DE102004039732A1 - Color film coating device for use in printing unit of rotary printing press, has roll coater whose supply and differential speed between backing roller and coater are controlled based on magnetic field strength of magnet within roller - Google Patents

Abstract

The device has a backing roller, a roll coater and a plate cylinder, which supports a printing plate. The coater is arranged downstream of the roller and is made of magnetisable material. An electromagnet is provided within a hollow space of the roller. Supply of the coater for color coating on the plate and the differential velocity between the roller and the coater are controlled based on magnetic field strength. An independent claim is also included for method of coating a color film.

Description

The The invention relates to a device and a method according to claims 1 and 29th

In Inking units for the conventional offset printing, as the majority of them all Offset machine manufacturers are used, the ink supply takes place from a color reservoir, e.g. the color box, by an oscillating Color lifter roller in the inking unit. In sheetfed and web offset these are Color elevators mostly used. In this type of inking unit receives the ink fountain roller through the ink ductor a relatively thick ink layer over the Width zonal may be different, and transfers by rolling a part of the strip on the first roller of the inking unit. The dosage of fed amount of color takes place in an inking unit that with a oscillating color lifter works, by the angular velocity (corresponds to the strip width) and the cycle time of the lifter (lifter frequency). Zonal can be the color amount by a zonal different scribing on the paint ductor, for the e.g. Color slides can be used to be differentiated. This type of inking works is differentiated from the so-called Short inking units are referred to as long-inking units or long inking units.

Known as long inking units are, for example, so-called film inking units. Film ink works represent a special feature of the long inking works. Film inking units do not transport the ink from the ink fountain roller over one oscillating color lifter in the inking unit, but stand out characterized in that between the usually slower rotating ink fountain roller or Farbduktor with this cooperating Farbdosiereinrichtungen (e.g., color pushers) and with the first, faster-going inking roller a predetermined gap prevails over which the paint in the inking unit is dosed. The dosage is typically continuous.

A combined film and Farbheberfarbwerk is known inter alia from EP-PS 0036103 and other documents. In the DE 3804204 Another film inking unit is disclosed which allows for recirculation of excess ink into a color reservoir.

Long Ink units have a number of advantages and disadvantages. The advantage such film and Farbheberfarbwerke lies in the high Dosierbandbreite, connected mostly with one over the width of the ink ductor roller zonal differentiable ink layer thickness, and the possibility the visual appearance of the print (color layer thickness, color tone) while to adapt to the pressure. But the large number of dosing options also require long set-up times and spoilage (misprints due to Hue deviations), which by modern color control systems, although clear minimized, but ultimately still too high. It is a clear trend towards smaller runs (lot sizes) in the printing industry clearly recognizable and thus increases the percentage cost burden of the entire contract due to the unavoidable waste (committee) clearly indicating the profitability over others Printing process, such as photocopy, is at risk. At short runs endangered caused by the adjustment process (color profile adjustment) Waste also clearly the profitability therefore, because at For many printed products, the proportion of material (substrate and Color costs) significantly over 50% of the total production costs.

One Another disadvantage of Farbdosiereinheit with Farbduktor, zonal dosage by means of slide openings is that an automation of the dosing process is limited, because the individual manipulated variables are not are independent of each other and the connections can not be described with simple linear equations. An enlargement of the slide opening leads e.g. also to an extension of the Farbheberstreifens (removal strip on the Farbduktor), since the dye lifter dips into the thicker color film earlier and appears later. On the other hand, a thicker color film can also lead to a "floating" of the color lifter in the Submerge in the paint film on the ink ductor, which is no longer the maximum possible amount of paint is removed. Due to the corresponding control variables (color slider opening, Color roller speed, Farbheberktstreifen, Hebertakt, color viscosity) and the related non-linear relationship equations is also a non-expert viewer recognizable that automation difficult to realize.

A further disadvantage of inking units which work with ink drawers is that the thick ink lifter strip delivered by the ink lifter to the compactor of the inking unit must be split and rearranged several times in a roller inking unit, so that the inking rollers on the printing areas of the printing form have a constant color film small thickness can offer. Another disadvantage of this method is that there is no continuous color flow. The reason for this is the discontinuous ink feed (system squeegee and duster roller) as well as the discontinuous ink transfer to the substrate (non-printing and printing elements on the printing plate). These two factors require a high storage capacity of the inking unit, in order to cushion the different color requirements, and a large number of Cleavage points, which make it possible to even out and split the thick strips of color fed into the compactor by the dye lifter. Due to the large number of nips an inking unit but also sluggish, since an adjustment to the actuators for the Farbwerksdosierung only with a time delay, which are caused by the long compactor, make noticeable on the sheet. Since production normally continues during the color dosing corrections, waste (scrap sheets) are created because the print products do not yet have the final target color.

at the long roller inking, the use of a color lifter for Achieving uniform coloring required are, arises while of the printing a so-called color gradient, i. in the upper area of the compactor is a high layer thickness, with the number the cleavage points in the direction of inking rollers decreases continuously. This color gradient equalizes during one Complete printing interruption, so that on all rolls at the beginning of production a uniform layer thickness is present. this leads to in the case of a restart of a production to distinct color deviations, first are the printed sheets usually over-dyed, then under-inked, before then the target color become level. Due to this fact fall in the long roller inking also a big Number of waste paper, especially for short runs and costly Substrates threaten the cost-effectiveness of the process.

A generic film inking is, for example, from the DE 29 42 734 known. Characteristic of film inking units is that there is a minimal gap between the ink fountain roller, often called the film roller, and the first roller of the inking unit, through which the ink is transferred. Although a continuous ink feed takes place in the film inking units, problems arise in that no return of excess ink into the ink reservoir can occur, ie without a doctoring device, too much ink fed into the inking unit can only be discharged from the inking unit via the printing material become. This can take a very long time at very low surface coverage of the print motif, resulting in a correspondingly high number of waste (scrap) arise. This circumstance means that correspondingly elaborate Abrakelvorrichtungen be provided for such inking types, as for example in the DE 38 04 204 are provided. The scraping of pasty paint, as they are used, inter alia, in sheetfed offset, is very difficult and the doctor devices are subject to constant wear, so that a uniform dosage over long distances is not always guaranteed.

Also known are so-called anilox inking units. An alternative inking concept is represented by the anilox printing units, as used for example in the DE 38 38546 and the DE 42 11 379 were revealed. Anilox offset short inking units of the generic type have no zone screws or color slides, but a built-in, abrakelbare anilox roller, as for example in the DE 38 22 692 was shown on, so that the amount of ink to be transferred is no longer directly influenced. The amount of ink transferred depends in the first line on the screening of the screen (anilox) roller, and on the physical properties of the ink used. The constant refilling of the wells prevents a sujet-related relief formation, and eliminates the necessary for the compensation of such irregularities, machine-related effort in conventional inking works. A short and responsive inking is the result. Ideally, the hard raster (anilox) roller acts against a single, soft inking roller that is approximately the same size as the plate cylinder. This arrangement allows stencil-free printing. The advantages of this process combination lie in the uniform coloring and in the low Makuiaturanfall this inking combination.

Of the Disadvantage of this inking configuration is that it is is a deterministic coloring process, i. the Coloring the Printing form is determined by the filling volume the sieve cups and Raster geometry of the raster (anilox) roller certainly. An adaptation of the coloring to the requirements of the print job is only to a very small extent due to a change the temperature of the aggregates involved and the change the Walzenbeistellungen to each other possible, since a temperature change the emptying behavior of the sieve cups and the color transfer behavior influenced between the roll groups involved. The temperature control However, it is very complex and only to a very limited extent possible and is partly due to the environmental conditions of the printing press (Room temperature).

Such tempering of a short inking unit is in the DE 197 36 339 described. According to the invention, a temperature in a printing unit, in particular on the anilox roller or on the inking roller or on a printing cylinder, ie in particular the forme cylinder or the transfer cylinder (blanket cylinder) or in the ink is changed so that the desired value, for example a certain densitometrically detected density results because there is a relationship between the temperature conditions in the printing unit and the transferred amount of ink in the printing unit from the inking unit to the substrate. Due to the changed Druckbe Conditions which affect the printing ink are influenced by their rheological properties, which in turn alters the color-splitting and thus the ink transfer behavior.

Adverse is also anilox offset printing units that due to the deterministic Coloring and the difficult emptying of the sieve cups Use of pasty Offset inks, the range of usable inks very low is. Every ink for This procedure must comply with exact rheological requirements. The pigmentation with color pigments of the offset printing ink is allowed only subject to very slight fluctuations in order to avoid color deviations so it needed is to control and print each production batch separately. Thereby can only special color types for this method can be used.

The Anilox offset inks are also less viscous than in offset printing with long inking units to ensure a stable Entieerverhalten of the cups of the Anilox (raster) roller to ensure. This has the further disadvantage that low-viscosity offset printing inks usually a higher one Can absorb proportion of dampening solution. This is not necessarily disadvantageous, as long as the dampening solution finely emulsified into the ink is. Nevertheless, the anilox process is designed using Offset ink and dampening solution, also wet offset process, as very difficult to dominate. Moisture accumulations on the detent roller can the Color transfer process to disturb and the paint can easily tip over in the inking unit if it is too close high saturation having an emulsified fountain solution. Here proves the low surface of the short inking unit, and associated evaporation surface, and the small number of cleavage sites as disadvantageous. In long inking works In contrast, at each nip the emulsion of ink and Dampening solution reconditioned. This problem led to that the majority of anilox short inking units on the market today in the so-called waterless process, without dampening, work. The wet offset plates are made by the well-known Toray printing plates for the replaces waterless offset printing, which means printing without dampening solution allow. However, this type of printing plate is more expensive than wet offset plates and has a much lower prevalence.

Of the mechanical design effort of a short anilox offset inking unit lets in cost-effective Expect the opposite, but the opposite is the case. Usually Anliox offset printing units are at least as expensive as they are long Offset printing units. The reasons therefor are the costly anilox (raster) roller and the high effort, the one for the Ink unit temperature control must be operated.

The required Special materials, the limited control options the coloring and the high cost of the anilox printing unit let this only as an alternative to the long roller inking units for one restricted Area of the printing market. For the broad use it is not suitable.

Finally, metering systems using doctor blades are also known. In the DE 30 49 009 a construction of a short inking unit is disclosed in which the ink is doctored off by a fixed squeegee from a roller and the scraped-off ink film is then smoothed by a roller group. However, a doctor blade doctor blade has the serious disadvantage that the doctor blade tips wear out very quickly, thereby changing the metering behavior. In addition, the Abrakelverhalten depends, depending on whether it is negative or positive blade delivery to the roller, by the amount of ink that is in front of the squeegee, influenced by hydrodynamic effects and the different pressure on the squeegee tip.

Farther Dosing systems are also using the adjustment of two Rollers proposed to each other.

In the DE 2 323 025 discloses a form of short inking units in which the ink is applied in excess to the inking roller and the excess amount of ink, before contact with the printing plate, is doctored by a metering roller, which is employed against the inking roller and in the opposite direction of rotation Direction of rotation of the inking roller moves.

In This patent is illustrative of the dosage over the Provision of two rolls to each other and by a differential speed and associated shear of the ink in the metering gap disclosed. However, the combination of soft and hard roller has the disadvantage that the metered amount depends heavily on the hydrodynamic pressure and depending on the printing speed is. The dosing behavior is highly non-linear and automation This dosing is thus feasible only at great expense.

Also in the well-known Zweiwalzenlackwerken, as they were among others earlier The MAN Roland sheetfed presses were used, the Dosage over the combination of a hard and a softer roller.

Another Dosiermöglichkeit consists in the roller pairing of two hard rollers, which are provided to each other. This pairing offers one Very well describable and defined dosing behavior, but places high demands on the surface quality of the roll surfaces. The metering of ink by means of a steel film roller and a steel metering roller is in the DE 39 23 037 disclosed. The metering takes place here by the provision of the rollers to each other and by the differential speed of the rollers to each other. The rollers must be made extremely stable, otherwise they would show excessive deflections, whereby a stable color across the width would not be possible. In addition to the high demands on surface quality, this is a cost-driving factor.

A special feature of the roller combination are the so-called Rollrakeldosiereinrichtung. Generic is that a hard roller of significantly smaller diameter is provided against a smooth roller with a larger diameter. The squeegee can be smooth, but usually has a screening or other structuring and thus replaced the raster (anilox) roller of the anilox process. The application of this dosing method is exemplary in the EP 0 546 454 and US 3,559,572 disclosed.

The dosing accuracy of this dosing process is very accurate and meets all the requirements of the offset process. The disadvantage of this method lies in the small diameter of the roller blade, which, depending on the provision of the roller pairs, very easily tends to deflection of the roller body. Without corresponding support elements, which are arranged over the width of the roller blade, a trough-shaped layer thickness profile across the width would result due to the deflection. An essential requirement of a metering system for printing inks, however, is that the cross-section has only very small deviations, since there is hardly any possibility in the subsequent roll groups of compensating for an uneven layer thickness profile. The requirements in offset printing are particularly high, since a layer thickness of 2-10 μm must be exactly maintained on the application roller, which is placed against the plate cylinder. Therefore, roller blades must be supported at least in several places over the length. Usually, roller blade beds in so-called squeegee, often made of an elastic material, stored, which usually extend over the entire length of the roller blade. Such a squeegee assembly with a corresponding storage is inter alia in the DE 295104 . DE 196 02 483 . DE 30 22 955 and the DE 100 45 515 disclosed. The disadvantage of these solutions is that the storage beds wear over time and therefore need to be replaced regularly. The cleaning of such Rollrakelbaugruppen is very difficult and can be automated only to a small extent, since the coating material also serves as a lubricant between roller blade and storage bed. Therefore, the rolling doctor groups must be regularly cleaned and maintained and thus lead to higher set-up times.

A possibility stocks therein, the roller blade by a soft, resting on the roller blade counter roll over the Width to support. This solution However, has the disadvantage that the possibility of dosing by Differential speeds between the pairs of rollers would be very limited, otherwise at high differential speeds, the soft roller a very subject to high wear would. Partial support the squeegee by training wheels, the press the roller blade against the smooth roller is known, but leads to the lack of color at the nodes and the unevenness the color film after the metering process by further smoothing rollers, which preferably change, is smoothed. But it is known that Traversing process dependent from the relative speed of the rollers to each other, the coloring affected.

Desirable would be therefore a roller blade against a counter-roller or two hard rollers against each other or to fix a pair of rolls hard roll soft roll so that the contact force between the rollers is uniform across the width. In a roll-doctoring counter-roller combination, it would be desirable without touching support elements to get to fix the squeegee. Another demand an ideal dosing system for Printing inks would be, that no or only a very small deflection of the roller blade or the rollers over the width occurs and thus the metered layer thickness is extremely uniform.

A realistic solution this task could be that the squeegee at least partially made of a magnetizable Material exists and the Ge genwalze is designed as a hollow roller, the inside a magnet, preferably an electromagnet, contains which fixes the roller blade on the counter roll. The squeegee is in this case, ideally, floating and / or axleless or stored largely force-free, so that by an external force no deflection of the roller occurs.

A similar solution could be chosen when mating two rollers to each other. A Roller would be formed as a hollow roller containing a magnet, and the other roll would exist at least in part of a magnetizable material. Again, could the bearings of the rollers largely force-free, so that no through Force generated deflection occurs.

The Provision between the roller pairs would be across the entire width the magnetic force, which in the case of the use of an electromagnet, also changeable would.

Such solutions are already used successfully in paper finishing. In the DE 36 18 935 discloses a device consisting of a magnetizable anilox roller and a hollow roller as a counter-pressure roller containing a magnet. The paper web to be coated passes between the anilox roller and counterpressure roller and the anilox roller is pressed against the paper web by magnetic force exerted by the magnet in the counterpressure roller.

In the DE 37 41 630 Another device is disclosed, characterized in that an applicator roll above, below or laterally arranged to a magnetic field generating means and simultaneously immersed in a supply of the flowable medium (coating color). This device is intended for direct application of the medium to a sheet-like carrier (paper web). The applicator roll is mounted without bearings.

In the DE 8706186 discloses another embodiment of such a metering device, characterized in that the magnetic applicator roll is arranged obliquely in the vertical direction. This device is also intended for the direct coating of a sheet-like material web.

In the DE 92 14 884 is another manifestation of a magnetically fixed doctor bar for direct or indirect coating of paper webs disclosed.

In the DE 200 10 388 an indirect coating device is described, characterized in that the application roller is a hollow cylinder and includes a magnet which controls the supply of a metering / scoop roller to the applicator roll. The coating agent is applied indirectly to the paper web via the application roller.

In the DE 295 17 095 Another device for double-sided coating of a paper web is disclosed. Again, the provision of the rollers, reinforced and regulated at least for the lower roller group by magnetic force.

devices, for direct or indirect coating of a paper web in which the provision between two rollers controlled by magnetic force are therefore state of the art.

A such solution for the Dosing in an inking unit, the at least one plate or forme cylinder, with a printing form located on it, are not known.

task The invention is to provide a short inking unit, the one Color control via a wide adjustment range and largely to the use of special materials, like special printing inks, and thus the restrictions an anilox inking picks up. According to the invention this is achieved by the dosage by the provision of two pressure rollers and optionally a differential speed between the two rollers takes place.

characteristic for the Invention is that the provision between the two rolls by Magnetic force occurs and so a deflection is avoided, the the uniformity the color scheme over the Width could influence. As a special feature are a twin-roller metering device or a roller doctor metering device described. These types of metering devices can find application in offset inking units or in flexographic works.

A different possibility that would be Roller blade or a roll of a permanent magnetic material and the counter roll of a metallic or another magnetizable To design material. Also, the design of the backing roll permanent magnetic material and one metallic or another To counteract magnetizable material Rolling bar provided. The design of both rolls of a permanent magnetic Material would be conceivable, taking on the polarity would have to be respected. With these devices could a uniform contact pressure of Rolling doctor be achieved, but with a control of the provision between roller blade and counter roll would have to be dispensed with. A Differentiation could can only be achieved when the roller blade driven and the differential speed between Roller blade and counter roll would be adjustable.

According to the invention is a Device for inking in a printing unit created, that at least one plate or plate cylinder, which is a printing forme wears or himself carrier the image information is included. Characteristic of the dosage The color is that the provision of two rolls or each other for metering the ink largely by magnetic force.

The roller pairings are hard roller-hard roller, hard roller-softer roller or roller roller blade possible combinations in the sense the invention. It is characteristic that at least one roller of the named roller pairings is a hollow roller which contains one or more magnets in the interior of the roller and the counter roller consists at least partially of a magnetizable material or this itself is designed as a hollow roller with an internal magnet. Each of the rollers may have its own drive, which serves to generate a differential speed between the rollers or optionally for generating a differential speed between the roller, which is in contact with the printing unit, and the printing unit. As a magnet in the sense of this invention, all types of permanent magnets and / or electromagnets are conceivable. Electromagnets have the advantage that the provision would be changeable.

The Metering roller is preferably a roller blade or a roller blade assembly, because a roller blade allows a very exact dosage and cheaper as an anilox roll. The squeegee can either be a smooth or structured surface exhibit. The structure can be an engraving, a defined roughness be a cut or any other structuring.

the Roller blade can be a smoothing roller be downstream in the direction of rotation of the counter roll, said smoothing roll a lower level of provision the counter roll than the squeegee has.

When another characteristic can be a zone over the pressure width divided roller blade serve that in the hollow roller Zone-wise controllable electromagnets are opposite. This would be one Zone-wise dosage quite conceivable.

When another characteristic the invention is that a roll to at least a part of a Magnetic material is made and the counter roll to at least formed of a magnetic material with a different polarity is or consists of a magnetizable material.

Also describes the invention method for controlling the coloring by means of a Device according to the invention.

Claims (34)

Device for dosing a defined color film in a printing unit of a rotary printing press, the at least two Rollers for metering the ink and a plate cylinder or Contains form cylinder, who wears the printing form, characterized in that a roller of the metering roller group as a hollow roller is formed and in the cavity at least one magnet contains and the other roller of the metering roller group as a roller blade or roller blade group is formed and at least one squeegee to at least partially is made of a magnetizable material, Device according to claim 1, characterized in that both rolls of the metering roll group have similar dimensions and a roller of the metering roller group is formed as a hollow roller is and contains at least one magnet in the cavity and the another roll of the metering roll group a roll of at least one partially magnetizable material. Device according to claim 1, characterized in that that both rolls of Dosierwalzengruppe formed as a hollow roll are in their cavities have at least one magnet, wherein the polarity of the magnets is different in both rolls, Apparatus according to claim 1 to 3, characterized in that it is the magnet or magnets in the cavity or in the cavities the hollow roll is permanent magnet, Apparatus according to claim 1 to 3, characterized in that it is the magnet or magnets in the cavity or in the cavities the hollow roller is about electromagnets, Device according to claim 5, characterized in that that at least one electromagnet is electrically controllable, Apparatus according to claim 1 to 3, characterized in that the rotational speed of the rollers of the metering roller group within equal tolerance limits, Apparatus according to claim 1 to 3, characterized in that there is a differential speed between the rollers of the metering roller group, Apparatus according to claim 1 to 3, characterized in that the direction of rotation of the rollers of the metering roller group is in the same direction, Apparatus according to claim 1 to 3, characterized in that the direction of rotation of the rollers of the metering roller group is opposite, Apparatus according to claim 1 to 3, characterized in that the roller of the metering roller group, with the subsequent Inking unit or printing form in contact, one in close tolerances identical At catch speed like the printing unit or the plate cylinder having, Apparatus according to claim 1 to 3, gekenn characterized in that the roller of the metering roller group, which is in contact with the subsequent inking unit or printing forme, has a differential speed to the peripheral speed of the inking unit or of the plate cylinder, Apparatus according to claim 1 to 3, characterized in that both rolls of the metering roll group have a smooth surface, Apparatus according to claim 1 to 3, characterized in that at least one of the rollers in the metering roller group having a structuring, wherein the structure is an engraving, a defined roughness of a cut or any other type of structuring can be, Apparatus according to claim 1 to 3, characterized in that pulled by the magnetic force against the hollow roller Roller is mounted largely force-free, Apparatus according to claim 1 to 3, characterized in that pulled by the magnetic force against the hollow roller Roller is largely floating, Apparatus according to claim 1 to 3, characterized in that pulled by the magnetic force against the hollow roller Roller is mounted so that even without the action of magnetic force a small provision of the rollers is present to each other, Device according to one of claims 1, 5 or 6, characterized in that the roller blade is divided in zones and with the same Zone width divided, controllable electromagnets in the hollow cylinder interact. Apparatus according to claim 1 to 3, characterized in that the ink layer thickness across the width after the metering is identical within narrow tolerances, Apparatus according to claim 2 or 18, characterized in that the ink layer thickness across the width of the metering may be different Device according to 1 to 3, characterized by that after the metering point, one or more smoothing rollers follow, which with at least a roller of the metering roller group interact, Apparatus for carrying out the method according to claim 1, characterized in that a roller of the metering roller group at least in part from a permanent magnetic material and the counter roll consists of a magnetizable material, Apparatus for carrying out the method according to claim 1, characterized in that both rollers to at least one Part consist of a permanent magnetic material, the polarity of the magnetic field is different for both rolls, Apparatus according to claim 1 to 3, 21 or 22, characterized in that at least one roller of the metering roller group in contact with the inking unit of an offset printing machine, Apparatus according to claim 1 to 3, 21 or 22, characterized in that between a roller of the metering roller a defined Gap distance and the first roller of the inking unit prevails and the Color over this gap is metered into the inking unit, Apparatus according to claim 23 or 24, characterized in that the inking unit is a multiroll inking unit These, Apparatus according to claim 23 or 24, characterized in that the inking unit is a narrow-cylinder plate-sized inking roller having, Apparatus according to claim 1 to 3, 21 or 22, characterized in that at least one roller of the metering roller group in contact the printing form of a flexographic printing works stands. Method for dosing a defined color film in a printing unit of a rotary printing press, the at least two Rollers for metering the ink and a plate cylinder or Contains form cylinder, who wears the printing form, characterized in that the dosage of the color film through the Provision of two, preferably hard, rollers to each other and the provision of the rollers to each other at least partially Magnetic force is generated. Method for controlling the coloring by means of a Device according to a or more of the claims 1 to 28, characterized in that the provision of the rollers the Dosierwalzengruppe to each other depending on the machine speed changed the printing press becomes, Method according to claim 30, characterized in that that the amendment change the rolls of Dosierwalzengruppe to each other on the basis of a characteristic for the allocation of the machine speed and power of the electromagnet at machine speed changes is changed. Method of controlling the coloring with A device according to one or more of claims 1 to 28, characterized in that one or more sensors measure the layer thickness of the ink film after the metering point on one or both rollers of the metering roller group and the measured layer thickness is adjusted in a control device with a nominal layer thickness and at Deviations from the nominal value the provision of the rolls of the metering roll group is changed by activation of the or the electromagnet until the desired ink layer thickness is achieved in the best possible way, Method for controlling the coloring by means of a Device according to a or more of the claims 1 to 28, characterized in that inline in the printing press or offline outside the printing press densitometrically on one or more densities be measured in several single-color or combined printing fields and the measured color density or densities in a controller be matched with a nominal density or with nominal densities, and in case of deviations from the nominal value, the provision of the rollers of the metering roller group as long as it is changed by controlling the electromagnet until the respectively desired Color density best possible achieved. Method for controlling the coloring by means of a Device according to a or more of the claims 1 to 28, characterized in that inline in the printing press or offline outside the printing press the color locus spectrophotometrically on one or be measured in several single-color or combined printing fields and the measured color location or color locations in a controller matched with a target color location or with target color locations and in the case of deviations from the nominal value, the provision of the rolls of the Dosing roller group as long by controlling the electromagnet changed becomes the desired color location best possible achieved.