Method for 3D printing a structure, 3D printer and sintering material system
Patent Information
- Application Number
- DE102023120757
- Authority / Receiving Office
- DE · DE
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-08-04
- Publication Date
- 2025-02-06
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
The present invention relates to a 3D printer and a method for printing a structure. The 3D printer applies a fusible material in the form of a strand to a printing bed by means of a print head. It is known that the printing bed can be partially heated in order to improve the result of the 3D printing.Fusible materials can be printed in virtually any desired form by means of the 3D printing process. Structures can be created without requiring an injection mold or the like for this purpose. In this case, different pressure parameters are of great importance in order to achieve stability of the structure.Special plastics are preferably used for 3D printing. This is done by a layer-by-layer or strand-by-strand construction of the object to be printed or of the structure to be printed.To increase the stability of the printed structure, it is known to chemically and / or thermally post-treat the structure. In particular, a so-called baking of the structure can be carried out in order to better connect the individual printed layers to one another.The use of the special plastics limits the application areas for 3D printed parts. Here, the choice of material for a material suitable for 3D printing determines the application cases for structures printed in this way. In particular, 3D printed parts may be subject to rapid wear during friction. To counteract this, the 3D printed parts can be post-processed in a time-consuming and cost-intensive manner.It is an object of the present invention to specify a method which makes it possible to produce low-wear and dimensionally stable structures by means of a 3D printing method.The present object is achieved by a method for printing a structure having the features of claim 1 and by a 3D printer having the features of claim 7.The method for 3D printing a pattern comprises the following steps:First, a sintering material system is provided which is suitable for 3D printing and comprises a sinterable component. Preferably, the 3D printing is carried out by means of material extrusion, so that the sinter material system is preferably suitable for 3D printing by means of material extrusion. Furthermore, a heatable printing bed is provided.By "heatable" is meant in particular that the pressurized bed is heatable to temperatures of up to >500 degrees Celsius.In a further step, the printing of a sintering material layer is carried out by applying the sintering material system to the printing bed at a specific printing temperature of the sintering material system. In particular, it is conceivable for the heatable pressure bed to be heated to a corresponding temperature.A sintered layer is then produced by heating the pressure bed to a sintering temperature. Preferably, a carrier material is removed from the sintering material system by heating, so that the sinterable component remains and is at least partially sintered at the specific sintering temperature.Subsequently, the temperature of the produced sintered layer is changed to a pressure temperature of a structural material system. In this case, the temperature of the produced sintered layer is preferably cooled and the sintered layer is particularly preferably heated to the pressure temperature of the structural material system.At least one further layer with the structure material system is then printed onto the sintering layer. It is understood that the structural material system can be the same material system as the sintered material system. It is also understood that a different material system can also be selected as a structural material system.Printing a further layer with the structure material system can achieve a conformality of the structure to be printed. The method can be used to create a structure by means of a 3D printing method, which has a sintered surface.When the pressure bed is heated to the sintering temperature, support material preferably evaporates starting from the pressure bed. As a result, a layer thickness of the sintered sintered layer can be determined by suitable selection of the temperature and heating rate. In particular, it is conceivable for the printed sintering material layer to be sintered only partially. It is understood that a plurality of layers above one another can also form the sintered material layer in order to create a thicker sintered sintered layer.The method can therefore provide a structure which has a sintered layer on at least one surface. Preferably, no post-treatment of the 3D printed structure has to be carried out for this purpose. A sintered surface structure can be provided cost-effectively and quickly.Preferred embodiments of the invention are described in the dependent claims. It is understood that the method and the sintering material system can be implemented according to the configurations defined for the device and the 3D printer.One skilled in the art will appreciate that this novel material processing approach is specific to all material extrusion 3D printing technologies and / or methods. The 3D printing by material extrusion comprises all 3D printing methods in which the processed material based on thermoplastic, i.e. in granulate form or in the form of filaments, is first melted and then applied to a surface, in particular the printing bed, by an extrusion process.In a preferred embodiment, the sintering material system comprises a carrier material, wherein the method comprises the step of: removing at least a part of the carrier material from the printed sintering material layer. The removal can be carried out thermally, for example, as already described above, such that the carrier material is vaporized or melted away. It goes without saying that the carrier material can also be removed chemically. In particular, it is also conceivable to remove a part of the carrier material in a targeted manner by laser irradiation. By removing at least a part of the carrier material, a layer thickness of the sinter layer can be adjusted precisely. The sintering process can thereby be carried out in a controlled manner.Particularly preferably, the pressure temperature of the sintering material system or of the structural material system comprises a melting temperature of the sintering material system or of the structural material system at which the molten sintering material system or structural material system can be applied to the pressure bed. The melting temperature is preferably in a range from 40 degrees Celsius to 300 degrees Celsius, preferably in a range from 50 degrees Celsius to 200 degrees Celsius and particularly preferably in a range from 60 degrees Celsius to 150 degrees Celsius. By means of a printing temperature which comprises a melting temperature of the corresponding material system, advantageous printing of the corresponding material system can take place. In particular, a firm connection between the printed layers or strands can be achieved. The pressure temperature preferably comprises exactly the melting temperature, so that after the application of a corresponding layer or a strand, a comparatively rapid curing takes place and the layer or the strand does not flow or only flows slightly.Advantageously, the sintering temperature comprises 0.3 times to 0.6 times the melting temperature of the sinterable component of the sintering material system. The sintering temperature is preferably greater than 300 degrees Celsius, preferably greater than 350 degrees Celsius and particularly preferably greater than 400 degrees Celsius. By selecting the sintering temperature in the corresponding region, it can be reliably ensured that a sintering process takes place. In particular, an advantageous temperature can be selected depending on the material in order to achieve an optimum sintering result.The method particularly preferably comprises the step "creating an oxide layer on the sintering material layer" and particularly preferably "providing an oxygen-rich atmosphere for the sintering", wherein the sintering material layer is preferably at least partially oxidized. By forming an oxide layer, abrasion resistance of the printed structure can be improved. By "oxygen-rich atmosphere" it can be understood in particular that the sintering takes place under normal atmosphere and the oxygen content is sufficient to at least partially oxidize the sintering layer. It goes without saying that an increased oxygen content can also be established in order to promote oxidation. As a result of the heating of the pressure bed, support material is preferably initially melted away, so that the sinterable component comes into contact with the prevailing atmosphere. As a result of the further heating, an oxidation process can then take place, particularly preferably parallel to the sintering process. As a result, a thickness of the sintered layer and a thickness of the oxidation layer can be determined. For oxidation, the sinterable component must preferably be exposed, i.e. come into contact with the atmosphere, and a corresponding temperature must prevail at the sinterable component. It is understood that a temperature preferably used for oxide formation can be set up by means of the pressure bed.In a further advantageous embodiment, the method comprises the step "creating a nitrite layer on the sintering material layer", preferably "providing a nitrogen-rich atmosphere for the sintering", wherein the sintering material layer is preferably at least partially nitrided. The nitrite layer can be produced in a manner analogous to the oxide layer and offers comparable advantages. It is understood that instead of an oxygen-rich atmosphere, a nitrogen-rich atmosphere is preferably provided.Advantageously, the printing bed is designed at least in sections in the form of a flat two-dimensional plate. Additionally or alternatively, the printing bed is designed to be rotationally symmetrical at least in sections. Additionally or alternatively, the pressure bed can be conical and / or cylindrical. In addition, the printing bed can have a structured surface at least in sections. This can provide a 3D printer capable of printing a variety of structures. Depending on the application, an optimum structure with a sintered surface can be printed.Particularly preferably, the 3D printer has an atmosphere chamber and a flooding unit which are designed to generate an oxygen-rich and / or nitrogen-rich atmosphere. By providing the chambers with respective units, a special 3D printer can be provided which is designed for rapidly creating respective structures.The sintering material system suitable for 3D printing preferably comprises a thermoplastic polymer and a sinterable component.The thermoplastic polymer can be present, for example, as granules and is mixed with the sinterable component. An optimum mixing ratio can thereby be achieved. In particular, it is conceivable to first mix a thermoplastic polymer in granulate form with the sinterable component and then only replenish the thermoplastic polymer in order to supply a sinter material system on the one hand and then a structural material system to the 3D printer without complicated changeover.Alternatively, the sintering material system may comprise a thermoplastic polymer matrix in which a sinterable component is dispersed. As a result, a corresponding sintering material system can be provided in a preprocessed manner. Handling is simplified in this case, since only a single component has to be supplied. Furthermore, it can be ensured that the mixing ratio is exactly maintained. Alternatively, the sintering material system can comprise exclusively a sinterable material.Particularly preferably, the sinterable component or the sinterable material comprises a metal, a ceramic material and / or a polymer.The material system under consideration is either a pure thermoplastic polymer having a single component and / or phase. Alternatively, it can be a thermoplastic polymer matrix phase in which an additional component, for example metal, a ceramic material or a polymer, is introduced. Alternatively, the material system can also comprise a multicomponent material which is mixed or in which at least one component is present distributed in a matrix.These material systems are manufactured or formed by powder metallurgical methods and may contain pure elements, in particular pure chemical elements as occur in the periodic table of the elements, which have a crystal structure and an atomic structure.Further, these elements may form an oxide or nitrite material upon a chemical or physical reaction with oxygen or nitrogen at a particular temperature and / or pressure.Furthermore, the material systems under consideration can be alloys or immiscible materials which coexist physically or chemically in a defined or undefined volume.The printing bed may be heated to a temperature that improves the adhesion of the printed materials to the printing bed, particularly to the printing temperature.With regard to the processing temperatures, the method may have two different phases. In the first 3D printing phase, a temperature may prevail at which a granulate or filament material can be melted, extruded and applied.In the second phase, the so-called sintering phase, a temperature may prevail at which the material can be sintered, so that a new material composition with defined boundary surfaces is produced.The sintering process is preferably carried out until the desired aim is achieved. In this case, an oxide or nitrite layer can be created in particular. During the sintering process, the thermal stress due to the pressure bed initiates a chemico-physical process at the interface between the pressure bed and the composite material.By heating to high temperatures, for example temperatures above 400 degrees Celsius, the polymeric part of the material, i.e. the carrier material, escapes from the material, in particular by pyrolysis-i.e. by thermal degradation into smaller, volatile molecules-and leaves behind the sinterable component. The sinterable component can in particular comprise the metallic or ceramic part of the material system and has a certain porosity in this state.The remaining material begins to adapt to the mass change by physically adapting itself through evaporation and fusion processes. At this stage, the material begins to compact. Volume reduction and microstructural changes occur.In the presence of oxygen or nitrogen, the process results in the formation of new crystal structures of oxides or nitrides. The resulting material is generally hard, brittle and also heat- and corrosion-resistant.In a further printing phase, the sintered material, which preferably serves as a printing bed for further layers, is cooled to room temperature and then heated to a printing temperature of the structural material system, so that the further printed material layers adhere.The structural material system may comprise a pure polymer, a polymer-based composite material, or the like. The so-called G code for the printed structure is determined from data describing the surface of the sintered surface layer.After this pressure phase, the material is cooled and finally the complete structure is removed from the pressure bed. The structure so produced has a sintered surface that is hard, brittle, and not dimensionally stable, and a later printed surface that is soft, possibly geometrically complex, and dimensionally stable.The entire process for the starting composite material system PLA / aluminum, i.e. in particular aluminum powder particles in a polylactide matrix, PLA matrix, is illustrated below.This PLA / Al composite material is printed in 3D onto the printing bed until a certain layer thickness is reached. The print bed, which can be heated to a much higher temperature, the sintering temperature, is then heated, thereby causing heat transfer from the print bed to the printed PLA / AI composite.During the sintering process, the PLA at the interface between the pressurized bed and the composite material is thermally removed from the composite material, so that pure aluminum remains, which reacts with atmospheric oxygen or oxygen in an oxygen-laden pressure chamber and forms aluminum oxide Al2O3.The material surfaces exposed to oxygen at the sintering temperature begin to convert to alumina. Once the desired thickness of the aluminum oxide is reached, the sintering process is stopped and the sintered structure cools to room temperature.A second 3D printing step is then initiated, in which first the surface of a new material to be printed / deposited is heated to improve adhesion, and then the new material is printed at a material supplier recommended temperature, the printing temperature.For a stoichiometric reaction of aluminum to aluminum oxide--Al(s)+O2(g)→Al2O3(s)--3 mol of oxygen must preferably react with 2 mol of aluminum at atmospheric pressure, i.e. 1 atm, 760 mmHg or 1 bar, in order to form about 102 g of aluminum oxide.For a stoichiometric reaction of aluminum to aluminum nitride - 2Al(s)+N2(g)→2AlN(s)-2 moles of aluminum must react with 2 moles of nitrogen at atmospheric pressure to form 2 moles of aluminum nitride having a mass of about 164 g.The invention will be described and explained in more detail below with reference to some selected exemplary embodiments in conjunction with the accompanying drawings. The following are shown: FIGS. 1a-1h schematically show the steps of a method according to the invention; FIGS. 2a-2d schematically show individual stages of a sintering process; FIG. 3 dis a schematic illustration of a 3D printer with a heatable printing bed; FIG. 4 is a schematic illustration of a 3D printer having a chamber; and FIG. 5 shows a schematic overview of various method steps.FIG. 1 aschematically illustrates the first step of the method according to the invention. A sintering material system 10 is provided here. The sintering material system 10 is located in a storage container 12 and can be supplied to a schematically illustrated print head 14.In the example shown, the storage container 12 comprises a spindle on which the sinter material system 10 is accommodated in the form of a filament.In FIG. 1 b, a heatable pressure bed 16 is provided in a next step.FIG. 1 cshows the step of printing a sintering material layer 20 by applying the sintering material system 10 to the heatable printing bed 16. It is understood that this step is preferably carried out at a pressure temperature of the sintering material system 10. For reasons of clarity, a representation of the heating of the printing bed 16 to the printing temperature has been dispensed with.In FIG. 1 d, a sintering layer is produced by heating the pressure bed 16 to a sintering temperature. In the figure, this is illustrated by wavy lines. When producing the sinter layer, the pressure bed 16 is heated to the sintering temperature. As a result, the sintering process takes place in a sinterable component of the sintering material system 10.FIG. 1e shows a sintered sintered layer 21. The sintered sintered layer 21 is formed from the sintered material layer 20 by applying the sintering temperature to the sintered material layer 20.In FIG. 1f, a change of the temperature of the produced sintered layer 21 to a pressure temperature of a structural material system 10' is schematically shown. The pressure temperature of the structural material system 10' is preferably lower than the sintering temperature. This is illustrated in the figure by the smaller number of wavy lines than in FIG. 1 d. It is understood that the structural material system 10' can also be the sintering material system 10. In the embodiment shown in FIG. 1 f, the structural material system 10' is a material system different from the sintering material system 10.FIG. 1g schematically illustrates the printing of a further layer 20' with the structural material system 10' onto the sintering layer 21. For reasons of clarity, the illustration of the wavy lines for illustrating a temperature in FIGS. 1 cand 1 gis omitted.FIG. 1h schematically illustrates a first step of an alternative method according to the invention. In this case, a sintering material system 10 in the form of a powder, powder mixture, granulate and / or granulate mixture is provided. The sintering material system 10 is located in a storage container 12, which is in the form of a pot or crucible, and is fed to an extruder print head, in which it is melted and subsequently applied to the printing bed.FIG. 2 aschematically illustrates a printed sinter material layer 20 arranged on a heatable printing bed 16.FIGS. 2a to 2d show in detail the individual processes during the sintering of the sintering material layer 20.FIG. 2 b shows a situation in which the heatable pressure bed 16 is heated to the sintering temperature by means of the heating spiral 18. The temperature is illustrated by the wavy lines.During the heating of the sintering material layer 20, a carrier material is removed from the sintering material layer 20. The carrier material vaporizes, for example, due to the high temperature. It is understood that decomposition of the carrier material is also conceivable, in the manner of pyrolysis.The sinterable component then remains in a porous structure. During sintering, these pores are partially closed and a solid sintering layer 21 is formed. This is illustrated in FIG. 2c. The sintered layer 21 may suffer shrinkage during sintering. The sintering layer 21 is therefore not true to shape to the sintering material layer 20.In Fig. 2d an alternative preferred embodiment is shown. In this, the sintering process takes place in a special atmosphere 22. The specific atmosphere may be, for example, oxygen-rich or nitrogen-rich.If the atmosphere 22 is oxygen-rich or nitrogen-rich, an oxide layer 24 is formed on the sinter layer growing from the heatable pressurized bed 16 in the case of an oxygen-rich atmosphere or a nitrite layer 24 in the case of a nitrogen-rich atmosphere.Referring now to Fig. 3, a 3D printer 26 is shown schematically. The 3D printer 26 has a material supply 28 of the material system. The material system is guided to a print head 14 of the 3D printer 26, so that a material layer, in particular a sinter material layer 20, can be applied to the heatable printing bed 16 by means of the print head 14.For this purpose, the 3D printer 26 has a supporting and guiding structure 30, on which the print head 14 can be guided movably. In the example shown, the print head 14 is moved to the left for strand deposition. Since this is the first strand deposit, a sintering material layer 20 is applied in the situation shown.It is understood that after sintering, the structural material system can be applied in the same manner as already described above.Referring now to Figure 4, there is shown a preferred embodiment of a 3D printer 26. In contrast to the embodiment shown in FIG. 3, the 3D printer 26 of FIG. 4 comprises a chamber 32 and a corresponding flooding unit 34. It is understood that only the print head 14 and the print bed 16 may be accommodated.The flooding unit 34 is configured to establish an oxygen-rich atmosphere during the sintering of the sintering material layer 20. It is understood that the oxygen-rich atmosphere may already prevail at the beginning of the printing process. It is further understood that the oxygen-rich atmosphere is preferably provided before the sintering step of the sintering material layer 20.A nitrogen-rich atmosphere can also be produced in an analogous manner.It is understood that FIG. 4 is greatly simplified and serves to better understand the invention. A person skilled in the art recognizes that a corresponding oxygen reservoir is required for establishing an oxygen-rich atmosphere. The same applies analogously to the provision of a nitrogen-rich atmosphere. A person skilled in the art knows the means necessary for this, so that further details in this respect are omitted.FIG. 5 schematically shows the steps of a method according to the invention in an overview.In a first step S 10, a sintering material system is provided which is suitable for 3D printing and comprises a sinterable component.Subsequently, in a second step S 20, a heatable printing bed is provided.In a third step S 30, the printing of a sintering material layer is carried out by applying the sintering material system to the printing bed at a specific printing temperature of the sintering material system.In a fourth step S 40, a sintering layer is subsequently produced from the sintering material layer by heating the pressure bed to a sintering temperature.In a fifth step S 50, the temperature of the produced sintered layer is changed to a pressure temperature of a structural material system.Finally, in a sixth step S 60, a further layer is printed with the structural material system onto the sinter layer.In an alternative seventh step S 70, at least a part of a carrier material can be removed from the printed sintering material layer if the sintering material system comprises a carrier material.The seventh step S 70 may be performed before the fourth step S 40. Advantageously, the seventh step S 70 is carried out parallel to the fourth step S 40 during heating of the pressurized bed to a sintering temperature. The separate illustration is provided for improved clarity and understanding.In a further alternative eighth step S 80, an oxygen-rich atmosphere or a nitrogen-rich atmosphere can preferably be generated. This step is preferably carried out before the fourth step S 40, the heating to a sintering temperature. This step does not have to be carried out directly before the fourth step S 40; it is sufficient if the corresponding atmosphere predominates during the sintering. Consequently, the atmosphere can be provided already before the beginning of the printing process.The invention has been fully described and explained with reference to the drawings and the specification. The description and explanation are to be taken by way of example and not limitation. The invention is not limited to the disclosed embodiments. Other embodiments or variations will become apparent to those skilled in the art upon use of the present invention, as well as upon a detailed analysis of the drawings, disclosure and appended claims.In the claims, the words "comprise" and "with" do not exclude the presence of further elements or steps. The undefined article "a" or "an" does not exclude the presence of a plurality. A single element or unit may perform the functions of several of the units recited in the claims. An element, a unit, an interface, a device and a system can be partially or completely implemented in hardware and / or in software. The mere naming of some measures in several different dependent claims is not to be understood as meaning that a combination of these measures cannot likewise be used advantageously. A computer program can be stored / distributed on a non-volatile data carrier, for example on an optical memory or on a solid state drive (SSD). A computer program can be distributed together with hardware and / or as part of hardware, for example by means of the Internet or by means of wired or wireless communication systems. Reference signs in the patent claims should be understood to be non-limiting.Reference numerals denote reference numerals10 Sintering material system 10' Structural material system 12 Storage container 14 Print head 16 Print bed 18 Heating spiral 20 Sintering material layer 20' Further layer 21 Sintering layer 22 Atmosphere 24 Oxide layer / nitrite layer 26 3D printer 28 Material store 30 Guide structure 32 Chamber 34 Flooding unit S 10 to S 80 Method steps
Claims
Method for 3D printing a structure, comprising the steps of: - providing (S10) a sintering material system (10) which is suitable for 3D printing and comprises a sinterable component; - providing (S20) a heatable printing bed (16); - printing (S30) a sintering material layer (20) by applying the sintering material system (10) to the printing bed (16) at a specific printing temperature of the sintering material system (10); - producing (40) a sintering layer (21) by heating the printing bed (16) to a sintering temperature; - changing (50) the temperature of the produced sintering layer (21) to a printing temperature of a structure material system (10, 10'); printing (S60) a further layer with the structural material system (10, 10') on the sintered layer (21).Method according to claim 1, wherein the sintering material system (10) comprises a carrier material, comprising the step of: - removing (S70) at least a part of the carrier material from the printed sintering material layer (20).Method according to one of the preceding claims, wherein the pressure temperature of the sintering material system (10) or of the structural material system (10, 10') - comprises a melting temperature of the sintering material system (10) or of the structural material system (10, 10') at which the molten sintering material system (10) or structural material system (10, 10') can be applied to the pressure bed (16); and - is preferably in a range from 40°C to 300°C, preferably 50°C to 200°C and particularly preferably 60°C to 150°C.Method according to any one of the preceding claims, wherein the sintering temperature comprises 0.3 times to 0.6 times a melting temperature of the sinterable component of the sintering material system (10); and - preferably greater than 300°C, preferably greater than 350°C and particularly preferably greater than 400°C.Method according to one of the preceding claims, comprising the step of: - creating an oxide layer (24) on the sintering material layer (20) and preferably providing (S80) an oxygen-rich atmosphere (22) for the sintering, wherein the sintering material layer (20) is preferably at least partially oxidized.Method according to one of the preceding claims, having the step of: - creating a nitrite layer (24) on the sintering material layer (20) and preferably providing (S80) a nitrogen-rich atmosphere (22) for the sintering, wherein the sintering material layer (20) is preferably at least partially nitrided.3D printer (26) for printing a structure by means of a fusible sinter material system (10) which is suitable for 3D printing and comprises a sinterable component, wherein the sinter material system (10) can be output from a print head (14) and the 3D printer (26) has a heatable print bed (16).3D printer (26) according to the preceding claim, wherein the printing bed (16) is formed at least in sections - in the form of a flat two-dimensional plate; - is formed rotationally symmetrically, - is formed conically; - is formed cylindrically; and / or - has a structured surface.3D printer (26) according to one of claims 7 or 8, comprising - an atmosphere chamber (32) and a flooding unit (34) which are designed to generate an oxygen-rich or nitrogen-rich atmosphere (22).A sintering material system (10) suitable for 3D printing, comprising: - a thermoplastic polymer and a sinterable component; - a thermoplastic polymer matrix in which a sinterable component is dispersed; or - exclusively a sinterable material.The sintering material system (10) according to the preceding claim, wherein the sinterable component or the sinterable material comprises a metal, a ceramic material and / or a polymer.