Printhead for a 3D printer and method for operating a printhead

Abstract

Print head for a material-depositing 3D printer with at least one first and at least two second (usually all equipped for simultaneous material deposition) material deposition nozzles, which are held (directly or indirectly) on at least one nozzle carrier that is movable in the main working direction, wherein at least the at least one first material deposition nozzle is mounted and driven in such a way that, while it is in the process of material deposition, it can be moved back and forth transversely (and usually perpendicularly) to the main working direction, preferably pendulum-like.

Description

[0001] The invention relates to a print head for a 3D printer, consisting of more than two material application nozzles, and a method for operating a print head with more than two material application nozzles. TECHNICAL BACKGROUND

[0002] Printheads with two material application nozzles are known. These are used to extrude different materials or to build support structures, which are then removed, for example, after the printing process is complete. The term "material application nozzle" will also be abbreviated as "nozzle" in the following text.

[0003] It is already known to create "sandwich-like" or corrugated cardboard-like structures using 3D printers. These are characterized by the fact that two materials extruded opposite each other on a single extrusion plane are joined by an intermediate extruded layer of material. After numerous repeated extrusion cycles, the first materials then form, as is known from corrugated cardboard, outer layers or, in terms of bending mechanics, "ribs" on both sides, which are connected, or are intended to be connected, by a corrugated central rib. PROBLEM

[0004] The "sandwich- or corrugated board-like" structures are created by extruding a single sheet; that is, the first outer sheet, the corrugated middle rib, and the second outer sheet are produced at different times. The bond between the individual sheets depends heavily on, among other things, the material quality at the time of bonding (temperature, viscosity, adhesion, bond strength) and any other relevant parameters.

[0005] Furthermore, a sequential production process for "sandwich- or corrugated board-like" structures can only result in the layers being laid parallel to each other. This means that the corrugated core or corrugated sheet is only attached to the outer layers from the inside and is therefore only more or less strongly "bonded" to them. Even minor material or process-related shrinkage often leads to the separation of the bond between the corrugated sheet, which forms the stabilizing core, and the outer layers. Dynamic loads can be even more likely to cause this undesirable separation. TASK

[0006] The purpose of the invention is to produce more reliable “sandwich- or corrugated board-like” structures. SOLUTION

[0007] The solution to the aforementioned problem is primarily achieved by a printhead according to the main claim.

[0008] A print head for a material-depositing 3D printer is proposed. The print head has at least one first and at least two second material deposition nozzles. Typically, all material deposition nozzles are capable of simultaneous material deposition. The material deposition nozzles are held directly or indirectly on at least one nozzle carrier. The at least one nozzle carrier is movable in the main working direction. According to the invention, at least the at least one first material deposition nozzle is mounted and driven such that, while in the process of material deposition, it can be moved transversely and preferably in a straight line perpendicular to the main working direction, preferably by oscillation. In this way, it can create a structure that extends more than negligibly transversely to the main working direction.

[0009] The second material application nozzles serve to simultaneously produce two spaced-apart top layers. The first, at least one, material application nozzle is used to produce the corrugated and / or zigzag layer that connects the two top layers. The connection is particularly stable and reliable because the two top layers and the corrugated or zigzag layer grow essentially simultaneously with each newly laid material bead. This means that when the newly laid material beads on the top layers meet the newly laid bead on the corrugated or zigzag layer, the beads can be laid seamlessly into one another where their paths intersect. They are also still hot and without a setting skin, and therefore highly ready to fuse.In this way, a close bond can be achieved between the cover sheets of the structure to be printed and its corrugated or zigzag web, which shows a significantly increased strength and reliability.

[0010] Optionally, more than one first material application nozzle can be provided. For example, if two first material application nozzles moving in opposite directions perpendicular to the main feed direction are used during printing, two intersecting corrugated or zigzag lines can be created between the two cover lines, ensuring a particularly strong bond because they form a kind of cross-bracing.

[0011] Optionally, more than two secondary material application nozzles can be provided, for example, four or more, to print uniform, particularly robust cover webs or even to produce two parallel cover webs on each side, thus reinforcing, for example, an area that will later be subjected to particularly high pressure. In the latter case, the corrugated or zigzag web will be designed so that it extends between the two outermost cover webs and passes over the inner cover webs, thereby bonding them to the corrugated or zigzag web.

[0012] Ideally, at least one first material application nozzle can be moved at variable speed perpendicular to the main working direction, as this allows for the printing of a particularly favorable, because rounded or ideally even sinusoidal wave. DEFINITIONS OF TERMS

[0013] A cover layer is understood to be, in particular, a flat sheet of material created by repeatedly printing beads of material onto it, forming the outer surface of the structure to be printed. If we consider corrugated cardboard in this context, then its cover layers are the two paper layers between which the corrugated core extends.

[0014] A corrugated sheet is defined as the supporting structure that extends in a wave-like, and preferably sinusoidal, pattern between two cover sheets, and in exceptional cases, between more cover sheets. The same applies analogously to the term zigzag sheet.

[0015] For the sake of clarity, it should be noted that the term "material application nozzle" or "nozzle" is currently understood here in a broad sense, although a narrower, fluid-engineering definition is an option to which the definition can be restricted later if necessary. The term "printing material" refers to very different materials. It can be a molten plastic compound applied to the substrate, or plastic or metal granules that are placed on the substrate and then melted in situ, thus bonding to it. It can also be a cement-like compound, which does not necessarily have to be water-based, but ideally incorporates a plastic binder or a plastic coating.

[0016] The term "material bead" refers to the layer that is printed, or applied, in one step.

[0017] Minimal cooling or setting is preferably assumed when a first and a subsequently applied bead of material meet, and the first bead still exhibits at least 90% of its initial bonding strength. The term "bead of material" is not limited to a specific manufacturing process (such as welding) or to a particular geometry of the applied material, such as a sausage-shaped cross-section.

[0018] The terms "corrugated sheet" and "zigzag sheet" are used repeatedly below. In their narrower sense, these terms primarily refer to sheets that are truly corrugated or accordion-like in a zigzag pattern; however, for the time being, they are also used in a broader sense and stand for any type of supporting structure between two defective cover sheets. PREFERRED FURTHER EDUCATION OPPORTUNITIES

[0019] The printhead can preferably be designed such that at least one, preferably at least two, of the second material application nozzles are held in such a way that they can also be adjusted transversely to the main working direction.

[0020] In this way, the printhead can be easily adjusted to print walls of varying thicknesses. It is not absolutely necessary to adjust the thickness during the actual printing process. In many cases, it is sufficient for the operator to adjust a second material application nozzle accordingly before printing a wall of uniform thickness.

[0021] If only one additional material application nozzle or only several additional material application nozzles located on one side can be adjusted transversely to the main working direction, then at least one first material application nozzle must be adjustable so that it then oscillates around a corresponding other central position that matches the current position of the additional material application nozzles.

[0022] Therefore, it is particularly advantageous if at least two or more additional material application nozzles can be adjusted in opposite directions, so that they can be set to a thicker wall without having to make changes to the first material application nozzle.

[0023] Ideally, the aforementioned secondary material application nozzles are mounted and driven in such a way that they can be moved perpendicular to the main working direction while material is being applied. This makes it possible to automatically adjust different wall thicknesses during printing, for example, to print a thinner partition and a thicker support wall in a single operation.

[0024] It is particularly advantageous if at least one first material application nozzle is positioned upstream of at least two second material application nozzles in the main working direction.

[0025] This allows for a greater amplitude than would be permitted by the spacing of the subsequent nozzles, i.e., if the first nozzle were positioned between the two subsequent nozzles. As a result, the beads for the surface layers and the corrugated, zigzag, or other support layers are not laid parallel. Instead, the beads for the corrugated, zigzag, or other support layers are laid by the first nozzle at the meeting points onto the underlying, previously generated beads of the subsequent nozzles and clamped from above by the trailing beads of the subsequent nozzles.

[0026] Ideally, the at least one first and at least two subsequent material application nozzles are arranged, designed, and moved in such a way that the currently laid material bead from the at least one first material application nozzle is placed at specific intervals onto the material beads laid in the previous work step by the at least two subsequent material application nozzles and then clamped from above by the currently laid paths from the at least two subsequent material application nozzles. In this way, a particularly close bond can ultimately be achieved between the central corrugated sheet or the central zigzag sheet and the respective lateral cover sheet.

[0027] Ideally, the inventive 3D print head is designed such that the at least one first and at least two further material deposition nozzles are arranged so close together that the layer currently laid down by the at least one material deposition nozzle can connect with the layers currently laid down by the at least two second material deposition nozzles without having cooled or set (more than negligibly) before the layers from the at least two further nozzles arrive. The definition of setting or cooling mentioned at the beginning applies here. In this way, a particularly strong bond is ensured at the interface between a top layer and the associated corrugated or zigzag layer.This is precisely what distinguishes the invention from known single-jet printers, which print the respective cover layer and the associated corrugated layer with too great a time interval, which is why an optimal bond cannot be achieved because the bonding capacity of the materials has already deteriorated too much.

[0028] It is particularly advantageous if the printhead has means by which the application quantity and / or application speed can be controlled (completely printhead-autonomously or with the additional help of an external control, such as that of the robot or other control) at least for some of the material application nozzles.

[0029] Ideally, printing is done in such a way that the points where the corrugated or zigzag web meets the cover web are calculated in advance. In this area, the bead of the corrugated or zigzag web, which is usually applied ahead of time, can then be made slightly smaller locally. The same is subsequently done with the bead of the cover web when it reaches the relevant point. At the relevant point, for example, the bead of the cover web and the bead of the corrugated web, each reduced by 50%, result in precisely the material thickness required to prevent an undesirable accumulation of material where the corrugated and cover webs meet. The same principle applies, of course, if a zigzag web is used instead of a corrugated web.

[0030] In many cases, it is also useful if a bead of material can only be applied temporarily via one of the at least two additional material application nozzles. This is the case, for example, when a wall structure has an end face where the wall terminates, perhaps because a door will later be installed there.

[0031] Ideally, the printhead has means by which the at least one first material application nozzle can be moved independently of the other material application nozzles (either completely autonomously or with the additional aid of an external controller), preferably in such a way that it lays down wave-like paths during the printhead's movement in the main working direction, ideally paths whose amplitude and / or frequency changes. This latter method makes it possible to work particularly efficiently with material. Where the load on the structure to be printed is relatively low, a wave-like path is drawn between the two cover layers, which changes at a lower frequency than at another point where the load on the structure to be printed is higher.

[0032] Ideally, protection is required not only for the printhead itself, but also for the entire printer equipped with it. This is because the printhead may lack certain necessary components, for example, because the printer does not provide the control electronics required to properly control and drive the printhead's valves and motors.

[0033] Ideally, protection is also sought for a method for operating a printhead according to one of the corresponding claims or for operating a 3D printer equipped with such a printhead according to one of the corresponding claims, which is characterized in that material is applied simultaneously with at least three material application nozzles, wherein at least one first material application nozzle oscillates back and forth transversely to the main working direction between the extreme positions that define at least two further, preferably trailing, material application nozzles which move at least predominantly only in the main working direction.

[0034] The claimed method may have one or more further process-related features that result directly or indirectly from the preceding description of the printhead. LIST OF FIGURES The Fig. Figure 1 shows a printhead according to the invention printing a wall structure, here for a building. The Fig. Figure 2 shows the entire 3D printer. The Fig. Figure 3 shows a view of the printhead. PREFERRED EXAMPLE OF EXECUTION

[0035] Clearly visible in the Fig. 1 is the printhead 1, which is suspended here from a robot arm coming from above. As can be seen, the printhead 1 is connected to the robot arm via a swivel joint 6 with a vertical swivel axis in order to be able to change the main working direction of the printhead so that printing can also be done over the corner 3 of the workpiece 2, as shown here.

[0036] In this embodiment, the workpiece to be printed is a wall structure for a building. This wall structure consists of two spaced-apart cover sheets 4. These two cover sheets 4 are connected to each other via a corrugated sheet 5. As can be clearly seen, the frequency of the corrugated sheet varies locally. In this way, where the corrugated sheet corrugates at a higher frequency, it forms locally stiffer structures 5a, for example, similar to a vertical beam.

[0037] Typically, the printhead is not only connected to the robot arm via a swivel joint 6 with a vertical pivot axis, but also simultaneously via another swivel joint 7 with a horizontal pivot axis. In this way, for example, roof slopes can be printed when constructing wall elements.

[0038] Also in Fig. 1 The material supply hoses 8 are clearly visible. They are used, for example, to supply acrylic-based cement or other printing materials from an external tank or mixer drum.

[0039] The Fig. Figure 2 shows the 3D printer as a whole. The two gantry rails 9 and the cross rail 10, on which the robot arm 11 is suspended and which it can move along, are clearly visible. The robot arm is, of course, height-adjustable to accommodate the printing progress.

[0040] The Fig.Figure 3 shows a closer view of the printhead. The swivel joint 6 with its vertical pivot axis and the swivel joint 7 with its horizontal pivot axis are clearly visible. The main working direction is symbolized by arrow 12. The nozzle carrier 13 is also clearly visible. The first material application nozzle 14 and one of the two second material application nozzles 15 are visually prominent. Only a small part of the third material application nozzle is visible. However, the threaded spindle 16 is visible. The first material application nozzle 14, which leads the main working direction, is attached to this spindle in such a way that it can be moved back and forth, preferably at a variable speed, at least transversely and, as a rule, exactly perpendicular to the main working direction. A spindle drive has proven very effective here because it always enforces a precisely defined position.

[0041] The two second material application nozzles 15 are also adjustable transversely and, as a rule, perpendicular to the main working direction. In this way, the thickness 17 of the wall can be varied. Although not shown in the drawing, it is usually the case that the two second material application nozzles 15 can also be moved not only manually, but continuously. This allows for the creation of continuously transitioning wall thicknesses, which is important, for example, where a thin partition wall of a wall module transitions into a thicker supporting wall via a corner or a T-joint.

[0042] A mechanical bond is created between the connecting and supporting structures. Material- or process-related shrinkage can be better compensated for.

[0043] By controlling the feeding of different amounts of material to the individual material application nozzles, variable thicknesses can be produced for the cover webs and / or the corrugated webs or the zigzag webs.

[0044] Variable numbers of connection and support structures can be created between the outer surfaces. This allows, for example, the mechanical stiffness of the component to be increased in certain areas. Material can also be saved across the surface.

[0045] It is also possible to create purely local material thickenings, for example in the form of special fixing points that offer enough material to allow a corresponding screw to be inserted after drilling, for example to fix a sink, toilet bowl or bidet.

[0046] There are numerous practical applications for the inventive method or printer: Large-volume 3D printer in the construction industry for processing concrete. Large-volume 3D printer in the construction industry for the production of sandwich walls in the area of ​​prefabricated or modular houses. Large-volume 3D printer in the plastics processing industry, e.g. boat building, swimming pool construction, vehicle construction. MISCELLANEOUS

[0047] Protection for a printhead with multiple material application nozzles is also required at the appropriate time. Optionally, this printhead can be equipped with one or more features disclosed above or below in the exemplary embodiment, even if these features may only be presented in conjunction with other features. REFERENCE MARK LIST 1 printhead 2. Workpiece to be printed 3 Corner of the workpiece to be printed 4. Decking 5 corrugated sheet 5a locally stiffer structure 6 Swivel joint with vertical swivel axis 7 Swivel joint with horizontal swivel axis 8 material supply hoses 9 Portal rail 10 Crossbar 11 robot arm 12 Arrow symbolizing the main working direction 13 nozzle carriers 14 first material application nozzle 15 second material application nozzle 16 threaded spindle 17 Wall thickness

Claims

[1] Print head for a material-depositing 3D printer with at least one first and at least two second (usually all capable of simultaneous material deposition) material deposition nozzles, which are held (directly or indirectly) on at least one nozzle carrier which is movable in the main working direction, characterized by , that at least the first material application nozzle is mounted and driven in such a way that, while it is in the process of applying material, it can be moved back and forth transversely (and usually perpendicularly) to the main working direction, preferably in a pendulum-like manner. [2] Printhead according to claim 1, characterized by , that at least one, preferably at least two of the second material application nozzles are held in such a way that they can also be adjusted transversely to the main working direction. [3] Printhead according to claim 2, characterized by, that the aforementioned second material application nozzles are mounted and driven in such a way that, while they are in the process of applying material, they can be moved transversely to the main working direction. [4] Printhead according to any one of the preceding claims, characterized by that the at least one first material application nozzle is positioned upstream of the at least two second material application nozzles in the main working direction. [5] Printhead according to any one of the preceding claims, characterized by , that the at least one first and the at least two further material application nozzles are arranged, designed and moved in such a way that the currently laid web of the at least one first material application nozzle is placed at certain intervals onto the webs laid in the previous work step by the at least two further material application nozzles and is then clamped from above by the webs currently laid by the at least two further material application nozzles. [6] Printhead according to claim 5, characterized by , that the at least one first and the at least two further material application nozzles are arranged so close together that the web currently laid by the at least one material application nozzle can connect with the webs currently laid by the at least two second material application nozzles without having cooled down or set (more than just insignificantly) before the webs from the at least two further nozzles arrive. [7] Printhead according to any one of the preceding claims, characterized by that the printhead has means by which (completely printhead-autonomous or with the additional help of an external control) the application quantity and / or application speed can be controlled for at least some of the material application nozzles. [8] Printhead according to any one of the preceding claims, characterized by, that the printhead has means by which (completely printhead-autonomous or with the additional help of an external control) at least some of the other material application nozzles can be operated independently of the rest of the other material application nozzles. [9] Printhead according to any one of the preceding claims, characterized by that the printhead has means by which (completely printhead-autonomous or with the additional aid of an external control) the at least one first material application nozzle can be moved independently of the other material application nozzles, preferably in such a way that it lays down wave-shaped paths during the feed of the printhead in the main working direction, preferably paths whose amplitude and / or frequency changes. [10] 3D printer with a print head according to one of the preceding claims. [11] 3D printer according to claim 10, characterized bythat the printer has a (fully configured) control system that drives at least one first material application nozzle in such a way that at least one wave layer can be printed from it, which is located between two - preferably essentially flat - cover layers and fuses with the cover webs at intervals. [12] 3D printer according to claim 10 or 11, characterized by that the printer has a (fully configured) control system that drives at least one first material application nozzle, taking into account the distance that at least two other material application nozzles currently have from each other. [13] 3D printer according to one of claims 10 to 12, characterized by that the printer has a (fully configured) control system that drives at least one first material application nozzle, taking into account the distance that at least two other material application nozzles currently have from each other. [14] 3D printer according to any one of claims 10 to 13, characterized by that the printer has a (pre-configured) control system that applies more or less printing material to at least one first material application nozzle depending on its current position. [15] Use of a 3D printer equipped with multiple material application nozzles capable of simultaneous material application for printing a structure and in particular a complete or partial building wall or a complete or partial boat hull with a wave pattern located between two - preferably substantially flat - deck layers in such a way that it repeatedly fuses with the deck layers at intervals. [16] Method for operating a printhead according to any one of claims 1 to 9 or for operating a 3D printer equipped with such a printhead according to any one of claims 10 to 14, characterized by, that material is applied simultaneously with at least three material application nozzles, wherein at least one first material application nozzle oscillates back and forth transversely to the main working direction between the extreme positions that define at least two further, preferably trailing, material application nozzles which move at least predominantly only in the main working direction.

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