Method and apparatus for making an object

A method and apparatus for making an object comprising repeatedly selectively depositing a material by controlling one or more deposition areas using a deposition control plate comprising one or more apertures and selectively melting the selectively deposited material.

This invention claims the benefit of UK Patent Application No, GB1210738.9, filed on 18 Jun. 2012, which is hereby incorporated herein in its entirety.

FIELD OF THE INVENTION

Embodiments of the present invention relate to a method and apparatus for making an object. In particular, some relate to a method and apparatus for making a gas turbine component using additive layer manufacturing.

BACKGROUND TO THE INVENTION

Additive layer manufacturing is a process used to manufacture objects layer by layer. A layer of material is deposited and selectively melted to fuse the material into a layer of the object. This process is repeated to form the object in layers.

Additive layer manufacturing is expensive and time consuming.

BRIEF DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION

According to various, but not necessarily all, embodiments of the invention there is provided a method of making an object comprising repeatedly: selectively depositing a material by controlling one or more deposition areas using a deposition control plate comprising one or more apertures; and selectively melting the selectively deposited material.

According to various, but not necessarily all, embodiments of the invention there is provided an apparatus for making an object comprising: means for supporting a deposition control plate, wherein one or more apertures in the deposition control plate restrict deposition of material to one or more deposition areas; and means for selectively melting material deposited within the one or more deposition areas.

According to various, but not necessarily all, embodiments of the invention there is provided an apparatus for making an object comprising: supports configured to support a deposition control plate, wherein one or more apertures in the deposition control plate restrict deposition to one or more deposition areas; and an energy source configured to selectively melt material deposited within the one or more deposition areas.

Embodiments of the invention provide the significant advantage that the volume of material used is reduced using the deposition control plate.

The Figures illustrate a method2of making an object36comprising repeatedly: selectively depositing6a material28by controlling one or more deposition areas using a deposition control plate22comprising one or more apertures24; and selectively melting8the selectively deposited material28.

The figures and following description illustrate an object36being made in three layers. The description is limited to three layers for illustrative purposes. It will be readily understood by one skilled in the art that the object36may comprise fewer layers or more layers. For example the object36may comprise a single layer or the object36may comprise several hundred or more layers. It will be further understood by the person skilled in the art that the three layers illustrated in the figures and discussed below may be formed as part of an object36comprising many layers and may be the first three layers of the object36, the final three layers of the object36or three intermediary layers of the object36.

FIG. 1illustrates an example of a method2of making an object36. The method2may, for example, be employed in techniques such as additive layer manufacturing. One example implementation of the method2is illustrated inFIGS. 2A, 2B and 2Cwhich illustrate manufacture of an object36from layers26of material28.

The method2ofFIG. 1starts at block4. Next, at block6a material28is selectively deposited as a layer of material26.

The material28may be processed to form an object36. The material28may be converted from an unprocessed form to a processed form, layer by layer. The processed layers collectively form the object36.

The material28may for example be a solid or a liquid. The material28may be a solid comprising particles of regular or irregular size and shape. The material28may be for example a powder. The material28may comprise a metal, plastic or other material.

From block6, the method2moves to block8. At block8, the selectively deposited material28is selectively melted. As illustrated inFIGS. 2A, 2B and 2C, selectively melted material28solidifies and fuses to form a layer27of the object36.

Next, at block10ofFIG. 1, it is determined if the object36is complete. From block10the method2branches. If the object36is complete the method2passes to block12and ends. If the object36is not complete, the method2returns to block6.

On returning to block6, additional material28is selectively deposited and selectively melted to form, as illustrated inFIGS. 2A2B and2C another layer27of the object36. The selective melting also acts to fuse a current layer27of the object36with the previous layer27of the object36.

The method2shown inFIG. 1comprises both selective deposition and selective melting thus reducing the quantity of supporting powder around the object being constructed.

An example of the method2will now be described in greater detail with reference toFIGS. 2A to 2C.FIGS. 2A, 2B and 2Cillustrate a system20and an apparatus21for making an object36. The system20comprises an apparatus21and a deposition control plate22. The deposition control plate22comprises an aperture24, which restricts deposition of material28to a deposition area.

The apparatus21may comprise a platform38. The platform38is able to move in a first direction, indicated by the arrow25and a second direction, opposite to the first direction. The platform38defines a plane orthogonal to the first direction.

The apparatus21may further comprise supports30for supporting a deposition control plate22over the platform38, a deposition system34configured to deposit the material28and an energy source32for selectively melting deposited material28. In this example, the energy source32is configured such that an output29from the energy source32may be directed at any point over the platform38.

The energy source32may be, for example, a laser or an electron beam source. The energy source32may be configured to heat the apparatus21in addition to melting the material28.

FIG. 2Aillustrates an example of the formation of a first layer271of an object36according to the method2. Material28is selectively deposited onto the platform38, in the aperture24of the deposition control plate22, to form a first layer261. The material28is selectively deposited such that the top of the selectively deposited material28is level with the top of the deposition control plate22. The material28is then selectively melted to form a first layer271of the object36.

The selective melting is performed by tracing the output29of the energy source32over the parts of the material28within the aperture24that are to be selectively melted. The output29of the energy source32is traced in a pattern that defines the first layer271of the object36. The tracing defines a perimeter, inside which the material28is melted.

Material28melts when it is exposed to the output29of the energy source32for a first period of time. The material28fully melts and fuses. Therefore, the tracing must be performed at a speed to allow melting of the material28. This may be achieved, for example, by holding the output29of the energy source32at a point for the first period of time, and then moving the output29of the energy source32to a next point to be melted.

When the first layer271is complete, the platform38is moved down and a second layer272is formed as shown inFIG. 2B. In some examples, no material28is melted in the first layer261of an object36and the platform38is moved down immediately after the selective deposition.

Material28is selectively deposited onto the first layer261, in the aperture24of the deposition control plate22to form a second layer262. The material28is selectively deposited such that the top of the selectively deposited material28is level with the top of the deposition control plate22. The material28is then selectively melted to form a second layer272of the object36. The selective melting also fuses the second layer272to the first layer271.

The selective melting is performed by tracing the output29of the energy source32over the parts of the material28within the aperture24that are to be selectively melted. The output29of the energy source32is traced in a pattern that defines the second layer272of the object36. The tracing defines a perimeter, inside which the material28is melted.

When the second layer272is complete, the platform38is moved down and a third layer273is formed as shown inFIG. 2C.

Material28is selectively deposited onto the second layer262, in the aperture24of the deposition control plate22to form a third layer263. The material28is selectively deposited such that the top of the selectively deposited material28is level with the top of the deposition control plate22. The material28is then selectively melted to form a third layer273of the object36. The selective melting also fuses the third layer273to the second layer272.

The selective melting is performed by tracing the output29of the energy source32over the parts of the material28within the aperture24that are to be selectively melted. The output29of the energy source32is traced in a pattern that defines the third layer273of the object36. The tracing defines a perimeter, inside which the material28is melted.

In this example, when the third layer273is complete the object36is then complete.

The distance that the platform38is moved down following the completion of a layer26defines the thickness of the subsequent layer26. In the example described above and with reference toFIGS. 2A, 2B and 2Cand in further examples described below and in reference toFIGS. 2D, 3A, 3B and 3C and 6A, 6B, 6C and 6Dthe platform38is moved down so that the top of the previously formed layer26is level with the bottom of the deposition control plate22, i.e. the layers26have the same thickness as the deposition control plate22.

In other examples, the thickness of the layers26may be less than the thickness of the deposition control plate22. The layers26may be between 20 microns and 200 microns thick. In some examples, different layers26may be of different thickness.

FIG. 2Dillustrates an alternative example of forming a first layer261. A deposition control plate insert37is placed in the aperture22before the object36is started. The platform38may then be moved down to define the correct thickness for the first layer261. Alternatively, the thickness of the deposition control plate insert37may be such that the platform38does not need to be moved to define the correct thickness for the first layer261. The control plate insert37descends with the platform38for each layer26of the object36being formed.

Material28to form the first layer261is selectively deposited on a deposition control plate insert37instead of the platform38. The material28is selectively deposited such that the top of the selectively deposited material28is level with the top of the deposition control plate22. The material28is then selectively melted to form a first layer271of the object36. Subsequent layers26are formed as described previously.

In the example illustrated inFIG. 2D, the deposition control plate insert37enables the first layer261to be thinner than the deposition control plate22.

In making the object36, a void31is formed underneath the deposition control plate22. The sides of the void31are formed by the apparatus21and the material28. The material28must be retained in some way so that it does not fall into the void31.

In one example, the method2may comprise partially melting at least some of the selectively deposited material28prior to the selective melting8of the objected36being formed.

Material28is partially melted when it is exposed to the output29of the energy source32for a second period of time, shorter than the first period, to loosely fuse the material28. In another example, material28is partially melted by using a lower energy output29of the energy source32. The partially melted material28is thus self-supporting. The partial melting is performed by tracing the output29of the energy source32over the parts of the material28that are to be partially melted.

FIGS. 3A to 3Cillustrates an example where a retainer44is formed to retain the material28during the process of making an object36.

FIG. 3Aillustrates an example of the formation of a first layer271of an object36. The method initially progresses as described above. A first part40of the material28is melted to form the first layer271of the object36. A second part42of the material28is melted to form the first layer of the retainer44. The second part42of the material28surrounds the layer271of the object36, forming a retaining enclosure.

After the first layer271of the object36and the first layer of the retainer44are formed, the platform38is moved down and a second layer262is formed as shown inFIG. 3B. The first layer of the retainer44retains the material28in the first layer261and prevents it falling into the void31when the platform38is moved.

Material28is selectively deposited in the aperture24. The material28is selectively deposited such that the top of the selectively deposited material28is level with the top of the deposition control plate22. A first part40of the material28is melted to form the second layer272of the object36. A second part42of the material28is melted to form the second layer of the retainer44. The second part42of the material28surrounds the layer272of the object36and overlies the first layer of the retainer44. The selective melting fuses the first layer271of the object36to the second layer272of the object36and the first layer of the retainer44to the second layer of the retainer44.

The second part42of the material28may be separate from the deposition control plate22and the layers27of the object36.

After the second layer272of the object36and the second layer of the retainer44are formed, the platform38is moved down and a third layer263is formed as shown inFIG. 3C. The second layer of the retainer44retains the material28in the second layer262and prevents it falling into the void31when the platform38is moved.

Material28is selectively deposited in the aperture24. The material28is selectively deposited such that the top of the selectively deposited material28is level with the top of the deposition control plate22. A first part40of the material28is melted to form the third layer273of the object36. Then a second part42of the material28is melted to form the third layer of the retainer44. The second part42of the material28surrounds the third layer273of the object36and overlies the first and second layer of the retainer44. The selective melting fuses the second layer272of the object36to the third layer273of the object36and the second layer of the retainer44to the third layer of the retainer44.

In this example, when the third layer273is complete the object36and the retainer44are complete.

FIG. 4illustrates a further example of how the material28may be retained so that it does not fall into the void31. The system20may further comprise a preformed telescopic retainer50.

The telescopic retainer50may be configured so that the lower layers of the retainer50fit inside the upper layers of the retainer. Therefore, when making the first layer271of an object36, the telescopic retainer50will be fully compressed and have a height matching the height of the first layer261.

When the platform38moves in order to make the second layer272of the object36, the telescopic retainer50is partially extended, so that the height of the telescopic retainer50is increased to match the height of the first two layers. Similarly when the platform38moves to make the third layer273of the object36, the telescopic retainer50is again expanded to match the height of the three layers. In this way, the telescopic retainer50acts to prevent material28falling into the void31.

In some examples, the method2may require the apparatus21to be environmentally controlled or sealed from the external atmosphere. This can be achieved by making a sealed apparatus and keeping it under vacuum or by flooding the apparatus with an inert gas.

In some examples, it may also be necessary to keep the object36in a environmentally controlled container64after the object36has been completed.FIG. 5shows an example of a completed object36in an environmentally controlled chamber64. Before the object36is made, a base60is provided. The object36and a retainer44is then made layer by layer. Once the object36is completed, a cap62is provided. The base60, layers of the retainer44and the cap62combine to form the container64.

The deposition control plate22should be configured to withstand any heating required in the method2and should be configured to support the load of material28deposited. The deposition control plate22should also be formed from a material that is inert with respect to the method2. The deposition control plate22may require out-gassing before the method is carried out.

The deposition control plate22may be made from, for example, 316 stainless steel or the same material as the object36. The deposition control plate22may be, for example, a preformed deposition control22plate provided before the process has started.

In some examples, the aperture24of the deposition control plate22is fixed throughout the process. In these examples, the aperture24should be configured to have larger dimensions than the largest dimensions of the object36in any of the layers27.

Alternatively, in other examples, the aperture24of the deposition control plate22may be varied throughout the process.FIGS. 6A to 6Dillustrate an example of a method of forming an object36where the aperture24is varied during the process.

FIG. 6Aillustrates the formation of the first layer271of the object36. A deposition control plate22is provided with a first aperture70defined by a first perimeter72. Material28is selectively deposited in the first aperture70. The material28is selectively deposited such that the top of the selectively deposited material28is level with the top of the deposition control plate22. An interior part74of the material28is selectively melted to form the first layer271of the object36.

Following the formation of the first layer271of the object36, a second aperture80, defined by a second perimeter82is formed by selectively melting material adjacent to the first aperture76. The second aperture80is used for forming the second layer272of the object36as shown inFIG. 6B. The selective melting fuses the material adjacent to the aperture76to form the deposition control plate22. This process forms a new deposition control plate22comprising the second aperture80. The new deposition control plate22is formed by augmenting the original deposition control plate22with the selectively melted material adjacent to the first aperture76.

The platform38is then moved down to form the second layer272. As shown inFIG. 6C, the material28that was not melted and the material28forming the first layer271of the object36also move down with the platform38. However, the melting process has fused the material28adjacent to the aperture76to the deposition control plate22. Therefore a new deposition control plate78comprising a second aperture80is formed.

FIG. 6Dshows the formation of a second layer272of the object36. Material28is selectively deposited in the second aperture80. The material28is selectively deposited such that the top of the selectively deposited material28is level with the top of the deposition control plate22. An interior part74of the material28is selectively melted to form the second layer272of the object36. A further aperture for forming the third layer273may be formed by selective melting material28adjacent to the second aperture80.

In some examples, the deposition control plate22is not provided as a preformed deposition control plate22but is formed in the apparatus21before the object36is made.

FIG. 7Ashows an example of a method96for forming a deposition control plate22. The method96may be placed between blocks4and6of the method2illustrated inFIG. 1. The method96starts at block90where material28is deposited over the platform38.

The method96then proceeds to block92. The material28deposited over the platform38is selectively melted to form a deposition control plate22comprising at least one aperture24.

When the deposition control plate22is formed, the platform38is moved down. The deposition control plate22is supported above the platform38so does not move down. However the material28in the aperture24, which is not selectively melted, moves down with the platform38. The first layer271of the object36may then be formed.

FIG. 7Billustrates an example of a method98than can be placed between blocks10and12of method2illustrated inFIG. 1. The method98comprises block94. The object36is removed from the material28not melted to leave the object36.

In some examples, releasing the material28may require physical or chemical processes to remove the material28. For example, where the material28not melted has been partially melted, the material28may be removed by, for example, sand blasting.

Alternatively, removing the object36from the material28not melted may involve removing the material28from a retainer44,50such as described in reference toFIGS. 3A to 3C, 4 and 5.

The apparatus21comprises supports30configured to support the deposition control plate22over the platform38. The supports30may be, for example retractable pins106or at least one recess110configured to interact with the deposition control plate22.

FIGS. 8A and 8Billustrate an example of an apparatus21comprising retractable pins106configured to support the deposition control plate22.

FIG. 8Aillustrates the apparatus21without the deposition control plate22. The sidewalls108of the apparatus21define a volume102in which the object36is formed. When the deposition control plate22is not in place, the retractable pin106is housed outside the volume102. For example, the pins106may be entirely housed in the side wall108.

FIG. 8Billustrates an example of the apparatus21when the deposition control plate22is in place. The retractable pin is now extending into the deposition control plate22which is in the volume102. The retractable pin106therefore supports the deposition control plate22within the volume102.

The deposition control plate22may be configured to receive the pins106of the apparatus21. For example, the deposition control plate22may comprise channels configured to align with the pins106.

If the deposition control plate22is formed as part of the method2, as discussed above with reference toFIG. 7A, the pins106should be extended into the volume102before the deposition or selective melting of the material28. In this way the deposition control plate22is formed around the pins106.

In some examples the apparatus21may comprise two retractable pins106. In other examples, the apparatus21may comprise more retractable pins106.

FIGS. 9A to 9Dillustrate an example of an apparatus21comprising recesses110configured to support the deposition control plate22.

FIGS. 9A and 9Billustrate an example of the apparatus21when the deposition control plate22is not place.FIG. 9Aillustrates a plan view of the apparatus21. Recesses110are formed in the side walls108by forming protrusions from the side walls108, which act to make the apparatus21wider at certain points.FIG. 9Bshows a side view of the apparatus21taken through A.FIG. 9Billustrates that the protrusions have a depth which defines the extent of the recess110.

FIGS. 9C and 9Dillustrate an example of the apparatus21when the deposition control plate22is in place. The deposition control plate22is configured to have protrusions112aligned with the recesses110. The protrusions112rest on the base of the recess110and act to support the deposition control plate22.

The apparatus21may comprise one recess110. For example, the apparatus21may comprise one continuous recess110around the perimeter of the volume102. Alternatively, the apparatus21may, for example, comprise a number of recesses110arranged around the perimeter of the volume102.

In some examples, the recesses110, may be configured so that when the deposition control plate22is formed as part of the method2, as discussed above with reference toFIG. 7A, material28is deposited in the recess110in step90. The energy source32may also be configured to be able to selectively melt the material28deposited in the recess110to form protrusions that support the deposition control plate22.

The deposition control plate22acts to reduce the effective volume102of the apparatus21by reducing the total area on which material28must be deposited.

FIGS. 8A and 8B and 9Ato D show an example of a deposition control plate22supported over the platform38. The apparatus21may comprise a deposition system34configured to deposit the material28.

The deposition system34may, for example, comprise a hopper, configured to dispense material28and a spreading system configured to spread the material28. The deposition system34is configured such that the top of the material28is spread so as to be level with a plane100.

The supports30of the apparatus21are configured to support the deposition control plate22over the platform38so that the top104of the deposition control plate22is level with the plane100.

In some examples, the deposition of material28by the deposition system34can be varied depending on the deposition control plate22. The size of the aperture24can be different depending on the size of object36to be made. In some examples, the deposition control plate22may comprise more than one aperture24to allow a number of objects36to be made simultaneously.

In one example, the deposition of material28is varied depending on the location, number and size of apertures114,116,118,120. For example, the amount of material28deposited may be varied depending on the volume of material28required.

For example, referring toFIG. 9C, if a deposition control plate22comprises four apertures114,116,118and120and objects36are to be made in the four apertures114,116,118,120, a first amount of material28will be deposited and spread over the entire deposition control plate22.

Referring again toFIG. 9C, if the deposition control plate22comprises only a single aperture114and an object36is to be made in this aperture114, a second amount of material28, less than the first amount, will be deposited. The deposited material28will then be spread over the entire area of the deposition control plate22.

If, for example, the deposition control plate22comprises two apertures114and116, then a third amount of material28, less than the first amount and more than the second, will be deposited. The deposited material28will then be spread over the entire area of the deposition control plate22.

In other examples, the area over which the material28is spread may be altered, by, for example, controlling where the material28is deposited.

For example, if a deposition control plate22comprises four apertures114,116,118,120and objects36are to be formed in apertures114and116only, material28may not be deposited along the full extent of the deposition control plate22orthogonal to A. Material may only be deposited in an area level with apertures114and116. The material28is then spread along the full extent of the deposition control plate22in the direction of A.

FIGS. 2A, 2B and 2C, 3A, 3B and 3C, 4, 5, 6, 8 and 9illustrate an apparatus21for making an object36. The apparatus21comprises a platform38configured to move in the vertical direction. The apparatus21further comprises means for supporting a deposition control plate22over the platform38. One or more apertures24in the deposition control plate22restrict deposition of material28to one or more deposition areas over the platform38.