Sinterable semi-crystalline powder and near-fully dense article formed therewith

• US 6,136,948 A
• Filed: 07/14/1997
• Issued: 10/24/2000
• Est. Priority Date: 11/23/1992
• Status: Expired

• Current Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Original Assignee: DTM Corporation (3D Systems Corporation)
• Inventors: Ng, Hendra, Forderhase, Paul F., Magistro, Angelo Joseph, Dickens, Elmer Douglas Jr., Taylor, Glenn Alfred, McAlea, Kevin P., Lee, Biing Lin
• Primary Examiner(s): BOYKIN, TERRESSA M
• Application Number:
  US08/892,583
• Time in Patent Office: 1,198 Days
• Field of Search: 528/323, 528/310, 156/62.2, 264/122, 264/125, 264/308, 428/325, 428/308.4, 428/317.9, 521/145, 521/919, 523/201, 523/205, 523/206, 525/902
• US Class Current: 528/323
• CPC Class Codes: B29C 2035/0838 using laser
• CPC Class Codes: B29C 41/003 characterised by the choice of material
• 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 67/04 Sintering combined with compression B29C43/00
• CPC Class Codes: B29K 2023/00 Use of polyalkenes or derivatives thereof as moulding material
• CPC Class Codes: B29K 2023/06 PE, i.e. polyethylene
• CPC Class Codes: B29K 2023/12 PP, i.e. polypropylene
• CPC Class Codes: B29K 2059/00 Use of polyacetals , e.g. POM, i.e. polyoxymethylene or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2067/006 PBT, i.e. polybutylene terephthalate
• CPC Class Codes: B29K 2077/00 Use of PA, i.e. polyamides, e.g. polyesteramides or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2079/00 Use of polymers having nitrogen, with or without oxygen or carbon only, in the main chain , not provided for in groups B29K2061/00 - B29K2077/00, as moulding material
• CPC Class Codes: B29K 2995/0094 Geometrical properties
• CPC Class Codes: B33Y 10/00 Processes of additive manufacturing
• CPC Class Codes: B33Y 70/00 Materials specially adapted for additive manufacturing
• CPC Class Codes: C08J 3/12 Powdering or granulating
• CPC Class Codes: C08J 9/24 by surface fusion and bonding of particles to form voids, e.g. sintering of expandable particles C08J9/232
• CPC Class Codes: Y10S 521/919 Sintered product
• CPC Class Codes: Y10S 525/902 Core-shell
• CPC Class Codes: Y10T 428/249958 Void-containing component is synthetic resin or natural rubbers
• CPC Class Codes: Y10T 428/249986 Void-containing component contains also a solid fiber or solid particle
• CPC Class Codes: Y10T 428/252 : Glass or ceramic [i.e., fired or glazed clay, cement, etc.] [porcelain, quartz, etc.]

Abstract

A laser-sinterable powder product has been prepared having unique properties which allow the powder to be sintered in a selective laser sintering machine to form a sintered part which is near-fully dense. For most purposes, the sintered part is indistinguishable from another part having the same dimensions made by isotropically molding the powder. In addition to being freely flowable at a temperature near its softening temperature, a useful powder is disclosed that has a two-tier distribution in which substantially no primary particles have an average diameter greater than 180 μm, provided further that the number average ratio of particles smaller than 53 μm is greater than 80%, the remaining larger particles being in the size range from 53 μm to 180 μm. A powder with slow recrystallization rates, as evidenced by non-overlapping or slightly overlapping endothermic and exothermic peaks in their differential scanning calorimetry characteristics for scan rates of on the order of 10° C. to 20° C. per minute, will also result in sintered parts that are near-fully dense, with minimal dimensional distortion.

Claims

1. A method of producing a three-dimensional object, comprising the steps of:

applying a layer of a powder at a target surface, the powder comprised of a semi-crystalline organic polymer, the powder having a melting peak and a recrystallization peak, as shown in differential scanning calorimetry traces, which slightly overlap when measured at a scanning rate of 10-20°

C./minute;

directing energy at selected locations of the layer corresponding to the cross-section of the object to be formed in the layer, to fuse the powder thereat;

repeating the applying and directing steps to form the object in layerwise fashion; and

removing unfused powder from the object.

2. The method of claim 1, wherein the polymer is selected from a group consisting of polyacetal, polypropylene, polyethylene, and ionomers.

3. The method of claim 1, wherein the polymer is selected from a group consisting of branched polyethylene and branched polypropylene.

4. The method of claim 1, wherein the powder has a melting point below about 200°

C.

5. The method of claim 1, wherein the overlap of the melting peak and the recrystallization peak is no more than about 13°

C.

6. The method of claim 1, wherein the overlap of the melting peak and the recrystallization peak is no more than about 11°

C.

7. An article formed of a semi-crystalline organic polymer powder that is laser-sintered in layerwise fashion, the powder having a melting peak and a recrystallization peak, as shown in differential scanning calorimetry traces, which slightly overlap when measured at a scanning rate of 10-20°

C./minute.

8. The article of claim 7, wherein the polymer is selected from a group consisting of polyacetal, polypropylene, polyethylene, and ionomers.

9. The article of claim 7, wherein the polymer is selected from a group consisting of branched polyethylene and branched polypropylene.

10. The article of claim 7, wherein the powder has a melting point below about 200°

C.

11. The article of claim 7, wherein the overlap of the melting peak and the recrystallization peak is no more than about 13°

C.

12. The article of claim 7, wherein the overlap of the melting peak and the recrystallization peak is no more than about 11°

C.

13. A method of producing a three-dimensional object, comprising the steps of:

applying a layer of a powder at a target surface, the powder comprised of a semi-crystalline organic polyester-based polymer, the powder having a melting peak and a recrystallization peak, as shown in differential scanning calorimetry traces, which do not substantially overlap when measured at a scanning rate of 10-20°

C./minute;

directing energy at selected locations of the layer corresponding to the cross-section of the object to be formed in the layer, to fuse the powder thereat;

repeating the applying and directing steps to form the object in layerwise fashion; and

removing unfused powder from the object.

14. An article formed of a semi-crystalline organic polyester-based polymer powder that is laser-sintered in layerwise fashion, the powder having a melting peak and a recrystallization peak, as shown in differential scanning calorimetry traces, which do not substantially overlap when measured at a scanning rate of 10-20°

C./minute.

15. A method of producing a three-dimensional object, comprising the steps of:

applying a layer of a powder at a target surface, the powder comprised of a semi-crystalline organic polymer, the powder having a caking temperature (T_c) that is greater than a softening point temperature (T_s) of the powder, as shown in differential scanning calorimetry traces;

directing energy at selected locations of the layer corresponding to the cross-section of the object to be formed in the layer, to fuse the powder thereat;

repeating the applying and directing steps to form the object in layerwise fashion; and

removing unfused powder from the object.

16. The method of claim 15, wherein the polymer is a nylon.

17. The method of claim 16, wherein the nylon is selected from a group consisting of nylon 6, nylon 11, and nylon 12.

18. The method of claim 15, wherein the polymer is a polyester-based polymer.

19. The method of claim 15, wherein the polymer is selected from a group consisting of polyacetal, polypropylene, polyethylene, and ionomers.

20. The method of claim 15, wherein the polymer is selected from a group consisting of branched polyethylene and branched polypropylene.

21. The method of claim 15, wherein the powder has a melting point below about 200°

C.

22. A method of producing a three-dimensional object, comprising the steps of:

applying a layer of a powder at a target surface, the powder comprised of a semi-crystalline organic polymer selected from a group consisting of nylon 6, nylon 11, and nylon 12;

directing energy at selected locations of the layer corresponding to the cross-section of the object to be formed in the layer, to fuse the powder thereat;

repeating the applying and directing steps to form the object in layerwise fashion; and

removing unfused powder from the object.

23. An article formed of a semi-crystalline organic polymer powder that is laser-sintered in layerwise fashion, the powder having a caking temperature (T_c) that is greater than a softening point temperature (T_s) of the powder, as shown in differential scanning calorimetry traces.

24. The article of claim 23, wherein the polymer is a nylon.

25. The article of claim 24, wherein the nylon is selected from a group consisting of nylon 6, nylon 11, and nylon 12.

26. The article of claim 23, wherein the polymer is a polyester-based polymer.

27. The article of claim 23, wherein the polymer is selected from a group consisting of polyacetal, polypropylene, polyethylene, and ionomers.

28. The article of claim 23, wherein the polymer is selected from a group consisting of branched polyethylene and branched polypropylene.

29. The article of claim 23, wherein the powder has a melting point below about 200°

C.

30. An article formed of a semi-crystalline organic polymer powder that is laser-sintered in layerwise fashion, the powder comprised of a semi-crystalline organic polymer selected from a group consisting of nylon 6, nylon 11, and nylon 12.