GB2586972A

GB2586972A - A method for making an article by additive manufacturing

Info

Publication number: GB2586972A
Application number: GB1912852.9A
Authority: GB
Inventors: David Monnington Brancher Carl
Original assignee: Mat Solutions Ltd; Materials Solutions Ltd
Current assignee: Mat Solutions Ltd; Materials Solutions Ltd
Priority date: 2019-09-06
Filing date: 2019-09-06
Publication date: 2021-03-17
Also published as: GB201912852D0

Abstract

A method of making an article 1 by simultaneously building the article 1 and an electrode 9 which extends along a passage 8 within the article 1 by additive manufacturing using an electrically conductive material, supplying an electrically conductive fluid in the passage 8 and passing an electric current between the electrode 9 and a wall of the passage 8, thereby removing lose particles from the passage walls, smoothing the passage walls or coating the passage walls. (I.e. electrochemical etching, anodisaton and electrical discharge machining). Supports 10 which space the electrode 9 from the passage walls 22 are formed at the same time as the article 1 and electrode 9 and are removed before application of the current. Insulators can be used to hold the electrode 9 in place while the current is applied.

Description

A method for making an article by additive manufacturing The present invention relates to a method for making an article by additive manufacturing.

One known method for making an article by additive manufacturing, will now be described with reference to Fig 1 of the accompanying drawings.

The method is practiced in a build chamber 20 comprising a base 7 and walls 6, wherein the base 7 can be raised or lowered relative to the walls 6.

The method proceeds as follows. The base 7 is raised relative to the walls 6, and a first layer of powdered metal or metal alloy 4 (e.g. titanium) is then deposited on the base 7. A laser (not shown) melts an area 2a of the first layer of powder 4, which area 2a corresponds to a first layer 2a of an article 1 to be produced. The base 7 is lowered a little, and a second layer of powder 4 is deposited on the first layer of powder 4, both on the melted 2a and un-melted areas of the first layer of powder 4. The laser melts an area 2b of the second layer of powder 4, which area 2b corresponds to a second layer 2b of the article 1. In addition, the laser re-melts at least an upper portion of the first layer 2a of the article 1, so that the first and second layers 2a, 2b of the article 1 are contiguous. The base 7 is lowered a little again, and a third layer of powder 4 is deposited on the second layer of powder 4, both on the melted 2b and un-melted areas of the second layer of powder 4. The laser melts an area 2c of the third layer of powder 4, which area 2c corresponds to a third layer 2c of the article 1. In addition, the laser remelts at least an upper portion of the second layer 2b of the article 1, so that the second and third layers 2b, 2c of the article 1 are contiguous. The method continues in corresponding manner for all remaining layers 2d-2i of the article 1. Thus, the method builds-up on a layer-by-layer basis the article 1.

The right-hand-sides of layers 2a-2e of the article 1 end at the same point, but the right-hand-sides of layers 2f-2i end progressively further to the right. This results in sharp edges in the region 3 of the surface of the article 1. These sharp edges require removal to provide the finished article 1.

The article 1 is surrounded by a bed 5 of powder 4, which powder bed 5 is retained by the base 7 and the walls 6 of the build chamber 20. The regions of the surface of the article 1 which interface the powder bed 5 will have attached thereto sintered powder 4. Examples of such attachment are referenced 4a in Fig 1. Sintered powder 4 attached to the surface of the article 1 requires removal to provide the finished article 1.

A manifold containing internal passageways is an example of an article suitably made by the above known method. The internal passageways are formed by internal walls of the manifold. The method gives rise to these internal walls having sharp edges and attached sintered powder. A known general method for removing the sharp edges and sintered powder is as follows. The method is carried out following removal of the manifold from the build chamber.

In the method, an electrode, a so-called counter electrode, is inserted into the manifold so as to extend along the internal passageways. A fluid capable of passing an electric current is then supplied to the internal passageways. Examples of such a fluid are an electrolytic fluid, e.g. sulphuric acid, and a dielectric fluid. An electric current is then passed, via the fluid, between the counter electrode and the internal walls of the manifold forming the internal passageways.

The method can be used to remove sharp edges and sintered powder from the internal walls. The method can also be used to apply a coating to the internal walls. Examples of the method are electrochemical etching (in which the fluid is an electrolytic fluid), anodisation (in which the fluid is also an electrolytic fluid), and electrical discharge machining polishing (in which the fluid is a dielectric fluid).

A problem encountered in the method can be the insertion of the counter electrode into the manifold so as to extend along the internal passageways. The configuration or geometry of the internal passageways may be such that it is difficult or impossible to carry out this insertion, e.g. due to a change in direction of an internal passageway or an internal passageway dividing into two internal passageways. In other words, the complexity of the paths taken by the internal passageways may make difficult or deny the insertion. The present invention solves this problem.

According to the present invention there is provided a method for making an article by additive manufacturing, comprising the steps of: building-up on a layer-by-layer basis an article, wherein the article includes one or more internal passageways therein formed by internal walls of the article, wherein the article is electrically conductive; simultaneously with the step of building-up an article, building-up on a layer-by-layer basis an electrode which extends along the internal passageway(s); supplying to the internal passageway(s) a fluid capable of passing an electric current; and passing an electric current between the electrode and the internal walls via the fluid, to surface modify the internal walls.

The method may further comprise the step of, following the step of passing an electric current, removing the electrode from the internal passageway(s).

The method may further comprise the steps of: simultaneously with the steps of building-up an article and building-up an electrode, building-up on a layer-by-layer basis one or more supports which support the electrode in position during the steps of building-up an article and building-up an electrode, the one or more supports extending between the electrode and the internal walls; and removing the one or more supports prior to the step of passing an electric current.

The surface modification of the internal walls may comprise: removing unwanted particles from the internal walls, or smoothing the internal walls by removing sharp edges from the internal walls, or applying a coating to the internal walls.

The building-up on a layer-by-layer basis may comprise depositing layers of particulate metal or metal alloy, and selectively heating those areas of each deposited layer 30 where it is required building-up take place.

The particulate metal or metal alloy may comprise powdered metal or metal alloy, and the selective heating may be performed by laser.

The building-up on a layer-by-layer basis may be performed within a build chamber having a base and walls, and the base may move downward relative to the walls as the layer-by5 layer building-up occurs.

The one or more internal passageways may comprise a first internal passageway and two or more second internal passageways, the first internal passageway dividing into the 10 two or more second internal passageways.

During the step of passing an electric current, the electrode may be held in position in the internal passageway(s) using one or more parts that are electrically insulative.

The removal of the electrode from the internal passageway(s) may require the electrode to be broken into two or more parts due to the configuration of the internal passageway(s).

The article and the electrode may require to be built-up simultaneously because the configuration of the internal passageway(s) denies first building-up the article and then 25 placing in the internal passageway(s) the electrode.

The simultaneous building-up on a layer-by-layer basis of the article and the electrode may comprise laying down layers wherein one area of the layer contributes to forming the article and another area of the same layer contributes to forming the electrode.

The simultaneous building-up on a layer-by-layer basis of the article, the electrode, and the one or more supports, may comprise laying down layers wherein one area of the layer contributes to forming the article, another area of the same layer contributes to forming the electrode, and yet another area of the same layer contributes to forming the one or more supports.

The method may further comprise the step of, over the course of the simultaneous building-up on a layer-by-layer basis of the article and the electrode, regularly verifying that the electrode is in the required position relative to the internal walls.

The regularly verifying may comprise verifying following the laying down of each layer of the article and the electrode 15 that the electrode is in the required position relative to the internal walls.

The present invention will now be described, by way of example, with reference to the accompanying drawings, in 20 which: Fig 1, already referred to, illustrates in cross-section a build chamber and an article in the build chamber built-up on a layer-by-layer basis; Fig 2 illustrates in cross-section an article disposed on a base of a build chamber, the article containing internal passageways which together form an inverted Y configuration, a counter electrode extending along the internal passageways; Figs 3a and 3b illustrate respectively in cross-section and in plan view the use of three supports to support in an internal passageway one end of a counter electrode; and Fig 4 corresponds to Fig 3b but has the three supports removed.

The known method for making an article by additive manufacturing described above with reference to Fig 1, is modified as follows.

Referring to Fig 2, the article 1 to be made contains three straight internal passageways 8 which together form an inverted Y configuration. The internal passageways 3 are formed by internal walls 22 of the article 1. A base 7 of a build chamber is shown in Fig 2. The article 1 is built-up on a layer-by-layer basis in the same manner as the article 1 of Fig 1. Simultaneously with the building-up of the article 1, also built-up on a layer-by-layer basis is a counter electrode 9 which extends along the internal passageways 8. The counter electrode 9 comprises three straight legs 21 which together form an inverted Y configuration. Each straight leg 21 extends along the centre of a respective one of the three straight internal passageways 8. In the simultaneous building-up of the article 1 and the counter electrode 9, layers are laid down wherein one area of the layer contributes to forming the article 1 and another area of the same layer contributes to forming the counter electrode 9.

Following the simultaneous building-up on a layer-by-layer basis of the article 1 and the counter electrode 9, sharp edges will be present on the internal walls 22, as will sintered powder 4 attached to the internal walls 22. In this regard, a part of the powder bed 5 surrounding the article 1 following the building-up of the article 1 and the counter electrode 9, is present in the internal passageways 8, between the counter electrode 9 and the internal walls 22. The sharp edges and sintered powder 4 are removed as follows. Following the removal of the article 1 with its associated counter electrode 9 from the build chamber, a

B

fluid capable of passing an electric current, e.g. an electrolytic fluid or a dielectric fluid, is supplied to the internal passageways 8 so as to occupy the space between the counter electrode 9 and the internal walls 22. An electric current is then passed, via the fluid, between the counter electrode 9 and the internal walls 22.

Finally, the counter electrode 9 is removed to provide the finished article 1. This is suitably done by breaking the counter electrode 9 at the point at which its three straight legs 21 meet, to provide three straight sections for removal. It may be that the intended use of the finished article 1, including operation of its internal passageways 8, does not require the counter electrode 9 to be removed, in which case it need not be removed.

It will be seen that it would not have been possible first to build-up the article 1 and then to insert into the built-up article 1 so as to extend along the passageways 8 the counter electrode 9. This approach is denied by the inverted Y configuration formed by the three straight internal passageways 8. This is the approach of the prior art. In general, the present invention enables internal passageway(s) to have a configuration that does not permit the insertion of a counter electrode in the built article.

A further advantage over the prior art is that it is possible regularly to verify over the course of the simultaneous building-up on a layer-by-layer basis of the article 1 and the counter electrode 9, that the counter electrode 9 is in the required position relative to the internal walls 22. This is not possible with the approach of the prior art wherein the positioning of the counter electrode relative to the article being made only occurs following completion of the building-up on a layer-by-layer basis of the article. The regular verification may be verification following the laying down of each layer of the article 1 and the counter electrode 9.

It may be that the counter electrode 9 requires supporting in position relative to the internal walls 22 during the simultaneous building-up on a layer-by-layer basis of the article 1 and the counter electrode 9. Figs 3a and 3b show an example of such support. One end of a counter electrode 9 is supported in an internal passageway 8 by three supports 10 evenly distributed about the counter electrode 9 which extend between the counter electrode 9 and the internal walls 22 of the internal passageway B. The supports 10 are constructed at the same time and in the same manner as the article 1 and the counter electrode 9. Thus, simultaneously with the building-up on a layer-by-layer basis of the article 1 and the counter electrode 9, also built-up on a layer-by-layer basis are the supports 10. In the simultaneous building-up of the article 1, the counter electrode 9, and the supports 10, layers are laid down wherein one area of the layer contributes to forming the article 1, another area of the same layer contributes to forming the counter electrode 9, and yet another area of the same layer contributes to forming the supports 10.

The supports 10 must be removed prior to the passing of an electric current between the counter electrode 9 and the internal walls 22, via a fluid present in the internal passageway B. Fig 4 shows the three supports 10 removed, and a fluid 11 present in the internal passageway B. One or more parts (not shown) that are electrically insulative may be used during the passing of the electric current via the fluid 11, to hold the counter electrode 9 in position in the 1C) internal passageway 8.

Examples of electrically conductive materials that may comprise the article 1, the counter electrode 9, and, if used, the supports 10, are as follows: titanium, aluminium, an aluminium alloy, an iron alloy, a nickel alloy.

Claims

CLAIMS: 1. A method for making an article by additive manufacturing, comprising the steps of: building-up on a layer-by-layer basis an article, Wherein the article includes one or more internal passageways therein formed by internal walls of the article, wherein the article is electrically conductive; simultaneously with the step of building-up an article, 10 building-up on a layer-by-layer basis an electrode which extends along the internal passageway(s); supplying to the internal passageway(s) a fluid capable of passing an electric current; and passing an electric current between the electrode and 15 the internal walls via the fluid, to surface modify the internal walls.
2. A method according to claim 1, further comprising the step of, following the step of passing an electric current, 20 removing the electrode from the internal passageway(s).
3. A method according to claim 1 or claim 2, furtner comprising the steps of: simultaneously with the steps of building-up an article and building-up an electrode, building-up on a layer-bylayer basis one or more supports which support the electrode in position during the steps of building-up an article and building-up an electrode, the one or more supports extending between the electrode and the internal walls; and removing the one or more supports prior to the step of passing an electric current.
4. A method according to claim 1 or claim 2 or claim 3, wherein the surface modification of the internal walls comprises: removing unwanted particles from the internal walls, or smoothing the internal walls by removing sharp edges from the internal walls, or applying a coating to the internal walls.
5. A method according to any one of the preceding claims, wherein the building-up on a layer-by-layer basis comprises depositing layers of particulate metal or metal alloy, and selectively heating those areas of each deposited layer where it is required building-up take place.
6. A method according to claim 5, wherein the particulate metal or metal alloy comprises powdered metal or metal alloy, and the selective heating is performed by laser. 15
7. A method according to any one of the preceding claims, wherein the building-up on a layer-by-layer basis is performed within a build chamber having a base and walls, and the base moves downward relative to the walls as the layer-by-layer building-up occurs.
8. A method according to any one of the preceding claims, wherein the one or more internal passageways comprises a first internal passageway and two or more second internal passageways, the first internal passageway dividing into the two or more second internal passageways.
9. A method according to any one of the preceding claims, wherein, during the step of passing an electric current, the 30 electrode is held in position in the internal passageway(s) using one or more parts that are electrically insulative.
10. A method according to claim 2, wherein the removal of the electrode from the internal passageway(s) requires the electrode to be broken into two or more parts due to the configuration of the internal passageway(s).
11. A method according to any one of the preceding claims, wherein the article and the electrode require to be built-up simultaneously because the configuration of the internal passageway(s) denies first building-up the article and then placing in the internal passageway(s) the electrode.
12. A method according to any one of the preceding claims, wherein the simultaneous building-up on a layer-by-layer basis of the article and the electrode comprises laying down layers wherein one area of the layer contributes to forming the article and another area of the same layer contributes to forming the electrode.
13. A method according to claim 3, wherein the simultaneous building-up on a layer-by-layer basis of the article, the electrode, and the one or more supports, comprises laying down layers wherein one area of the layer contributes to forming the article, another area of the same layer contributes to forming the electrode, and yet another area of the same layer contributes to forming the one or more supports.
14. A method according to any one of the preceding claims, further comprising the step of, over the course of the simultaneous building-up on a layer-by-layer basis of the article and the electrode, regularly verifying that the electrode is in the required position relative to the internal walls.
15. A method according to claim 14, wherein the regularly verifying comprises verifying following the laying down of each layer of the article and the electrode that the electrode is in the required position relative to the internal walls.