EP0488092B1 - Screen printer - Google Patents

Abstract

In a screen printer having at least one adjustably mounted screen (4, 4') and having known squeegee and path-guiding and transporting means, furthermore having a device for reading off register marks or the like for multi-colour printing, the displaceably mounted screen (4, 4') is connected to adjusting motors (9, 9', 9") which are controlled by at least one monitoring camera (5, 5', 7, 7') which reads off the register marks or colour displacements, its pulse generator controlling the adjusting motors (9, 9', 9") via a computer or the like (8). <IMAGE>

Description

The invention relates to a roller screen printing machine with at least one adjustably mounted screen, which has application devices and counterpressure devices as well as transport means for web guiding and surveillance cameras for reading registration marks or the like, servomotors for setting the at least one screen in the longitudinal and transverse directions are provided and the servomotors in turn are electrically connected to at least one surveillance camera for reading registration marks or the like, the pulse generator of which controls the servomotors via a computer or the like.

Screen printing machines which have such a possibility of adjusting the screens are known (EP-A 0 126 723). In such known screen printing machines, the screens are adjusted as a function of a corresponding specification. The registration accuracy is increased by the cameras, which may be provided in pairs at the inlet to a printing station. The target and actual positions of the material to be printed are determined at the input of a printing station and the target position of the servomotors is determined therefrom. According to the determined values, the servomotors are used to adjust the screen to increase the registration accuracy.

Based on this prior art, the invention has for its object to design a roller screen printing machine of the type presumed to be known so that it makes it possible to determine the accuracy with which printing is carried out in each printing station.

This object is achieved in that a pair of cameras for querying the markings before the printing process and a further pair of cameras for querying the markings after printing are provided in each printing station.

Such an arrangement of four cameras allows the printing accuracy to be determined in each printing station. It becomes possible to specify tolerances per printing station and to provide appropriate signals or markings when exceeded. This makes it possible to control the print quality separately in each individual printing station and not only at the end of the entire printing process. Furthermore, with such a roller screen printing machine, the screens can be set up automatically in each station.

Furthermore, it is an idea of the invention that all slides, in which the templates to be set lie, together, are connected via a push rod, the entire unit of carriage and stencils being able to be moved forward and backward, forwards and backwards. trained as a crank drive are movable.

This has the advantage that the entire system can be calculated, whereby each unit receives its special setting of the template with its slide on a computer.

The entire device can work variably, depending on which computer system is used and which accuracy is required in the first order, or how many color orders are run in succession.

It is important that through the cooperation of one or more cameras, connected with 1 plus x servomotors, - to fix the position of the stencil (s), - using one or more computers, the printing result can be achieved in an accuracy range that is far away from known results. Uncertainties from the transport of goods and from the goods themselves are excluded, or compensated or compensated for.

It is also essential that not only the incoming strand of the web that lies in front of the order area is checked, but that the outlet leg lying after the order is queried with two control cameras. Then the stencil has already applied the pressure, but the further orders in your own and next stencil can be corrected immediately.
Larger failures are avoided. For example, the last template basically didn't need any run-out cameras. However, they should work retrospectively, ie monitor your own template and control it if necessary, or evaluate the overall result.

It is also important that basic errors are taken into account in advance, namely processing errors of the counter-pressure roller, which belong to the range of the "difference value", and which must be prevented from the outset.
"Difference value" is understood to mean the length deviation between the original and the actual print. This is entered into the computer in the + or - direction. The pulse generator is used to evenly distribute the difference value over the entire print image. For example, if the difference is in the plus 0.10 and the pulse generator delivers 10 pulses for a print image, each correction is 0.01mm / pulse.

The invention is seen in the fully automatic print registration, which adjusts two or more stencils to the positional accuracy achieved in the stencil production for the respective print job.

Fig.1

die Seitenansicht einer Siebdruckstation,

Fig.2

die Draufsicht auf eine Schablone,

Fig.3

den Computer in Vorderansicht,

Fig.4

eine Draufsicht auf eine der Schablonen,im Einstellrahmen mit Stellmotoren und Kameras,

Fig.5

ein Antriebsschema in Draufsicht.

In the drawings, an embodiment of the invention is shown; show it:

Fig. 1

the side view of a screen printing station,

Fig. 2

the top view of a template,

Fig. 3

the computer in front view,

Fig. 4

a plan view of one of the templates, in the setting frame with actuators and cameras,

Fig. 5

a drive diagram in top view.

The fully automatic registration in the machine 1 shown should be able to apply at least two colors to one another in such a way that the register marks used are accurate to e.g. Stand +/- 0.05mm to each other. If no register marks are used, which may happen in special cases, the single point query should not show any major difference.

In order to achieve this, the position of the first printing ink must be recognized and the screen of the color to be applied next corrected before the further printing ink is applied.

The printing station 2 shown, in the screen printing machine 1 shown only partially in FIG. 1, preferably has two cameras 5, 5 'lying parallel to one another in the inlet of the web 3 below the screen 4. In the exemplary embodiment shown in FIG. 1, these are located in front of an impression cylinder 6 which has suction holes 16.
A sieve frame 4 'carries the sieve 4, and lies in a longitudinally and transversely movable carriage 44. This carriage 44 is in turn supported in a support frame 40 which carries the servo motors 9, 9', 9 '' which move the carriage 44.

• a) den Kameras 5,5' zur Abfrage der Markierungen vor dem Druck, z.B. beim 2.od.x. Durchgang, und
• b) den Kameras 7,7' zur Abfragung der Markierungen nach dem Druck, als Kontrollangabe.

Die Kameras wirken jeweils, vorzw. über den Rechner 8,auf Verstell- bzw. Einstellmittel der Schablone.
Das Registriersystem schließt somit auch die jeweils dem Sieb 4 zugeordneten und mit dem Kamera-Computersystem verbundenen Stellmotore 9,9', und 9'' ein und zwar,

• a) zwei Stellmotore 9,9' zur Einstellung der Siebes in oder entgegen der Laufrichtung der Bahn, (A-B)
• b) einem Stellmotor 9''zur Einstellung des Siebes quer zur Laufrichtung der Bahn, somit siehe (C-D)

Es wird jeweils der Schlitten 44 eingestellt, in dem die Siebschablone mit ihrem Rahmen 4' liegt.
Ferner gehört zum Erfindungsgegenstand der Rechner oder Computer 8, vorzugsweise mit zwei Bildschirmen 8',8'' und der Eingabe- und Korrekturtastatur 80. Daß jeweils Verbindungsmittel 18 vorgesehen sind,ist selbstverständlich.
So sind die Kameras mit dem Rechner und dieser mit den Stellmotoren verbunden und reagieren jeweils gegenseitig auf Signale, die vorzw. über den Rechner kommen.
Der Rechner 8 selbst, bekommt Signale und Voreingaben.In order to check in each case whether the print job carried out is also set up exactly, another check is carried out in the area of the running strand of the material web 3, that is to say behind the counter-pressure cylinder 6, namely by two further cameras 7.7 'which are arranged next to one another, preferably at the same height, are assigned to the running path.
If the correction is incorrect, the correction system is activated via the computer or computer 8 so that the color or the like is applied exactly the next time the print is made.
Thus, in the exemplary embodiment shown, there are two pairs of control cameras each, namely a pair of cameras 5,5 'in the inlet and the second pair of cameras 7,7' in the path 3. (See Figs. 3 and 4)
Thus, the registration system consists of

• a) the cameras 5,5 'for querying the markings before printing, for example in the 2.od.x. Passage, and
• b) the cameras 7, 7 'for querying the markings after printing, as control information.

The cameras work, mainly via the computer 8, on the adjusting means of the template.
The registration system thus also includes the servomotors 9, 9 'and 9''assigned to the screen 4 and connected to the camera computer system.

• a) two servomotors 9.9 'for setting the sieve in or against the running direction of the web, (AB)
• b) a servomotor 9 '' for setting the screen transversely to the running direction of the web, thus see (CD)

The carriage 44 is set in each case, in which the screen template lies with its frame 4 '.
Furthermore, the subject of the invention includes the computer or computer 8, preferably with two screens 8 ′, 8 ″ and the input and correction keyboard 80. It is self-evident that connection means 18 are provided in each case.
So the cameras are connected to the computer and this to the servomotors and each react to signals that come over the computer.
The computer 8 itself receives signals and pre-inputs.

As can be seen in FIG. 1, the connection between screen printing machine 1 and computer 8 can take place via cable 18 if one does not prefer a radio connection.
Furthermore, the mounting of the screen template 4 with its screen frame 4 'is shown in FIG. 1, the screen or template frame 4' in turn being fitted into a carriage 44 which bears against the servomotors 9, 9 ', 9''.

The servomotors 9, 9 ', 9''are designed as stepper motors.
The number of steps / revolution can be, for example, 1000 / 1U, so that an exact correction of the position of the screen template can be carried out in the longitudinal and / or transverse direction. The servomotors 9.9 ', 9''are firmly attached to the support frame 40. Depending on the specification of the computer 8 and the reading modalities of the camera pairs 5.5' and 7.7 ', they are actuated in order to set the screen printing stencil precisely for everyone to ensure individual pressure.

The impulses for the servomotors 9, 9 ', 9''come from the computer 8, its parameters entered and the data determined by the cameras about the deviations which define the two axes for the setting of the template. The actuators or stepper motors work precisely.
The template frame 4 'is inserted into the carriage 44. Springs 11 ensure that a cross bar 41 of the slide 44 is pressed evenly onto the servomotors.
This is a guarantee that the work of the servomotors, which are designed as stepper motors, is transferred exactly to the stencil and that their position during printing is guaranteed.
The stepper or servo motors 9 and 9 'pull the stencil in the running direction of the web 3 to be printed, and possibly unequal to the small angular position, if necessary, and the stepper or servo motor 9''is on a protruding finger 14 of the Carriage 44 attached and pulls or pushes the template 4, respectively. whose frame 4 'in the transverse direction to the web guide.

Another correction option than the reading of registration marks or the like. is the mentioned correction for the "difference path", which has already been described. This compensation can then also be carried out by controlling the screen template, but not by the respective impulses from the camera input on the stepper motors, but, as mentioned, is entered as a value directly in advance into the computer or computer. This computer or computer then continuously controls the screen with the entered value by moving it in the printing phase, according to the value, in the printing direction or also against the printing direction. The impression cylinder also makes the correspondingly larger or smaller angle adjustment in the transport direction of the web. This compensates for errors that e.g. caused by shrinkage or stretching of the material to be printed. This is always the same for every print stroke of an order.

Solche Zusatzbewegungen mit dieser Präzision sind nur über die Rechner- bzw. Computersteuerung möglich. Dies ist die Vorabeingabe jeder Druckfolge und wichtig, insbesondere wenn hochqualifizierte Drucke, z.B Leiterplatten gedruckt werden sollen, was vielfach geschieht.2 shows an example for the compensation of the differential path:
The area "a" in the screen printing stencil 4 drawn corresponds to the actual printing, for example 299 mm.
The template is 1 mm larger, for example, 300 mm and thus the area "b" is the processing error or the "difference value" of 1 mm.
This value is measured and entered once.
The pressure cylinder 6 is connected to a pulse generator 16 which emits, for example, 1 pulse / 10 mm.
The printing cylinder therefore continues to rotate and the screen must always be shifted, for example, by 1 mm additionally in or against the printing direction, respectively after

$\text{10 mm by 1/300 x 10 = 0.033mm}$

Such additional movements with this precision are only possible via the computer or computer control. This is the default input for each print sequence and is important, especially if high-quality prints, eg printed circuit boards, are to be printed, which often happens.

4 shows the mounting of the screen template 4 with its frame 4 'and the adjustment frame or slide 44. As mentioned, the stencil frame 4 'lies in the carriage 44 and by moving it by means of the actuating or stepping motors 9, 9', 9 '', the lateral adjustment or displacement and also the forward and return movement are effected, the stepping motors , as mentioned, can be controlled by the computer 8. This is supplied with data even by the camera pairs 5.5 'and 7.7'.
The data is thus determined before the run-in and after the paint application.
At the first print, only the registration marks are checked and the difference value is taken into account. The second and subsequent pressure is carried out in the stations by the displacement of the carriage in which the templates are located, based on the camera values determined, exactly by the servomotors 9, 9 ', 9''controlled by the computer 8.
Possibly. Errors are immediately detected and immediately avoided without rejects being produced continuously.
This idea of fully automatic print registration can be realized on single-station printers where the web is run several times and also in multi-color screen printing machines.
If two cameras 5.5 'and 7.7' are shown in the example, this is very advantageous, with only one camera in the inlet leg and one in the outlet leg of the web, the detection of possible angular errors is missing.
5 shows a drive diagram for three stations. A push rod 13 moved via a rocker arm 12 takes all the desired stations evenly, in each station the position of the template is separated from the cameras and the computer 8. regulated about the displacement of the carriage 44.
The idea of the invention is not limited to the exemplary embodiment shown, so variations are conceivable and possible.

The different characteristics are therefore variable.
For example, the screen printing machine can have only one station through which it is driven several times, or a number of stations, possibly with intermediate drying.
That must be left to the circumstances.
It is advantageous to equip each station with the monitoring device described, or according to the circumstances.
The computer or computer is also freely selectable, with or without screens 8 ', 8'', and with or without a display 81, which monitors control of the activation of the cameras and the motors, or monitors other functions of the machine.

Reference list

1

Screen printing machine

2nd

Printing station

3rd

Goods train, train

4th

Screen template

4 '

Screen frame

40

Support frame

41

Cross bar of the sled

44

carriage

5.5 '

Camera pair

6

Impression cylinder

7.7 '

Camera pair

8th

Calculator, respectively computer

8 ', 8' '

Screens

80

Input and correction keyboard

81

Display of the calculator

9.9 ', 9' '

Servomotors

11

Springs, spring balancing for sledges

12th

Swing arm for crank drive

13

Push rod,

14

Finger for actuator 9 ''

16

Suction holes

18th

Connection means, such as cables or the like.

Claims (9)

1. A roller screen printing machine having at least one adjustably located screen, which features coating devices and counter-pressure devices and means for conveyance for the guidance of the sheeting and monitoring cameras for scanning of register marks or the like, whereby actuator motors are provided for the setting of at least one screen in longitudinal and transverse direction and the actuator motors for their part are connected electrically to at least one monitoring camera for scanning of register marks or the like, the pulse generator of which controls the actuator motors via a computer or the like,
   characterised in,
   that at each printing station (2) in each case a pair of cameras (5; 5') is provided for scanning the marks prior to the printing operation and another pair of cameras (7, 7'') is provided for scanning the marks after printing.
2. An arrangement according to claim 1, characterised in that the screen template(s) (4) lie with their template frames (4') in a setting frame or in a carriage slide (44) and are monitored in same and are arranged to be able to be slid by processor control.
3. An arrangement according to claim 1 or 2, characterised in that a plurality of screen templates 94) lying preferably in their carriage slides (44) or the like, are mutually interconnected by means of a push rod (13) and the entire unit can be moved by an oscillating crank (12) or a crank drive mechanism.
4. An arrangement according to one or several of the claims 1 - 3, characterised in that at least one camera is arranged and is connected to the processor (8) in such a manner that a feed section or discharge section of the guidance of the sheeting prior to or after the application zone can be scanned by the camera.
5. An arrangement according to any of the claims 1 - 4, characterised in that the setting frame or carriage slide (44) is connected to the actuator motors (9,9' 9'') for the movement with the template (4) in longitudinal direction and / or transverse direction.
6. An arrangement according to one or several of the claims 1 - 5, characterised in that the actuator motors provided for pushing the screen template are arranged in such a manner that two separate operating actuator motors (9, 9'') control the screen template in the direction of conveyance (A - B) and return of the sheeting, or to an angular position and at least one actuator motor (9'') controls the transverse direction (C - D).
7. An arrangement according to claim 6, characterised in that a finger (14) is provided on the screen template (4') or its carriage slide 944) to which the actuator motor (9'') is fixed for transverse direction of the template.
8. An arrangement according to one or several of the claims 1 - 7, characterised in that a differential value switching circuit is provided for the actuator motor (9, 9'') in the computer or processor (8).
9. An arrangement according to one or several of the claims 1 - 8, characterised in that the carriage slide (44) is subjected to a spring tensioner (11) on the actuator motors (9' 9'') and can be skewed in the plane of the screen.

Images