DE102006031101A1 - Adapting method for number of stepping motor cycles per revolution involves performing recording of original printing by setting corrected number of stepping motor cycles per revolution in accordance with predetermined relationship - Google Patents

Abstract

A recording of the original printing is performed by setting the corrected number of stepping motor cycles per revolution in accordance with the relationship K 1=CxK 0. The parameter K 1is the corrected number of stepping motor cycles per revolution, c is the setting correction factor in dependence on different temperature dependent length expansion of the feed spindle and reference object, and K 0is the setting number of the stepping motor cycles per revolution of an exposure drum (1). The object carrier is moved axially along the exposure drum in the feed direction on feed spindle. Independent claims are also included for the following: (1) an adapting device of number of stepping motor cycles per revolution of exposure drum; (2) and an exposer for recording printing original.

Description

The The invention relates to a method according to the preamble of the claim 1 and a device according to the preamble of claim 7.

In The reproduction technique produces print templates for printed pages, the contain all elements to be printed such as texts, graphics and images. For the colored printing is for Each ink creates a separate artwork that contains all the elements contains which are printed in the respective color. For the four-color printing are the inks cyan, magenta, yellow and black (CMYK). The after Printing inks separated printing originals are also called color separations. The artwork is usually rasterized and exposed on an imagesetter Films exposed, with which then printing plates for high-volume printing getting produced. Alternatively you can the print templates in special exposure equipment also on printing plates be exposed directly or as digital data to one handed over digital printing machine. There, the print template data then, for example, with a in the printing press integrated imaging unit on printing plates exposed immediately before the printing starts.

To In the current state of the art, the artwork is electronic reproduced. This will be images that are not yet in digital form are scanned in a color scanner and in the form of digital Data saved. Digital images can, for example, by means of Digital cameras are generated. Texts are created using word processing programs generated and graphics with drawing programs. With a layout program the picture, text and graphic elements become a printed page compiled. After separation, lie in the printing inks the artwork then in digital form. As data formats for Description of the print templates today are largely the page description languages Postscript and PDF (Portable Document Format). The postscript or PDF data is saved before recording the artwork in a raster image processor (RIP) in a first step in color separation values for the color separations CMYK converted. In the process arise for each pixel has four color separation values as tone values in the value range from 0 to 100%. The color separation values are a measure of the color densities with which the four printing colors cyan, magenta, yellow and black on the substrate to be printed. In cases, printing with more than four colors is every pixel described by as many color separation values as are printing inks gives. The color separation values can e.g. stored with 8 bits per pixel and ink as data values whose value ranges from 0% to 100% in 256 tone levels is divided.

The Data from several printed pages are combined with the data of other elements, such as registration marks, crop marks and folding marks as well as print control fields, to print templates for summarized a sheet. This print sheet data will also be provided as color separation values (CMYK).

Untarschiedliche Torn values of a color separation to be reproduced can be printed only by an area modulation the applied inks, i. by a screening, play. The area modulation The printing inks can, for example, according to a method for dot patterning take place, in which the different tone levels of the color separation data be converted into halftone dots of different sizes, the in a regular grid are arranged with periodically repeating grid cells. A grid cell for a typical sixty grid comprises a square with 1/60 cm edge length, i. a grid cell has the dimensions 166 microns × 166 microns. When recording the color separations on a printing plate, the grid points in the individual grid cells composed of exposure points by an order of magnitude smaller than the grid points are. A typical resolution of Exposure points is, for example, 1000 exposure points per centimeter, i.e. one exposure point has the dimensions 10 μm × 10 μm. The implementation the color separation values in grid points is done in a second Step in the further processing of the color separation data in the raster image processor, which the color separation data into high-resolution binary values with only two brightness values be converted (exposed or unexposed), the pattern form the modulated dot matrix. In this way, the Print template data of each color separation in the form of a high-resolution raster bitmap described for each of the exposure points on the print area contains one bit, the indicates whether this exposure point is to be exposed or not.

In the recording devices used in the electronic reproduction technique for exposure of masters and printing forms, an exposure beam is generated, for example, a laser beam with a laser diode laser beam formed by optical means and focused on the recording material and a spot and line over the recording material by means of a deflection system distracted. There are also recording devices which, to increase the exposure speed, produce a bundle of laser beams, eg with a separate laser light source for each laser beam, and with each sweep of the recording material as several recording lines of the printing plate simultaneously expose. Nowadays, printing plates are printing plates which are exposed in a platesetter or directly in a digital printing machine in which a unit for plate exposure is integrated. The recording material may be on a flat surface (flatbed imagesetter), in a cylindrical well (internal drum imagesetter) or on a drum (external drum imagesetter). The artwork can also be first exposed to film so that so-called color separation films are created, which are then used by means of a photographic Umkopierverfahrens for producing the printing plates.

flatbed work predominantly with a fast rotating polygon mirror, whose mirror surfaces the Laser beam across direct the recording material while simultaneously recording material is moved perpendicular to the deflection of the laser beam. To this Way is recording line for Illuminated recording line. As the movement of the laser beam over the recording material the length of the light path changes, an elaborate imaging optics is required, which is the result conditional size changes of the Exposure point compensated.

at an internal drum imagesetter is the material to be exposed the inner surface a partially open hollow cylinder mounted and with a laser beam exposed along the cylinder axis to a deflection device directed, which reflects the laser beam perpendicular to the material. The deflector, a prism or a mirror, rotates during operation at high speed and is doing in the direction of the cylinder axis moves so that the deflected laser beam is circular or helical Describes recording lines on the material.

at an external drum imagesetter becomes the material to be exposed in the form of films or printing plates mounted on a rotatably mounted drum. While the drum is rotating, becomes an exposure head in a relatively short distance axially the drum moves along. The exposure head is in the feed direction moved by means of a feed screw, with which it is positively connected and which is rotated by a stepping motor. Of the Exposure head focuses one or more laser beams the drum surface, the drum surface in the form of helical lines. In this way, one or more turns every drum revolution Imaging lines exposed to the recording material.

Around to shorten the exposure time and thus increase the economics of the imagesetter, work external drum preferably with one or more exposure heads, each one a bunch of N laser beams by means of an exposure optics as a in the axial direction the exposure drum oriented linear array of exposure points the surface of the recording material. If there are multiple exposure heads, are the exposure heads For example, arranged on an exposure head carrier, with the feed screw is connected, so that by the rotational movement of the feed screw all exposure heads together in the feed direction along the exposure drum to be moved. The exposure heads are arranged at a distance in the axial direction of the exposure drum, which is a fraction of the axial drum length, for example at three exposure heads one third of the axial drum length. To submit a print template the entire drum length Record the exposure head then needs using the feed spindle only one Distance to be moved, which corresponds to the distance of the exposure heads. Each exposure head then exposes only one recording tape of the artwork. The recording time for the artwork is correspondingly short.

The Number of laser beams, each exposure head on the recording material maps is For example, N = 64, but may also be any other number. When the exposure drum rotates, then several groups exposed in each case by N recording lines in parallel, which are helical the surface wind the exposure drum. The feed speed of the exposure heads is set to go one round after one drum revolution Distance in the axial direction of the drum have moved the width which corresponds to N recording lines. This will close the next Drum rotation to be exposed N recording lines immediately to the N recording lines exposed in the previous drum revolution at. In another mode of operation, the so-called interleave writing method, The laser beams are not considered N exposure points with the distance each represented by a recording line width but with a greater distance, which corresponds to a multiple P of the width of a recording line. For suitable conditions N and P decrease after successive drum rotations and the gaps between the first exposed recording lines with further recording lines filled.

At the high resolution of 1000 recording lines per centimeter, the spacing of the recording lines is 10 μm. This distance must always be maintained with a high degree of precision. In particular, the next N recording lines must turn to the drum after one drum revolution connect previously exposed recording lines without gaps. In addition, when exposing with multiple exposure heads, this distance must be maintained between the last recording line of one exposure head and the first recording line of the adjacent exposure head, ie where the recording bands exposed by the individual exposure heads are contiguous. If the line spacing is not maintained exactly, there will be disturbing patterns in the recorded artwork for which the eye is particularly sensitive. This means that the feed distance of the exposure heads per drum revolution must always be constant, regardless of temperature changes or other disturbing influences. In particular, the required accuracy for the feed path for exposure of a recording tape is ± 1 μm.

Usually is used as a drive for the feed screw uses a stepper motor, and the feed distance is set by the number of stepper motor pulses that the stepper motor during one certain number of drum turns. Especially the temperature-related change in length the feed screw causes the feed distance for the so set number of stepper motor clocks varies. For a typical Feed distance of 200 mm the change in length 2.2 μm each Degrees Celsius, for a temperature change of 10 degrees thus already 22 microns. This change is so big that the required accuracy of the feed drive is not without corrective actions can be complied with.

to This problem could be alleviated Printed artwork images set up in an air-conditioned room be, but with restrictions is connected and causes high costs. Another possibility is to air-condition the air inside the print mastersetter. However, you come across this on different problems. To prevent ingress of dust and gases from the outside To reduce, a slight overpressure is generated in the interior. The recording material is placed on the exposure drum by means of vacuum fixed. When exposed to high-power laser beams Particles and gases need be sucked to the units in the imagesetter, in particular the optical components, to protect against contamination. All these different Increase air movements the difficulties and the effort, an effective of the external conditions largely closed air conditioning system for the air in the interior of the To realize the exposure. Furthermore is thus hardly the required accuracy to comply, namely the Temperature of the feed spindle to a constant half a degree. Also, methods that control the temperature of the feed screw and, where appropriate measure other related to the feed drive components and from that the length change calculating the feed distance are not sufficiently reliable and accurate.

In spite of occurring temperature-dependent changes in length of the feed screw to form a printing plate in a suitable manner is in the German patent DE 103 53 029 B3 a method and a device for measuring the change in length and a corresponding correction of the control of the stepper motor proposed. The measurement of the change in length takes place via a reference rod which is arranged parallel to the feed direction of the exposure head carrier. At this reference rod, a reference path is arranged. It is determined once an optimal number M ₀ of stepping motor clocks required by the stepper motor to transport the exposure head along the reference path, so that one or more exposure heads optimally imaged on the exposure head support a printing plate on an exposure drum. Before each further imaging, a further number M _X of stepping motor clocks is detected which is necessary for the movement of the exposure head carrier along the reference path. This number of stepping motor clocks is dependent on temperature-dependent change in length of the feed screw, while the length of the reference path does not change. If an optimal imaging of the entire plate, a specific section of the plate or during a drum rotation during the first described optimal imaging K ₀ stepping motor cycle is required, then for a corresponding formation with a length-changed feed spindle, a corrected stepping motor cycle number K _X results from a modification give the number K ₀ with the quotient of M _X / M ₀ : K x = K 0 · M X / M 0

K _x and K ₀ each correlate with a certain number of drum rotations and determine the feed rate of the spindle.

In the DE 103 53 029 B3 it is provided that the reference path does not change its length during the measurements. On the one hand, this is the case when a material is used whose dimensions are substantially unaffected by temperature changes, such as glass or ceramic, on the other hand, this constancy of the reference distance can be achieved by the reference rod for the reference distance by a tempering on a constant temperature is maintained. This necessary tempering system is relatively complicated and expensive. Termination fluids may leak and cause damage or corrosion may be possible. When using It must be borne in mind that the use of temperature-stable reference rods made of glass or ceramics must be relatively expensive to manufacture and can not always be ideally adapted to all requirements

It Therefore, the object of the invention is a method and an apparatus introduce the genus mentioned above, with the described Disadvantages and problems of the prior art can be overcome.

The The object of the invention is achieved by a method with the characterizing Features of claim 1 and a device with the characterizing Characteristics of claim 7 solved.

Further Subtasks are solved by the subordinate claims.

For the recording of the print original, a corrected number K _k = c × K _{0 is set} as a stepping motor clock per revolution of the exposure drum. The correction factor c is for this purpose determined and set in dependence on the different temperature-dependent length expansions of the feed screw and the reference object. It is provided that the reference object has an expansion coefficient α _RS , which is clearly different from zero and the expansion coefficient of the feed screw α _SP .

The correction factor c can be determined in a further development of the invention as a function of the difference α _RS - α _SP and numbers M ₀ and M _x . M ₀ is the number of stepping motor clocks required by the slide to traverse a reference path substantially parallel to the feed direction, while M _{X is} the number of stepping motor clocks required by the slide just before a recording of a print original for traversing the reference path.

ermittelt wird.Advantageously, it is provided that for the recording of the print original, a corrected number K _k of stepping motor clocks per revolution of the exposure drum according to the relationship K k = C × K 0 is adjusted and the correction factor C according to the relationship

is determined.

K ₀ is the number of stepping motor clocks per revolution in a first laboratory measurement with an optimal exposure, M _{0 is} the number of cycles for traversing a reference path during an optimal exposure and M _{x is} the corresponding number before an exposure under changed temperature conditions.

Advantageously, in the calculation of the correction factor proposed here, a length change of the reference distance as a function of the temperature is taken into account. About the two expansion coefficients α _SP and α _RS , the different properties of the length changes for the feed screw and also for the reference rod have been taken into account. It is thus not necessary to use a reference rod which does not change its length as a function of the temperature.

Particularly advantageously, it is provided in terms of apparatus that the reference object has a coefficient of expansion α _RS different from zero and from the expansion coefficient α _SP .

Especially is provided that uses a reference rod as the reference object which is its extent and therefore the length of the reference distance in dependence changes from the temperature monotonously.

In particular, a reference object made of a material with a larger expansion coefficient α _RS than the expansion coefficient α _{SP of} the spindle is to be used. This allows the correction factor C to assume a value that is more independent of measurement tolerances.

der Ausdehnungskoeffizienten von Referenzobjekt und Vorschubspindel größer als 1,9 ist. Dieses kann erfindungsgemäß besonders günstig dadurch erreicht werden, dass der Referenzstab, bzw. das Referenzobjekt aus Aluminium gebildet ist. Die Vorschubspindel wird im Allgemeinen aus Stahl sein. Sie wird dann den geforderten Quotienten der Ausdehnungskoeffizienten ergeben. Hierdurch ist der Korrekturfaktor C weniger fehlerbehaftet.In order to achieve a particularly favorable correction factor, it is provided that the quotient

the coefficient of expansion of reference object and feed screw is greater than 1.9. This can be achieved particularly favorable according to the invention in that the reference rod, or the reference object is formed of aluminum. The feed screw will generally be steel. she will then give the required quotient of the expansion coefficients. As a result, the correction factor C is less error-prone.

By a large difference in the expansion coefficients, a particularly clear, temperature-dependent change in the measured number of stepping motor clocks M _x can be achieved.

to execution of the procedure it is provided in a development that the Starting point and the end point of the reference distance with at least be detected by a sensor. This can be done by device be achieved that on the reference rod or reference object two Reference marks are attached, with these reference marks the starting point and the end point of the reference link is marked and a Reference mark sensor is provided on the slide, with the the reference marks are recognized. In the slide can it is advantageously an exposure head carrier.

alternative it is also possible that on the slide, or exposure head carrier only one reference mark is provided and on the reference object two reference mark sensors are provided, with which the starting point and the end point of the reference link is marked. Then can With these reference mark sensors the reference mark can be recognized.

Especially Advantageously, it is provided that it is the reference mark sensor is a forked light barrier.

advantageously, the reference object should be structurally arranged so that the reference object and the feed screw each have the same temperature changes Experienced.

at the reference object may be e.g. around an edge or a metal carrier inside act of the imagesetter. Particularly advantageously, it is provided that it is a reference rod, as such, ideally suited to the needs the described method is tailored.

One advantageous embodiment However, the invention is not limited to the scope hereof and on which further inventive features can be found can is shown in the drawings.

It demonstrate:

1 a printing platesetter with a device for length compensation of a feed screw,

2 an alternative device for length compensation of a feed screw.

The 1 schematically shows the structure of an outer drum exposure for exposure of a printing plate 3 on an exposure drum 1 is spanned. The exposure drum is rotatably mounted and can with a rotary drive not shown here in the direction of the rotation arrow 2 be put in a uniform rotational movement. The printing plate 3 is by means of a terminal block 9 and clamping pieces 10 fixed on the surface of the exposure drum. In addition, a vacuum device, not shown here, may be provided which the pressure plate 3 sucked on the drum surface.

The exposure of the printing plate 3 takes place by means of an exposure head 11 , This exposure head is on an exposure head carrier 16 arranged. It can be provided in particular that on an exposure head 16 several exposure heads 11 are located. These multiple exposure heads 11 then can the pressure plate 3 parallel pictures. The exposure head 11 includes N laser diodes, not shown here. These laser diodes emit N laser beams 12 on the printing plate 3 be focused. To illustrate the printing plate 3 becomes the exposure drum 1 rotated and the exposure head carrier 16 becomes axially at the exposure drum at a relatively short distance 1 moved along. At the same time, N images are laser beams 12 the pressure plate 3 in the form of helical lines as a function of printing data, which consists of a print data store, not shown here, on the exposure head 11 be handed over.

By means of laser beams 12 be on the printing plate 3 Illustrated recording lines. These recording lines of the different laser diodes are interlocked depending on the required resolution of the imaging. At a resolution of A = 100 recording lines per mm, the pitch of the recording lines is 10 μm. During one drum revolution, the exposure head images 11 a strip of the width Q on the printing plate 3 , The stripe width Q results from the formula Q = N: A

The feed rate of the exposure head 11 must be set so that the exposure head 11 after a drum revolution has been moved in the feed direction by the distance Q, so that with each drum revolution illuminated recording lines seamlessly on each other shut down. The distance must be 10 μm in the feed direction. If this distance is not respected, particularly sensitive defects in the exposed print image are present to the eye 15 to recognize. These defects can be gaps or overlaps of individual image areas. It is therefore required an accuracy of the connection of recording lines, which is at +/- 1 micron.

The feed distance of the exposure head 11 per drum revolution is set by the number of motor cycles that the stepper motor 14 the feed spindle 13 during a drum rotation. The stepper motor 14 is, for example, a three-phase stepper motor, which is controlled with 10,000 motor cycles per spindle revolution. With a pitch of the feed spindle 13 of 2mm per spindle revolution results in a feed of 0.2 microns per engine cycle. With such a stepper motor 14 The feed can be adjusted with sufficient fine-tuning.

The length of the feed spindle 13 depends on the temperature prevailing in your environment. For this reason, the feed distance varies for a fixed number of step motor clocks. For a typical feed distance of 200mm, the change in length of the feed screw is 2.2 μm per C °. For a temperature change of 10 ° so already 22 microns. It does not matter in which direction the temperature changes, whether it gets colder or warmer. The changes shown here as a function of the temperature are so great that the required accuracy of the advance of the exposure head 11 can not be achieved without corrective action.

For the purpose of adjusting the feed rate of the exposure head 11 to a change in length of the feed screw 13 Here is a corresponding device for adjusting the number of stepping motor K per revolution of the exposure drum 1 intended. This device comprises a reference rod 30 on which a reference track 35 is appropriate. This reference route 35 is formed by two reference marks 31 on the reference bar 30 are attached. A first reference mark 31 describes the beginning of the reference route 35 and a second reference mark 31 at a distance R to the first reference mark 31 describes the end of the reference distance 35 , For the reference brands 31 For example, they may be metal tags that are a reference mark sensor 32 to stimulate the generation of a measurement signal. On the side of the exposure head carrier 16 there is a reference mark sensor 32 , which is designed here as a fork light barrier. This fork light barrier is triggered in each case and generates a corresponding signal when it is a reference mark 31 detected. The reference rod is parallel to the feed spindle 13 aligned so that the reference marks 31 each the reference mark sensor 32 can trigger.

Both the reference bar 30 as well as the feed spindle 13 change their longitudinal extent depending on the prevailing temperature. These temperature-dependent changes in length are described by a material-dependent expansion coefficient α. The feed spindle 13 is generally made of steel or stainless steel and has an expansion coefficient α _SP of 12 × 10 ^-6 per Kelvin. This means that the length of the feed spindle changes by a factor α _SP when the temperature changes by 1 Kelvin. As material for the reference rod 30 a material is selected which has an expansion coefficient α _RS , which is substantially different from the expansion coefficient α _SP . In particular, it is provided that the expansion coefficient α _{RS is} greater than α _SP . For example, in the case illustrated here, it may be aluminum. Then, the expansion coefficient α _{RS is} 23.8 × 10 ^-6 per Kelvin. In this way, it is always guaranteed that changes in length of the reference rod 30 and the feed screw 13 distinguished so strongly that at a changed temperature, a different number of stepping motor clocks of the stepping motor 14 is needed to with the exposure head carrier 16 the reference route 35 to depart. Due to this changed number of stepping motor clocks then the control of the stepper motor 14 to the change in length of the feed screw 13 be adjusted.

The number of stepper motor clocks needed to pass the reference path 35 is counted by an unillustrated counting means and by an unillustrated storage means and stored.

By the number of step motor K files per revolution of the exposure drum 1 to the temperature-dependent change in length of the feed screw 13 A two-stage procedure is foreseen.

In a first calibration phase at any fixed temperature T _o a test exposure of the printing plate 3 performed. The feed rate of the feed screw is then varied to determine a number of stepping motor clocks per drum rotation for which optimum exposure, ie, no gaps or overlaps between two recording tapes, each exposed during one drum revolution, occurs. This then gives the calibration value K ₀ which is stored in the platesetter. Starting from this number of step motor K files per revolution becomes a second Number of stepping motor clocks M ₀ determined, which are necessary for this optimal exposure result to go through the reference path. This value is also stored in a memory of the platesetter.

The second phase of the method, the correction phase for determining the correction factor C is applied to the calibration value K _{is 0,} one of the change in length of the feed screw 13 adapted number K _k of stepping motor clocks per revolution of the exposure drum 1 results.

This correction phase is performed before each exposure pass of the printing plate imagesetter. In this way, changes in length of the feed screw 13 be considered for each new printing plate imaging. Even if between two images the temperature in and around the platesetter should fluctuate.

Before the start of the imaging, the exposure head carrier becomes 16 on the feed spindle 13 at the reference track 35 guided along. The feed rate of the stepper motor 14 is essentially irrelevant, since a given route is traveled.

The counting means then counts the number of stepping motor clocks M _x that are necessary for the reference mark sensor to count 32 on the exposure head carrier 16 the reference route 35 from that by the reference mark 31 formed beginning of the reference distance 35 through to the reference mark 31 formed end of the reference route 35 traverses.

If the temperature at this time of measurement is greater than the temperature T ₀ during the calibration phase, then the reference bar 30 due to the larger expansion coefficient α _{RS expanded} more than the feed screw 13 , The number M _{x of} the stepping motor clock is then greater than the number M _o which was recorded during the calibration phase. If the different expansion coefficients α _RS and expansion coefficient α _{SP are} both known, the correction factor C according to the relationship results from the measured values for the number of stepping motor cycles for passing through the reference path during the calibration phase and the correction phase:

It should also be remembered that while it is advantageous if the feed screw 13 and the reference bar 30 Both are in the same temperature environment but this is not a condition for a working process. However, a prerequisite for adapting the stepping motor clock to the change in length of the feed spindle is that the temperature difference between the feed screw 13 and the reference bar 30 should remain as constant as possible. This is given, for example, given the geometry of the reference bar 30 so adapts that the heat flows within the platesetter always to the same temperature changes in feed screw 13 and reference bar 30 to lead. A particularly accurate determination of the correction factor C results in particular when the distance beginning, end of the two reference marks 31 is chosen as large as possible.

From the correction factor C thus determined, the feed rate of the exposure head carrier necessary for achieving an optimum imaging result can then be determined 16 in which a corrected number K _k of step motor clocks of the stepping motor 14 each revolution of the exposure drum 1 after the relationship K k = C × K 0 is set.

In the 2 is an alternative embodiment of the device for adjusting the number of stepping motor K per revolution of the exposure drum 1 shown.

Here is the reference distance 35 by two reference mark sensors 32 formed on the reference bar 30 are arranged. The distance between the two reference mark sensors 32 Therefore, the distance R is the first reference mark sensor 32 forms the beginning of the reference route 35 and the second reference mark sensor 32 forms the end of the reference section 35 , The reference mark sensors 32 can in particular as fork light barriers also for 1 described, be trained. On the side of the exposure head carrier 16 is a reference mark 31 provided at a feed of the exposure head carrier 16 the reference mark sensors 32 trigger. Again, the reference bar 30 parallel to the feed spindle 13 aligned. The same reference numbers mean the same elements as in 1 , Apart from the exchange of reference mark sensors 32 with the reference mark 31 and conversely, the structure of the alternative apparatus shown here is identical to the structure of FIG 1 shown device. Also, the methods performed for adapting the number of stepping motor clocks K are identical. In particular, the methods and devices presented here are not limited to the described sensor concepts. It can too Be provided contact sensors or sensors via capacitances. It can also be provided that several exposure heads 11 on an exposure head carrier 16 are provided. Corresponding sensor concepts and exposure head arrangements are also, for example, in the German patent specification DE 103 53 029 B3 described.

1

Imaging drum

2

rotation arrow

3

printing plate

9

terminal block

10

clamp

11

exposure head

12

laser beam

13

feed screw

14

stepper motor

15

print image

16

Exposure head carrier

30

reference bar

31

reference mark

32

Reference mark sensor

35

reference section

Claims (20)

Method for adjusting the number of stepping motor clocks K per revolution of an exposure drum ( 1 ) to a temperature-dependent change in length of a feed screw ( 13 ) with an expansion coefficient α _SP in an imagesetter for recording masters of printing ( 3 ), wherein - a slide ( 16 ) on the feed spindle ( 13 ) by means of a stepping motor ( 14 ) in a feed direction axially on the exposure drum ( 1 ) is moved along, - during a basic setting, a first number K ₀ of step motor clocks per revolution of the exposure drum ( 1 ), - a reference path substantially parallel to the feed direction ( 35 ) by a reference object ( 30 ) is provided with an expansion coefficient of α _RS , characterized in that for the recording of the artwork ( 3 ), A corrected number K _k of stepping motor cycles per revolution of the exposure drum ( 1 ) is set according to the relationship K _K = c · K ₀ , and the correction factor c is dependent on the different temperature-dependent length expansions of the feed spindle (FIG. 13 ) and the reference object ( 16 ) is set. Method according to Claim 1, characterized in that a reference rod ( 30 ) is used, its extension and thus the length of the reference section ( 35 ) changes monotonically depending on the temperature. Method according to one of claims 1 or 2, characterized in that the reference object ( 30 ) made of a material with a zero and the coefficient of expansion α _{SP of} the spindle ( 13 ) significantly different expansion coefficient α _RS is used. Method according to claim 3, characterized in that the reference object ( 30 ) of a material with a greater coefficient of expansion α _RS than the coefficient of expansion a _{SP of} the spindle ( 13 ) is used. A method according to claim 4, characterized in that the quotient

is greater than 1.9. Method according to one of claims 1 to 5, characterized in that as material for the reference object ( 30 ) Aluminum is used. Method according to at least one of claims 1 to 6, characterized in that the starting point and the end point of the reference path ( 35 ) with at least one sensor ( 32 ) is recognized. Method according to at least one of claims 1 to 7, characterized in that - a number M _{0 is determined} by stepping motor clocks which the slide ( 16 ) for passing through a feed path substantially parallel reference path ( 35 ), - immediately before recording a print template ( 3 ) the number M _{x of} the chritt motor acts is determined which the slide ( 16 ) for traversing the reference route ( 35 ) and - the correction factor c is determined as a function of the difference α _RS - α _{SP of} the different coefficients of expansion and the numbers M ₀ and M _X. Method according to at least one of claims 1 to 8, characterized in that the correction factor c according to the relationship

is determined. Method according to at least one of claims 1 to 9, characterized in that as Slide an exposure head carrier ( 16 ) and the number K ₀ corresponds to the number of stepping motor clocks at which a defined exposure result is printed on a print original ( 3 ) by means of at least one exposure head ( 11 ) on the exposure head carrier ( 16 ) is achieved. Device for adapting the number of stepping motor clocks K per revolution of an exposure drum ( 1 ) to a temperature-dependent change in length of a feed screw ( 13 ) with an expansion coefficient α _SP in an imagesetter for recording masters of printing ( 3 ), wherein - the imagesetter comprises a microscope slide ( 16 ) mounted on a feed spindle ( 13 ) by means of a stepping motor ( 14 ) in a feed direction axially on the exposure drum ( 1 ) is moved along, - a reference distance ( 35 ) by a reference object ( 30 ), and - a counting device is provided for determining the number of stepping motor clocks which the slide ( 16 ) for traversing the reference route ( 35 ), characterized in that the reference object ( 16 ) has a coefficient of expansion α _{RS which} differs significantly from zero and from the expansion coefficient α _SP . Device according to claim 11, characterized in that the reference object ( 16 ) has a larger expansion coefficient α _RS than the feed spindle ( 13 ) having. Apparatus according to claim 12, characterized in that the quotient

the coefficient of expansion of the reference object ( 16 ) and feed spindle ( 13 ) is greater than 1.9. Device according to claim 12 or 13, characterized in that the reference object ( 16 ) is formed of aluminum. Device according to at least one of claims 11 to 14, characterized in that two reference marks ( 31 ) on the reference object ( 30 ), with these reference marks ( 31 ) the starting point and the end point of the reference route ( 35 ), and a reference mark sensor ( 32 ) on the slide ( 16 ) is provided with the reference marks ( 31 ) be recognized. Device according to at least one of claims 11 to 14, characterized in that a reference mark ( 31 ) on the slide ( 16 ) is mounted on the reference object ( 30 ) two reference mark sensors ( 32 ) are provided, with which the starting point and the end point of the reference route ( 35 ) and with these reference mark sensors ( 32 ) the reference mark ( 31 ) is recognized. Device according to one of claims 15 or 16, characterized in that the reference mark sensor ( 32 ) is a forked light barrier. Device according to one of claims 11 to 17, characterized in that the reference object ( 30 ) is structurally arranged so that the reference object ( 30 ) and the feed spindle ( 13 ) are subjected to substantially the same temperature changes. Device according to one of claims 11 to 18, characterized in that the reference object is a reference rod ( 30 ). Device according to at least one of claims 11 to 19, characterized in that the slide has an exposure head carrier ( 16 ) for carrying at least one exposure head ( 11 ).