Important notice to our current and future customers:
G. Bopp + Co. AG (“Bopp”) and even their existing customers have recently noticed that online offerings of products which look similar to those of Bopp and declaring them as “Bopp” products are increasingly being introduced on online purchasing platforms. There is no doubt that these offerings infringe Bopp’s trademarks, violate unfair competition (and other) laws and seriously deceive the market participants.
Bopp have reacted and undertaken respective measures to defend and protect their rights. Considering the enormous number of violators, it seems inevitable that this process will take longer than Bopp desire.
In the meantime, Bopp would like to emphasize the following:
Products manufactured by G. Bopp + Co. AG in Zurich, Switzerland are exclusively available from its subsidiaries in Switzerland, Germany, England, Italy, Sweden, USA, Korea and China.
G. Bopp + Co. AG are one of the world’s leading producers of precision woven wire meshes providing their high-quality products to market leaders in the high tech, pharmaceutical, chemical, aeronautics, plastic, glass, ceramics, mechanical engineering, paper, environmental technology and even space travel (www.bopp.com).
Screen Printing Technology
Choosing the right screen printing frame
Metal frames must always be used with BOPP SD stainless steel meshes.
Stainless steel meshes are always tensioned to higher values than synthetic meshes.
The screen printing frame must be able to take up these higher tensions and maintain these levels over many printing cycles.
We recommend the use of cast or hollow aluminium profiles.
Frame size - a vital factor for durability
Frames that are too small lead to excessive stress on the mesh
Fatigue leads to reduced print quality
Shorter service life means higher costs
Correct tensioning extends service life
In order to optimise the benefits of today’s modern meshes, a correspondingly productive tensioning machine is required.
When tensioning, the following rules have proved useful:
1. Bring the mesh up to the required tension in stages. Alternate tensioning in warp and weft directions, always beginning with the warp.
2. During the tensioning process, monitor the tension values using a reliable tension meter.
3. Leave to stand for 15–30 minutes, test again and tension accordingly.
Aligning the mesh
From a mechanical point of view, tensioning at a 45° angle is recommended for reasons of stability. For typographical reasons, this angle is not always ideal. We recommend:
Where possible, tension meshes diagonally (22° to 45°).
If diagonal tensioning is not possible, align the weft direction of the mesh with the squeegee.
Producing the stencil
Recommended tensioning for BOPP SD
stainless steel meshes is dependent upon the demands upon print quality. Certain BOPP SD and BOPP SD PLUS
meshes can be tensioned to way above 35 N/cm. In these instances, the stability of the screen printing frames in use must always be verified. Generally speaking, for these specifications a tension value of 30-35 N/cm is sufficient for an acceptable end result.
Due to their higher tensile yield point, stainless steel meshes can be tensioned to higher values.
Higher tensions enable a smaller off contact distance.
The smaller the off contact distance, the better the registration accuracy.
With careful degreasing, the surface of stainless steel meshes offers an exceptional bond for a wide range of films and emulsions; no napping is required.
SD stainless steel meshes offer minimal undercutting and can therefore be exposed without problems.
Printing (off contact distance and squeegee pressure)
The required off contact distance is dependent upon many different factors such as mesh tension, colour viscosity, squeegee speed and even the print image itself. For this reason, we cannot give general recommendations for off contact distance and squeegee pressure. However, the following is worth noting:
Always begin with the smallest possible off contact distance.
If the ink is not released cleanly from the stencil, increase the off contact distance in small stages.
Always work with the minimum squeegee pressure.
Printing with off contact distance
When printing with off contact distance the mesh will deform, which impacts negatively on registration accuracy. The smaller the off contact distance, the less the deformation and therefore the better the registration accuracy.
The higher the mesh tension, the lower the ink viscosity and the slower the squeegee speed, therefore a smaller off contact distance is better.
Doubling the off contact distance results in a fourfold distortion of the image.