Method for enhancing the finish of additively-manufactured components

Abstract

Discloses are a method and apparatus for the additive manufacture of components by applying layers of powder material on a substrate or a previously produced part of a component and at least partial fusing of the powder material in the powder layer in line with the component cross-section contour along the powder layer and to an underlying solid material of the component or substrate for the purpose of building up several solid layers one on top of the other. Following fusion of the powder material the solid layer just generated is cleaned of powder material and, prior to deposition of the next solid layer, the edge of the solid layer is post-processed by softening the fusion-bonded material.

Claims

1. A method for the additive manufacturing of a component, wherein the method comprises applying layers of powder material on a substrate or a previously produced part of a component and at least partial fusing of the powder material in a powder layer in line with a component cross-section contour along the powder layer and to an underlying solid material of the component or substrate for the purpose of building up several solid layers disposed one on top of the other, and wherein after producing a solid layer by fusion of the powder material and subsequent solidification, the solid layer just generated is cleaned of powder material and then, prior to deposition of a next solid layer, an edge of the solid layer is post-processed by heating the edge of the solid layer so that only material at the edge is at least one of softened and remelted and thereafter solidified again.

2. The method of claim 1, wherein cleaning of the solid layer of powder material is carried out after every deposition of a solid layer.

3. The method of claim 1, wherein the cleaning of a solid layer comprises removal of powder material from one or more solid layers deposited prior to a most recently applied solid layer.

4. The method of claim 1, wherein cleaning of the solid layer is carried out by at least one method selected from mechanical removal of powder material, brushing, wiping, vacuuming, cleaning by spraying with a fluid, blowing off with compressed air or other gases, raising from a surrounding powder bed and lowering of a powder bed.

5. The method of claim 1, wherein fusing of the powder material is carried out by employing an energy beam.

6. The method of claim 5, wherein fusing of the powder material is carried out by at least one of selective laser melting or sintering and selective electron beam melting or sintering.

7. The method of claim 1, wherein post-processing of the edge of a solid layer is carried out several times prior to deposition of a next solid layer.

8. The method of claim 1, wherein heating of the edge of the solid layer results in softening and/or melting the edge of the solid layer and is carried out by using an energy beam.

9. The method of claim 8, wherein the energy beam comprises at least one of a laser beam and an electron beam.

10. The method of claim 8, wherein softening and/or melting of the edge of the solid layer is effected with from 60% to 90% of that power of the energy beam with which fusing of the powder material occurs during deposition of a solid layer.

11. The method of claim 8, wherein softening and/or melting of the edge of the solid layer is effected with from 70% to 80% of that power of the energy beam with which fusing of the powder material occurs during deposition of a solid layer.

12. The method of claim 8, wherein softening and/or melting of the edge of the solid layer takes place at from 20% to 50% of that feed rate of the energy beam at which the energy beam for fusing the powder material is moved during deposition of a solid layer.

13. The method of claim 8, wherein softening and/or melting of the edge of the solid layer takes place at from 30% to 40% of that feed rate of the energy beam at which the energy beam for fusing the powder material is moved during deposition of a solid layer.

14. The method of claim 10, wherein softening and/or melting of the edge of the solid layer takes place at from 20% to 50% of that feed rate of the energy beam at which the energy beam for fusing the powder material is moved during deposition of a solid layer.

15. The method of claim 11, wherein softening and/or melting of the edge of the solid layer takes place at from 30% to 40% of that feed rate of the energy beam at which the energy beam for fusing the powder material is moved during deposition of a solid layer.

16. The method of claim 1, wherein an energy beam for post-processing by heating stems from the same radiation source as an energy beam for fusing the powder material.

17. The method of claim 16, wherein the energy beams for the post-processing and fusion are generated differently and/or are influenced or shaped differently.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The attached drawings show here in purely schematic form in

(2) FIG. 1 a schematic representation of an embodiment of an inventive apparatus for the additive manufacture of components as illustrated by the example of selective laser melting,

(3) FIG. 2 a description of the processing sequence as per an embodiment of the inventive method and in

(4) FIG. 3 a plan view of a powder bed and a produced solid layer.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

(5) The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description in combination with the drawings making apparent to those of skill in the art how the several forms of the present invention may be embodied in practice.

(6) FIG. 1 shows a purely schematic illustration of an apparatus 1 of the kind which can be used, for example, to additively manufacture a component by means of selective laser melting. The apparatus 1 comprises a lifting table 2, on the platform of which is disposed a semi-finished product 3 (part of a component) on which material is deposited in layers to create a three-dimensional component. For this purpose, powder 10, which is located in a powder reservoir above a lifting table 9, is pushed by means of a slider 8 in layers over the semi-finished product 3 and is melted with the laser beam 13 of a laser 4 such that it bonds to the existing semi-finished product 3. The bonding of the powder material in a layer of powder to the semi-finished product 3 is carried out by the laser 4 in accordance with the desired contour of the component to be produced, such that any desired three-dimensional shapes can be generated. Accordingly, the laser beam 13 is guided over the powder bed 12 in order that, through various points of contact on the powder bed in accordance with the contour of the three-dimensional component in the cross-sectional plane corresponding to the layer to be produced, it may melt powder material and bond it to the previously generated part of a component or a substrate provided initially. In this regard, the laser beam 13 can be guided over the surface of the powder bed 12 by a suitable deflection unit and/or the powder bed can be moved relative to the laser beam 13.

(7) In order that undesirable reactions with the ambient atmosphere during melting or sintering may be prevented, the process can take place in a sealed space provided by a housing 11 of the apparatus 1, and additionally an inert gas atmosphere can be provided, for example, to prevent oxidation of the powder material and the like during deposition. Nitrogen can serve as an example of the inert gas used, which can be supplied via a gas supply that is not shown.

(8) Instead of the inert gas, another process gas could also be used if, for example, reactive deposition of the powder material is required.

(9) In addition, other types of radiation are also conceivable, such as electron beams or other particle beams or light beams which are used in stereolithography.

(10) Slider 8 is designed as a combined levelling and smoothing slider for smoothing the powder layer on the semi-finished product 3 and adjusting it to a certain layer thickness. However, it is also conceivable for the slider 8 merely to provide a rough quantity of the powder material and for an additional levelling and smoothing slider (not shown) to be used.

(11) The levelling and smoothing slider 8 is used to set the required thickness D of the powder layer 5 precisely, as shown in the detailed view of FIG. 1, and moreover to ensure that the powder bed surface 6 of the powder layer 5 is smooth and level, as otherwise inaccuracies and irregularities might arise in the generated component.

(12) The apparatus 1 also comprises a cleaning apparatus in the form of a brush 7, which is used to clean the most recently deposited solid layer and the previously generated component 3 prior to post-processing of the edge of the solid layer. After the powder layer 5 or the powder material contained therein has been melted with the laser beam 13 of the laser 4 in line with the shape of the component to be produced in the cross-section along the powder layer 5 and after solidification of the molten powder material to a solid layer 14 (as shown in illustrations 15 and 16 in FIG. 2), the cleaning apparatus in the form of a brush 7 is used to remove powder material from the solid layer 14 as well as from parts of the component generated previously. For this purpose, the component 3 is raised by the lifting table 2 such that at least the most recently generated solid layer 14, and preferably several, for example 5 to 20, of the most recently generated solid layers, of the component 3 protrude(s) from the powder bed 12, such that the brush 7 can be moved, as indicated by the arrow in FIG. 1, over the previously produced component 3 in order that the most recently generated solid layer and parts of the component 3 may be cleaned of loose powder material by the movement relative to the component 3.

(13) Illustrations 15 to 20 in FIG. 2 show the process steps in detail. In process step 1 as shown in illustration 15, the powder material of a powder layer not shown in more detail in FIG. 2 is melted partially by the laser beam 13 of the laser 4 in accordance with the shape of the component 3 to be produced and forms after solidification a solid layer 14 in accordance with the cross-sectional plane of the component 3 to be produced. In the second process step, as shown in illustration 16, the component 3, together with the solid layer 14 produced on it, is raised from the powder bed 12, such that the most recently generated solid layer 14 and preferably other previously generated solid layers of the component 3 protrude(s) from the powder bed. In the third process step of illustration 17, the brush 7, which can for example be a brush of the kind disclosed in DE 10 2013 223 587A1, is then guided over that part of the component 3 which was previously produced and which protrudes from the powder bed 12, in order that the most recently generated solid layer 14 and adjacent parts of the component 3 which were previously generated may be freed of the powder material. The cleaning step can be repeated several times in succession, so that the brush can be moved back and forth several times to remove loose powder material.

(14) When the cleaning step as shown in illustration 17 is complete, the edge of the solid layer 14 is post-processed by re-melting of the edge with the laser beam 13 of the laser 4, such that the edge area and thus the surface of the component 3 to be produced can be smoothed. This is illustrated in FIG. 3, which shows a plan view of a powder bed 12, wherein the melting and re-solidification of the powder material have created a solid layer 14 which comprises a peripheral outer edge 21 and an inner edge 22 for bounding an inner cavity 23. The post-processing of the edge 21, 22 of the solid layer 14 is performed both along the outer edge and along the inner edge 21, which bounds the cavity 23.

(15) After post-processing of the edge 21, 22 of the most recently applied solid layer 14, the lifting table 2 with the component 3 disposed on it is lowered back into the powder bed 12 (5th process step as per illustration 19) and, as per process step 6 in accordance with illustration 20, a new powder layer 5 is applied by means of the slider 8, such that deposition of a new solid layer 14 can commence with process step 1 as per illustration 15. As shown in the arrows between the illustrations 15 to 20, the process steps 1 to 6 can be repeated over and over for the purpose of depositing a plurality of solid layers 14 until the component to be manufactured is finished.

(16) In the embodiments shown here, two different apparatuses are provided, one for cleaning the most recently deposited solid layer and further parts of the previously generated component 3 and the other for applying a powder layer. However, the cleaning apparatus or parts of it and the apparatus for applying a powder layer, i.e. the brush 7 and the slider 8, can be integrated within a single apparatus, such that one brush or levelling and smoothing slider can be used both for applying a powder layer and for cleaning the previously generated component prior to post-processing of the edge contour.

(17) Although the present invention has been described in detail with reference to the embodiments, it is self-evident to the person skilled in the art that the invention is not limited to these embodiments, but rather that modifications involving the omission of individual characteristics are possible, or that other types of combinations of characteristics can be made without departing from the scope of the appended claims. The present disclosure comprises all combinations of the presented individual characteristics.

LIST OF REFERENCE NUMERALS

(18) 1 Apparatus 2 Lifting table 3 Semi-finished product 4 Laser 5 Powder bed 6 Powder bed surface 7 Brush 8 Slider 9 Lifting table 10 Powder 11 Housing 12 Powder bed 13 Laser beam 14 Solid layer 15 Process step 1 16 Process step 2 17 Process step 3 18 Process step 4 19 Process step 5 20 Process step 6 21 Edge of the solid layer 22 Edge of the solid layer 23 Cavity