Process for producing a moulding using a water-soluble casting mould and material system for the production thereof

• US 10,343,301 B2
• Filed: 02/18/2014
• Issued: 07/09/2019
• Est. Priority Date: 02/28/2013
• Status: Active Grant

• Current Assignee: Voxeljet AG
• Original Assignee: Voxeljet AG
• Inventors: Gunther, Daniel, Gnuchtel, Ingo, Karrer, Beat
• Primary Examiner(s): Wollschlager, Jeffrey M
• Assistant Examiner(s): Melendez, Armand
• Application Number:
  US14/768,533
• Publication Number:
  US 20150375419A1
• Time in Patent Office: 1,967 Days
• Field of Search: None
• CPC Class Codes: B28B 7/342 which are at least partially destroyed, e.g. broken, molten, before demoulding; Moulding surfaces or spaces shaped by, or in, the ground, or sand or soil, whether bound or not; Cores consisting at least mainly of sand or soil, whether bound or not
• CPC Class Codes: B28B 7/346 Manufacture of moulds
• CPC Class Codes: B28B 7/36 Linings or coatings, e.g. removable, absorbent linings, permanent anti-stick coatings; Linings becoming a non-permanent layer of the moulded articlelubricating surfaces of moulds, cores or mandrels B28B7/38
• CPC Class Codes: B29C 33/3842 Manufacturing moulds, e.g. shaping the mould surface by machining
• CPC Class Codes: B29C 33/52 soluble or fusible in particular used in injection moulding B29C45/4457
• CPC Class Codes: B29C 33/56 Coatings , e.g. enameled or galvanised; Releasing, lubricating or separating agents in-mould coating B29C37/0028; using or applying separating agents B29C37/0067
• CPC Class Codes: B29C 64/10 Processes of additive manufacturing
• CPC Class Codes: B29C 64/165 using a combination of solid and fluid materials, e.g. a powder selectively bound by a liquid binder, catalyst, inhibitor or energy absorber

Abstract

A method for producing molded parts (16), a water-soluble casting mold (6) being produced in a first step using a layering method, in particular using a powder bed-based layering method. In a second step, the surface of the casting mold (6) is sealed with the aid of a material (9; 10). A casting of the molded part (16) is then formed by filling the casting mold (6) with a free-flowing, hardenable material (13), in particular a hydraulically setting material. After the casting has solidified, the casting mold (6) is dissolved with the aid of an aqueous solution (18), in particular a heated aqueous solution (18). The present application furthermore relates to a material system for producing a water-soluble casting mold (6), comprising at least one water-soluble material for building a casting mold (6) in a layering method, as well as comprising at least one material (9; 10) for sealing the surface of the casting mold (6).

Claims

1. A method for producing a molded part, comprising the following steps:

a) producing a water-soluble casting mold using a layering method, wherein the layering method is a powder bed-based layering method where particulate material is applied in thin layers and selectively printed upon with a computer-controlled print head;

b) sealing the surface of the casting mold with a sealing material including at least one water insoluble material;

c) generating a casting of the molded part by filling the casting mold with a free-flowing, hardenable material; and

d) dissolving the casting mold with the aid of an aqueous solution, characterized in that the casting mold is produced in a 3D printing method;

wherein the particulate material includes a sand, a gypsum, a metal, or a ceramic powder;

the sealing material penetrates pores between individual particles of the casting mold;

a material of the casting mold in the layering method includes a binder;

the hardenable material is capable of a binding action with the binder or the partiuclate material, and

the sealing material prevents the binding action.

2. The method according to claim 1, characterized in that the surface of the casting mold is sealed by immersion in a bath, by being sprayed and/or by being brushed with the sealing material.

3. The method according to claim 1, characterized in that an underpressure above an ambient pressure or an overpressure below the ambient pressure is applied to the casting mold when it is filled with the free-flowing, hardenable material, and/or the casting mold is subjected to a shaking motion or a temperature increase.

4. The method according to claim 1, characterized in that the casting mold is dissolved by immersion in a bath containing the heated aqueous solution.

5. The method of claim 4, wherein the dissolution is accelerated by:

movements of the casting mold within the bath;

or

the application of ultrasound.

6. The method according to claim 1, characterized in that the hardenable material includes a casting polyamide.

7. The method of claim 1, wherein the free-flowing, hardenable material is a hydraulically setting material.

8. The method of claim 1, wherein the aqueous solution is a heated aqueous solution.

9. The method of claim 7, wherein the water-soluble casting mold includes at least one water-soluble binder.

10. The method of claim 9, wherein the at least one water-soluble binder includes at least one inorganic compound.

11. The method of claim 10, wherein the at least one water-soluble binder includes at least one polysaccharide, at least one salt and/or at least one water-soluble polymer, or a mixture thereof.

12. The method of claim 9, wherein the sealing material includes a water-insoluble material including a wax or a water-insoluble polymer.

13. The method of claim 12, wherein

the surface of the casting mold is sealed by immersion in a bath, by being sprayed and/or by being brushed with the sealing material;

an underpressure above an ambient pressure or an overpressure below the ambient pressure is applied to the casting mold when it is filled with the free-flowing, hardenable material, and/or

the casting mold is subjected to a shaking motion or a temperature increase; and

the casting mold is dissolved by immersion in a bath containing the aqueous solution, the dissolution being accelerated by movements of the casting mold within the bath or by a temperature increase and/or by the application of ultrasound.

14. The method of claim 1, wherein the water-soluble casting mold is produced from a material system including

a) at least one water-soluble material for building a casting mold in a layering method, which comprises at least one particulate material as well as at least one water-soluble binder;

and

b) the sealing material for sealing the surface of the casting mold.

15. The method of claim 14, wherein the sealing material for sealing the surface of the casting mold includes a wax, at least one fatty acid, at least one water-insoluble polymer, stearyl alcohol and/or cetyl alcohol, or a mixture thereof.

16. The method of claim 15, wherein

the surface of the casting mold is sealed by immersion in a bath, by being sprayed and/or by being brushed with the sealing material;

an underpressure above an ambient pressure or an overpressure below the ambient pressure is applied to the casting mold when it is filled with the free-flowing, hardenable material, and/or

the casting mold is subjected to a shaking motion or a temperature increase; and

the casting mold is dissolved by immersion in a bath containing the aqueous solution, the dissolution being accelerated by movements of the casting mold within the bath or by a temperature increase and/or by the application of ultrasound.

17. The method of claim 1, wherein the dissolving of the casting mold is after the casting has solidified and the aqueous solution is temperature controlled.

18. The method of claim 1, wherein the binding action includes a chemical reaction of the hardenable material with the binder or the partiuclate material, and wherein the sealing material prevents the chemical reaction.

19. The method of claim 1, wherein the method includes a step of washing the water-insoluble material off of the molded part.

20. The method of claim 1, wherein the hardenable material includes a free-flowing material that transitions to a hardened state by a polymerization reaction.

21. The method of claim 1, wherein the casting mold has a rough surface and the sealing material smooths the surface.

22. The method of claim 1, wherein the casting mold is cleaned and a surface is mechanically processed before the step of sealing.

23. The method of claim 1, wherein the sealing material includes a wax, a fatty acid, a water-insoluble polymer, a stearyl alcohol, or a cetyl alcohol.

24. The method of claim 1, wherein the binding action includes hardening by forming a crystalline structure.

25. A method of for producing a molded part, comprising the following steps:

a. producing a water-soluble casting mold using a layering method, wherein the layering method is a powder bed-based layering method where particulate material is applied in thin layers and selectively printed upon with a computer-controlled print head;

b. sealing the surface of the casting mold with a sealing material including a water insoluble material including at least one water insoluble material;

c. generating a casting of the molded part by filling the casting mold with a free-flowing, hardenable material; and

d. dissolving the casting mold with the aid of a heated aqueous solution, wherein the casting mold is produced in a 3D printing method;

the sealing material penetrates pores between individual particles of the casting mold;

a material of the casting mold in the layering method includes a binder;

the hardenable material is capable of a binding action with the binder or the partiuclate material, and

the sealing material prevents the binding action.

26. The method of claim 25, wherein

the surface of the casting mold is sealed by immersion in a bath, by being sprayed and/or by being brushed with the sealing material;

an underpressure above an ambient pressure or an overpressure below the ambient pressure is applied to the casting mold when it is filled with the free-flowing, hardenable material, and/or

the casting mold is subjected to a shaking motion or a temperature increase; and

the casting mold is dissolved by immersion in a bath containing the aqueous solution, the dissolution being accelerated by movements of the casting mold within the bath or by a temperature increase and/or by the application of ultrasound;

and wherein the sealing material includes a wax, at least one fatty acid, at least one water-insoluble polymer, stearyl alcohol and/or cetyl alcohol, or a mixture thereof.