Guide to Buying Spray Guns for Car Paintwork

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Guide to Buying Spray Guns for Car Paintwork

Ever since the advent of spray guns, the brushes and buckets used for painting until then have been obliterated. All laborious, time-consuming painting tasks are now accomplished in much less time. And there are other advantages as well. Spray painting is not as messy, the coat applied is more even, and less paint supplies are used as well, curbing wastage.

The credit for this invention was shared by two Americans, Joseph Binks and a doctor from Ohio, Dr. Allen DeVilbiss. Dr. Allen's son, Thomas DeVilbiss, improvised on his father's invention to create a handheld, air-powered spray gun that was first used in the furniture industry. Several years later, the spray gun also found application in automotive finishing jobs, and auto body repair workshops could choose from three types of spray guns.

The same three styles of automotive spray guns are widely available in brick-and-mortar stores and online stores. eBay offers all three types of spray guns, siphon-feed guns, gravity-feed, pressure feed spray guns, and more. As one considers purchasing spray guns for a job, it is worthwhile to take a  look at the working of the three styles of spray guns and the features incorporated in them to successfully carry out car painting jobs.

Basic Controls and Working of a Spray Gun

A spray gun is a pneumatic device with a trigger-like attachment using compressed air to atomise the fluid paint through its nozzle. Typically, the design for a conventional air atomising spray gun comprises of the gun system, pressurised paint cup, compressed air-system, and flexible tubing to connect these components. The three basic controls, namely the air micrometer to adjust air pressure, the fluid adjustment for quantity of fluid, and fan control to regulate the spray pattern, all work together to achieve optimum performance of the gadget. This ensures controlled atomisation and even dispersion of the fluid paint.

There are two passageways, one for the fluid and the second for air, both of which are closed. The air passage is blocked by the air valve, while the fluid flow is stopped by the fluid needle that fits securely into the orifice at the nozzle tip.When the spray gun trigger is pulled, the air valve opens and the fluid needle retracts to open the orifice. The fluid from the cup is drawn into the nozzle, and the air rushes past through the air passageway. Meanwhile, the fluid is making its way towards the orifice on the nozzle tip. At the nozzle tip, atomisation occurs, as the air mixes with the fluid to form a spray mist that is ejected out. Conventional spray guns may have the siphon-feed or the gravity-feed designs, determined by the placement of the material cup. Fluid supply options thus give rise to three types of spray guns.

Pressure-Feed Guns

These guns are almost obsolete, replaced with more efficient paint systems. Fluid pressure in this system is provided by an external source such as a pressure tank, through a hose. Pressure-feed guns find application in large industries, where vast amounts of fluids are moved through the paint systems. The air in the cup also may be pressurised, which in turn forces the fluid to rise through the dip tube in the cup. Air atomisation is achieved using a separate air hose.

Siphon-Feed Spray Guns

This paint system draws up the fluid from the cup located below the gun. Greater compressed air pressure is needed to create a strong enough vacuum at the nozzle tip that pulls the fluid paint through the feed tube. Additionally, an orifice on the cup lid also lets in atmospheric air that forces the fluid up the feed tube. This reduces the overall pressure and renders the siphon effect less efficient especially if fluid viscosity is more. Hence siphon-feed spray guns are ideal for low viscosity fluids such as lacquers, stains, and dyes.

 Gravity-Feed Spray Guns  

This contraption is similar to siphon-feed guns, except that the cup holding the paint is located above the gun. The fluid entering the gun is assisted by gravity for positive fluid pressure, optimising the compressed air pressure to create better atomisation and better utilisation of paint materials, thereby reducing wastage. This system is also ideal for fluids with greater viscosity. Gravity-feed spray guns using less air pressure also ensure less overspray, which is a major health hazard.

Specialised Guns Using Other Spray Painting Technologies

To convert fluid paint into millions of tiny, atomised droplets, spray guns may be based on other spray technologies as hydraulics, high volume low pressure or HVLP,  and low volume low pressure or LVLP.  HPLV spray guns are popular for car painting jobs, especially those with gravity-feed cups. Shoppers looking to buy spray guns are well advised to know the working of each type and the pros and cons as well, as this can help them make informed choices.

HPLV Spray Guns

HPLV spray guns are conventional spray guns but deliver greater quantities of fluids at reduced pressures. Hence, they have higher Transfer Efficiency TE, delivering 65 percent of  fluid to the surface. High volumes of air generated by HPLV turbines are delivered to the HPLV gun by way of hoses. The gun reduces the volume of air to between 4 psi and 10 psi at 42 cfm to 62 cfm. At that pressure, the flow of fluid is even and overspray is greatly minimised. To accommodate large volumes of fluids passing through the fan under low pressure, HPLV spray guns have larger passageways.

LVLP Spray Guns

Turbine-driven LVLP spray guns use lower volumes of air and operate at low pressures. Since the air requirements are less when using an LVLP spray gun, large air compressors are not necessary and small compressors can paint an entire car without ceasing.

Reduced Pressure or RP Spray Guns

A good alternative to HPLV spray guns, reduced pressure or RP spray guns are popular because these guns offer better finishes and have higher transfer efficiency than HPLV guns. Also, a smaller compressor can work fine as pressure levels needed for operation are lower than that needed for conventional spray guns.

Airless Spray Guns

A painting job done using airless spray guns is less turbulent, and hence paint loss is greatly reduced. The paint is pushed to the specialised atomising nozzle and through it, using great pressure created by multistage pumps. At the nozzle, the highly pressurised paint encounters a sudden drop in pressure, and atomisation results. Airless spray guns are ideal for painting large surfaces, and as the paint droplets formed are larger than in conventional spray guns, a single pass gives a heavier coat.

Pros and Cons of Popular Spray Guns

The chart below offers a quick comparison of various spray guns with different types of feed supply, using varying technologies. The pros and cons of each type are provided.

Spray Gun Type

Pros

Cons

Siphon-feed

Inexpensive, good for beginners

Requires greater air pressure for operations, residual paint is wasted, difficult to use in tight corners

Gravity-feed

Less air pressure, easy to paint in recesses and cavities, can be held upside down, uses up all paint in the cup, ideal for automotive spray paint jobs

Overspray, expensive paint tends to be wasted

HPLV Guns

Less overspray, ideal for finishing jobs, minimal wastage of paint, easy clean-up

Large compressor for prolonged jobs, cannot take viscous fluids

LVLP Guns

Uses small compressors, high transfer efficiency at 70 to 80 percent

Slower than HPLV guns

Airless Spray Guns

Less paint loss, 70 percent transfer efficiency

Ideal only where thick coats are needed, finish quality leaves much to be desired, nozzle may clog

Gravity-feed and HPLV spray guns are the more popular types of spray guns in the market. They hold many advantages, but are not ideal for jobs requiring high-quality finishes.

Buying Spray Guns on eBay

eBay is a great online source which allows the shopper to compare and select from a vast array of products. People looking to buy spray guns for automotive painting can find all major types that can accommodate different budgets. Spray guns can be expensive, but eBay has new and used spray guns on sale.

Online shoppers can have no problems browsing the various types of spray guns available on eBay, because the products are categorised well and products are available under numerous categories. This ensures that the shopper does not miss out on relevant listings. Information provided on listings include a brief description about each product, top-rated sellers, and the pricing and postage charges. With so much information available at a glance, shoppers can quickly narrow down their choices and then peruse each listing at leisure, until they finally make their choices.

No matter what one's choice of spray guns may be, it is a good idea to verify the background of the seller before entering into a transaction on eBay. The website makes this easy by making available the feedback and rating that each seller receives from customers.

Conclusion

Painting the car is a messy job, but spray guns have made it far less tedious. Several types of spray guns have been introduced in the marketplace, with subtle design changes and improved technology. The conventional spray system used a gun with can to hold the paint, and pressurised paint was pumped up towards the nozzle that finally sprayed atomised paint onto a surface. Paint cups were placed on top of the gun and paint aided by gravity was atomised, providing better performance. Siphon-feed guns, gravity-feed guns, and pressure-feed guns are now available and are based on different methods of fluid supply.

Spray paint technology also evolved. HPLV and LVLP paint systems, reduced pressure guns, and airless spray guns increased the transfer efficiency so that more painted was sprayed on the surface while overspray was reduced. Overspray was also a health hazard, and with new systems, these issues have been better addressed.

With a seemingly endless inventory and user-friendly search tools, eBay is a website that consumers have come to depend on to fulfil their car painting needs.

 

 
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