DE19517154B4 - Method for obtaining machine-dependent default values for loading a roller inking unit prior to printing - Google Patents

Abstract

Method for obtaining machine-dependent default values for loading a roller inking unit of a printing press before printing, comprising the following features:
a) Several tests are carried out in each case with loading and temporally separate unloading of the inking unit, using a test form with a defined printing area and at least one printing material-ink combination,
b) for each test, the inking unit is first loaded without being printed with an associated, defined color volume of the color of the selected substrate / ink combination, the inking zones being set in a defined ratio to the printing area of the test form,
c) each loading operation is followed by an unloading process wherein a predetermined number of test sheets are printed from the substrate of the selected substrate / ink combination with the test form and the ink feed is turned off,
d) the color density on the printed test sheet is determined to form charge volume dependent color density characteristics, and
e) the color density characteristics are used to formulate default values for the before ...

Description

The The invention relates to a method for obtaining machine-dependent default values for the store a roller inking unit of a printing press before the start of printing.

In In practice, the presetting of the color flow and in particular the determination of the amount of paint that is allowed to run in, that is with the the inking system is still loaded manually and empirically. This leads however only to a rough approximation to the actual required Values, allowing an adjustment while the already starting printing operation is required. The episode this is a comparatively large amount of waste paper.

In DD-Z: Paper and Printing 31 (1982) 3, Printing and Processing, Pp. 37-40 is a method for mathematical pre-adjustment of the color dosage described on printing machines. A calculation of the in the usually colorless inking unit shrinking in amount of ink proposed. Clear calculation rules are not specified. The for The equations addressed in the calculation are based on the Assumption of a color layer model in the printing unit. The in such However, experience has shown that results can not be achieved exactly enough, so that subsequent Manual corrections are required. It would also be extensive and complicated Arithmetic operations for The practical printing operation is not easy and clear enough.

In DE-Z: Polygraph 6-93, Pp. 47-50 is a method for optimizing so-called alignment processes in offset printing described. An adjustment process begins when in the event of a deviation the print result of a desired target color strength a change the ink supply to the inking unit is made and ends when the Target color strength is reached. Such matching processes take place during the current printing operation, that is, while ink is added to the inking unit. and dissipated therefrom is and therefore take a relatively long time. To shorten such Angleichvorgänge Here is a so-called overdrive suggested their height and duration, that is their intensity, is calculated by means of a computer simulation, based on a model based on the color flow in the printing operation. For the amount of paint required for running in this results in no instruction.

The Object of the present invention is the above-mentioned method so that after only a few cylinder revolutions after Printing starts a stable color flow in the correct intensity arises.

These The object is solved by the features of claim 1.

below the invention will be closer described.

The Color zones of a roller inking system, the data of a printing plate scanner According to the zonal color needs opened (0 to 100%). In combination this is the Farbduktorgeschwindikeit, according to the fertility curves the default paper / color combination, set. As a general rule applies: high color requirement for absorbent, rough paper and a low yield ink. The Procedure how to find the right settings of the ductor are described in the following example. In the conventional Offset printing is the amount of fountain solution according to the promoted Color amount set. The possible Methods are described in more detail in the following example. Will a roller inking a high pressure plate or a dry offset plate colored (eg Toray plate), this eliminates the Adjustment at the dampening unit.

According to the invention is a to be adjusted inking unit in terms of its typical properties to test to determine specific characteristics and key figures. For this Test case - im Contrary to the usual Operating mode - is loading and unloading the inking unit as one from the other independent To look at the process. Loading and unloading become separate from each other and tested consecutively separately, which is described below a method example is described in detail.

The The inking system, after the ink zones, the printing surfaces of the Correspondingly, with a definable pressure plate Number of machine or lift strokes loaded (running in from Color) without being printed becomes. Thus, according to the zonal color requirement, a defined color level in the roller inking system.

If a color profile in the inking unit consists of a previous print job, erfindungsge mäß ensured that after the end of this print job still some sheet, z. B. 10 sheets are printed under the following conditions: All ink zones are closed, the ink lifter continues to run, so that, as described above, promotes color in the ink fountain. In addition, the dampening is switched off during offset printing. As a result, it comes to toning, ie the entire printing plate colors. The result is a very strong flow of ink from the inking unit, which quickly degrades the existing color profile. In dry offset or high pressure no dampening system exists. With these methods, it takes a little longer, about 20 to 30 sheets, until the existing color profile without ink supply is sufficiently degraded. In sheetfed printing, this "discontinued waste" can be presented as a printed waste sheet at the end of the paper stack to be printed, so that no "white waste" is consumed.

• a) Laden des Farbwerks und
• b) Entladen des Farbwerks separat zu betrachten sind. Als Testform wird eine Volltonfläche verwendet

An embodiment of the invention will be described below to systematically check the correct setting and the characteristics of the ink zones and the ink ductor and to represent the absence of side effects and the color cross-transport in the inking unit:
Important and essential is that the operations

• a) loading the inking unit and
• b) unloading the inking unit are to be considered separately. The test form used is a solid surface

It is assumed that a practice-usual ductor and ink zone setting, z. B. Color zones = 50% (Z ₀ = 50), Farbduktor 50% (D ₀ = 50). For loading, the inking unit runs a defined number of lifter cycles with the given zone and director settings without printing (according to the following table 10 ... 80 cycles).

To The store takes a defined number of turns to print can be (according to the following table uniformly 10 bars). This number should be recorded as idle. After each load and idle a given number of sheets is printed (according to the following Table 10 ... 100 * printed sheet).

• – Automatisches Protokoll
• – Inkjet Marking auf jedem Bogen
• – Unterstützung der Dokumentation durch Video-Camrecorder.

Serie A Versuchs-Nr. a) Laden Hebertakte Leerlauf Takte b) Entladen Druckbogen 1. 10 10 10 2. 20 10 10 3. 40 10 10 4. 80 10 100*

• * (oder bis die Farbdichte ein Minimum von
• D = 0,50 unterschreitet.

To monitor and register the experiments, the following measures are appropriate:

• - Automatic log
• - Inkjet marking on each sheet
• - Support documentation through video camcorder.

Series A Experiment no. a) Loading lifters Idle cycles b) unloading sheet 1. 10 10 10 Second 20 10 10 Third 40 10 10 4th 80 10 100 *

• * (or until the color density is a minimum of
• D = 0.50 below.

Series B to E

Same experiments, for example with the following settings on the ink zones and on the ink ductor: Z = Z 0 / 2 and Z = 2 Z 0 D = D 0 / 2 and D = 2 D 0

It depends on of printing press type, maybe better the points 10% -90% - at Z and D (or similar Values) to the function of the promoted Color quantity f = f (Z, D) to determine.

The densitometric evaluation of the printed sheets (Scanning Densitometer use, with data evaluator) shows:

Charge and discharge

Out the discharge curves is the discharge characteristic of the inking unit and to represent the charging characteristics by the different charge, z. B. as Farbdichteverlauf, averaged over the sheet width in dependence from the printed number of sheets.

Constant quality of the ink zones

By zone-wise evaluation, the synchronous quality of the zones can be determined.

Test for side effect freedom and cross transport the color

Same Test form but adjust ink zones alternately to Z = 10, 90 ... 10, 90%.

series print like A ... E, then color zones in opposite directions to Z = 90, Set 10 ... 90, 10% and print series again, like A ... E.

Variant: After running in more than 10 empty cycles !! Evaluation like above. The profile of the zones is clearly visible and is arched to arc more indistinct, because on the one hand no color nachfließt and on the other hand the color is transversely transported by the trituration.

Adjustment of the dampening unit

Of the Humidity ductor is adjusted proportionally to the ink fountain roller, whereby the dampening solution requirement of the printing ink is added as a correction factor.

Measuring programs and evaluation programs

• – Ladung und Entladung
• – Gleichlaufgüte der Farbzonen
• – Nebenwirkungsfreiheit und Quertransport der Farbe.

Different measuring and evaluation programs are provided,

• - Charge and discharge
• - Consistent quality of the ink zones
• - Side effect freedom and cross transport of the color.

Before the measuring program carried out is the scanning densitometer and data storage as well to check the data processing!

A clear synchronization of the measured values on the ink fountain keys through the beginning and end D <D _max must be ensured.

Evaluation of the charge and discharge

Color density measurements should be made on all 10 printed sheets of a series parallel to the gripper with as many measurements as possible (approximately every 5 mm) and stored on a floppy disk. Each density reading is: D _ij

3 : Definition of arc width i = 1 ... m and of arc number j = 1 ... n

The mean value per arc j over all color zones is:

The deviation of the color density in each zone from the mean of the sheet is: .DELTA.D ij = D ij - D j

The associated standard deviation is calculated as follows: STDV (.DELTA.D i ) = STDV (ΔD ij - D j ).

Because of the lack of ink supply, the average color density decreases from sheet to sheet D _j .

These Determining this mean value is important, because only so the values the successive sheets are compared functionally can.

The function D _j = f (j) is an illustration of the discharge curve.

Out the functions can Codes, comparable to the time constants for RC elements electrical networks are formed.

Evaluation of the synchronous quality of the ink zones

mit der dazugehörigen Standardabweichung: STDV(D_i)For the targeted representation of the differences of individual ink zones, proceed as follows:
The mean value per color zone i over all sheets is:

with the associated standard deviation: STDV (D _i )

Because of the color density decreasing from bow to bow is the standard deviation Naturally greater than in the previous evaluation.

Will now be the mean D _{i applied} over all i, then shows which color zone i promotes more or less color than the average.

Side effect freedom and cross transport

Just if the test prints described above with alternately open Color zones performed the corresponding evaluation is also possible. This is the color density at the gripper edge, as well as for the evaluations described above to eat.

at The evaluation programs become the zones with a lot and little amount of paint considered separately.

Claims (15)

Method for obtaining machine-dependent default values for the Loading a roller inking unit of a printing machine before printing starts, contains the following features: a) There are several tests each with loading and temporally separated Discharging the inking performed, wherein a test form with a defined printing area and at least one printing ink-color combination use Find, b) for every test is the inking first without printing with an assigned, defined color volume the color of the selected Substrate-color combination charged, the ink zones in a defined ratio to the printing surfaces the test form are set, c) follows each load a discharge process, wherein a predetermined number of test sheets from the substrate of the selected Printing material-color combination is printed with the test form, and with the ink supply turned off, d) the color density The printed test sheet is used to form charge density dependent color density characteristics determined and e) the color density characteristics become the formation of default values for that tested before starting the actual printing with the tested substrate-ink combination Ink supply to be supplied Loading volume used. Method according to claim 1, characterized in that that as a test form a solid surface is provided. Method according to one of the preceding claims, characterized characterized in that when using a solid surface in Loading assumed a ductor and ink zone setting of 50% becomes. Method according to one of the preceding claims, characterized characterized in that when loading the rotational speed of the ductor dependent on is adjusted by the substrate / color combination used. Method according to one of the preceding claims, characterized characterized in that tests with different duct speed and / or different lifter cycles are performed, the adjustment the color zones is kept constant. Method according to one of the preceding claims, characterized characterized in that the ink volume supplied to the inking unit at each test is defined by the number of lifters. Method according to one of the preceding claims, characterized characterized in that for each test between loading and unloading a defined number of idle revolutions is provided. Method according to one of the preceding claims, characterized characterized in that when unloading only printed so many test sheets until the color density is a predetermined minimum of D = 0.5 reached. Method according to one of the preceding claims, characterized characterized in that the color density of each test sheet as Mean over all color zones is determined. Method according to one of the preceding claims, characterized characterized in that the color density on the printed test sheet determined by densitometric measurement or comparison with a sample pressure strip becomes. Method according to one of the preceding claims, characterized characterized in that for determining the synchronization quality of all Color zones (same delivery volume at the same setting) for each color zone averages over all test sheets of a test be formed. Method according to one of the preceding claims, characterized characterized in that in tests with wet offset machines, the dampening ductor is set proportional to the Farbduktor. Method according to one of the preceding claims, characterized characterized in that for determining the transverse transport of the color Tests with alternately open and closed color zones are performed. Method according to one of the preceding claims, characterized characterized in that the the inking unit before the beginning of the actual Pressure to be supplied Loading volume at the zonal ink needs opened accordingly Color zones determined by the charging time or the number of charges becomes. Method according to one of the preceding claims, characterized marked that for default values assigned to each machine type are determined.