DE10225824A1 - Method for determining a course for the tension drop of a web and method for adjusting the tension - Google Patents

Abstract

The invention relates to a method for determining the course of a drop in tension to be expected for a strip in a printing unit. According to the invention, essentially the same tensions are first adjusted without ink and without a humidifying agent, in a printing position in front of and behind the printing unit; ink and optionally a humidifying agent are then added; a value for the tension behind the printing unit is measured once essentially stationary conditions have been achieved; and on the basis of at least one of the pairs obtained in this way for the tension values, a fictitious course of the drop in tension caused by the humidity in the printing unit is established according to a tension, by means of linearisation of a tension-extension dependence, at least in sections. Said course can be used in a method for adjusting tension in front of and/or behind the printing unit.

Description

The invention relates to methods to determine a history for the voltage drop of a web and a method of adjustment the tension according to the generic term of claims 1 and 10.

Through the DE 28 40 630 A1 a device is known by means of which a stress-strain characteristic for a band-shaped material can be determined.

In the EP 07 37 638 A1 A method for determining and regulating an elongation of a running material web is known, wherein the elongation is determined on the basis of two measured speeds and is regulated to a desired elongation via the web tension.

The invention is based on the object Method for determining a curve for the voltage drop of a To create web and a method of adjusting the tension.

The object is achieved by the Features of claims 1 and 10 solved.

The achievable with the invention The main advantages are that effects of a specific Paper characteristics can be determined with simple means, and on Because of this, a secure setting of the printing press is guaranteed is.

An elaborate determination of a Stress-strain characteristics field under laboratory conditions can be omitted. In addition, such a characteristic field does not yet provide any information about the in the press actually expected moisture penetration, so that these are also measured would have to sure statements about to be able to meet the expected rail transport.

It is of great advantage that after Determination of the production-specific paper characteristics Web tensions are adjustable so that on one side a run of the web after the printing unit due to too low tension, and on the other hand avoided a web break caused by excessive tension can be.

Embodiments of the invention are shown in the drawings and are described in more detail below.

Show it:

1 a schematic representation of a printing unit with measuring points;

2 a stress-strain characteristic of a paper web;

3 a first embodiment for the method for determining a characteristic;

4 a second embodiment for the method for determining a characteristic.

A processing machine, e.g. B. a printing, in particular web-fed rotary printing press, has at least one processing stage 01 , e.g. B. a printing unit 01 on. The printing unit 01 which of a train 02 , e.g. B. a paper web 01 , is run through. The printing unit 01 is in 1 designed as a so-called aft tower, which several, z. B. four, as double printing units 03 executed printing units 03 having. But you can also like in 1 schematically represented as a printing unit comprising two nine-cylinder or two ten-cylinder systems 01 each with a satellite cylinder 04 adjustable printing units 06 be executed.

The train 02 runs from a reel changer 07 via at least one train group 08 and one measuring point 09 for measuring a tension S1 of the web 02 before making a first of several pressure points 11 passes. After the last printing point 11 it passes a second measuring point 12 for measuring a tension S2 of the web 02 and a second train group 13 , before passing through a third train group, if necessary, via other aggregates, not shown 14 a former 16 is fed. In an advantageous embodiment, the printing press has between roll changers 07 and first train group 08 a single feed mechanism 17 by means of which the voltage S1 can be changed.

When going through the printing units 03 ; 06 the web is in print-on position during production 02 at least by applying color, and especially in wet offset printing by dampening solution. As is known, their properties change, in particular the stress-strain characteristics. In 2 is an example of a specific path 01 (Grade, thickness, surface quality etc.) the dependence of an elongation ε (in%) on a web tension S once in the dry state and once with a water content of 10%.

Depending on the number of printing points passed through during production and the respective printing density, ie the amount of onto the web 02 applied paint and / or dampening solution, is now the web 02 on its way through the printing unit 01 more or less moistened. In addition, a temporal penetration behavior also plays a role, which in turn depends on the respective paper, but also on a throughput time, ie on the speed.

For the quality of the printed products, especially when in front of the former 16 several lanes 01 are brought together is a section length that is as constant as possible, ie an essentially constant stretch of the web 02 between printing unit 01 and folding former 16 , desirable. For this the second train group 13 regulated for example with regard to its speed. The regulation can e.g. B. to a constant speed or to a certain relative speed to another train group 08 ; 14 be regulated. In this context, the term rotational speed is to be understood as meaning a regulation with regard to a (relative) angular position or an angular velocity.

Using the example of 2 would now wet the previously dry web 02 due to the pressure unit to 10% water content, a voltage drop ΔS behind the pressure unit 01 from approx. 50 daN / m to approx. 28 daN / m if the web is stretched 02 is kept constant. With a different type of paper for the web 02 , a different strength, or a different humidification would lead to completely different results.

For setting and controlling the web tension, it is essential that a lower limit for the tension S, z. B. 12 daN / m, in particular 8 daN / m, is not fallen below, otherwise the web 02 can run sideways on their way. To minimize the risk of a web break, an upper limit for the tension S, z. B. 55 daN / m, in particular 60 daN / m, are not exceeded. Another criterion is that the levels of several webs brought together in front of the former 16 02 must be graded in their voltage S to each other.

The printer or a control or Control device must now when setting the voltages S all the criteria mentioned for the most varied Paper types and / or production conditions.

The following procedure gives that Printer or a control or regulating device a simple, inexpensive and safe practice at hand to get a characteristic to generate and a corresponding adjustment of the voltages S; S1; S2.

Should be a train 02 unknown quality or / and a new production with a new one, related to this web 02 still unknown web run, or / and with a different number of printing points or / and with a very different printing density, so in the run-up to this production, a characteristic specific to this paper type and / or production is first created, which is initially carried out manually by the printer Form is described.

A diagram shows on one of its axes, here the abscissa, in linear plotting the web tension S in the area of interest, e.g. B. from 0 to 60 daN / m. The other axis, here the ordinate, does not have to have a predetermined division and does not denote a "real" size. The ordinate can be in a to 2 parallel viewing represent something like an unscaled strain ε *. The diagram also has a straight line G1 through the origin. In analogy to 2 The straight line G1 corresponds to the "dry" curve idealized as a linear, but with an essentially arbitrary slope. However, in order to obtain a reasonable spread of the diagram to be completed later, the straight line G1 is such that it is aligned with the axis for the tension S, here the abscissa, forms an angle of 25 to 55 °, in particular 35 to 50 °.

The most unfavorable production conditions for a railway 02 to achieve z. B. a production with all pressure points in the web 11 , here a 4/4 production, where the printing units 03 ; 06 possibly also with full-page images in multi-color printing, here four-color printing.

The printing machine is now brought to a speed between zero and the intended production speed. Advantageous because for the train 02 most disadvantageously, the speed is around 5,000 to 15,000 m / h, in particular 8,000 to 12,000 m / h, which in the case of double-sized cylinders, ie for cylinders with two printed images on their circumference, roughly corresponds to the speed in the unit cylinder revolutions / h corresponds.

The press is started up with the printing units in the print-on position 03 ; 06 , but temporarily without paint and water.

In the simplest case, the characteristic is based on only one measuring point generated. For this purpose, the voltage S1 in front of the printing unit 01 is raised a certain voltage value x1, e.g. B. regulated to 50 daN / m. Will only be a measuring point approached, this is the measuring point advantageously in the upper third of the candidate for production Voltage range, e.g. B. from 40 to 60 daN / m.

By means of the train group 13 is now essentially the same voltage value, z. B. 50 daN / m, set for the voltage S2. Then the ink and water supply is activated and, in a largely stationary state, the voltage value x2 that is set for the voltage S2 at the measuring point 12 decreased.

Preferably there are four double or eight single pressure points 03 ; 06 between paint and water and at least the measured value recording 15 , especially 20 seconds.

At the level of the point P1 of the straight line G1 belonging to the set voltage value x1, the determined voltage value x2 is now entered as point P2 parallel to the abscissa. In the version with only one measuring point, a second straight line G2 is now laid through point P2 and the origin. The straight line G2 is idealized with the curve "10% water" 2 comparable.

In a more precise implementation of the method, as in 3 shown in order to determine the replacement characteristics, several measuring points for the voltage S1, z. B. approached three voltage values x1 such as at 30, at 40 and at 50 daN / m. The measuring points preferably arrive in the order from smaller voltage values x1 to larger ones hazards. The ink and dampening solution can be switched off between the individual measuring points in order to adjust the two voltages S1 and S2 to the new voltage value x1. However, the latter can also be omitted if it can be assumed that the relative basic settings of S1 and S2 for the dry state will not change if S1 is increased. The latter is usually the case. The printing machine is therefore on the above-mentioned speed and the printing units 03 ; 06 brought into pressure-on position without water and paint. Before and after the printing unit 01 a voltage value x1 of z. B. 30 daN / m set. After ink and water come on, the voltage S2 is in the largely stationary state behind the printing unit 01 read. The z. B. after 20 s voltage value x2, here z. B. 16 daN / m, is entered at the level of the point P1 belonging to the set voltage value x1 of the straight line G1 parallel to the abscissa as point P2.

Then, e.g. B. by means of the feed mechanism, the voltage S1 before the printing unit 01 increased to 40 daN / m, again z. B. waited 20 s, the voltage S2 after the printing unit 01 read and entered in the diagram at the level of point P1 of line G1 belonging to the set voltage value 40 daN / m parallel to the abscissa as point P2, here at approx. 20 daN / m. Accordingly, the method z. B. for x1 = 50 daN / m and possibly further measuring points continued.

Through the zero point and the points P2 is now the line G2. Is especially in the upper area of the voltage values x2 a point P2 to the left of one through the remaining points P2 given straight line G2, the straight line G2 should go through this Point P2 can be placed to a higher one Level of security to get. There is a larger deviation from a straight line G2, so can the individual adjacent points P2 and the zero point also connected to each other by sub-sections, not shown become.

With the straight line G2, or the partial straight line, the printer or a control device can be used for each voltage S1 in front of the printing unit 01 (Straight G1) with the dampening solution guide selected for this production, determine the voltage drop ΔS of the respective paper, which in the most sensitive production - e.g. B. eight times dampening solution and ink on the paper - can occur.

The printer or a control or regulating device can thus take a guideline value from the diagram as to which voltage S1-min it is minimal in front of the printing unit 01 may adjust without the web 02 runs after the printing unit 01. The arrows in 3 based on the required minimum voltage S2-min, e.g. B. 8 daN / m, followed vertically to the straight line G2, subsequently horizontally to the straight line G1 and finally vertically to the resulting value for the minimum stress S1-min on the abscissa. The minimal in front of the printing unit 01 The voltage S1-min to be set results for the paper and the production conditions z. B. to about 16 daN / m.

To one after the printing unit 01 to determine the maximum voltage to be set S2-max without the web 02 when starting, stopping or changing roles, the arrows in 3 based on the required maximum tension S-max for the dry web 01 , e.g. B. 60 daN / m, followed vertically to the straight line G1, subsequently horizontally to the straight line G2 and finally vertically to the resulting value for the maximum stress S2-max on the abscissa. The maximum after the printing unit 01 The voltage to be set S2-max results for the present paper and the present production conditions e.g. B. to about 30 daN / m.

In a third embodiment ( 4 ) for the wet offset, in addition to the procedure described in the first or second example, for a voltage value x1 in the upper range, here 50 daN / m, the amount of dampening solution added in the printing units 03 ; 06 varied. One point W becomes the so-called "water plume limit" WG, ie the amount of dampening solution is so large that so-called water plumes appear in the printed image, and the other point SG means the lubrication limit SG, ie the amount of dampening solution is so small that lubrication of the Color occurs, formed.

By doing this further knowledge of Setting tolerances won. through these points WG and SG and the zero point again each line G3; The printer receives G4 one between these straight lines G3; G4 lying tolerance range, which exactly describes this paper to the printer and him for his Productions, e.g. B. four-sided (4/4) on both sides, safe setting options gives.

The highest level of security is achieved when determining the minimum voltage S1-min in front of the printing unit 01 and the maximum voltage S2-max according to the printing unit 01 of the procedure described above are based on the straight lines G1 and G4. For the lower limit of the voltage setting, ie for S2-min of z. B. 8 daN / m after the pressure unit 01 - wet track 02 - This results in a minimum voltage S1-min to be set in front of the printing unit 01 of approx. 25 daN / m. Is used as the upper limit z. B. S-max for the dry web 01 from Z. B. 60 daN / m before the printing unit 01 - dry web - put on, with this paper the tension S2 should be after the printing unit 01 in this production, e.g. B. 4/4, do not lie above the maximum voltage S2-max of approx. 25 daN / m.

In the case of productions with fewer water applications (2/2, 1/1, 4/1 productions) the upper limit of the tension S2-max of the then less wet web can be reached 02 after the printing unit 01 are noticeably higher. So with z. B. 2/2 productions for the paper shown the voltage drop ΔS z. B. only 20% of the voltage S1 in front of the printing unit 01 be.

Is the generation of the characteristic and / or the evaluation and regulation by a regulating or control device made, can be based on the one measuring point or on the basis of the several Measuring points either a linearization can be made, z. Legs Table or function is determined and stored on the basis of which the evaluation of for setting the voltage essential information such. B. the Voltages S1-min and S2-max occur.

The purely mathematical linearization of the voltage drop ΔS takes place, for example, by means of the straight line of origin according to the equation x2 = a⋅x1
for the relationship between the value x2 for the voltage S2 after the printing unit 01 and the value x1 of the voltage S1 in front of the printing unit 01 , The voltage drop ΔS results accordingly ΔS = x1⋅ (1 - a)
Voltage drop ΔS due to the dampening of the web ( 02 ) and voltage build-up ΔS ', e.g. B. due to an interruption in moisture, are to be considered here in the same way and differ only in the starting point. An expected voltage build-up ΔS 'would be, for example, as ΔS '= x2 / (1 - a)
to describe, and is not shown or discussed separately in the following. The evaluation and use is carried out in a similar way, but taking into account the above reverse view.

From the voltage values x1 and x2 of a single pair obtained as described above and obtained, for example, at 50 daN / m, a can be determined by forming the quotient x2 / x1 and is the result of evaluating the minimum and maximum voltages S1-min, S2-min, S-max for the dry web 01 and S2-max as follows: S1-min = S2-min / a S2-max = S-max⋅a

If there are several measured Pairs x1, x2 for several voltage values x1, for example by mathematical Process a medium, but preferably by the origin Even, or their value a can be determined. However, it can also the greatest value a selected from the values a which result from the formation of quotients x2 / x1.

There are several as described above P2 points not without great Multiple errors can be linearized Values a obtained from several measurements, and thus a in sections be defined.

The linear relationship can also in another way, e.g. B. as x1 = b⋅x2, then formed the above Relationships are to be changed in the same way.

The minimum and / or maximum voltage S1-min or S2-max obtained can be further processed directly in an automatic process for regulating or adjusting the voltage S and used, for example, to determine the limit values. In a fully automated process, in addition to a cycle of the measurement described above to determine the replacement characteristic or the linearized voltage drop ΔS, the value a calculates (if necessary in sections), the corresponding limit values for the minimum and maximum voltages S1-min, S2 -min, S-max for the dry web 01 , S2-max determined, and supplied to the regulating or control device for setting the voltage S.

The minimum voltage to be observed S2-min and / or the maximum allowable Voltage S-max can for one automated process in a regulating or control device stored and predeterminable.

Both the graphic and the tabular or the mathematical method are based on the basic principle of first determining a course of an expected voltage drop by the voltage drop of a web 02 by moistening in a printing unit 01 , especially in the worst case, using at least one pair of voltage values x1 and x2 in front of and behind the printing unit 01 we determined punctually. This is done by first without ink and dampening solution in the print-on position in front of and behind the printing unit 01 essentially the same value x1 for voltage S1; S2 is set, then ink and, if necessary, dampening solution is switched on, and after essentially stationary conditions have been reached, the value x2 for the voltage S2 behind the printing unit 01 is measured.

On the basis of the value pair obtained (or a plurality of value pairs obtained) x1, x2, an idealization then becomes a fictitious course for the one resulting from the dampening in the printing unit 01 caused voltage drop ΔS depending on a voltage S. In one case, this is done by using at least sectionally linearized replacement characteristic curves for the dependence of an unscaled strain ε * on the tension S, e.g. B in that the voltage value x1, or the voltage values x1, and the zero point, see above as by the voltage value x2, or the voltage values x2 respectively through straight line G1; G2; G3; G4 as a replacement straight line. In the other case, there is a basis, at least in sections, of a linear relationship between that in front of the printing unit 01 present voltage S1 and that after the printing unit 01 voltage S2 resulting from dampening by z. B. a value a for the slope of the linearized relationship between x1 and x2 is formed by forming quotients between the mutually assigned voltage values x1 and x2. With several pairs of voltage values x1 and x2, this can also be done in sections by forming the difference quotient.

The course obtained for the expected voltage drop is used to set the voltage S1; S2 before and / or after the printing unit 01 used by S2-min behind the printing unit due to a predeterminable minimum voltage 01 a minimum tension S1-min in front of the printing unit, and / or based on a predeterminable maximum tension S-max for the dry web 01 a maximum allowable voltage S2-max behind the printing unit 01 is determined.

The information about the determined course, as graphic, as function, as table or a modification to this, or the slope or the slopes, can advantageous for the specific paper, if applicable i. V. m. specific production, in a storage unit or the regulating or control device be, and for latter Productions can be called up without having to take another measurement would.

The determination of the course and the subsequent Evaluation and use in setting the voltages S; S1; S2 for production is simple, inexpensive and reliable.

01

Processing stage, printing unit

02

Train, paper web

03

Printing, Double printing

04

satellite cylinder

05

-

06

printing unit

07

reelstands

08

traction group

09

measuring point

10

-

11

bruise

12

measuring point

13

traction group

14

traction group

15

-

16

formers

17

infeed

S

Tension, train

S1

Tension, train

S2

Tension, train

.DELTA.S

voltage drop

S1-min

Tension, dry, minimal

S2-min

Tension, moist, minimal

S-max

Tension, dry, maximum

S2-max

Tension, moist, maximum

ε *

unscaled strain

G1

Just, Spare characteristic

G2

Just, Spare characteristic

G3

Just, Spare characteristic

G4

Just, Spare characteristic

x1

Voltage value (S1)

x2

voltage value (S2)

P1

Point (S, ε *)

P2

Point (S, ε *)

SG

Point, smearing limit

WG

Point, Water flags border

Claims (14)

Method for determining a course for an expected voltage drop (ΔS) of a web in a printing unit ( 01 ) - by first in front of and behind the printing unit without ink and dampening solution in the print-on position ( 01 ) essentially a value (x1) for the voltage (S1; S2) is set, - then ink and, if necessary, dampening solution is switched on, - after essentially steady-state conditions are reached, a value (x2) for the voltage (S2) behind Printing unit ( 01 ) is measured, - and finally, based on at least one of the pairs obtained in this way for the stress values (x1, x2) by at least sectionally linearizing a stress-strain dependency, a fictitious course for the moisture caused in the printing unit ( 01 ) caused voltage drop (ΔS) depending on a voltage (S) festge is laid. Method according to claim 1, characterized in that by means of the at least one pair of tension values (x1, x2) at least in sections each for the dry web ( 02 ) and by the printing unit ( 01 ) moistened web ( 02 ) linearized substitute characteristic curves (G1; G2; G3; G3) for the dependence of an unscaled strain (ε *) on the stress (S) are formed. A method according to claim 2, characterized in that in one the unscaled elongation (ε *) against the diagram representing the voltage (S) on a freely selectable height of Voltage value (x1) and the voltage value (x2) entered at the same level is, and the replacement characteristic curves (G1; G2; G3; G4) each as a straight line (G1; G2; G3; G4) by the origin and the respective voltage value (x1; X2) or if there are several pairs of voltage values (x1, x2) as middle straight line passing through the origin (G1; G2; G3; G4) or as the most distant from each other by which Straight lines originating (G1; G2; G3; G4) are formed. Method according to Claim 3, characterized in that the voltage drop (ΔS) to be expected in the printing unit (01) by forming a difference between the associated voltages (S) between two points (P1; P2) of the two straight lines (G1; G2; G3; G4) for the dry and the wet web ( 02 ), which are at the same height parallel to the axis for the voltage (S). A method according to claim 1, characterized in that by Quotient formation between the voltage values assigned to each other (x1) and (x2) or by forming the difference quotient pairs of voltage values (x1, x2) at least in sections, a value (a) for the slope of the linearized relationship between (x1) and (x2) is formed. Method according to Claim 5, characterized in that the voltage drop (ΔS) to be expected in the printing unit (01) by means of the value for the slope (a) and that before the printing unit ( 01 ) applied voltage (S1) according to ΔS = S1⋅ (1 - a), and an expected voltage build-up (ΔS ') by means of the value for the slope (a) and after the pressure unit ( 01 ) applied voltage (S2) is determined according to ΔS '= S2 / (1 - a). Method according to Claim 1, characterized in that the course obtained for the expected voltage drop (ΔS) for setting the voltage (S1; S2) before and / or after the printing unit ( 01 ) is used. Method according to Claim 7, characterized in that one or more limit values (S1-min; S2-max) for the voltage (S1; S2) before and / or after the printing unit ( 01 ) and that this limit value (S1-min; S2-max) or these limit values (S1-min; S2-max) for setting the voltage (S1; S2) before and / or after the printing unit ( 01 ) can be used. A method according to claim 1, characterized in that the Method for determining the course as an activatable sub-process in a Web tension control expires. Method for setting a tension (S; S1; S2) of a web ( 02 ), in the run-up to a production a course for a dampening in a printing unit ( 01 ) expected voltage drop (ΔS), one or more limit values (S1-min; S2-max) for the voltage (S1; S2) before and / or after the printing unit ( 01 ) are determined, and this limit value (S1-min; S2-max) or these limit values (S1-min; S2-max) for setting the voltage (S1; S2) before and / or after the printing unit ( 01 ) can be used. Method according to Claim 10, characterized in that, based on the curve for the expected voltage drop (ΔS), starting from a predeterminable minimum voltage (S2-min) behind the printing unit (01), a minimum voltage (S1-min) in front of the printing unit ( 01 ) is determined as the limit (S1-min). Method according to Claim 10, characterized in that, based on the course for the expected voltage drop (ΔS), starting from a predeterminable maximum tension (S-max) for the dry web ( 02 ) a maximum permissible voltage (S2-max) behind the printing unit ( 01 ) is determined as the limit value (S2-max). Method according to claim 11 and / or 12, characterized in that that the limit value (S1-min; S2-max) of a web tension control is fed. A method according to claim 10, characterized in that the course for the expected voltage drop (ΔS) is determined, - by first in front of and behind the printing unit without ink and fountain solution in the print-on position ( 01 ) essentially a value (x1) for the voltage (S1; S2) is set, - then ink and, if necessary, dampening solution is switched on, - after essentially steady-state conditions are reached, a value (x2) for the voltage (S2) behind Printing unit ( 01 ) is measured, - and finally on the basis of at least one of the pairs obtained in this way for the tension values (x1, x2) by linearization, at least in sections, a fictitious course for the damping in the printing unit ( 01 ) caused voltage drop (ΔS) is determined depending on a voltage (S).