Spray gun cleaning: an important process
Greg Davie looks at an important process in making sure the finished job is the best it can be: using a clean spray gun and how to easily and effectively clean it.
You spend the time to get the job prepped and looking perfect ready for spraying, you’ve prepare the booth, set up your equipment and materials, meticulously cleaned the surface you are about to spray and take your time in spraying to make sure the finish is flawless. Then you have to clean up. Errgghhhh.
I can’t say that cleaning a spray gun is anyone’s favourite job but as we all know, ensuring that you do it properly is critical to making the next job come out as well as the one you just finished.
But did you ever stop to make sure you are cleaning and maintaining your equipment in the most efficient method, and ensuring the asset you are holding in your hand, your spray gun, is going to have a maximum service life?
I’ll bet you are saying the same thing we hear people say all the time. “I’ve been spraying for 30 years, of course I know how to clean my spray gun.” And you know what, you’re probably one of the few people who are. But just in case here are a couple of Tips to make sure you can keep your spray gun in good working condition.
You don’t need to strip it bare to clean it
The only areas of a spray gun that need to be cleaned are those that come into contact with product. I know this sounds like an obvious thing to say but it is a common belief that it is necessary to strip every aspect of the gun. There are only a few elements that should be disassembled in the cleaning process. They are:
The air cap
The nozzle
The needle
Removing things like fluid joints and needle packing is simply asking for trouble and in time will result in unnecessary wear and tear on the tool.
Soaking the gun body is not a good idea
It is common for us to see that a spray gun body has been soaking in thinners. This over time is going to cause serious issues to some of the delicate parts of to the tool. Soaking in thinners causes the “O” rings in the fan and air control systems to swell and become inoperable.
Use the right tool for the job.
When removing the nozzle make sure you use the spanner provided with the gun, or use a correct fitting hole spanner or socket. Never use a shifting spanner, pliers or vice grips.
If you use the incorrect tool you will likely swage the nozzle. The fit of the nozzle against the air cap is precise and if you damage that fit by distorting the shape of the nozzle you will likely lose fan control. The only fix for this is to replace the nozzle.
Lubricate
If you have taken out the needle make sure you lubricate the needle with Teflon-based grease before retuning it to the gun. By ensuring the needle is well lubricated you will reduce the wear on the needle as it slides through the gun body.
So how exactly should you clean a spray gun? If you follow these simply steps you will ensure a long service life:
Drain all excess paint from the spray gun and pot.
Wipe out the pot with a solvent-covered cloth as this will help to speed up the cleaning process.
Place a small amount of solvent – pre-used thinners will be sufficient at this stage – in the pot. Spray the gun to flush out the fluid corridor of the spray gun.
Remove the air cap and nozzle and place them in a suitable solvent bath for a short soaking period.
Using a soft pipe-style brush, clean all fluid ports and gently wipe off any paint residue from the needle.
Remove the needle by undoing the fluid control. Pull the trigger of the gun and using either your fingers or pliers pull the needle from the back of the gun. Place the needle in the solvent bath.
Remove the air cap from the solvent bath and gently clean it with a soft nylon brush (the best type of brush to use are those supplied in a gun cleaning kit). Pay particular attention to the atomisation holes to ensure there is no residual product. Finish with a quick blow out with an air duster.
All product must be removed from the atomisation holes otherwise the fan pattern will be affected. If there is product remaining after you have used the air duster, return it to the solvent bath and repeat this step. Do not use a hard instrument such as a screwdriver to scrape the paint away as this will likely cause damage to the air cap.
Clean the nozzle in the same manner as the air cap and pay careful attention to the needle hole to ensure there is no build-up of product. If there is residual product left in the needle hole you will find the gun will leak form this area.
Before replacing the nozzle put a small amount of lubricant (Inox Teflon grease is ideal) around the nozzle tread and tapered seats. This will ensure a leak-proof seal and will help to prevent unnecessary wear.
Before replacing the needle, lubricate it with Teflon grease to help protect the packing seal and reduce the wear on the needle. Tighten the needle packer if necessary so that the needle fits snugly.
Replace the air cap and give the gun a final flush with clean solvent. It is not recommended that you leave solvent in a gun as the vapour will dry out seals.
Tech Tips is researched and written by Greg Davie of GnG Sales, suppliers of smash repair equipment and consumables under the brand names: Mako, Rupes, Star Sprayguns, Star New Century, Workquip, Autoglym and Tranmax.
Head Office: 3 Foundry Road, Seven Hills NSW 2147
Tel: (02) 9680 4464