Laser sintering method with increased process precision, and particles used for the same

• US 20060159896A1
• Filed: 06/16/2003
• Published: 07/20/2006
• Est. Priority Date: 06/18/2002
• Status: Abandoned Application

• Current Assignee: Daimler AG (Mercedes-Benz Group AG)
• Original Assignee: Daimler AG (Mercedes-Benz Group AG)
• Inventors: Pfeifer, Rolf, Shen, Jialin
• Application Number:
  US10/518,699
• Publication Number:
  US 20060159896A1
• Time in Patent Office: Days
• US Class Current: 428/206
• CPC Class Codes: B22F 1/10 Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
• CPC Class Codes: B22F 1/102 Metallic powder coated with organic material
• CPC Class Codes: B22F 10/28 Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
• CPC Class Codes: B22F 10/36 of energy beam parameters
• CPC Class Codes: B22F 12/13 to preheat the material
• CPC Class Codes: B22F 2003/1052 assisted by energy absorption enhanced by the coating or powder
• CPC Class Codes: B22F 2998/00 Supplementary information concerning processes or compositions relating to powder metallurgy
• 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 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 70/00 Materials specially adapted for additive manufacturing
• CPC Class Codes: C04B 2235/5436 micrometer sized, i.e. from 1 to 100 micron
• CPC Class Codes: C04B 2235/665 Local sintering, e.g. laser sintering
• CPC Class Codes: C04B 35/6342 Polyvinylacetals, e.g. polyvinylbutyral [PVB]
• CPC Class Codes: C04B 35/63468 Polyamides
• CPC Class Codes: C04B 35/64 Burning or sintering processes C04B33/32 takes precedence ; powder metallurgy B22F
• CPC Class Codes: Y02P 10/25 Process efficiency
• CPC Class Codes: Y10T 428/24893 including particulate material
• CPC Class Codes: Y10T 428/2991 Coated

Abstract

In the rapid prototyping method of selective laser sintering, temperature gradients occur inside and between individual layers, leading to component deformation which is intolerable at least for high-quality components. The air of the invention is to provide a method for selective laser sintering, whereby the temperature inside the built-up particle cake is as homogeneous as possible. To this end, particles containing at least one material having a maximum softening temperature of approximately 70° C. are used.

Claims

1. A particle for use in selective laser sintering (SLS), including

a core (1) formed from at least one first material,

an at least partial coating (2) of the core (1) with a second material,

the second material having a lower softening point than the first material,

wherein the softening point of the second material is lower than approximately 70°

C.

2. The particle as claimed in claim 1, wherein the coating (2) contains a polymer, preferably a thermoplastic polymer.

3. The particle as claimed in claim 2, wherein the coating (2) contains a polyvinyl acetal, preferably a polyvinyl butyral.

4. The particle as claimed in claim 1, wherein the coating (2) is not hygroscopic, and is preferably hydrophobic.

5. The particle as claimed in claim 1, wherein the core (1) contains at least one element selected from the group of materials consisting of metal, ceramic, polymer.

6. The particle as claimed in claim 5, wherein the core 1 includes at least two parts selected from the group of materials consisting of metal, ceramic, and polymer, loosely or securely joined.

7. A process for producing a three-dimensional object by means of SLS, which includes the following steps:

application of a layer of particles to a target surface,

irradiation of a selected part of the layer, corresponding to a cross section of the object, using an energy beam, so that the particles are joined in the selected part,

repetition of the application and irradiation steps for a plurality of layers, so that the joined parts of the adjacent layers combine to form the object,

wherein

particles which contain at least one material whose softening point is lower than approximately 70°

C. are used.

8. The process as claimed in claim 7, wherein particles are used comprising

a core (1) formed from at least one first material,

an at least partial coating (2) of the core (1) with a second material,

the second material having a lower softening point than the first material,

wherein the softening point of the second material is lower than approximately 70°

C.

9. The process as claimed in claim 7, wherein at least the particle layer which is to be irradiated in each case is additionally heated prior to irradiation with the energy beam, preferably to a temperature level of approx. 2-3°

C. below the lowest softening point of the particle materials used.

11. The process as claimed in claim 7, wherein coating (2) contains a polymer, preferably a thermoplastic polymer.

12. The process as claimed in claim 11, wherein the coating (2) contains a polyvinyl acetal, preferably a polyvinyl butyral.

13. The process as claimed in claim 7, wherein the coating (2) is not hygroscopic, and is preferably hydrophobic.

14. The process as claimed in claim 7, wherein the core (1) contains at least one element selected from the group of materials consisting of metal, ceramic, polymer.

15. The process as claimed in claim 14, wherein, wherein the core 1 includes at least two parts selected from the group of materials consisting of metal, ceramic, and polymer, loosely or securely joined.

10. An object formed from joined particles, wherein the particles comprise

a core (1) formed from at least one first material,

an at least partial coating (2) of the core (1) with a second material,

the second material having a lower softening point than the first material,

wherein the softening point of the second material is lower than approximately 70°

C.,

and/or wherein the object is formed by a process which includes the following steps;

application of a layer of particles to a target surface,

irradiation of a selected part of the layer, corresponding to a cross section of the object, using an energy beam, so that the particles are joined in the selected part,

repetition of the application and irradiation steps for a plurality of layers, so that the joined parts of the adjacent layers combine to form the object,

wherein

particles which contain at least one material whose softening point is lower than approximately 70°

C. are used.