AU658428B2

AU658428B2 - Process for setting a production-run ink profile

Info

Publication number: AU658428B2
Application number: AU21304/92A
Authority: AU
Inventors: Bernd Muller; Robert Muller; Anton Rodi
Original assignee: Heidelberger Druckmaschinen AG
Current assignee: Heidelberger Druckmaschinen AG
Priority date: 1991-08-28
Filing date: 1992-08-27
Publication date: 1995-04-13
Anticipated expiration: 2012-08-27
Also published as: JP3073609B2; EP0529257A1; ATE129193T1; DE59204053D1; DE4128537A1; DE4128537C2; EP0529257B1; ES2080388T3; AU2130492A; JPH05220936A

Abstract

The invention relates to a method for setting a production run ink zone profile of an offset printing machine. Firstly, an ink zone profile is set which is inverted relative to the desired ink zone profile and said inverted ink zone profile is then matched to the actually desired ink zone profile.

Description

AUSTRALIA

Patents Act 658428 COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: Name of Applicant: Heidelberger Druckmaschinen Aktiengesellschaft Actual Inventor(s): Anton Rodi Robert Muller Bernd Muller Address for Service: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Invention Title: PROCESS FOR SETTING A PRODUCTION-RUN INK PROFILE Our Ref 297694 POF Code: 1386/1386 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): 6006 6006 PROCESS FOR SETTING A PRODUCTION-RUN INK PROFILE The invention relates to a process for setting a production-run ink profile of an offset printing press with damping unit and inking unit, said inking unit comprising an ink-metering apparatus for setting an ink profile, with the applicator rollers of the inking unit and damping unit being moved permanently or temporarily into a position of engagement with respect to the printing forme.

In offset printing presses, it is necessary for a thin ink film to be supplied to the printing forme, said printing forme being wetted with damping solution. Use is made for this purpose of an inking unit, said inking unit being provided with a multiplicity of rollers. The damping solution is supplied by means of a dampinq unit, which likewise comprises a roller arrangement. Depending on the image on the printing forme, a suitably adapted ink distribution (ink profile) is required transversely to the printing direction of the offset printing press in order to achieve a good printed product. The inking unit may therefore comprise an ink-metering apparatus, which permits the zonal setting of an ink profile. There results a corresponding ink-film thickness as a function of the setting of the individual zones. The ink is supplied by means of an ink-duct roller from an ink duct.

The printer has the task of making the respective zonally required setting of the ink-metering apparatus depending on 25 the ink demand of the image. Prior to actual printing, moreover, there is a so-called "ink running-in", in which the aforementioned ink film is built up inside the inking unit.

According to the prior art, movable applicator rollers assumed a disengaged position with respect to the printing forme 30 during "ink running-in", with the result that there was not ee yet any inking of the printing forme.

se:* During "ink running-in", apart from being distributed in the circumferential direction, the ink is also distributed laterally by traversing distributor rollers. Apart from the 35 known advantages of lateral distribution without engaged applicator rollers, the ink profile, built up by the ink-metering apparatus during "ink running-in", is evened out again to a certain extent, with the result that, at the start 39 s -2of printing, the ink profile is not immediately available to the desired extent. In order to remedy this disadvantage, it has been proposed that the rotating applicator rollers of inking unit and damping unit should be brought into a position of engagement with respect to the printing forme. This means that the image on the printing plate has such a supporting effect on the distribution of the ink that there results an ink profile which corresponds very largely to the image. The ink profile that has been set zonally at the ink-metering apparatus is built up again by the interaction and reaction of the applicator rollers and printing forme. This measure made it possible greatly to reduce the hitherto incurred quantity of waste. An ink profile suitable for the production run is quickly achieved.

15 It has become apparent that, with the applicator rollers engaged and with the ink-metering apparatus set for the desired production-run ink profile, there results, as a result of "ink running-in", an ink distribution in the inking unit that overdraws the desired ink profile, i.e. there results, for example, a higher or lower maximum/minimum of the zonal ink-film thickness. In particular, this effect of overdrawing occurs with images in which there are great differences in the zonal ink-area density. In order to limit this effect in marginal cases, the practice hitherto has been for the printer to supply ink manually to the relevant zonal regions by means of a palette knife, in order at least to be able to start the printing process and not to have excessive problems during the production process. However, the ink-water equilibrium in non-printing image parts is substantially disrupted.

The objcct of the invention is to achieve ac quickly a-; possible an ink profile suitable for the productionruna and to prevent further printing of waste.

According to the nt invention there is provided in a first step, in the process as already described, the suppl the ink quantity is controlled in such a manner that 39 -3- 4 It would be advantageous to achieve as quickly as possible an ink profile suitable for the production run and to reduce the printing of waste.

According to an aspect of this invention there is provided a method of setting up a production-run ink profile on an offset printing press having a damping unit and an inking unit and a printing forme or plate cylinder with printing plate mounted thereto, the damping and inking units having applicator rollers which are moved into engagement with the printing forme, and the inking unit having ink-metering apparatus for establishing a desired production run ink profile, the method including: a first step of controlling the quantity of ink supplied by the ink metering apparatus such that it produces an ink profile that is substantially inverse to or phase-opposed to the production-run ink profile, and a second step of controlling the quantity of ink supplied by the ink metering apparatus such that it produces an ink profile substantially corresponding to the production-run ink profile.

The above-described overdrawing of the ink profile is purposely utilized for the invention. This is because, surprisingly, it has become apparent that the production-run state is achieved considerably faster and 25 without further printing of waste if, first of all, there 9:06 is an inverse setting of the ink-metering apparatus and then the ink-metering elements are adjusted, during "ink running-in", to the optimal production-run state. The result is an ink/damping-solution equilibrium that is S 30 optimal for the production run. An ink gradient corresponding to reality is built up throughout the entire inking unit without using the conventional preliminary !.:"waste" run, i.e. without conveying sheets beforehand •.through the printing press and printing them. This process for the fast achieving of the optimal production-run state is used at the start of printing, after interruptions in the printing process, such as when starting afresh each day, after washing the rubber blanket 39 or after a change of printing job.

5 It is preferred that the con- ol of the quantity of ink supplied in the second step is such that it simultaneously adapts zone by zone 1o the desired production-run ink profile, irrespective of the gap between the substantially inverse or phase-opposed ink profile and the production-run ink profile.

Since, in the range of extreme values of the inverse ink profile and the actually desired ink profile, the time required for setting the ink-metering elements is greater than in the range of the turning points (medium presetting of the zones of a printing unit), a control is provided which equalizes the time differences in such a manner that there results as fast an adjustment as possible to the optimal state.

It is preferred that during the setting up of the production-run in profile, the quantity of damping solution is reduced by comparison with the quantity thereof which is supplied during the production run.

It may be possible, according to the invention, to control the damping-unit control in coordination with the ink-metering apparatus in coordination with the applicator rollers and the intermediate roller in such a manner that optimal production-run states are achieved.

According to a further preferred embodiment of the 25 invention, it is provided that the inverse ink profile is e o set through the intermediary of an electronic computing and control apparatus.

For example, the optimal production-run ink profile is measured by means of a plate reader, which determines S 30 the area coverages for each zone; then, on the basis of this date, the suitable inverse ink profile is determined and then the ink-metering apparatus is set accordingly.

The production-run profile can also be preset with a light pen or keyboard and can then be executed accordingly with 35 the computing apparatus according to the invention.

According to another aspect of this invention there is provided a method for establishing a production ink

S

zone profile in an offset printing press producing 39 successive prints of an image formed on a printing plate, 6 the printing press including a plate cylinder for receiving thereon a printing plate, an ink reservoir for supplying ink, an ink roller train inclluding at least one ink applicator roller for transferring at least portion of the ink supplied by the ink reservoir to the printing plate, an ink metering apparatus for metering ink from the ink reservoir to the ink roller train, a wetting agent reservoir for supplying wetting agent, a wetting aqent roller train including at least one wetting agent applicator roller for transferring at least a portion of the wetting agent supplied by the wetting agent reservoir to the printing plate, the ink metering apparatus including a plurality of individually adjustable ink metering devices for supplying ink to the ink roller train, each ink metering device defining a corresponding ink zone of the printing press, the amount of ink metered into said ink zones defining the ink zone profile of the printing press, the method including the steps of: determining from the image provided on the printing plate, a production ink zone flow from each of the plurality of individual adjustable ink metering devices which produces a production ink zone profile appropriate for the printing of the image provided on the printing plate onto the printing medium; determining an average production ink zone flow for the ink metering devices; osetting the plurality of individually adjustable ink .metering devices to produce initial inverted ink zone flows, said initial inverted ink zone flows being a mirror 30 image of said production ink zone flows, said mirror image being reflected about said average production ink zone flow; operating the printing press with the plurality of individually adjustable ink metering devices set to produce said initial inverted ink zone flows, and with the at least one ink applicator roller and the at least one wetting agent applicator roller in contact with the oo printing plate; e 39 setting the plurality of individually adjustable ink

AM

0L of 7 metering devices to produce said production ink zone flows; operating the printing press with the plurality of individually adjustable ink metering devices set to produce said production ink zone flows, and with the at least one ink applicator roller and the at least one wetting agent applicator roller in contact with the printing plate.

Thus the invention facilitates the obtaining of an optimal production-run state as quickly as possible, with there being only a minor amount of printing waste. The use of the inverse ink profile results in an ideal ink-water equilibrium. Smearing and emulsification are prevented. In particular, the production process for larger printing jobs is optimally prepared.

A method of setting up a production-run ink profile in accordance with this invention may manifest itself in a variety forms. One particular form is described in detail below, purely by way of example, with reference to the following drawings. The generality of the preceding statements is not to be narrowed down or limited by the folloting specific description. In the drawings: Fig. 1 shows a graph of an ink profile; Fig. 2 shows the representation of the different ink quantities; and Fig. 3 shows a graph of the ink-film thickness 0:0 during "ink running-in".

Fig. 1 shows a graph in which the ink coating thickness for each of the zones Z of the ink dosing apparatus F z is plotted against the zones Z. There is shown a profile of the ink layer thickness, whereby the ink stripe width set by the ink ductor roller was kept constant at .The ink quantity or flow V which is plotted in

F

S. Fig. 2 as the solid line curve over the zones Z S 35 corresponds approximately to this profile. The ink quantity VF is proportional to the product of the ink Sductor stroke F and the ink zone aperture F The cvD V curve corresponds to the desired quantity of ink for the 39 production run status. The curve, for example, has two 8 maxima and one minimum. A horizontal line which corresponds to the average ink consumption over all of the ink zones of the printing unit runs through the turning points between the extremes. If, however, the applicator rollers are in contact with the printing plate (for example, in accordance with the process disclo,'ed in the above-noted parent application), and the ink dosing apparatus were to be set according to the solid curve (corresponding to the production run process) for the zonal ink quantity, there would be initially an overdosing or an underdosing, as described above. Such overdosing and/or underdosing is illustrated schematically by the dotted curve in Fig. 2. The present invention takes advantage of this effect, theroby achieving a surprisingly positive result. First, the ink dosing apparatus (i.e.

the ink feed to the zones Z) is set so that a reverse quantitative ink distribution is achieved, as illustrated by the dashed curve in Fig. 2, and then this setting is modified so that the broken-line curve is fitted to the curve represented by the solid line to the optimal production run status. In this manner an optimal ink-water equilibrium is achieved. The approximation (or fitting) of the reverse curve to the desired curve is indicated by arrows in Fig. 2.

Fig. 3 shows the average value of the full tone density Dv as a function of the sheet number- Bz The V.0 overinking and underinking, respectively. The setting is optimal when it is between the horizontal lines a and b, as shown in Curve I. It is clearly apparent that with the process according to the invention, the dotted Curve I tends toward the final value after a relatively few sheets, while, on the other hand, the solid Curve II, which corresponds to the setting of the ink layer density without the reverse control setting according to the present invention, achieves a comparably optimal condition only at a later time. Thus, the numbers of waste sheets which have to be printed (approximately 100-300) using the 39 processes of the prior art are no longer necessary), and 9 the production process can be started after a very small number of waste sheets (approximately 10 to 50 sheets).

In other words, the present invention utilizes, to good effect, the phenomenon described above, wherein, when the applicator rollers of the inking and wetting mechanisms are maintained in contact with the plate cylinder during the so-called ink introduction period (as disclosed in the above-noted parent application), there is a tendency toward an overshoot or undershoot, respectively, in the areas of maximum and minimum ink thickness. This phenomenon is generally most apparent when the production printing run involves an image having areas requiring substantially differing thicknesses (or flows) of ink, for example, an image having one area requiring relatively dense ink coverage and another area requiring relatively sparse ink coverage.

Referring again to Fig. 2, the ink flow VF which is determined to be appropriate for a particular image provided on a printing plate is there shown by a solid line. Such appropriate ink zone flows may be derived from the use of a printing plate image reader such as the one described in the publication entitled "Heidelberg CPC", published by Heidelberger Druckmaschinen Ag, D-6900 Heidelberg (Publication No. 4,681,455 entitled "Method of Determining the Area of Coverage of J Printed Original or a Printing Plate for Printing Presses", equivalent to published European Patert Appln. No. 0 095 606 AZ.

However, due to the above-noted "generalizing" effect, the actual achieved flows may overshoot (or undershoot) the derived appropriate flows in the areas of maximum minimum) flow, as shown by the dotted line in Fig. 2, particularly when -the method of the parent application the method for maintaining the inking 0.0 and wetting applicator rollers in contact with the plate cylinder during the ink introduction period) is adopted.

The present invention is directed to the reduction and/or S* elimination of this overshoot/undershoot phenomenon.

Referring still to Fig. 2, it will be seen that the 39 determined appropriate ink zone flows generally form a 10 graphical production (or appropriate) flow line the solid line depicted in Fig. 15) across the ink zones Z=l, This production ink zone flow line has at least one area of maximum flow a peak) and at least one area of minimum flow a valley or trough). In general, the present invention is directed to first determining an intermediate ink flow level, the intermediate ink flow level being within the range defined by the maximum and minimum production ink zone flows det-nmined as being appropriate for the particular image provided on the printing plate. In the preferred embodiment, the intermediate ink flow level chosen is the arithmetic average of all of the determined appropriate ink zone flows for the ink zones However, it is believed that intermediate ink flows other than the arithmetic average may be appropriate.

Next, the production ink zone flow line is inverted about the chosen intermediate ink flow level, to thereby produce an inverted ink zone flow line, such that peaks of the production ink zone flow line become troughs of the inverted ink zone line, and such that troughs of the production ink zone flow line become peaks of the inverted ink zone flow line. Alternatively, this may be viewed as forming a reflected mirror image of the production ink 25 zone flow line about the chosen intermediate ink flow .:eo level to form the inverted ink zone flow line. Still see* g further, a similar effect can be achieved by determining, :'"for each ink zone Z=l, 2. 8, a signed difference or -times a scalar value) between the production ink zone flow and the chosen intermediate ink zone flow, multiplying each signed difference by and adding the rsults to the chosen intermediate ink flow to produce the inverted ink zone flows.

The particular ink zone profile (and/or ink flow 35 VF) which is appropriate for a particular image provided on a printing plate may be determined using a printing plate image reader such as the one described in the publication entitled "Heidelberg CPC" referenced above.

3 9 Typically, such a printing plate image reader will employ 11 a programmable CPU device. The same, or a similar, CPU device may also be used for controlling some (or nearly all) of the steps described above of determining, based upon the image provided on the printing plate, a production ink zone profile appropriate for the printing of the image provided on the printing plate during the production printing run; determining, for each of the plurality of individually adjustable ink metering devices, a production ink zone flow to produce the production ink zone profile in the printing press during the production printing; determining an ink flow level within the range of the determined production ink zone flows; and inverting the production ink zone flow about the determined ink flow level to thereby produce an inverted ink zone flow, such that peaks of the production ink zone flow become troughs of the inverted ink zone flow, and such that troughs of the production ink zone flow become peaks of the inverted ink zone flow.

In particular, such a programmable CPU device is particularly well adapted for performing at least one of the steps of determining an ink flow level within the range of the determined production ink zone flows id inverting the production ink zone flows about the determined ink flow level to thereby produce inverted ink zone flows, such that peaks of the production ink zone flows become troughs of the inverted ink zone flows, ind such that troughs of the production ink zone flows become peaks of the inverted ink zone flows.

An advantage of this invention is that it is able to 30 provide a method for setting up a production-run ink profile on an offset printing press which results in only a very small amount of waste at the commencement of the printing run.

o 8984e

Claims

1. A method of setting up production-run ink profile on an offset printing press ving a damping unit and an inking unit and a printing forme, the damping and inking units having applicator rollers which are moved into engagement with the printing forme, and the inking unit having ink-metering apparatus for establishing a desired production-run ink profile, the method including: a first step of controlling the quantity of ink supplied by the ink metering apparatus such that it produces an ink profile that is substantially inverse to or phase-opposed to the production-run ink profile, and a second step of -ontrolling the quantity of ink supplied by the ink metering apparatus such that it produces an ink profile substantially corresponding to the production-run ink profile.

2. A method according to Claim 1, wherein the control of the quantity of ink supplied in the second step is such that it simultaneously adapts zone by zone to the desired production-run ink profile, irrespective of the gap between the substantially inverse or phase-opposed ink profile and the production-run ink profile.

3. A method according to Claim 1 or Claim 2, wherein during the setting up of the production-run ink profile, the quantity of damping solution is reduced by comparison with the quantity thereof which is supplied during the production run.

4. A method according to any one of the preceding claims, wherein the substantially inverse or phase-opposed 30 ink profile is set through the intermediary of an electronic computing and control apparatus.

A method for establishing a production ink zone profile in an offset printing press producing successive prints of an image formed on a printing plate, the printing press including a plate cylinder for receiving thereon a printing plate, an ink reservoir for supplying ink, an ink roller train inclluding at least one ink applicator roller for transferring at least a portion T39 of the ink supplied by the ink reservoir to the printing 13 plate, an ink metering apparatus for metering ink from the ink reservoir to the ink roller train, a wetting agent reservoir for supplying wetting agent, a wetting agent roller train including at least one wetting agent applicator roller for transferring at least a portion of the wetting agent supplied by the wetting agent reservoir to the printing plate, the ink metering apparatus including a plurality of individually adjustable ink metering devices for supplying ink to the ink roller train, each ink metering device defining a corresponding ink zone of the printing press, the amount of ink metered into said ink zones defining the ink zone profile of the printing press, the method including the steps of: determining from the image provided on the printing plate, a production ink zone flow from each of the plurality of individual adjustable ink metering devices which produces a production ink zone profile appropriate for the printing of the image provided on the printing plate onto the printing medium; determining an average production ink zone flow for the ink metering devices; setting the plurality of individually adjustable ink metering devices to produce initial inverted ink zone flows, said initial inverted ink zone flows being a mirror 25 image of said production ink zone flows, said mirror image 9**9 being reflected about said average production- ink zone Peet flow; operating the printing press with the plurality of individually adjustable ink metering devices set to produce said initial inverted ink zone flows, and with the "at least one ink applicator roller and the at least one wetting agent applicator roller in contact with the "printing plate; setting the plurality of individually adjustable ink metering devices to produce said production ink zone flows; operating the printing press with the plurality of individually adjustable ink metering devices set to 0: produce said production ink zone flows, and with the at 39 least one ink applicator roller and the at least one 14 wetting agent applicator roller in contact with the printing plate.

6. A method for establishing a production ink zone profile according to Claim 5, wherein said step of determining an average production ink zone flow, comprises determining the substantial arithmetic average of production ink zone flows for the ink metering devices.

7. A method substantially as herein described with reference to the accompanying drawings. DATED 25 January 1995 PHILLIPS ORMONDE FITZPATRICK Attorneys for: HEIDELBERGER DRUCKMASCHINEN AKTIENGESELLSCHAFT *9 S s.. S. 8984e ABSTRACT The invention relates to a process for setting a production-run ink profile of an offset printing press. First of all, an ink profile is set that is inverse to the desired ink profile and then said inverse ink profile is adjusted to the actually desired ink profile. to a 39 S *0 39