Method for use in casting technology

• US 6,155,331 A
• Filed: 05/17/1996
• Issued: 12/05/2000
• Est. Priority Date: 05/27/1994
• Status: Expired due to Term

• Current Assignee: EOS GmbH Electro Optical Systems
• Original Assignee: EOS GmbH Electro Optical Systems
• Inventors: Keller, Peter, Wendt, Florian, Wilkening, Christian, Langer, Hans
• Primary Examiner(s): BATTEN JR, J REED
• Application Number:
  US08/571,838
• Time in Patent Office: 1,663 Days
• Field of Search: 164/6, 164/12, 164/15, 164/147.1, 164/4.1, 164/456
• US Class Current: 164/456
• CPC Class Codes: B22C 1/00 Compositions of refractory mould or core materials; Grain structures thereof refractory materials in general C04B35/00; Chemical or physical features in the formation or manufacture of moulds
• CPC Class Codes: B22C 1/02 characterised by additives for special purposes, e.g. indicators, breakdown additives
• CPC Class Codes: B22C 1/20 of organic agents
• CPC Class Codes: B22C 23/00 Tools; Devices not mentioned before for moulding
• CPC Class Codes: B22C 25/00 Foundry moulding plants for preparing mould materials B22C5/18; in combination with casting plants B22D47/02
• CPC Class Codes: B22C 9/02 Sand moulds or like moulds for shaped castings
• CPC Class Codes: B29C 2035/0827 using UV radiation
• CPC Class Codes: B29C 2035/0855 using microwave
• CPC Class Codes: B29C 64/153 using layers of powder being selectively joined, e.g. by selective laser sintering or melting
• CPC Class Codes: B29C 71/04 by wave energy or particle radiation , e.g. for curing or vulcanising preformed articles during moulding, e.g. in a mould B29C35/08
• CPC Class Codes: B33Y 10/00 Processes of additive manufacturing
• CPC Class Codes: B33Y 50/02 for controlling or regulating additive manufacturing processes
• CPC Class Codes: Y02P 10/25 Process efficiency

Abstract

The geometry of the cast part is provided as a digital pattern and an inverse pattern for the lost casting mold including any core is generated from the digital pattern. A layer of a particulate molding material is provided. The molding material is made of a first material and a second material. The first material is chemically inert when irradiated by electromagnetic radiation. The second material is curable by a chemical curing process that is initiated by electromagnetic radiation. The layer is scanned by irradiating electromagnetic radiation on places of the layer corresponding to the inverse pattern for the lost casting mold including any core. The irradiation is controlled to initiate the chemical curing process in the second material. The layer providing, scanning and controlling steps are repeated for subsequent layers of the molding material to connect each layer to the immediately preceding layer by the irradiation to produce the lost casting mold including any core for subsequently casting the desired cast part.

Claims

1. A method for manufacturing a three-dimensional lost casting mold including any core for sand casting of a cast part, the method comprising the following steps of:

providing the geometry of said cast part as a digital pattern;

generating from said digital pattern an inverse pattern for the lost casting mold including any core;

providing a layer of a particulate molding material, said molding material comprising a first material and a second material, said first material being chemically inert when irradiated by electromagnetic radiation and said second material being curable by a chemical curing process which is initiated by electromagnetic radiation,

scanning said layer by irradiating electromagnetic radiation on places of said layer corresponding to a cross-section of said inverse pattern for the lost casting mold including any core,

controlling said irradiation so as to initiate said chemical curing process in said second material, and

repeating said layer providing, scanning and controlling steps for subsequent layers of said molding material such that a subsequent layer is connected to the immediately preceding layer by said irradiation to produce the lost casting mold including any core for subsequently casting said cast part.

2. The method of claim 1, wherein said first material compromises silica sand, zirconic sand, olivine sand, chromite sand, chamotte, corundum, carbon sand, silica material or any other mineral material in pure form or mixed in any proportion with one or several of said other materials, said first material being granular, granulated or comminuted.

3. The method of claim 2, wherein said first material consists partly or entirely of previously used material, said material being regenerated or not regenerated and having adhering material which chemically reacts with said second material.

4. The method of claim 1 wherein said first material comprises a metal or ceramic powder.

5. The method of claim 1, wherein said second material comprises phenolic resin, furane resin, urea resin or amino resin, novolakes or resoles, urea formaldehyde resin, furfur alcohol urea formaldehyde resin, phenolic modified furane resin, phenolic formaldehyde resin, furfur alcohol phenolic formaldehyde resin, acrylic modified phenolic resin or any other resin which can be thermally cured either in liquid, solid, granular or powdery form and being modified and/or dissolved.

6. The method of claim 1, wherein said second material comprises epoxy resin, acrylic resin or polyacrylic resin.

7. The method of claim 1, wherein said molding material comprises particles of said first material, said particles being coated with said second material.

8. The method of claims 7, comprising coating said first material by cold coating, warm coating, hot coating or melt coating.

9. The method of claim 7, comprising adding one or more aggregates, accelerators, acids, iron oxide, separating agents, ammonium salts, hexamethylentetramine, hexamine, urea, magnetite, hematite, calcium stearate, glycerine, water or solving agent during said mixing of said first with said second material or during coating said first material with said second material.

10. The method of claim 1, wherein said molding material comprises a mixture of particles of said first material with particles of said second material.

11. The method of claim 1 comprising using a laser beam for irradiating said molding material and deflecting said laser beam to said places corresponding to said cross-section in said layer.

12. The method of claim 1 comprising irradiating said material in two-dimensional manner through a mask which is transparent to said irradiation at said places to be cured of said layer.

13. The method of claim 1 comprising using an electromagnetic radiation having a wavelength in the ultraviolet region.

14. The method of claim 1, comprising using electromagnetic radiation having a wavelength in the infrared region.

15. The method of claim 1, comprising selecting an energy input of said electromagnetic radiation into the molding material to be cured by varying an irradiation period and/or an intensity of said radiation so that said energy input starts said chemical curing process in said second material, whereas said first material does not react.

16. The method of claim 15, comprising observing a color change of said molding material and controlling said chemical curing process in accordance to said color change and readjusting said irradiation period and/or said intensity if necessary.

17. The method of claim 1, comprising carrying out said solidification selectively in an air, oxygen or inert gas atmosphere.

18. The method of claim 1, comprising carrying out said solidification selectively under pressure or reduced pressure.

19. The method of claim 1, comprising producing segments, shells, masks or other parts of molds and cores and combining said segments, shells, masks or other parts with lost cores, casting dies or cores or parts thereof produced with the same or different materials.

20. The method of claim 1, comprising producing a mold and core selectively in one piece or with one or several divisions and, in the latter case, combining said divided mold and core.

21. The method of claim 1 comprising producing several molds and cores simultaneously.

22. The method of claim 1, comprising completing said lost casting mold including any core by additions which are required by casting technology and produced in the same or a different manner from the same or different materials before using said lost casting mold including any core.

23. The method of claim 1, comprising providing said lost casting mold including any core with coating materials before using said lost casting mold including any core.

24. The method of claim 1, comprising thermally aftertreating said lost casting mold including any core for improving their strength and suitability for casting, said thermal aftertreating causing a further curing of said second material.

25. The method of claim 1, said molding material being dry and pourable.

26. A method of producing sand casting molds of warm curing mold material for casting a cast part, wherein molding sand is used as a mold material and a warm curing results from a chemical setting process initiated by electromagnetic radiation, the method comprising the following steps:

generating a computer model of a sand mold from digital information defining the geometry of said cast part;

providing a first layer of said molding sand;

directing electromagnetic radiation onto said first layer and using said computer model to control said directing said electromagnetic radiation onto places of said layer corresponding to said sand casting mold, and repeating said providing and directing steps for subsequent layers of said molding sand, and

removing unsolidified molding sand after solidification of all layers of said sand casting mold.

27. The method of claim 26, wherein said molding sand comprises silica sand having a phenolic resin coating.

28. The method of claim 26, comprising producing a casting mold having an integrated core.

29. The method of claim 26, comprising producing said casting mold in one piece.

30. The method of claim 26, comprising producing said casting mold with a runner gate.

31. The method of claim 26, comprising providing openings in said casting mold and removing uncured molding material through said openings after said solidification.

32. The method of claim 31, comprising producing said openings generating said computer model of said casting mold.

33. The method of claim 26, comprising producing a separate core.

34. The method of claim 33, comprising producing a one-piece core for a casting mold.

35. The method of claim 26, comprising using laser radiation as said electromagnetic radiation.

36. The method of claim 35 comprising using radiation of an infrared laser.

37. The method of claim 26, comprising the step of thermally post-curing said casting mold.

38. The method of claim 26, comprising the step of post-curing said casting mold by irradiation with micro waves.

39. The method of claim 26, said molding sand comprising silica sand, zirconic sand, olivine sand, chromite sand, chamotte, corundum or carbon sand or silica material, and warm or hot curing resin binder being added to each of said materials.

40. The method of claim 39, said warm or hot curing resin binder being a resin of the group of furane resins, urea resins or amino resins, urea formaldehyde resins, furfur alcohol urea formaldehyde resins, phenolic modified furane resins, phenolic formaldehyde resins, furfur alcohol phenolic formaldehyde resins, acrylic modified phenolic resins, acrylic resins or polyacrylic resins, each of said resins being either in liquid, solid, granulated or powdery form.

41. The method of claim 39, comprising the step of using an epoxy resin as resin binder.

42. The method of claim 26, comprising the step of inducing a chemical setting process in said resin when solidifying said molding sand, said setting process being started by said laser, wherein said sand does not chemically participate in said setting process.