electrostatic spraying was created.
The first layer is sprayed using compressed air, airless, or methods of assisted-airless.
Even these systems need equipment designed for use electrostatic principles are the same spray applications do not electrostatic.
The paint particles sprayed at this point, are provided with forward speed and targeted.
The particles must pass through a floating cloud of electrons (negatively charged) produced by a high voltage source as an independent generator power, cable and electrode in the gun, or operated by a turbine generator located inside the gun spray.
The basic principle of electrostatic spraying is that ‘and’ electronic charges repel one another and ‘unlike’, electric charges attract.
Thus, each particle of material is negatively charged, 30-140KV and 0-200mA, and will seek the nearest grounded object (positive) to complete the electrical circuit.
If the product is sufficiently grounded, particles that have lost that part, will now be attracted to it. This effect is called a “Faraday cage”.
Finishing quality Requires operator training
High efficiency Requires grounding of components
High rates of application Conductive inks are required and areas to the acid test
Transfer efficiency is 50-90%
FACTORS THAT DISTINGUISHED AND FEATURING THE VARIOUS SYSTEMS OF PAINTING
All spray equipment is distinguished and characterized by three main factors:
• Surface quality achieved: is the final aspect of the film produced by ink, which must be faultless and uniform thickness throughout length;
• Productivity: output per hour is obtained, ie the amount of m 2 / hour;
• Efficiency of transfer: is the amount of material that actually remains in the part being painted.
Below is a comparative table showing the percentage of efficiency of transfer of the spray system analysis. In some countries that adopt strict standards for the emission of volatile organic compounds, the limit allowed is 65%.
COMPARATIVE TABLE OF TRANSFERS
Note: The efficiency of transfer may vary according to the operator and condition of the equipment.
SELECTION CRITERIA FOR SELECTION OF PAINTING EQUIPMENT
PARAMETERS CONVENTIONAL AIRLESS AIRLESSASSISTIDO HVLP ELECTROSTATIC
QUALITY. FINISHING EXCELLENT BAD GOOD EXCELLENT EXCELLENT
SPEED. APPLICATION MEDIUM / FAST FAST FAST MIDDLE FAST
EFFICIENCY TRANSFER 25-45 (%) 55-70(%) 65-85(%) 50-85(%) 50-90(%)
OPERATION EASY DIFFICULT DIFFICULT MIDDLE DIFFICULT
COST MAINTENANCE MIDDLE HIGH HIGH MIDDLE HIGH
PAINTING MANUAL EXCELLENT BAD BAD EXCELLENT EXCELLENT
MAQ. RECIPROCATING GOOD GOOD GOOD EXCELLENT