METHOD FOR PRODUCING A THREE-DIMENSIONAL MOLDED OBJECT BY METHOD OF LAYER-PAYMENT MATERIAL

Description

[0001] The invention relates to a method for producing a three-dimensional shaped article by layered material application, wherein geometric data for the shaped article, a carrier part with a base surface for receiving the three-dimensional shaped article, a solidifiable liquid or flowable first material, a solidifiable, liquid, flowable, pasty or powdery second material and a solvent are provided in which the solidified first material is soluble.

[0002] In such a process known from practice, liquid polymers which can be solidified by exposure to ultraviolet radiation are used as the first and second materials. In the previously known process, a first material layer is first applied to the base surface of the carrier part by spraying droplet-shaped portions of the first and second materials onto different locations on the base surface using an inkjet printer. The locations at which the material droplets consisting of the different materials are applied to the base surface are selected depending on the provided geometric data for the molded article to be produced such that the regions of the material layer consisting of the second material form a bottom layer of the molded article to be produced.The first material serves as a support material, which is applied to the base surface at locations where no second material is applied and over which the molded article, after the application of another layer of the first material, exhibits overhangs that are to be supported by the support material until all material layers have solidified. The resulting bottom layer of material is irradiated with ultraviolet radiation in a further step to solidify the polymers contained in the first and second materials by crosslinking.

[0003] After the bottom layer of material has been completed, further layers of material are applied and solidified in a similar manner until all layers of the molded article have been produced and solidified. The resulting stack of layers is then brought into contact with the solvent until the first material dissolves. The second material is insoluble in the solvent.

[0004] The previously known process allows for the comparatively cost-effective production of three-dimensional molded objects as prototypes or in small batches. The use of UV-curable polymers and the high printing resolution enable good surface quality. However, high-resolution 3D printing requires a very low viscosity of the polymers so that they can be applied through fine nozzles onto the base surface or a solidified material layer located thereon.

[0005] In inkjet printing, nozzles can typically handle a maximum viscosity of 25 mPa s. Higher viscosities are generally not jettable. Objects created from such materials have only minimal durability and can only serve as demonstration objects.

[0006] It is also already known in practice to produce an injection mold for an injection molding machine by layering material from a solidifiable liquid polymer using an inkjet 3D printer. The injection mold has two mold parts, between which a cavity is formed, containing a three-dimensional negative mold of a molded article to be produced in the injection molding machine. The injection mold is produced in the 3D printer by applying a plurality of layers of the polymer, which is applied in liquid form using nozzles to a base surface or a previously applied, solidified layer of material. After each layer of material has been applied, the still-liquid polymer is irradiated with UV light to crosslink it and thereby solidify the respective material layer. Further layers of material are then applied and solidified in a similar manner until the injection mold is complete.The injection mold is then removed from the 3D printer and installed in the injection molding machine, where a hot plastic, different from the polymer, is injected into the cavity through injection openings provided in the mold. After the cavity is filled with the plastic and the plastic has cooled, the injection mold is opened, and the molded article is ejected from the cavity using ejectors. This process has the disadvantage that molds produced using 3D printing have a very limited lifespan due to the high temperature of the filling material and must be replaced after approximately 10 to 100 injection molding processes. Furthermore, installing the injection mold in the injection molding machine is relatively time-consuming. This is particularly disadvantageous when manufacturing a molded article individually.

[0007] Other known technologies that use solid materials as build materials usually involve melting thermoplastics and applying them layer by layer through a nozzle or in powder form using a sintering process. However, this relatively good resilience comes at the expense of printing time (very slow) or low resolution or surface quality.

[0008] The stereolithography process offers a slight advantage, allowing the processing of higher viscosities. This advantage arises from the fact that the materials do not need to be sprayed through a nozzle, but are crosslinked according to specifications in a polymer container using an external UV beam. Two-component UV polymers with even more enhanced properties can also be processed with this process. This also improves the durability of the molded parts. The disadvantages, however, are: large quantities of material required to create an object, limited curing time for the two-component mixture, and high material consumption (precluding reuse of unused polymers). All of this significantly increases the costs of part production.

[0009] With the exception of the inkjet process, all known 3D technologies have another serious drawback: they are not multi-material capable. This means that only one type of material can be used at a time. This severely limits the process's industrial usability.

[0010] WO 2015 / 105047 A1 discloses a method for producing a three-dimensional molded article by layered material application, in which a carrier part with a base surface for receiving the three-dimensional molded article, a first material, a second material, and a solvent in which the solidified first material is soluble are provided. In the method, to produce the individual molded article layers, material portions of the first and second materials are simultaneously applied to the base surface or a solidified material layer of the three-dimensional molded article located thereon in such a way that a sacrificial layer is produced from the first material and an outer layer of the molded article is produced from the second material. The outer layer of the molded article has an outer edge adjacent to the sacrificial layer and an inner edge that defines a cavity.After the outer layer and the sacrificial layer have solidified, the cavity is filled with a third powdered material, which is then brought into contact with a binder ink to solidify the powdered material and bond it to the outer layer and, if applicable, to the already solidified layer beneath the powdered material. After all molded article layers have been produced in this way, the sacrificial layer is removed in a further process step by dissolving it in the solvent.

[0011] In a process known from DE 10 2015 212 569 A1, an object shell wall having a cavity is first produced on a base surface by repeatedly depositing and solidifying a first material in layers. The cavity is then filled with a solidifying second material. In a third process step, a solidified filler material region projecting vertically above the object shell edge is removed, so that a solidified filler material surface flush with the mold shell edge is formed. The process of layer-by-layer deposition and solidification of the first material is continued along the upper object shell edge, and further filler material is poured into the space delimited by the object shell edge thus raised. The solidified filler material region subsequently projecting above the object shell edge is removed in a further process step.These steps are repeated until the desired height of the molded object is reached.

[0012] US 2013 / 0011562 A1 discloses a method for producing a three-dimensional molded article by layer-by-layer material deposition, in which the individual material layers are each produced by applying a first material. After each material layer has been applied, a portion of the material layers is removed. This portion is filled with a second material that is soluble in a solvent. The thickness of the resulting layer is then reduced to a desired level. Further material layers are produced in a similar manner until all layers of the molded article are completed. In a further process step, the second material is removed by contacting it with the solvent.

[0013] The object of the invention is therefore to provide a method of the type mentioned at the outset with which mechanically stable and resilient three-dimensional shaped objects can be printed with high resolution.

[0014] This object is achieved with the features of patent claim 1. According to the invention, a method for producing a three-dimensional molded article by layer-by-layer material application is provided, in which geometric data for the molded article, a carrier part with a base surface for receiving the three-dimensional molded article, a solidifiable, liquid or flowable first material, a solidifiable, liquid, flowable, pasty or powdery second material and a solvent are provided, wherein the second material in the solidified state has a higher strength than the solidified first material, wherein the solidified first material is soluble in the solvent, a) wherein, to form a negative mold layer consisting of the first material, material portions of the flowable first material are applied to the base surface and / or a solidified material layer of the three-dimensional molded article located thereon in accordance with the geometric data such that the negative mold layer has at least one cavity on its surface facing away from the base surface, which cavity has a negative mold of a material layer of the molded article to be produced, b) wherein the negative mold layer is solidified, c) wherein, to form a molded article layer, the cavity is filled with the second material such that the negative mold is transferred to the molded article layer as a positive mold by molding the solidified first material, d) wherein the second material filled into the cavity is solidified,e) wherein overhanging regions of the solidified negative mold layer and / or the solidified molded article layer are removed by machining, f) wherein steps a) to e) are repeated at least once, g) wherein the negative mold layers are brought into contact with the solvent in such a way that the solidified first material dissolves in the solvent.

[0015] According to the invention, a hybrid process is provided in which materials with different properties are processed using different printing methods and / or applied layer by layer to the base surface or a solidified material layer located thereon of the three-dimensional molded object using different printing devices. This can be done in a continuous 3D printing process, i.e., the process can be carried out entirely in one 3D printing station. No further manufacturing process is necessary outside of the 3D printing station.

[0016] The first material can be very low-viscosity or thin-flowing, or highly fluid, because it serves solely to create a mold for the second material. Due to the low viscosity or high flowability of the first material during application to the base surface or an already solidified material layer of the three-dimensional molded object located thereon, the mold can be printed using a digital printing process with high resolution and surface quality by applying a plurality of correspondingly small portions of the first material to the base surface or the solidified material layer of the three-dimensional molded object located thereon.

[0017] Only low demands are placed on the mechanical stability and strength of the material layer of the mold consisting of the first material, since the mold only has to carry the second material and absorb any forces exerted on the first material during the printing process intended for applying the second material. By solidifying the first material, it achieves sufficient strength to be able to serve as a mold for the second material. The mechanical strength of the first material in its solidified state has no influence on the mechanical stability of the molded article formed from the solidified layers of the second material, because the first solidified material is removed from the molded article by dissolving it in the solvent after all material layers have been applied. The solidified second material is insoluble in the solvent.

[0018] The second material is the actual building material for the molded object and can have different properties, especially a higher viscosity than the first material. Since the second material is geometrically shaped by molding the form made from the first material, it is not necessary to apply small portions of the second material to the base surface or the solidified material layer of the three-dimensional molded object on top of it in order to achieve a high print resolution. Instead, a highly viscous second material can also be used. This makes it possible to achieve high mechanical stability and strength of the molded object. If required, it is even possible for the second material to contain a mixture of at least two different highly viscous substances and / or at least one additive to increase the material strength. The second material can also be applied to the base surface or the solidified material layer of the three-dimensional molded object using a digital printing process.The second material can be selectively applied to the solidified material layer of the three-dimensional shaped object located thereon, i.e., by applying a large number of material portions to different locations selected according to the geometric data provided for the shaped object. However, it is also possible to apply the second material to the base surface or the solidified material layer of the three-dimensional shaped object located thereon using an analog printing process. It is even possible to apply two or more components of the second material to the base surface and / or a solidified material layer located thereon in order to produce a shaped object containing several different components. This type of multi-material capability can be achieved by connecting several printing modules for the second material in series.In this way, different mechanical and / or electrical properties and / or different colors can be achieved.

[0019] Since, in the method according to the invention, preferably after printing each individual material layer, regions of the solidified negative mold layer and / or the solidified molded article layer that protrude beyond a plane arranged at a predetermined distance from the base surface, preferably parallel to it, are removed by machining, the individual layers of the molded article run exactly parallel or are arranged in a predetermined arrangement relative to one another and have a predetermined layer thickness. Furthermore, the machining removes "contamination" that can occur on the surface of the uppermost solidified layer of the first material when the second material comes into contact with this surface when the cavities are filled with the second material.The removal of the regions protruding beyond the plane thus ensures that the mixed layer consisting of the solidified first and second materials always has the desired thickness and is free of second material insoluble in the solvent on the surface of the first material. This enables very precise and distortion-free production of the molded article. The material removal by machining is preferably carried out using a so-called thickness milling cutter / polisher. Step e) of patent claim 1 is preferably carried out after the application of each individual material layer of the first material. The regions of the solidified negative mold layer and / or the solidified molded article layer protruding beyond the plane arranged at the predetermined distance from the base surface are preferably removed completely.Thus, after the removal of the protruding areas, both the uppermost negative mold layer and the uppermost molded article layer are flush with the plane arranged at a predetermined distance from the base surface.

[0020] In the method according to the invention, the areas of the solidified negative mold layer and the solidified molded article layer that extend beyond the plane arranged at the predetermined distance from the base surface, preferably parallel to the base surface, are removed by machining after each application of a molded article layer. Using the method according to the invention, molded articles can therefore be manufactured entirely in one printer – without the need for any other process.

[0021] In a preferred embodiment of the invention, the material portions of the first material are preferably applied to the base surface and / or the solidified negative mold layer and / or a solidified molded article layer located thereon by means of an inkjet printing process or by means of electrophotography, wherein the first material is a material that can be solidified by the action of energy and is subjected to the energy to solidify the negative mold layer. Preferably, the second material is also a material that can be solidified by the action of energy and is subjected to the energy after being filled into the cavity. The energy can in particular comprise radiation and preferably optical radiation, such as UV radiation.

[0022] In an advantageous embodiment of the method, the viscosity of the second material in the unsolidified state is higher, optionally at least 10 times as high, in particular at least 200 times as high and preferably at least 2000 times as high as the viscosity of the first material in the unsolidified state and / or the flowable first and the flowable, pasty or powdery second material have a solids content, wherein the solids content of the second material in the unsolidified state of this material is higher, optionally at least 10 times as high, in particular at least 200 times as high and preferably at least 2000 times as high as the solids content of the first material in its unsolidified state. This enables the production of a shaped article which has a high surface quality and accuracy and at the same time excellent mechanical strength.Furthermore, the second material can be provided with solid content (additives) in spherical or fiber-like form, which significantly increase the mechanical and / or electrical properties compared to a corresponding material without solid content.

[0023] In an expedient embodiment of the invention, the first material has a working viscosity suitable for jetting, which is less than 1000 mPa s, in particular less than 100 mPa s, optionally less than 30 mPa s and preferably less than 10 mPa s and is applied in the form of liquid droplets with a resolution of at least 360 dpi (254 dpi = 100 dpc), in particular at least 720 dpi and preferably at least 1440 dpi to the base surface and / or the solidified material layer located thereon of the three-dimensional molded article. This enables a high surface quality of the molded article. The second material is preferably heated to a working temperature compared to room temperature in order to change its flowability, preferably to increase it or reduce its viscosity. The second material, heated to working temperature, is then applied to the base surface or a solidified material layer located thereon.

[0024] In a further development of the invention, the second material is applied to the negative mold layer by means of a selective, digital coating / dosing process depending on the geometric data such that at least a portion of the flowable, pasty, or powdery second material is dispensed into the at least one cavity, and areas of the negative mold layer located preferably outside the cavity are not brought into contact with the second material, or only slightly so. The second material is therefore preferably dispensed only to the areas where cavities are located. The second material can be filled into the cavities using nozzles that can be adjusted into an open and a closed position by means of a valve or similar actuating device. The valves can be synchronized depending on the relative position between the cavities and the dispensing openings of the nozzles using a controller.This is an advantage compared to analogous coating processes, in which the second material is applied over a large area both inside and outside the cavities. The second material can exhibit different properties than the first material when poured into the cavities. In particular, the second material can have a higher viscosity than the first material when applied to the base surface or a solidified material layer located thereon of the three-dimensional molded article.

[0025] In a preferred embodiment of the invention, the second material is a composite comprising a fluid and at least one additive, wherein the fluid has a viscosity of at least 50 mPa s and preferably of at least 1000 mPa s at room temperature, and wherein the additive comprises solid particles arranged in the fluid. The solid particles can comprise fibers, in particular carbon fibers, nanotubes, glass spheres, graphene, styrene block copolymers, in particular styrene-ethylene-butylene-styrene (SEBS), nano / micro-particles of solids as fillers and / or highly branched polyesterols and / or mixtures thereof. The composite can be filled into the cavity(ies) at room temperature or heated to a temperature higher than room temperature.

[0026] In a preferred embodiment of the invention, the second material has a higher viscosity and / or a higher solids content than the first material, wherein both the first and the second material are applied to the base surface and / or a solidified negative mold layer and / or molded article layer located thereon by means of an inkjet printing process, wherein in the inkjet printing process the first material is ejected from at least one first nozzle and the second material from at least one second nozzle, and wherein the outlet opening of the second nozzle has a larger cross-section and / or is subjected to a higher working pressure than the outlet opening of the first nozzle, wherein in particular the diameter of the outlet opening of the second nozzle is larger than that of the outlet opening of the first nozzle.An inkjet printing process is understood to be a printing process in which the second material is ejected from the nozzle in pulses and / or in portions by means of a piezoelectric activator (jetting). The larger cross-section and / or higher working pressure of the second nozzle enables inkjet printing of the highly viscous second material. The smaller cross-section of the outlet opening of the first nozzle compared to the cross-section of the outlet opening of the second nozzle and / or the higher working pressure of the second nozzle compared to the working pressure of the first nozzle enables the first material to be applied with high resolution to the base surface or a solidified material layer of the three-dimensional molded object located thereon.

[0027] The nozzles are placed a short distance from the surface to which the second material is to be applied. If a cavity is located beneath the nozzle, the flow of the second material from the nozzle's material channel is activated. The second material is extruded from the nozzle, and when the surface is moved relative to the nozzle, a strip of the second material is deposited onto it. After deactivating the material feed, the nozzle moves over the surface without dispensing any material.

[0028] In a further development of the invention, the second material is subjected to gas pressure, and the second material thus pressurized is guided via at least one valve to at least one nozzle, wherein the outlet opening of the nozzle is positioned along the base surface relative to the carrier part, and the valve is controlled as a function of the geometric data provided for the molded article to be produced and as a function of the relative position between the nozzle and the carrier part such that the material flow is released when the outlet opening is positioned at the cavity, and the material flow is blocked when the outlet opening is not positioned at the cavity. The valve can be actuated electromagnetically or by means of a piezo element.

[0029] Preferably, the outlet opening of a nozzle is moved relative to the carrier part along a continuous line running within the cavity, and the liquid, flowable, or pasty second material is continuously dispensed along this line from the outlet opening into the cavity. This enables continuous material application and thus rapid work progress when filling the cavity(ies) with the second material. The second material can be fed to the nozzle using a micropump known per se and suitable for a continuous conveying process, or by subjecting the second material to gas pressure. The second material is conveyed out of the nozzle channel either directly by a piezo activator for high viscosities, by a piezo activator for a nozzle-channel slide (closes / opens the nozzle channel), or is pressed into the channel by compressed air.The compressed air can be activated electromagnetically by a solenoid valve.

[0030] In an advantageous embodiment of the invention, a carrier film is provided on which the second material is arranged, wherein the second material has a higher viscosity than the first material and / or contains a higher solids content than the first material, wherein the carrier film is positioned on the cavity for filling the cavity with the second material such that the second material located on the carrier film faces the cavity, wherein an energy beam, to which the carrier film is permeable, is directed onto the carrier film such that the second material on the side of the carrier film facing the cavity is liquefied by heating and released into the cavity. The second material is therefore preferably selectively filled into the cavities by means of a transfer printing process. A laser beam is preferably used as the energy beam. However, it is also conceivable for the energy beam to be an electron beam.The energy beam can be deflected from a neutral position during material application to position it at different locations on the carrier film. The deflection can be performed depending on the geometric data provided for the molded article and the relative position between the energy beam in the neutral position and the carrier part. In the case of a laser beam, the deflection can be achieved using adjustable optics, in particular a galvanometer mirror and / or a polygon mirror. If an electron beam is used as the energy beam, it is advantageously deflected by a magnetic field.

[0031] In a further development of the invention, the second material is filled into the cavity using a flexographic printing, gravure printing, offset printing, screen printing, laser transfer, micro-dispensing process, or a doctor blade or chamber doctor blade. The second material is thus filled into the cavity(ies) using an analog printing process. This enables high printing speeds due to the flat printing.

[0032] In a further advantageous embodiment of the invention, the second material is a thermoplastic that is liquefied by heating, then poured into the cavity, and subsequently solidified by cooling. In this case, no UV radiation source is required to solidify the second material; it is simply cooled.

[0033] It is advisable to clean the topmost solidified negative mold layer and / or the topmost solidified molded article layer of any chips generated during the machining process. This results in a flat and clean surface onto which another layer of material can be applied with great precision.

[0034] In a preferred embodiment of the invention, the carrier part having the base surface is rotated about a rotational axis during material application and, if appropriate, during the solidification of the materials, and preferably displaced along the rotational axis. This enables uninterrupted printing of a plurality of superimposed material layers. This enables rapid material application.If the second material is filled into the cavity by means of a transfer printing process, the energy beam can be positioned successively at several material delivery points on the carrier film, each of which is arranged above an associated application point for the material, in order to heat the second material on the carrier film by means of the energy beam such that it is transferred into the cavity located at the application point, wherein the power of the energy beam is adjusted such that when the energy beam is positioned at a first material delivery point that is further away from the axis of rotation than a second material delivery point, the energy beam has a greater power than when the energy beam is positioned at the second material delivery point. This power adjustment has the advantage that the same amount of material is delivered at each material delivery point.This is primarily necessary when used on a rotating platform where the inner diameter is smaller than the outer diameter, which consequently requires a narrower beam on the inside than on the outside.

[0035] Exemplary embodiments of the invention are explained in more detail below with reference to the drawings. They show: Fig. 1 shows a preferred device in polar design for producing a three-dimensional shaped article by layer-by-layer material application, wherein the device has different dispensing devices for dispensing different liquid and solidifiable materials, Fig. 2 shows a side view of a device for producing a three-dimensional shaped article, wherein the device has a first dispensing device which has nozzles for layer-by-layer application of a liquid first material and a second material application station designed as a flexographic or gravure printing device for applying a liquid second material, Figs. 3A to 3F show a cross-section through a shaped article during different process steps of its production, Figs. 4 and 4A show a side view of a thickness milling cutter during the milling of a material layer, Fig.5 shows a cross section through a first exemplary embodiment of a molded article after all of the material layers have been applied, Fig. 6 shows a schematic representation of the solidified material layers of the molded article consisting of the first and second material, the layers being shown transparent, Fig. 7 shows a three-dimensional view of a layer stack consisting of the material layers of the first and second material, Fig. 8 shows a three-dimensional view of the molded article after the material layers of the first material have been removed with the aid of a solvent, Fig. 9 shows a cross section through a second exemplary embodiment of a molded article after all of the material layers have been applied, Fig. 10 shows a cross section through the second exemplary embodiment of the molded article after the material layers of the first material have been removed, Fig. 11 shows a side view of a device similar to . Fig. 2 , but instead of the flexo printing device a rotary screen printing device is provided, Fig. 12 a side view of a device similar Fig. 2 , but instead of the flexographic printing device, a chambered doctor blade coating device is provided, Fig. 13 a cylindrical coating roller, Fig. 14 a frustoconical coating roller, Fig. 15 a side view of a device similar Fig. 2 , but instead of the flexo printing device an inkjet printing device for higher viscosities is provided, Fig. 16 a side view of a device similar Fig. 2 , but instead of the flexo printing device a hotmelt or a microdosing / coating device is provided, Fig. 17 an enlarged section of Fig. 16 , which shows a nozzle filling a cavity with the second material, Fig. 18 a schematic representation of a print head module for applying the second material, Fig. 19 a cavity that has been filled with the second material, Fig. 20 a micro-dosing unit with a nozzle that has a circular outlet opening, and Fig. 21 a micro-dosing unit with a nozzle that has a rectangular outlet opening.

[0036] In a method for producing a three-dimensional shape and a three-dimensional shaped object 1 by layered material deposition, geometric data for the shaped object 1 are provided by a control unit that communicates with a computer running software. Furthermore, a plate-shaped support part 2 is provided with a base surface 3 arranged in a horizontal plane for receiving the shaped object 1. As shown in Fig. 1 As can be seen, the base surface 3 essentially has the shape of a circular disk. However, other configurations are also conceivable, in which the base surface 4 can, in particular, have the shape of a full circular disk or be rectangular.

[0037] Furthermore, the method provides a solidifiable liquid first material 4, a different, solidifiable liquid second material 5, and water as a solvent for the solidified first material 4. The solidified second material 5 is not soluble in the solvent. The second material 5 is selected such that, in the solidified state, it has a higher strength than the solidified first material 4. Therefore, the second material 5 has a higher viscosity than the first material 4. In this embodiment, the first material 4 is a polymer containing a photoinitiator and crosslinkable by irradiation with ultraviolet radiation.

[0038] The liquid first material 4 is arranged in a first reservoir 6 and the liquid second material 5 in a second reservoir 7. The first reservoir 6 is connected via a line to a first dispensing device 8 for the first material 4. As shown in Fig. 2 As can be seen, the first reservoir 5 is designed as a substantially closed container and the second reservoir 7 as a trough.

[0039] The first dispensing device 8 comprises a first inkjet print head with a plurality of nozzles arranged in a row (not shown in detail in the drawing), which are directed to dispense portions of the first material 4 onto the base surface 3 or a solidified material layer of the first and / or second material 4, 5 located thereon. The row of nozzles is arranged parallel to the plane of the base surface 4 and extends transversely to the circumferential direction of the base surface 3, preferably substantially radially to its center.

[0040] The support part 2 and the first dispensing device 8 are rotatable relative to each other in and against the direction of arrow 10 and displaceable parallel to the rotation axis 11 by means of a first positioning device 9. Points located in the base surface 3 and spaced from the rotation axis 11 move along a helical or spiral trajectory.

[0041] The first dispensing device 8 and the first positioning device 9 are connected to a control device (not shown in detail in the drawing), which has a data memory for storing the geometric data of the molded article 1 to be produced. By means of the control device, the dispensing of the material portions of the first material 4 and the first positioning device 9 can be controlled depending on the geometric data such that negative mold layers 12 consisting of the flowable first material 4 can be applied to the base surface or a previously applied solidified material layer of the first and / or second material 4, 5 ( Fig. 3A ). The negative mold layers 12 each have at least one cavity 13, which contains a negative mold of a material layer of the molded article 1 to be produced. The cavities 13 each extend over the entire layer thickness of the respective negative mold layer 12 up to the base surface 3 or the solidified material layer located beneath the negative mold layer 12.

[0042] Arranged in the direction of arrow 10 behind the first dispensing device 8 is a first solidification device 14, by means of which the liquid first material 4 applied to the base surface 3 or a solidified material layer located thereon can be solidified. For this purpose, the first solidification device 14 has a first UV radiation source (not shown in detail in the drawing), by means of which ultraviolet radiation can be emitted onto the material layer of the first material to be solidified in such a way that a photocrosslinker contained in the first material is activated and the polymers contained in the first material 4 are crosslinked.

[0043] In the direction of arrow 10 behind the first solidification device 14, a second dispensing device 15 is arranged, by means of which the cavity(ies) 13 of the respective, previously solidified negative mold layer 12 are filled with the second material 5 in order to form a molded article layer 16 ( Fig. 3B ). In the Fig. 2 In the illustrated embodiment, the second dispensing device 15 is designed as a flexographic printing device.

[0044] This comprises a transfer body 17 designed as a flexographic printing roller and a coating device 18 in contact with the second reservoir 7, by means of which at least one surface region of the transfer body 17 can be coated with a layer 19 of the second material 5. With the aid of a second positioning device, the conical transfer body 17 can be rotated about an imaginary axis of rotation in such a way that the layer 19 of the second material 5 located on the outer surface of the transfer body 17 comes into contact with the bottom and the inner wall of the cavity(ies) 13 in such a way that the flowable second material 5 is filled into the cavity(ies) and then forms the molded article layer 16. This layer has the positive shape of a layer of the molded article 1 to be produced, the inverse of the negative shape of the layer 12.

[0045] Thereafter, the thus obtained molded article layer 16 is solidified by means of a second solidification device 21. As in Fig. 1 As can be seen, the second solidification device 21 is arranged behind the second dispensing device 14 in the direction of arrow 10. The second solidification device 21 contains a second UV radiation source, by means of which ultraviolet radiation can be emitted onto the molded article layer 15 in order to solidify the second material by crosslinking the polymers contained therein.

[0046] Thereafter, in a further process step, areas of the solidified negative mold layer 12 and / or the solidified molded article layer 16 and / or solidified second material 5 arranged on the negative mold layer are removed by means of a thickness milling cutter 22 ( Fig. 3C , 4 , 4A). In this case, areas of the solidified first and / or second material 4, 5 that protrude beyond a plane arranged parallel to the base surface at a predetermined distance therefrom are completely removed by machining and subsequently vacuumed away by means of a suction nozzle 23. If necessary, a surface cleaning device 20 can be arranged behind the suction nozzle 23.

[0047] Now, in a corresponding manner, another negative mold layer 12 ( Fig. 3D ) and a further shaped article layer 16 is applied ( Fig. 3E, 3F ) are applied. These steps are repeated until all the molded article layers 16 of the molded article to be produced have been produced ( Fig. 5 bis 8 ).

[0048] In a further process step, the negative mold layers 12 are brought into contact with the solvent in such a way that the solidified first material 4 dissolves completely in the solvent. This can be achieved, for example, by immersing the layer stack consisting of the negative mold layers 12 and the molded article layers 16 in the solvent for a predetermined period of time. The finished molded article ( Fig. 8 ) removed from the solvent and dried.

[0049] As in Fig. 9 und 10 As can be seen, the method according to the invention can also be used to produce shaped articles with overhangs 25 and cavities 26.

[0050] The second material 5 can also be filled into the cavity(ies) 13 using the screen printing process. As in Fig. 11 As can be seen, the transfer body 18 is designed as a rotary screen printing roller. This has a perforated, screen-like outer surface. The second reservoir 6 is arranged in the inner cavity of the rotary screen printing roller.

[0051] The dimensions of the perforation holes provided in the outer surface are adapted to the viscosity of the second material 5 such that the second material 5 can be pressed through the perforation holes by means of a squeegee 24 that rests linearly on the inner surface of the cylinder wall of the rotary screen printing roller. Outside the effective range of the squeegee 24, the second material 5 does not pass through the perforation holes. A cleaning device located behind the discharge point removes the material not removed from the rotary screen printing roller and feeds it into the cycle for reuse. Furthermore, the Fig. 11 device shown in the Fig. 2 , so that the description of Fig. 2 for Fig. 11 applies accordingly.

[0052] The second material 5 can also be filled into the cavity(ies) 13 using the chamber doctor blade method. As in Fig. 12 As can be seen, the transfer body 18 is designed as an anilox roller, on whose outer surface a chamber doctor blade 32 is arranged. The anilox roller has a correspondingly engraved outer surface prepared for material reception. Furthermore, the Fig. 12 device shown in the Fig. 2 , so that the description of Fig. 2 for Fig. 12 applies accordingly.

[0053] While in the Cartesian method the roller of the coating device 18 has a cylindrical shape ( Fig. 13 ) the roller in the polar process has a conical shape ( Fig. 14 ).

[0054] The second material 5 can also be filled into the cavity(ies) 13 using the inkjet printing process ( Fig. 15 ). For this purpose, the second dispensing device 15 has a second inkjet print head with a plurality of nozzles arranged in a row, which are directed to dispense material portions of the second material 5 onto the base surface 3 or a solidified material layer of the first and / or second material 4, 5 located thereon. The row of nozzles is arranged parallel to the plane of the base surface 4 and extends transversely to the circumferential direction of the base surface 3, preferably substantially radially to its center. Since the second material 5 has a higher viscosity than the first material 4, the nozzles of the second inkjet print head have a larger cross-section than those of the first inkjet print head. Instead of using a larger nozzle cross-section, or in addition to this, the nozzles of the second inkjet print head can also operate with a higher nozzle pressure than the first nozzles.The positioning of the carrier part 2 relative to the inkjet print head is carried out accordingly. Fig. 1 with the aid of a positioning device. The ejection of the second material 5 is controlled depending on the relative position between the inkjet print head and the carrier part 2 and depending on the geometric data provided for the molded article 1 to be produced.

[0055] In the Fig. 16 In the embodiment shown, the second material 5 is filled into the cavity(ies) 13 using a nozzle or hotmelt process. In the nozzle process, a highly viscous second material 5 is conveyed through a nozzle outlet at room temperature or in a state heated relative to room temperature by means of gas pressure. In the hotmelt process, the second material 5 is a thermoplastic that is solid at room temperature and can be liquefied by heating. During the printing process, the second material is heated to such an extent that it becomes liquid, and then it is conveyed by means of a metering pump, conveyor screw, or gas pressure through a nozzle 27 ( Fig. 17 ) onto the base surface 3 or a solidified material layer of the first and / or second material 4, 5 located thereon. The positioning of the carrier part 2 relative to the nozzle 27 is carried out according to Fig. 1 with the aid of a positioning device 9. The ejection of the second material 5 from the nozzle 27 is controlled as a function of the relative position between the nozzle 27 and the carrier part 2 and as a function of the geometric data provided for the molded article 1 to be produced. After the second material has been filled into the cavity(ies) 13, it is solidified by cooling.

[0056] Furthermore, it is possible to fill the second material 5 into the cavity(ies) 13 by a microdosing process. As in Fig. 18 As can be seen, the second reservoir 7 is connected to a gas pressure source 28, which can be an air pressure source, for example, in order to pressurize the second material 5. The reservoir 7 is connected to a nozzle 27 for dispensing material via lines 29, in each of which a valve 30 is arranged that can be adjusted to an open and a closed position. The outlet opening of the nozzle 27 is arranged with its outlet opening at a short distance from the base surface 3 and is then positioned along the base surface 3 relative to the carrier part 2. The individual valves 30 are each controlled in such a way as to depend on the geometric data provided for the molded article 1 to be produced and as a function of the relative position between the nozzle 27 and the carrier part 2 that the material flow of the second material 5 is released when the outlet opening of the nozzle 27 is positioned on the cavity 13.The material flow is blocked if the outlet opening of the nozzle 27 is not positioned on the cavity 13.

[0057] As in Fig. 18 As can be seen, several microdosing units 31 can be provided, each of whose valves 30 is connected with its inlet via a line 29 to the second reservoir 7. Each microdosing unit 31 has a nozzle 27 connected to the outlet of the respective valve 30. The nozzles 27 are arranged in a matrix in several rows and / or several columns. The valves 30 are controlled such that the cavity 13 is covered with the second material 5 ( Fig. 19 ). The nozzle 27 can be a round ( Fig. 20 ) or a square, preferably rectangular ( Fig. 21 ) outlet opening.

Claims

1. A process for preparing a three-dimensional molded article (1) by means of a layerwise application of material, wherein geometric data for said molded article (1), a support part (2) having a base surface (3) for receiving the three-dimensional molded article (1), a solidifiable liquid or free-flowing first material (4), a solidifiable liquid, free-flowing, pasty or powdery second material (5) and a solvent are provided, wherein said second material (5) in a solidified state has a higher strength than the solidified first material (4), wherein said solidified first material (4) is soluble in said solvent, a) wherein, for forming a negative form layer (12), material portions of said flowable first material (4) are applied to the base surface (3), and / or a solidified layer of material covering it, of said three-dimensional molded article (1) in accordance with the geometric data in such a manner that said negative form layer (12) has at least one cavity (13) at its surface facing away from said base surface (3), which cavity has a negative form of a layer of material to be prepared of said molded article (1), b) wherein said negative form layer (12) is solidified, c) wherein, for forming a layer of the molded article (16), said cavity (13) is filled with the second material (5) in such a manner that the negative form is transferred as a positive form to the layer of the molded article (16), d) wherein the second material (5) filled into the cavity (13) is solidified, e) wherein regions of the solidified negative form layer (12) and / or of the solidified molded article layer (16) that project over a plane provided at a predetermined distance to the base surface (3) are removed by material ablation by machining, f) wherein steps a) to e) are repeated at least once so as to perform step e) after the application of each individual layer of the first material (4), g) wherein said negative form layers (12) are contacted with the solvent in such a way that said solidified first material (4) dissolves in the solvent:

2. The process according to claim 1, characterized in that the material portions of the first material (4) are preferably applied to the base surface and / or the solidified negative form layer (12) covering it and / or a solidified molded article layer (16) by an ink-jet printing method or by electrophotography, and said first material (4) is a material that can be solidified by exposure to energy, and is exposed to such energy for solidifying the negative form layer (12).

3. The process according to claim 1 or 2, characterized in that the viscosity of the second material (5) in the non-solidified state is higher, optionally at least 10 times as high, especially at least 200 times as high, and preferably at least 2000 times as high, as the viscosity of the first material (4) in the non-solidified state, and / or that said flowable first and said flowable, pasty or powdery second material have a solids content, and that the solids content of the second material (5) in the non-solidified state of this material (5) is higher, optionally at least 10 times as high, especially at least 200 times as high, and preferably at least 2000 times as high, as the solids content of the first material (4) in its non-solidified state.

4. The process according to any of claims 1 to 3, characterized in that said first material (4) has a working viscosity suitable for jetting, which is lower than 1000 mPa·s, especially lower than 100 mPa·s, optionally lower than 30 mPa·s and preferably lower than 10 mPa·s, and is applied to said base surface and / or the solidified layer of material covering it, of said three-dimensional molded article (1) in the form of liquid droplets with a resolution of at least 360 dpi (254 dpi = 100 dpc), especially at least 720 dpi, and preferably at least 1440 dpi.

5. The process according to any of claims 1 to 4, characterized in that said second material (5) is applied to said negative form layer (12) as a function of the geometric data using a selective coating method in such a way that at least one material portion of said flowable, pasty or powdery second material is delivered into said at least one cavity (13), and preferably at least one site of the negative form layer that is outside the cavity is not contacted with said second material (4).

6. The process according to any of claims 1 to 5, characterized in that said second material (5) is a composite comprising a fluid and at least one additive, that said fluid has a viscosity at room temperature of at least 50 mPa·s and preferably at least 1000 mPa·s, and that said additive has solids particles provided in the fluid.

7. The process according to claim 5 or 6, characterized in that said second material (5) has a higher viscosity and / or a higher solids content as compared to the first material (1), that both the first and the second material (4, 5) are applied by an ink-jet printing method to the base surface (3) and / or a solidified negative form layer (12) and / or molded article layer (16) covering it, that in said ink-jet printing method, the first material (4) is ejected from at least one first nozzle, and the second material (5) is ejected from at least one second nozzle, and that the outlet opening of the second nozzle has a greater cross-sectional area and / or is exposed to a higher working pressure as compared to the outlet opening of the first nozzle, especially that the diameter of the outlet opening of the second nozzle is larger than that of the outlet opening of t he first nozzle.

8. The process according to any of claims 2 to 7, characterized in that the second material (5) is exposed to a gas pressure, and the thus pressurized second material (5) is passed through at least one valve (30) to at least one nozzle (27), that the outlet opening of the nozzle is provided along the base surface (3) relative to the support part (2), and the valve (30) is actuated as a function of the geometric data provided for the molded article (1) to be prepared, and as a function of the relative positions between the nozzle (27) and said support part (2) in such a manner that the material flow is released when the outlet opening is placed at the cavity (13), and that the material flow is blocked when the outlet opening is not placed at the cavity (13).

9. The process according to claim 7 or 8, characterized in that the outlet opening of a nozzle (27) is moved relative to the support part (2) along a continuous line running within the cavity (13), and said liquid, flowable or pasty second material (5) is delivered continuously along this line from the outlet opening into the cavity (13).

10. The process according to claim 5 or 6, characterized in that a support sheet is provided on which said second material (5) is arranged, that the second material (5) has a higher viscosity than the first material, and / or contains a higher solids content than the first material (5), that for filling the cavity (13) with the second material (5), the support sheet is placed at the cavity (13) in such a way that the second material (5) provided on the support sheet is facing the cavity (13), that an energy beam for which the support sheet is transparent is directed onto the support sheet in such a way that the second material is liquefied by heating on the side of the support sheet facing the cavity (13), and delivered into the cavity (13).

11. The process according to any of claims 1 to 6, characterized in that said second material (5) is filled into the cavity (13) by a flexographic printing, gravure printing, offset printing, screen printing, laser transfer, microdosing method, and / or by means of a doctor blade (24) or chamber blade.

12. The process according to any of claims 1 to 11, characterized in that the second material (5) is a thermoplast that is liquefied by heating, then filled into the cavity (13), and thereafter solidified by cooling.

13. The process according to any of claims 1 to 12, characterized in that the uppermost solidified negative form layer (12) and / or the uppermost solidified negative molded article layer (16) is cleaned from the chips formed during said machining material ablation.

14. The process according to any of claims 1 to 13, characterized in that said support part (2) having the base surface (3) is rotated around a rotation axis (11), and preferably displaced along the rotation axis (11), during the application of material and optionally during the solidification of the materials (4, 5).