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coatSEAL end seals for flexo printing

End seals for chamber doctor blade systems


Seemingly a small cog in the big flexo printing machine wheel - yet the end seals play a vital part in the proper functioning of the chamber doctor blade system. The right end seal solution promotes accurate doctoring results and leak tightness. The benefit therefore is: less cleaning, less machine down time, less ink waste, i.e. true cost and time savings.

Identifying the most suitable sealing concept

So how do you get to the optimal sealing solution? The magic word is custom-designed. The world of flexo printing is manifold: The application environment of narrow web label printing compared to wide web flexible packaging production or coating and converting applications differs considerably and so do the demands on end seals.

First, the parameters of the application are analyzed: Machine brand and model, ink type, printing speed, chamber geometry, substrate, final print product, load factor of the press, all these are important factors for the sealing concept and sealing material choice.

coatSEAL sealing concepts

coatSEAL Flexi-LF - ultimate lifespan

coatSEAL Flexi-LF is an extra-long-lasting end seal especially for high-speed printing, even beyond 400m/min.

The top radius of the seal, on which the anilox roller rotates, has a special low-friction insert that increases the anti-frictional properties of the seal. On the one hand, this reduces the mechanical load on the seal and, on the other, keeps frictional heat within limits, thus reducing the risk of ink residue being deposited, which could lead to leaks.

The body of the seal is made of a dimensionally stable and ink-repellent technical foam, which at the same time has the necessary flexibility to fit perfectly into the chamber contour.

The coatSEAL Flexi-LF chamber doctor blade end seals are primarily suitable for solvent-based and water-borne inks. They show their particular strengths at printing speeds of more than 400 m/min, but can certainly also be used for lower speeds if a particularly long seal life is desired.

coatSEAL Universal – high end solution

The Universal material consists of wear resistant rubber, which is suitable for all kinds of printing inks and cleaning agents and performs extremely well also in high speed applications.

Universal end seals are complex designs that are adjusted with highest precision to the chamber geometry and can only be manufactured in a molding process. Therefore this sealing concept is mainly used for high volume serial production.

A selection of coatSEAL Universal seals is already available in the Agergaard Online Store.

coatSEAL Universal for flexo printing

coatSEAL AIR80 – masters solvent/high speed

The AIR80 material is a special synthetic with strong chemical resistance. This material performs very well with solvent based inks but is also a feasible option for water based inks.

Thanks to their extremely high restoring force AIR80 seals withstand compression and distortion and thus qualifiy for mechanically demanding applications.

If used for high speed printing, the contact zone with the anilox roller can be coated with a PTFE layer, which reduces friction, diminishes ink residues in the sealing area and extends the seal life time.

coatSEAL AIR80 for solvent printing
coatSEAL AIR80-PTFE for solvent high speed printing

coatSEAL Longlife – for water based inks

Longlife B (black) and Longlife W (white) end seals consist of different felt types, which are treated with a special thermo impregnation. The lubricant which is used for impregnation is food and cosmetic safe, that is why this sealing concept is often used for packaging printing applications.

End seals made of the Longlife material show a remarkably long lifespan, especially in combination with water based inks, and thus keep the chamber leak-proof for a long period. Due to their lack of restoring force, the Longlife seals require a 100% adjustment to the chamber geometry in order to perform optimally.

coatSEAL Longlife W for water based and UV inks
coatSEAL Longlife B for water based inks

coatSEAL LD40 – multi-purpose

The LD40 material is synthetic foam with a very high flexibility. Being resistant against all usual printing inks and cleaning agents, it offers an good performance cost ratio. That is why it is often used for applications where the end seal is replaced after a job run.

This material can also be a feasible concept for presses that run at relatively low speed and thus do not wear off the seal heavily.

For applications, of which the exact chamber geometry is not 100% determined, the LD40 represents the ultimate choice because it adapts easily to the chamber outline.

coatSEAL LD40 foam end seal

coatSEAL Flexi NW - ideal for UV

The Flexi NW material is stiff synthetic foam that is often used when the set up of the chamber doctor blade system requires a rather thin end seal.

While it can be used for all ink systems, it performs especially well in combination with UV inks.

coatSEAL NW for UV inks

Translating the concept into a tangible sealing solution

Next, we decide on the most suitable production method depending on the material and job lot. The different options available are: water jet cutting, CNC cutting, punching or even injection molding. Choosing the right production method is crucial to achieving smooth sealing surfaces and a neat sealing shape.

Since the Agergaard Company produces in house, we have 100% control about the final outcome. That includes consistent quality controls throughout the production cycle in order to ensure that our customers continuously receive an end seal of reliable quality.

OEM end seal development
Agergaard end seal production
coatSEAL Universal end seal production
Agergaard end seal quality control

Taking advantage from coatSEAL best practice

No matter what printing application an end seal is required for, if it is a Comexi, Windmöller & Hölscher, Uteco, Schiavi, Fischer & Krecke, Bobst, Gallus, Flexotecnica, Bielloni, Martin, Nilpeter or another press, whether it is equipped with a Tresu, Harris & Bruno, Absolute Engineering or another chamber system, we can work out a compatible alternative sealing solution that suits the individual requirements best.

In doing so, we do not necessarily need to start from scratch - there are a lot of coatSEAL solutions that have proven themselves already and are used at diverse printing shops around the world. Our flexo end seal catalogue gives some inspiration.

Dr. Dichtung with lubrication grease

Did you know that lubrication grease

can improve the performance of your end seal enormously?

It enhances the anti-frictonal properties of the seal, which means less ink residues causing leakage.

Also, it extends the seal lifetime.