Abstract:
A method and an apparatus for compensating for inking differences between setpoint color values and actual color values in offset printing presses having at least one inking unit and a control computer. The control computer controls the printing speed of the offset printing press and the temperature control of rollers in the inking unit of the offset printing press. The control computer is set up in such a way that, if an inking difference is detected between the setpoint color values and the actual color values, a combined control operation including a change in the printing speed and the temperature in the inking unit is performed in order to compensate for the inking difference. A printing press having the apparatus is also provided.
Abstract:
A method for controlling inking units having a plurality of zones and/or dampening units in printing presses, includes determining reference values, which are dependent on surface area coverage and/or location, through the use of a computer for the inking zones in the inking unit. Deviations of detected color measuring values from the reference values are calculated for each inking zone. The calculated deviations are compared with data stored in the computer and corresponding with causes of color problems. The computer determines causes of color problems in the inking unit and/or dampening unit by comparison with the data.
Abstract:
A process for adjusting the print image of a rotating machine equipped with transfer rollers and actuators assigned to them includes changing the position of the rollers. During the printing operation, at least one camera records the intensity of light reflected from the printed material. The camera also feeds the recorded measured values to a control and regulation unit that compares the recorded measured values with set values, and generates corrective signals for the actuator of at least one part of the rollers involved in the printing process. Based on the corrective signals, the actuator of the relative position of the roller assigned to it is actuated until the measured values once again lie within a tolerance range.
Abstract:
An ink feeding method for a printing machine includes a color density measuring step for measuring color density of prints at intervals of time, a variation coefficient computing step for computing a variation coefficient for varying the ink feeding rate based on the color density of prints and a target color density of prints, a color density gradient computing step for computing, based on the color density of prints, a color density gradient representing a rate of variation in the color density of prints occurring with an increase in the number of prints, an expected color density computing step for computing, based on the color density gradient, an expected color density of prints occurring after a predetermined number of prints are made, a determining step for determining whether the expected color density of prints occurring after the predetermined number of prints are made exceeds the target color density of prints, and a variation coefficient correcting step for correcting the variation coefficient when the expected color density of prints is determined to exceed the target color density of prints.
Abstract:
Introduced are a device and a process for setting the printed image of a rotary press by adjusting the relative position of the rollers (3, 7, 8) involved in the ink transfer. In this respect at least one part of these rollers (7, 8) can be moved toward each other both together and also independently of each other by means of their own actuating drives (M1 to M4), so that the rollers (3, 7, 8) involved in the printing process can be set into motion in relation to each other, In addition, there is at least one camera (K) that scans the printed image (10) on the printed material web (17) and that feeds the images shot in succession to an electronic control and regulating unit (13). This control and regulating unit (13) generates signals for the actuating drives of at least one part of the rollers (3, 7, 8) involved in the printing and inking process until or as the printed image is reproduced without area loss.
Abstract:
To improve the control of the inking process in an offset printing machine, color measuring fields provided on printed sheets are evaluated not as heretofore densitometrically but colorimetrically by means of spectral measurements. Spectral reflections are used to match colors, or color coordinates are calculated from them and compared with corresponding set reflections or set color coordinates. The color deviations obtained in this manner are used to control the inking process. For the stabilization of printing runs the spectral reflections are converted into filter color densities and the inking process is controlled on the basis of these color densities in a conventional manner. The control of the inking process using color deviations and control using color density may be superposed upon each other.The process makes it possible to adapt color impressions in delicate locations of importance for the image in the print to the corresponding locations of the proof. Color deviations due to different material properties and other error sources may also be equalized to some extent.
Abstract:
The invention relates to a method and device for detecting ink or lacquer films on metallic surfaces inside printing machines. In particular, to irradiate the surface with light and sensing of the intensity of the reflected light to detect whether an ink film or lacquer film on a roller has been completely removed by applying a metering element or doctor-blade element. This is achieved according to the invention by the irradiation of the metallic surface or of the film located thereon, and the reception of the light reflected from the surface or the film located thereon is performed at the Brewster angle with respect to the surface normal, the Brewster angle being defined by the refractive index of the material of the film to be determined and that liner polarization of the light is performed at least partially in the plane of incidence, at least in one of the two beam paths.
Abstract:
In a stencil printing machine, when quantity of ink supplied into an ink supplying section in a rotary cylindrical drum is smaller than a predetermine value, ink complementing means is driven to supply ink from an ink storing container into the ink supplying section, and when the quantity of ink in the ink supplying section does not reach the predetermined value within an ink-complementing-means operation time, a determination is made that no ink is left in the ink storing container, and a warning signal is produced. The stencil printing machine comprises: a quantity-of-ink detector for detecting whether or not the quantity of ink in the ink supplying section has reached the predetermined value; a kind-of-ink detector for detecting the kind of ink supplied into the ink supplying section in the rotary cylindrical drum; and controller which operates to change, according to the kind of ink detected by the kind-of-ink detector, the ink-complementing-operation time which elapses until a determination is made that no ink is left in the ink storing container.
Abstract:
In a stencil printing device in which printing ink is supplied to the inner surface of a printing drum, and printing paper is pressed onto a stencil master plate sheet mounted on the outer circumferential surface of the printing drum by using a press roller for effecting a stencil printing on the printing paper, there are provided dip switches in the printing drum for identifying the type of the printing ink supplied to the inner surface of the printing drum, and the pressing force of the press roller against the printing drum is variably determined according to the detected type of the printing ink set on the dip switches so that a stencil printing is carried out with a prescribed printing density without regard to the type of ink, in particular the color of the printing ink used with the printing drum. An alternative device determines material properties of the ink including temperature, color, viscosity and opacity of the ink so that pressing force of the roller against the printing drum can be variably determined.
Abstract:
An on-plate water film sensor for printing machines uses a narrow-band light source, a photo modulator for chopping a light beam therefrom into p- and s-polarized beams, a collimator for making parallel the rays of the collimated beams with a given cross-sectional area for measurement, a wavelength plate for adjusting the wavefront of the parallel rays, a receiver for the light secularly reflected from a plate, and an arithmetic unit to figure out the thickness of a water film formed on the plate based on the intensities of the received beams. Water lining which usually has patterns of narrow width can be detected, and the measurement of a water film thickness can be done with high speed.