Parameters in rotary screen printing – type of screen plate

To achieve a good print result, particular attention needs to be paid to the most important parameters in rotary screen printing. The key influencing factors are the type of screen plate, the ink, the squeegee and the flow path. This article focuses on the type of screen plate, the parameter with the most decisive influence on the print result. Press operators can control this parameter by selecting the appropriate screen.

A uniform fabric structure is key

The screen printing plate regulates the volume of the ink layer that is transferred to the substrate. The Gallus Screeny screen printing fabric is made of steel and is produced at special mills. The same terminology is used for woven stainless steel fabric as for woven textiles, so it is made up of warp and weft threads (see sketch).

The more uniformly the fabric is woven, the more precisely the required volume of ink is transferred to the substrate. It is therefore important for warp and weft threads to be woven so as to always form a square mesh. This homogeneous structure is vitally important if large ink pigment particles are to be pressed through the screen fabric, for instance.


 “A” and “B” are the same length.

Galvanising to stabilise the fabric

The steel fabric itself is very fragile. If it is to be used for rotary screen printing, it needs to be strengthened using the galvanising process. This involves covering it completely with a homogeneous layer of nickel. Experience has shown that this nickel layer needs to cover the steel fabric smoothly and evenly for the galvanised fabric to benefit from a good level of stability and an optimum ink flow.

The close-up shows the fabric has a smooth, even nickel surface.

Closed photopolymer layer

Following nickel plating, a full-area photopolymer layer is applied to the steel fabric in the cleanroom. It is important to ensure that there are no gaps in this layer and that its thickness remains the same over the entire screen fabric (EOM = emulsion over mesh). If these basic requirements are not met, it is not possible to define and specifically control ink transfer.

An evenly applied, closed photopolymer layer is an essential quality factor for a rotary screen printing plate.

Galvanised stainless steel fabric + photopolymer layer = ink control

The combination of perfectly woven and galvanised stainless steel fabric and closed, homogeneous photopolymer layer creates the basis for targeted ink control in screen printing. Once the photopolymer layer has been exposed and washed out, the required volume of ink is pressed through the openings in the galvanised stainless steel fabric.

The green polymer layer controls the targeted ink flow of the yellow ink droplets.

Key selection criteria for the right screen printing plate

But which criteria should label printers use to select the right screen printing plate for the relevant application? Three elements play a key role in this respect – the thickness of the ink layer, the resolution and the size of ink pigment particles. With regard to the thickness of the ink layer, Gallus offers a range of Gallus Screeny screen printing plates with an ink build-up of 5 to 280. The ink pigment resolution is extremely important, because rotary screen printing is still primarily used for solid and line motifs. It can be varied between 100 and 400 with Gallus Screeny screen printing plates. Last but not least, the particle size of the ink pigment to be pressed through the screen mesh ranges from 24 to 265 with Gallus Screeny screen printing plates.

Printing error: Inhomogeneous photopolymer layer

An inhomogeneous photopolymer layer leads to pinholes in the print image. During exposure and subsequent washing out of the screen, parts of the photopolymer layer are rinsed out. This means that the screen printing plate has to be reworked manually with a photopolymer filler before being fitted onto the press. A screen printing plate produced industrially should always have a smooth, homogeneous and closed photopolymer layer.

Gallus Screeny application consulting

Due to its position as a pioneer in rotary screen printing and its many years of experience in this field, Gallus is the ideal contact if you have any questions about your rotary screen printing plate. Gallus Screeny currently offers the most comprehensive range of screen printing plates for rotary screen printing on narrow-web label presses. The Gallus Screeny team will advise you on the ideal type of screen printing plate for your particular application. Please feel free to get in touch – we’ll be happy to help.