Process for producing a shaped body by layerwise buildup from material powder

• US 9,713,856 B2
• Filed: 11/29/2012
• Issued: 07/25/2017
• Est. Priority Date: 11/29/2011
• Status: Active Grant

• Current Assignee: ReaLizer GmbH (Dmg Mori Co., Ltd.)
• Original Assignee: ReaLizer GmbH (Dmg Mori Co., Ltd.)
• Inventors: Fockele, Matthias
• Primary Examiner(s): KIM, CHRISTOPHER S
• Application Number:
  US14/361,156
• Publication Number:
  US 20140332507A1
• Time in Patent Office: 1,699 Days
• CPC Class Codes: B22F 10/28 Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
• CPC Class Codes: B22F 10/32 of the atmosphere, e.g. composition or pressure in a building chamber
• CPC Class Codes: B22F 10/36 of energy beam parameters
• CPC Class Codes: B22F 10/362 for preheating
• CPC Class Codes: B22F 12/30 Platforms or substrates
• CPC Class Codes: B22F 12/38 Housings, e.g. machine housings
• CPC Class Codes: B23K 26/32 taking account of the properties of the material involved
• CPC Class Codes: B23K 26/342 Build-up welding
• CPC Class Codes: B29C 64/153 using layers of powder being selectively joined, e.g. by selective laser sintering or melting
• CPC Class Codes: Y02P 10/25 Process efficiency

Abstract

The invention relates to a method for producing a molded body by building up layers of powdered material, comprising the steps of:

• a) preparing a layer of powdered material,
• b) heating the layer using controlled radiation by irradiating selected points of the layer according to a cross-sectional pattern of the molded body assigned to said layer according to the geometry description data of the molded body, so that the powdered material is solidified by melting to form connecting regions according to the cross-sectional pattern of the molded body,
• c) preparing a next layer of powdered material on the layer irradiated most recently and
• d) heating the most recently prepared layer using controlled radiation by radiating selective points of the layer according to a cross-sectional pattern of the molded body assigned to said layer, so that the powdered material is solidified by melting to form connecting regions according to said cross-sectional pattern of the molded body,
• and
• e) repeating steps c) and d) multiple times at least until the build-up of the molded body is complete, wherein the energy application to selected points in radiation steps d) can be varied per unit of time by performing the radiation according to the respective radiation point on the powdered layer.

Claims

1. Method for producing a moulded body by building up layers of powdered material, comprising the steps of:

a) preparing a layer (34) of powdered material,

b) heating the layer (34) using controlled radiation by irradiating selected points of the layer (34) according to a cross-sectional pattern of the moulded body (2) assigned to the layer (34) according to a geometry description data of the moulded body (2), so that the powdered material is solidified by melting to form connecting regions according to the cross-sectional pattern of the moulded body (2),

c) preparing a next layer of powdered material (34) on the layer irradiated most recently,

d) heating the most recently prepared layer (34) using controlled radiation by irradiating selected points of the most recently prepared layer (34) according to a cross-sectional pattern of the moulded body assigned to the most recently prepared layer, so that the powdered material is solidified by melting to form connecting regions according to said cross-sectional pattern of the moulded body (2),

e) repeating steps c) and d),

wherein an energy application to the irradiated selected points in step d) is varied per unit of time by a means of radiation according to a respective irradiation point on the most recently prepared layer (34),

wherein the energy application per unit of time to the respective irradiation point in step d) is selected as a function of a thermal conductivity of a respective defined, immediate, three-dimensional surrounding region (38) of the respective irradiation point and is modulated automatically by setting irradiation parameters,

wherein the irradiation parameters include an energy density of the radiation at the respective irradiation point, a duration of the irradiation at the respective irradiation point, or a combination thereof,

wherein the thermal conductivity of the defined, immediate, three-dimensional surrounding region of the respective irradiation point is measured by determining a volume of material already solidified by melting powdered material within the defined, immediate, three-dimensional surrounding region based on the geometry description data of the moulded body, and

wherein the energy application per unit of time to the respective irradiation point is selected to be greater as the thermal conductivity of the defined, immediate, three-dimensional surrounding region increases beyond a tolerance range.

2. Method according to claim 1, wherein the step of irradiating the selected points on a respective layer using controlled radiation is performed by a bundled laser beam (24), whereby a radiation power of the laser beam, an extent of a point of impact of the laser beam on the respective layer (34), a scanning speed of the laser beam at the respective irradiation point, or a combination thereof is adjusted based on a function of the thermal conductivity of the respective defined, immediate, three-dimensional surrounding region (38) of the respective irradiation point.

3. Method according to claim 1, wherein the measurement of the thermal conductivity of the defined, immediate, three-dimensional surrounding region of the respective irradiation point determined from the geometry description data of the moulded body used for automatically controlling the irradiation parameters is performed by a control apparatus (28).

4. Method according to claim 3, wherein the measurement of the thermal conductivity or values derived therefrom are saved in association with respective geometry description data of the respective irradiation points so that the measurement of the thermal conductivity or values derived therefrom can be read and processed by the control apparatus (28) in order to control the irradiation parameters.

5. Method according to claim 1, wherein the measurement for determining the thermal conductivity of the defined, immediate three-dimensional surrounding region of each respective irradiation point includes dividing each respective layer into a plurality of volume elements (40), wherein each volume element (40) includes a volume element height corresponding to the layer thickness (d), and the volume elements (40) are assigned to irradiation points so that each respective defined, immediate three-dimensional surrounding region and is defined by an assigned number of volume elements (40), and the measurement for determining the thermal conductivity of the defined immediate, three-dimensional surrounding region (38) includes accounting for a number of volume elements of material already solidified by melting powdered material.

6. Method according to claim 5, wherein the number of volume elements of material already solidified by melting powdered material in the defined, three-dimensional immediate surrounding region (38) of the respective irradiation point includes volume elements in layers below the layer (34) of the respective irradiation point.

7. Method according to claim 6, wherein the number of volume elements of material already solidified by melting powdered material in the defined, immediate three-dimensional surrounding region (38) of the respective irradiation point includes volume elements in the layer of the respective irradiation point.

8. Method according to claim 1, further includes assigning an irradiation parameter set to each irradiation point, wherein each irradiation set includes irradiation parameters depending on the thermal conductivity of the defined immediate, three-dimensional surrounding region of the respective irradiation point, and the irradiation parameter sets are saved in association with geometry description data of said irradiation points, so that the irradiation parameter sets are read and processed by the control apparatus (28) to control the irradiation processes.

9. Method according to claim 1, wherein the selection of the irradiation points during the irradiation of a respective layer (34) is based on the measurement of the thermal conductivity of the defined, three-dimensional, immediate surrounding regions determined from the geometry description data.

10. A device for performing the method according to claim 1, comprising

a processing chamber housing (8) with a support platform (14) for supporting the moulded body to be produced,

a layer preparation apparatus (16) for preparing respective powdered layers on the support platform (14),

an irradiation apparatus (18) for irradiating the most recently prepared layer on the support platform (14) according to the geometry description data of the moulded body to be produced, and

a control apparatus (28) for controlling the irradiation apparatus (18),

wherein the control apparatus is configured to control the irradiation apparatus by setting the irradiation parameters so that the application of energy to the selected points per unit of time is performed on the respective irradiation point on the respective layer (34) as a function of the thermal conductivity of the respective defined, three-dimensional, immediate surrounding region (38) of the respective irradiation point, and the thermal conductivity is determined from the geometry description data of the moulded body to be produced.

11. Device according to claim 10, wherein the irradiation apparatus (18) comprises a laser (20) and a beam deflecting unit (22) for controlling the deflection of a laser beam (24) emitted by the laser.