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AFS faqs

Questions and answers

AFS provides fast and unburocratic support. Worldwide, and near wherever you are.
 
In the following section, we answer some of the more commonly-asked questions. Should you have any questions which are not answered here, please email us at: Support@afs.biz or contact your local sales representative.

  1. What is reverse (back)-side treatment, and how can it be avoided?
  2. The treatment level from a 2-sided treater using a single generator is higher on one side than the other.
  3. The message: DESIRED POWER CAN NOT BE REACHED, together with a blinking fault lamp is displayed.
  4. The required dyne level can not be obtained

1. What is reverse (back)-side treatment, and how can it be avoided?

When a single side of web material is corona treated, there should be no measurable treatment effect on the side of the material which comes in contact with the roller.

Reverse-side treatment occurs if air is trapped between the web material and the roller, or wherever there is no contact between the two surfaces. If this occurs, a small amount of corona sprays underneath the web material. Unlike the main treated surface, reverse-side treatment appears as a random pattern. The nature of the pattern usually gives us a clue about the cause.

The treatment roller surface should be matt, clean and smooth. The web tension should be high enough to ensure a high degree of contact between the roller surface and the web material. The use of a pressure roller on the web inlet side is highly recommended, especially if high web speeds are usual.

The electrical characteristics of silicone-rubber deteriorate with time. When this happens, the rubber material can absorb electrical energy, causing it to become hotter and thermally stress the web material.

2. The treatment level from a 2-sided treater using a single generator is higher on one side than the other.

In order to obtain the same treatment level on both sides of the web, both sides of the treatment station must be set up identically.

If segments are used, the same number of segments must be used on each side.

The gap between the tips of the electrodes and the treatment roller should be the same on both sides. For a silicone-rubber coated roller, the gap should be set to exactly 2mm.

The operating hours of the silicone-rubber sleeves or coatings should be the same for both sides.

Check the quality of the corona discharge at low powers. If one side appears stronger than the other, this is a clear indication that the two halves are not exactly balanced.

3. The message: DESIRED POWER CAN NOT BE REACHED, together with a blinking fault lamp is displayed.

This can have 3 main causes, number 1 being the least likely and number 3 being the most common:

1. The generator has a fault, preventing it from being able to produce full power.

2. The mains supply voltage is lower than the specified value.

3. The treatment station is not able to draw enough power from the generator.

Firstly check that the mains supply voltage is within the specified range.

In order to check the system, run the corona treatment, with the generator set to run at full power. Check the DC link voltage. This is easily accessed at the push of a button and is displayed from the generator front panel. As the access method can vary slightly between different models, please refer to the generator manual, to establish how to do this.

If the DC link voltage is higher than approx. 490V, this indicates that the generator is operating correctly, but the treatment station is not able to draw enough power from the generator. If the voltage is much lower, this indicates that the generator is defective; assuming that the mains supply voltage is within tolerance.

There are several typical causes for the treatment station not being able to draw sufficient power from the generator.

If segment electrodes are in use, full power is only certain when the majority of the segments are switched into use. The gap between the electrode tips and the roller surface should be 2mm in the case of a rubber-coated roller, and 1.5mm, in the case of a ceramic-coated roller or electrode bar.

If the treatment roller has been re-coated or re-sleeved, the coating or sleeve thickness must be identical with the originally supplied parts.

4. The required dyne level can not be obtained

When a corona treatment system is initially designed for a particular application, all factors regarding the required treatment level are taken into consideration, including the web material type, the amount and types of additives, the web width and thickness, the line speed, climatic conditions, and whether the material is being initially or boost-treated.

From this information, it is possible to reliably ascertain the optimum corona dose for the application, and this determines generator power and establishes the correct type of treatment station necessary in order to obtain the required treatment level.

As a starting point, the treatment station should be in technically perfect condition. If the treatment roller is silicone-rubber coated, this must be in a near new condition, where there is any doubt with regard to the treatment level.

For the majority of polymer materials, it is essential to treat the material directly on the extruder. The treatment level always drops with time. Unless the material is going to be processed within a short period after extrusion, it is usually necessary to apply a second dose of corona treatment directly at the converting stage.

The majority of polymer materials will not allow themselves to be corona treated at all at the conversion stage, if they were not initially treated on the extruder.

If the treatment level measured at the factory does not reach the expected level, it is almost always because the treatability of the web material is different to the originally specified material.

The most common culprit is the type or amount of additives in the material; especially slip agents, FSU-105, or titanium dioxide. All additives worsen the treatability and long-term stability of the treatment effect.