Gun current is one of the most critical parameters affecting the quality and efficiency of the finishing process. Excessive gun current can result in lower transfer efficiency, reduced finish quality and back-ionization. Back-ionization limits attainable film thickness, inhibits recoating, and has a detrimental effect on the coatings ability to penetrate “Faraday cage” areas.

For liquid painting operations using the RA-20R rotary atomizer or Kinetix guns, Nordson offers Automatic Feedback Current control.

Automatic Feedback Current control allows users to set the gun current at a level that will provide optimal (not necessarily maximum) charge and field strength for each application. Control of the gun current ensures that the number of ions generated in the charge zone is sufficient to charge the coating effectively, but not high enough to create excessive free-ion current on the already-deposited coating layer.

When coating parts with varying contours and shapes it is difficult to maintain constant gun-to-part distances. With a conventional voltage-control spray system, gun current will increase as the gun-to-part distance decreases. Conversely, gun current decreases as the gun is moved farther from the part. AFC control minimizes this problem, by allowing the operator to set the optimal gun current for his application. The AFC system automatically maintains the current at no higher than the preset level, regardless of the gun-to-part distance.
 
AFC control results in maximum transfer efficiency, high finish quality and enhanced Faraday-cage penetration. It also enables finishers to apply thicker layers of coating, when desired, and improve the efficiency of the recoating process.