Auto or Manual?



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Q. We are trying to decide between automatic and manual powder application equipment. We will be running our new line at 6 fpm. Our product opening will be 36 inches wide × 54 inches high. We have a variety of parts that are of welded construction, some that are fairly simple and many that have more complex shapes. Most of our products cannot be coated with automatic -only spray. The automatic guns are pretty expensive, and we do not know how to calculate the value. Any suggestions? R.D.


A. First, look at what each kind of application equipment is best equipped for. Manual applicators have sight and flexible axis of motion. Operators can adjust the gun settings for different applications in a short period of time. They can view the part to cover only what is bare and avoid leaving any light spots.

If the operator is well trained and maintains proper flow rates, the manual gun can provide exceptional transfer efficiency.

Also, manual guns can be cleaned for a new color in a very short period of time.

Automatic application equipment is useful when operators may have trouble keeping up with the amount of surface that has to be covered. Automatic guns provide more precise and repeatable coverage over larger surfaces. Automatic guns take longer to clean unless they are fitted with equipment to blow-down the gun parts automatically.

The first question you need to address is: “Can two manual operators keep up with the amount of surface that has to be covered per minute?” Two sprayers can cover about 45 ft2/min. If your product window were fully loaded at 6 fpm, they would just barely be able to keep up. The line will not be wall-to-wall parts, so it appears that two people can keep up with this line speed. Indeed, there are many manual-only lines operating at 6 fpm. However, the complexity of the parts may have a profound influence on how well they keep up. Also keep in mind that you can go to four manual stations in one booth. It does not appear that you would need that, but it is a viable option for flexible coverage and fast color change.

The value of the automatic guns lies in three primary areas: 


1) If the operators cannot keep up and stop the line, the guns are justified.

2) If the reject rate is higher because of light coats, the guns are justified.

3) If absenteeism and worker fatigue are adversely impacted, the guns are justified.



At 6 fpm, you should consider having a booth that can be fitted with automated guns even if you cannot afford them or don’t need them at this time. If problems arise and the auto guns are needed, they can be added.

Keep in mind that it is often harder to get approval for an additional capital purchase later on. Finally, there is no downside to owning the automatic guns and using them as needed. If you can afford the capital now, that would probably be the best way to go. Also keep in mind that many companies look to speed the line up at some point.

If it were my line I would seriously consider buying the guns now and having a flexible line that can do many things without stressing the applicators.