MULTISEGMENT PRINTING TABLE

Description

[0001] The present invention relates to a printing table designed for use in a screen printing device, and to a screen printing device with such a printing table, wherein the screen printing device is designed for three-dimensional screen printing.

[0002] Three-dimensional screen printing processes are used, for example, to produce three-dimensional components or molded parts. This process makes it particularly possible to create three-dimensional green bodies from metallic or ceramic powder. Here, material in paste form is successively applied layer by layer using a printing process until the component or green body reaches the desired height.

[0003] A key component of a screen printing machine is the screen tool, which comprises a screen frame and a screen element. The screen element typically consists of a composite of a screen mesh and a coating applied to the mesh, in which the layout of the component to be printed is incorporated. Each coated screen mesh is thus assigned a layout. The coating is impermeable to the printing paste. The layout specifies which areas of the screen mesh are left uncoated, allowing the printing paste to pass through. The screen element is firmly attached to the screen frame, in particular by being glued to the frame under tension.

[0004] In detail, to produce a component or green body, the paste, which is usually a suspension, is applied to the screen element and spread using a spreader. The paste is then forced through the screen element using a pressure blade. In this step, the paste is deposited onto a printing substrate on a printing table and forms a layer of material for the part to be produced. This layer is then typically processed further, primarily by curing. This is done, for example, by drying or UV irradiation.

[0005] These steps are repeated until the desired height of the product is reached. To achieve different contours in the printed product, the screen element, in particular the coated screen fabric with a layout, may need to be changed periodically.

[0006] The resulting three-dimensional printed product can then be used as desired or, if necessary, further processed mechanically or in another form.

[0007] If the three-dimensional printed product produced in this way is a green body, it can then be subjected to heat treatment, in particular sintering.

[0008] This process is particularly suitable for the production of components or molded parts where the shape or cross-section does not change along a longitudinal axis, since the component or molded part can then be printed layer by layer along the longitudinal axis without the need to change the screen element.

[0009] If the shape of a component or mold changes along its longitudinal axis, for example due to undercuts or bulges, or because the component becomes wider or narrower, the screen tool, or at least the coated and patterned screen mesh, must be changed accordingly. This leads to undesirable delays in the manufacturing process and usually requires manual work.

[0010] To produce the largest possible number of components in the shortest possible time, the method used is to simultaneously create, and in particular print, several components or molds on a single printing table. The components or molds are produced side by side on the printing table, with the layout of the coated screen fabric designed to allow for the simultaneous production of multiple components or molds. For example, the coated screen fabric may contain several identical masks to enable the production of multiple components or molds side by side on a stationary printing table.

[0011] This process reaches its limits when manufacturing molded parts that are twisted along their longitudinal axis, such as screw-like or helical parts, because the layout, and therefore the coated screen fabric, must be changed regularly, in extreme cases even after every printing step. While the contour and / or size of the molded part in cross-section does not change, or at least not very frequently, its orientation does. For mass production of molded parts twisted along their longitudinal axis, this process is therefore too expensive.

[0012] To produce these molded parts on a stationary printing table, it may be necessary, as described above, to change the screen tool or at least the screen mesh with a layout after each printing step. Alternatively, as described in DE 10 2019 123 128 A1 or WO 2011 / 112692 A1, either the entire printing table or the entire screen frame can be rotated, so that the screen element, in particular the screen mesh with a layout, only needs to be changed if the contour and / or size of the molded part changes from one printing layer to the next.

[0013] However, this leads to either the production of a component or molded part positioned centrally on the printing table, which is inefficient for mass production, or the need for very complex coordination between the layout of the coated screen mesh and the position of the molded part on the printing table. For example, screen tools with different layouts can be used, which are rotated and / or shifted relative to the printing table, and the printing table itself can also be rotated and / or shifted. The more complex the coordination between the layout of the coated screen mesh and the position of the molded part on the printing table, the greater the risk of inconsistencies that can affect the quality of the molded part.Systems that produce multiple molded parts simultaneously must operate with very high precision to manufacture a large number of parts with minimal deviations. With these processes, a comparatively high reject rate is to be expected.

[0014] The production of a large number of structural or molded parts with a twist along the longitudinal axis is therefore very complex.

[0015] The object of the present invention is to provide a device with which it is possible to quickly and inexpensively produce a large number of components or, more generally, a large number of shaped bodies that are rotated along a longitudinal axis using a three-dimensional screen printing process.

[0016] In particular, the object of the present invention is to provide a device with which it is possible to quickly and inexpensively produce a large number of components or, more generally, a large number of shaped bodies that are rotated along their central axis, such as screw-like, propeller-like or helical shaped bodies, in a high quality using a three-dimensional screen printing process.

[0017] Furthermore, it is an object of the present invention to provide a device for the production of molded bodies which makes it possible to produce molded bodies that are rotated along their longitudinal axis as automatically as possible.

[0018] According to the invention, the problem is solved by a printing table according to claim 1, namely a printing table designed for use in a screen printing device designed for three-dimensional screen printing, wherein the printing table has a plurality of printing positions at which a molded body can be produced, wherein the printing table has at least two segments and an adjustment device, wherein each segment contains a printing position and is rotatable relative to the printing table, and wherein the adjustment device is designed to rotate the at least two segments relative to the printing table.

[0019] The term "printing position" here refers to the point where the molded body is successively formed on the printing table.

[0020] Replacing the screen element, which features a screen mesh printed with a layout, is only necessary when manufacturing a molded part using this printing table if the contour and / or size of the molded part's cross-section changes from one printed layer of material to the next. Replacing the layout, and therefore the coated screen mesh, due to a simple change in the orientation of a cross-sectional shape from one printing step to the next is not required.

[0021] With this printing table, it is therefore easy to produce multiple molded parts where the contour and size of the cross-section rarely change from one printed layer to the next, compared to the orientation of the cross-section. Since the number of screen element changes is significantly reduced compared to other screen printing processes, production speed can be increased. When producing these types of molded parts, the printing table and the screen tool / element are held stationary; only the segments themselves are rotated, making the alignment of the printing table and screen element relatively simple. Quality variations of the molded parts due to inaccurate positioning during the printing process therefore occur much less frequently than with previously known screen printing systems.

[0022] Preferably, a segment has an axis of rotation oriented perpendicular to the surface of the printing table. This printing table is therefore particularly suitable for the production of molded parts or components that are helically or helically twisted along their central axis. This printing table is especially ideal for twisted molded parts where the cross-sectional shape of the part does not change along its longitudinal axis. In this case, it is not necessary to replace the coated screen mesh with its layout during the entire manufacturing process of the molded part, thus eliminating delays or process downtime due to screen element changes. Because screen element changes are no longer necessary, the production of this type of molded part can even be fully automated.

[0023] In a preferred embodiment, the adjusting device is designed to rotate at least two segments simultaneously. This allows the production speed to be increased.

[0024] It is further advantageous that the adjustment device is designed to rotate at least two segments at the same angle. For example, if the layout of the coated screen fabric is a regular pattern, allowing a large number of identical patterns to be produced in a single printing step, the fact that the segments are always rotated at the same angle means that the molded parts exhibit only very slight deviations, if any, from one another. Thus, a large number of nearly identical molded parts can potentially be produced fully automatically.

[0025] To actuate the adjusting device, the adjusting device can include a motor, in particular a stepper motor. Alternatively, the adjusting device can include at least one of the following actuators: pneumatic actuator, hydraulic actuator, piezoelectric actuator.

[0026] The adjustment device is designed to drive each segment individually. This allows for a very high degree of flexibility in adjusting the individual segments. However, the control system is quite complex and prone to errors when a large number of identical molded parts are to be produced simultaneously.

[0027] To easily drive the segments synchronously, it is therefore advantageous to have an adjusting device that includes a gearbox designed to rotate at least two segments simultaneously. For example, the gearbox could be a gear system or a belt drive.

[0028] In a preferred embodiment, at least one segment comprises a circular disk or a circular plate, wherein the disk or plate is preferably arranged flush with the printing table.

[0029] Since the segment can rotate relative to the printing table, it is particularly advantageous, if the segment is wholly or partially embedded in the printing table, for the segment to be arranged with play in a recess of the printing table.

[0030] To ensure that the molded part is securely held on the segment during the manufacturing process, it is advantageous for at least one segment to include means for fixing the molded part. Suitable fixing means include, for example, mechanical devices such as clamps or screws. With a suitable substrate or paste that is itself magnetic, magnetic fixing elements can also be provided on the printing table. Alternatively, the molded part can be held on the segment during the manufacturing process by means of adhesion or vacuum.

[0031] To produce as many turned molded parts as possible, it is preferred that a plurality of segments be provided, each containing a printing position and rotatable relative to the printing table, wherein the adjustment device is designed to rotate the plurality of segments relative to the printing table. The adjustment device can be designed to rotate the segments at the same or at different angles.

[0032] The present invention also relates to a screen printing device designed for three-dimensional screen printing, wherein the screen printing system comprises a printing table with the specified features and a screen tool which is arranged above the printing table.

[0033] Preferably, the sieve tool comprises a sieve frame and a sieve element, the sieve element typically consisting of a composite of a sieve fabric and a coating in which a layout for the component to be printed is incorporated. This results in a coated sieve fabric in which some areas are permeable to the printing paste and other areas are impermeable to the printing paste. The sieve element, in particular the coated sieve fabric with the layout, is tensioned and firmly connected to the sieve frame. For example, the sieve element is bonded to the sieve frame.

[0034] In a preferred embodiment of the screen printing device, the at least two segments each comprise an axis of rotation perpendicular to the printing table, and a plurality of masks are provided in the screen tool, in particular in the coated screen fabric, with each segment being assigned a mask. The plurality of masks preferably form the layout of the screen element.

[0035] Since producing a turned molded body with a cross-section whose contour and size remain constant along the longitudinal axis requires only a rotational movement of the segment relative to the stationary printing table and the stationary screen tool, comparatively fewer work steps are needed to successively apply the individual material layers to manufacture the molded body. With this screen printing device, a large number of turned molded bodies can therefore be produced in a short time.

[0036] To obtain a molded body that is rotated along its central axis and whose contour and size remain constant along the longitudinal axis, it is advantageous for the mask to have a center point located on the segment's axis of rotation. This allows the manufacturing process of the molded parts to proceed automatically and without interruption due to a change of the screen element, without requiring any adjustments or realignments of the molded part's printing position.

[0037] In a first embodiment of the screen printing device, the printing table is designed as a separate component, which rests as an attachment on a fixedly mounted printing table of the screen printing device.

[0038] Alternatively, the printing table is permanently mounted in the screen printing device as the actual printing table. The present invention also includes a method for producing a three-dimensional molded body according to claim 15.

[0039] Advantageous embodiments are explained in more detail with reference to the accompanying drawings, which show: Fig. 1 the basic structure of a screen printing system; Fig. 2 a printing table in a top view; Fig. 3 a first embodiment of a printing table in a bottom view; Fig. 4 a first embodiment of an adjustment device; Fig. 5 a second embodiment of an adjustment device; Fig. 6 a third embodiment of an adjustment device; Fig. 7 a fourth embodiment of an adjustment device; Fig. 8 a component manufactured with a printing table according to Fig. 2 ; Fig. 9 another component manufactured with a pressure table according to Fig. 2 .

[0040] Fig. 1Figure 1 shows the construction of a screen printing system 10, suitable for three-dimensional screen printing, according to a first embodiment. The screen printing system 10 comprises a printing table 12 and a screen tool 14, the screen tool 14 in turn comprising a screen frame 16 and a screen element 18, consisting of a screen mesh 17 and a coating 19 applied to the screen mesh. The layout of the component to be printed is incorporated into the coating, such that individual areas of the screen mesh 17 are permeable and other areas of the screen mesh 17 are opaque. The layout can have a plurality of identical or different masks. The screen mesh 17, provided with a coating 19 and a layout, is rigidly connected to the screen frame 16, and the screen mesh 17 is taut.

[0041] The sieve element 18 is located above the printing table 12 and is aligned parallel to the surface of the printing table 12. Above the sieve element 18, a device (not shown) for feeding paste-like substrate 20 onto the sieve element 18 is provided, as well as a flood squeegee 22 and a pressure squeegee 24.

[0042] The paste-like substrate 20 can, for example, be a suspension consisting of a binder with a metallic or ceramic powder. In this case, green bodies are produced using the screen printing process, which usually then need to be sintered.

[0043] Although not shown, a height adjustment device is provided which adjusts the distance A of the printing table 12 relative to the sieve element 18 or the rebound, i.e. the distance between the underside of the sieve element 18 and the green body.

[0044] The printing table 12 includes, as particularly in Fig. 2 A multitude of circular segments 26 can be identified, which are rotatably mounted in the printing table 12. Each segment 26 is designed as a flat disk and can be rotated clockwise and counterclockwise about a rotation axis located at the center of the segment 26. Furthermore, a printing position is provided on each segment 26, so that a molded body can be produced on each segment 26.

[0045] To secure the molded part to be produced on segment 26, means are provided for fixing the molded part during the manufacturing process. In this specific case, the molded parts are held on segment 26 by means of a vacuum. For this purpose, openings 27 parallel to the axis of rotation are incorporated into the disk, which are connected to a suction device (not shown) located below the pressure table.

[0046] Recesses 28 are provided in the printing table 12 for the segments 26, in which the disc-shaped segments 26 are inserted with a precise fit but with minimal play. The upper surface of the segments 26 is flush with the upper surface of the printing table 12, so that the printing table 12 has a substantially flat surface.

[0047] In Fig. 3 is the in Fig 1 The illustrated pressure table 12 is shown from below. The adjustment device, designed to adjust the segments 26, can be seen here. In this embodiment, a motor 32 is provided below each segment 26. The motor 32 is, for example, a stepper motor. Each of the in Fig. 3The nine segments 26 shown are each driven by a motor 32, wherein the individual segments 26 can be centrally controlled by means of a control device not shown and can thus be rotated either synchronously and at the same angle or independently of each other.

[0048] Fig. 4Figure 1 shows another embodiment of an adjustment device for the nine segments 126. The adjustment device comprises a motor 132, which drives each segment 126 by means of a gear transmission. For this purpose, each segment 126 is provided with a gear 140 on its underside, the gear 140 being arranged concentrically to the respective segment 126. The individual gears 140 provided on the underside of the segments 126 are in turn connected to each other by connecting gears 142, which engage with the gears 140 provided on the underside of the segments 126. The connecting gears 142 have a smaller diameter than the gears 140 on the segments 126. The position of the connecting gears 144 is chosen such that all gears 140, 144 form a gear chain. Thus, when one segment 126 is rotated, all segments 126 are rotated. A motor 132, in particular a stepper motor, is provided to drive this gear chain.In this case, the stepper motor is mounted below the central segment 126. The size of the gears 140, which are provided on the underside of the segments 126, and the connecting gears 142 are selected and matched so that the segments 126 are rotated synchronously and at the same angle by means of the motor 132.

[0049] During a Fig. 5 The illustrated embodiment of an adjusting device with a motor 232 and a gearbox uses, instead of the one shown in Fig. 4The gears 140, 142 and belts 250, 252 shown are provided, which are guided via pulleys 254. Here, too, a central segment 226 is driven in the middle by a motor 232, with a main belt 250 connecting the segment 226, on which the motor 232 is located, to another segment 226. This segment 226, which is connected to the main belt 250, then connects the remaining segments 226 by means of a circulating belt 252. Furthermore, pulleys 254 are provided both on the segments 226 and on the printing table between the segments 226. The position of the pulleys 254 on the printing table between the segments 226 is chosen such that the individual segments 226 are adjusted synchronously, i.e., simultaneously and at the same angle.

[0050] The Figure 6 and 7 show variations of a belt arrangement on a printing table with nine segments.

[0051] At the in Fig. 6In the illustrated embodiment, the central segment 326 is driven by a motor 332. The segment 326, on which the motor 332 is mounted, is connected to another segment 326 via a main belt 350. Each segment 326 has a pulley 354 and is connected to two adjacent segments 326 by means of two connecting belts 356. The connection of adjacent segments 326 is such that a belt chain is formed, which connects all segments 326 together. The motor 332 can drive all segments 326 by means of this belt chain. In this arrangement, the individual segments 326 are adjusted synchronously, i.e., simultaneously and at the same angle.

[0052] As with the in Fig. 7 In the illustrated embodiment, the central segment 426 has a motor 432. Each segment has a pulley 454. The in Fig. 7 The embodiment shown differs from the one in Fig. 6In the illustrated embodiment of an adjusting device, each segment 426 is connected in a star-shaped configuration to the central segment 426, to which the motor 432 is attached, by means of a main belt 450. In this embodiment, the motor 432 can adjust all segments 426 synchronously, i.e., simultaneously and at the same angle.

[0053] In Fig. 8 A component is shown which can be manufactured using the screen printing system at hand.

[0054] The printing table 12 can be integrated into a screen printing system 10 or placed as an attachment on an existing permanently mounted printing table of a screen printing system.

[0055] To produce a large number of shaped bodies rotated along a longitudinal axis using the printing table 12, a screen element 18, comprising a coated screen fabric 19 with a large number of masks, is prepared. The number of masks corresponds to the number of segments 26, 126, 226, 326, and 426. The screen element 18 with the screen fabric 17 and the masks is positioned above the segments 26, 126, 226, 326, and 426 such that a mask is arranged above each segment 26, 126, 226, 326, and 426.

[0056] In a first step, a first layer of material is applied to segment 26; 126; 226; 326; 426 in a known manner and, if necessary, further processed, such as dried or hardened. The distance between the pressure table 12 and the screen element 18 is then changed while maintaining a constant gap. Before, simultaneously, or after this, segments 26; 126; 226; 326; 426 are synchronously adjusted using one of the described adjustment devices. The next layer of material is then applied to segment 26; 126; 226; 326; 426 in a known manner and, if necessary, further processed. The distance between the pressure table 12 and the screen element 18 is then changed again while maintaining a constant gap. Before, simultaneously, after, or after a certain number of printing layers, segments 26; 126; 226; 326; 426 was adjusted synchronously again using one of the described adjustment devices.This process is repeated until the large number of molded parts is complete.

[0057] In the Figs. 8 and 9 The figures show molded parts that can be produced in a screen printing system using the described printing table 12. These are molded parts that are rotated along a central axis.

[0058] If the contour or size of the cross-section of the molded body does not change along its central axis, no change of the sieve elements 18 is required. A change of the sieve elements 18 would only be necessary if the cross-section changes with respect to contour or size along the longitudinal axis of the molded body.

[0059] The shaped body has a flat base. To obtain a shaped body with a longitudinal axis perpendicular to its base, care must be taken to ensure that the longitudinal axis running through the center of the shaped body forms an extension of the segment's axis of rotation.

[0060] Although not shown, the individual segments 26; 126; 226; 326; 426 can also be designed as circular plates. Furthermore, the segments 26; 126; 226; 326; 426 can protrude from the printing table or be recessed into it.

[0061] To actuate the adjustment device, which can be done manually or programmatically, the adjustment device can include a motor, in particular a stepper motor, as shown. Alternatively, the adjustment device can include another actuator, such as a pneumatic actuator, hydraulic actuator, or piezoelectric actuator.

[0062] It is understood that a printing table can have any number of segments and is not limited to the nine segments shown. The one in the Figures 4 to 7 The depicted motor is not necessarily attached to the middle or central segment. The motor can also be attached to other segments.

[0063] To ensure that the molded part is securely held on the segment during the manufacturing process, the illustrated embodiments provide for the creation of a vacuum on the segment's disk. In embodiments not shown, other means for fixing the molded parts to be produced may be provided. Suitable fixing means include, for example, mechanical means such as clamps or screws. With a suitable substrate or paste that is itself magnetic, magnetic means may also be used. Alternatively, the molded part can be held in place by adhesion during the manufacturing process.

[0064] It is understood that the features of the illustrated embodiments can be combined with each other, and that individual features of the illustrated embodiments can also be omitted.

Claims

1. A printing table (12) designed for use in a screen printing apparatus configured for three-dimensional screen printing, wherein the printing table (12) comprises a plurality of printing positions at which a moulded body can be produced, characterised in that the printing table (12) comprises at least two segments (26; 126; 226; 326; 426) and an adjustment device, wherein each segment (26; 126; 226; 326; 426) comprises a printing position and is rotatable relative to the printing table (12), and wherein the adjustment device is designed to rotate the at least two segments (26; 126; 226; 326; 426) relative to the printing table (12).

2. The printing table according to claim 1, characterised in that at least one segment (26; 126; 226; 326; 426) has an axis of rotation which is aligned perpendicular to the surface of the printing table (12).

3. The printing table according to any one of the preceding claims, characterised in that the adjustment device is designed to rotate the at least two segments (26; 126; 226; 326; 426) simultaneously and / or by the same angle.

4. The printing table according to any one of the preceding claims, characterised in that the adjustment device comprises a motor (31; 132; 232; 332; 432), in particular a stepper motor.

5. The printing table according to any one of claims 1 to 3, characterised in that the adjustment device comprises at least one of the following actuators: a pneumatic actuator, a hydraulic actuator, a piezoelectric actuator.

6. The printing table according to any one of the preceding claims, characterised in that the adjustment device comprises a transmission designed to rotate the at least two segments (26; 126; 226; 326; 426) simultaneously.

7. The printing table according to claim 6, characterised in that the transmission is a gear drive or a belt drive.

8. The printing table according to any one of the preceding claims, characterised in that at least one segment (26; 126; 226; 326; 426) comprises a circular disc or a circular plate, which is preferably arranged flush with the surface of the printing table (12).

9. The printing table according to any one of the preceding claims, characterised in that at least one segment (26; 126; 226; 326; 426) comprises means for securing the moulded body.

10. The printing table according to any one of the preceding claims, characterised in that a plurality of segments (26; 126; 226; 326; 426) is provided, each of which contains a printing position and is rotatable relative to the printing table (12), and in that the adjustment device is designed to rotate the plurality of segments (26; 126; 226; 326; 426) relative to the printing table (12).

11. A screen-printing apparatus designed for three-dimensional screen printing, comprising a printing table (12) according to any one of the preceding claims and a screen-printing tool (14) arranged above the printing table (12).

12. The screen-printing apparatus according to claim 11, characterised in that the at least two segments (26; 126; 226; 326; 426) each have an axis of rotation perpendicular to the printing table (12) and in that a plurality of masks are provided in the screen-printing tool (14), with one mask being assigned to each segment (26; 126; 226; 326; 426).

13. The screen-printing apparatus according to claim 12, characterised in that at least one mask is symmetrical and has a centre point, wherein the centre point of the mask lies on the axis of rotation of the associated segment (26; 126; 226; 326; 426).

14. The screen-printing apparatus according to any one of claims 11 to 13, characterised in that the printing table (12) is designed as a separate component which rests as an attachment on a fixedly mounted printing table of the screen-printing apparatus.

15. A method for producing a three-dimensional moulded body using a screen printing apparatus according to any one of claims 11 to 14, wherein the moulded body is produced in a plurality of printing steps, characterised in that, after a printing step, the at least two segments (26; 126; 226; 326; 426) are rotated simultaneously or at the same angle, or in that, after a printing step, the at least two segments (26; 126; 226; 326; 426) are rotated simultaneously and at the same angle.