Method for a computer to control a screen printing machine, computer-controlled screen printing machine

Abstract

The present invention relates to a computer-implemented method for controlling a screen printing machine, wherein the method comprises screen printing a printing paste with a squeegee lip of the screen printing machine through a screen of the screen printing machine to produce a printed layer formed by the printing paste on a substrate, wherein the squeegee is moved along the X-axis at a working speed by at least one squeegee drive of the screen printing machine, is oriented at a working angle with respect to the Z-axis, and prints onto the screen along the Y-axis with a working force. The method comprises: automatically determining, after printing a plurality of printed layers, the area of the contact surface of the squeegee lip with the screen by means of at least one sensor and, after the determination, automatically resetting the working force according to the area for setting a preset desired pressing force of the squeegee lip onto the screen. The present invention also relates to a computer-controlled screen printing machine.

Description

Field of the Invention

[0001] The present invention relates to a computer-implemented method for controlling a screen printing machine according to the preamble of claim 1 and to a computer-controlled screen printing machine according to the preamble of claim 10. Background Art

[0002] Multiple types of screen printing methods and screen printing machines are known from the prior art.

[0003] In known screen printing machines, settings that are important for the printing result, such as the speed of the squeegee, the pressing force, or the mounting angle, are set manually and adjusted if necessary based on visual control of the printed pattern, where the squeegee prints the printing medium through the screen onto the substrate to be printed. As a result, the printed coating is neither sufficiently uniform nor fully reproducible for functional applications, such as printed batteries, screens, photovoltaic modules, or heating modules.

[0004] In known screen printing machines, the rubber lip at the end of the squeegee is fully utilized during operation, such that the shape and area of the bearing surface change, where the printing medium is printed through the screen by means of the squeegee. As a result, the pressing force of the squeegee onto the screen and thus the thickness and quality of the printed layer also change.

[0005] Patent application WO2012164223A2 describes a screen printing machine and a screen printing method. The screen printing method includes checking the printing result by means of an inspection device in order to control the parameters of the screen printing machine based on the inspection result. As the sole control method, WO2012164233A2 discloses an optical inspection of the printing result, such that functionalized printed products, such as electronic devices, cannot be comprehensively controlled. In addition, WO2012164233A2 also does not disclose how the input parameters are processed in order to control the printing process.

[0006] Patent application EP1080889A2 describes a screen printing method, where the pressure can be set during the printing process, by means of which the printing paste is discharged from the print head. The pressure can in particular be adjusted based on the inspected printing result, where the inspection is also an optical inspection in this case. Similarly, the movement speed of the print head or the screen can also be set. In addition to the discharge pressure and movement speed of the print head and the screen, EP1080889A2 does not describe the parameters of the printing process that are automatically controlled.

[0007] Patent application WO2014080010A1 describes a screen printing machine having a sensor system for determining the pressure acting on a substrate during the printing process. The pressure on the substrate can be kept constant, for example, by automatically adjusting the pressing force of an imprinting tool, such as a squeegee. In particular, in the case of an elastically deformable and thin substrate, such as a film, the measurement of the pressure acting on the substrate is however technically costly to configure.

[0008] Patent application WO2006091845A2 describes a screen printing machine comprising a fluid transfer member having holes. The printing machine may also include a squeegee. The position of the squeegee relative to the fluid transfer member can be configured such that it is set according to the judgment of the user of the device. Thus, WO2006091845A2 only discloses a printing machine in which the squeegee position can, at best, be manually adjusted by the user. Manual adjustment is however usually carried out too late and is imprecise, so that a high-quality printing result cannot be reliably achieved thereby.

[0009] Document EP2999595B1 discloses a device for manufacturing three-dimensional screen printing. The device can be equipped with a non-contact measuring device by means of which the position and pressure ratio of the pressing and flood squeegee lower edges are detected and evaluated and the measurement results can be incorporated into the setting of the squeegee position, in particular for squeegee control, in order to ensure a parallel orientation of the squeegee relative to the screen cloth. The determination and adjustability of the squeegee position are mainly used for the 3D printing function of the device and may not result in a great quality advantage when manufacturing flat prints. Summary of the Invention

[0010] The object of the present invention is to provide a simply implemented method for controlling a screen printing machine and a low-cost screen printing machine in order to print functional layers effectively, reliably and with high precision.

[0011] The subject matter of the present invention provides a method according to claim 1, which method achieves the technical object. Similarly, the object is achieved by a screen printing machine according to claim 10. Advantageous design options result from the dependent claims.

[0012] The computer-implemented method according to the present invention includes the control of a screen printing machine having at least one screen, at least one squeegee, at least one squeegee drive and at least one computer device for controlling the screen printing machine, wherein the squeegee has a squeegee lip fixed to a tube plate, wherein the squeegee lip includes a contact surface having an area in contact with the screen, and the squeegee drive is for translating the squeegee relative to the screen along an X-axis parallel to the screen and along a Z-axis perpendicular to the screen and for rotating the squeegee relative to the screen about a Y-axis perpendicular to the X-axis and the Z-axis.

[0013] The aforementioned components of the screen printing machine can for example be constructed and connected to each other as in a conventional screen printing machine. In addition, the screen printing machine can have other components which are in particular known from conventional screen printing machines in terms of their construction and their function.

[0014] The screen printing machine includes at least one sensor which is connected in terms of communication to a computer device, the sensor being used to determine the area of the contact surface of the squeegee lip.

[0015] The method includes printing a printing paste through a screen by means of a squeegee lip for producing a printed layer from the printing paste on a substrate, wherein the squeegee is moved along the X-axis at a working speed, oriented at a working angle relative to the Z-axis, and pressed onto the screen along the Y-axis with a working force.

[0016] The printing is preferably repeated several times in order to construct a layer consisting of a plurality of printed layers on the substrate. The layer can for example include a functional layer of a printed electronic component, for example a dielectric layer of a printed capacitor.

[0017] The method preferably includes automatically determining the area of the contact surface of the squeegee lip by means of at least one sensor after printing a plurality of printed layers, and after the determination, automatically resetting the working force again according to the area for setting a preset desired pressing force of the squeegee lip onto the screen.

[0018] In the simplest case, the reset working force corresponds to the product of the desired pressing force and the area, supplemented with other parameters if necessary, the parameters being obtained for example from the deformation of the squeegee lip which may occur during printing. The other parameters can be determined and / or calculated for a given pressure setting as well as the properties and geometry of the squeegee lip, for example by calibration.

[0019] Keeping the desired pressing force as accurate as possible is very important for a high-quality printing result, because on the one hand the pressing force must at all times be large enough to press the printing paste with a preset mass flow density through the screen so that a defect-free printed layer is produced. A defect-free printing is particularly important when manufacturing functional layers, because defects can cause functional losses, for example due to corrosion in the case of defects in the anti-corrosion protection layer or by short circuits in the case of defects in the electrical insulation layer.

[0020] On the other hand, however, the pressing force is not too high either, because otherwise an increased wear of the squeegee and / or the screen is caused. In addition, too high a pressing force damages the already printed printed layer and / or the substrate, which is particularly problematic when printing functional layers and / or using sensitive substrates, such as films.

[0021] During the process of the method, the determination and the resetting are preferably carried out several times, respectively after printing a particularly constant number of printed layers.

[0022] The number of printed layers to be printed before automatic determination can be selected according to the printing settings and the material properties of the squeegee lip, the printing paste, and the screen, such that determination is made once there is a significant change in the expected area and thus significant wear of the squeegee lip. Thereby, undetected wear of the squeegee lip that may damage the printing quality is prevented. On the other hand, the number of printed layers should not be selected to be so small that determination is made before a significant change in area, so that the printing process is not interrupted unnecessarily often for determination.

[0023] The area can be stored together with the number of printed surfaces to be printed, preferably together with other parameters of the method, such as the material properties of the squeegee lip, the printing paste, and / or the screen, the working speed, the working angle, and / or the working force. Thereby, the wear of the squeegee lip can be recorded. In addition, it can be automatically announced when the squeegee lip may have to be replaced based on the wear so far, so that a replacement squeegee lip can be provided in a timely manner.

[0024] The number of printed layers can also be automatically adjusted from the stored development of the area, and the next determination is made according to the above-mentioned number of printed layers, such that the next determination is made once there is a significant change in the expected area and thus significant wear of the squeegee lip.

[0025] The method preferably includes automatically adjusting the working angle to a preset angle range once the area exceeds the maximum area, and automatically resetting the working force after the adjustment to set the desired pressing force. The adjustment and reset can be performed multiple times during the process of the method, always when the area exceeds the maximum area.

[0026] The adjustment prevents having to apply a very large force to maintain the desired pressing force due to an overly large area, which increases the energy consumption and wear of the squeegee drive and may damage the squeegee drive. In addition, more uniform wear of the squeegee lip is achieved through the adjustment, so that the squeegee lip can be used for a longer time, and / or a softer squeegee lip can be used to protect the screen and / or the substrate.

[0027] After the adjustment, a new edge of the squeegee lip with a reduced area is provided for further printing. Therefore, the working force must be reset in order to continue to cause the desired pressing force. In the simplest case, the working force is reset to the initial force at the start of printing.

[0028] The automatic adjustment of the working angle is preferably performed in a first direction until the working angle passes through a first limit angle. When passing through the first limit angle, the working angle is preferably automatically reset to the initial angle at the start of printing. The automatic adjustment is preferably performed in a second direction opposite to the first direction after resetting the working angle until the working angle passes through a second limit angle.

[0029] The limiting angle is advantageously selected such that the squeegee is oriented relative to the screen sufficiently inclined between the limiting angles so as to reliably press the printing paste through the screen with a preset mass flow density. If the squeegee is oriented too gently relative to the screen, there is a risk that not a sufficient amount of printing paste is present between the squeegee lip and the screen at the contact surface to enable defect-free printing.

[0030] By adjusting the working angle first in a first direction and then starting from an initial angle in a second direction, the squeegee lip can be optimally utilized to the fullest extent, such that the squeegee lip can be used for a particularly long time and / or can be particularly soft.

[0031] Automatically determining the area preferably includes: automatically determining the abrasion thickness of the squeegee lip by means of at least one sensor, and automatically calculating the contact surface from the abrasion thickness and the original shape of the squeegee lip. In a known, for example, square original shape, the area can be calculated in a simple way by trigonometry from the working angle of the squeegee lip, the original shape, and the abrasion thickness.

[0032] According to the invention, the abrasion thickness is understood as the thickness of the material removed perpendicular to the contact surface by printing from the squeegee lip relative to the original dimensions of the squeegee lip. The terms original shape and original dimensions relate to the shape and dimensions of the squeegee lip before it is used in the process and thus wears.

[0033] The area can also be determined directly, for example, by means of an imaging sensor and automatically measuring the image taken by the sensor, for example, by means of automatic object detection. Since the contact surface is however usually not significantly different in terms of color and structure from the surrounding squeegee lip, the automatic measurement of the image of the contact surface is technically costly and unreliable.

[0034] In contrast, the abrasion thickness can be precisely determined by means of a technically simple mechanism, for example, by means of an imaging sensor and by automatically measuring the pictures taken by the sensor of the sides of the squeegee lip oriented along the X-axis and the Z-axis, for example, by means of an automatic object recognition device. A particularly simple and precise determination of the abrasion thickness can be achieved by mounting length-readable on the sides of the squeegee lip. To be able to display the abrasion thickness independently of the working angle, the length-readable can be formed by an arc that connects points at the same spacing to the original corners of the side designed for contact with the screen to each other.

[0035] Automatically determining the abrasion thickness preferably includes: automatically measuring the reference spacing of the squeegee lip by means of at least one sensor in the case of a known reference abrasion thickness of the squeegee lip, especially at the start of printing or directly after adjusting the working angle, and if the reference abrasion thickness is zero, automatically measuring the spacing of the squeegee lip by means of at least one sensor, and automatically calculating the abrasion thickness from the reference abrasion thickness, the reference spacing, and the spacing.

[0036] Automatically measure a reference spacing, and preferably the squeegee is oriented relative to the Z-axis at a reference measurement angle, and automatically measure a spacing, and preferably the squeegee is oriented relative to the Z-axis at a measurement angle.

[0037] The reference measurement angle preferably corresponds to the measurement angle. In this case, the reference spacing and the spacing can be measured in a simple manner by means of the same sensor without having to move the sensor for this purpose and the abrasion thickness can be calculated particularly simply as the difference between the reference spacing and the spacing.

[0038] The reference angle and / or the measurement angle preferably correspond to the working angle. From this, the advantage results that no angle adjustment is required in order to measure the reference spacing and / or the spacing. Angle adjustment requires additional time and when the angle adjustment is not precise enough, measurement errors are induced. Particularly preferably, the reference angle and the measurement angle correspond to the working angle.

[0039] The reference angle and / or the measurement angle can be different from the working angle, for example so that at least one sensor can be mounted at an easily accessible location of the screen printing machine. For example, the reference angle and / or the measurement angle, in particular the reference angle and the measurement angle, differ from the working angle by 180°. From this, the advantage results that at least one sensor can be mounted on the side of the squeegee facing away from the screen. This area of the screen printing machine is usually easily accessible.

[0040] The measurement of the reference spacing and / or the spacing is preferably carried out along the Z-axis because the precise orientation of the measurement direction is technically simply implemented along the usually vertical Z-axis.

[0041] The measurement of the reference spacing and / or the spacing is preferably carried out during the rotation of at least one squeegee by means of at least one squeegee drive in an angular interval about the Y-axis. The reference spacing and / or the spacing can be calculated from the resulting spacing curve within the angular interval without the need for an exact angular positioning of the squeegee. In addition, the shape of the squeegee lip can also be determined in this way in order to be able to monitor its wear more accurately. The shape of the squeegee lip can also be determined, for example, by means of a spacing measurement using a scanner, in particular a laser scanner.

[0042] The method preferably includes automatically controlling at least one physical property of the layer printed on the substrate with the screen printing machine by means of a control device of the screen printing machine, and automatically adjusting the working force, the working angle and / or the working speed of the squeegee and / or the screen spacing between the screen and the substrate when the physical property differs from the associated desired property.

[0043] By combining automatic control in the method, the method parameters can be quickly and automatically adjusted when the printed layer differs from its desired properties, in order to avoid incorrect printing. This is particularly important in the case of functional layers, since functional failures of the layer result in high subsequent costs.

[0044] The physical properties preferably include the layer thickness of the layer along the Z-axis, the conductivity of the layer along the Z-axis and / or the specific resistance of the layer and / or the uniformity of the layer thickness and / or the conductivity along the XY plane spanned by the X-axis and the Y-axis.

[0045] The physical properties mentioned are particularly important especially when manufacturing electronic functional layers, such as capacitor layers, electroluminescent layers or resistor layers or insulating layers.

[0046] The invention relates to a computer-controlled screen printing machine for carrying out the method according to the invention, the screen printing machine having at least one screen, at least one squeegee, at least one squeegee drive, at least one computer device for controlling the screen printing machine, wherein the squeegee has a squeegee lip fixed to the squeegee, the squeegee lip comprising a contact surface having an area for contacting the screen, the squeegee drive being for translating the squeegee relative to the screen parallel to the X-axis of the screen and along the Z-axis perpendicular to the screen and for rotating the squeegee relative to the screen about the Y-axis perpendicular to the X-axis and the Z-axis.

[0047] The aforementioned components of the screen printing machine can for example be constructed and connected to one another as in a conventional screen printing machine. In addition, the screen printing machine can have other components which are known especially from conventional screen printing machines in terms of their construction and their function.

[0048] The screen printing machine includes at least one sensor communicatively connected to the computer device for determining the area of the contact surface of the squeegee lip. The advantages of the determination of the area have been described in detail above for the method according to the invention.

[0049] At least one sensor preferably includes a distance sensor, particularly preferably a laser distance sensor, for measuring the distance between the contact surface and at least one sensor. With the aid of the distance sensor, the area can be determined precisely in a simple manner as described above for the method according to the invention. The laser distance sensor allows particularly high accuracy here.

[0050] At least one sensor can include an imaging sensor, in particular a camera. With the aid of the imaging sensor, the area can be determined by the method described above for the method according to the invention.

[0051] At least one sensor is preferably designed for distance measurement on at least two regions of the squeegee lip that are spaced apart from each other along the Y-axis. For example, when the squeegee is not accurately installed in the screen printing machine in its preset position, uneven wear of the squeegee lip along the Y-axis may thereby occur. By measuring in at least two regions, this uneven wear can be automatically determined. Subsequently, for example, the position of the squeegee can be automatically corrected and / or an alarm can be sent to the user of the screen printing machine.

[0052] Generally, the uneven wear of the squeegee lip along the Y-axis extends linearly. Therefore, generally, it is sufficient to provide distance measurement on just two spaced-apart regions.

[0053] For distance measurement in at least two regions, the screen printing machine includes, for example, at least two sensors that are spaced apart from each other along the Y-axis.

[0054] The screen printing machine preferably includes: a screen drive communicatively connected to a computer device for translating the screen along the Z-axis relative to the substrate; a printing plate drive communicatively connected to the computer device for translating the printing plate that houses the substrate to be printed along the X-axis relative to the screen; at least one flood squeegee for dispensing printing paste onto the screen; and a flood squeegee drive communicatively connected to the computer device for translating the flood squeegee relative to the screen along the X-axis and along the Z-axis and for rotating the flood squeegee relative to the screen about the Y-axis and / or at least one frame that bears at least one squeegee and at least one flood squeegee and a frame drive communicatively connected to the computer device, the frame drive being for translating the frame relative to the screen along the Z-axis.

[0055] The main functions of the screen printing machine can be automatically controlled by the computer device through one, several, or all of the aforementioned drives. Thereby, a more precise and reliable control can be achieved as compared to conventional screen printing machines, in which the functions are at least partially manually controlled. In particular, for printing functional layers, it is necessary to position the individual printed layers very accurately relative to each other and to have a high printing quality for the individual printed layers, which is generally not achievable with conventional screen printing machines.

[0056] At least one squeegee drive, screen drive, printing plate drive, flood squeegee drive, and / or frame drive preferably includes a plurality of motors communicatively connected to the computer device, preferably servo motors. Particularly preferably, each of the aforementioned drives respectively includes a plurality of motors communicatively connected to the computer device, especially servo motors. The motors have the advantage of positioning the driven member more precisely as compared to the hydraulic drives used in conventional screen printing machines.

[0057] The servo motor has special advantages. The servo motor enables precise control of the angular position, rotational speed, and acceleration of its motor shaft through an integrated position sensor.

[0058] The screen printing machine preferably includes at least one control device communicatively connected to a computer device, the control device being configured to control at least one physical property of the layer printed onto a substrate with the screen printing machine. The physical property preferably includes the layer thickness of the layer along the Z-axis, the conductivity of the layer along the Z-axis and / or the specific resistance of the layer and / or the uniformity of the layer thickness and / or the conductivity along the XY plane spanned by the X-axis and the Y-axis.

[0059] The advantages of the control are described above for the method according to the invention.

[0060] To measure the layer thickness and / or the uniformity of the layer thickness, the control device can for example include at least one distance sensor, interferometer, profilometer, and / or camera system.

[0061] At least one control device can for example be designed to measure the specific resistance according to the four-point method and / or according to the van der Pauw measurement method. Description of the Drawings

[0062] Other advantages, objects, and features of the invention are set forth in the following description and drawings, in which articles according to the invention are shown by way of example. Features that are at least substantially identical in their functional aspects in the drawings can be denoted by the same reference numerals herein, where these features do not have to be numbered and described in all of the drawings.

[0063] Figure 1 A schematic perspective view of a screen printing machine according to the invention is shown.

[0064] Figure 2 Shown Figure 1 A schematic perspective view of the printing plate of the screen printing machine in

[0065] Figure 3 A schematic sectional view of the squeegee of the screen printing machine according to the invention is shown.

[0066] Figure 4 Shown Figure 3 Another schematic sectional view of the squeegee in

[0067] Figure 5 A schematic view of a method for controlling a screen printing machine according to the invention is shown. Detailed Description

[0068] Figure 1Shows a schematic perspective view of a screen printing machine 100 according to the present invention, the screen printing machine having: at least one screen 120; at least one squeegee 110 having a squeegee lip 111 fixed to the squeegee, wherein the squeegee lip 111 includes a contact surface having an area for contacting the screen 120; at least one squeegee drive 130 for translating the squeegee 110 relative to the screen 120 along an X-axis X parallel to the screen 120 and along a Z-axis Z perpendicular to the screen 120 and for rotating the squeegee 110 relative to the screen 120 about a Y-axis Y, wherein the Y-axis Y is perpendicular to the X-axis X and the Z-axis Z; and at least one computer device 140 for controlling the screen printing machine 100.

[0069] For this purpose, the computer device 140 is communicatively connected to the remaining components of the screen printing machine 100 wirelessly or wiredly. The communication connections are not shown for the sake of clarity.

[0070] The squeegee drive 130 includes, for example, four electric motors 130A, 130B, 130C, 130D. For example, two of the electric motors 130A, 130C are used to vertically translate the squeegee 110 along the Z-axis Z, another electric motor 130B is used to rotate the squeegee 110 about the Y-axis Y, and another electric motor 130D is used for the horizontal translation of the squeegee 110, and preferably also the flood squeegee 170 of the screen printing machine 100 is translated along the X-axis X.

[0071] The screen printing machine 100 preferably includes a screen drive 121 communicatively connected to the computer device 140 for translating the screen 120 relative to the substrate along the Z-axis Z.

[0072] The screen printing machine 100 preferably includes a flood squeegee 170 for dispensing printing paste onto the screen 120 and a flood squeegee drive 171 communicatively connected to the computer device (140), the flood squeegee drive being for translating the flood squeegee 170 relative to the screen 120 along the X-axis X and along the Z-axis Z and for rotating the flood squeegee 170 relative to the screen 120 about the Y-axis Y.

[0073] The flood squeegee drive 171 includes, for example, three electric motors 171A, 171B, 171C. For example, 2 of the electric motors 171A, 171C are used to vertically translate the flood squeegee 170 along the Z-axis Z and another electric motor 171B is used to rotate the flood squeegee 170 about the Y-axis Y.

[0074] The screen printing machine 100 preferably includes a frame 180 carrying at least one squeegee 110 and at least one flood squeegee 170 and a frame drive 181 communicatively connected to the computer device 140, the frame drive being for translating the frame 180 relative to the screen 120 along the Z-axis Z.

[0075] The screen printing machine 100 may further include a printing plate for accommodating a substrate to be printed. For the sake of overview, the substrate is shown separately in Figure 2 it.

[0076] Figure 2 Shown Figure 1 is a schematic perspective view of the printing plate 160 of the screen printing machine 100 in it. The screen printing machine 100 preferably includes a printing plate driver 161 communicatively connected to a computer device 140. The printing plate driver 161 is used to translate the printing plate 160 along the X-axis relative to the screen 120.

[0077] In the printing plate 160, for example, at least one sensor 150 communicatively connected to the computer device 140 may be provided, in particular two sensors 150 spaced apart from each other along the Y-axis Y, for determining the area of the contact surface of the squeegee lip 111.

[0078] The sensor 150 may be configured as a distance sensor, in particular a laser distance sensor, for measuring the distance between the contact surface and each sensor 150.

[0079] In the shown arrangement of the sensor 150 in the printing plate 160, the sensor 150 is designed, for example, for vertical distance measurement along the Z-axis Z upward.

[0080] During printing, the squeegee 110 is oriented at a working angle relative to the Z-axis Z, and the surface normal of the contact surface of the squeegee lip 111 is oriented downward along the Z-axis Z. Thus, distance measurement can be performed relative to the Z-axis Z at the measurement angle or reference measurement angle of the squeegee 110, and the measurement angle or reference measurement angle corresponds to the working angle. Therefore, angle adjustment is necessary, which takes additional time and may be a source of measurement error.

[0081] Alternatively, the sensor 150 may also be provided at another position, for example, arranged vertically downward in the measurement direction above the squeegee.

[0082] Figure 3 is a schematic sectional view of the squeegee 110 of the screen printing machine 100 according to the present invention along the X-Z plane. The squeegee 110 is oriented at a working angle α relative to the Z-axis Z for printing and moves along the X-axis X on the screen 120.

[0083] This causes wear of the squeegee lip 111 of the squeegee. The wear is from an original shape such as a square (shown by a solid line) to a shape where the material of the squeegee lip 111 is abraded perpendicular to the contact surface 112 in contact with the screen 120 by an abraded thickness d (shown by a dotted line).

[0084] The area of the contact surface 112 can be calculated trigonometrically from the abrasion thickness d and the working angle α when the original dimensions of the known squeegee lip 111 are available.

[0085] At least one sensor 150, such as a laser distance sensor, can be mounted, for example, on the side of the squeegee 110 facing away from the screen 120 in order to measure the distance between the contact surface 112 and the sensor 150 for calculating the abrasion thickness. There is usually sufficient structural space on the side facing away from the screen 120 to accommodate the sensor 150 and the sensor 150 is, for example, easily accessible for maintenance work.

[0086] Figure 4 Show Figure 3 A schematic sectional view of the squeegee 110 along the X-Z plane is shown. The squeegee 110 is oriented, for example, at a measurement angle β relative to the Z-axis Z in order to measure the distance between the contact surface 112 and the sensor 150, where the measurement angle β, for example, differs from the working angle α by 180°. Thereby, the distance s can be measured along the Z-axis Z from the sensor 150 to the screen 120. The corresponding orientation of the sensor on the Z-axis can be set particularly simply.

[0087] Figure 5 A schematic view of a method for controlling a screen printing machine according to the invention is shown, the screen printing machine having: at least one screen; at least one squeegee having a squeegee lip fixed to the squeegee, wherein the squeegee lip includes a contact surface having an area for contacting the screen; at least one squeegee drive for translating the squeegee relative to the screen along an X-axis parallel to the screen and along a Z-axis perpendicular to the screen and for rotating the squeegee relative to the screen about a Y-axis perpendicular to the X-axis and the Z-axis; at least one computer device for controlling the screen printing machine; and at least one sensor communicatively connected to the computer device for determining the area of the contact surface of the squeegee lip.

[0088] The method includes printing 210 printing paste with the squeegee lip through the screen of the screen printing machine to produce a printed layer composed of the printing paste on a substrate, wherein the squeegee is moved along the X-axis at a working speed, oriented at a working angle relative to the Z-axis Z, and printed onto the screen along the Y-axis with a working force.

[0089] The method 200 shown includes automatically determining 220 the area of the contact surface after printing 210 a plurality of printed layers and, after the determination 220, automatically resetting 230 the working force again according to the area for setting a preset desired pressing force of the squeegee lip onto the screen.

[0090] In particular, the determination 220 and the resetting 230 are usually carried out respectively after printing 210 a specific number of printed layers.

[0091] Automatically determining the 220 area may include automatically obtaining the abrasion thickness of the squeegee lip by means of at least one sensor, and automatically calculating the 222 contact surface from the abrasion thickness and the original shape of the squeegee lip.

[0092] The method may include automatically adjusting the working angle to a preset angle range of 260 once the area exceeds the maximum area, and automatically resetting the working force to 265 after the adjustment of 260 for setting the desired pressing force. After the reset, printing of multiple printing layers may be performed again subsequently at 210.

[0093] The method may include automatically controlling at 240 at least one physical property of the layer printed on the substrate by means of the control device of the screen printing machine, and automatically adjusting at 250 the working force, working angle and / or working speed of the squeegee and / or the screen spacing between the screen and the substrate when the physical property is different from the relevant desired property.

[0094] The physical properties include, for example, the layer thickness of the layer along the Z-axis, the conductivity of the layer along the Z-axis and / or the specific resistance of the layer and / or the uniformity of the layer thickness and / or the conductivity along the XY plane spanned by the X-axis and the Y-axis.

[0095] After the adjustment of 250, printing of other printing layers may also be performed at 210.

[0096] List of reference numerals

[0097] 100 Screen printing machine

[0098] 110 Squeegee

[0099] 111 Squeegee lip

[0100] 112 Contact surface

[0101] 120 Screen

[0102] 121 Screen drive

[0103] 130 Squeegee drive

[0104] 140 Computer device

[0105] 150 Sensor

[0106] 160 Printing plate

[0107] 161 Printing plate drive

[0108] 170 Flood squeegee

[0109] 171 Flood squeegee drive

[0110] 180 Frame

[0111] 181 Frame driver

[0112] 190 Control device

[0113] 200 Method

[0114] 210 Printing

[0115] 220 Determine

[0116] 221 Obtain

[0117] 222 Calculate

[0118] 230 Reset

[0119] 240 Control

[0120] 250 Adjust

[0121] 260 Regulate

[0122] 265 Reset

[0123] d Abrasion thickness

[0124] s Spacing

[0125] X X-axis

[0126] Y Y-axis

[0127] Z Z-axis

[0128] α Working angle

[0129] β Measuring angle

Claims

1. A computer-implemented method (200) for controlling a screen printing machine (100), the screen printing machine having a) at least one screen (120), b) at least one squeegee (110) having a squeegee lip (111) fixed to the squeegee (110), wherein the squeegee lip (111) includes a contact surface (112) having an area for contacting the screen (120), c) at least one squeegee drive (130) for translating the squeegee (110) relative to the screen (120) along an X-axis (X) parallel to the screen (120) and along a Z-axis (Z) perpendicular to the screen (120), and for rotating the squeegee (110) relative to the screen (120) about a Y-axis (Y) perpendicular to the X-axis (X) and the Z-axis (Z), d) at least one computer device (140) for controlling the screen printing machine (100), and e) at least one sensor (150) communicatively connected to the computer device (140), the sensor for determining the area of the contact surface (112) of the squeegee lip (111), f) wherein the method includes printing a printing paste through the screen (120) by means of the squeegee lip (111) for producing a printed layer on a substrate from the printing paste, wherein the squeegee (110) is moved by the at least one squeegee drive (130), f1) in a working speed along the X-axis (X), f2) oriented at a working angle (α) relative to the Z-axis (Z), and f3) pressed onto the screen (120) with a working force along the Y-axis (Y), characterized in that the method has the following steps: g) automatically determining the area of the contact surface (112) of the squeegee lip (111) by means of at least one sensor (150) after printing a plurality of printed layers, h) after the determination, automatically resetting the working force according to the area for setting a preset desired pressing force of the squeegee lip (111) onto the screen (120), i) automatically adjusting the working angle (α) to a preset angle range once the area exceeds a maximum area, and j) after the adjustment, automatically resetting the working force for setting the desired pressing force.

2. The method according to claim 1, characterized in that a) automatically adjusting the working angle (α) in a first direction until the working angle (α) passes a first limit angle, b) automatically resetting the working angle (α) to an initial angle at the start of printing when passing the first limit angle, and c) automatically adjusting in a second direction opposite to the first direction after resetting the working angle (α) until the working angle (α) passes a second limit angle.

3. The method according to claim 1 or 2, characterized in that automatically determining the area includes: a) automatically obtaining an abrasion thickness (d) of the squeegee lip (111) by means of at least one sensor (150), and b) automatically calculate the contact surface from the abrasion thickness (d) and the original shape of the squeegee lip (111).

4. The method according to claim 3, wherein, automatically obtaining the abrasion thickness includes: a) automatically measuring the reference spacing of the squeegee lip (111) by the at least one sensor (150) when the reference abrasion thickness of the squeegee lip (111) is known, b) automatically measuring the spacing (s) of the squeegee lip (111) by the at least one sensor (150), and c) automatically calculating the abrasion thickness (d) from the reference abrasion thickness, the reference spacing and the spacing (s).

5. The method according to claim 4, wherein, a) perform the automatic measurement of the reference spacing while the squeegee (110) is oriented at a reference measurement angle relative to the Z-axis (Z), and b) perform the automatic measurement of the spacing (s) while the squeegee (110) is oriented at a measurement angle (β) relative to the Z-axis (Z), c) wherein the reference measurement angle corresponds to the measurement angle (β).

6. The method according to claim 4 or 5, wherein, a) perform the automatic measurement of the reference spacing while the squeegee (110) is oriented at a reference measurement angle relative to the Z-axis (Z), and b) perform the automatic measurement of the spacing (s) while the squeegee (110) is oriented at a measurement angle (β) relative to the Z-axis (Z), c) wherein the reference angle and / or the measurement angle (β) corresponds to the working angle (α).

7. The method according to claim 4, wherein, perform the measurement of the reference spacing and / or the spacing (s) while the at least one squeegee (110) rotates about the Y-axis (Y) by means of the at least one squeegee drive (130).

8. The method according to claim 1, wherein, the method has the following steps: a) automatically control at least one physical property of the layer printed on the substrate by the screen printing machine (100) by means of the control device (190) of the screen printing machine (100), and b) automatically adjust the working force, the working angle (α) and / or the working speed of the squeegee (110) and / or the screen spacing between the screen (120) and the substrate when the physical property is different from the relevant desired property, c) wherein the physical properties include the layer thickness of the layer along the Z-axis (Z), the conductivity of the layer along the Z-axis (Z) and / or the specific resistance of the layer and / or the uniformity of the layer thickness and / or the conductivity along the XY plane spanned by the X-axis (X) and the Y-axis (Y).

9. A computer-controlled screen printing machine (100) for operating the method according to any one of claims 1 to 8, the screen printing machine having a) at least one screen (120), b) at least one squeegee (110) having a squeegee lip (111) fixed thereto, wherein the squeegee lip (111) includes a contact surface (112) having an area for contacting the screen (120), c) at least one squeegee drive (130) for translating the squeegee (110) relative to the screen (120) along the X-axis (X) parallel to the screen (120) and along the Z-axis (Z) perpendicular to the screen (120) and for rotating the squeegee (110) relative to the screen (120) about the Y-axis (Y) perpendicular to the X-axis (X) and the Z-axis (Z), d) at least one computer device (140) for controlling the screen printing machine (100), characterized in that, e) at least one sensor (150) communicatively connected to the computer device (140), the sensor for determining the area of the contact surface (112) of the squeegee lip (111).

10. The screen printing machine (100) according to claim 9, characterized in that, the at least one sensor (150) includes a distance sensor for measuring the distance (s) between the contact surface (112) and the at least one sensor (150).

11. The screen printing machine (100) according to claim 10, characterized in that, the at least one sensor (150) is configured for distance measurement on at least two regions of the squeegee lip (111) spaced apart from each other along the Y-axis (Y).

12. The screen printing machine (100) according to any one of claims 9 to 11, characterized in that, a) a screen drive (121) communicatively connected to the computer device (140) for translating the screen (120) along the Z-axis (Z) relative to the substrate, b) a printing plate drive (161) communicatively connected to the computer device (140) for translating a printing plate (160) accommodating the substrate to be printed along the X-axis relative to the screen (120), c) at least one flood squeegee (170) for dispensing printing paste onto the screen (120) and a flood squeegee drive (171) communicatively connected to the computer device (140), the flood squeegee drive for translating the flood squeegee (170) relative to the screen (120) along the X-axis (X) and along the Z-axis (Z) and for rotating the flood squeegee (170) relative to the screen (120) about the Y-axis (Y), and / or d) at least one frame (180) carrying the at least one squeegee (110) and the at least one flood squeegee (170) and a frame drive (181) communicatively connected to the computer device (140), the frame drive for translating the frame (180) relative to the screen (120) along the Z-axis (Z).

13. The screen printing machine (100) according to claim 12, characterized in that, The at least one squeegee drive (130), screen drive (121), printing plate drive (161), flood squeegee drive (171) and / or frame drive (181) includes a plurality of electric motors communicatively connected to the computer device (140).

14. The screen printing machine (100) according to any one of claims 9 to 11, characterized in that the screen printing machine has at least one control device (190) communicatively connected to the computer device (140), the control device being configured to control at least one physical property of a layer printed onto the substrate with the screen printing machine (100), wherein the physical property includes the layer thickness of the layer along the Z-axis (Z), the conductivity of the layer along the Z-axis (Z) and / or the specific resistance of the layer and / or the uniformity of the layer thickness and / or the conductivity along the XY plane spanned by the X-axis (X) and the Y-axis (Y).

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