WO1981000083A1

WO1981000083A1 - Method and device for determining order values allowing particularly the automatic control of printers

Info

Publication number: WO1981000083A1
Application number: PCT/EP1980/000041
Authority: WO
Inventors: A Beckert
Original assignee: Mohn Gmbh Reinhard; A Beckert
Priority date: 1979-07-02
Filing date: 1980-06-30
Publication date: 1981-01-22
Also published as: EP0031829A1; DE2926629A1

Abstract

The variations of energy of an energy beam is measured and the measured values may be modulated by means of microprocessors to obtain the order values by directing an energy beam to the surface of a printing plate (12) and by measuring the energy reflected by the surface of the plate. It is important to use a non-gummy printing plate and a laser beam allowing the measuring in surface density of the surface of the plate. The device for applying such process comprises a scanner operating according to the reflection principle and which is arranged in a processing machine (14) for printing plates.

Description

Method and device for determining target values for the in particular automatic presetting of printing presses

Through an automatic presetting of e.g. B. and sheet printing machines /

As is generally known, set-up times can be shortened considerably, rotary presses / before printing with pre-determined target values, waste can be reduced, similar, recurring print jobs can be processed more efficiently and the working time of the operating personnel can be simplified. Mainly the coloring, the paper feed and the registers are preset with the target values, however the ink zone presetting takes priority. The default setting is therefore primarily restricted to printing processes that work with roller inking units. Printing machines that are equipped with a remote ink setting are particularly suitable.

A method for determining target values for the automatic presetting of printing presses is already known. The target value serves in particular especially for pre-setting the knife distance to the ductor of the inking unit, so that the amount of ink is determined that is needed in each zone to print the desired shape. The amount of ink is a function of the area covered by the image to be printed within a color zone across the circumference of the plate cylinder. In the known methods, the target value for this so-called area coverage is determined from the litho film from which the printing plate is copied, using a densitometric measurement. A densitometer that works in transmitted light is used for this purpose, with which a zone-wide area coverage in the film original is recorded in a film scanning system. Negative and positive films or adhesive assemblies can be used. The zone-wide scanning takes place via glass fiber optics or light wells, with the measured values being electronically integrated and stored over the film length. For machines with two plates or for templates with several films in a row, the mean value from the different templates or films must be taken per zone. The averaged measured values are then converted into the target values using various electronic devices in accordance with the degree of automation of the method, and the target values are used for manual or automatic presetting. Numerous influencing factors are taken into account and coordinated with microprocessors. Such a method and a device for this purpose, for. B. in "The Polygraph", 30th year, Issue 8, dated April 20, 1977, pages 489-492.

A major disadvantage of the known methods and devices is the zone-wide scanning, which only in certain cases corresponds to the width of the zone setting of the inking units of a printing press. In this respect, there may be overlaps in the zones, which may lead to a falsification of the target value or the area coverage. The zone-wide scanning also has the disadvantage that it is not in every case a whole multiple of the original width or plate width, so that edge zones can exist in which the mean value of the measured values of the scanning zone is falsified. A further falsification of the average results when one and the same original has to be copied in large numbers side by side and / or one below the other on a disk and only the average of the zones of the original has been determined. B. is usually the case in the manufacture of a printing plate for a dust jacket or the like for a book or if only a part of the entire area of the original is covered, but the entire zone must be measured, or if the original is scanned several times, e.g. B. the image part, the text part or the template with 1 to 3 masks etc.

Furthermore, it is disadvantageous that in the case of several originals to be copied one above the other for a printing plate, i.e. A densitometric measurement must be carried out at least according to the number of templates, which is time-consuming.

The most important disadvantage of the known methods, however, is that when copying the originals, influencing factors can become so effective that the printing plate does not produce the printing image that is expected. For example, a grid can be falsified or overexposed or underexposed due to exposure errors. The object of the invention is to show a simple, fast-working method for determining the target value, which supplies more useful values for the presetting, and to provide a device with which the method can be carried out particularly easily.

This object is achieved by a method for determining target values for the, in particular, fully automatic presetting of printing presses, the energy change of an energy beam being measured and the measured values being modulated to target values, possibly using microprocessors, characterized in that the A running energy beam is projected onto the surface of the printing plate to be printed and the energy reflected from the surface is measured. A laser beam is preferably used; however, halogen or halogen vapor light can also be used. In particular, the area coverage, i.e. determines the printing area that reflects the beam.

Systems known per se can be used within the scope of the invention. These consist of a light transmitter that emits a driving beam. The driving beam is directed onto the surface of the printing plate and the reflected light energy is measured. The light beam can be reflected in itself (autocollimation) and fed to a receiver in the optical head, or it is received as a result of remission at a freely adjustable angle to the transmitted beam by a light guide system and fed to the signal converter. The measured values of the measuring devices are modulated in a manner known per se to set values and the set values are used for presetting in a manner known per se. A known device has a scanner, the task of which is to move a finely focused light beam continuously and always axially parallel over the printing plate surface. The scanner works together with the optical receiving unit, which is either integrated in the scanner or takes up the optical signals emitted by the printing plate surface in the reflection process and converts them into a video signal. The receiving unit is coupled to an electronic evaluation unit, which evaluates the received electrical signals via video processors and possibly microcomputers and, if necessary, prepares them for controlling the remote ink setting of the printing press.

The surface of the printing plate is scanned line by line with the light beam of high running speed of the automatic surface inspection system. It is particularly advantageous that the scanning of the printing plate in the movement is possible due to the high speed of the light beam. The scanning beam causes a constant light spot size over the entire scanning width of the printing plate, the light spot size or the light spot path of the beam being relatively small compared to the partial zone width of the inking unit. In this respect, it is possible to define scanning fields distributed over the surface of the printing plate, which correspond to the width of the zone setting of the inking units. This avoids the disadvantages of the known methods in connection with zone-wide scanning.

Typically, the scanner and receiver are coupled to an analog video processor, which is connected to a digital extractor is connected, the digital extractor being connected to a microprocessor. Influencing factors, in particular printing machine-specific data, can be programmed into the microprocessor in a manner known per se, which can be processed together with the measured values by means of an operating dialog. The data determined and output are the target date for the press presetting. The method according to the invention enables the target values to be determined in one operation by scanning the printing plate, which means a considerable saving of time. In addition, the element is scanned for what is actually printing, ie copy tolerances are also taken into account. In addition, the handling of a plate is much easier than that of films or templates; because a film is more likely to be damaged than a printing plate. The scanning zone width can be selected individually, so that the system can be used for different printing machines in relation to the ink zone width and plate size. Furthermore, the integration of the measured values can be optimized by the choice of the beam spot size and the feed. In addition, the relatively small point size allows additional information to be determined, e.g. B. whether the scanned zone is predominantly unprinted or predominantly printed with grids or predominantly over the entire surface and also to include this information in the target value calculation.

Since a process computer can be connected in the method according to the invention, the measured values can be output in a manner known per se via data carriers (tape, magnetic disk, punched tape, etc.) or forwarded directly to the printing press. As is known, there are different types of printing plates. They differ in terms of material and color. For example, printing plates are used which have an aluminum plate as the non-printing carrier plate with a plastic coating as the printing element. The plastic coating can e.g. B. be yellow, brown, blue or purple. In addition, the carrier plate can consist of non / copper or measurement, on which a printing

Chrome layer sits. For this reason, the reflection values for the light beam are different. However, the invention is also applicable to these different printing media. According to a special embodiment of the invention, the measuring device is calibrated accordingly before scanning a printing plate. For this purpose, one or more calibration markings are arranged on the edge of the printing plate, in particular on the clamping edge, which is known not to be required during the printing process. For example, a narrow full-area marking is arranged on the upper edge part, which corresponds to a 100% printing area. An unprinted area with a 0% printing area can be followed by a printing area with a 50% grid in the lower edge part. These markings are first scanned with the measuring device, the scanned values permitting a statement about the type and color of the plate. The samples are e.g. B. processed in the microprocessor and are used to convert the subsequently determined measured values on the printing plate or to preset the measuring device with respect to the energy density.

It is obvious that the new method can work independently of the plate size, the zone width and the zone number of the inking units. With the Characteristic values of the printing press and the printing plate, the scanning widths and scanning frequencies can be determined with the help of the microprocessor. The measuring device calibrates itself automatically before each scan due to the very original arrangement of calibration marks on the printing plate at a point that is not used for printing anyway.

The invention further relates to a device for carrying out the method according to claims 13 and 14.

The invention is explained in more detail by way of example with reference to the drawing. Show it:

1 is a known scanner that works according to the autocollimation process,

Fig. 2 schematically shows a printing plate developing device with a scanning device.

The scanner shown in Fig. 1 preferably works with laser beams. These are generated in the light transmitter 1, deflected via a mirror 2 and fed to a slit optics 3 with a translucent mirror 4. From there, the rays pass through a mirror 5 and a lens 6 onto a fast-running, multi-surface mirror wheel 7, wherein they are moved by the rotation of the wheel and sent to the plane mirror 8. The rays are reflected from the plane mirror 8 to the plane mirror 9 and from there to the concave mirror 10, which focuses them onto the printing plate 12 through a cylindrical lens 11. From there, the rays are reflected according to the reflectance values of the plate Location of the light spot reflects in itself and migrate the same way up. back to the partially transparent mirror 4. They are passed from the mirror 4 into the photoelectronic receiver 13 and registered as measured values. The measurement signals can be passed from the receiver 13 into an analog video processor, from there into a digital extractor and from there into a microprocessor, and then appear as averaged target values for a specific color zone setting.

2 shows a particularly favorable possibility for realizing the method according to the invention. The device shown consists of the printing plate development device 14 with various baths 15 known per se for developing the printing plate 12. Transport rollers 15 are arranged between the baths in a manner known per se, which transport the printing plate through the development device. The pressure plate travels through the individual development baths and then arrives at the measuring table 17, on which it is scanned before the rubber coating. After scanning, which takes place in the movement of the printing plate, it arrives in the rubber bath 18, in which it is finally rubberized in a manner known per se. It is therefore essential that the pressure plate is scanned before the gumming, since otherwise the surface of the pressure plate is changed too much.

For example, the known scanning system, which works according to the reflection principle, is used for scanning. In the drawing, the same numbers as in Fig. 1 have been used for the same parts, so that the one ins No detailed description is necessary. The known receiver 19 is designed as a selective reception system and is arranged outside the transmission device. It can have essentially three light rods 20. The light striking the pressure plate is directed into the middle light guide rod by remission. In the event of deviations from a certain surface condition of the printing plate, part of the remitted light is deflected into the light guide rods arranged on the side. The optical signals of all three light guide rods are evaluated in the electronics.

It has surprisingly been found that the different lines of coverage of the printing plates provide sufficiently differentiable reflections; this was not to be expected without further ado because the printing surface of the plates can be structured very differently. If the light spot size is selected correctly, very precise values for different lines of coverage can be obtained.

For metal plates in particular, it may be sufficient to measure the reflection in the bright zone with only one light measuring rod (FIG. 2), which is arranged in the area of direct reflection - in the case shown in the area of the central rod 20. The two rods arranged on the side are located in the diffuse area of the reflected beam and can be omitted if necessary or can be used to check the measurement. The direct reflection in the autocollimation process can also be measured.

It is particularly advantageous in the area of the bisector between the incident and the reflected Beam to measure the diffuse reflection in the remission method or accordingly / in the autocollimation method / next to the direct reflection; because it was surprisingly found that in the area of the bisector or at a certain angle, in addition to direct reflection, the greatest energy differences occur as a function of the area coverage. It has also been shown that this measuring method can be used to analyze the surfaces of all known printing plate types, including those of plastic plates or the like.

In addition, it has been shown that the energy beam not only for integrating the measured values for the zone-wide area coverage, but also for delivering a discrete statement at the measurement location in the area of the z. B. laser spots can be used.

Claims

Expectations

1. Method for determining target values for the in particular fully automatic presetting of printing presses, the energy change of an energy beam being measured and the measured values possibly being modulated with microprocessors, characterized in that a running energy beam is applied to the surface of the printing plate to be printed projected and its energy reflected from the surface is measured.

2. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that an ungummed printing plate is used.

3. The method according to claim 1 and / or 2, characterized in that a laser beam is used as the energy beam and the area coverage of the plate surface is measured.

4. The method according to one or more of the claims

1 to 3, so that the direct reflection of the reflectance is measured with metal printing plates.

5. The method according to one or more of the claims

1 to 3, so that the diffuse reflection is measured approximately in the region of the bisector between the incident and the reflected beam, preferably in the case of remission.

6. The method according to one or more of the claims

1 to 5, so that a light transmitter with a driving beam is used for scanning, the driving beam is directed onto the surface of the printing plate and the reflected light energy is measured.

7. The method of claim 6, d a d u r c h g e k e n n z e i c h n e t that a scanning system is used in which the light beam reflects in itself and is fed to a receiver in the optical head.

8. The method according to claim 6, d a d u r c h g e k e n n z e i c h n e t that a scanning system is used in which the light beam is received as a result of remission at a freely adjustable angle to the transmitted beam by a light guide rod system with three light guide rods.

9. The method according to one or more of claims 1 to 8, characterized net that the measured values are modulated in a manner known per se to target values and the target values are used in a manner known per se for the automatic zonal presetting of the inking units.

10. The method according to one or more of claims 1 to 9, d a d u r c h g e k e n n z e i c h n e t that the pressure plate is scanned line by line in motion.

11. The method according to one or more of the claims

1 to 10, so that the measured values of a printing plate width corresponding to the ink zone width are integrated and averaged.

12. The method according to one or more of claims 1 to 11, d a d u r c h g e k e n n z e i c h n et that the scanning device is calibrated with calibration marks on the printing plate.

13. The method according to claim 12, d a d u r c h g e k e n n z e i c h n e t that scanning marks are used for the calibration, which at the edge of the

Pressure plate, in particular on the clamping edge, are arranged.

14. The method according to claim 12 and / or 13, characterized in that the measured values of the calibration are fed to a microprocessor and are used to convert the subsequently determined measured values on the printing plate or to preset the measuring device in relation to the energy density.

15. Device for performing the method according to

Claims 1 to 14, d a d u r c h g e k e n n z e i c h n e t, that a known, works on the reflection principle scanning system in a known development machine for

Pressure plates is arranged.

16. The apparatus according to claim 15, characterized by the printing plate developing device (14) with various known baths (15) for developing the printing plate (12) and transport rollers (16) which transport the printing plate through the developing device, and a measuring table (17) in front the gumming bath (18) on which the printing plate is scanned, the scanning device being arranged above the measuring table (17).