The present invention relates to additive manufacturing of metal parts. More pre- cisely the present invention relates to an additive manufacturing method wherein heat sensitive components, such as electronic components, are embedded inside the manufactured metal part during the additive manufacturing process.

Additive manufacturing technologies provide various advantages and possibilities for combining different kinds of components and materials for end products due to the layer-by-layer nature of the manufacturing process, where material is added where needed, rather than subtracted or formed from basic shapes. However, when manufacturing parts and components from metals, a thin layer of metal powder is typically completely melted with a heat input, whereby the high manufacturing tem peratures require quite high heat tolerance from the components to be embedded into the metal part during its additive manufacturing process. Alternatively, the em bedded component needs to be shielded in some way against the heat during the embedding and continued manufacturing of the part.

The heat accumulation in metal powder bed fusion additive manufacturing is pres ently typically handled by increasing the waiting time between successive fusion layers. This causes the build time of the part to be formed increase, especially with the relative slow processes, such as laser powder bed fusion (LPBF) process for example. Further, the increased waiting time usually only bring incremental benefits and easily leads to very long waiting times, up to and over 60 seconds, between layers, in order to obtain any noticeable effect on the cooling. Typical practice, especially with LPBF, is actually to pre-heat the substrate in order to reduce the cooling rate of the formed part. This is done as an attempt to reduce residual stresses that can develop in the formed part.

The accumulated heat in the metal part during the powder bed fusion additive man ufacturing process effectively reduces the options for suitable components to be added inside the part being formed.

The present invention provides a novel solution for laser powder bed fusion additive manufacturing of metal parts and embedding heat sensitive components therein during the additive manufacturing process, while solving or at least mitigating the problem of excessive heat accumulation in the part during its forming.

In the present invention the area of the formed part, where the heat sensitive com ponent is embedded, is cooled during the additive manufacturing process. This cool ing is obtained with at least one cooling channel formed in the formed portion of the part to be manufactured before the additive manufacturing process is interrupted and the heat sensitive component is placed at its place in the formed portion of the part to be manufactured. This way the heat sensitive component can be protected against the created and accumulating heat during the continued additive manufac turing process of the metal part.

In the method of the invention for embedding components during additive manufac turing of metal parts, the product is formed with laser powder bed fusion process, at least one space for a component is formed inside the metal material of the product during the additive manufacturing process, the additive manufacturing process is interrupted before the said space is closed, the component is inserted in the said open space, and the additive manufacturing process for manufacturing the product is continued, at least one cooling channel, for cooling the area of the product wherein the said space is located, is formed inside the product to be manufactured before the additive manufacturing process is interrupted for insertion of the said compo nent, and cooling fluid is conveyed in the at least one cooling channel.

This way an active cooling channel, or channels, can be integrated in the formed portion of the part to be manufactured, which conveys heat away more effective than the passive heat sink, i.e. the substrate metal material of the formed portion of the part, which is a common practice presently.

In an embodiment of the method of the invention the cooling fluid is conveyed to the cooling channel via a building platform, on which the product is formed. In this em bodiment the building platform preferably comprises internal channels with openings on the surface on which the product is formed for conveying the cooling fluid from building platform to the at least one cooling channel in the formed portion of the product. The internal channels of the building platform in this embodiment can also be utilized for cooling the building platform itself during the powder bed fusion pro cess of the product formed on the building platform. In an embodiment of the method of the invention unfused powder is removed from the formed at least one cooling channel before the cooling fluid is conveyed in the cooling channel.

In an embodiment of the method of the invention the cooling fluid is preferably water. Alternatively, other suitable cooling fluids, such as suitable oil, can be used in the cooling.

More precisely the features defining a method in accordance with the present inven tion are presented in claim 1 . Dependent claims present advantageous features and embodiments of the invention.

Exemplifying embodiments of the invention and their advantages are explained in greater detail below in the sense of example and with reference to accompanying drawings, where

Figures 1 A-1 B show schematically an embodiment of a method of the inven tion, and

Figure 2 shows schematically an alternative embodiment of a method of the invention.

Figures 1A-1 B show schematically an embodiment of a method of the invention, wherein a part 1 is formed with powder bed fusion process on a building platform 2.

In powder bed fusion process, the formation of the product 1 proceeds in layers wherein the first layer is formed by spreading a layer of powder on the building plat form 2 and then fusing the powder with an energy beam from the predefined areas of the powder layer. In the present invention the powder is metal powder, and the energy beam is laser. After the formation of the first layer, a new layer of powder is spread on top of the previous powder layer and the formed portion of the part, and this new powder layer is then fused with the energy beam from the predefined areas of the powder layer. This process is repeated layer by layer until the finished part 1 is obtained. After each powder layer is selectively fused with the energy beam, the building platform 2 is typically moved downwards, or the sidewalls restricting the powder bed (not shown) are moved upwards, stepwise for the spreading of the new powder layer.

In figure 1A is shown the first stage of the formation of the part 1 with the method of the invention. In the situation of figure 1A, the formation of the part 1 has proceeded to stage, where a space 3 is formed inside the completed portion of the part 1 and where the said space 3 is still accessible via its open upper surface. At this stage the powder bed fusion process is interrupted, powder accumulated in the space 3 is removed and a component 4 is added in the space.

During the formation of completed portion of part 1 shown in figure 1 A, a cooling channel 5 is simultaneously formed inside the part 1 so that the cooling channel is completed inside the formed portion of the part 1 before the powder bed fusion pro cess is interrupted for the inserting of the component 4 into the space 3.

In this embodiment the building platform 2 comprises a cooling channel 6. The cool ing channel 6 comprises branches extending and opening to the upper surface of the building platform 2. The location of these openings of the upper surface of the building platform 2 are utilized in the formation of the cooling channel 5 inside the part 1 so, that the starting point and the ending point of the cooling channel 5 are located at the same places than where the openings of the upper surface of the building platform 2 are located. This allows the circulation of cooling fluid via the cooling channel 6 of the build platform 2 through the cooling channel 5 of the part 1 .

In this embodiment there is shown only a single cooling channel 5 inside the part 1 . It is, however, evident that there can be more than one cooling channel 5 inside the part 1 with the corresponding openings on the building platform 2, if that is needed or desired.

After the powder bed fusion process is interrupted in the stage shown in figure 1A, the powder remaining in the cooling channel 5 and accumulated in the cooling chan nel 6 during the formation of the completed portion of the part 1 is preferably re moved, by blowing pressurized air through the cooling channels 5 and 6 for exam ple, and the circulation of cooling fluid via the cooling channels 5 and 6 is started with a suitable pump (not shown) for example.

The cooling fluid can be water, for example, or other suitable cooling fluid like suit able oils. Suitable gasses can also be used for the cooling. Preferably, due to envi ronmental considerations and ease of obtaining and handling etc., the cooling fluid is water.

The cooling channel 5 is formed inside the formed portion of part 1 so, that it pro vides cooling effect especially for the area of the space 3, so that the temperature affecting the component 4 placed inside the space 3 during the formation of the part 1 can be lowered. This is obtained for example by forming the cooling channel 5 inside the completed portion of part 1 so that it runs close by and/or circulates the space 3.

The space 3 for the component 4 can be dimensioned so, that the component 4 snugly fits inside the space 3 so that no additional fixing means are required, or the space can be large enough to contain the component 4 and separate fixing means for example. It is, however, preferable that in the formed space 3 there is at least some distance between the component 4 and the upper surface of the formed por tion of the part 1 , so that the melting or fusing of the powder during the closing of the space 3 when the powder bed fusion process is continued does not take place in the immediate vicinity of the component 4.

After the component 4 is placed, and fixed if that is required, at the space 3, the interrupted powder bed fusion process is continued by forming a new powder layer on top of the formed portion of the product 1 , and fusing it with the energy beam at predetermined areas. During the formation of the first powder layer, any open area left in the space 3 is also filled with the powder. The layer formation and fusing is continued until the final part 1 is obtained as shown in figure 1 B. During the contin ued powder bed fusion process the cooling fluid is circulated in the cooling channel 5.

Alternatively, the space 3 can also be closed with a separate metal lid after the component 4 is placed and fixed at the space and before the powder bed fusion process is continued. This allows the space 3 to remain powder-free during the rest of the powder bed fusion process.

Once the part 1 is formed, it is detached from the building platform and required finishing actions, if any, are carried out. The said finishing steps may include filling the cooling channel 5 with suitable material, or plugging the openings of the cooling channel 5 on the surface of the part 1 , for example. The channel 5 can also be left in the final part 1 as it is.

In the embodiment of figures 1A and 1 B the cooling channel 6 in the building plat form 2 does not merely provide cooling fluid for the cooling channel 5 once it is completely formed inside the product 1 , but can also provide significant cooling for the building platform 2 itself, as can be seen from the figures. Thus, the branches of the cooling channel 6 extending and opening to the upper surface of the building platform 2 can be equipped with suitable valve members (not shown) for opening and closing the fluid connection between the cooling channel 6 and cooling channel 5, so that the cooling fluid can be circulated in the cooling channel 6 before the cooling channel 5 is completed inside the product 1 during the powder bed fusion process.

In the alternative embodiment shown in figure 2 the cooling channel 6’ formed inside the building platform 2’ extends directly from the bottom surface of the building plat form to the upper surface of the building platform.

This embodiment allows for simpler building platform 2’ structure, but the cooling of the building platform itself during the powder fusion process before the cooling chan nel 5 inside the product 1 is completed cannot be obtained. The specific exemplifying embodiments of the invention shown in figures and dis cussed above should not be construed as limiting. A person skilled in the art can amend and modify the embodiments described in many evident ways within the scope of the attached claims. Thus, the invention is not limited merely to the em bodiments described above.