Troubleshooting: Where Do We Begin?
Posted on Wednesday, September 22, 2021
By Marty Korecky
We all have run into situations where something we’re doing doesn’t work the way we expected. Whether at home or at work, problems always arise at the most inopportune times. The car won’t start and we have to be in the office early for a meeting, the computer gives us the spinning wheel of death when the end- of-the-month report is due, or our finishing system is down because of a quality issue we can’t figure out and our customer needs the parts now.
In the finishing industry, we run into similar problems all the time. For example, the big order must ship ASAP, but we’ve run into a problem—contamination on the parts, parts won’t cure, powder feed issues, and the list goes on. In each of these situations we are faced with troubleshooting the problem so we can get life back to normal as quickly as possible. We would like to call in an “expert,” but we don’t have the time. It’s up to you. Do you have what it takes to find the root cause and provide the solution?
Troubleshooting is a systematic approach to problem solving. We are sometimes mystified at the speed at which the “experts” can do this; however, it’s because they have done this many times, probably have seen the same or similar problems, and know where to start looking. We can do the same thing and we can start to become proficient once we have the basic steps in place.
Fortunately, we have help. Many vendors of equipment, pretreatment, and powder, as well as industry trade associations, provide troubleshooting charts which help with the process. These guides typically list the problem along with several possible causes and solutions or remedies. Let’s look at an example problem and walk through the troubleshooting process.
Our example finishing system consists of:
- Conveyorized line.
- Load/unload area.
- 3- or 5-stage spray pretreatment system.
- Convection dry-off oven.
- Reclaim capable powder booth with a fluid bed hopper feeding either automatic or manual guns.
- Convection cure oven.
As we begin to inspect the parts as they come off the line, we notice craters in the coating. We reach for our troubleshooting chart and here is what we find.
This is a great start and often will lead us to the answer. In some cases, however, the cause may be more difficult to find. Let’s see if we can add to the information noted above.
All shops should have clean, unopened panels available for troubleshooting and/or offline testing. These can be purchased from several vendors in various sizes but for this exercise we can use standard CRS (cold rolled steel) 3 x 5 inch panels.
1. Run a few panels through the process just as you would the production parts. This does two things. It confirms the problem, or if the panels don’t exhibit the craters, indicates the substrate may be the cause. If the panels exhibit craters, then we move to the next step.
2. Spray a test panel or two right out of the package with virgin powder from an unopened container with a clean powder gun. Cure the panels in the cure oven and inspect. If the panels do not have craters, the virgin powder is not the cause. If the panels exhibit craters, there are a few possibilities.
- The virgin powder may be the cause.
Solution: Contact the powder supplier.
- The compressed air is contaminated with oil and/or moisture.
Solution: Test by spraying into a clean white cloth and look for wet stains.
- The cure oven is fouled or dirty.
Solution: Try curing another panel in the dry-off oven (if temperature is adequate).
3. If the powder is good:
- Did the powder in the booth get contaminated by:
- Improper cleaning between powders?
- Operators dragging something into the booth on their clothes?
- Use of a substance such as WD-40 somewhere near the powder line?
- Personal hygiene products worn by operators working in the booth? This has been known to happen in a few instances.
If all of the above checks out ok, move to the next step of the process.
4. Run a test panel through the pretreatment system and coat and cure the panel. If you have craters, the problem is most likely within the preteatment process.
- Look to see if the panels/parts are clean before coating.
- Look for a water break free surface on the panels/ parts after the cleaning and first rinse stage.
- Did your manufacturing department change to machining lubricants which are not compatible with the cleaner in the pretreatment washer?
- Is there an issue with the oil skimmer in the cleaning stage?- Verify the exhaust fans are running properly.
Solution: Contact your pretreatment supplier. If the panel is good, there may be other possibilities.
5. Cure oven
- When was the last time the cure oven was cleaned? If recently, maybe residue is floating in the oven.
- Make-up air. Is the oven pulling in fumes from other parts of the plant or outside, causing contamination?
Solution: Have maintenance check the oven and/or clean the oven.
6. When was the last time maintenance was done on the conveyor?
- Over-lubrication can cause oil to drip from overhead onto parts causing craters.
Solution: Check the chain for excessive oil. Adjust the chain oiler as needed.
7. Air knives are great for blowing off parts or for air curtains. If there is oil/ moisture in the air lines this can leave residue on parts, causing craters.
Solution: Check air dryer/chiller and all traps and drain as necessary.
While a typical troubleshooting chart is a good start, there is no replacement for a good understanding of your finishing process. There are many ways to become educated on finishing processes.
Most vendors are willing to provide in-house training for your employees. Trade associations provide great opportunities for training at classes they hold throughout the year. The Powder Coating Institute (PCI), www.powdercoating.org, conducts several Powder Coating 101 and Powder Coating 202 workshops, which cover powder, pretreatment, application and recovery equipment, as well as test equipment required for a quality finishing process. The Chemical Coaters Association International (CCAI), www.ccaiweb.com, conducts training within their regional chapters. Training is also available at national shows like FABTECH, www.fabtechexpo.com.
Even the most experienced technical service engineers run into situations where the answer isn’t obvious. And even when they follow their systematic troubleshooting processes, the answers they get don’t always add up. In most cases, like our example situation, co-vendors are called in to work together. While most powder suppliers understand pretreatment and equipment, they are not the experts and vice-versa. Working together allows the sharing of information not only between themselves, but with the customer experiencing the problem. Watching them and asking questions as they solve the mystery and get to the root cause is a great education.
Marty Korecky is business specialist – powder coatings for AkzoNobel Powder Coatings, Inc.