Proper care for your spray guns

May 26, 2015
Taking the best care of your shop spray guns can mean superior finishes and lower costs for the paint department.

When it comes to your paint department, little things really do mean a lot. Dust, poorly measured formulas, dirty spray booth filters, technicians not wearing their suits and hoods and poor spraying technique can wreak havoc on your work —producing poor, flawed finishes whose follow-up repairs diminish efficiency and cut profits.

Consider then the potential problems caused when your most important painting tool, the spray gun, isn't functioning properly. Faulty guns produce these same poor finishes, often to a worse degree.

Yet, many shops overlook the proper care of this crucial tool, often until it meets an early demise and needs replaced. By then, the shop has two expensive issues to address — a string of jobs that need costly re-dos and investment in a new gun (which typically prices out at $600).

All this can be avoided by investing a few extra minutes daily and weekly spent cleaning and caring for spray guns according to manufacturer specifications. Use these general recommendations as a guide.

Stock the right items
The keys to proper cleaning start with having the proper tools and products on hand for the job. Despite being durable, spray guns are also fairly delicate. They can be easily damaged when being cleaned if repairers use unapproved products and tools.

Avoid this by stocking only those cleaning solutions permitted by the gun and paint manufacturer. The basic rules are: Guns used for waterborne products should be cleaned only with pH-neutral solutions. Avoid chlorinated hydrocarbon solvents, which can corrode aluminum and galvanized parts for solvent-based paints.

Consider investing in tools that reduce the possibility of damage. Repairers sometimes resort to using wire brushes, key files or paper clips for cleaning simply because they're available in a shop. These items can wreck the delicate passages in a gun and permanently ruin the spray pattern. Clear these items out of the paint department and instead stock spray gun cleaning tool sets. These sets typically include cleaning brushes in various sizes (large, medium and double-sided), nozzle cleaning needles and a high-performance lubricant.

Consider as well investing in a sealed, automatic spray gun cleaner. These units provide safer, quicker, more thorough cleanings than those performed manually and use less cleaning solution. Because they're sealed, they cut the release of VOCs.

(Photo courtesy of Sherwin-Williams) - A poorly maintained spray gun costs a shop twice--in poor finishes that must be redone and in reduced service life. (Photo courtesy of Anest-Iawata) - A spray gun cleaning kit contains all the tools necessary for a proper cleaning and prevents employees from using unauthorized tools that can damage a gun.

Manual cleaning
If your shop manually cleans its guns, use the following steps after putting on goggles and Nitrile gloves:

1. Dismantle the gun by first removing the paint needle, followed by the cap, and then unscrew the fluid tip. Note: If these parts don't remove easily, never resort to using excess force such as striking the gun with a hammer or other tool. Apply a lubricant and gradually work the parts loose.

Many times you can go online to your gun manufacturer's website and download a build and component sheet and even other troubeshooting tips.

2. Clean the material passage with the recommended solution and then the gun body.

Use the recommended brushes to remove paint residues stuck to the drill holes. Utilize the needles included in the cleaning kit for cleaning out the smaller drill holes. Never push paint residue back into the openings.

Make sure that no cleaning fluid or dirt particles end up in the air passages (air intake or the paint nozzle drill holes) of the gun body. Some manufacturers recommend leaving the spray gun connected to the airline with the air rate reduced to the minimum flow.

Finish by drying with a blowgun. 

3. Use the brushes to clean the nozzle set. Be careful that none of the metal on the brushes touches the nozzle.

If the nozzle is damaged or needs replaced, always perform a complete re-installation of the nozzle set, which includes the air cap, paint nozzle and paint pin. Strictly follow the installation regulations of the gun or nozzle manufacturer.

4. Reassemble the gun. Brush a thin coat of silicon and acid free, non-resining special grease or oil on the needle spring, paint pin and all sliding parts and bearings. Re-install the parts in the reverse order.  

Note: Some shops soak their guns in buckets or vats of thinner to help clean them. This practice actually can cause blockages. If the thinner has been used or is dirty, residual dirt and paint can soak into and clog drill holes and passages in a gun. Even if the thinner is clean, paint and contaminants that are loosened or remove can move onto and clog a different passage.

Additionally, some of the packing in the gun can become damaged by absorbing the thinner due to prolonged soaking, which will cause improper operation of the gun.

Cleaning machines
Spray gun cleaning machines are relatively simply to use. The instructions for each manufacturer differs, but most utilize a system that pushes cleaning solution at high pressure through the gun. Care needs to be taken when inserting the gun into these systems. If the gun is not set up correctly, the system actually can create serious blockages.

Note that some manufacturers recommend that the gun body be cleaned first to ensure the most thorough cleaning possible.

(Photo courtesy of Becca Inc.) - Gun cleaning machines provide quicker and more thorough cleaning of spray guns than manual cleaning, along with reducing the release of VOCs. (Photo courtesy of Becca Inc.) -  Make sure guns are loaded into the machine correctly. Bad connections, in some cases, can create serious blockages.

Set a maintenance schedule
Properly maintaining a spray gun involves more than just keeping it cleaned. Guns also need to be lubricated regularly and examined for wear and damage. While this may seem like a lot of extra work, it actually can be completed fairly quickly and provides significant benefits that (1) ensure the gun is working properly all the time and (2) remains in service during its expected life span.

Note the following maintenance schedule recommended by DeVilbiss.

Every shift duties
1) Check the front air cap face and all air cap holes for damage. Replace if necessary

2) Check the fluid tip external profile for damaged. Replace if necessary

4) Make sure the fluid needle is seated correctly in the fluid head, allowing no seepage. If necessary, replace or lap in.

5) Turn off the pressure tank fluid cock and/or compressed air supply to the gun. Trigger the gun. Apply one drop of spray gun lubricant to the needle shaft immediately behind the fluid needle packing screw. Release the trigger. Repeatedly pull and release the trigger to work lubricant into fluid needle packing.

6) Make sure the trigger operates smoothly and the fluid needle does not stick or bind up during movement due to damage or paint build up.

7) Apply a single drop of lubricant to each side of the trigger pivot screw. Repeatedly pull and release trigger to work lubricant into trigger pivot.

8) Apply a single drop of lubricant to the air valve stem. Repeatedly pull and release the trigger to work lubricant into air valve packing seal.

9) Make sure the air valve operates smoothly and without sticking. Replace the valve stem if necessary.

10) Check the needle packing for fluid leakage. If required, tighten the needle packing by rotating the packing screw until the needle starts to bind, then loosen the packing nut just enough so that the needle moves freely. If the screw bottoms without eliminating the fluid leak, replace packing with a new item.

Additional end of week maintenance checks
1) Check to see if the air cap retaining ring and gun air baffle threads are free from damage (a smear of petroleum jelly on the threads will help prevent binding).

2) Check to ensure the air baffle seal is not leaking air badly or is visibly damaged. If necessary, replace.

3) Apply petroleum jelly to the needle shaft front end for smooth operation.

4) Apply petroleum jelly to the needle shaft rear end and needle spring to aid resistance to corrosion and contamination.

5) Check to see if the horn control valve can freely rotate with no stiff spots. If necessary, lubricate or replace the O ring.

6) If the Check Air control valve is fitted, make sure it rotates freely with no stiff spots. If necessary, replace or lubricate the O ring.

7) Check for air leaks from the air cap when the gun is not triggered. If necessary, clean or replace the air valve stem or seat.

8) Determine if the trigger retaining screw is tight.

9) Make sure the fluid and air inlet connectors are tight and sealed. Tighten if necessary.

Additional bi-weekly maintenance checks
1) Check for air leakage from the air valve body when trigger is pulled. Replace the air valve seal if necessary.

2) Check to ensure the fluid needle shaft is not badly worn and needle end profile and point are undamaged.

3) Apply a smear of petroleum jelly to all air O rings to aid fitting and easy rotation.

4) Check the gun body for damage, particularly around the air inlet connector port.

5) If the stainless steel head fluid insert is fitted, check for damage to the fluid tip seat, swaging or leaks caused by rotation. This item is not removable or replaceable. A new gun body will be necessary.

6) Check for damage to the air baffle chimney. Replace the air baffle assembly if necessary.

7. Apply Vaseline to the air valve spring to aid resistance to corrosion and contamination.

To ensure your shop adheres to these schedules, create a checklist that employees can sign and date. That's one more simple step to a spray gun cleaning and care regimen that will pay off handsomely in a better product and reduced expenses.

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