Structure and method for applying particulate structural material in a 3D printer

Abstract

The present invention relates to a structure and a method for applying a particulate construction material in a 3D printer, the problem being based on the provision of a solution in which the forces acting on the already applied layer of particulate construction material (2) and on the areas of particulate construction material (2) that have already partially hardened are reduced when applying another layer of particulate construction material (2). On the part of the structure, this problem is solved in that, seen in the direction of movement (4) of the smoothing means (9), means are arranged in front of the smoothing means (9) for removing excess particulate material (2) from the pile (10) in front of the smoothing means (9). On the part of the method, this problem is solved in the work step of smoothing the particulate construction material (2) that is transferred by the transport device (1) onto the surface of the construction field (3) and accumulated in the pile (10) in front of the smoothing means (9), by controlling the height (H) of the pile (10) by partially removing particulate construction material (2) from the pile (10).

Description

[Technical field]

[0001] The present invention relates to a construction device for applying particulate construction material in a 3D printer, the construction comprising means for smoothing the particulate construction material transferred from a transfer device onto a construction field.

[0002] The invention also relates to a method for applying a particulate construction material in a 3D printer, in which the particulate construction material is applied layer by layer onto a construction field of the 3D printer. [Background technology]

[0003] For the production of single or mass-produced parts, workpieces or shapes, it is known to use so-called 3D printing or so-called 3D printing methods, in which three-dimensional parts or workpieces are produced layer-by-layer.

[0004] The formation of the layers is computer-controlled from one or more types of fluid or solid material according to predetermined means and forms. The reference values ​​for the part or workpiece (3D structure) to be printed may be provided, for example, by a so-called computer-aided design system (CAD: English computer-aided design).

[0005] When printing a 3D structure or part, a particulate building material, also called build material, is subjected to a physical or chemical hardening or melting process. As materials for such 3D printing methods, building or building materials such as unhardened deposits of plastics, synthetic resins, ceramics, minerals or sand, and metals are used.

[0006] Where 3D printing is carried out, various manufacturing processes are known.

[0007] However, some of these method processes include the method steps exemplified below. The partial or full application of a particulate construction material, also referred to as granular material or powdered build material, onto the so-called construction field, resulting in a layer of unhardened particulate material, the partial or full application of the particulate construction material including the transfer and smoothing of the particulate construction material. Selectively hardening a layer of applied, unhardened particulate structural material in predetermined partial areas, for example by selectively compressing, applying or applying a treatment agent, such as a binder, using a print head or by using a laser. Repeating the preceding method steps in another layer plane in order to form a part or workpiece layer by layer. For this purpose, it is provided that the part or workpiece to be formed or applied layer by layer on the construction field is lowered together with the construction field by one layer plane or layer thickness in each case, or the 3D printing device is raised relative to the construction field by one layer plane or layer thickness in each case, after which a new layer is applied partially or completely. This is followed by the removal of the unhardened, loose particulate structural material surrounding the manufactured part or workpiece.

[0008] Particulate construction materials are generally understood to be accumulations of individual particles of a material or material mixture, each of which has a three-dimensional extent. These particles may be understood to be predominantly round, elliptical or oblong particles, but also elongated particles, so that for such particles it is possible to express an average diameter, which is often in the range of 0.1 mm to 0.4 mm. Such particulate construction materials may be flowable.

[0009] From the prior art, various methods are known for producing 3D structures or for transporting and applying particulate construction material onto a construction field in order to produce 3D structures.

[0010] From DE 101 17 875 a method and device for applying a fluid and its use are known.

[0011] The method of applying a fluid particularly relates to particulate material being applied to the area to be coated, in which case the fluid is applied to the area to be coated in front of the blade in the direction of the blade's forward movement, and then the blade moves over the applied fluid.

[0012] The object is to provide an apparatus, a method and a use of the apparatus which make it possible to achieve a distribution of the flowable material on the area to be coated that is as even as possible.

[0013] To solve the problem, it is proposed that the blade undergoes a certain rotational vibration. The vibratory rotational movement of the blade causes the fluid attached to the area to be coated to be fluidized. This not only allows the particulate material, which has a strong tendency to agglomerate, to be applied as evenly and smoothly as possible, but also makes it possible to affect the compression of the fluid by the vibration.

[0014] In a preferred embodiment, it is provided that the application of the fluid on the area to be coated is carried out in excess. Thus, due to the constant movement of the blade, which oscillates in a certain rotational movement, the excess fluid is homogenized in front of the blade in the forward movement direction of the blade, in the roll formed from the fluid or particulate material by the forward movement of the blade. This allows the hollow spaces between the individual particle agglomerates that may possibly occur to be filled, and the larger agglomerates of particulate material are broken up by the movement of the roll.

[0015] Japanese Patent No. 6380948 relates to a powder material supplying device for a three-dimensional modeling facility that manufactures products made of powder material and that are three-dimensionally modeled. The modeling facility is capable of suppressing non-uniformity that occurs in the powder material layer and modeling products that are accurately modeled at a higher speed than before.

[0016] To this end, a powder material supplying device is disclosed, which has an outlet and a smoothing element. The powder material is transferred from the outlet onto a building table, and the smoothing element is arranged behind the outlet in the moving direction of the powder material supplying device. The smoothing element forms a powder material layer having a predetermined thickness on the building table of the powder material transferred from the outlet onto the building table. To remove the excess amount of powder material, a suction device is provided, which has a suction nozzle for sucking the excess amount of powder material.

[0017] From DE 10 2015 015 353 A1, a method and an apparatus for manufacturing three-dimensional parts are known. The problem to be solved is to provide a method and an apparatus for checking or, according to preferred embodiments, also controlling the process progress. To solve this problem, it is provided that a measurement of the excess amount of particulate material is carried out. It is also disclosed that the measurement is carried out at the end of the coater run and / or during the coater run, the measurement being spatially resolved and preferably across the entire coater width.

[0018] US 2004 / 0173946 A1 discloses a method for producing three-dimensional objects from particles using a layer-forming method (powder-based rapid prototyping additive method), in which the layer structure is monitored by an optical control device. The problem to be solved is to provide a method that allows a quality control of the applied layer before or after curing and from which repair measures can be derived. For this purpose, in particular suitable particles or binding liquids should be specified and suitable control devices should be indicated. To solve this problem, it is intended to take an optical image of the applied, smoothed and / or cured layer by means of a control device. The layer image is processed in such a way that defects arranged in the layer plane can be detected, in particular particle missing points or particle layer defects and structure defects. By particle missing points, both excess and shortage of particles in the layer are understood.

[0019] JP 2001-9921 A relates to a stereolithography apparatus for selectively curing a photocurable resin by irradiating it with light to produce a three-dimensional resin model. The problem to be solved is to provide a stereolithography apparatus capable of producing a highly accurate model. To solve this problem, a smoothing section is provided having a support section, a storage and transport section, and a grinding section, in which case the smoothing section can move on the resin surface at a moving speed. The grinding section scrapes off excess uncured resin, which is then transported through the storage and transport section. This material can be sucked up using a suction device.

[0020] US 2019 / 0193150 describes a system and corresponding method for additively manufacturing three-dimensional objects to improve the packing density of the powder bed used in the manufacturing process. The system and corresponding method allow for a denser packing of powder. Such a denser packing improves the mechanical interlocking of the particles, which leads to lower sintering temperatures and less deformation of the 3D object during sintering. An embodiment of the system has a means for adjusting the volume of powder dispensed on the surface of the powder bed to obtain an adapted and dispensed volume. Further, a means for distributing the adapted and dispensed volume is disclosed, which forms a flat volume for forming a flat powder layer with a controlled packing density on the surface of the powder bed. The controlled packing density allows for uniform shrinkage without deformation of the 3D object during sintering, which produces a high-quality 3D printed object.

[0021] From the prior art, various methods are known for applying or transferring particulate construction material in a 3D printer. Such means, hereinafter also called transfer devices, are described below. Of course, other means with the same function for transferring particulate construction material may be used without affecting the essence of the invention.

[0022] To apply a layer of particulate construction material, a transport device, as described, for example, in DE 10 2018 003 336 A1, moves horizontally over the construction field. The transport device exemplified here is a so-called fluidizer, in which the particulate construction material is discharged through an outlet and reaches as discharge the surface of the construction field, where a new layer of particulate construction material with a defined layer thickness is formed. In order to form a uniform layer of particulate construction material with a defined layer thickness, according to the prior art, means for smoothing the layer of particulate construction material, such as, for example, a roller or a blade, are generally also used.

[0023] The transport device has a funnel-shaped storage container for storing the particulate construction material and an opening or discharge port for transporting the particulate construction material, which is arranged in the area below the transport device. Furthermore, a discharge means is arranged in the area below the funnel-shaped storage container, which prevents the particulate construction material from inadvertently reaching the construction field from the application device.

[0024] The application of a new layer of particulate construction material onto the construction field is achieved in that the particulate construction material is released in the area of ​​the discharge means.

[0025] Simultaneously with the release at the discharge means, the transport device moves over the building field and a new layer of particulate building material is applied onto the building field.

[0026] As already mentioned, the particulate material applied in this way is smoothed or smoothed and hardened by a means for smoothing the layer of applied particulate material, such as a blade, and in the process a pile of excess applied particulate material is formed in front of this means, the height and shape of which are determined by the amount of excess applied particulate material by the transport device.

[0027] If the particulate construction material is not transferred in excess onto the surface of the construction field, defects may occur in which the particulate construction material is not formed with the desired layer thickness in the layer currently to be applied, so for reasons of reliability, more or excess particulate construction material is transferred from the transfer device onto the surface of the construction field.

[0028] When a means for smoothing the layer of applied particulate construction material, such as a blade, moves horizontally over the construction field, forces acting on the substrate are generated by the blade and the accumulation of excess applied particulate construction material formed in front of the blade. The substrate consists, for example, of a number of layers of already transferred particulate construction material, where the particulate construction material has been selectively hardened in partial regions in which the 3D structure to be produced is to be formed. The magnitude or value and direction of these forces acting on the substrate vary locally. The value of these forces depends, for example, on the inclination of the blade, on the height of the accumulation, which may be different at different points of the accumulation, on the movement speed of the blade over the construction field, and on the particle size and distribution of the particulate construction material. Thus, forces of different strengths act on the substrate, preferably at different points below the accumulation.

[0029] Such forces generally have a horizontal and a vertical component. H A horizontal component, called the force F, acts parallel to the surface of the construction field on the area of ​​the last applied layer of particulate construction material. H is due to the horizontal movement of a smoothing means such as a blade. V The vertical component, called the force F, acts perpendicular to the surface of the construction field or perpendicular to the last applied layer of particulate construction material. V is due to the gravitational force of the granular structural materials, especially those in the agglomeration. In fact, the force F H and force F V and are superimposed, resulting in a resultant force F R This resultant force F R is oriented at a given angle or perpendicular to the surface of the construction field. The angle is determined by the force F H and F Vand may vary at different points of the stack, especially along the longitudinal extension of the stack. R The value of may be different magnitudes at different locations.

[0030] Resultant force F acting on the substrate at a given angle to the surface of the applied particulate structural material R The sliding action, for example, on a layer of already applied particulate construction material, can be selectively partially hardened. This leads to dimensional inaccuracies in the 3D structure to be produced. If such inaccuracies exceed certain tolerances, the produced 3D structure can possibly no longer be used. Such tolerances in the production of the 3D structure can be in the range of, for example, less than ±0.5 mm, in particular less than ±0.3 mm.

[0031] What this means is that if the inaccuracy at just one point of the 3D structure to be manufactured is greater than ±0.5 mm, in particular greater than ±0.3 mm, the manufactured 3D structure can no longer be used.

[0032] Another challenge may result from too high friction forces between the particles of the particulate construction material itself or between the particles of the particulate construction material and the blades of the smoothing means, since this may result in unacceptable spot heating, which may impair, for example, the physical properties of the particulate construction material.

[0033] Thus, in the prior art, solutions are known which try to influence the size or amount of the piles before a smoothing means, such as a blade, or to keep them constant at a predefined size or amount. In such solutions, it may be envisaged to determine the size of the piles, for example by means of a camera and a suitable algorithm, and depending on the determined size of the pile, to influence the amount of particulate construction material transferred from the transfer device onto the surface of the construction field, thereby for example keeping the size of the piles constant. In this case, it may also be envisaged to keep the size of the piles to a minimum before the smoothing means, and thus the forces acting on the substrate to a minimum. Such a minimisation of the piles or the minimum necessary height Hmin is required to enable the layer of particulate construction material to be applied uniformly, with a defined layer thickness and without defects.

[0034] The disadvantages of such a solution are that it is cumbersome, expensive and requires a great deal of effort in open-loop and closed-loop control of the transport of the particulate construction material. Moreover, such a solution does not prevent the accumulation of different sizes along the longitudinal extension of the blade, which in practice occurs quite often. Thus, forces acting on the substrate with different magnitudes along the longitudinal extension of the blade, although they do affect the accumulation size precisely, are generated. This results in the underlying selectively hardened structure being subjected to locally different loads along the blade length.

[0035] Another drawback of the known prior art for applying particulate construction material in 3D printers is that the accumulation of particulate construction material is often no longer provided to the currently running manufacturing process for producing the 3D structure after passing through the construction field. The particulate construction material that is still in the accumulation after passing through the construction field can be collected, for example, in a collection vessel. To feed this collected particulate construction material again to the manufacturing process usually requires several process steps.

[0036] Therefore, there is a need to improve upon the prior art and thus to improve structures and methods for applying particulate build material in 3D printers. [Prior art documents] [Patent documents]

[0037] [Patent Document 1] German Patent No. 10117875 [Patent Document 2] Patent No. 6380948 [Patent Document 3] DE 102015015353 A1 [Patent Document 4] US Patent Application Publication No. 2004 / 0173946 [Patent Document 5] JP 2001-9921 A [Patent Document 6] US Patent Application Publication No. 2019 / 0193150 [Patent Document 7] DE 102018003336 Summary of the Invention [Problem to be solved by the invention]

[0038] The object of the present invention is to provide a structure and a method for applying particulate building material in a 3D printer, in which the forces acting on an already applied layer of particulate building material and on already partially hardened areas of the particulate building material are reduced when applying another layer of particulate building material.

[0039] In addition, the quality of the currently applied layers and the dimensional accuracy of the 3D structures thus produced should be improved.

[0040] Furthermore, the minimum required height H min It should be possible to guide at least a portion of the particulate construction material in the pile that is not required to form the pile back directly into the storage vessel of the transfer device. [Means for solving the problem]

[0041] The minimum height of the pile is H min Particulate structural material that is not required to form the matrix is ​​referred to as excess particulate material.

[0042] The method generally provides for a work step of smoothing a particulate construction material transferred from the transport device onto the surface of the construction field and accumulated in a pile before the smoothing means, in which this particulate construction material is at least partially removed or led out of the pile and guided back into a storage container of the transport device, for which corresponding suitable means are provided for removing or leading out the particulate material from the pile.

[0043] In this case, the control according to the method is carried out according to the minimum required height H min Only the excess particulate construction material that is not required for forming the particulate construction material is removed or led out of the pile and guided back into the storage container of the transport device, whereby the minimum required height Hmin of the pile is the height H of the pile that is required to be able to apply a layer of particulate construction material uniformly, with a given layer thickness and without defects.

[0044] It is contemplated that the amount of excess particulate construction material removed, e.g., aspirated, from the pile is controlled depending on the amount of particulate construction material transferred by the transfer device.

[0045] The amount of excess particulate material, i.e. the proportion of particulate material not required to properly form a new layer of particulate material, depends on the amount of particulate material transferred from the transfer device onto the surface of the construction field, and therefore the amount of excess particulate material removed or removed from the pile may be controlled depending on the amount of particulate material transferred.

[0046] Alternatively, it is contemplated that the amount of excess particulate structural material removed or drawn off from the pile is controlled depending on the height H of the pile.

[0047] The means for removing or drawing off the particulate construction material from the pile may be realized in various ways. For example, suitable suction means, brushes, squeegees, blades, shovels or trays may be provided for partially removing or drawing off the particulate construction material from the pile. Furthermore, mechanical conveying systems such as belt conveyor systems, bucket mechanism systems, screw systems, screw conveyor systems or vibrating conveyor systems may be used to convey the particulate construction material removed or drawn off from the pile into the storage vessel of the transfer device. Alternatively, pneumatic conveying systems such as compression conveyors, suction conveyors, suction compression conveyors or plug flow or tight flow conveyors may be used to convey the particulate construction material removed or drawn off from the pile into the storage vessel of the transfer device. In the following, the invention is described by way of example with suction means for drawing off the particulate construction material from the pile, but this does not limit the invention to this form of means for removing or drawing off the particulate construction material from the pile.

[0048] The height H and shape of the accumulation are determined according to the amount of granular construction material that is applied in excess by the transport device onto the surface of the construction field. The height H can be determined, for example, optically, and the suction device is controlled to determine the minimum necessary height H of the accumulation that is required to ensure that the layer of granular construction material is applied uniformly, with a defined layer thickness and without defects. min This may be achieved so that a certain height H of the accumulation is obtained, which corresponds to

[0049] It is further contemplated that the amount of excess particulate construction material removed or sucked out from the pile is controlled depending on one or more layers that may have so-called at-risk areas located below the layer produced in the smoothing work step.

[0050] Areas in which the application and smoothing of the particulate construction material in the current layer risks causing defects in the construction of the 3D structure of the layer located below are referred to as risk areas, where such defects are understood in particular to mean ruptures and / or sliding of areas or partial areas of the 3D structure to be produced.

[0051] Such risky areas are also areas where application of the substructures of the 3D structure to be produced on the small substructures of the underlying layer is to be performed. Such small substructures arise, for example, when the dimensions of the substructures arranged one above the other layer by layer are small, for example, such that only little mechanical strength is expected in the stacked structure of these substructures. Such little strength is possessed by substructures with the smallest possible dimensions, for example, in the range of 0.1 mm in length and 0.1 mm in width to dimensions in the range of 5 mm or more in length and 5 mm or more in width. These dimensions depend on the building material, the processing speed and the flow properties of the building material. Furthermore, such risky areas may include parts of the current layer due to, for example, complicated or complex 3D structures to be produced or poorly adhesive substrates located below the current layer, for example the surface of the structure field, or may be complete layers.

[0052] By analyzing the printing data present for the production of the 3D structure, such risk areas are known and can be taken into account when producing the 3D structure. The amount of excess particulate construction material removed or sucked out from the pile is controlled in such a way that, depending on the risk area, the amount of excess particulate construction material removed from the pile increases when the risk area is reached, thereby decreasing the height of the pile. The removal of such excess particulate construction material is performed in such a way that the minimum required height H of the pile, which should not be less than this, is reached. min This will be done taking into consideration the following:

[0053] When moving away from the risk area, the excess particulate construction material removed from the pile is reduced again to the height H of the pile, for example as it was before reaching the risk area.

[0054] This change in the build-up height H in the risk area can be coupled in time with a reduction in the speed of the working means of the 3D printer in this risk area, so that for example the application device and / or the smoothing means move at a reduced speed over the surface of the construction field and at the same time the build-up height H is reduced to a minimum.

[0055] Minimum required height of pile H min This reduction of the pile height H taking into account the above can take place already shortly before reaching the risk area, for which a corresponding preparation time or a distance between, for example, the application device and the risk area is determined.

[0056] The increase in pile height H when moving away from the edge of the risk area can be delayed by a coast time or a predefined distance between the risk area and the application device.

[0057] This general method may be implemented in a variety of configurations.

[0058] It is provided that the excess particulate material of the pile in front of the blade is collected, for example by suction, and guided back into a storage container of the transfer device. The particulate construction material applied in excess to the surface of the construction field by the transfer device reduces the minimum required height H of the pile in front of the smoothing means, for example the blade. min A pile is formed of the excess particulate material required for the formation of a new layer of particulate construction material. From this pile, the excess particulate material not required for the correct formation of the new layer of particulate construction material is sucked away. A pile of significantly reduced volume or a pile with significantly reduced height H remains.

[0059] According to the invention, it is provided that the excess particulate construction material of the pile in front of the smoothing means, such as a blade, is collected by a suction device, the smoothing means for the particulate construction material having a gap-like opening in the longitudinal extension of the blade, through which the excess particulate construction material is sucked from the pile and guided back into a storage container of the transfer device. For this purpose, the blade is designed to be partially hollow, in which case the blade has a gap-like opening for sucking the excess particulate construction material and one or more openings for the subsequent guidance of the particulate construction material towards a storage container for particulate construction material. For this purpose, the one or more openings are connected to a controllable means for generating a negative pressure, which may be arranged in the smoothing means. The excess particulate construction material is sucked from the pile by the negative pressure generated along the gap-like opening provided in the longitudinal extension of the blade and directed towards the pile.

[0060] For example, if the lower edge of the gap-like opening of the blade is positioned on the surface of the construction field at a predetermined distance A and the negative pressure generated is appropriately controlled, it is possible to reduce the height H of the accumulation so that the height H of the accumulation corresponds to the distance A on the surface of the construction field.

[0061] It is further provided that the blade is constructed in two pieces, consisting of a blade base body and a blade plate, in which case a gap-like opening on the side facing the accumulation is formed between the blade base body and the blade plate. By suitable positioning of the blade plate relative to the blade base body, the gap size or gap dimension can be determined.

[0062] Between the blade base body and the blade plate, a hollow space is formed, which has a gap on the inlet side and is connected to a suction device on the outlet side. The term inlet side is used in this case for the inlet, through which the excess particulate construction material reaches from the pile into the hollow smoothing means. The term outlet side is used in this case for the outlet, through which the excess particulate construction material is conveyed from the smoothing means, for example via a suction device and a corresponding connection, towards a storage container of a transfer device.

[0063] Alternatively, it is contemplated that the blade plate is variably spaced relative to the blade base body to form a gap, which may be accomplished, for example, when conditioning the blade prior to operation of the 3D printer, in which case the blade plate is appropriately mechanically attached.

[0064] In another embodiment, the blade plate is attached such that it can be slid or adjusted in position by suitable means for moving the blade plate, thereby changing the clearance relative to the blade base body, and such sliding or gap size change can be performed by means of moving the blade plate while the 3D printer is in operation.

[0065] In this manner, variables are provided, such as the amount of negative pressure generated or suction capacity and the size of the gap in the blades, to affect the amount of particulate matter to be sucked from the pile.

[0066] It is further provided that such a hollow blade, consisting of a blade base body and, for example, an adjustable blade plate, has a blade pocket arranged in the blade base body, which constitutes an area within the blade that is formed in the blade below the lower edge of the gap formed in the blade. When the particulate construction material is sucked through the gap and the approximately vertical area of ​​the partially hollow blade towards the storage container, some particles of the particulate construction material may not be sucked in any more or may fall downwards due to the gravity acting on them in the vertical area. In order to prevent these particles from falling back onto the construction field again, the area within the blade is configured approximately L-shaped and has a blade pocket, which at its lowest point is located below the lower edge of the gap formed, in which the falling particles are accumulated.

[0067] Alternatively, it is further envisaged that the excess particulate structural material of the accumulation is accommodated in front of the blade by a gap-like opening provided in the longitudinal extension of the blade, in which case the blade has a blade base body and a blade plate, in which case the blade cutter is arranged in the blade base body.

[0068] For this purpose, the blade is designed to be partially hollow, in which case the blade has a gap-like opening arranged above the blade cutter for sucking out excess particulate construction material and one or more outlet-side openings for further guiding the particulate construction material towards a storage container for the particulate construction material.

[0069] The blade cutter is arranged in the lower region of the blade base body, so that its lowest point or its lower edge is positioned on the construction field, and when the blade moves over the construction field with the blade cutter, a new layer of the applied particulate construction material with the set desired layer thickness is produced on the underside of the blade. Excess particulate construction material is conveyed in the direction of particle movement through the upper side of the blade towards the longitudinally extending opening with an adjustable gap size, via the suction device and the connection towards the storage container of the transfer device.

[0070] A particular advantage of this configuration is that the blade cutter can be replaced separately if it wears out during operation of the 3D printer: if there is no blade cutter in front of the blade base body, the blade base body will wear out, and in this case the blade base body must be replaced separately or together with the blade plate.

[0071] The wedge-shaped configured blade cutter has a thickness at its thinnest point, which projects furthest from the blade base body to which it is attached, of a value between 0.01 mm and 1.5 mm, preferably between 0.07 mm and 0.3 mm.

[0072] In order to prevent the particulate construction material present in the pile before the smoothing means, such as a blade, from moving away from the edge of the construction field and thus being lost, the smoothing means has a shaped contour guide on both sides or both ends, respectively. The shaped contour guide limits the pile laterally and prevents it from having a smaller height H in the edge area, where the particulate construction material could fall or flow out of the construction field. In this way, the loss of the particulate construction material is further minimized when the smoothing means passes over the construction field, since the shaped contour guide prevents the particulate construction material present in the pile from moving away laterally from the construction field and no longer being provided to the 3D printing process.

[0073] The shaped contour guide may be arranged on the blade plate and mechanically coupled to the blade plate. The shaped contour guide has, for example, a triangular lateral limit, with which it protrudes from the blade plate and forms a lateral limit for the build-up formed during operation of the 3D printer. The shaped contour guide may have a triangular base plate aligned parallel to the surface of the construction field, which base plate forms a smooth transition between the shaped contour guide and the smoothing means, in particular the blade plate.

[0074] For example, by monitoring the height H of the pileup and controlling the negative pressure to be generated, the minimum required height H min It is intended to form a stack having a minimum height H min The excess particulate construction material that is not required to form the pile is removed or sucked away from the pile. By reducing the height H of the pile to the minimum necessary, the forces F acting on the substrate, especially in the risk area, are reduced. H , F V , F R is reduced.

[0075] Thus, the sliding occurring in the layer of particulate construction material already applied, which can be partially selectively hardened, is reduced, which reduces the dimensional inaccuracies of the 3D structures to be produced, and the quality of the produced 3D structures is improved, since the production of the 3D structures is more precise.

[0076] The height H of the accumulation can be, for example, more than 10 mm, depending on the speed of movement of the smoothing means, such as a blade, over the construction field and on the amount of applied particulate construction material. By reducing the height H of the accumulation according to the invention, this height H can be reduced to significantly smaller values ​​of 8 mm, preferably 5 mm, and even more preferably 2 mm.

[0077] Depending on the blade geometry and the strength of the removal of the particulate construction material, for example by suction, accumulations can also be almost completely avoided, so that the accumulations have a height H corresponding to the average particle size of the particulate construction material, for example 0.5 mm, preferably 0.3 mm, more preferably even 0.15 mm.

[0078] It is further provided that the excess particulate construction material sucked out from the pile is guided back into the storage container of the transport device. By this direct return of the particulate construction material into the storage container of the transport device, the amount of particulate construction material to be prepared is reduced. For this direct return, the mechanical or pneumatic conveying systems already mentioned above can be used. A further advantage of this direct return is that the particulate construction material does not have to be fed first to a complex cleaning or treatment of the particulate construction material, as was necessary in the prior art.

[0079] In order to control the height H of the pile, it is contemplated to influence the means for generating a negative pressure and thus suck more or less excess particulate construction material from the pile.

[0080] The foregoing features and advantages of the present invention will be better understood and appreciated from a careful consideration of the following detailed description of the presently preferred, but non-limiting, exemplary embodiments of the invention in conjunction with the accompanying drawings, in which: [Brief description of the drawings]

[0081] [Figure 1] 1 illustrates an exemplary structure for transferring particulate build material in a prior art 3D printer. [Diagram 2] 1 shows a perspective view of a collection of particulate construction material on a construction field. [Diagram 3] 1 shows an exemplary decomposition of forces acting on a substrate when an implement such as a blade moves over a structural field. [Figure 4] 1 shows a structure having means for removing or transporting particulate construction material from the pile according to the prior art; [Diagram 5] 1 shows a first structure according to the invention having a suction device for sucking particulate construction material from a pile; [Figure 6] 1 shows another structure according to the invention having a suction device for sucking excess particulate construction material from the pile. [Figure 7] 1 shows a means according to the invention in a perspective view. [Figure 8] 8 shows the means according to the invention according to FIG. 7 in a top view. [Figure 9] 2 shows an exemplary prior art return guide of excess granular construction material from a pile into a storage container. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0082] 1 shows an exemplary structure 1 for transferring particulate construction material 2 in a 3D printer according to the prior art. Such a structure 1 is also called a transfer device 1. This structure 1 for transferring particulate construction material 2 is exemplary and may be replaced by other means of the same action without affecting the essence of the invention.

[0083] It is envisaged that the transport device 1 can move horizontally on the construction field 3 in a movement direction indicated by the arrow 4 .

[0084] The transfer device 1 is shown as recording the moment when the particulate construction material 2 leaves the storage container 8 through the outlet 5 and reaches the surface of the construction field 3 as a transfer section 6, whereby a new layer of particulate construction material 2 having a predetermined layer thickness 7 is formed there. To form this layer of particulate construction material 2 having a predetermined layer thickness 7, according to the prior art, generally also means 9 for smoothing the layer of particulate construction material 2, such as for example a blade, are used.

[0085] The transport device 1 has a hopper-like storage container 8 for storing the particulate construction material 2. This hopper-like storage container 8 extends elongately across the width of the construction field 3, in which case the length of the storage container 8 is many times its width.

[0086] The storage container 8 has an opening or outlet 5 in which outlet means (not shown in FIG. 1 ) are arranged, which prevent the particulate construction material 2 from inadvertently reaching the construction field 3 .

[0087] The application of the particulate construction material 2 onto the construction field 3 is achieved by controlling the discharge means in such a way that the particulate construction material 2 is released in the region of the discharge opening 5, whereby the particulate construction material 2 is discharged via the discharge opening 5 and reaches the construction field 3 forming a transfer section 6. At the same time, the transfer means 1 moves over the construction field 3 in the movement direction indicated by the arrow 4, and a new layer of particulate construction material 2 is applied onto the construction field 3. As already mentioned, the particulate construction material 2 thus applied is smoothed or smoothed and hardened by a means 9 for smoothing the applied layer of particulate construction material 2, which for example has a blade. For this purpose, the smoothing means 9 also moves over the construction field 3 in the movement direction indicated by the arrow 4, whereby the movement speed of the transfer device 1 over the construction field 3 and the movement speed of the smoothing means 9 can be identical.

[0088] In order to control the amount of particulate construction material 2 to be discharged, the discharge means is appropriately controlled, whereby, as a result, for example, more of the fluidized particulate construction material 2 can exit through the discharge port 5, and the size or amount of the accumulation 10 of particulate construction material 2 formed in front of the smoothing means 9 is increased.

[0089] Alternatively, the discharge means may be controlled so that the same or a smaller amount of particulate construction material 2 is discharged. Thus, it is achieved that the size or amount of the accumulations 10 of particulate construction material 2 formed upstream of the smoothing means 9 remains constant or is reduced.

[0090] Such control of the applied layer of particulate structural material 2 is insufficient if special demands are placed on the precision of the 3D structures to be produced, in which deviations during production of the 3D structures should be less than ±0.5 mm, in particular less than ±0.3 mm.

[0091] 1 shows a side view of a pile 10 of particulate construction material 2 on a construction field 3 in a 3D printer according to the prior art. A means 9 for smoothing the transferred particulate construction material 2, shown for example as a blade, moves over the construction field 3 in a movement direction indicated by the arrow 4.

[0092] In front of the means 9 for smoothing the particulate construction material 2, a build-up 10 of the particulate construction material 2 is formed. The area included in the build-up 10 is shown surrounded by a dashed line in FIG. 1 for better clarity.

[0093] As the means 9 for smoothing the transported particulate construction material 2 moves over the construction field 3 , a new layer of particulate construction material 2 is applied with a defined layer thickness 7 .

[0094] The stack 10 shown in Fig. 1 has a thickness T11, a width B12 and a height H13. The width B12 of the stack 10, which is not shown in Fig. 1, extends, so to speak, into the depth direction of the drawing in Fig. 1.

[0095] For example, if the height H13 of the accumulation 10 exceeds a required maximum value, the quality of the currently applied layer may be reduced, which in turn may affect the accuracy of the 3D structure to be manufactured.

[0096] The reason for this may be that the forces acting on the underlying layer of particulate structural material 2 are increased. Unacceptably high forces may result in, for example, uneven subsidence or compression of individual regions of the layer or layers of the applied particulate structural material 2. Alternatively, unacceptably high forces may affect the density of partial regions of the underlying layer or layers. In addition to affecting the particulate structural material 2, areas already hardened to form the 3D structure may also be affected. Such effects may lead to deviations in the dimensional accuracy of the 3D structure to be manufactured, for example, due to compression or sliding of such already hardened areas.

[0097] In order to avoid such effects on the 3D structure to be produced and to ensure a constant quality when applying the particulate structural material 2, the method ensures that the amount, volume or height H13 of the accumulation 10 is kept constant or controlled to a predetermined value, for example over the length of the smoothing means 9 or the width of the accumulation 10.

[0098] FIG. 2 shows a perspective view of a collection 10 of particulate building material 2 on a building field 3 in a 3D printer according to the prior art.

[0099] For the sake of clarity, Fig. 2 shows in a perspective view a part of a pile 10 of particulate construction material 2 above a construction field 3. The pile 10 is shown in front of the smoothing means 9 in the direction of movement of the smoothing means 9 indicated by the arrow 4. Such a smoothing means 9 is, for example, a blade, by means of which the particulate construction material 2 is smoothed or smoothed and compressed. Fig. 2 also shows the dimensions of the width B12, the thickness T11 and the height H13 of the pile 10. The dimensions of the thickness T11 and the height H13 may vary over the width of the blade 9 or over the width B12 of the pile 10, which is not shown in Fig. 2.

[0100] Figure 3 shows an exemplary decomposition of the forces acting on the substrate when a smoothing means 9, such as a blade, moves over the construction field 3. With regard to Figure 3, reference is made to the explanations in Figures 1 and 2, which have already described the components shown again in Figure 3.

[0101] The smoothing means 9 moves horizontally over the surface of the construction field 3, for example in the direction of movement indicated by the arrow 4. In front of the blade 9 a pile 10 is formed by the excess transported particulate construction material 2.

[0102] Forces are generated due to the movement of the blade 9, which may be arranged at an angle deviating from the vertical, and due to the weight of the transported particulate construction material 2 within the pile 10.

[0103] Such forces generally have a horizontal and a vertical component. H The horizontal component, denoted as F, acts on the area of ​​the last applied layer of particulate construction material 2 horizontally to the surface of the construction field 3. H is generated by the horizontal movement of the smoothing means 9 such as a blade.

[0104] In figure 3 the forces described here are exemplarily plotted at a point of application 14. The point of application 14 is located in the area of ​​the surface of the layer of particulate structural material 2 to be produced in the current working or coating process.

[0105] force F V The vertical component, written as F, acts perpendicular to the surface of the construction field 3 or perpendicular to the last applied layer of particulate construction material 2. V is caused by the weight of the particulate construction material 2, in particular the weight of the particulate construction material 2 present in the pile 10. In fact, the force F H and force F V and are superimposed, resulting in a resultant force F R is generated. The resultant force F R is oriented at an angle of 0° to 90° with respect to the surface of the construction field 3 or to a vertical line, not shown in FIG. 3. This angle is determined by the force F H and force FV and may vary at different locations of the stack 10, particularly along the width 12 of the stack 10. Similarly, the resultant force F R The value of may be different magnitudes at different locations.

[0106] In Figure 3, the resultant force F R is indicated by an arrow, for example at an angle of approximately 30° to the surface of the structure field 3 .

[0107] The resultant force F acting on the base layer R This can result in, for example, horizontal sliding of one or more layers of the already applied particulate construction material 2, which may be partially and selectively solidified, which impairs the dimensional accuracy of the 3D structure to be produced and reduces the quality of the produced 3D structure.

[0108] Figure 4 shows a structure according to the prior art, with means for removing or leading off particulate construction material 2 from a pile 10. In the example of Figure 4, the means for removing or leading off particulate construction material 2 is a suction device 15 for drawing particulate construction material 2 from the pile 10, shown partially in dashed lines.

[0109] The suction device 15 is arranged in the direction of movement 4 of the smoothing means 9, in front of the means 9 for smoothing the particulate construction material 2, such as a blade 9, above the pile 10. As already explained, in front of the blade 9 moving over the construction field 3 in the direction of the arrow 4, a pile 10 is formed having a thickness 11 and a height 13.

[0110] The suction device 15 has a connection 16. The suction device 15 may comprise means for generating a controllable negative pressure 17, not shown in Fig. 4. Alternatively, the suction device 15 is connected to the means for generating a controllable negative pressure 17 via the connection 16. The negative pressure generated by the means for generating a controllable negative pressure 17 sucks the excess particulate construction material 2 from the pile 10 in the direction of particle movement 18 indicated by the arrows.

[0111] The structural unit consisting of the suction device 15 and the connection 16 can have its distance to the surface of the pile 10 or the construction field 3 changed, as is shown by the double arrow in FIG.

[0112] 5 shows a first structure according to the invention with a suction device 15 for sucking excess particulate construction material 2 from a pile 10. As is already known, a smoothing means 9 moves over the construction field 3 in the movement direction indicated by the arrow 4, in which case a pile 10 is formed in front of the smoothing means 9.

[0113] In this embodiment, it is contemplated that the smoothing means 9 is constructed in two pieces and is formed by an L-shaped blade base body 19 and a movable blade plate 20. It is also contemplated that the blade plate 20 is movable in the direction indicated by the double arrow. The movement or sliding of the blade plate 20 is achieved by suitable means for moving the blade plate 20 in the direction indicated by the double arrow, which means are not shown in FIG. 5 in this case. Thus, by the movement or sliding of the blade plate 20, a change in the gap size of the gap 22 can be automatically performed.

[0114] The blade base body 19 is configured in an L-shape and has a blade pocket 21. The blade pocket 21 is molded into the two-piece blade 9 in an area that is lowest or spaced less from the surface of the construction field 3 than the lower edge 24 of the blade base body 9 at the location of the formed gap 22. If excess particulate construction material 2 sucked in through the gap 22 cannot be conveyed out of the suction device 15 via the connection 16 due to gravity and falls back towards the construction field 3, the excess particulate construction material 2 is accommodated in the blade pocket 21 and cannot slide back into the pile 10 through the gap 22.

[0115] As can be seen from FIG. 5, the lowest point of the blade pocket 21 is located below the lower edge 24 of the blade base body 19 at the location of the formed gap 22 with a predetermined distance 23 therebetween.

[0116] The lower edge 24 of the blade base body 19, which has a distance A to the surface of the construction field, is arranged or configured in the blade 9 in such a way that the height H13 of the pile 10 is determined by this lower edge 24, since the particulate construction material 2 located above the distance A can be sucked through the gap 22 and removed into the storage container 8 of the transport body 1. This lower edge 24, which extends parallel to the surface of the construction field, determines the height H13 of the pile 10, at least locally, of the minimum required height H13. min , the excess particulate material is sucked from the pile 10 at all points of its longitudinal extension or width B12, even if the height H13 of the pile 10 varies. min In this way, the pile 10 has a uniform height H12 along its longitudinal extension or width B12, so that the resultant force F acting on the layer of particulate structural material 2 is R It is achieved that the resultant force F R This improves the quality of the 3D structures to be manufactured, so that the 3D structures have smaller deviations or improved dimensional accuracy.

[0117] 6 shows another construction according to the invention with a suction device 16 for sucking excess particulate construction material 2 from the pile 10. The smoothing means 9 moves over the construction field 3 in the movement direction indicated by the arrow 4, in the course of which the pile 10 is formed in front of the smoothing means 9.

[0118] In this embodiment too, it is contemplated that the smoothing means 9 is of two-piece construction and is formed by an L-shaped blade base body 19 and a movable L-shaped blade plate 20. It is further contemplated that the blade plate 20 is movable in the direction indicated by the double arrow. The movement or sliding of the blade plate 20 is achieved by suitable means for moving the blade plate 20 in the direction indicated by the double arrow, which means are not shown here in FIG. 6. Thus, by the movement or sliding of the blade plate 20, a change in the gap size of the gap 22 can be automatically performed.

[0119] In this embodiment, the blade plate 20 has a blade pocket 21 molded into the blade 9. If excess particulate construction material 2 sucked in through the gap 22 cannot be transported out of the suction device 15 via the connection 16 due to gravity, but falls back towards the construction field 3, the excess particulate construction material 2 is contained within the blade pocket 21 and cannot slide back into the pile 10 through the gap 22.

[0120] The configuration shown in Fig. 6 has a blade cutter 25 arranged in the lower region of the blade base body 19. The blade cutter 25 is positioned with its lowest point or its lower edge on the construction field 3, so that when the blade 9 with the blade cutter 25 moves over the construction field 3, a new layer of the applied particulate construction material 2 is laid down below the blade cutter 25 with a defined and desired layer thickness 7. Excess particulate construction material 2 is conveyed in the direction of particle movement 18 via the upper surface of the blade cutter 25, which opens into an elongated opening with an adjustable gap size 22, via the suction device 15 and the connection 16 towards a storage container 8 of the transfer device 1, not shown.

[0121] The blade cutters 25 arranged on the blade base body 19 are mounted so that they can be individually replaced, if necessary, after they have undergone corresponding wear.

[0122] FIG. 7 shows a smoothing means 9 according to the invention in a perspective view, of which only the components that are important for the explanation are shown. The smoothing means 9 moves horizontally on a construction field 3, not shown, in a moving direction 4 indicated by an arrow. The smoothing means 9 also has a two-piece construction in this embodiment, that is to say with a blade base body 19 and a blade plate 20. Below the blade plate 20, an elongated gap 22 is formed between the blade plate 20 and the L-shaped blade base body 19. Through this gap 22, the excess particulate construction material 2, not shown, is sucked in, the particles moving in the direction of particle movement 18 indicated by an arrow. Through the connection 16, the sucked excess particulate construction material 2 leaves the smoothing means 9 and reaches a storage container 8, although in FIG. 7 the suction device 15 and the connection 16 are not shown for the sake of simplicity of the illustration.

[0123] In order to prevent the particulate construction material 2 in the pile 10 (not shown) before the smoothing means 9 from moving away from the edges of the construction field 3 (not shown) and thus being lost, the smoothing means 9 has shaped contour guides 26 on both sides or ends thereof, respectively. By means of these shaped contour guides 26, the pile 10 is limited laterally and prevented from having a lower height H13 in the edge regions, where the particulate construction material 2 could fall or drop out of the construction field 3. Furthermore, in this way, losses of the particulate construction material 2 when the smoothing means 9 passes through the construction field 3 are minimized.

[0124] In this configuration, the blade plate 20 can still slide, thus adjusting the gap size of the gap 22. This option is not shown in FIG.

[0125] Furthermore, the blade base body 19 or the blade plate 20 may have a blade pocket 21 .

[0126] It is also possible to consider a configuration in which the blade cutter 25 is disposed at the lower end of the blade base body 19 .

[0127] In figure 8 the means according to the invention from figure 7 is shown in a top view. The blade base body 19 and the blade plate 20 can be seen, which together form the smoothing means 9.

[0128] At the end of the smoothing means 9, a contoured guide 26 is arranged which limits the accumulation 10 laterally (not shown). In this way, it is prevented that the particulate construction material 2 in the accumulation 10 moves away laterally from the construction field 3 and is therefore no longer available for the 3D printing process.

[0129] The shaped contour guide 26 may be arranged on the blade plate 20 or on the blade base body 19 and mechanically connected thereto. The shaped contour guide 26 has, for example, a triangular lateral limit, with which it protrudes from the blade plate 20, which limit forms a lateral limit of the buildup 10 formed during operation of the 3D printer. The shaped contour guide 26 may have a triangular base plate aligned parallel to the surface of the construction field 3, which base plate forms a smooth transition between the shaped contour guide 26 and the smoothing means 9, in particular the blade base body 19.

[0130] 9 shows, by way of example, the return guidance of excess particulate construction material 2 from a pile 10 into a storage container 8 in the prior art. FIG. 9 is not to scale and does not show the actual spacing between the structures, but is merely used to illustrate the principle of returning excess particulate construction material 2 into the storage container 8.

[0131] Figure 9 shows a transfer device 1 arranged on a construction field 3. The transfer device 1 is already known from Figure 1 and therefore does not need to be described in further detail. In the right part of Figure 9, the construction known from Figure 4 is illustrated with a suction device 15 for sucking particulate construction material 2 from the pile 10.

[0132] The excess particulate construction material 2 removed or sucked from the pile 10 formed upstream of the smoothing means 9 reaches a storage container of the application device 1 via the suction device 15, the connection 16 and the line 27. The excess particulate construction material 2 is thus directly fed or guided back by the application device 1 to the process of applying the particulate construction material 2.

[0133] In Fig. 9, for example, a means 17 for generating a negative pressure is arranged in the line 27. Alternatively, such a means 17 may be arranged in the suction device 15. Alternatively, more than one such means 17 may be arranged, for example at both ends of the line 27. It is important that such a means 17 generates a controllable negative pressure so that the excess particulate construction material 2 is removed from the pile 10 and conveyed into a storage container 8 of the transfer device 1, as shown, for example, in Fig. 9. The smoothing means 9 shown in Fig. 9 can be replaced by the smoothing means 9 according to the invention shown in Fig. 5, while still retaining the functionality of returning the excess particulate construction material 2 from the pile 10 into the storage container 8. [Explanation of symbols]

[0134] 1 Transfer device 2. Particulate structural materials 3 Structure Fields 4 Arrows / Movement Direction 5 Outlet 6 Transfer section 7 layer thickness 8. Storage Containers 9 Smoothing tools / blades 10 Accumulation 11 Thickness T 12 Width B 13 Height H 14. Area of ​​action 15 Suction device 16 Connection 17 Means for generating controllable negative pressure 18 Direction of particle motion 19 Blade Base Body 20 Blade plate 21 Blade Pocket 22 Gap size / gap 23 intervals 24 Lower edge 25 Blade Cutter 26 Contour Shaping Guide 27 Conduit

Claims

1. A structure for applying a particulate construction material (2) in a 3D printer, the structure having a means (9) for smoothing the particulate construction material (2) transferred from a transfer device (1) onto a construction field (3), the smoothing means (9) has an inlet gap (22) extending along the longitudinal extension of the smoothing means (9), through which surplus particulate construction material (2) is sucked from a pile (10) located in front of the smoothing means (9) in the direction of travel (4); The smoothing means (9) has a suction device (15) arranged on the outlet side, The smoothing means (9) comprises a blade base body (19) and a blade plate (20), between which a hollow space is formed, the hollow space being connected at its inlet side to the gap (22) and at its outlet side to the suction device (15); The blade plate (20) is arranged slidably relative to the blade base body (19), and the gap size of the gap (22) changes due to the sliding of the blade plate (20) relative to the blade base body (19). A structure characterized in that

2. 2. The structure according to claim 1, characterized in that the suction device (15) is connected via a connection (16) to a storage container (8) of the transfer device (1) in order to guide excess particulate construction material (2) from the pile (10) back into the storage container (8), and that means (17) for generating a negative pressure are arranged in or adjacent to the smoothing means (9) or in or adjacent to a line (27) connected to the smoothing means (9).

3. 3. A structure according to claim 1 or 2, characterized in that in the blade plate (20) or in the blade base body (19) a blade pocket (21) is arranged.

4. 4. The structure according to claim 1, wherein a blade cutter (25) is arranged on the blade base body (19) and / or at least one shaped contour guide (26) is arranged on the blade base body (19) or on the blade plate (20).

5. A method for applying a particulate construction material (2) in a 3D printer, comprising applying the particulate construction material (2) layer by layer onto a construction field (3) of the 3D printer, the method comprising: in a work step of smoothing the particulate construction material (2) transferred by the transfer device (1) onto the surface of the construction field (3) and accumulated in a pile (10) before the smoothing means (9), the height H (13) of the pile (10) being controlled by partially removing the particulate construction material (2) from the pile (10), Guiding the particulate construction material (2) partially removed from the pile (10) back into the storage container (8) of said transfer device (1); 2. A method according to claim 1, characterized in that excess particulate construction material (2) is sucked from the pile (10) through a gap (22) of variable gap size arranged in the smoothing means (9) and guided back into the storage container (8) of the transfer device (1).

6. The minimum required height H of the pile (10) ｍｉｎ 6. The method according to claim 5, characterized in that only the surplus particulate construction material (3) that is not required for forming the particulate construction material is guided back into the storage container (8) of the transfer device (1).

7. The minimum required height H of the pile (10) ｍｉｎ 7. The method according to claim 5 or 6, characterized in that H (13) of the accumulation (10) is required to be able to apply a layer of particulate construction material (2) uniformly, with a predetermined layer thickness (7) and without defects on the surface of the construction field (3).

8. 8. The method according to claim 5, further comprising sucking excess particulate construction material (2) from the pile (10) in the region preceding the smoothing means (9) in the direction of movement (4) of the smoothing means (9) and guiding it back into the storage container (8) of the transport device (1).

9. The amount of excess particulate construction material (2) to be sucked in is depending on the amount of particulate construction material (2) transferred by the transfer device (1), or Depending on the height H (13) of the pile (10), or Depending on the layer or layers located below the layer produced in the smoothing process, 9. The method according to claim 5, further comprising controlling

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