TECHNICAL FIELD

[0001] The present invention relates to a vacuum chamber and to an additive manufacturing process using such a vacuum chamber.

BACKGROUND OF THE INVENTION

[0002] Freeform fabrication or additive manufacturing is a method for forming three- dimensional articles through successive fusion of chosen parts of powder layers applied to a worktable.

[0003] An additive manufacturing apparatus may comprise a work table on which said three-dimensional article is to be formed, a powder dispenser, arranged to lay down a thin layer of powder on the work table for the formation of a powder bed, an energy beam for delivering energy to the powder whereby fusion of the powder takes place, elements for control of the energy given off by the energy beam over said powder bed for the formation of a cross section of said three-dimensional article through fusion of parts of said powder bed, and a controlling computer, in which information is stored concerning consecutive cross sections of the three-dimensional article. A three-dimensional article is formed through consecutive fusions of consecutively formed cross sections of powder layers, successively laid down by the powder dispenser.

[0004] The additive manufacturing process may be performed in a vacuum chamber. For some reason it may be necessary to illuminate the powder surface. Presently the illumination device is provided outside the vacuum chamber and illuminates the work table through a window. Since the additive manufacturing process may comprise fusing of metals there are meal vapors inside the vacuum chamber which may be deposited at all surfaces inside the vacuum chamber. If the window through which said illumination is taking place is not protected in some way, said window will receive said metal vapor deposition and thereby loose its transparency. A known solution to this problem is to provide a movable film in front of the window inside the vacuum chamber. As the film becomes deposited with said metal it is replaced with a new non-metal deposited area of the film. A problem with said method is that the film is expensive and it requires reloading of the film after a certain usage of the machine. Another method of keeping the window free from metal deposition is to provide a steady flow of gas in front of the window on the inside of the vacuum chamber. A problem with said solution is that such an arrangement cannot be used in high vacuum conditions because the gas will destroy the vacuum. There is a need in the art of vacuum chamber with an illumination device which is cheaper, more reliable and service friendly than the existing solutions.

SUMMARY OF THE INVENTION

[0005] An object of the invention is to provide a vacuum chamber which will solve the issues mentioned above.

[0006] The above mentioned object is achieved by the features in the method according to claim 1.

[0007] In a first aspect of the invention it is provided a vacuum chamber in which metallic vapours are deposited, said vacuum chamber comprising at least one reflector and a tube, where a first end of said tube is arranged inside said vacuum chamber and provided for receiving electromagnetic radiation, a second end of said tube is extending inside said vacuum chamber and said tube is arranged in said vacuum chamber so that electromagnetic radiation emanating from any position of the substrate without being reflected by any part in said vacuum chamber is out of sight of the first end of said tube, said reflector is arranged inside said vacuum chamber to reflect electromagnetic radiation which is exiting from said second end of said tube onto said substrate surface which is generating metallic vapour or to reflect electromagnetic radiation which is exiting from said substrate surface to said second end of said tube.

[0008] An advantage of the present invention is that the tube may be used for hiding a camera and/or an illumination source and/or a protective window which is provided inside or outside said vacuum chamber. Any metal deposition will be deposited inside the tube instead of reaching the camera and/or the illumination source or a protective window for said camera and/or said illumination source.

[0009] In one example embodiment of the present invention an electromagnetic source is provided inside said vacuum chamber and attached to said first end of said tube or inside said tube. [0010] An advantage of this embodiment is that the electromagnetic source, for illuminating the substrate 103, may not lose its intensity because of metal deposition on its outer surface. The metal deposition will not reach the illumination source but instead deposit the inner wall of the tube before reaching the illumination source. The tube is protecting or shielding the illumination source from metal deposition. The illumination source may be attached to the first end of said tube and the electromagnetic radiation which is emanating from the illumination source is exiting from the second end of the illumination source. There is a distance between the illumination source and the second end of the tube, which may be in the order of the length of the tube which may be 3- 50cm.

[0011] In another example embodiment of the present invention an electromagnetic source is provided outside a window of said vacuum chamber and said tube is provided at said window of said vacuum chamber.

[0012] An advantage of this embodiment is that the electromagnetic source may be used more freely compared to if said source is to be fitted into said tube inside said vacuum chamber. The tube is protecting said window from receiving said metal deposition allowing said electromagnetic source to illuminate the surface of the substrate 103 with constant intensity throughout the lifetime of the illumination source.

[0013] In another example embodiment of the present invention said first end of said tube is sealed to said window or said wall of said vacuum chamber.

[0014] By fixing the tube to the wall of the vacuum chamber one is eliminating the risk of any metal deposition slipping in between said first end of said tube and said wall of said vacuum chamber.

[0015] In still another example embodiment of the present invention said window is attached to an inside wall of the vacuum chamber or an outside wall of the vacuum chamber or a first window in the inside wall and a second window in the outside wall.

[0016] In yet another example embodiment of the present invention said reflector and said tube is a single unit.

[0017] An advantage of this embodiment is a more compact solution which may be easier to install in the vacuum chamber. [0018] In still another example embodiment the length of the tube is between 3cm - 40cm. In another example embodiment said length is 20 cm.

[0019] In still another example embodiment said reflector is flat, convex or concave. Any of said reflectors may be tiltable.

[0020] A customized reflector having a specific shape may increase, decrease or maintain the shape of the electromagnetic radiation beam exiting from the tube or from the substrate surface. The advantage of a tiltable reflector is that the angle of inclination of said illumination may be varied. A varied angle of inclination may serve the purpose of increasing the information from a reflected image from said surface of said substrate. This in turn may be useful if a camera is arranged so as to receive the electromagnetic radiation which is exiting from said substrate and/or electromagnetic radiation which is emanating from the electromagnetic source.

[0021] In another aspect of the present invention it is provided a method of producing a part from powder comprising the steps of: providing a first layer of the powder at a target surface, directing energy at selected positions of said first layer of powder corresponding to a first cross section of the part to fuse, depositing a second layer of powder over both fused and unfused portions of said first layer of powder after said directing step, so that the second layer of powder is supported by fused and unfused powder positions of said first layer of powder, directing energy at selected positions of said second layer of powder corresponding to a second cross section of the part to fuse, so that fused powder at one of said selected positions of said second layer of powder fuses to fused powder in said first layer, wherein said fusion process is taking place in a vacuum chamber as disclosed above.

[0022] Illumination may serve many purposes during additive manufacturing, for instance for capturing images of the powder bed with and without illumination. The visibility of the ongoing process through the vacuum chamber may be enhanced for a human eye or the camera. The advantage of having an illumination system which does not require any service may become very important as the building times of larger and larger objects in additive manufacturing chambers may take longer and longer time.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS [0023] The invention will be further described in the following, in a non-limiting way with reference to the accompanying drawings. Same characters of reference are employed to indicate corresponding similar parts throughout the several figures of the drawings:

[0024] Fig. la depicts a schematic side view of a first example embodiment of a vacuum chamber according to the present invention;

[0025] Fig. lb depicts a portion of a vacuum chamber according to a second example embodiment of the present invention;

[0026] Fig. lc depicts a portion of a vacuum chamber according to a third example embodiment of the present invention;

[0027] Fig. Id depicts a portion of a vacuum chamber according to a fourth example embodiment of the present invention;

[0028] Fig. le depicts a portion of a vacuum chamber according to a fifth example embodiment of the present invention;

[0029] Fig. I f depicts a portion of a vacuum chamber according to a sixth example embodiment of the present invention;

[0030] Fig. lg depicts a portion of a vacuum chamber according to a seventh example embodiment of the present invention; and

[0031] Fig, 2 depicts a schematic side view of an example embodiment of a freeform fabrication or additive manufacturing apparatus.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

[0032] To facilitate the understanding of this invention, a number of terms are defined below. Terms defined herein have meanings as commonly understood by a person of ordinary skill in the areas relevant to the present invention. Terms such as "a", "an" and "the" are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. The terminology herein is used to describe specific embodiments of the invention, but their usage does not delimit the invention, except as outlined in the claims.

[0033] The term "three-dimensional structures" and the like as used herein refer generally to intended or actually fabricated three-dimensional configurations (e.g. of structural material or materials) that are intended to be used for a particular purpose. Such structures, etc. may, for example, be designed with the aid of a three-dimensional CAD system.

[0034] The term "electron beam" as used herein in various embodiments refers to any charged particle beam. The sources of charged particle beam can include an electron gun, a linear accelerator and so on. As an alternative beam source any electromagnetic source may be used such as lasers with appropriate vawelength.

[0035] Vapor deposition inside a vacuum chamber may not only emanate from an additive manufacturing process but may also emanate from chemical vapor deposition (CVD), physical vapor deposition (PVD), laser ablation etc.

[0036] Figure 2 depicts an embodiment of a freeform fabrication or additive manufacturing apparatus 21 in which the inventive method and device according to the present invention may be implemented.

[0037] Said apparatus 21 comprising an electron beam gun 6; deflection coils 7; two powder hoppers 4, 14; a build platform 2; a build tank 10; a powder distributor 28; a powder bed 5; and a vacuum chamber 20.

[0038] The vacuum chamber 20 is capable of maintaining a vacuum environment by means of a vacuum system, which system may comprise a turbomolecular pump, a scroll pump, an ion pump and one or more valves which are well known to a skilled person in the art and therefore need no further explanation in this context. The vacuum system is controlled by a control unit 8.

[0039] The electron beam gun 6 is generating an electron beam which is used for melting or fusing together powder material provided on the build platform 2. At least a portion of the electron beam gun 6 may be provided in the vacuum chamber 20. The control unit 8 may be used for controlling and managing the electron beam emitted from the electron beam gun 6. At least one focusing coil (not shown), at least one deflection coil 7, an optional coil for astigmatic correction (not shown) and an electron beam power supply (not shown) may be electrically connected to said control unit 8. In an example embodiment of the invention said electron beam gun 6 generates a focusable electron beam with an accelerating voltage of about 15-60kV and with a beam power in the range

-3

of 3-1 OKw. The pressure in the vacuum chamber may be 10 ^" mbar or lower when building the three-dimensional article by fusing the powder layer by layer with the energy beam.

[0040] The powder hoppers 4, 14 comprise the powder material to be provided on the build platform 2 in the build tank 10. The powder material may for instance be pure metals or metal alloys such as titanium, titanium alloys, aluminum, aluminum alloys, stainless steel, Co-Cr alloys, nickel based superalloys etc.

[0041] The powder distributor 28 is arranged to lay down a thin layer of the powder material on the build platform 2. During a work cycle the build platform 2 will be lowered successively in relation to a fixed point in the vacuum chamber. In order to make this movement possible, the build platform 2 is in one embodiment of the invention arranged movably in vertical direction, i.e., in the direction indicated by arrow P. This means that the build platform 2 starts in an initial position, in which a first powder material layer of necessary thickness has been laid down. Means for lowering the build platform 2 may for instance be through a servo engine equipped with a gear, adjusting screws etc.

[0042] An electron beam may be directed over said build platform 2 causing said first powder layer to fuse in selected locations to form a first cross section of said three- dimensional article. The beam is directed over said build platform 2 from instructions given by the control unit 8. In the control unit 8 instructions for how to control the electron beam for each layer of the three-dimensional article is stored.

[0043] After a first layer is finished, i.e., the fusion of powder material for making a first layer of the three-dimensional article, a second powder layer is provided on said build platform 2. The second powder layer is preferably distributed according to the same manner as the previous layer. However, there might be alternative methods in the same additive manufacturing machine for distributing powder onto the work table. For instance, a first layer may be provided by means of a first powder distributor 28, a second layer may be provided by another powder distributor. The design of the powder distributor is automatically changed according to instructions from the control unit 8. A powder distributor 28 in the form of a single rake system, i.e., where one rake is catching powder fallen down from both a left powder hopper 4 and a right powder hopper 14, the rake as such can change design. [0044] After having distributed the second powder layer on the build platform, the energy beam is directed over said work table causing said second powder layer to fuse in selected locations to form a second cross section of said three-dimensional article. Fused portions in the second layer may be bonded to fused portions of said first layer. The fused portions in the first and second layer may be melted together by melting not only the powder in the uppermost layer but also remelting at least a fraction of a thickness of a layer directly below said uppermost layer.

[0045] Figure la depicts a schematic side view of a first example embodiment of a vacuum chamber 100 in which metallic vapours may be deposited according to the present invention.

[0046] Said vacuum chamber 100 may comprise at least one reflector 101 and a tube 105, where a first end of said tube 105 may be arranged inside said vacuum chamber 100 and provided for receiving electromagnetic radiation.

[0047] A second end of said tube 105 is extending inside said vacuum chamber 100. A central axis of said tube 105 may be slanted with respect to a surface of a substrate 103 which may be generating metallic vapour. Said reflector 101 may be arranged inside said vacuum chamber 100 to reflect electromagnetic radiation which is exiting from said second end of said tube 105 onto said surface of said substrate 103 which may be generating the metallic vapour.

[0048] In an example embodiment of the present invention the tube may be arranged in said vacuum chamber so that electromagnetic radiation emanating from any position of the substrate without being reflected by any part in said vacuum chamber is out of sight of the first end of said tube.

[0049] Out of sight means that radiation from the substrate 103 which is not reflected before reaching the second end of the tube is not visible for the first end of said tube. Electromagnetic radiation has to be reflected in order to reach the first end of the tube. This means that metal vapor will either deposit the reflector 101 or the inner wall of the tube 105 instead of a window of the vacuum chamber, a removable protective window in front of said window of said vacuum chamber or an illumination source or the illumination source as such at the first end of the tube. The tube is functioning as a shield for said window, removable protective window or illumination source. [0050] In vacuum conditions particles may move randomly inside a vacuum chamber. In an example embodiment of the present invention a cross section and length of the tube is chosen so that metal vapor particles have to be reflected at least twice inside the tube before reaching the window or illumination source. In still another example embodiment the number of reflections made by said metal vapor particle inside said tube is at least 5.

[0051] In still another example embodiment a cross section and a length of said tube is chosen so that when the pressure in said vacuum chamber is lower than 10 ^~3 mbar the transmission of said window, removable protecting glass or illumination source is >95% after lOOh of processing time with metal vapor being generated from said substrate.

[0052] In yet another example embodiment a cross section and a length of said tube is

-3 chosen so that when the pressure in said vacuum chamber is lower than 10 ^" mbar the transmission of said window, removable protecting glass or illumination source is >95% after lOOOh of processing time with metal vapor being generated from said substrate.

[0053] An illumination source 107 may be provided outside the vacuum chamber 100 at a position which enables electromagnetic radiation from said illumination device to enter the tube 105 via a waveguide in said vacuum chamber 100. Said wave guide may be a window or an optical fibre.

[0054] The reflector 101 may reflect the electromagnetic radiation emanating from the illumination source from said tube onto said substrate. The reflector may also reflect electromagnetic radiation emanating from said substrate in form of infrared radiation to the second end of said tube 105.

[0055] In another example embodiment of the present invention the illumination source may be combined with or replaced with a camera 177. In figure lg it is depicted an example embodiment with an illumination source 107 and a camera 177.

[0056] The camera 177 may be used to detect electromagnetic radiation which may be emitted from the electromagnetic source 107 and reflected by said reflector 101 onto the substrate 103. The electromagnetic radiation emanated from said source 107 may be transmitted via said tube 105 before being reflected by said reflector 101. Said electromagnetic radiation may be reflected back by said substrate 103 onto said reflector 101 via said tube 105 to said camera 177. The camera 177 is only illustrated in the example embodiment in figure lg. It is evident that the camera 177 may replace the illumination source 107 in all other shown embodiments or combined with the illumination source 107 in all other shown embodiments.

[0057] The camera 177 may also detect infrared radiation which is emanating from the substrate 103. As the substrate is generating metallic vapour it is hot. A hot surface may inter alia radiating infrared radiation. The camera may be configured to detect infrared radiation.

[0058] In another example embodiment said camera is provided with a filter device which may provide a first filter in front of the camera allowing only radiation which is emanating from the illumination source to be detected by the camera, i.e., a band pass filter with a predetermined wavelength range. Said filter device may change the filter to a second filter allowing only infrared radiation to be detected by the camera 177. In an alternative embodiment the filter may be a fixed filter allowing only radiation from the illumination source 107, only infrared radiation or no filter at all which allows all wavelength to be detected by the camera.

[0059] Said filter device may also be a protective removable window, i.e., a first function will be to transmit a predetermined range of wavelength and a second function will be to protect said camera, window of said vacuum chamber or illumination source from metal deposition. In another example embodiment said protective removable window has no filtering characteristics.

[0060] In another example embodiment said protective removable window is attached to said first end of said tube. The protective window and the tube may be exchanged as one unit. In still another example embodiment said protective removable window, said tube and said reflector 101 is arranged in one and the same unit, which means that when changing the protective removable window one is also changing at the same time the tube and the reflector.

[0061] In an example embodiment said tube may at its first end have a flange for attaching to a wall of said vacuum chamber where a window is arranged.

[0062] In another example embodiment said reflector 101 is arranged tiltable. This allows radiation from the illumination source 107 to incline on the substrate 103 with different angles. This may be useful in an image analysis. Topographic variations may better be separated from pure heat differences with several images taken with different angle of inclination of the illumination onto said substrate 103. The reflector may be tiltable so that the illumination may be scanned in an x-direction on the substrate 103, in a y-direction on the substrate 103, or in any direction having a component in both the x and y direction.

[0063] The metal vapour which may be generated from said surface of said substrate 103 may emanate from an additive manufacturing process, a physical vapour deposition process, a chemical vapour deposition process or a laser ablation process. An energy beam source 120 in the form of a laser beam source or an electron beam source may direct a high energy beam onto said surface of said substrate 103 for creating said metal vapour. Said substrate may be made of solid metal or powder metal.

[0064] The reflector 101 may be made of a metal material. The reflector 101 may be fiat, concave or convex. In an alternative embodiment a plurality of reflectors are arranged for directing the electromagnetic radiation from the exit (second end) of the tube 105 to said substrate 103. In still another example embodiment at least one of said reflectors are arranged movable or tiltable for changing a focus position of the electromagnetic radiation from said tube 105 on said substrate 103.

[0065] Figure lb depicts a portion of a vacuum chamber 100 according to a second example embodiment of the present invention. In figure lb it is depicted an illumination source 107, an optical fiber 130 and a tube 105. The optical fiber 130 is inserted into the vacuum chamber 100 via an opening in a wall of said vacuum chamber. An appropriate sealing member may be attached between the optical fiber and said opening in said vacuum chamber. Said illumination source may be arranged outside said vacuum chamber 100 and may illuminate a first end of said optical fiber 130 which may also be arranged outside said vacuum chamber 100. A second end of said optical fiber 130 may be arranged inside said vacuum chamber 100. Said second end of said optical fiber 130 may be inserted into the tube 105. The length of said optical fiber 130 in said vacuum chamber 100 may be shorter than said tube 105.

[0066] A central axis of said tube 105 may build an angle a with respect to said surface of said substrate 103. In a first example embodiment said angle a is 0° < a < 80° or 360° > a > 280°. In another example embodiment said angle a is 0° < a < 60° or 360° > a > 300°. In still another example embodiment said angle a is 0° < a < 45° or 360° > a > 315°. In still another example embodiment said angle a is 0° < a < 30° or 360° > a > 330°.

[0067] The length of the tube 105 may be between 3-50cm. In another example embodiment said length of the tube is 5-35cm. In still another example embodiment said length of the tube is 8-20cm.

[0068] The tube may be made of a metal material, a ceramic material or a plastic material. The tube may have a cross section in the form of a circle, ellipse, triangle, rectangle, polygon or any other shape.

[0069] The illumination device may be a source which is emitting white light or any light within a predetermined wavelength. The illumination device may also be a laser source.

[0070] In figure lc it is depicted a portion of a vacuum chamber 100 according to a third example embodiment of the present invention. In this embodiment the illumination source 107 is arranged outside the vacuum chamber 100. A window 110 is arranged over an opening in said vacuum chamber 100. The window 1 10 is attached on an inside wall of the vacuum chamber 100 with fastening means 160 which is pressing the window 1 10 to said vacuum chamber wall with screws 170. Between said window and said wall of said vacuum chamber there may be provide a sealing member 180. The window may be made of glass or plastic material. In front of said window a removable protective window may be provided which can be changed when its transmission is below a predetermined value for instance 95% of full transmission.

[0071] In figure Id it is depicted a portion of a vacuum chamber 100 according to a fourth example embodiment of the present invention. The only difference to the third embodiment is that the window 110 is attached to an outside wall of the vacuum chamber 100 instead of the inside wall as depicted in figure lc. It may also be possible to combine the embodiments in figure lc and Id, i.e., a first window attached to the inside wall of the vacuum chamber 100 and a second window attached to the outside wall of the vacuum chamber 100.

[0072] In case the illumination source 107 is arranged on the outside of the vacuum chamber 100, said tube, with its first end, may be attached to a wall of the vacuum chamber 100 where said window is provided for allowing electromagnetic radiation to radiate through said window to or from said tube 105. The reason for arranging the tube 105 to said wall is to hide said window for metal deposition. Metal vapor which may originate from the surface of said substrate 103 may deposit any surface inside said vacuum chamber.

[0073] However, if said surface is hidden, as in the case of the window which is hidden by said tube, the deposition on said window may be reduced to a minimum or totally eliminated. Factors that may influence the rate of deposition on said window hidden inside said tube 105 is the distance of said tube 105 to said substrate 103, the angle a and the length of the tube 105. If a is close to 0, i.e., in parallel with the substrate surface, a small amount of vapor or no vapor may be transported to the window inside the tube 105. Increasing the length of the tube 105 may also reduce the likelihood of deposition of metal vapor on said window. Decreasing an opening of the tube, i.e., the second end of the tube, is also reducing the possibility of vapor particles to be deposited on said window 110.

[0074] In figure le it is depicted a portion of a vacuum chamber 100 according to a fifth example embodiment of the present invention. In this embodiment the illumination source is arranged inside the vacuum chamber 100. The illumination source is further arranged inside said tube 105. The reason for arranging the illumination source inside the tube 105 is to hide said illumination source for metal deposition. Metal vapor which may originate from the surface of said substrate 103 may deposit any surface inside said vacuum chamber. However, if said surface is hidden, as in the case of the illumination source inside said tube the deposition may be reduced to a minimum totally eliminated. The factors that may influence the rate of deposition of said illumination source inside said tube 103 is the distance of said tube to said substrate 103, the angle a and the length of the tube. If a is close to 0, a small amount of vapor or no vapor may be transported to the illumination source 107 inside the tube 105. Increasing the length of the tube 105 may also reduce the likelihood of deposition of metal vapor on said illumination source. Decreasing an opening of the tube, i.e., the second end of the tube is also reducing the possibility of vapor particles to depositing on said illumination source 107.

[0075] In figure If it is depicted a portion of a vacuum chamber 100 according to a sixth example embodiment of the present invention. In this embodiment the reflector 101 and the tube 105 are arranged in a single unit. [0076] In another aspect of the invention it is provided a window arrangement for a vacuum chamber in which metallic vapors are deposited. The window arrangement comprises a window, at least one vacuum seal, at least one reflector and a tube. Said window and a first end of said tube are provided at an opening of a wall of the vacuum chamber and forming an air tight arrangement together with said at least one vacuum seal. Said second end of said tube may extend inside said vacuum chamber. A central axis of said tube may be slanted with respect to a surface of a substrate plate which is generating said metallic vapors. Said reflector may be arranged inside said vacuum chamber to reflect electromagnetic radiation which may be exiting from said second end of said tube onto said substrate surface which is generating metallic vapour or to reflect electromagnetic radiation which is exiting from said substrate surface to said second end of said tube. A source for generating electromagnetic radiation may be arranged outside said vacuum chamber.

[0077] In still another aspect of the present invention it is provided an apparatus for producing a part from powder, said apparatus comprising a powder distributing mechanism for providing at least a first layer of the powder at a target surface. Means for directing energy at selected positions of said first layer of powder corresponding to a first cross section of the part to fuse, wherein said fusion process is taking place in a vacuum chamber comprising at least one reflector and a tube, where a first end of said tube is arranged inside said vacuum chamber and provided for receiving electromagnetic radiation. A second end of said tube is extending inside said vacuum chamber and a central axis of said tube is slanted with respect to a surface of a substrate surface which is generating metallic vapour. Said reflector may be arranged inside said vacuum chamber to reflect electromagnetic radiation which is exiting from said second end of said tube onto said substrate surface which is generating metallic vapour or to reflect electromagnetic radiation which is exiting from said substrate surface to said second end of said tube.

[0078] The invention is not limited to the above -described embodiments and many modifications are possible within the scope of the following claims. Such modifications may, for example, involve using a different source of energy beam than the exemplified electron beam such as laser beam. Other materials than metallic powder may be used such as powder of polymers or powder of ceramics.