# US 11,298,880 B2 · Freezing method for cleaning an additive manufacturing part

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- Number: US 11,298,880 B2
- Document ID: US11298880B2
- Status: Granted
- Kind: B2
- Application number: 17/041,491
- Filed: 2019-03-26
- Published: 2021-05-06
- Granted: 2022-04-12
- Earliest claimed: 2018-03-27
- Assignees: Freemelt AB
- Applicants: Freemelt AB
- Inventors: Robin Stephansen
- Web page: https://patentgrep.com/patent/US11298880B2

## CPC

- B08B 3/12: by sonic or ultrasonic vibrations
- B08B 7/0092: {by cooling}
- B08B 9/00: Cleaning hollow articles by methods or apparatus specially adapted thereto
- B22F 3/24: After-treatment of workpieces or articles {(B22F3/1146 takes precedence)}
- B22F 5/10: of articles with cavities or holes, not otherwise provided for in the preceding subgroups
- B22F 10/68: Cleaning or washing
- B29C 64/35: Cleaning
- B29C 71/0009: {using liquids, e.g. solvents, swelling agents (spectacle cases, e.g. for cleaning contact lenses A45C11/04; disinfecting or sterilising contact lenses A61L12/00, using liquid substances A61L2/20; cleaning involving the use of liquid in general B08B3/00; for hydrating contact lenses B29D11/00067)}
- B33Y 40/20: Post-treatment, e.g. curing, coating or polishing
- B08B 9/027: Cleaning the internal surfaces; Removal of blockages
- B22F 10/28: Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
- B22F 2003/247: {Removing material: carving, cleaning, grinding, hobbing, honing, lapping, polishing, milling, shaving, skiving, turning the surface}
- B22F 2999/00: Aspects linked to processes or compositions used in powder metallurgy
- B29C 2071/0045: {Washing using non-reactive liquids}
- Y02P 10/25: Process efficiency
- B08B: CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
- B22F: WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER (making alloys by powder metallurgy C22C); APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00)
- B33Y: ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

The present invention relates to a method for removing powder from a component or part produced by a powder bed additive manufacturing system. The method comprises the steps; providing a part, the part having at least one internal cavity with at least one external opening, the at least one cavity being at least partly filled with powder grains, the powder grains being connected to each other and to the walls of the cavity by mechanical, frictional, electrical, physical or chemical forces; adding medium in liquid phase to the at least one cavity of the part, the liquid having the property that it expands in phase transition from liquid to solid phase; transforming added medium to solid phase to loosen and break up at least a fraction of the powder grains connections from each other; and removing powder from the at least one internal cavity.

## Claims

### Claim 1

A method comprising:
providing a part, said part having at least one internal cavity with at least one external opening, said at least one cavity being at least partly filled with powder grains, said powder grains being connected to each other;
adding medium in liquid phase to said at least one cavity, said liquid having the property that it expands in phase transition from liquid to solid phase, wherein said medium is saline water;
transforming the added medium to solid phase to break at least a fraction of said powder grain connections; and
removing powder from said at least one internal cavity.

### Claim 2 (depends on 1)

The method according to claim 1, further comprising transforming said medium from solid to liquid phase before removing powder from said at least one internal cavity.

### Claim 3 (depends on 1)

The method according to claim 1, further comprising removing said medium from the part before removing powder from said at least one internal cavity.

### Claim 4 (depends on 1)

A method according to claim 1, wherein removing powder from said at least one internal cavity comprises removing said medium together with said powder from said at least one internal cavity.

### Claim 5 (depends on 1)

The method according to claim 1, wherein said transformation of medium between liquid and solid phase is being cycled more than one cycle.

### Claim 6 (depends on 1)

The method according to claim 1, wherein said powder is metal powder.

### Claim 7 (depends on 1)

The method according to claim 1. wherein said powder grains are connected with bonds by sintering.

### Claim 8 (depends on 1)

The method according to claim 1, wherein said transformation from liquid to solid phase is performed by a temperature reduction.

### Claim 9 (depends on 1)

The method according to claim 1. wherein external pressure is applied to the cavity to facilitate removing the powder from the cavity.

### Claim 10 (depends on 1)

The method according to claim 1, wherein ultrasonic energy is applied to facilitate removing the powder from the cavity.

### Claim 11 (depends on 1)

The method according to claim 1, further comprising evacuating gas surrounding said powder in said at least one cavity before adding said medium.