FAQ For The Powder Coating Process

Why You Need An Electrostatic Gun?

Powder being non-conductive cannot be charged internally. It can only be charged externally, i.e., electrostatic charge. The electrostatic charge can be imparted with high voltage discharge, called Corona Charging, or by frictional contact with the inside of the gun barrel, called Tribo Charging. In a corona charging system, 100 KV is generated in the gun and released at the gun tip. The free ions created in the field rush towards the nearest ground (the object to be coated). The powder is sprayed through the gun using compressed air. As the powder passes through the electrostatic field created by the release of 100 KV at the gun tip, it picks up a charge and gets deposited on the grounded substrate. The part is then placed into an oven for curing of the powder. In the curing oven, the powder melts and cross-links to form a hard film to complete the process.

What Is Tribo Charging?

In Tribo charging the powder gets charged by friction. Powder moving through the gun will rub against the media in the gun, and it will get charged.

Which Is Better: Corona or Tribo?

Corona guns are the most versatile guns as they can charge any chemistry of powder. Tribo guns can only charge powders specifically manufactured for the Tribo charging only. Beside that Tribo guns are very sensitive and also charging dependent on other factors like atmospheric moisture, powder particle size. As the quantity of powder that can be charged from Tribo guns is less, as compared to Corona gun, more Tribo guns are required to coat the same amount of the surface area.

Does Mitsuba Manufacture Tribo Guns? Do I Need A Separate Control Panel To Use The Tribo Guns?

Mitsuba does manufacture Tribo guns. All Mitsuba panels are designed to use Tribo as well as corona guns on the same panels. We can also offer a dedicated Tribo system.

Why Do You Need A Powder Hopper?

Fluidization is the mixing of compressed air with the powder in the feed hopper. This helps to break up the powder particles, remove moisture from the powder, and provide a lightweight consistency to powder that is easy to transport. When the powder is properly fluidized, the powder rises in the hopper, and the surface appears to be moving like water at a low boiling temperature. The feed hopper has a porous tile that separates the small air plenum at the bottom from the main body of the container. The compressed air is introduced into this plenum and circulates up through the powder in the container, suspending the powder particles in a state that resembles a liquid.

What Is Faradays Cage Effect In Powder Coating And How Does One Overcome The Same?

A phenomenon was first observed by the great scientist Michael Faraday (September 22, 1791 – August 25, 1867). The Faradays cage is the area of the object where the external electrical field does not penetrate. It is difficult to deposit the powder in very complicated objects.

To overcome the Faradays Cage areas, the following conditions must be fulfilled: powder has to be well charged, airflow must be sufficient to deliver the powder inside a recess but not excessive to preclude powder deposition, and the free ions must be minimized. Because most Faradays Cage areas involve some type of “pocket” areas, it is important that the method for directing the powder flow in these areas allows for displacement of the air to allow penetration. Mitsuba nozzles are specially designed to overcome the Faraday’s cage area. And also the special Corona Classic Attachment is available to minimize the free ions from the field which greatly reduces the Faradays Cage Effect.

Why Do You Need To Sieve The Powder?

Sieving separates dust from powder. The powder which could have compacted during recovery or transport is once again distributed into distinct fine particles.

How Do I Select The Correct Type Of Booth And Recovery?

The selection of booth and type of recovery is determined by the size of the object to be coated, the speed of the conveyor, number of colors to be changed, etc. The comparison of various recoveries will help you to select the most suitable recovery for the requirement.

How Does The Quality Of Grounding Affect The Quality Of Powder Coating?

The 100 KV discharge at the gun tip creates a corona effect between the gun tip and the object (to be coated). The positive ions are drawn back towards the gun tip. The negative ions search the closest grounded object and are attracted to it immediately. The powder collects the charge on the way to the object and sticks to it. If the grounding is not up to the mark, all the ions will not be attracted to the object, and a smaller quantity of powder will be deposited on the object to be coated.

Besides this, if the grounding is not of good quality, it can cause shocks to the operator as well as create sparks. The sparks are very likely to cause a fire. It is necessary to have efficient grounding. The Efficiency Meter helps you check grounding as well as Gun tip voltage.