METHOD FOR PRODUCING MOULDED PARTS, IN PARTICULAR DENTAL MOULDED PARTS

Abstract

A method for producing molded parts from a sinterable mixing compound using a cold casting mold having a cavity that corresponds geometrically to the molded part and at least one opening into the cavity, wherein the mold is additively constructed from a starting material, in particular a 3D printing method using a 3D printer, and wherein the cavity is created on the basis of a digital data set, in particular based on a three-dimensional model of the oral cavity of a patient. The cavity is filled via the opening with the sinterable mixing compound, curing and/or solidifying the mixing compound, wherein gases and/or liquids contained in the mixing compound are discharged from the cavity via the opening, thermally and/or thermochemically decomposing the mold at a temperature from 200° C. to 2500° C. and sintering the mixing compound to hardness at a temperature from 900° C. to 2500° C. until a molded part is obtained.

Claims

1. A method for producing molded parts (210) from a sinterable mixing compound (200) using a cold casting mold (100) having a cavity (110) that corresponds geometrically to the molded part and at least one opening (111, 112) opening into the cavity (110), the method comprising the following method steps: (1) producing the cold casting mold (100) by means of an additive material construction method from a starting material (150), wherein the cavity (110) is created on the basis of a digital data set, based on a three-dimensional model of the oral cavity of a patient, (2) filling the cavity (110) of the cold casting mold (100) via the at least one opening (111, 112) with the sinterable mixing compound (200), (3) curing or solidifying the sinterable mixing compound (200) in the cavity (110) of the cold casting mold (100), wherein gases or liquids contained or enclosed in the sinterable mixing compound (200) are discharged from the cavity (110) via the at least one opening (111, 112), (4) thermally or thermochemically decomposing the cold casting mold (100) at a temperature in a temperature range from 200° C. to 2500° C., (5) sintering the sinterable mixing compound (200) to final hardness at a temperature in a temperature range from 900° C. to 2500° C. until a molded part (210) is obtained.

2. The method as claimed in claim 1, characterized in that the mixing compound (200) is provided as a slurry or pasty mass and comprises a diluent (205), wherein the mixing compound (200) cures or solidifies in the cavity (110) of the cold casting mold (100) by drying and a liquid component or moisture content of the mixing compound (200) is discharged by means of the at least one opening (111, 112) from the cold casting mold (100).

3. The method as claimed in claim 2, characterized in that the cold casting mold (100) is additively constructed having at least one first opening (111) opening into the cavity (110) or leading out of the cavity (110) and having at least one second opening (112) opening into the cavity (110) or leading out of the cavity (110), wherein the cavity (110) of the cold casting mold (100) is filled via the first opening (111) and gases contained or enclosed in the sinterable mixing compound (200) are discharged via the second opening (112) from the cavity (110).

4. The method as claimed in claim 3, characterized in that at least one wall (120) of the cold casting mold (100) delimiting the cavity (110) is additively constructed completely or in regions having a plurality of second openings (112), which open into the cavity (110) or lead out of the cavity (110) and penetrate this wall (120), for discharging gases.

5. The method as claimed in claim 1, characterized in that the mixing compound (200) cures or solidifies in the cavity (110) of the cold casting mold (100) under the action of heat, wherein the cold casting mold (100) filled with the mixing compound (200) is placed in a drying cabinet, climatic cabinet, or a sintering furnace and a temperature in a temperature range from 30° C. to 120° C. or humidity in a range from 1% to 50% is set.

6. The method as claimed in claim 1, characterized in that the digital data set, which is based on a three-dimensional model of the oral cavity of a patient, for the geometric design of the cavity (110) of the cold casting mold (100) comprises a sintering-related or curing-related volume shrinkage of the mixing compound (200).

7. The method as claimed in claim 1, characterized in that an organic material, is used as the starting material (150) for additively constructing the cold casting mold (100), so that the cold casting mold (100) can be plasticized or thermally or thermochemically decomposed.

8. The method as claimed in claim 1, characterized in that the mixing compound (200) comprises a metal powder (209) or a ceramic powder (209), or a zirconium oxide powder or a glass ceramic powder and a binder (206).

9. The method as claimed in claim 8, characterized in that the melting point or the decomposition temperature of the cold casting mold (100) is below the melting point or the decomposition temperature of the binder (206).

10. The method as claimed in claim 9, characterized in that the mixing compound (200) in the cavity (110) of the cold casting mold (100) cures to green body hardness before the decomposition of the cold casting mold (100) is initiated or completely carried out.

11. The method as claimed in claim 10, characterized in that the decomposition of the cold casting mold (100) is initiated or carried out completely by the action of heat at a temperature in a temperature range from 200° C. to 650° C., before the mixing compound (200) is sintered to final hardness.

12. The method as claimed in claim 11, characterized in that the melting point or the decomposition temperature of the cold casting mold (100) is below the sintering temperature of the mixing compound (200).

13. The method as claimed in claim 8, characterized in that the thermal or thermochemical decomposition of the cold casting mold (100) is carried out in a sintering furnace, wherein the cold casting mold (100) is placed in the sintering furnace together with the mixing compound (200) located therein.

14. The method as claimed in claim 13, characterized in that the decomposition of the cold casting mold (100) is carried out thermally under oxygen-free conditions or thermochemically with a supply of oxygen.

15. The method as claimed in claim 1, characterized in that the cold casting mold (100) is coated using a coating agent (220) before the filling with the mixing compound (200) in order to avoid a frictional or materially-bonded connection between the cold casting mold (100) and the mixing compound (200).

16. The method as claimed in claim 1 wherein the cold casting mold (100) is produced by a 3D printing method using a 3D printer (300).

17. The method as claimed in claim 7 wherein the organic material is an organic polymer or a wax or a plastic, having a melting point or a decomposition temperature in a temperature range from 40° C. to 300° C.

18. The method as claimed in claim 8 wherein the mixing compound (200) comprises a CrCo powder or a zirconium oxide powder or a glass ceramic powder or a lithium disilicate powder.

19. The method as claimed in claim 14 wherein the decomposition of the cold casting mold (100) is carried out thermally under oxygen-free conditions pyrolytically or thermochemically with a supply of oxygen by combustion.

20. The method as claimed in claim 15 wherein the interior walls (120) of the cold casting mold (100) delimiting the cavity (110) are coated using the coating agent (220) before filling with the mixing compound (200).

Description

DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0049] Further details, features, feature (sub-)combinations, advantages, and effects on the basis of the invention will be apparent from the following description of a preferred exemplary embodiment and from the drawings. In the figures

[0050] FIG. 1 shows a flow chart of an exemplary sequence of the method according to the invention for producing a molded part, here using the example of a dental molded part,

[0051] FIG. 2 shows a schematic representation of a cold casting mold whose cavity corresponds to the shape of a denture,

[0052] FIG. 3 shows a schematic perspective representation of an embodiment of a cold casting mold having a filling channel and a compensating volume,

[0053] FIG. 4 shows a sectional view of the cold casting mold from FIG. 3,

[0054] FIG. 5 shows a schematic perspective representation of a second exemplary embodiment of a cold casting mold according to the invention having two filling channels,

[0055] FIG. 6 shows a schematic perspective representation of a molded part which was produced using a cold casting mold according to the invention.

[0056] The figures are merely of an exemplary nature and are used only to understand the invention. The same elements are provided with the same reference numerals and are therefore usually only described once.

DETAILED DESCRIPTION OF THE INVENTION

[0057] FIG. 1 shows a flow chart of an exemplary sequence of the method according to the invention for the production of a dental molded part 210. In this case, a cold casting mold 100 is first produced (1). The cold casting mold 100 is constructed by means of an additive material construction method, for example using a 3D printer, wherein the cold casting mold 100 is constructed having at least one opening 111, 112. A thermally and/or thermochemically decomposable plastic is preferably used as the starting material 150. Optionally, the cold casting mold 100 can be coated with a coating agent 220 before it is filled with the mixing compound 200 (1.1). Petroleum, for example, is suitable as the coating agent 220, wherein the cold casting mold 100 is preferably immersed in a basin containing petroleum. The cold casting mold 100 is then filled with the mixing compound 200 (2). Depending on the desired molded part 210, the mixing compound 200 comprises a ceramic or metallic powder 209, which is suitable for the production of dental shaped parts. The respective powder 209 is preferably mixed with a diluent 205, for example water or an organic solvent, to form a slurry or a pasty mass, admixed with a binder 206, and conditioned before use. The mixing compound 200 is filled into the cavity 110 of the cold casting mold 100 via the at least one opening 111, 112. Fluids 207 contained in the mixing compound 200, in particular the diluent 205 or air inclusions 208, can already escape via the at least one opening 111, 112 during the filling. After the filling, the mixing compound 200 cures or solidifies inside the cold casting mold 100, more precisely in its cavity 110 (3). In order to accelerate the curing or solidifying, the cold casting mold 100 is placed, for example, in a drying cabinet or climatic cabinet to set a desired ambient humidity of the environment, and heat 230 is applied, so that the liquid components of the mixing compound 200 dry or evaporate more quickly. Fluids 207, diluents 205, or air inclusions 208 can continue to escape via the at least one opening 111, 112. For the production of ceramic or metallic dental molded parts 210, the curing in the cold casting mold 100 is preferably carried out up to green body hardness. The stability of the green body can be achieved by the binder 206 used.

[0058] After the curing or solidifying, the cold casting mold 100, together with the cured mixing compound 200 located therein, is preferably initially softened in a sintering furnace at a temperature in a range from 35° C. to 300° C. and can, for example, be “inflated” by blowing in compressed air and detached from the mixing compound 200.

[0059] The cold casting mold 100 is expediently decomposed thermally or thermochemically (4) before or while the mixing compound 200 cures to final hardness. For this purpose, thermal decomposition or pyrolysis in the absence of oxygen or thermochemical decomposition or combustion with oxygen of the cold casting mold 100 is initiated in a sintering furnace at a temperature in a temperature range from 200° C. to 650° C., at which the starting material 150 is completely or almost completely dissolved. At a temperature in a temperature range from 650° C. to 1300° C., the mixing compound 200 can optionally be pre-sintered (4.1), wherein the binder 206 evaporates. During the ultimate final or dense sintering (5), the mixing compound 200 is compacted to final hardness at a temperature in a temperature range from 900° C. to 2500° C. and can be removed from the sintering furnace as a finished dental molded part 210. Any remnants of the cold casting mold 100 that are not yet completely decomposed are also decomposed during pre-sintering or final sintering.

[0060] FIG. 2 shows an exemplary embodiment of the invention, in which the cold casting mold 100 has a cavity 110 which corresponds to the geometry of a dental molded part 210. Also indicated schematically in the figure is a pressure nozzle 310 of a 3D printer 300, by means of which the cold casting mold 100 is integrally constructed additively from the starting material 150. The cold casting mold 100 comprises a first opening 111 which connects to a filling channel 130 in a fluid-conducting manner via a compensating volume 131. The cavity 110 is filled with the mixing compound 200 via the filling channel 130 using a filling means 400, here by way of example an injection syringe 420. Fluids 207 contained in the mixing compound 200 or air inclusions 208 occurring during filling are discharged from the cavity 110 via a plurality of second openings 112. The second openings 112 are formed here as capillaries or pores in the external walls 121 and are therefore not visible to the naked eye. The large number of second openings 112 creates a porous or hygroscopic surface, which conducts fluids 207 or moisture contained in the mixing compound 200 out of the cavity to the external environment.

[0061] FIGS. 3 and 4 each show an exemplary embodiment of a cold casting mold 100, in a schematic perspective view and in a sectional view, respectively. The cold casting mold 100 is embodied here, for example, in the form of a test specimen, the cavity 110 of which has geometric properties typical for dental molded parts 210, which result in wall thicknesses of the molded part 210 in a range from 0.30 mm to 10 mm. The cavity 110 of the cold casting mold 100 is delimited by the external walls 121 and the internal walls 122 of the cold casting mold 100, so that the finished molded part 210, for example a crown, has an internal cavity 211 (see FIG. 6) which, for example, corresponds to the shape of an abutment, as a result of which the crown can be placed on the abutment. For this purpose, the internal walls 122 form a cylindrical or truncated cone shape. A first opening 111 opens into the cavity 110 and penetrates one of the external walls 121, which are occlusal with respect to the dental molded part 210. The cavity 110 is filled with the mixing compound 200 via the first opening 111. The internal walls 122 are penetrated using a plurality of second openings 112 which, for example, allow fluids 205, 207 and/or air inclusions 208 contained in the mixing compound 200 to escape already during the filling. After the filling, fluids 205, 207, 208 can optionally also escape via the first opening 111. The plurality of second openings 112 can, as shown here by way of example, penetrate an inner lateral surface of the cavity 110 like a sieve. Alternatively, the plurality of second openings 112 could be embodied in the form of pores and/or capillaries and form a porous and/or hygroscopic surface.

[0062] A filling channel 130 having a compensating volume 131 adjoins the first opening 111 in a fluid-conducting manner. Filling means 400, for example injection syringes 420, in particular low-pressure injection syringes (see FIG. 2) or supply lines, such as hoses 410 can be connected to the filling channel 130 to facilitate the filling of the cavity 110 with mixing compound 200. The compensating volume 131 is used as a type of reservoir for the mixing compound 200, so that the volume loss of fluids 205, 207, 208 escaping through the second openings 112 can be compensated for by means of the mixing compound 200 stored in the compensating volume 131. In the exemplary embodiment shown, the cold casting mold 100 is produced integrally with the filling channel 130 and the compensating volume 131.

[0063] FIG. 5 shows a schematic perspective representation of a second exemplary embodiment of a cold casting mold 100 according to the invention. The cold casting mold 100 corresponds to the first exemplary embodiment shown in FIGS. 1 and 2, with the exception that the filling channel 130 is formed without the (optional) compensating volume 131 and a channel-like second opening 112 opens integrally into the occlusal external wall 121. The filling channel 130 can optionally be implemented integrally or also as an additional part of the cold casting mold 100 and opens with its first opening 111 into the cavity 110. In this variant, the first opening 111 penetrates the second opening 112 concentrically. If required, a separate compensating volume 131 can be connected to the filling channel 130, in particular as part of a filling means 400.

[0064] The mixing compound 200 cured to the final hardness required for dental molded parts 210 can be seen in FIG. 6 as a finished molded part 210, which was produced using the cold casting mold 100 designed as a test specimen. The molded part 210 has wall thicknesses in a range from 0.3 mm to 10 mm. A lower, apical section of the molded part 210 is formed having a recess 211, the shape of which corresponds to the shape of an abutment for placing a dental molded part 210, for example a crown. The inward facing walls of the recess 211 are provided with a nubby surface 212 due to the plurality of second openings 112 which penetrate the internal walls 122 of the cold casting mold 100 in a sieve-like structure (see FIG. 4). The nubby surface 212 improves the hold between the dental molded part 210, for example a crown and, for example, an abutment.

LIST OF REFERENCE SIGNS

[0065] 100 cold casting mold [0066] 110 cavity or tool shape [0067] 111 first opening [0068] 112 second opening [0069] 120 wall [0070] 121 external wall [0071] 122 internal wall [0072] 130 filling channel [0073] 131 compensating volume [0074] 140 support structure [0075] 150 starting material [0076] 200 mixing compound [0077] 205 diluent [0078] 206 binder [0079] 207 fluids [0080] 208 air inclusions [0081] 209 powder [0082] 210 molded part [0083] 211 recess [0084] 220 coating agent [0085] 230 heat/ambient humidity [0086] 231 light [0087] 300 3D printer [0088] 310 pressure nozzle [0089] 400 filling means [0090] 420 injection syringe, in particular low-pressure injection syringe

Method Steps:

[0091] 1 producing a cold casting mold [0092] 1.1 coating the cold coasting mold [0093] 2 filling the cold casting mold with mixing compound [0094] 3 curing and/or solidifying the mixing compound in the cold casting mold [0095] 4 thermally or thermochemically decomposing the cold casting mold [0096] 4.1 pre-sintering [0097] 5 sintering/final sintering