A customer had an application where they were using a plastic blasting media (PBM) to remove a coating from composite sheets. Being that I was unfamiliar with this type of blasting media, I went to the web for research. This process is very interesting as it can remove coatings, paint, powder coats, etc. without harming the substrate. It is widely used in the automotive and aerospace industries as it can be used on materials like very thin metals, composites, and even hardwood.
In our experience with non-conductive materials, static can be a huge problem. And in this case, it was. The PBM was “sticking” to everything including the composite material that was being cleaned. They were losing material as it was leaving the blasting chamber. As with any type of blasting system, you want to reuse the material to economically reduce waste and keep the operation running longer. As you can see in the picture below, the PBM is clinging to the internal components because of static. This static force was keeping the PBM attached to the composite sheet and allowing it to leave the chamber.
As a quick remedy, they tried to use compressed air to blow the PBM back into the cabinet. They were using copper tubes that were flattened to create a homemade nozzle. This style of nozzle is unsafe and very loud. It was also difficult to get the correct amount of blowing force because static can build at different rates. The higher amount of static charges, the stronger the attraction. They needed a better method as they found themselves wasting not only the blasting material, but also much compressed air.
With applications similar to this, we like to remove the static at the problem area. Then, we do not have to be concerned about the static forces. For their application, the cabinet had a 6” wide opening where the composite material would exit. So, I recommended two pieces of the model 111206, 6” Super Ion Air Knife Kits, to be mounted just outside the cabinet. One Super Ion Air Knife would be mounted above the sheet to clean the top surface, and the other mounted below the sheet to clean the bottom surface. I recommended that they position the Super Ion Air Knives at a 45 deg. angle to the surface of the composite sheet in the counter-flow direction.
This position will optimize the performance of the Super Ion Air Knife. It increases the contact time to coat the surface with ions to remove the static and to keep the PBM inside the cabinet. With the design of the EXAIR Super Ion Air Knife, it has a 40:1 amplification ratio. That means that for every 1 part of compressed air, it will entrain 40 parts of ambient air. So, it can operate with much less compressed air. Once they mounted the Super ion Air Knives, they were amazed at the performance. It was very quiet; it used very little compressed air; and it kept the composite sheets completely clean. After the static forces are removed, it only needed a light breeze to remove the PBM from the surface.
If you find that static is creating process problems, wasting time, and costing you money, EXAIR has a large line of Static Eliminators that can help you. For this customer, it was a simple phone call to EXAIR that got his operation back up and running fast and smooth without static.