DE3909764A1 - OPTO-ELECTRONIC ADJUSTMENT METHOD AND DEVICE FOR THE AUTOMATIC COMPUTER-CONTROLLED POSITIONING OF THE PRINTING TEMPLATES OF A ROTARY SCREEN PRINTING MACHINE - Google Patents

Abstract

The method and the device based thereon for automatic computer-based positioning of the printing stencils (1) for a rotary screen printing press with optoelectronic scanning of printing marks of different configurations applied to the stencils, provision is made according to the invention for the use of an optical measurement route (2, 11, 12) which penetrates the hollow cylinder wall of the respective printing stencil (1). The electric signal pattern is read into a computer which recognises the printing mark pattern on the basis of a preprogrammed logic and provides control commands to servomotors (4[X], 5[Y]) for the axial and rotational adjustment of the respective printing stencil. The underlying measurement principle has the advantage that the measurement is independent of the surface contrast of the stencil and any engraving faults will have no effect. Furthermore, different stencil diameters can be used without readjusting the measurement route. <IMAGE>

Description

The invention relates to an optoelectronic Justierver drive and an adjustment device for automatic, computer controlled positioning of the printing stencils Rotary screen printing machine with opto-electronic scanning of printing marks attached to the printing stencils different configuration, their electrical signal pattern is read into a computer based on Programmed logic recognizes the print pattern and Steuerbe lack of servo motors for axial and rotary and, if necessary, radial adjustment of the respective Printing template.

For the production of multi-colored patterns, especially Tex tilmuster, it is required on machines of the type mentioned Lich, in the individual successive printing groups fixed printing stencil cylinders from their engraving  speaking in the required position (rap port determination). This setting is usually made during production in creeper by adjusting the individual printing units via handwheels at the same time visual control of the print result.

Except for the high expenditure of time and inevitable Reject production has this manual method further parts, especially when using reactive pressure sensors serve as a visual check of the entries made positions not at all or only after a connection subsequent process (e.g. development) is possible.

To the required setting of the printing units already To be performed automatically before printing begins opto-electronic detection of the template surface been struck to computerized positioning to enable. The subsequent became known Application of special reflex marks on the printing template to read these markings later enable reflex sensor. Such a solution of the However, the user only has adjustment problems difficult to defend, since the subsequent attachment of the he mentioned markings must be extremely precise and large Experience requires a sufficiently high system accuracy guarantee. Show existing experience However, the markings also change over time can change or replace due to wear.

Further improvement has already been proposed To use reflection measurement system that is able to already in the production of photographic stencils so-called registration marks on each template in conjunction with a specially developed micro to recognize processor-controlled scanning methods to da through an automatic adjustment of the printing templates  enable. However, this reflection measurement method brings a number of problem with it. For one thing, the ver drive strongly from the surface contrast of the respective Scha blone dependent, which is especially true when using un different photoresist colors from the stencil manufacturer too large during the later template adjustment Can cause difficulties. Furthermore, the measuring ver can only be used to a limited extent with roughly perforated sheets screen seven and for stencils with so-called light Engraving errors. A distinction between error signals and measurement signals is only possible to a very limited extent here. Furthermore the measurement depends on the respective measuring distance between the sensor (receiver element) and the template, which for The consequence is that when using different templates diameter of the measuring head additionally adjusted and again must be adjusted very precisely. This caused experience According to the user considerable difficulties.

The invention is therefore based on the object, a method ren and a device for adjusting the stencils to create a rotary screen printing machine that works at high Operational reliability a fully automatic computer-controlled Positioning of the stencils enables, namely un depending on the type of stencil production and its Diameter.

The invention is characterized in that a Push through the hollow cylinder wall of the respective printing template de opto-electronic measuring section is used before preferably with coherent light, especially laser light, is operated.

Although there were fundamental concerns at first whether the problems outlined above with opto-electronic Er version of the template position, in particular by litter effects would not increase, there were overwhelming results  The new measuring principle has the following advantages:

• - The surface con is no longer for the measurement traces the respective printing template, but its through nonchalance prevailing, which makes one of the stencil color becomes completely independent.
• - Possible engraving errors in the stencil varnish and / or the The degree of fineness of the perforation during fluoroscopy Surprisingly, a much smaller influence on the measurement reliability of the system than expected.
• - An important advantage is that the transmitter and receiver of the opto-electronic measuring section even when used very greatly different template diameter unchanged be attached to the same fixed location can because it is surprisingly and unlike Reflection measurement method does not play a decisive role, if the light rays used for the measurement are not in the hit the template surface at a right angle.

Advantageous further developments of the inventive concept are in dependent claims and are specified in following it with reference to the drawings purifies. It shows

Figure 1 shows the basic system structure for the inventive method and a device for Justie tion of a rotary screen printing machine.

Fig. 2 shows a basic example and tested for the fixed-aligned attachment of the optoelectronic measurement path;

FIGS. 3 and 4 serve to illustrate the measuring and Ju bull method; and

FIGS. 5A and 5B illustrate the positioning process for the printing stencils on two successive flow charts.

Corresponding components or assemblies are in the Figures marked with the same references.

The system structure of Fig. 1 shows a stored in a Druckscha blonen clamping unit 3 printing stencil 1 , which is designed in a known manner as a hollow cylinder. The ink tube guided in the interior of the printing stencil 1 , the ink guide, the stencil drive wheels arranged at the end and the like are not shown in FIG. 1 for reasons of clarity, also because they are unchanged and known. The printing stencil 1 can be rotated in the X direction (rotation) via a first stepper motor 4 and offset in the Y direction (transverse movement; approximately axial direction) by a second stepper motor 5 . The adjustment movements of the printing stencil 1 by the servomotors 4 and 5 are carried out by a positioning computer 6 (axis computer) via digital driver amplifiers 7 and 8 in accordance with a program sequence stored in a master computer 9 of the overall system. According to the invention, the axis computer 6 receives at a control input 10 measurement signals from an opto-electrical measuring section 2 , which is essentially formed by a transmitter element 11 arranged outside the printing template 1 and a receiver element 12 fixed within the printing template 1 , the electrical signal pattern of which is the control input 10 applied to the axis computer 6 . The processing principle for the signals supplied by the opto-electronic measuring section 2 for positioning the printing stencil 1 via the servomotors 4 and 5 is explained further below with reference to FIGS. 4 and 5.

Fig. 2 shows in a basic lung Querschnittsdarstel an example of the mounting of the transmitter element 11 and the receiver unit 12 of the opto-electronic measuring section 2. As the drawing shows, the Emp catcher element 12 can be attached to and connected to the color level sensor 13 at the same time.

In the illustration of FIG. 2, very different diameters are drawn for the printing stencil 1 with a small diameter and a medium and a large diameter, illustrated in strong lines. When using such a wide variety of template diameters, depending on the mounting height of the opto-electronic measuring section 2, with reference to the respective center of diameter, a different "light angle" α is obtained , which is shown in the illustration by two tangent constructions on the small or large diameter is made visible. Despite these strongly differing light angles, which have a significant influence on reflection measurement and require readjustment of the measuring section when the template diameter changes, the measuring principle according to the invention with through light shows that readjustment is not necessary for the vast majority of applications.

After positioning and adjusting the stencils, it is fixed in the stencil clamping unit 3 in a usual and known manner.

Referring to Figs. 3, 4 and 5, the positio hereinafter nier- and erläu tert adjustment method for the printing stencil. This adjustment method can be divided into two sections, which can be called preselection (FIGS . 3 and 5A) or fine adjustment ( FIGS. 4 and 5B).

Fig. 3 shows the development of the outer surface of a printing stencil 1 , on the edge area (enlarged Darge provides) distributed over the circumference printed marks 14 are applied arranged according to a certain system. Another marking is the so-called register cross 16 , which marks the pattern start of each template 1 .

When preselecting, a (also greatly enlarged) light point moves as measuring point 15 with simultaneous X and Y feed spirally from the outer edge towards the center of the template until the first sensor signal is registered by one of the print marks 14 . At this moment, the Y feed is stopped, while the further X feed (rotation) leads to a sensor pulse sequence that corresponds exactly to the arrangement and sequence of the markings 14 on the template 1 .

As can be seen from the sketch in FIG. 3, the register cross 16 is the last marking in the marking sequence. Due to its different configuration, the registration cross 16 can be recognized by the computer logic as a reference point.

In the subsequent fine adjustment, the register cross 16 is measured in the following way:

It is overrun with the measuring point 15 in Fig. 4 vertical upper bar of the register 16 in the X direction and the pulse duration of the sensor pulse 17 in a certain ratio to the number of steps of the control pulses 18 of the stepper motor during the duration of the pulse 17 is brought GE . Then the stepper motor for the Y direction is excited in the same way and it is measured accordingly.

The sensor pulses determined for the X and Y directions are added up by calculation and then halved and converted into corresponding motor steps. In this way, the center 10 of the register cross 16 can be calculated and automatically adjusted via the X and Y feeds. If this state is reached, the template 1 is correctly positioned.

By the method according to the invention used here The system is in its ge accuracy does not depend on the size or line width of the register cross or other markings.

The successive flow diagrams of FIGS . 5A and 5B vividly again against the above-explained process for preselection and fine adjustment. Further explanations appear to be unnecessary for the person skilled in the art.

The process of preselection can vary depending on the software currently also on other marking sequences and forms can be easily reprogrammed without changing the opto-electronic measuring sections (sensors) of the total sy tems and / or without changing other hardware components.

In order to obtain high light-emitting diodes and a good signal / noise ratio of the measuring signal without simultaneously Lei stung for the opto-electronic elements 11, the need to increase 12, it may be advantageous that the transmitter element 11 to scan at a certain frequency, ie Pulse operation to work. The measurement signal can be distinguished from the excitation clock without difficulty using conventional methods of comparison and filtering.

Claims (8)

1. Opto-electronic adjustment method for automatic, computer-controlled positioning of the printing stencils of a rotary screen printing machine by optical scanning of printing marks attached to the printing stencils of different configuration, in which the receiver element of the opto-electronic measuring section due to the movement of the printing stencils when scanning the The signal pattern supplied to the print marks is read into a computer, which recognizes the print mark pattern by means of pre-programmed logic and issues control commands to servomotors for axia len and angular positioning of the respective print templates, characterized in that an op to electronic measuring section penetrating the Hohlzy cylinder wall of the respective print templates is used. 2. Opto-electronic adjustment method according to claim 1, characterized in that for the opto-electronic Measuring path coherent light, especially laser light, ver is applied. 3. Optoelectronic adjustment method according to claim 1, or 2, characterized in that the opto-electronic Measuring section is operated pulsed. 4. Adjusting device for automatic, computer-controlled positioning of the printing templates of a rotary screen printing machine with opto-electronic scanning of printing marks ( 14, 16 ) of different configurations attached to the printing templates ( 1 ), the electrical signal pattern of which is read in a computer (CPU 6 ). which recognizes the print mark pattern on the basis of preprogrammed logic and supplies control commands to servomotors ( 4 [X] , 5 [Y]) for axial and rotary and, if appropriate, radial adjustment of the respective printing template ( 1 ), characterized in that the optical measuring path ( 2 ) the optoelectronic scanning device ( 11, 12 ) penetrates the hollow cylinder wall of the respective printing template ( 1 ). 5. Adjusting device according to claim 4, characterized in that the transmitter element ( 11 ) of the opto-electronic scanning device's ( 2 ) outside and the Receiver element ( 12 ) is positioned within the respective printing template ( 1 ). 6. Adjusting device according to claim 5, characterized in that at least one of the two elements ( 11, 12 ) of the optoelectronic scanning device ( 2 ) can be moved transversely to the optical axis of the measuring section by small adjusting distances. 7. Adjusting device according to claim 4, characterized in that the optical measuring section of the opto-electronic scanning device ( 2 ) is operated with homogeneous, sharply bundled light, preferably with laser light. 8. Adjusting device according to claim 7, characterized records that the opto-electronic measuring section be pulsed is driven.