Methods and systems for the manufacture of layered three-dimensional forms

• US 7,807,077 B2
• Filed: 06/11/2004
• Issued: 10/05/2010
• Est. Priority Date: 06/16/2003
• Status: Active Grant

• Current Assignee: Exone GMBH (Desktop Metal, Inc.)
• Original Assignee: Voxeljet Technology GMBH (Voxeljet AG)
• Inventors: Ederer, Ingo, Hochsmann, Rainer
• Primary Examiner(s): Tentoni; Leo B
• Application Number:
  US10/866,205
• Publication Number:
  US 20050017394A1
• Time in Patent Office: 2,307 Days
• Field of Search: 264/112, 264/113, 264/308, 264/401
• US Class Current: 264/113
• CPC Class Codes: B22C 9/02 Sand moulds or like moulds for shaped castings
• CPC Class Codes: B22C 9/06 Permanent moulds for shaped castings moulds for ingots B22D7/06
• CPC Class Codes: B22C 9/10 Cores; Manufacture or installation of cores breaker cores B22C9/084
• 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
• CPC Class Codes: B33Y 10/00 Processes of additive manufacturing
• CPC Class Codes: B33Y 70/10 Composites of different types of material, e.g. mixtures of ceramics and polymers or mixtures of metals and biomaterials
• CPC Class Codes: B33Y 80/00 Products made by additive manufacturing
• CPC Class Codes: Y02P 10/25 Process efficiency

Abstract

New methods and systems for manufacturing a three-dimensional form, comprising steps of providing a plurality of particulates; contacting the particulates with an activation agent; contacting particulates having the activation agent with a binder material that is activatable by the activation agent; at least partially hardening the binder for forming a layer of the three-dimensional form; and repeating these steps to form the remainder of the three-dimensional form. Following sequential application of all required layers and binder material to make the form, the unbound particles are appropriately removed (and optionally re-used), to result in the desired three-dimensional form. The invention also contemplates a novel method for preparing a form, where unbound particulates free of binder material are re-claimed.

Claims

1. A method for manufacturing a three-dimensional metal casting mold, comprising:

a) providing a plurality of silica sand particulates that are substantially free of binder material;

b) coating at least a portion of a surface of each of the plurality of silica sand particulates with an activation agent;

c) contacting a pre-selected portion of the particulates having the activation agent present upon the particulates with a binder material that is activatable by the activation agent pursuant to which binder material is contacted with the particulates no earlier than when the binder material first contacts the activation agent;

d) at least partially hardening the binder material, crosslinking the binder material to itself and coupling adjoining particulates to each other with the binder material for forming a layer of the three-dimensional metal casting mold by the reaction between the binder material and the activation agent; and

e) repeating the steps (a)-(d) to form the remainder of the three-dimensional metal casting mold;

wherein the binder material includes molecules that cross-link among each other and the binder material is selected from the group consisting of phenol resin, polyisocyanate, polyurethane, epoxy resin, furane resin, polyurethane polymer, phenolic polyurethane, phenol-formaldehyde furfuryl alcohol, urea-formaldehyde furfuryl alcohol, formaldehyde furfuryl alcohol, peroxide, polyphenol resin, resol ester and mixtures thereof, and

wherein the binder material is present at a concentration of less than 2 weight percent based on the total weight of the mold.

2. The method of claim 1 wherein the activation agent is selected from the group consisting of acids, amines, alcohols, ketones, salts, and mixtures thereof.

3. The method of claim 2 wherein the binder material is selected from the group consisting of epoxy resin, furane resin, and mixtures thereof.

4. The method of claim 3 wherein heat is applied prior to or during the hardening step.

5. The method of claim 3 wherein the activation agent coating step (b) is done by a step selected from brushing, rolling, blading, spraying, plating or a combination thereof.

6. The method of claim 3 wherein the binder material contacting step (c) includes dispensing the binder material through a drop-on-demand dispenser.

7. The method of claim 1 wherein the viscosity of the binder material at 20°

C., ranges from 5 to 60 cps.

8. The method of claim 1, further comprising a step of re-using particulates that are not contacted with the binder material.

9. The method of claim 8 wherein the binder is an organic material, heat is applied prior to or during the hardening step, and the activation agent includes one or more acids selected from the group consisting of sulfuric acid, sulfonic acid, phosphoric acid, hydrochloric acid, and nitric acid.

10. The method of claim 9 further comprising pouring a material, selected from a metal or a plastic, in a molten state, into a resulting mold to form a part using the mold.

11. The method of claim 9 wherein the particulates are foundry sand particles, wherein 80 percent by volume of the particles have a diameter from 90 μ

m to 210 μ

m.

12. The method of claim 9, further comprising forming a core in the mold.

13. A method for manufacturing a three-dimensional metal casting mold, comprising:

a) coating a plurality of individual sand particles that are substantially free of binder material with an activation agent;

b) dispensing an organic activatable resin binder material through a print head over preselected portions of the sand particles that include the activation agent for contacting the activation agent, pursuant to which the dispensed binder material is contacted with the particles no earlier than when the binder material first contacts the activation agent;

c) reacting at a temperature of about 20°

C. to about 30°

C. the binder material with the activation agent for at least partially hardening the binder material, crosslinking the binder material to itself, and coupling adjoining particles to each other with the binder material, for forming a layer of the three-dimensional metal casting mold;

d) repeating the steps (a)-(c) to form the remainder of the three-dimensional metal casting mold; and

wherein the binder material includes at least one material selected from the group consisting of phenol resin, polyisocyanate, polyurethane, epoxy resin, furane resin, polyurethane polymer, phenolic polyurethane, phenol-formaldehyde furfuryl alcohol, urea-formaldehyde furfuryl alcohol, formaldehyde furfuryl alcohol, peroxide, polyphenol resin, resol ester, or mixtures thereof, and

wherein the binder material is present at a concentration of less than 2 weight percent based on the total weight of the mold.

14. A method according to claim 13, wherein the sand is selected from quartz, zircon, olivine, magnetite, or combination thereof, and wherein the particles include at least 80 percent by volume particles with an average particle size ranging from about 30 μ

m to about 450 μ

m.

15. A method according to claim 13, wherein the activation agent includes one or more acids selected from the group consisting of sulfuric acid, sulfonic acid, phosphoric acid, hydrochloric acid and nitric acid.

16. A method according to claim 13, wherein the activation agent includes an amine.

17. A method according to claim 16 wherein, the activation agent includes an aliphatic amine.

18. A method according to claim 16 wherein the activation agent includes an aromatic amine.

19. A method according to claim 15, wherein the sand includes reclaimed sand.

20. A method according to claim 16, wherein the sand includes reclaimed sand.

21. A method according to claim 15, wherein at least one period of at least 2 hours elapses between steps (a) and (b).

31. A method according to claim 13, wherein the ratio of binder to activation by weight is about 1:

4 to about 4;

1.

32. A method according to claim 13, further including a reinforcement.

22. A method for making a mold for a metal casting comprising the steps of:

a. coating a plurality of individual uncoated sand particles, having an uncoated diameter, with an acidic activation agent for forming a plurality of individual coated sand particles having a resulting diameter of about 1.0 to about 2.5 times the uncoated diameter;

b. spreading a layer of the coated sand particles on a workpiece platform by dispensing coated sand particles through an opening of a moveable hopper;

c. forming a smooth layer having a thickness of from about 0.15 to about 0.30 mm;

d. selectively contacting the resulting smooth layer with a furane resin binder material, a binder material, or both by dispensing the resin, in droplets of a density of 100 to 600 dots per inch and no earlier than when the furane resin or binder material first contacts the activation agent, through a piezo bending drop-on-demand print head, the binder being dispensed in an amount of about 2 parts binder to 1 part activation agent;

e. curing the binder at ambient room temperature for causing the binder to crosslink and covalently bond the resin to form a matrix in which the sand particles are dispensed;

f. repeating at least steps (b)-(e) until a metal casting mold is completed

wherein the binder material is present at a concentration of less than 2 weight percent based on the total weight of the mold.

23. A method according to claim 22 further comprising a step of reclaiming sand that is not contacted with the binder.

24. A method according to claim 23, wherein the sand includes reclaimed sand that is free of binder material.

25. A method according to claim 23, wherein the acidic activation agent includes one or more acids selected from the group consisting of sulfuric acid, sulfonic acid, phosphoric acid, hydrochloric acid, and nitric acid.

26. The method of claim 25, wherein the acid includes sulphuric acid.

27. The method of claim 25, wherein the acid includes sulfonic acid.

28. The method of claim 25, wherein the coating step includes contacting the sand particles with a polyol.

29. The method of claim 25, wherein the binder material comprises the furane resin binder material.

30. A method for manufacturing a three-dimensional metal casting mold, comprising the following successive steps:

a) providing a plurality of individual particulates comprising sand, wherein at least a portion of a surface of the individual particulates is pre-coated with an activation agent;

b) contacting a pre-selected portion of the particulates having the activation agent present upon the particulates with a binder material that is activatable by the activation agent;

and

c) at least partially hardening the binder material, for forming a layer of the three-dimensional metal casting mold;

wherein the binder material is present at a concentration of less than 2 weight percent based on the total weight of the mold.