GB2562467A

GB2562467A - Chemical milling

Info

Publication number: GB2562467A
Application number: GB1707321.4A
Authority: GB
Inventors: PEDERSEN Mikkel; Parimi Lakshmi; Dee Luke
Original assignee: GKN Aerospace Services Ltd
Current assignee: GKN Aerospace Services Ltd
Priority date: 2017-05-08
Filing date: 2017-05-08
Publication date: 2018-11-21
Anticipated expiration: 2037-05-08
Also published as: GB2562467B; GB201707321D0

Abstract

An additive manufacturing component and method, e.g. using electron beam or laser beam melting, where a component, e.g. of layers 6, is built up with support elements or members incorporated into the build of the component, using either or both chemical milling to disconnect the support portions and/or where at least one support member has a hollow conduit (fig 6) e.g. to communicate and direct a liquid to an outlet proximal to the connection. Preferably the supports are narrower 5, e.g. triangular 3 or pyramidal, e.g. with truncated apex 4, towards the connections for easier disconnection. The support members may be 5 mm or less, and perforations may be included. A base plate may be used. The erosion agent may be suitably selected e.g. a liquid e.g. nitric acid e.g. with hydrofluoric acid; or with sulphuric and hydrochloric acid e.g. for a bath. Acids may be sequentially selected. An additional thickness may be built into the outer surfaces of the component e.g. to be sacrificed, e.g. according to the duration of etching. Titanium powder may be used for the building. The designs aim to optimise separation.

Description

(71) Applicant(s):

GKN Aerospace Services Limited

National Composites Centre, Feynman Way, Bristol and Bath Science Park, EMERSONS GREEN, Bristol, BS16 7FS, United Kingdom (72) Inventor(s):

Mikkel Pedersen

Lakshmi Parimi

Luke Dee (74) Agent and/or Address for Service:

D Young & Co LLP

120 Holborn, LONDON, EC1N 2DY, United Kingdom (56) Documents Cited:

EP 1683593 A2 WO 2017/029276 A1

WO 1990/003893 A1 US 20150197862 A1

US 20110256416 A1 US 20100193998 A1 (58) Field of Search:

INT CL B22F

Other: Online: WPI, EPODOC, PATENT FULLTEXT (54) Title of the Invention: Chemical milling

Abstract Title: Separating additive manufacturing supports by optimally eroding the connections to a component (57) An additive manufacturing component and method, e.g. using electron beam or laser beam melting, where a component, e.g. of layers 6, is built up with support elements or members incorporated into the build of the component, using either or both chemical milling to disconnect the support portions and/or where at least one support member has a hollow conduit (fig 6) e.g. to communicate and direct a liquid to an outlet proximal to the connection. Preferably the supports are narrower 5, e.g. triangular 3 or pyramidal, e.g. with truncated apex 4, towards the connections for easier disconnection. The support members may be 5 mm or less, and perforations may be included. A base plate may be used. The erosion agent may be suitably selected e.g. a liquid e.g. nitric acid e.g. with hydrofluoric acid; or with sulphuric and hydrochloric acid e.g. for a bath. Acids may be sequentially selected. An additional thickness may be built into the outer surfaces of the component e.g. to be sacrificed, e.g. according to the duration of etching. Titanium powder may be used for the building. The designs aim to optimise separation.

At least one drawing originally filed was informal and the print reproduced here is taken from a later filed formal copy.

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FIG. 1

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FIG. 2

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FIG. 3

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FIG. 4B

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FIG. 5B

FIG. 5C

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FIG. 6

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FIG. 7A

FIG. 7B

Chemical Milling

Background

The present invention is concerned with an improved and alternative approach to finishing components manufactured using additive manufacturing techniques (AM).

Additive manufacturing technologies involve ‘printing’ layers of material to form three dimensional components. An example technique is electron beam melting (EBM) in which a metal powder is selectively melted using an electron beam to lay down layers of the desired component. A plurality of layers can be laid down to form the component.

In complex components, for example components with internal geometries/structures, it is often necessary to ‘print’ supporting members such as columns as part of the AM process. This allows the component to be supported as it is formed. Figure 1 illustrates the final shape of the desired component (reference A) and a plurality of support columns B1 to B5. The support columns B1 to B5 are printed during the EBM process and allow the sides and upper surface of the component to be supported as each progressive layer is printed.

The support columns are sacrificial in the sense that on completion of the component the support columns are removed leaving the final component A. Conventionally the component A is separated from the support columns either by machining the columns away from the lower side of the component or by applying a force to each of regions C1 to C5 to break the connection between the support column and the component.

Applying a force to the joint between the support column and the component is generally the preferred approach in the art because of its simplicity and speed. Furthermore it can be achieved using a hammer and chisel or bespoke tool.

However, this approach does have its limitations in terms of safety where shrapnel (that is sharp debris from the break point) can injure the machinist. It is also time consuming and labour intensive and potentially dangerous. In spite of these drawbacks it still remains the conventional approach to removing support columns in AM manufacturing.

AM techniques are generating ever more complex components and geometries and creating and removing the support structures further increases the complexity of AM manufacturing as well as cost in terms of labour. Furthermore, for some geometries it is not possible to remove the support structure from inside the component.

The present inventors have identified an alternative approach to forming support structures in

AM manufacturing techniques that not only addresses the issues discussed above but allows for components with improved surface finishes thereby further reducing the need to machine 5 AM components. This, amongst other advantages, greatly improves the cost effectiveness of

AM technologies as well as component integrity.

Although the EBM AM technique has been used as an example above the reader will understand that the invention can advantageously be applied to any AM technique where 10 support structures are used.

Summary of the Invention

Aspects of the invention are set out in the accompanying claims.

Viewed from a first aspect there is provided a method of manufacturing a component using an additive manufacturing process, wherein the component is built up of a plurality of layers and wherein support portions are incorporated into the build of the component during the additive manufacturing process to support portions of the component during the build, said method further comprising the step of disconnecting the support portions from the component by chemical erosion.

The term ‘chemical erosion’ is intended to refer to the step of using an acid or the like to dissolve part of the structure to the extent that the connection is broken allowing the support portions or elements to be removed from the component leaving the net component shape that is desired.

The step of erosion may be achieved in a range of ways. For example an erosion liquid or agent may be sprayed onto the relevant parts of the built component (and support portions) to cause the two to be separable. Advantageously the component may be positioned in a receptacle such as a tank or bath containing the erosion agent such as an acid. The entire component can then be submerged in the acid for a predetermined length of time. Furthermore, submerging the entire component also allows for the surface finish of the component to be improved by removal of any unwanted scratches of burrs on the surface of the component.

It is common for additive manufacturing to incorporate supporting members to allow for complex components to be built. An example is shown in figure 1. Because the components are built as a plurality of sequential layers (one on top of the other) it is often necessary to support parts of the components which are higher up in the build if they extend over voids in the component beneath the given layer.

These support members are conventionally removed using either machining such as milling or grinding. The most common technique is to manually remove the supports by breaking them from the component using a chisel and hammer. This can be effective in removing the supports but, as discussed above, it can result in component damage, danger to the operative and high labour costs.

The present invention uses a different approach to chemically de-couple the supports from the component without excessive manual intervention. It also provides additional advantages as discussed further below.

As discussed above the support portions provide structural support to parts of the components that would otherwise potentially collapse or sink into the powder bed of the additive manufacturing machine. Additive manufacturing (AM) techniques using metal powder technology will be well understood by a person skilled in the art and will not therefore be described in detail. In the present invention the support portions may provide the support to the component either by extending to the base plate of the AM machine and/or to adjacent portions of the component which can themselves provide the desired support. Furthermore, a ‘floating support’ can also be used (for example using EBM) where surrounding powder is used to support parts without extending to the baseplate.

The point at which the support portion connects with the component may advantageously be thinned i.e. having a smaller cross-sectional area than the rest of the support and in particular the part of the support immediately adjacent to the component. By thinning the support in this way the erosion time can be reduced and thus the time needed to de-couple the supports and component can also be reduced.

The connection between the support portions and the respective part of the component may be any suitable shape and may be a simple uniform rib or line of material (it will be recognised that because the support and component are built simultaneously in the AM machine the two can, in effect, be homogeneous before separation). Alternatively, the process parameters for forming the part and the support structure may be adapted so that the support structure is more porous than the part. Making the support structure more porous allows them to be weaker than the part itself facilitating break-away from the part.

Advantageously, the connection may be in the form of a plurality of discrete connections. This advantageously increases the surface area of the connection. By increasing the surface area of the connection the erosion agent can contact a greater proportion of the surface of the connection thereby further increasing the effectiveness of erosion and reducing the separation or de-coupling time needed.

For example, the discrete connections may have a triangular cross-section with the apex of the triangle making the connection between the support portion and the component. Such a shape may be in the form of a prism extending along the length or width of the support such that the apex of the prism forms a connection in a line with the component.

To further optimise erosion of the support portions, and in particular those support portions close to the connection, perforations or holes may extend into and/or completely through the support portions. The contact area for the erosion agent can thereby be further increased and separation time reduced.

The apex of the triangular profile may be truncated so as to have a flat top. The flat top increases the connection area with the component to increase the strength of the connection. This may for example be desired when supporting loads are high for example and a stronger connection is needed.

In an alternative arrangement the plurality of discrete connections may be in the form of domes or pyramids - all of which can be conveniently formed in the AM process to high levels of accuracy. Again to increase the connection strength the top of the connection may be truncated.

Adjacent discrete connections may be separated by a predetermined space depending on the loads required to support the respective part of the component in combination with any thermal stresses that may affect the connection during the AM process.

For example, in an electron beam melting AM process high temperatures are used which minimises stress and so the separation may be, for example, 5mm.

Alternatively in a laser beam melting AM process isolated high temperature is used in the melting process which causes high stresses in the component thus requiring a greater number of connections. Thus, the separation between adjacent discrete connections may be 1 mm.

As discussed above the erosion agent may be brought into contact with the connection using a tank or bath i.e. submerging the component and support portions. Advantageously the support portions (all or a sub-set) may be provided with internal conduits or pipes to allow the erosion agent to travel inside the support portion.

This provides at least two advantages:

First, the erosion agent can contact the inner surface of the support portion which causes the connection to dissolve from both the inside and outside of the connection to the component. This reduces separation time.

Second, in an arrangement where the entire support portion is to be eroded (as opposed to just the connecting portion) this increases the contact of the erosion agent which can erode the support portion from both inside and outside.

Advantageously such a conduit, pipe or passage allows the erosion agent to reach the connection much more quickly and effectively. Each support portion may be an inlet to the conduit at a distal end from the component and connection end. The component or connection end (the proximate end) may have one or more outlets that are configured to release erosion agent directly to the connection portion.

In effect the internal geometry of the support portion can act as a manifold to direct the erosion agent precisely to the optimal parts of the connection to effect the separation of the two.

As an alternative to submerging the entire component and support portions the inlet to the conduits with the support portions may act as a port or inlet into which the erosion agent can be poured or injected. This may advantageously reduce the amount of erosion agent required and the size of the tank or bath.

The erosion agent or liquid is selected according to the material which has been used in the AM process. For example, in an application where a titanium metal has been used to build the component and the support portions, an acid such as nitric acid may be used. A combination of acids may also be used, such as a combination of nitric acid and hydrofluoric acid (HNO3+HF), or sulfuric acid and hydrofluoric acid (H₂SO₄+HF).

As another example, in an application where a nickel superalloy has been used to build the component and support portions, multiple combinations of acids may be used sequentially such as sulfuric acid and hydrochloric acid (H₂SO₄+HCI) in a first step and nitric acid and hydrofluoric acid (HNO3+HF) in a second step.

In an arrangement where the component and support portions are submerged into the erosion agent, the erosive effect may advantageously be used to improve the surface finish of the entire component as discussed above. Advantageously during the build the dimensions of the component may be increased by a predetermined amount to account for the erosion of the surface during the support portion separation step. More specifically, a calculation or determination may be made of the amount of material (the thickness) of the component’s surface that will be eroded in the erosion bath in the time it will take for the connection to be eroded. This additional thickness is added to the outer dimensions of the component such that at the end of the final erosion step the resultant part not only has the precise dimensions originally required but the surface finish has also improved. Still further the support portions are de-coupled form the component. These three advantages can be realised in a single manufacturing step.

Viewed from another aspect there is provided an additive manufacturing method comprising the steps of building a three-dimensional component and a plurality of internal support portions, said portions connected to and arranged to support parts of the component during the build, the method comprising the step of simultaneously building at least one conduit arranged in use to communicate a liquid from an inlet of the conduit to an outlet, wherein the outlet of the conduit is located proximate to at least one connection between a support portion and the component.

Advantageously the outer wall of the conduit may act as one of the support portions providing the desired support to the component.

The skilled person will recognise that the process described herein may be used with any suitable AM manufacturing technique including, but not limited to, electron beam melting and laser beam melting. The term ‘powder bed fusion’ will be understood by the skilled person to mean an additive manufacturing process in which thermal energy selectively fuses regions of a powder bed.

Viewed from yet another aspect there is provided an additively manufactured component, said component further comprising a plurality of support members formed during the additive manufacture process connected to and extending from inner surfaces of the component, wherein at least one of said support members comprises an internal conduit having an open end proximate to a point at which the support member connects to the inner surface of the component.

Viewed from a still further aspect there is provided a method of manufacturing a component using an additive manufacturing process, wherein the component is built up of a plurality of layers and wherein support elements are incorporated into the build of the component during the additive manufacturing process to support portions of the component during the build, said method further comprising the step of disconnecting the support portions from the component by chemical erosion and wherein the time taken to erode connections between the support portions and the component is determined and a corresponding thickness (d) of 5 material which will be eroded over the remainder of the component is predetermined, and the dimensions of the component in the build are increased by said predetermined thickness (d).

Drawings

Aspects of the invention will now be described, by way of example only, with reference to the accompanying figures in which:

Figure 1 shows a cross-section of an AM manufactured component incorporating a plurality of support columns;

Figure 2 shows a basic view of 3 support portions connected to a component;

Figure 3 shows a single support portion with a plurality of discrete connections;

Figure 4A shows an erosion bath and schematic component including support portions;

Figure 4B illustrates the erosion effect;

Figures 5A to 5D show examples of support portions;

Figure 6 shows a manifold arrangement within a support portion; and

Figures 7A and 7B show one example of the flow path of erosion agent in a manifold of a support portion.

While the invention is susceptible to various modifications and alternative forms, specific embodiments are shown by way of example in the drawings and are herein described in detail. It should be understood however that drawings and detailed description attached hereto are not intended to limit the invention to the particular form disclosed but rather the invention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the claimed invention

It will be recognised that the features of the aspects of the invention(s) described herein can conveniently and interchangeably be used in any suitable combination

Detailed Description

Figure 1 shows a cross-section through a component which has been manufactured in an AM process and illustrates the need for support portions B1 to B5 which are arranged to support the component portions C1 to C5 as the individual layers of the component are laid one on top of the next.

Figure 2 shows a basic view illustrating support portions and a component. The three support portions 1a, 1b and 1c are elongate bodies 2 with triangular upper portions 3. In the example in figure 2 the apex 4 of each triangular portion 3 has been truncated to increase the contact area 5 between the support and component 6.

Because the support and component are built together in the AM machine process they are in fact homogeneous i.e. they are one and the same part. However, the support portions are sacrificial and are exclusively needed during the AM manufacturing process. Once the process is finished they can be de-coupled from the component 6.

Figure 2 is a schematic drawing illustrating the connection principle. In reality the support portion may comprise a plurality of small discrete connections between the support portion elongate body 2 and the component 6. Figure 3 illustrates how the connection may be used with a plurality of small connections. In figure 2 the connections 7 have triangular crosssections with the apex of each being connected to the component 6.

AM techniques advantageously allow these connections to be formed at extremely small scales and with high accuracy. For example, the base of each triangle may be of the order of 1 mm and the truncated apex in the order of 0.05mm to 0.6mm.

Figure 4A and 4B illustrate the erosion process. The combination of support portion 2 and component 6 have been submerged into a tank or bath 8 containing a combination 9 of nitric acid and hydrofluoric acid (HNO3+HF).

The component and supports are left in the erosion bath 8 for a predetermined period of time. The bath may optionally include an agitator or the like to cause circulation of the acid within the tank to enhance the erosion effect.

The erosion process occurs according to the following chemical reaction:

Ti +3HF — >TiF3+3/2H2$

Ti+ 6HF + 4HNO3-^H₂TiF₆ + 4NO₂+ 4H₂0

The circled image in Figure 4A shows a closer view of the connection 7 between the support 2 and component 6 corresponding to figure 3.

Figure 4B shows the connection having been eroded after a period of time. Each of the connections has been de-coupled from the component 6 by virtue of the acid dissolving the metal forming the connection. The two components can be separately removed from the bath 8.

Figure 4B also shows in dotted lines the additional erosive effect of the acid on the support outer surface 10 and component surface 11. These too are exposed to the acid and are also eroded in the erosion bath 8 by a thickness d. The erosion thickness d is dependent on the time within the bath (in combination with conditions in the bath such as acid strength and agitation/flow).

The process described herein may be used to erode only the connections 7 between support portions and the component, after which the two can be removed separately from the bath. In this application it is only the metal forming the connections 7 which requires erosion. Once this is safely eroded no further chemical erosion is needed. In this scenario increasing the contact of the erosive agent with the surfaces making up the connection is important; greater surface contact increases the erosion and reduces the de-coupling time between support and component.

Alternatively, the entire support portions may be eroded. In this scenario it is important to increase the surface contact area the erosion agent has with the entire support portion. To do this the support may be provided with a plurality of perforations or holes or may be formed of a low density structure which provides the necessary strength but optimises the erosive effect the erosion agent will have in the bath described above.

Figures 5A to 5D show alternative support portion options to increase the contact the erosive agent may have with the support portion surfaces.

In figure 5A a plurality of holes 12 are formed in the support 2 and entire through the entire support shown by dotted line 13.

Figure 5B shows a hollow portion 2 (a hollow section 14 in the centre of the support) and a plurality of holes 15 penetrating the walls of the support.

Figure 5C shows another arrangement comprising a hollow core 14. In this embodiment a low density frame is created by removing sections 16 from the outer wall of the support; and

Figure 5D shows a tubular or ‘chimney’ arrangement comprising a hollow core 14.

In each of the examples shown in Figure 5A to 5C the contact with the erosion agent is increased facilitating the dissolving of the support portion 2. The AM technique advantageously allows complex and optimised shapes to be formed such these at small scales and with high accuracy.

In both scenarios above there is an additional advantageous effect in that the component itself is exposed to the erosive acid which advantageously can improve the surface finish and remove any imperfections to provide a smooth undamaged outer surface of the component.

Figure 6 shows a further development of a support portion in cross-section. As shown in figure 6 the support portion is built in the AM process so as to comprise a conduit 17 having an inlet 18 at a lower part of the support 2. At the opposing end of the conduit one or more outlets 19 may be provided which allow erosion agent to be communicated to the connection 7. In effect the support portion can function as an integrated manifold to communicate erosion agent directly and internally to the connection 7.

The accuracy and controllability of AM processes allows the internal geometry of the support to be optimised for both strength and erosion agent flow.

Figures 7A and 7B show one example of how the internal conduit functioning as an erosion agent manifold may be used.

In Figure 7A the connection 7 is in the form of a plurality of concave elongate channels 20 with truncated surfaces 21 which connect to the component (not shown). It will be recognised that this is just one example of the shape and profile of the connection.

Figure 7B is an enlarged view of two of the channels in figure 7A and illustrates the manifold of the support portion.

Figure 7B represents only a small section of the connection 7. As shown the end of the conduit 17 closest to the connection 7 comprises a manifold 22 and a plurality of further conduits 23, 24, 25 and 26 each in fluid communication with one of the channels 20.

As shown the component 6 is coupled to the support portion 2 by means of the flat connections 21 - the two being homogeneous.

In use erosion agent E is either injected into the conduit 22 or flows through the conduit by virtue of being submerged in the bath as shown in figure 4A. Erosion agent can then flow, as shown by the arrows, directly into the channels 20 filling each channel. This advantageously commences erosion of the inner surfaces of the channel 20 as shown by dotted lines 27. After a period of time the connection 21 will be entirely dissolved and the support portion and component separated.

In a further embodiment the inlet to the conduit may be provided with a connector/coupling allowing erosion agent to be injected into the support portions thereby negating the need to submerge the component and support portions in a large bath. Erosion agent may then be forced through the support portions and directed to the connection between the supports and component to effect localised erosion.

The AM processes according to the invention allow huge flexibility in optimising the flow paths for chemical erosion within the support portions of an AM build. For example the conduits may be tapered, divergent, curved and other complex geometries that can be selected. The build could even be designed to include a reservoir to collect the erosion agent once it had passed through channels such as though shown in figure 7B. Still further the build could be designed to include barriers or inserts that prevent etching in certain specific areas of the build by preventing chemical agent from flowing to those areas.

The AM process may further comprise the steps of agitating the acid bath for improve flow of liquid followed by cleaning with water as well as a cleaning solution to remove acid traces after separation.

Claims

1. A method of manufacturing a component using an additive manufacturing process, wherein the component is built up of a plurality of layers and wherein support elements are incorporated into the build of the component during the additive manufacturing process to support portions of the component during the build, said method further comprising the step of disconnecting the support portions from the component by chemical erosion.

2. A method as claimed in claim 1, wherein chemical erosion is performed by introducing the component and support portions into a receptacle containing an erosion agent.

3. A method as claimed in claim 1 or 2, wherein the support portions are arranged to provide structural support between a base plate of the additive manufacturing machine and a portion of the component and/or between adjacent portions of the component.

4. A method as claimed in any preceding claim, wherein the connection between the support portion and the component has a cross-sectional area that is smaller than the cross-sectional area of the respective support portion immediately adjacent to the component.

5. A method as claimed in any preceding claim, wherein the connection between the support portion and the component is in the form of a plurality of discrete connections.

6. A method as claimed in claim 5, wherein the plurality of discrete connections are generally triangular in cross-section with the apex of each triangle forming the connection between the support portion and the component.

7. A method as claimed in claim 6, wherein the plurality of discrete connections are in the form of triangular prisms.

8. A method as claimed in claim 6 or 7, wherein the apex of each triangular cross-section is truncated.

9. A method as claimed in any preceding claim wherein outer walls of the support portions are provided with a plurality of perforations.

10. A method as claimed in any of claims 1 to 6, wherein the plurality of discrete connections are in the form of pyramids.

11. A method as claimed in claim 10, wherein the apex of each pyramid is truncated.

12. A method as claimed in any of claims 5 to 11 wherein the separation of adjacent discrete connections is less than 5mm.

13. A method as claimed in any of claims 5 to 11 wherein the separation of adjacent discrete connections is less than 1mm.

14. A method as claimed in any preceding claim, wherein at least one of the support portions comprises an internal conduit arranged in use to allow for the passage of an erosion liquid/agent.

15. A method as claimed in claim 14, wherein each conduit has an inlet at a first end of the support portion and at least one outlet at a second end of the support portion, and wherein the at least one outlet is proximate to a connection between the support portion and the component.

16. A method as claimed in claim 14 or 15, wherein each conduit has an inlet and a plurality of outlets.

17. A method as claimed in any of claims 14 to 16, wherein an erosion liquid/agent is introduced into each conduit and communicated to the connections between a support portion and a component to cause erosion of the connection.

18. A method as claimed in claim 17, wherein an erosion liquid/agent is injected into the inlet of the conduit.

19. A method as claimed in any preceding claim wherein the erosion agent/liquid is selected according to the material used in the additive manufacture process.

20. A method as claimed in any preceding claim wherein the erosion agent contains nitric acid.

21. A method as claimed in claim 20, wherein the erosion agent is nitric acid and hydrofluoric acid (HNOs+HF).

22. A method as claimed in any preceding claim, wherein a predetermined additional thickness of material is built onto the outer surfaces of the component being built during the additive manufacture process.

23. A method as claimed in claim 22, wherein the predetermined additional thickness of material is calculated based on a predetermined erosion thickness needed to separate the support portions from the component over a predetermined time interval.

24. A method as claimed in any preceding claim, wherein at least one support portion is hollow.

25. An additive manufacturing method comprising the steps of building a three-dimensional component and a plurality of internal support portions, said portions connected to and arranged to support parts of the component during the build, the method comprising the step of simultaneously building at least one conduit arranged in use to communicate a liquid from an inlet of the conduit to an outlet, wherein the outlet of the conduit is located proximate to at least one connection between a support portion and the component.

26. An additive manufacturing method as claimed in claim 25, wherein the outer wall of the conduit acts as one of the support portions.

27. An additive manufacturing method as claimed in any preceding claim wherein the additive manufacturing process is selected from electron beam melting or laser beam melting.

28. An additively manufactured component, said component further comprising a plurality of support members formed during the additive manufacture process connected to and extending from inner surfaces of the component, wherein at least one of said support members comprises an internal conduit having an open end proximate to a point at which the support member connects to the inner surface of the component.

29. A method of manufacturing a component using an additive manufacturing process, wherein the component is built up of a plurality of layers and wherein support elements are incorporated into the build of the component during the additive manufacturing process to support portions of the component during the build, said method further comprising the step of disconnecting the support portions from the component by chemical erosion and wherein the time taken to erode connections between the support portions and the component is determined and a corresponding thickness (d) of material which will be eroded over the remainder of the component is predetermined, and the dimensions of the component in the build are increased by said predetermined thickness (d).

Intellectual

Property Office

Application No: GB1707321.4