Aside from a few stationary tools like the spray booth, air compressor, and maybe a wide belt sander, most of the finisher’s arsenal of tools are hand-held. Hand sanders, spray guns, air hoses, regulators, and filters are just some of the tools used in the application process. Then there are the material handling tools like dollies, drying racks, saw horses and carts. Half of the processes and most of the time in the finish room is spent moving material. It only makes sense to have the racks and carts to do it efficiently. It also makes sense to place the carts so you save footsteps.
Do You Have the Tools Necessary to do the Job Efficiently?
Don’t take anything for granted. I was at a very large company and as I walked by the stain booth I noticed the finisher was holding his gun back about 3 feet from the piece he was spraying. The gun was producing a huge rush of air and a large cloud of overspray. I couldn’t help myself, so I asked him what he was doing. He replied that he was spraying dye stain. I asked him what he had his air pressure set at. He said about 75 psi – about 3 times the required air volume. Now I was intrigued, so I asked him why so high. He said that he didn’t have a blowgun to dust off the piece before he sprayed it so he just turns the pressure to the gun up real high so he can use it to blow off the piece. Then, he says, if he holds the gun way back here he can control it enough to be able to spray on the stain.
Sometimes the simple addition of another regulator, spray gun, sander, or even a couple of extra hoses can afford a large increase in productivity. In this situation, a $12 blowgun was costing this company hundreds of dollars a month in stain, not to mention the cost of the compressed air and booth filters.
Whatever is invested in your tools will be paid back many times over by increased quality and productivity.
Are Your Tools Set-Up Properly?
Once again, don’t take anything for granted. Just because a tool is brand new, or appears to be working alright don’t assume that it is operating at its best. This axiom is particularly true with spray equipment. Often guns have improperly sized needles and fluid tips for the material that they are spraying. The finisher will quite often over-reduce the material or modify their spraying technique to compensate for this situation – People Principal #2. This result is higher VOCs, less film build, and increased labor. Your equipment supplier should have the information and parts necessary to remedy this problem.
Compressed air systems are also prone to performance problems. Parts get replaced; piping gets added to or moved. This can often lead to moisture in the lines or restricted airflow. Either of these problems will impact the performance of your spray or sanding equipment. Sometimes the culprit can be something as simple as an air hose that is too small in diameter or the installation of a reducer in the main piping system.
The compressed air system is at the head of the finishing toolchain, so any problems it introduces will affect everything that comes after it in the chain.
The quality of your finish and the consistency of your color begin with sanding. It is one of the most important steps in your finishing process. This being said I find it ludicrous that this is the job that most shops give the “new guy”.
You have to approach sanding from the perspective of the finish and not your finger. Of course, you sand to level joints and smooth the surface; however, you are also providing a uniform texture that will help take stains evenly and provide a tooth for the finish to grab on to. The correct grit selections and type of paper are crucial. Many of the high solids finishes require less white wood sanding than their older counterparts. Over-sanding is not only counter-productive but will ultimately encourage adhesion problems.
Take time to investigate different sanding schedules and sandpaper types. Work with your abrasives supplier. Run tests and compare results. You may find some ways to cut time and improve quality.
There is another way of reducing sanding time that is not directly related to your abrasives. Some people spray out finishes, especially primers using a poor quality gun and without the proper reduction, usually resulting in orange peel. Their feeling is that you just have to sand it anyway so what is the big deal? Well, for every hour you spend waving a spray gun over the wood you will spend 3-5 hours sanding what you just sprayed. It only makes sense that the smoother a sealer or primer goes on the less time you will spend sanding it out.
A word about swirl marks. If you have them, then there is a problem with your sander, your system, or the person using it. An adequately powered, properly maintained sander, using the correct progression of grits will not swirl. Notice the keywords: adequately powered, properly maintained, and correct progression of grits.
There are 3 basic types of spray guns used in professional finishing operations; Conventional, HVLP, and Air Assisted Airless. Their names refer to how the finishing material is atomized. The terms siphon feed, gravity feed and pressure feed refer to how the material is presented to the spray gun.
The spray gun system that you use can affect your bottom line in a couple of different ways.
- It will affect the amount of reducer that you need to add. Systems that feed the material to the gun under pressure tend to require less reducer than a siphon system which is trying to suck the material up through a tube.
- It will determine not only how often you have to stop and refill your material supply, but it also has an effect on operator fatigue. Not only do you have to stop more often to refill that quart cup, but that quart cup of primer adds about 2 ½ pounds of weight to the gun. At the end of the day, it feels like 2 ½ tons.
- Will have an effect on the amount of time and materials required for clean-up. Obviously, it is going to require less solvent to clean up that quart cup than it is to blow through 20 feet of material hose
The method of atomization affects the amount of material wasted in overspray. This is called transfer efficiency.
Transfer efficiency is a term that refers to how much of the material that comes out of your spray gun sticks to the wood versus how much bounces off and turns into overspray. The velocity that the material exits the gun has a lot to do with its Transfer Efficiency.
- Conventional – 40%
- Air Assisted Airless-80%
Thinking of it in a different way; for every $100 worth of finish
- Conventional puts $60 up the stack
- HVLP puts $35 up the stack
- Air Assisted Airless puts $20 up the stack
The switch from a conventional gun to an HVLP should be a no-brainer. The material savings alone will pay for the new gun. When deciding on your feed system, or if you are thinking about moving up to an air-assisted airless, you should consider the volume of finish that you shoot in a day, as well as the number of material change-overs that you perform. While Air Assisted Airless systems are pricey, they do offer significant savings in material because of the high transfer efficiency. Plus, they consume about 1/5th the compressed air of a pressure pot. Since they generate less overspray than the other systems, there is usually a reduction in sanding times on items like drawer boxes and cabinet interiors. Plus your finishers, your booth, and its filters stay cleaner longer.
Maintenance – nothing lasts forever
It can be hard to justify maintenance time since on the surface it appears to be non-productive time. The exact opposite is true. When and how well you maintain your equipment can have a huge impact on your productivity and the quality of your finish. It can also directly impact the morale of the people using the equipment. The “if they don’t care then I don’t care” attitude can have devastating effects on your products, so make maintenance routine. Invest in rebuild kits for your spray guns and replacement pads for your sanders. Murphy’s Law says that you are going to need them right in the middle of a rush job. That is not the time to try and hunt them down and go get them.