Method for manufacturing a molded piece, in particular dental

Abstract

This invention relates to a method for manufacturing a molded part (210) using a cold-casting mold (100) having a cavity (110) with geometrical aspects corresponding to a molded part, particularly a dental molded part (210), and at least one opening (111, 112) leading into the cavity (110), said molded part being, in particular, a dental molded part (210) made of a sinterable mixture (200), wherein the cold-casting mold (100) is additively manufactured from raw material (150) using a 3D printer by means of additive manufacturing, particularly 3D printing, and wherein the cavity (110) is created according to digital data recording, particularly based on a patient's oral cavity space model. The object of this invention is to enable the manufacture of molded parts (210), particularly dental molded parts, at a lower cost and more accessible to the general public compared to existing technologies. The objective is to fill the cavity (110) of a cold casting mold (100) with a sinterable mixture (200) via at least one opening (111, 112); to harden and / or solidify the sinterable mixture (200) in the cavity (110) of the cold casting mold (100), wherein the cold casting mold (100) is thermally decomposed and / or thermochemically decomposed in a gas and / or liquid containing and / or including the mixture (200) via at least one opening (111, 112); and to sinter the sinterable mixture (200) to a final hardness in a temperature range of 200°C to 2500°C, until a molded part (210), particularly a dental molded part (210), such as a denture, is obtained in a temperature range of 900°C to 2500°C.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a molded part, particularly a dental molded part, by means of a cold casting mold having a cavity with a geometric aspect corresponding to the molded part, particularly a dental molded part, and at least one opening leading into the cavity, wherein the molded part is, in particular, a dental molded part made of a sinterable mixture, wherein the cold casting mold is additively manufactured from the raw material by means of additive manufacturing, particularly 3D printing, using a 3D printer, and wherein the cavity is created according to digital data recording, particularly based on a patient's oral cavity spatial model. Background Technology

[0002] The use of computer-aided design (CAD / CAM) to manufacture molded parts is known in many technical fields. Dental molded parts, particularly dentures such as crowns and bridges, as well as dental implants and restorations or orthodontic-related parts such as brackets, have also been manufactured using CAD / CAM in many dental clinics and laboratories. Here, a digital spatial model of the patient's mouth is first created. For example, the desired denture is planned using software, and the created data is sent to a milling machine, which mills the finished denture from the blank. The blank is typically manufactured using cold casting, where a mixture is first made from ceramic or metal powders suitable for dental technology. For example, pastes, slurries, suspensions, or even "dry" loose powders can be used as the mixture. A method for manufacturing dentures from dental metal powders is known from EP 2 470 113 B1. Here, CrCo dental metal powder is mixed into a slurry, cold-filled into a mold, and dried therein. The binder added to the slurry provides sufficient shape stability after drying, allowing the dried slurry to be removed as a green blank from the cold casting mold and milled into the desired spatial shape using a milling machine according to transmitted digital data. Through final (dense) sintering, the denture achieves the required hardness and density. The material properties required for dental molded parts are clearly defined according to national and / or international standards. This cold casting method is only applicable to the manufacture of blanks. The fine, complex shape of the actual denture is then milled from the blank by machining. Teachings on metal or ceramic slurries used in dental technology are prior art and can be found, for example, in documents EP1658018 B1, EP1047355 B1, WO 2013007684 A, EP1558170 B1, and EP1885278 B1. Information on their regulation can be found in documents DE 102005023727 B4 and DE19801534A1. The implementation of final sealing or final sintering is also well described in the prior art; the corresponding methods and sintering furnaces can be found in EP2765950 B1, EP2844412A1, and WO2011020688 A1.

[0003] When using loose powder as a mixture, an additional step is usually required: isostatic pressing to achieve sufficient shape stability. Here, the mixture is uniformly loaded with high pressure from all sides. Corresponding methods for manufacturing ceramic dentures from ceramic powders such as zirconia are also well known from the prior art. A method for manufacturing dental components from ceramic powders is described in WO 2008 / 114 142 A1.

[0004] The digital spatial model of the oral cavity is also used to manufacture temporary parts from plastic. Here, the data record created for the denture is forwarded to a 3D printer, which manufactures temporary parts from plastic raw materials using additive manufacturing (3D printing) master layers.

[0005] In addition to plastics, inorganic materials can also be used as raw materials in additive manufacturing. Additive manufacturing methods such as SLM (Selective Laser Melting), and extrusion methods such as FDM (Fused Deposition Modeling) and FFF (Fused Filament Fabrication) are known. Additive manufacturing methods that utilize the photocuring properties of raw materials, such as SLA or STL (Stereolithography), DLP (Digital Light Processing), and LCM (Lithography-based Ceramic Fabrication), are also known.

[0006] Therefore, preliminary attempts have been made to manufacture dentures from metal or ceramic using additive manufacturing. The manufacture of dental crowns from zirconia using additive manufacturing is known from WO2018 / 065856A1. However, 3D printers for metal or ceramic articles are very expensive and / or the printed molded parts do not meet the high material requirements for dental use. In particular, additive manufacturing requires a very high binder share (approximately 30%) in the raw materials, thus making it impossible or extremely costly to achieve the desired final density or final hardness. An economically feasible implementation of printing dental molded parts from ceramic or metal remains a long way off.

[0007] WO 2019 / 210285 A2 discloses another possibility in which digital spatial data of the oral cavity will be used to manufacture complex and densely sintered denture components using a 3D printer. For this, a self-destructing mold should be printed using a 3D printer, rather than a denture. A two-component powder mixture, a sinterable alumina powder and a powdered binder with a high coefficient of thermal expansion (WAK), is used as the raw material for the printing process. The printed mold is filled with sinterable dry zirconia loose powder as a mixture. The mold is then locked with a cap printed from the same material to isostatically press the (two-part) mold together with the zirconia loose powder contained therein under a pressure of 400 MPa. Crucially, the loose powder does not contain binder to allow for uniform pressing. The loose powder is compacted together with the mold and then sintered without removing the mold. During sintering, the binder contained in the mold expands, causing the mold to burst. To separate the sintered molded part from the mold, the sintering temperature of the mold must be higher than that of the loose powder. The disadvantages of the disclosed method are, on the one hand, the high cost associated with 3D printing of the ceramic raw material and isostatic pressing at extremely high pressures of 400 MPa. However, the use of ceramic raw materials with sintering temperatures higher than the loose powder is crucial for the described method, and on the other hand, it also limits the possible applications of the method. The mixture used must be binder-free to achieve uniform pressing. Furthermore, the pressure should be applied evenly to the molded part using a compaction pressing method, especially since isostatic pressing is not suitable for mixtures with a moisture content exceeding 7%. Liquids are almost incompressible. For isostatic pressing, the loose powder needs to be completely surrounded within a mold that is sealed with a lid. For this reason, any moisture contained in the mixture cannot escape. Summary of the Invention

[0008] Therefore, the object of this invention is to provide a cold casting mold for additive manufacturing, particularly 3D printing, which enables the mass production of dental molds with complex anatomical shapes, such as crowns, bridges, dental implants, abutments, prostheses, etc., at a lower cost than existing technologies. Simultaneously, its applicability should be expanded. In particular, it can be used in various mixtures of sinterable, metallic, and / or ceramic materials, either in dry powder form or as a slurry, suspension, or paste.

[0009] The objective is achieved by the method for manufacturing dental molds according to claim 1.

[0010] The method for manufacturing molded parts, especially dental molded parts of the type described in detail at the beginning, is characterized by having the following method steps:

[0011] - The cavity of the cold casting mold is filled with a sinterable mixture through at least one opening;

[0012] - Hardening and / or solidifying a sinterable mixture in the cavity of a cold casting mold, wherein the gas and / or liquid contained in and / or included in the sinterable mixture are discharged from the cavity via at least one opening;

[0013] - When the temperature is in the range of 200°C to 2500°C, the cold casting mold will undergo thermal decomposition and / or thermochemical decomposition.

[0014] - When the temperature is in the range of 900°C to 2500°C, the sinterable mixture is sintered to the final hardness until the molded part is obtained, especially the dental molded part, such as dentures.

[0015] Therefore, according to the present invention, for manufacturing molded parts, especially dental molded parts, additive manufacturing, particularly 3D printing, and preferably one-piece cold casting molds are proposed. These cold casting molds are preferably capable of undergoing pyrolysis or combustion thermal decomposition or thermochemical decomposition or dissolution during the working step of sintering the mixture into the final molded part, especially the dental molded part. In this way, damage to the dental molded part, which typically has a thin filamentary structure, due to cracking or bursting of the cold casting mold or other forces acting thereon, can be avoided. After sintering is completed, the cold casting mold has undergone complete or almost complete thermal or thermochemical decomposition, thus avoiding the additional working step of separating the cold casting mold and the molded part from each other.

[0016] According to the method of the invention, the cavity of the cold casting mold is preferably filled with a sinterable mixture after its manufacture, optionally under pressure and hardened or solidified within the cold casting mold. Particularly during filling and / or during hardening or solidification, but also throughout the process, gases and / or liquids contained in and / or included in the mixture can be drained or escaped from the cavity through at least one opening. Suitably, at least one opening remains open or unclosed throughout the entire process of the method.

[0017] The thermal and / or thermochemical decomposition of the cold casting mold can begin during the hardening or solidification of the mixture, or optionally only after the mixture has fully hardened, especially to the green hardness. Preferably, the decomposition begins in the temperature range of 200°C to 650°C and is completed in the final sintering at a temperature range of 900°C to 2500°C.

[0018] The hardening or curing of the mixture in the cavity can occur in various ways, particularly through chemical reactions. Chemical reactions can be achieved, in particular, by means of adhesives or two-component adhesives. Depending on the adhesive chosen, the reaction can be initiated by various triggers, such as irradiation with a light source, especially an ultraviolet source, by heat, by the removal of moisture, etc.

[0019] According to an advantageous variation of the method, the mixture exists as a slurry and / or paste and includes a diluent, especially water, wherein the mixture is dried, hardened and / or solidified in the cavity of the cold casting mold and the liquid portion and / or moisture of the mixture are extracted from the cold casting mold, especially from the mixture, by means of at least one opening.

[0020] Especially when using slurry or water-containing / paste-like material as the mixture, however, for additive manufacturing of loose powder, a cold casting mold according to an advantageous design of the method is also used, the cold casting mold having at least one first opening leading into and / or leading out of the cavity and having at least one second opening leading into and / or leading out of the cavity, wherein the cavity of the cold casting mold is filled through the first opening and contains and / or includes gas, especially air inclusions, and / or liquid, especially diluent, contained in a sinterable mixture, which is then discharged from the cavity through the second opening.

[0021] Therefore, in addition to at least one first opening, at least one second opening can be constructed, wherein the first opening is designed to fill the cavity with the mixture, and the second opening is designed to drain the fluid contained in the mixture. In principle, it is conceivable that the first and / or second openings are configured for drilling, particularly after the additive manufacturing of the cold casting mold is completed. However, it is advantageous that the first and / or second openings are constructed directly during additive manufacturing, thereby avoiding additional working steps. By constructing at least one second opening, the cold casting mold additively manufactured according to the method of the invention can be used not only for mixtures with arbitrary moisture content, but the at least one second opening also allows for venting when using loose powders, which can be assisted, for example, by vibration. In an improved form of this design, at least one wall portion of the cold casting mold that limits the cavity is additively manufactured to have, wholly or partially, a plurality of second openings leading into and / or leading out of the cavity and penetrating the wall portion, the second openings being used to drain gases, especially air inclusions, and / or liquids, especially diluents.

[0022] By constructing multiple adjacent second openings through one or more walls of a cold-casting mold, a sieve-like surface can be formed, allowing liquids and gases to pass through while blocking solids. Preferably, the diameter of the respective second opening is smaller than the particle size of the powder contained in the mixture, such as metal powder, ceramic or glass-ceramic powder, and / or the size of the resulting particle agglomerates. The multiple second openings can also be configured as pores and / or capillaries penetrating the wall, giving the wall fully or partially porous and / or hygroscopic properties.

[0023] This design offers the advantage that moisture contained in the mixture is contained or absorbed by adjacent, porous, and / or hygroscopic walls, and preferably discharged from the interior towards the atmosphere surrounding the cold casting mold. This effect can be aided by increasing the ambient temperature surrounding the cold casting mold or by other measures to reduce ambient air humidity, thereby creating dry ambient air.

[0024] Therefore, a variation of the method is proposed to harden and / or solidify the mixture in the cavity of the cold casting mold by means of heat, wherein the cold casting mold filled with the mixture is placed in a drying cabinet or sintering furnace and set at a temperature ranging from 30°C to 120°C. The ambient air humidity can also be set to a desired value if needed. It has been found that an air humidity range of 1% to a maximum of 50% is beneficial for gentle, uniform, and simultaneously rapid drying.

[0025] The hardening of the mixture can be accelerated by the action of heat and, when necessary, by reducing air humidity, such as in the case of a drying process. In particular, the atmosphere or ambient air present in the environment, i.e., in a drying cabinet or air-conditioned cabinet, or in a sintering furnace, is dried, thereby allowing the moisture and / or liquid contained in the mixture to be more quickly expelled from the cavity into the environment. In the design of the walls of cold-casting molds with porous and / or absorbent surfaces, where these surfaces are pierced by multiple holes and / or second openings in the form of capillaries, this effect can have a significant impact on drying time.

[0026] During hardening and / or curing of the mixture, and during sintering, volumetric shrinkage or sintering shrinkage of the molded part typically occurs, which depends on the compaction of the mixture. Preferably, digital data recording of the geometry of the cavity for cold casting molds, based on a spatial model of the patient's cavity, includes volumetric shrinkage of the mixture depending on sintering and / or hardening.

[0027] Depending on the mixture used, the corresponding volumetric shrinkage during hardening and / or sintering of the mixture must be considered, and the cavity of the cold casting mold is configured to have a correspondingly matching (larger) initial geometry. For example, sintering shrinkage in the range of 25% to 50% is considered for mixtures containing ceramic powder, 50% to 95% for mixtures containing sol and nano-zirconia particles, and 8% to 25% for mixtures containing metal powder, respectively, based on the initial geometry. For the hardening of the mixture by light and / or drying, approximately 2% to 20% volumetric shrinkage is considered based on the initial geometry. For the cold casting mold itself, in the manufacture of molded parts, especially dental molded parts, a volumetric shrinkage in the range of 1% to 10% is also considered based on the initial geometry. Cold casting molds manufactured according to the method of the invention enable the low-cost manufacture of molded parts, especially dental molded parts, from a wide variety of mixtures.

[0028] To ensure a constant supply of sufficient mix for manufacturing molded parts, especially dental molded parts, particularly in the event of volume shrinkage, an improved design connects at least one compensation volume, if necessary, to the cavity of the cold casting mold via a filling channel in a fluid-conducting manner to store the mix. Preferably, the compensation volume is also additively manufactured in one piece with the cold casting mold. Especially when using mixes with high moisture content and / or in the presence of air inclusions, the compensation volume acts as a reservoir and allows for backflow or dripping of the mix to compensate for volume loss caused by the escape of gas and / or liquid from the cavity via at least one second opening.

[0029] Advantageous for the method is the use of organic materials, particularly organic polymers, waxes, or plastics, as raw materials for additive manufacturing of cold casting molds. These materials preferably have a melting point or decomposition temperature in the range of 40°C to 300°C, making the cold casting mold plasticizable and / or thermally decomposable and / or thermochemically decomposable. Materials with particularly good heat resistance include, for example, waxes. By using wax-containing organic materials, the cold casting mold can be softened or plasticized from approximately 35°C.

[0030] Organic materials such as waxes and / or polymers and / or plastics are significantly simpler and thus lower cost to use in additive manufacturing methods, such as 3D printing. The relatively low heat resistance of plastics allows cold casting molds additively manufactured from organic materials to plasticize or even decompose through pyrolysis and / or combustion thermal decomposition and / or thermochemical decomposition. Advantageously, for the structures and / or walls of cold casting molds, especially for support structures, filling channels, compensating volumes, etc., raw materials with lower melting points, such as waxes, are used as walls for cavity confinement in cold casting molds, which are subsequently additively manufactured, for example, from polymers or plastics, wherein the structures and / or walls do not confine the cavity or are directly connected to the cavity. In this way, stresses caused by heat during the plasticization or decomposition of the cold casting mold, which can damage the molded part, can be reduced or even completely avoided, in particular. Other properties of cold casting molds, such as water solubility, color, transparency, etc., can also be achieved by additive manufacturing with different raw materials, especially 3D printing, which can differentiate them in different areas. Organic raw materials may contain small amounts of inorganic materials as additives. For example, it is common to mix inorganic additives into plastics. However, the proportion of organic components is always higher than that of inorganic components.

[0031] According to a preferred design scheme, the mixture comprises metal powder, especially CrCo powder, or ceramic powder, especially alumina powder and / or zirconium oxide powder, and / or glass ceramic powder, especially lithium disilicate powder, and binder.

[0032] The binder-containing mixture can be dried in a cold casting mold without pressure, especially after hardening to the green body hardness. Therefore, the costly isostatic pressing known in the prior art can be abandoned by using a binder. However, in contrast to the methods also described in the prior art, it is necessary to harden the mixture while the cold casting mold is open (without a "lid"), allowing fluid to exit from the mold cavity through at least one opening. Binders are known in the prior art in various embodiments and are mostly composed of organic materials such as resins, surfactants, or waxes, which are directed to relatively low melting points.

[0033] In order to achieve gentle separation of the cold casting mold from the mixture before debinding or before the start of melting the binder, a method is modified to improve the temperature resistance and / or heat deformation resistance of the cold casting mold, especially the melting point and / or decomposition temperature of the cold casting mold being lower than the melting point of the binder and / or lower than the sintering temperature of the mixture, especially metal powder or ceramic powder.

[0034] Therefore, preferably, the mixture is hardened in the cavity of the cold casting mold before the disassembly of the cold casting mold is started or fully performed, especially to the hardness of the green blank.

[0035] The grading of cold casting molds can be designed according to a method that allows the mixture to be sintered to its final hardness before being initiated or fully performed by thermal action at a temperature range of 200°C to 650°C.

[0036] Suitablely, the melting point and / or decomposition temperature of the cold casting mold can be lower than the sintering temperature of the metal powder or ceramic powder.

[0037] An improved version of the method proposes that the organic material used in additive manufacturing of cold casting molds is first plasticized by thermal action at a temperature range of 35°C to 300°C and then decomposed by pyrolysis and / or by combustion thermochemical decomposition at a temperature range of 200°C to 650°C.

[0038] To facilitate the separation of the cavity walls from the mixture contained therein, the cold casting mold filled with the mixture is placed in a drying cabinet, air-conditioned cabinet, or sintering furnace and set at a temperature ranging from 35°C to 300°C. Here, the material properties of organic or plastic materials can be utilized. Organic materials, especially plastics, begin to soften before reaching the melting point of the cold casting mold, thus making the mold plasticizable or malleable. By selectively blowing in compressed air, the soft, deformable cold casting mold can be separated from the mixture, which is preferably already hardened (to the green body hardness).

[0039] Advantageously, the thermal decomposition and / or thermochemical decomposition of the cold casting mold is performed in a sintering furnace, wherein the cold casting mold is placed in the sintering furnace together with the mixture therein.

[0040] An alternative method step is proposed to pre-sinter the mixture before actual sintering, particularly at temperatures in the range of 650°C to 1300°C, so as to remove the binder portion before the molded part is compacted to its final hardness.

[0041] Thermal decomposition and / or thermochemical decomposition can then continue completely and / or at high temperatures within the sintering temperature range of 900°C to 2500°C, so that the cold casting mold can be dissolved without residue or at least with almost no residue by thermal action.

[0042] According to a variation of the method, the decomposition of cold casting molds is carried out thermally, especially pyrolytically, under anaerobic conditions or thermochemically, especially by combustion, under oxygen supply.

[0043] When pyrolyzing a cold-cast mold under anaerobic conditions, the mold, along with the mixture contained therein, is placed in a sintering furnace capable of sintering under vacuum and / or (low-oxygen or anaerobic) protective atmosphere. This method variation is particularly suitable for, for example, dental molds made of CrCo alloys, to avoid damage to the molded parts due to oxidation.

[0044] However, especially for obtaining ceramic molded parts, particularly dental molded parts, it is also feasible to modify the cold casting mold by combustion under oxygen supply according to another method.

[0045] Finally, according to a variation of the method, the walls of cold casting molds, especially the cavity-limiting parts of cold casting molds, can be coated with a coating agent before being filled with the mixture in order to avoid frictional fit and / or material fit between the cold casting mold and the mixture.

[0046] It is conceivable that the cold casting mold is dipped into a basin containing an organic oily liquid, such as petroleum, or alternatively flushed with an organic oily liquid, such as petroleum, just before or shortly before being filled with the mixture. In this way, a heat-resistant protective layer can be easily and uncomplicatedly constructed between the wall of the cold casting mold that limits the cavity and the mixture, without having to close the first and / or second openings.

[0047] In the case of dental molded parts, such as crowns, bridges, implants, and / or dentures, a thin-walled filament structure is typically required. High sintering temperatures are necessary for manufacturing dental molded parts from ceramic or metal. To avoid damage to the molded parts due to the thermal expansion of the cold-casting mold, the linear thermal expansion of the cold-casting mold, based on its initial geometry, is advantageously up to 10%, preferably up to 3%, and particularly preferably up to 0.8%, wherein the maximum thermal expansion of the cold-casting mold is achieved at a temperature less than or equal to 240°C, preferably less than or equal to 200°C, more preferably less than or equal to 150°C, and particularly preferably less than or equal to 100°C. Preferably, the coefficient of thermal expansion (WAK value) of the mixture, taking into account the corresponding WAK values ​​of the metal powder, ceramic powder, or glass-ceramic powder used, can be adjusted by the proportions of the polyelectrolyte and binder (polymer) in the cold-casting mold and their WAK values, so that the cold-casting mold and the mixture undergo similar or identical thermal expansion. Additionally or alternatively, the mechanical stability of the mixture (in the green state) can be improved by increasing the binder content.

[0048] To achieve the dimensional accuracy required for cold casting molds, especially for dental molds, in pressure filling methods, the cold casting molds have a Shore A hardness of at least 15 and / or a Shore D hardness of at least 10 and an elastic modulus of at least 5 MPa. The walls of the cavity boundaries of the cold casting mold preferably have a wall thickness of at least 0.01 mm. Shore hardness is a material characteristic value for elastomers and plastics and is defined in standards DIN EN ISO 868, DIN ISO 7619-1, and ASTM D2240-00. The elastic modulus, also known as the tensile modulus or E modulus, is determined, particularly for plastics, according to DIN EN ISO 527-1:2019-12.

[0049] An exemplary prototype of the cold casting mold according to the present invention is suitable for manufacturing molded parts, especially dental molded parts, manufactured according to stereolithography 3D printing method, and has the following physical properties:

[0050]

[0051] Attached Figure Description

[0052] Further details, features, combinations of features, advantages, and effects of the invention will become apparent from the following description and accompanying drawings of preferred embodiments of the invention. The drawings illustrate:

[0053] Figure 1 A flowchart illustrating an exemplary process for manufacturing a molded part, here for example a dental molded part, according to the present invention;

[0054] Figure 2 A schematic diagram of a cold casting mold is shown, the cavity of which corresponds to the shape of a denture.

[0055] Figure 3 A schematic perspective view of one embodiment of a cold casting mold is shown, the cold casting mold having a filling channel and a compensation volume;

[0056] Figure 4 Show Figure 3 A cross-sectional view of a cold casting mold;

[0057] Figure 5 A schematic perspective view of a second embodiment of a cold casting mold according to the present invention, having two filling channels;

[0058] Figure 6 A schematic perspective view of a molded part is shown, which is manufactured using a cold casting mold according to the invention.

[0059] The accompanying drawings are merely illustrative and for understanding the invention only. The same elements are given the same reference numerals and are therefore typically described only once. Detailed Implementation

[0060] Figure 1A flowchart illustrating an exemplary process for manufacturing a dental mold 210 according to the invention is shown. Here, (1) a cold casting mold 100 is first manufactured. The cold casting mold 100 is manufactured by means of additive manufacturing, such as by means of a 3D printer, wherein the cold casting mold 100 is manufactured to have at least one opening 111, 112. It is preferred to use a thermally degradable and / or thermally chemically degradable plastic as the raw material 150. Optionally, the cold casting mold 100 may be coated with a coating agent 220 (1.1) before it is filled with a mixture 200. For example, petroleum is suitable as the coating agent 220, wherein the cold casting mold 100 is preferably inserted into a basin containing petroleum. Next, the cold casting mold 100 is filled with the mixture 200 (2). Depending on the desired mold 210, the mixture 200 comprises a ceramic or metal powder 209 suitable for manufacturing dental molds. Preferably, the corresponding powder 209 is stirred into a slurry or paste by means of a diluent 205, such as water or an organic solvent, incorporates a binder 206, and is pretreated before use. The mixture 200 is filled into the cavity 110 of the cold casting mold 100 through at least one opening 111, 112. During filling, fluid 207, especially diluent 205 or air inclusions 208 contained in the mixture 200 can escape through at least one opening 111, 112. After filling, the mixture 200 is hardened or cured inside the cold casting mold 100, more precisely in its cavity 110 (3). To accelerate hardening or curing, the cold casting mold 100 is placed, for example, in a drying cabinet or air-conditioned box to set the desired humidity of the environment and to apply heat 230, so that the liquid components of the mixture 200 are dried or evaporated more quickly. Here, fluid 207, diluent 205, or air inclusions 208 can also escape through at least one opening 111, 112. For manufacturing ceramic or metal dental molded parts 210, hardening in the cold casting mold 100 is preferably performed up to the green body hardness. The stability of the green body is achieved by the binder 206 used.

[0061] After hardening or solidification, the cold casting mold 100, together with the hardened mixture 200 located therein, preferably escapes first in the sintering furnace at a temperature in the range of 35°C to 300°C and can be separated from the mixture 200, for example, by blowing in compressed air.

[0062] Suitablely, the cold casting mold 100 is thermally or thermochemically decomposed (4), followed by or simultaneously hardening the mixture 200 to its final hardness. For this purpose, the thermal decomposition or pyrolysis of the cold casting mold 100 in the absence of oxygen, or the thermochemical decomposition or combustion in the presence of oxygen, is initiated in a sintering furnace at a temperature ranging from 200°C to 650°C, wherein the raw material 150 is completely or nearly completely dissolved. Optionally, the mixture 200 may be pre-sintered (4.1) at a temperature ranging from 650°C to 1300°C, wherein the binder 206 volatilizes. During the final final sintering or densification sintering (5), the mixture 200 is compacted to its final hardness at a temperature ranging from 900°C to 2500°C and can be removed from the sintering furnace as the finished dental mold 210. Any remaining residues of the cold casting mold 100 that may not have been completely decomposed also decompose during pre-sintering or final sintering.

[0063] Figure 2 An exemplary embodiment of the invention is illustrated, wherein a cold casting mold 100 has a cavity 110 corresponding to the geometry of a dental mold 210. Schematably, a pressure nozzle 310 of a 3D printer 300 is also shown in the figure, by means of which the cold casting mold 100 is additively manufactured in one piece from raw material 150. The cold casting mold 100 includes a first opening 111 connected to a filling channel 130 via a compensation volume 131 in a fluid-conducting manner. The cavity 110 is filled via the filling channel 130 with a filling mechanism 400, exemplarily an syringe 420, using a mixture 200. Fluid 207 contained in the mixture 200 or air inclusions 208 generated during filling are discharged from the cavity 110 via a plurality of second openings 112. The second openings 112 are configured here as capillaries or pores located on the outer wall 121 and are therefore not visible to the naked eye. A porous or hygroscopic surface is created through multiple second openings 112, which conducts fluid 207 or moisture contained in the mixture 200 from the cavity to the external environment.

[0064] Figure 3 and 4 Embodiments of the cold casting mold 100 are shown in schematic perspective or cross-sectional views. The cold casting mold 100 is exemplarily constructed in the form of an examination body, the cavity 110 of which has typical geometry for a dental mold 210, resulting in a wall thickness of the mold 210 ranging from 0.30 mm to 10 mm. The cavity 110 of the cold casting mold 100 is defined by an outer wall 121 and an inner wall 122, such that the manufactured mold 210, for example a dental crown, has an internal cavity 211 (see...). Figure 6The cavity corresponds, for example, to the shape of an abutment, thereby allowing the crown to be fitted onto the abutment. The inner wall 122 is therefore configured in a cylindrical or truncated conical shape. A first opening 111 extends into the cavity 110, penetrating the outer wall 121 that engages with the dental mold 210. The cavity 110 is filled with the mixture 200 via the first opening 111. The inner wall 122 is penetrated by a plurality of second openings 112, which, for example, allow fluids 205, 207 and / or air inclusions 208 contained in the mixture 200 to escape during filling. After filling, fluids 205, 207, 208 can optionally be additionally drained via the first opening 111. The plurality of second openings 112 can, as exemplarily shown here, sieve-likely penetrate the inner surface of the cavity 110. Alternatively, the plurality of second openings 112 can be configured in the form of pores and / or capillaries, forming a porous and / or hygroscopic surface.

[0065] A filling channel 130, having a compensation volume 131, is connected to the first opening 111 in a fluid-conducting manner. A filling mechanism 400, such as a syringe 420, particularly a low-pressure syringe (see [reference]), can be installed at the filling channel 130. Figure 2 An inlet pipe, such as hose 410, can be connected to facilitate filling the cavity 110 with the mixture 200. The compensation volume 131 serves as a reservoir for the mixture 200, allowing fluids 205, 207, 208 escaping through the second opening 112 to be compensated by the mixture 200 stored in the compensation volume 131. In the illustrated embodiment, the cold casting mold 100 is manufactured as a single piece with the filling channel 130 and the compensation volume 131.

[0066] exist Figure 5 The diagram shows a schematic perspective view of a second embodiment of the cold casting mold 100 according to the present invention. The cold casting mold 100 corresponds to... Figure 1 and 2 The first embodiment shown in the figure is characterized by the filling channel 130 being configured without an optional compensation volume 131, and the channel-like second opening 112 being integrally inserted into the engaging, external wall portion 121. The filling channel 130 may optionally be implemented integrally or as an additional part of the cold casting mold 100 and its first opening 111 is inserted into the cavity 110. In this variant, the first opening 111 concentrically extends through the second opening 112. If necessary, a separate compensation volume 131, particularly as part of the filling mechanism 400, is connected to the filling channel 130.

[0067] The mixture 200, hardened to the final hardness required for the dental mold 210, is from... Figure 6The molded part 210 is manufactured using a cold-casting mold 100 configured as an examination body. The molded part 210 has a wall thickness ranging from 0.3 mm to 10 mm. The lower and uppermost sections of the molded part 210 are configured with recesses 211, the shape of which corresponds to the shape of a base, such as a crown, used to house the dental molded part 210. Through a plurality of second openings 112, the inwardly pointing wall portion of the recess 211 has a granular surface 212, and the second openings penetrate the inner wall portion 122 of the cold-casting mold 100 in a sieve-like structure (see...). Figure 4 The granular surface 212 improves the support between dental molds 210, such as crowns and abutments.

[0068] List of reference numerals

[0069] 100 Cold Casting Mold

[0070] 110 Cavity or Tool Mold

[0071] 111 First Opening

[0072] 112 Second opening

[0073] 120 wall section

[0074] 121 The outer wall portion

[0075] 122 The interior wall portion

[0076] 130 Fill Channel

[0077] 131 Compensation Volume

[0078] 140 Supporting Structure

[0079] 150 raw materials

[0080] 200 Mixture

[0081] 205 Diluent

[0082] 206 Adhesive

[0083] 207 Fluid

[0084] 208 Airborne impurities

[0085] 209 Powder

[0086] 210 Molded parts

[0087] 211 Notch

[0088] 220 Coating Agent

[0089] 230 heat / air humidity

[0090] 231 Light

[0091] 300 3D printer

[0092] 310 Pressure Nozzle

[0093] 400 filling mechanism

[0094] 420 syringes, especially low-pressure syringes

[0095] Method and steps:

[0096] 1. Manufacturing cold casting molds

[0097] 1.1 Coating of cold casting molds

[0098] 2. Fill the cold casting mold with the mixture.

[0099] 3. Harden and / or solidify the mixture in the cold casting mold.

[0100] 4. Thermal or thermochemical decomposition of cold casting molds.

[0101] 4.1 Pre-sintering

[0102] 5. Sintering / Final Sintering

Claims

1. A method for manufacturing a molded part (210) by using a cold casting mold (100) having a cavity (110) with geometrical aspects corresponding to the molded part and at least one opening (111, 112) leading into said cavity (110), said molded part being composed of a sinterable mixture (200), said method comprising the following steps: (1) A cold casting mold (100) is manufactured from raw materials (150) by means of additive manufacturing, wherein the cavity (110) is created based on digital data recording; (2) The cavity (110) of the cold casting mold (100) is filled with a sinterable mixture (200) through the at least one opening (111, 112). (3) Harden and / or solidify the sinterable mixture (200) in the cavity (110) of the cold casting mold (100), wherein Gases and / or liquids contained in and / or included in the sinterable mixture (200) are discharged from the cavity (110) via the at least one opening (111, 112); (4) The cold casting mold (100) is thermochemically decomposed at a temperature range of 200°C to 2500°C, wherein the cold casting mold (100) is placed in a sintering furnace together with a mixture (200) therein, and decomposed by pyrolysis under anaerobic conditions or by combustion under oxygen supply, wherein the mixture (200) comprises metal powder or ceramic powder and binder (206), wherein the melting point and / or decomposition temperature of the cold casting mold (100) is lower than the melting point or decomposition temperature of the binder (206), wherein the thermochemical decomposition of the cold casting mold (100) is performed in the sintering furnace; (5) The sinterable mixture (200) is sintered to the final hardness at a temperature range of 900°C to 2500°C until a molded part (210) is obtained, wherein step (4) is performed before step (5).

2. The method according to claim 1, Its features are, The mixture (200) exists as a slurry and / or paste and includes a diluent (205), wherein the mixture (200) is dried, hardened and / or cured in the cavity (110) of the cold casting mold (100) and the liquid and / or moisture portions of the mixture (200) are discharged from the cold casting mold (100) by means of the at least one opening (111, 112).

3. The method according to claim 1 or 2, Its features are, The cold casting mold (100) is additively manufactured to have at least one first opening (111) and at least one second opening (112), wherein the first opening leads into the cavity (110) and the second opening leads out from the cavity (110), wherein the cavity (110) of the cold casting mold (100) is filled via the first opening (111), and gas (208) and / or liquid contained in and / or included in a sinterable mixture (200) is discharged from the cavity (110) via the second opening (112).

4. The method according to claim 1 or 2, Its features are, At least one wall portion (120) of the cold casting mold (100) that defines the cavity (110) is additively manufactured to have, wholly or partially, a plurality of second openings (112) through the wall portion (120) into and / or out of the cavity (110), the second openings being used to drain gas (208) and / or liquid.

5. The method according to claim 1 or 2, Its features are, The mixture (200) in the cavity (110) of the cold casting mold (100) is hardened and / or cured by heat, wherein the cold casting mold (100) filled with the mixture (200) is placed in a drying cabinet, air conditioning box or sintering furnace and set at a temperature in the range of 30°C to 120°C and / or an air humidity in the range of 1% to 50%.

6. The method according to claim 1, Its features are, The digital data record of the design scheme for the geometry of the cavity (110) of the cold casting mold (100) includes the volume shrinkage of the mixture (200) caused by sintering and / or hardening.

7. The method according to claim 1, Its features are, In order to additively manufacture the cold casting mold (100), an organic material is used as a raw material (150) having a melting point or decomposition temperature in the temperature range of 40°C to 300°C, which enables the cold casting mold (100) to be plasticized and / or thermochemically decomposed.

8. The method according to claim 1, Its features are, The metal powder is CrCo powder, and the ceramic powder is alumina powder and / or zirconium oxide powder, and / or glass ceramic powder.

9. The method according to claim 1, Its features are, Before the disassembly of the cold casting mold (100) is initiated or fully performed, the mixture (200) is hardened to the green blank hardness in the cavity (110) of the cold casting mold (100).

10. The method according to claim 1, Its features are, Before sintering the mixture (200) to its final hardness, the decomposition of the cold casting mold (100) is initiated or fully performed by applying heat at a temperature in the range of 200°C to 650°C.

11. The method according to claim 10, Its features are, The melting point and / or decomposition temperature of the cold casting mold (100) is lower than the sintering temperature of the mixture (200).

12. The method according to claim 1, Its features are, The cold casting mold (100) is coated with a coating agent (220) before being filled with the mixture (200) in order to avoid friction fit and / or material bonding between the cold casting mold (100) and the mixture (200).

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