Method for manufacturing parabolic antenna and method for manufacturing mirror surface plate for parabolic antenna

Abstract

A method for manufacturing a mirror surface plate for a parabolic antenna according to the present disclosure is characterized by comprising: a step in which an original form (29) of a mirror surface plate for a parabolic antenna is fabricated through additive manufacturing in a directed energy deposition (DED) method using, as a filler material, a material for forming an intermetallic compound (16) at an interface with a mold material (9, 10, 11) serving as a mold of the mirror surface plate for a parabolic antenna when the material is dissolved in or mixed with the mold material (9, 10, 11), said material being different from the mold material (9, 10, 11); a step in which the original form (29) of the mirror surface plate for a parabolic antenna is peeled from the mold material (9, 10, 11) and released therefrom; and a step in which the original form (29) of the mirror surface plate for a parabolic antenna is subjected to mirror finishing.

Description

Method for manufacturing a parabolic antenna and method for manufacturing a mirror plate for a parabolic antenna

[0001] The present disclosure relates to a method for manufacturing a parabolic antenna and a method for manufacturing a mirror plate for a parabolic antenna.

[0002] Conventional methods for manufacturing mirror plates for parabolic antennas include forming a master mold for the mirror plate by injection molding or transfer molding, then depositing a metal film on the surface to form a mirror surface, or aluminum die casting. These methods require large injection molding machines or press molding machines for large parabolic antennas with diameters exceeding 1 meter, which can be cost-prohibitive for production volumes approaching a few to a dozen units.

[0003] As an alternative to the use of large injection molding machines or press molding machines, a method for producing a thick-walled parabolic antenna mirror plate by spraying metal onto a parabolic mirror plate matrix has been disclosed (see, for example, Patent Document 1). However, when a metal mold is used as the matrix, this method requires that the metal spraying be performed at a low temperature to prevent reaction with the matrix, i.e., alloying. However, because the metal sprayed film thickness is thin, if the film thickness is on the order of millimeters, the temperature rises during the process, causing a reaction with the matrix, making it difficult to release the metal sprayed mirror plate from the matrix. Furthermore, when a wooden mold is used as the matrix, the large and thick mirror plate produced can easily peel off from the matrix during spraying due to stress.

[0004] JP 51-83451

[0005] To avoid these problems, the inventors have conducted extensive research into applying a metal additive manufacturing (AM) manufacturing system called Directed Energy Deposition (DED), which is suitable for manufacturing large objects and has a fast manufacturing time, to the manufacture of parabolic antenna mirror plates. The DED system uses wire or metal powder as the raw material and deposits the raw material in the required locations by welding.

[0006] However, in additive manufacturing using the DED method, the surface roughness of the formed object is on the order of mm, so when manufacturing objects that require a surface roughness at the μm level, such as mirror plates for parabolic antennas, there is a problem in that the amount of grinding required in the subsequent mirror finishing process to achieve the required surface roughness is large, which is cost-inefficient.

[0007] The manufacturing method of a parabolic antenna mirror plate according to the present disclosure is characterized by comprising the steps of: forming a prototype of the parabolic antenna mirror plate by additive manufacturing using a DED (Directed Energy Deposition) method in which a filler material is used for a mold material that will serve as the mold for the parabolic antenna mirror plate, the filler material being a material that is different from the mold material and that forms an intermetallic compound at the interface with the mold material when dissolved or mixed with the mold material; peeling the prototype of the parabolic antenna mirror plate from the mold material and releasing the prototype of the parabolic antenna mirror plate from the mold material; and mirror-finishing the prototype of the parabolic antenna mirror plate.

[0008] In addition, the method for manufacturing a parabolic antenna according to the present disclosure is characterized by comprising the steps of: forming a prototype of a parabolic antenna mirror plate by additive manufacturing using a DED method, in which a filler metal is used for a mold material that serves as a mold for the parabolic antenna mirror plate, and the filler metal is a material that is different from the mold material and that forms an intermetallic compound at the interface with the mold material when dissolved or mixed with the mold material; forming a framework that supports the prototype of the parabolic antenna mirror plate integrally with the prototype of the parabolic antenna mirror plate by additive manufacturing using the DED method, to form the prototype of the parabolic antenna; peeling the prototype of the parabolic antenna from the intermetallic compound and releasing the prototype of the parabolic antenna from the mold material; and mirror-finishing the prototype of the parabolic antenna.

[0009] According to the present disclosure, it is possible to manufacture a parabolic antenna and a mirror plate for a parabolic antenna in which the amount of grinding is reduced in the mirror finishing process.

[0010] A perspective view of a mold 9 of the original shape of a parabolic antenna mirror plate according to the first embodiment. A cross-sectional view of the mold 9 of the original shape of a parabolic antenna mirror plate according to the first embodiment, taken along the cross-sectional line II-II shown in FIG. 1. An enlarged cross-sectional view showing how a prototype 29 of a parabolic antenna mirror plate is additionally manufactured on the mold 9 according to the first embodiment. A perspective view showing how a prototype 29 of a parabolic antenna mirror plate is being additionally manufactured on the mold 9 according to the first embodiment. Cross-sectional view of original 29 Cross-sectional view showing the state in which original 29 of the parabolic antenna mirror plate has been released from the mold material 9 in embodiment 1 Perspective view showing a modified example of how original 29 of the parabolic antenna mirror plate is released from the mold material 9 in embodiment 1 Enlarged cross-sectional view of original 29 of the parabolic antenna mirror plate released from the mold material 9 in embodiment 1 Cross-sectional view of original 59 of the parabolic antenna mirror plate according to a comparative example Enlarged cross-sectional view of original 59 of the parabolic antenna mirror plate according to a comparative example 3 is a cross-sectional view of a prototype 31 of a parabolic antenna formed in the third embodiment; FIG. 4 is a cross-sectional view showing how the prototype 31 of the parabolic antenna is released from the mold 9 in the second embodiment; FIG. 5 is a cross-sectional view of the prototype mold 10 of the parabolic antenna mirror plate in the third embodiment; FIG. 6 is a perspective view of the TIG weld bead 40 formed on the mold 10 in the third embodiment; and FIG. 7 is a cross-sectional view showing how the MIG weld bead 42 is formed along the TIG weld bead 40 on the mold 10 in the third embodiment. 16A and 16B are enlarged perspective views of the original shape 11 of the parabolic antenna mirror plate according to the fourth embodiment;

[0011] The details of the embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts will be denoted by the same reference numerals, and redundant explanations will not be repeated. Note that the embodiments described below are merely examples, and the scope of the present disclosure is not limited to the embodiments described below.

[0012] Embodiment 1. A method for manufacturing a mirror plate for a parabolic antenna according to embodiment 1 will be described. The mirror plate for a parabolic antenna manufactured in this embodiment is a sub-reflector of a Cassegrain antenna, which is a type of parabolic antenna. Note that the type and form of the parabolic antenna manufactured in this disclosure are not limited to this. The manufacturing method according to this embodiment includes steps A1 to A3. Steps A1 to A3 will be described below.

[0013] <Step A1: Step of forming a prototype of a parabolic antenna mirror plate> First, a step of forming a prototype of a parabolic antenna mirror plate is carried out. Hereinafter, the details of this step will be described with reference to FIGS.

[0014] FIG. 1 is a perspective view of a mold 9 for the original parabolic antenna mirror plate according to the first embodiment. A concave surface is formed in the center of the mold 9, which will serve as the mold for the original parabolic antenna mirror plate 29. The mold 9 has a bowl-shaped recess, and the original parabolic antenna mirror plate 29 is manufactured by additive manufacturing using the DED method in this portion. Here, the original parabolic antenna mirror plate 29 is a shaped object having the shape of a parabolic antenna mirror plate, which becomes a parabolic antenna mirror plate by mirror-finishing the surface on the mirror side. The mold 9 is made of a material with low surface roughness. Specifically, a steel material that has been mirror-finished to a surface roughness of approximately 0.1 to 5 μm may be used. In this embodiment, hot-rolled steel SS400 (JIS standard) is used for the mold 9. The dimensions of the recess in the mold 9 were adjusted to a diameter of 1.2 m and a depth of 0.4 m.

[0015] As will be explained later, the mold 9 is made by connecting a plurality of work plates 19 with fixing jigs 21 and attaching hook hooks 20. For convenience, the work plates 19, fixing jigs 21, and hook hooks 20 are omitted from the illustration of the mold 9 in Fig. 1. Unless otherwise specified, the same applies to the other drawings.

[0016] FIG. 2 is a cross-sectional view of the original mold 9 of the parabolic antenna mirror plate according to the first embodiment, taken along the line II-II in FIG. 1 . As described above, the mold 9 was fabricated by connecting multiple processed plates 19 with fixtures 21 and attaching hooks 20. Specifically, due to dimensional constraints, it would be difficult to create the mold 9 by cutting out a single metal block from the perspective of material procurement and machining. Therefore, the processed plates 19, which were machined from 100 mm thick plate material, were connected with fixtures 21. Furthermore, the hooks 20 were attached to the mold 9 so that the mold 9 could be transported by hanging it from a hook using a crane. A zinc-based rust inhibitor was applied to the surface of the mold 9 with a brush to facilitate welding. The zinc-based rust inhibitor applied to the surface of the mold 9 was then thoroughly dried. Instead of using a zinc-based rust inhibitor, a hot-dip galvanizing process may be performed.

[0017] 3 is an enlarged cross-sectional view showing additive manufacturing of a prototype 29 of a parabolic antenna mirror plate on a mold 9 in the first embodiment. In this embodiment, a DED type additive manufacturing device 200 was used to form the prototype on the concave surface of the mold 9. Hereinafter, for convenience, the DED type additive manufacturing device 200 will be simply referred to as the additive manufacturing device 200. The additive manufacturing device 200 used is a device that performs additive manufacturing using the DED type with a laser light source.

[0018] As shown in FIG. 3 , the additive manufacturing apparatus 200 includes a shaping head 1. A fiber laser oscillator 23, a near-infrared light source, is connected to the shaping head 1 via an optical fiber 27. The laser light emitted by the fiber laser oscillator 23 is guided to a conduit within the shaping head 1 via the optical fiber 27, condensed from the center of the shaping head 1, and irradiated onto the surface of the mold material 9. The dotted arrows in the figure represent the irradiated laser light. Simultaneously with the irradiation of the laser light at the shaping position, a filler wire 3 is fed from the side of the shaping head 1 to form a weld bead 39, thereby performing additive manufacturing. The wire 3 is fed to the shaping position by feeding the wire 3 wound around a bobbin 2 using a wire feeder / straightener 26. A 1.2 mm diameter A5183 (JIS standard) aluminum welding wire was used as the wire 3. The shaping conditions were a laser power of 2 kW and an Ar gas flow rate of 10 L / min. In addition, a cooling water pipe 24 is connected to the modeling head 1 to cool it, and cooling water is circulated through the cooling water pipe 24 by a chiller 22. In addition, a shielding gas spraying unit 25 is connected to the modeling head 1, and a shielding gas is supplied from the shielding gas spraying unit 25 to suppress oxidation of the model during modeling. Ar gas was used as the shielding gas. Additive manufacturing was performed by welding a filler metal wire 3 to the model material 9 via a zinc-based rust inhibitor applied to the surface of the model material 9.

[0019] Although not shown in FIG. 3 , an intermetallic compound 16 is formed at the interface between the mold material 9 and the weld bead 39. The "weld bead" referred to here refers to a weld mark formed by build-up welding using the raw material wire 3 (or metal powder). This build-up portion 39 is shaped by additive manufacturing using the DED method. In order to form this intermetallic compound 16, the filler metal, i.e., the material of the wire 3, is a material that is different from the mold material 9 and that forms the intermetallic compound 16 at the interface with the mold material 9 when dissolved or mixed with the mold material 9. In this embodiment, since the mold material 9 is Fe and the filler metal is Al, FeAl ３ and Fe ２ Al ５Intermetallic compounds 16 such as the above are formed. Intermetallic compounds generally have a higher Vickers hardness and are more brittle than the original metal, making them prone to cracking. That is, the intermetallic compounds 16 have a higher Vickers hardness and are more brittle than the mold material 9 and the weld bead 39, making them prone to cracking. To form such intermetallic compounds 16, welding conditions such as the welding temperature and the amount of filler metal supplied can be adjusted. The zinc-based rust inhibitor applied to the mold material 9 is vaporized during welding and is discharged to the outside with the flow of shielding gas supplied simultaneously with welding.

[0020] 4 is a schematic perspective view showing the process of additively manufacturing a prototype 29 of a parabolic antenna mirror plate on a mold 9 in the first embodiment. For convenience, the additive manufacturing apparatus 200 is not shown. As shown in FIG. 4, arc-shaped weld beads 39 were formed from the outermost periphery of the concave surface of the mold 9 toward the inside, so as to form the parabolic surface of the parabolic antenna mirror plate. At this time, the weld beads 39 were not continuously overlapped, but were formed into arc-shaped shapes with gaps between them.

[0021] Furthermore, the formation of the weld bead 39 was continued, and when the weld bead 39 reached the bottom center of the parabolic surface of the mold material 9, it returned to the outer periphery and continued forming in an arc to fill in the gap. Using this method, it is possible to prevent the parabolic surface from being locally overheated and causing peeling during forming. Then, the weld bead 39 was gradually connected until the entire parabolic surface of the mold material 9 was filled with the weld bead 39, thereby forming the original shape 29 of the parabolic antenna mirror plate.

[0022] 5 is a cross-sectional view of a prototype 29 of a parabolic antenna mirror plate formed on a mold 9 in the first embodiment. The prototype 29 of the parabolic antenna mirror plate is formed along the concave surface of the mold 9 via an intermetallic compound 16. Of the surface of the prototype 29 of the parabolic antenna mirror plate, the side in contact with the intermetallic compound 16 becomes the mirror surface of the parabolic antenna. In addition, the intermetallic compound 16 is formed over the entire welding interface between the mold 9 and the prototype 29 of the parabolic antenna mirror plate.

[0023] As mentioned in the explanation of Fig. 3, this intermetallic compound 16 is formed by melting or mixing the mold material 9 and the filler material. In this embodiment, since the mold material 9 is Fe and the filler material is Al, FeAl is present at the welding interface between the mold material 9 and the base 29 of the parabolic antenna mirror plate. ３ and Fe ２ Al ５ The intermetallic compound 16 is formed. The intermetallic compound 16 can be formed by adjusting welding conditions such as the welding temperature and the amount of filler metal supplied.

[0024] The intermetallic compound 16 is determined by the combination of the mold material 9 and the filler material. For example, when the mold material 9 is Fe and the filler material is Al, Fe ３ Al, FeAl, FeAl ２ , Fe ２ Al ５ , FeAl ３ , Fe ２ Al ６ , Fe ２ Al ９ Various Fe-Al based intermetallic compounds 16 such as these are formed at the weld interface. Many of these intermetallic compounds 16 have higher Vickers hardness and greater brittleness than the original metals Fe and Al. Among these, FeAl ３ and Fe ２ Al ５ However, the intermetallic compounds 16 have a higher Vickers hardness and are more brittle than the original metal. The type and composition ratio of the intermetallic compounds 16 formed can be adjusted by adjusting welding conditions such as the welding temperature and the amount of filler metal supplied.

[0025] By changing the combination of the mold material 9 and the filler material, it is possible to form intermetallic compounds 16 other than Fe-Al-based compounds. For example, when Ti or Ni is used for the mold material 9 and Al is used for the filler material, Ti-Al-based or Ni-Al-based intermetallic compounds 16 can be formed. When Ni is used for the mold material 9 and Ti is used for the filler material, Ni-Ti-based intermetallic compounds 16 can be formed. Intermetallic compounds generally have a higher Vickers hardness and are more brittle than the original metals, making them prone to cracking. In other words, the intermetallic compound 16 has a higher Vickers hardness and is more brittle than the original parabolic antenna mirror plate 29 made of the mold material 9 and the filler material, making them prone to cracking.

[0026] The thickness of the intermetallic compound 16 affects the bonding strength at the interface. The thicker the intermetallic compound 16, the lower the bonding strength at the interface, and the more likely cracks are to occur in the intermetallic compound 16. On the other hand, the thinner the intermetallic compound 16, the higher the bonding strength at the interface. Therefore, in order to release the original form 29 of the parabolic antenna mirror plate from the mold material 9 in a later process, it is preferable that the intermetallic compound 16 is thick. Specifically, it is preferable that the thickness of the intermetallic compound 16 is 1 μm or more. The thickness of the intermetallic compound 16 can be adjusted by changing welding conditions such as the welding time and the amount of filler metal supplied.

[0027] <Step A2: Step of Releasing the Original Form of the Parabolic Antenna Mirror Plate> Next, a step of releasing the original form of the parabolic antenna mirror plate is carried out. The original form 29 of the parabolic antenna mirror plate formed in step A1 is released from the mold material 9. The details of this step will be described below with reference to FIGS. 6 and 7 .

[0028] 6 is a cross-sectional view showing a state in which the original 29 of the parabolic antenna mirror plate has been released from the mold material 9 in the first embodiment. The original 29 of the parabolic antenna mirror plate has been completely released from the mold material 9. The original 29 of the parabolic antenna mirror plate is released from the mold material 9 by peeling it off from the mold material 9 via the intermetallic compound 16 (not shown in FIG. 6 ) present at the interface with the mold material 9. The intermetallic compound 16 is brittle, and cracks occur within the layer of the intermetallic compound 16, causing the original 29 of the parabolic antenna mirror plate to be released from the mold material 9. Depending on the extent of the cracks, some of the intermetallic compound 16 may remain attached to the mold material 9 side of the original 29 of the parabolic antenna mirror plate.

[0029] As a means for releasing the original 29 of the parabolic antenna mirror plate from the mold 9, there is a method of applying an impact or vibration to the interface between the mold 9 and the parabolic antenna mirror plate. In this way, the original 29 of the parabolic antenna mirror plate is peeled off from the mold 9. In this embodiment, a mechanical impact is applied using a mallet. The impact may be a thermal shock or the like. Vibration may be applied instead of an impact, for example, ultrasonic vibration. The impact or vibration does not necessarily have to be applied directly to the interface between the mold 9 and the original 29 of the parabolic antenna mirror plate; it may be applied indirectly to a location other than the interface as long as the impact or vibration is applied to the interface.

[0030] In addition to applying impact or vibration, for example, the mold material 9 may be fixed with an anchor and the original form 29 of the parabolic antenna mirror plate may be pulled little by little to cause the mold to be released. Alternatively, the mold material 9 and the original form 29 of the parabolic antenna mirror plate may be heated and the mold may be released by the difference in the amount of thermal expansion resulting from the difference in the thermal expansion coefficients of the two. Specifically, a method of placing the mold material 9 in a furnace or a method of placing a heat source to cause localized separation from the mold material 9 while gradually moving the position of the heat source to promote the separation may be considered.

[0031] 7, the original form 29 of the parabolic antenna mirror plate may be released by removing the fixing jig 21 that has been holding the mold material 9 and removing the processing plate 19, which is a component of the mold material 9, from the outside. In this way, a mechanical shock can be applied to the vicinity of the location where the original form 29 of the parabolic antenna mirror plate is to be peeled off from the mold material 9, allowing for more efficient release.

[0032] FIG. 8 is an enlarged cross-sectional view of a prototype 29 of a parabolic antenna mirror plate released from the mold 9 in embodiment 1. For the prototype 29 of the parabolic antenna mirror plate shown in FIG. 8, surface 18a is the surface released from the mold 9. That is, surface 18a is the surface that will become the mirror surface of the parabolic antenna mirror plate. On the other hand, surface 18b is the surface that does not contact the mold 9 during molding. That is, surface 18b is the surface that will become the opposite side of the mirror surface of the parabolic antenna mirror plate. The surface roughness of surface 18a is smaller than that of surface 18b. Specifically, the variation in the unevenness of surface 18a was approximately 50 to 100 μm, and the variation in the unevenness of surface 18b was approximately 0.5 to 1.5 mm.

[0033] As shown in FIG. 8 , the surface roughness of surface 18a is smaller than that of surface 18b. The reason for this is as follows. First, because surface 18a is the surface released from mold member 9, the surface roughness of surface 18a depends on the surface roughness of mold member 9. Furthermore, as described with reference to FIG. 1 , a mold member 9 with a low surface roughness is used. Therefore, the surface roughness of surface 18a is also small. Here, intermetallic compounds 16 are present between surface 18a and the surface of mold member 9. However, the thickness of intermetallic compounds 16 is generally on the order of μm. Even if the intermetallic compounds 16 remain attached to surface 18a when the original 29 of the parabolic antenna mirror plate is released from mold member 9, the effect of the intermetallic compounds 16 on the surface roughness of surface 18a is small, and the surface roughness of surface 18a remains small. On the other hand, surface 18b opposite surface 18a is the surface that has not been released from mold member 9, i.e., the surface that did not come into contact with mold member 9 when the original 29 of the parabolic antenna mirror plate was formed. Generally, the surface of an object manufactured by additive manufacturing without contact with other members such as mold materials has a large surface roughness. Therefore, the surface roughness of surface 18a is large. Therefore, the surface roughness of surface 18a is smaller than the surface roughness of surface 18b.

[0034] <Step A3: Step of Mirror-Finishing the Original Form of the Parabolic Antenna Mirror Plate> Finally, a step of mirror-finishing the original form of the parabolic antenna mirror plate is carried out. The original form 29 of the parabolic antenna mirror plate released in step A2 is mirror-finished.

[0035] The parabolic antenna mirror plate according to this embodiment is manufactured by mirror-finishing the mirror-side surface 18a of the original parabolic antenna mirror plate 29. The mirror-finishing method may be cutting using a lathe or milling machine, polishing using an abrasive, or the like, and any method can be used as long as it can achieve the required surface roughness of the mirror surface. <Effect 1A>

[0036] 8, the surface 18a on the specular side has a smaller surface roughness than the surface 18b on the opposite side. Therefore, the original 29 of the parabolic antenna specular plate shaped in this embodiment requires less grinding when grinding the specular surface to the required order.

[0037] Next, a comparison with the surface of a prototype 59 of a parabolic antenna mirror plate according to a comparative example will be described. The prototype 59 of a parabolic antenna mirror plate according to the comparative example is formed by additive manufacturing using the DED method on a flat base plate 57, as shown in FIG. 9 . That is, the prototype 59 of the parabolic antenna mirror plate is formed without contacting other components except for the areas that come into contact with the base plate 57. After being formed, the prototype 59 of the parabolic antenna mirror plate is peeled off from the base plate 57 by electrical discharge machining or machining. The difference from this embodiment is that the prototype 59 of the parabolic antenna mirror plate is additively manufactured on a flat base plate 57, rather than on a mold material 9 of the prototype of the parabolic antenna mirror plate.

[0038] FIG. 10 is an enlarged cross-sectional view of a prototype 59 of a parabolic antenna mirror plate according to a comparative example. As described above, the prototype 59 of the parabolic antenna mirror plate is formed on a base plate 57 by additive manufacturing using the DED method. However, the prototype is formed without contacting other components except for the portion that contacts the base plate 57. Surface 58a is the surface that becomes the mirror surface of the parabolic antenna mirror plate, the portion that does not contact the base plate 57 during fabrication. Surface 58b is the surface opposite the mirror surface. The surface roughness of surface 58a is approximately the same as that of surface 58b. In other words, unlike the present embodiment, the surface roughness of the mirror surface side is approximately the same as that of the opposite side. Note that when the fabrication conditions, such as laser output, are the same as those of the present embodiment, the variation in the unevenness of surfaces 58a and 58b is approximately 0.5 to 1.5 mm.

[0039] On the other hand, as explained in Fig. 8, the specular-side surface 18a of the original 29 of the parabolic antenna mirror plate according to this embodiment has a smaller surface roughness than the opposite surface 18b. Therefore, when the shaping conditions, such as the laser output, are the same, the specular-side surface 18a of the original 29 of the parabolic antenna mirror plate according to this embodiment shown in Fig. 8 has a smaller surface roughness than the specular-side surface 58a of the original 59 of the parabolic antenna mirror plate according to the comparative example shown in Fig. 10. Comparing the numerical values ​​of the surface roughness mentioned above, the variation in the irregularities of the specular-side surface 58a of the original 59 of the parabolic antenna mirror plate is about 0.5 to 1.5 mm, whereas the variation in the irregularities of the specular-side surface 18a of the original 29 of the parabolic antenna mirror plate is about 50 to 100 µm.

[0040] Therefore, the original form 29 of the parabolic antenna mirror plate according to this embodiment requires less grinding when grinding the surface roughness of the mirror surface to the required order than the original form 59 of the parabolic antenna mirror plate according to the comparative example. Therefore, the manufacturing method of the parabolic antenna mirror plate according to this embodiment can reduce the amount of grinding in the mirror finishing process.

[0041] Second Embodiment. A method for manufacturing a parabolic antenna according to the second embodiment will be described. The parabolic antenna according to the present embodiment is manufactured by molding a framework 30 integrally with the original parabolic antenna mirror plate 29, which was manufactured in step A1 of the first embodiment, before releasing it in step A2, to form a parabolic antenna original 31, and then releasing the molded parabolic antenna original 31 and polishing it to a mirror finish. The manufacturing method according to the present embodiment includes steps B1 to B4. Steps B1 to B4 will be described below.

[0042] <Step B1: Step of forming a prototype of a parabolic antenna mirror plate> First, a step of forming a prototype of a parabolic antenna mirror plate is carried out. This step is the same as step A1 in embodiment 1. That is, a prototype 29 of a parabolic antenna mirror plate is formed on a mold 9.

[0043] <Step B2: Step of additively manufacturing a framework on the prototype of the parabolic antenna mirror plate> Next, a step of additively manufacturing a framework on the prototype of the parabolic antenna mirror plate is carried out. In this step, a framework 30 that supports the prototype 29 of the parabolic antenna mirror plate is formed integrally with the prototype 29 of the parabolic antenna mirror plate formed in step B1 by additive manufacturing using the DED method, to form the prototype 31 of the parabolic antenna. The details of this step will be described below with reference to FIG. 11.

[0044] FIG. 11 is a cross-sectional view of a parabolic antenna prototype 31 formed on a mold 9 in the second embodiment. The parabolic antenna prototype 31 is manufactured by integrally molding a framework 30 that supports the parabolic surface from the backside of the parabolic antenna mirror plate prototype 29 with the parabolic antenna mirror plate prototype 29 before releasing the parabolic antenna mirror plate prototype 29 from the mold 9. Here, the parabolic antenna prototype 31 is a shaped object having the shape of a parabolic antenna, which becomes a parabolic antenna by applying a mirror finish to the mirror surface side. The parabolic antenna prototype 31 is manufactured by forming and welding the framework 30 to the formed parabolic antenna mirror plate prototype 29 using additive manufacturing with the DED method. The formation of the framework 30 was performed continuously from the formation of the parabolic antenna mirror plate prototype 29 without changing the welding conditions. The framework 30 may be shaped to have a shape that is topology-optimized for the parabolic antenna reflector plate.

[0045] In this way, by continuously and integrally forming the base 29 of the parabolic antenna mirror plate and the framework 30, it is possible to form the base 31 of the parabolic antenna, unlike in the first embodiment.

[0046] <Step B3: Step of Releasing the Parabolic Antenna from its Original Form> Next, a step of releasing the parabolic antenna from its original form is carried out. The parabolic antenna original form 31 formed in step B2 is released from the mold material 9. The details of this step will be described below with reference to FIG. 12 .

[0047] 12 is a cross-sectional view showing the process of releasing the parabolic antenna prototype 31 from the mold 9 in the second embodiment. A hook 33 is attached to the framework 30 of the parabolic antenna prototype 31, and a slight upward force is applied by a wire rope 32 connected to the hook 33. The arrow in the figure indicates the direction of the force being applied. Furthermore, a mechanical impact is applied to the interface between the mold 9 and the parabolic antenna prototype 31 using a wooden mallet. In this way, the mold 9 and the parabolic antenna prototype 31 are peeled off from the intermetallic compound 16 at the interface, and the parabolic antenna prototype 31 is completely released from the mold 9.

[0048] Although a mechanical shock is applied in this embodiment, the means of applying the shock in this disclosure is not limited, and for example, a thermal shock may be applied. Furthermore, instead of a shock, vibration may be applied, such as ultrasonic vibration. The application of the shock or vibration does not necessarily have to be directly applied to the interface between the mold 9 and the parabolic antenna prototype 31, and may be indirectly applied to a location other than the interface as long as the shock or vibration is applied to the interface.

[0049] In addition to applying impact or vibration, for example, the mold material 9 may be fixed with an anchor and the parabolic antenna prototype 31 may be pulled little by little to cause the mold to separate. Alternatively, the mold material 9 and the parabolic antenna prototype 31 may be heated and the mold may be separated by the difference in the amount of thermal expansion resulting from the difference in the thermal expansion coefficients of the two. Specifically, a method of placing the mold material 9 in a furnace or a method of placing a heat source to cause localized separation from the mold material 9 while gradually moving the position of the heat source may be considered to promote the separation.

[0050] <Step B4: Step of Mirror-Finishing the Parabolic Antenna Prototype> Finally, the parabolic antenna prototype is mirror-finished. The parabolic antenna prototype 31 released in step B3 is mirror-finished.

[0051] The surface of the mirror side of the parabolic antenna prototype 31 is subjected to a mirror finish. The mirror finish may be achieved by cutting using a lathe or milling machine, polishing using an abrasive, or any other method as long as the required surface roughness of the mirror surface can be achieved. In this manner, the parabolic antenna according to this embodiment is manufactured.

[0052] <Effect 1B> In this embodiment, unlike in embodiment 1, the base form 29 of the parabolic antenna mirror plate and the framework 30 are continuously and integrally formed to form the base form 31 of the parabolic antenna. Therefore, in this embodiment, unlike embodiment 1, it is possible to manufacture a parabolic antenna rather than a parabolic antenna mirror plate. On the other hand, in order to complete the parabolic antenna in embodiment 1, after manufacturing the parabolic antenna mirror plate in this embodiment, it is necessary to separately connect or integrally form a framework that supports the parabolic surface from behind.

[0053] <Effect 2B> As described in the first embodiment, the specular surface 18a of the original parabolic antenna mirror plate 29 has a smaller surface roughness than the specular surface 58a of the original parabolic antenna mirror plate 59 according to the comparative example. As described in FIG. 8 , the specular surface 18a of the original parabolic antenna mirror plate 29 is the surface released from the mold 9, which has a small surface roughness. Furthermore, the specular surface 18a of the original parabolic antenna mirror plate 29 is also the specular surface of the original parabolic antenna 31. This is because the original parabolic antenna 31 is formed by integrally molding the framework 30 that supports the parabolic surface from behind with the original parabolic antenna mirror plate 29. Therefore, the original parabolic antenna 31 formed in this embodiment requires less grinding when grinding the specular surface to the required surface roughness. Therefore, in the method for manufacturing a parabolic antenna according to this embodiment, the amount of grinding can be reduced in the mirror finishing step.

[0054] Third Embodiment. A method for manufacturing a parabolic antenna according to the third embodiment will be described. In this embodiment, a different type of DED additive manufacturing device 201 and a TIG welder 300 are used, rather than the additive manufacturing device 200 used in the first and second embodiments. While the additive manufacturing device 200 used in the first and second embodiments performs DED additive manufacturing using a laser light source, the additive manufacturing device 201 used in this embodiment performs DED additive manufacturing using MIG (Metal Inert Gas) welding, a type of arc welding. First, TIG (Tungsten Inert Gas) welding is performed on the mold 10 using the TIG welder 300, and then MIG welding is performed using the additive manufacturing device 201 along the formed TIG weld bead 40, thereby forming the prototype 31 of the parabolic antenna. The manufacturing method according to this embodiment includes steps C1 to C4. Steps C1 to C4 will be described below.

[0055] <Step C1: Step of Forming a Prototype of a Parabolic Antenna Mirror Plate> First, a step of forming a prototype 29 of a parabolic antenna mirror plate is carried out. Hereinafter, the details of this step will be described with reference to FIGS.

[0056] FIG. 13 is a cross-sectional view of a prototype mold 10 for a parabolic antenna mirror plate according to the third embodiment. The mold 10 is a mold for a prototype 29 of a parabolic antenna mirror plate. The mold 10 has a bowl-shaped recess. Unlike the mold 9 according to the first and second embodiments, the mold 10 was manufactured by casting, rather than by fixing multiple processed plates 19 with a fixture 21. The mold 10 was made of stainless steel casting SCS13. The recess dimensions were adjusted to a diameter of 1.1 m and a depth of 0.35 m. The parabolic surface side of the mold 10 was ground to achieve a surface roughness with a surface irregularity variation of approximately 0.1 to 5 μm. Similar to the mold 9, the mold 10 uses a mold with a small surface roughness.

[0057] FIG. 14 is a cross-sectional view showing the formation of a TIG weld bead 40 on a molded member 10 in the third embodiment. The surface of the molded member 10 to be TIG welded was previously roughened using a wire brush. Furthermore, because the stainless steel casting SCS13 (JIS standard), from which the molded member 10 is made, has a strong oxide film, flux was applied to the roughened surface. As shown in FIG. 14 , the TIG weld bead 40 was formed by melting a welding rod 38 (filler material) and depositing it using a TIG welding machine 300. The welding rod 38 was an aluminum welding rod A5183 (JIS standard) with a diameter of 2.4 mm. A tungsten electrode 37 was attached to one input terminal of an arc welding power source 35 via a conductor 34, and a ground electrode 36 was attached to the other input terminal via a conductor 34 and grounded to the molded member 10. The current was adjusted to approximately 100 to 120 A, and while holding the welding rod 38 by hand, an arc was generated near the tungsten electrode 37 to form a TIG weld bead 40. The arc is indicated by a triangle surrounded by a dotted line in the figure. A shielding gas sprayer 25 was connected to the tungsten electrode 37, and during welding, shielding gas was supplied from the shielding gas sprayer 25 to suppress oxidation of the TIG weld bead 40. Ar gas was used as the shielding gas.

[0058] In TIG welding, a filler metal is manually supplied to a molten pool (melt pool) on the surface of the base metal melted by an arc, so sufficient heat input is required, making it easy for the molded member 10 to melt at the weld. Therefore, as shown in FIG. 14 , a TIG weld bead 40 is formed by engraving a certain level into the molded member 10. This engraving depth is approximately several millimeters, typically exceeding 3 mm. This differs from the laser welding used in embodiments 1 and 2. Laser welding can control the heat input energy lower than TIG welding, making it possible to limit the engraving depth to approximately 100 μm. On the other hand, TIG welding has high energy, making it easy to weld any type of molded member. For example, even if the molded member 10 is made of Ti, which has a higher melting point than Fe, TIG welding allows for easier adjustment of the wattage and feed rate than laser welding, making it easy to weld.

[0059] 15 is a perspective view showing TIG weld beads 40 formed on a mold 10 in the third embodiment. The TIG weld beads 40 are formed at intervals in a grid pattern on the parabolic surface of the mold 10. Because TIG welding uses high energy, the mold 10 is sufficiently melted, and an intermetallic compound 16 is formed between the mold 10 and the TIG weld bead 40. At this time, the intermetallic compound 16 is formed over the entire weld interface, as described in FIG. 5.

[0060] FIG. 16 is an enlarged perspective view showing the formation of a MIG weld bead 42 along the TIG weld bead 40 on the mold member 10 in the third embodiment. Using an additive manufacturing device 201, the MIG weld bead 42 was formed on the mold member 10 at intervals along the TIG weld bead 40 described in FIG. 15 . The additive manufacturing device 201 is a type of device that performs DED additive manufacturing using MIG welding, a type of arc welding. Unlike TIG welding, MIG welding automatically supplies the filler material by the additive manufacturing device 201. For this reason, MIG welding can be controlled to reduce heat input compared to TIG welding, and the amount of engraving into the mold member 10 is small, approximately 1 mm. Because the MIG weld bead 42 is weakly bonded to the mold member 10, it is preferable to form it along the TIG weld bead 40, which is relatively strongly bonded to the mold member 10.

[0061] As shown in FIG. 16 , the additive manufacturing apparatus 201 has a MIG welding head 41. A filler wire 3 was fed from the center of the MIG welding head 41, and welding was performed by an arc generated between the wire 3 and the mold material 10. The arc is indicated by a triangle surrounded by a dotted line in the figure. The wire 3 was fed to the manufacturing position by feeding the wire 3 wound around a bobbin 2 using a wire feeder / straightener 26. The MIG welding head 41 was attached to one input terminal of the arc welding power source 35 of the additive manufacturing apparatus 201 via a conductor 34, and a ground electrode 36 was attached to the other input terminal via a conductor 34 and grounded to the mold material 10. As in the first embodiment, a 1.2 mm diameter A5183 (JIS standard) aluminum welding wire was used for the wire 3. The manufacturing conditions were adjusted to an arc current range of 120 to 160 A and an Ar gas flow rate of 15 L / min. A shielding gas spraying unit 25 is connected to the manufacturing head 1, and during manufacturing, a shielding gas for suppressing oxidation of the object is supplied from the shielding gas spraying unit 25. Ar gas was used as the shielding gas.

[0062] During the manufacturing process, as in the first and second embodiments, the MIG weld beads 42 were not continuously overlapped but were formed into an arc shape with gaps. The arc shape was then formed to fill the gaps. This method prevents the parabolic surface from being locally overheated and causing peeling during the manufacturing process. The MIG weld beads 42 were then gradually connected until the entire parabolic surface of the mold 10 was filled with the MIG weld beads 42 and the TIG weld beads 40, thereby forming the base 29 of the parabolic antenna mirror plate. Because the TIG weld beads 40 are thin, the MIG weld beads 42 were gradually connected so as to cover the TIG weld beads 40.

[0063] 17 is a cross-sectional view of a base 29 of a parabolic antenna mirror plate formed in the third embodiment. TIG weld beads 40 are formed at intervals in the recesses of the mold 10, and MIG weld beads 42 are formed all over the surface to cover the TIG weld beads 40. The TIG weld beads 40 and the MIG weld beads 42 are joined to each other to form the base 29 of the parabolic antenna mirror plate. The TIG weld beads 40 and the MIG weld beads 42 are dug into the mold 10 by different amounts, with the TIG weld bead 40 being dug into the mold by a larger amount than the MIG weld bead 42. As mentioned above, TIG welding is prone to high heat input because the filler metal is supplied manually, whereas MIG welding is performed by automatically supplying the filler metal, and therefore, heat input is controlled to avoid excessive heat input. For this reason, in the original form 29 of the parabolic antenna mirror plate according to this embodiment, the TIG weld bead 40 portion is raised higher than the MIG weld bead 42 portion on the surface on the mold material 10 side, i.e., the mirror surface side. The height of this raised portion is approximately 2 mm to several mm. This is because, as described above, the amount of engraving of the TIG weld bead 40 into the mold material 10 is approximately 3 mm to several mm, while the amount of engraving of the MIG weld bead 42 is approximately 1 mm. In addition, intermetallic compounds 16 are formed at the interfaces between the mold material 10 and the TIG weld bead 40 and MIG weld bead 42.

[0064] In order to form this intermetallic compound 16, the filler material, i.e., the material of the wire 3 and the welding rod 38, is a material different from the mold material 10, which when dissolved or mixed with the mold material 10, forms the intermetallic compound 16 at the interface with the mold material 10. In this embodiment, since the mold material 10 is Fe and the filler material is Al, FeAl ３ and Fe ２ Al ５ The intermetallic compound 16 is formed. The intermetallic compound 16 can be formed by adjusting welding conditions such as the welding temperature and the amount of filler metal supplied.

[0065] The intermetallic compound 16 is determined by the combination of the mold material 10 and the filler material. For example, when the mold material 10 is Fe and the filler material is Al, the intermetallic compound 16 is formed by the combination of Fe and Al. ３ Al, FeAl, FeAl ２, Fe ２ Al ５ , FeAl ３ , Fe ２ Al ６ , Fe ２ Al ９ Various Fe-Al based intermetallic compounds 16 such as the above are formed at the weld interface. These intermetallic compounds 16 have a higher Vickers hardness and are more brittle than the original metals Fe and Al. Among these, FeAl ３ and Fe ２ Al ５ However, the intermetallic compounds 16 have a higher Vickers hardness and are more brittle than the original metal. The type and composition ratio of the intermetallic compounds 16 formed can be adjusted by adjusting welding conditions such as the welding temperature and the amount of filler metal supplied.

[0066] By changing the combination of materials for the mold material 10 and the filler metal, it is possible to form intermetallic compounds 16 other than Fe-Al-based compounds. For example, when Ti or Ni is used for the mold material 9 and Al is used for the filler metal, Ti-Al-based or Ni-Al-based intermetallic compounds 16 can be formed. When Ni is used for the mold material 9 and Ti is used for the filler metal, Ni-Ti-based intermetallic compounds 16 can be formed. Intermetallic compounds generally have a higher Vickers hardness and are more brittle than the original metals, making them prone to cracking. In other words, the intermetallic compound 16 has a higher Vickers hardness and is more brittle than the original parabolic antenna mirror plate 29 made of the mold material 9 and the filler metal, making them prone to cracking.

[0067] The thickness of the intermetallic compound 16 affects the bonding strength at the interface. The thicker the intermetallic compound 16, the lower the bonding strength at the interface, and the more likely cracks are to occur in the intermetallic compound 16. On the other hand, the thinner the intermetallic compound 16, the higher the bonding strength at the interface. Therefore, in order to release the original form 29 of the parabolic antenna mirror plate from the mold material 10 in a later process, it is preferable that the intermetallic compound 16 is thick. Specifically, it is preferable that the thickness of the intermetallic compound 16 is 1 μm or more. The thickness of the intermetallic compound 16 can be adjusted by changing welding conditions such as the welding time and the amount of filler metal supplied.

[0068] <Step C2: Step of additively manufacturing a framework on the prototype of the parabolic antenna mirror plate> Next, a step of additively manufacturing a framework on the prototype of the parabolic antenna mirror plate is carried out. In this step, a framework 30 that supports the prototype 29 of the parabolic antenna mirror plate is formed integrally with the prototype 29 of the parabolic antenna mirror plate formed in step C1 by additive manufacturing using the DED method, to form the prototype 31 of the parabolic antenna.

[0069] 11, a framework 30 that supports the parabolic surface from behind was build-up welded to the prototype 29 of the parabolic antenna reflector plate without changing the welding conditions, completing the prototype 31 of the parabolic antenna. The framework 30 can be shaped to have a shape that is topology-optimized for the parabolic antenna reflector plate.

[0070] In this way, by continuously and integrally forming the base 29 of the parabolic antenna mirror plate and the framework 30, it is possible to form the base 31 of the parabolic antenna, unlike in the first embodiment.

[0071] <Step C3: Step of Releasing the Parabolic Antenna from its Original Form> Next, a step of releasing the parabolic antenna from its original form is carried out. The parabolic antenna original form 31 formed in step C2 is released from the mold material 10.

[0072] 12, a hook 33 is hung on the framework 30 of the prototype 31 of the parabolic antenna, and a slight upward force is applied by a wire rope 32 connected to the hook 33, while a wooden mallet is used to apply a mechanical impact to the interface between the mold 11 and the prototype 31 of the parabolic antenna. By doing this, the mold 10 and the prototype 31 of the parabolic antenna are peeled off from the intermetallic compound 16 at the interface, and the prototype 31 of the parabolic antenna is completely released from the mold 10.

[0073] Although a mechanical shock is applied in this embodiment, the means of applying the shock in this disclosure is not limited, and for example, a thermal shock may be applied. Furthermore, instead of a shock, vibration may be applied, such as ultrasonic vibration. The application of the shock or vibration does not necessarily have to be directly applied to the interface between the mold 10 and the parabolic antenna prototype 31; it may be indirectly applied to a location other than the interface as long as the shock or vibration is applied to the interface.

[0074] In addition to applying impact or vibration, for example, the mold material 10 may be fixed with an anchor and the parabolic antenna prototype 31 may be pulled little by little to cause the mold to separate. Alternatively, the mold material 10 and the parabolic antenna prototype 31 may be heated and the mold may be separated by the difference in the amount of thermal expansion resulting from the difference in the thermal expansion coefficients of the two. Specifically, a method of placing the mold material 10 in a furnace or a method of placing a heat source to cause localized separation from the mold material 10 while gradually moving the position of the heat source to promote the separation may be considered.

[0075] <Step C4: Step of Mirror-Finishing the Parabolic Antenna Mirror Plate Original> Finally, the parabolic antenna original is mirror-finished. The parabolic antenna original 31 released in step C3 is mirror-finished.

[0076] The surface of the mirror side of the parabolic antenna prototype 31 is subjected to a mirror finish. The mirror finish may be achieved by cutting using a lathe or milling machine, polishing using an abrasive, or any other method as long as the required surface roughness of the mirror surface can be achieved. In this manner, the parabolic antenna according to this embodiment is manufactured.

[0077] 17 , TIG weld beads 40 are formed at intervals in the recesses of the mold member 10, and MIG weld beads 42 are formed all over the surface to cover the TIG weld beads 40. MIG welding has lower energy than TIG welding, so the MIG weld beads 42 are weakly bonded to the mold member 10, while the TIG weld beads 40 are relatively strongly bonded to the mold member 10. By forming the TIG weld beads 40 that are relatively strongly bonded to the mold member 10 at intervals and forming the MIG weld beads 42 over the entire remaining portion, it is possible to locally vary the bond strength between the mold member 10 and the parabolic antenna prototype 31 formed by these weld beads. In this way, it is possible to control the releasability of the parabolic antenna prototype 31 from the mold member 10.

[0078] <Effect 2C> In this embodiment, unlike in embodiment 1, the parabolic antenna base 29 and framework 30 are continuously and integrally molded to form the parabolic antenna base 31. Therefore, in this embodiment, unlike embodiment 1, it is possible to manufacture a parabolic antenna rather than a parabolic antenna base plate. On the other hand, in order to complete the parabolic antenna in embodiment 1, after manufacturing the parabolic antenna base plate in this embodiment, it is necessary to separately connect or integrally mold a framework that supports the parabolic surface from behind.

[0079] <Effect 3C> As described with reference to FIG. 17 , before the original 29 of the parabolic antenna mirror plate according to this embodiment is released from the mold 10, the TIG weld bead 40 is recessed into the mold 10 by a few millimeters, and the MIG weld bead 42 is recessed into the mold 10 by a few millimeters. Therefore, the original 29 of the parabolic antenna mirror plate has a localized surface roughness on the order of a few millimeters on the mirror-side surface, which is the difference in elevation between the TIG weld bead 40 and the MIG weld bead 42. On the other hand, the original 59 of the parabolic antenna mirror plate according to the comparative example described with reference to FIG. 10 has an overall surface roughness on the order of a few millimeters on the mirror-side surface 58 a. Therefore, the original 29 of the parabolic antenna mirror plate according to this embodiment has fewer portions on the mirror-side surface with surface roughness on the order of a few millimeters than the original 59 of the parabolic antenna mirror plate according to the comparative example. That is, the parabolic antenna mirror plate prototype 29 according to this embodiment requires less grinding when grinding the mirror surface to the required surface roughness than the parabolic antenna mirror plate prototype 59 according to the comparative example. The same is true for the parabolic antenna prototype 31. This is because the parabolic antenna prototype 31 is formed by integrally molding the framework 30 from the side opposite the mirror surface, i.e., the parabolic surface side, of the parabolic antenna mirror plate prototype 29. Therefore, the parabolic antenna prototype 31 formed in this embodiment requires less grinding when grinding the mirror surface to the required surface roughness. Therefore, the parabolic antenna manufacturing method according to this embodiment can reduce the amount of grinding in the mirror finishing process.

[0080] Fourth Embodiment. A method for manufacturing a parabolic antenna according to the fourth embodiment will be described. In this embodiment, a parabolic antenna with a diameter of 2 m was manufactured, which is even larger than the parabolic antennas manufactured in the second and third embodiments. In this embodiment, first, a mold 11 to be used in this embodiment is manufactured. Then, the manufactured mold 11 is used to manufacture a parabolic antenna. The manufacturing method according to this embodiment includes steps D0 to D4. The following description will be given in order of steps D1 to D4.

[0081] <Step D0: Step of Manufacturing a Mold Material> First, the step of manufacturing a mold material is carried out. Hereinafter, the details of this step will be described with reference to FIGS.

[0082] FIG. 18 is a perspective view of a mold base 49, which is a part of the original mold 11 of the parabolic antenna mirror plate according to the fourth embodiment. The mold base 49 is the base of the original mold 11 of the parabolic antenna mirror plate. To manufacture the mold 11, the mold base 49 is first manufactured. The mold base 49 is manufactured by fitting reinforcing members 43 and 44 that intersect with each other. The mold base 49 has a curved surface with a recess in the depth direction. Furthermore, in the depth direction of the mold base 49, the portion where the reinforcing members 43 and 44 are not fitted is hollow. Therefore, the recess in the mold base 49 is shaped like a grid. The reinforcing members 43 and 44 were prepared by cutting out hot-rolled steel SS400 (JIS standard) to a thickness of 10 mm and providing notches for fitting together. Additionally, rings 45 are attached to the upper end surfaces of the reinforcing members 43 and 44, and define the outermost periphery of the recess in the mold base 49. A zinc-based rust inhibitor is applied to the recess in the mold base 49 with a brush and allowed to dry thoroughly.

[0083] In this embodiment, a large parabolic antenna with a diameter of 2 m is manufactured, and therefore the mold material is also large. Therefore, from the viewpoint of cost and size restrictions, the mold material base 49 is assembled by fitting reinforcing members 43 and 44 together. Note that the shape of the recess in mold material base 49 formed by fitting the reinforcing members is not limited to the aforementioned grid shape.

[0084] Fig. 19 is a cross-sectional view of the base 49 of the mold member shown in Fig. 18 in embodiment 4. As explained in Fig. 18, the reinforcing member 43 and the reinforcing member 44 are fitted together to form an integrated unit. In addition, a ring 45 is attached to the upper surface of the reinforcing member 44.

[0085] Figure 20 is a perspective view of a prototype mold 11 for a parabolic antenna mirror plate according to the fourth embodiment. The mold 11 is a mold for a prototype 29 of a parabolic antenna mirror plate. The mold 11 was manufactured by temporarily fixing #300 stainless steel mesh 46 in the grid-shaped recess of the mold base 49 described in Figures 18 and 19, and welding the contacting portions. The prototype 29 of the parabolic antenna mirror plate is additively manufactured on the stainless steel mesh 46. When the stainless steel mesh 46 is laid in the grid-shaped recess, care must be taken to prevent the stainless steel mesh 46 from loosening in the hollow portions that form the gaps between the grids.

[0086] The stainless steel mesh 46 is a mesh-like sheet member with stainless steel threads woven in. However, other sheet members may be used instead of the stainless steel mesh 46, as long as they can be laid in the recesses of the base 49 of the mold material and can form intermetallic compounds 16 between the reinforcing members 43 and 44 and the filler metal when melted by the heat during welding.

[0087] The welding of the stainless steel mesh 46 to the reinforcing members 43 and 44 was performed using an additive manufacturing device 200. A 1.2 mm diameter A5183 (JIS standard) welding aluminum wire was used for the wire 3, and the manufacturing conditions were a laser output of 2 kW and an Ar gas flow rate of 10 L / min. A grid-shaped weld bead 47 was formed in the laser-welded area. In the area where the grid-shaped weld bead 47 was formed, the stainless steel mesh 46 was melted by the heat generated during welding. Therefore, the grid-shaped weld bead 47 was welded to the reinforcing members 43 and 44, which supported the stainless steel mesh 46 as a base. An intermetallic compound 16 was formed at the interface between the grid-shaped weld bead 47 and the reinforcing members 43 and 44.

[0088] 21 is a cross-sectional view of the original mold 11 of the parabolic antenna mirror plate according to the fourth embodiment. The mold 11 comprises a mold base 49 made up of reinforcing members 43, 44, and a ring 45, and a stainless steel mesh 46. The stainless steel mesh 46 is spread over the mold base 49, and the mold base 49 and the stainless steel mesh 46 are welded together at their contact points by a grid-shaped weld bead 47. In the areas where the grid-shaped weld bead 47 is formed, the stainless steel mesh 46 is melted by the heat generated during welding, and an intermetallic compound 16 is formed.

[0089] In order to form this intermetallic compound 16, the filler material is a material different from the mold material 11, which when dissolved or mixed with the mold material 11, forms the intermetallic compound 16 at the interface with the mold material 11. In this embodiment, the intermetallic compound 16 is formed between the reinforcing members 43 and 44 that constitute the mold base 49, which is a part of the mold material 11. In this embodiment, since the mold material 11 is Fe and the filler material is Al, FeAl ３ and Fe ２ Al ５ The intermetallic compound 16 is formed. The intermetallic compound 16 can be formed by adjusting welding conditions such as the welding temperature and the amount of filler metal supplied.

[0090] The intermetallic compound 16 is determined by the combination of the mold material 11 and the filler material. For example, when the mold material 11 is Fe and the filler material is Al, the intermetallic compound 16 is formed by the combination of Fe and Al. ３ Al, FeAl, FeAl ２ , Fe ２ Al ５ , FeAl ３ , Fe ２ Al ６ , Fe ２ Al ９ Various Fe-Al based intermetallic compounds 16 such as these are formed at the weld interface. Many of these intermetallic compounds 16 have higher Vickers hardness and greater brittleness than the original metals Fe and Al. Among these, FeAl ３ and Fe ２ Al ５However, the intermetallic compounds 16 have a higher Vickers hardness and are more brittle than the original metal. The type and composition ratio of the intermetallic compounds 16 formed can be adjusted by adjusting welding conditions such as the welding temperature and the amount of filler metal supplied.

[0091] By changing the combination of the mold material 11 and the filler material, it is possible to form intermetallic compounds 16 other than Fe-Al-based compounds. For example, when Ti or Ni is used for the mold material 11 and Al is used for the filler material, Ti-Al-based or Ni-Al-based intermetallic compounds 16 can be formed. When Ni is used for the mold material 11 and Ti is used for the filler material, Ni-Ti-based intermetallic compounds 16 can be formed. Intermetallic compounds generally have a higher Vickers hardness and are more brittle than the original metals, making them prone to cracking. In other words, the intermetallic compound 16 has a higher Vickers hardness and is more brittle than the original 29 of the parabolic antenna mirror plate made of the mold material 11 and the filler material, making it prone to cracking.

[0092] The thickness of the intermetallic compound 16 affects the bonding strength at the interface. The thicker the intermetallic compound 16, the lower the bonding strength at the interface, and the more likely cracks are to occur in the intermetallic compound 16. On the other hand, the thinner the intermetallic compound 16, the higher the bonding strength at the interface. Therefore, in order to release the original form 29 of the parabolic antenna mirror plate from the mold material 11 in a later process, it is preferable that the intermetallic compound 16 be thick. Specifically, it is preferable that the thickness be 1 μm or more. The thickness of the intermetallic compound 16 can be adjusted by welding conditions such as the welding time and the amount of filler metal supplied.

[0093] <Step D1: Step of forming a prototype of a parabolic antenna mirror plate> Next, a step of forming a prototype 29 of a parabolic antenna mirror plate is carried out. The prototype 29 of a parabolic antenna mirror plate is formed on the mold material 11 manufactured in step D0.

[0094] First, build-up welding was performed on the stainless steel mesh 46 along the grid-shaped weld beads 47, leaving gaps between them. The build-up weld beads were then gradually joined together to form the base 29 of the parabolic antenna mirror plate on the mold 11. The build-up welding was performed using the additive manufacturing apparatus 200 used in step D0, with the laser output reduced to 1.5 kW. The laser output was reduced to prevent the stainless steel mesh 46 from melting or breaking due to the heat generated during welding in the areas where the mold base 49 does not support the stainless steel mesh 46, i.e., the grid-shaped hollow portions of the mold base 49.

[0095] 22 is a cross-sectional view of a prototype 29 of a parabolic antenna mirror plate according to the fourth embodiment. The prototype 29 of the parabolic antenna mirror plate is formed on a mold 11. The configuration of the mold 11 is as described in FIG. 21 . The prototype 29 of the parabolic antenna mirror plate is made up of a grid-shaped weld bead 47 and an overlay weld portion 48. As described above, the prototype 29 of the parabolic antenna mirror plate is formed by overlay welding along the grid-shaped weld bead 47, and therefore the grid-shaped weld bead 47 also becomes part of the prototype 29 of the parabolic antenna mirror plate.

[0096] As shown in FIG. 22 , at the interface between the grid-shaped weld bead 47 and the base 49 (reinforcement material 43) of the mold, no stainless steel mesh 46 is present, but an intermetallic compound 16 is formed. As described above, this is because the stainless steel mesh 46 is melted to weld the grid-shaped weld bead 47 to the base 49 of the mold. On the other hand, at the interface between the build-up weld portion 48 and the base 49 of the mold, no intermetallic compound 16 is formed, but the stainless steel mesh 46 is present. As described above, this is because the build-up welding is performed with a laser output that is not sufficient to melt or fracture the stainless steel mesh 46. Furthermore, because the build-up welding is performed on the grid-shaped weld bead 47 rather than the stainless steel mesh 46, the build-up weld portion 48 and the stainless steel mesh 46 are not welded. In other words, among the parts that constitute the base 29 of the parabolic antenna mirror plate, the build-up weld portion 48 is not joined to the mold 11, and the grid-shaped weld bead 47 is joined to the mold 11 via the intermetallic compound 16.

[0097] <Process D2: Process of additively manufacturing a framework on the prototype of the parabolic antenna mirror plate> Then, a process of additively manufacturing a framework on the prototype of the parabolic antenna mirror plate is carried out. In this process, a framework 30 that supports the prototype 29 of the parabolic antenna mirror plate is formed integrally with the prototype 29 of the parabolic antenna mirror plate formed in process D1 by additive manufacturing using the DED method, to form the prototype 31 of the parabolic antenna.

[0098] 11, a framework 30 that supports the parabolic surface from behind was build-up welded to the prototype 29 of the parabolic antenna reflector plate without changing the welding conditions, completing the prototype 31 of the parabolic antenna. The framework 30 can be shaped to have a shape that is topology-optimized for the parabolic antenna reflector plate.

[0099] In this way, by continuously and integrally forming the base 29 of the parabolic antenna mirror plate and the framework 30, it is possible to form the base 31 of the parabolic antenna, unlike in the first embodiment.

[0100] <Step D3: Step of Releasing the Parabolic Antenna from its Original Form> Next, a step of releasing the parabolic antenna from its original form is carried out. The parabolic antenna original form 31 formed in step D2 is released from the mold material 11.

[0101] 12, a hook 33 is hung on the framework 30 of the prototype 31 of the parabolic antenna, and a slight upward force is applied by a wire rope 32 connected to the hook 33, while a wooden mallet is used to apply a mechanical impact to the interface between the mold material 11 and the prototype 31 of the parabolic antenna. By doing this, the mold material 11 and the prototype 31 of the parabolic antenna are peeled off from the intermetallic compound 16 at the interface, and the prototype 31 of the parabolic antenna is completely released from the mold material 11.

[0102] Although a mechanical shock is applied in this embodiment, the shock may be applied by any means in the present disclosure, for example, a thermal shock. Furthermore, vibration may be applied instead of a shock, for example, ultrasonic vibration. The shock or vibration does not necessarily have to be applied directly to the interface between the mold 11 and the parabolic antenna prototype 31, and may be applied indirectly to a location other than the interface as long as the shock or vibration is applied to the interface.

[0103] In addition to applying impact or vibration, for example, the mold material 11 may be fixed with an anchor and the parabolic antenna prototype 31 may be pulled little by little to cause the mold to separate. Alternatively, the mold material 11 and the parabolic antenna prototype 31 may be heated and the mold may be separated by the difference in the amount of thermal expansion resulting from the difference in the thermal expansion coefficients of the two. Specifically, a method of placing the mold material 11 in a furnace or a method of placing a heat source to cause localized separation from the mold material 11 while gradually moving the position of the heat source to promote the separation may be considered.

[0104] Alternatively, as in the embodiment described in Fig. 7, the original 31 of the parabolic antenna mirror plate may be released from the mold 11 by removing its constituent members from the mold 11. Specifically, referring to Fig. 21, the reinforcing member 44 is removed by pulling it out from below relative to the reinforcing member 43. In this manner, a mechanical shock can be applied to the vicinity of the location where the original 29 of the parabolic antenna mirror plate is to be peeled off from the mold 11, allowing for more efficient release.

[0105] <Step D4: Step of Mirror-Finishing the Parabolic Antenna Mirror Plate Prototype> Finally, the parabolic antenna prototype 31 released in step D3 is subjected to a mirror-finishing process.

[0106] The surface of the mirror side of the parabolic antenna prototype 31 is subjected to a mirror finish. The mirror finish may be achieved by cutting using a lathe or milling machine, polishing using an abrasive, or any other method as long as the required surface roughness of the mirror surface can be achieved. In this manner, the parabolic antenna according to this embodiment is manufactured.

[0107] <Effect 1D> Unlike Embodiments 1 to 3, this embodiment uses a mold 11 having a mold base 49 fitted with reinforcing members 43 and 44 and a stainless steel mesh 46 laid across the mold base 49. Because the parabolic antenna mirror plate prototype 29 is formed on the stainless steel mesh 46, the mold base 49 supporting the stainless steel mesh 46 may have a cavity. The mold base 49 of this embodiment has a cavity in the lattice-shaped portion. This embodiment can reduce the cost of the mold by the amount of this cavity. Furthermore, even when manufacturing a large parabolic antenna, the mold can be easily manufactured by fitting the reinforcing members. These effects are particularly advantageous when manufacturing a large parabolic antenna with a diameter of 2 m or more, as in this embodiment.

[0108] 22 , among the parts constituting the original form 29 of the parabolic antenna mirror plate, the build-up weld portion 48 is not joined to the mold material 11, and only the cross-shaped weld beads 47 are joined to the mold material 11 via the intermetallic compound 16. Therefore, the area where the original form 29 of the parabolic antenna mirror plate is joined to the mold material 11 is reduced, and therefore the original form 29 of the parabolic antenna mirror plate can be easily separated from the mold material 11.

[0109] <Effect 3D> In this embodiment, unlike the first embodiment, the base form 29 of the parabolic antenna mirror plate and the framework 30 are continuously and integrally formed to form the base form 31 of the parabolic antenna. Therefore, in this embodiment, unlike the first embodiment, it is possible to manufacture a parabolic antenna rather than a parabolic antenna mirror plate. On the other hand, in order to complete the parabolic antenna in the first embodiment, after manufacturing the parabolic antenna mirror plate in the same embodiment, it is necessary to separately connect or integrally form a framework that supports the parabolic surface from behind.

[0110] <Effect 4D> As described in the first embodiment, the specular surface 18a of the original parabolic antenna mirror plate 29 has a smaller surface roughness than the specular surface 58a of the original parabolic antenna mirror plate 59 according to the comparative example. This is because, as described in FIG. 8 , the specular surface 18a of the original parabolic antenna mirror plate 29 is a surface released from the mold 11, which has a small surface roughness. Furthermore, the specular surface 18a of the original parabolic antenna mirror plate 29 is also the specular surface of the original parabolic antenna 31. This is because the original parabolic antenna 31 is formed by integrally molding the framework 30 that supports the parabolic surface from behind with the original parabolic antenna mirror plate 29. Therefore, the original parabolic antenna 31 formed in this embodiment requires less grinding when grinding the specular surface to the required surface roughness. Therefore, in the method for manufacturing a parabolic antenna according to this embodiment, the amount of grinding can be reduced in the mirror finishing step.

[0111] 1 Modeling head, 2 Bobbin, 3 Wire, 9, 10, 11 Mold material, 16 Intermetallic compound, 19 Processing plate, 20 Hook hook portion, 21 Fixing jig, 29 Original form of mirror plate for parabolic antenna, 30 Frame, 31 Original form of parabolic antenna, 39 Weld bead, 40 TIG weld bead, 42 MIG weld bead, 43, 44 Reinforcement material 45 Ring, 46 Stainless steel mesh, 47 lattice-shaped weld bead, 48 Overlay weld portion, 49 Base of mold material, 200, 201 Additive manufacturing device, 300 TIG welding machine

Claims

1. A method for manufacturing a parabolic antenna mirror plate, comprising the steps of: forming a prototype of the parabolic antenna mirror plate by additive manufacturing using a Directed Energy Deposition (DED) method, in which a filler material is used for a mold material that will serve as the mold for the parabolic antenna mirror plate, and the filler material is a material that will form an intermetallic compound at the interface with the mold material when dissolved or mixed with the mold material; peeling the prototype of the parabolic antenna mirror plate from the mold material and releasing it from the mold material; and finishing the prototype of the parabolic antenna mirror plate to a mirror finish.

2. A method for manufacturing a parabolic antenna mirror plate as described in claim 1, characterized in that the intermetallic compound has a higher Vickers hardness and is more brittle than the mold material and the original form of the parabolic antenna mirror plate.

3. A method for manufacturing a parabolic antenna mirror plate as described in claim 1 or 2, characterized in that the process of releasing the original form of the parabolic antenna mirror plate from the mold is carried out by applying impact or vibration to the interface between the mold and the original form of the parabolic antenna mirror plate.

4. A method for manufacturing a parabolic antenna mirror plate according to claim 3, wherein the method for applying the shock or vibration is either mechanical shock, thermal shock, or ultrasonic vibration.

5. A method for manufacturing a parabolic antenna mirror plate as described in claim 1 or 2, characterized in that the process of releasing the original shape of the parabolic antenna mirror plate from the mold is carried out by fixing the mold with an anchor and pulling the original shape of the parabolic antenna mirror plate from the mold.

6. A method for manufacturing a parabolic antenna mirror plate as described in claim 1 or 2, characterized in that the process of releasing the original shape of the parabolic antenna mirror plate from the mold material is performed by utilizing the difference in thermal expansion coefficients between the mold material and the parabolic antenna mirror plate.

7. A method for manufacturing a parabolic antenna mirror plate according to any one of claims 1 to 6, characterized in that the intermetallic compound is an Fe-Al based, Ti-Al based, Ni-Al based, or Ni-Ti based intermetallic compound.

8. The intermetallic compound is FeAl ３ or Fe ２ Al ５ 8. The method for manufacturing a parabolic antenna mirror plate according to claim 7, wherein 9. A method for manufacturing a parabolic antenna mirror plate according to any one of claims 1 to 8, characterized in that the thickness of the intermetallic compound is 1 μm or more.

10. A method for manufacturing a parabolic antenna, comprising: a step of forming a prototype of a parabolic antenna mirror plate by additive manufacturing using a DED method, in which a filler material is used for a mold material that will serve as a mold for the parabolic antenna mirror plate, and the filler material is a material that is different from the mold material and that forms an intermetallic compound at the interface with the mold material when dissolved or mixed with the mold material; a step of forming a framework that supports the prototype of the parabolic antenna mirror plate by additive manufacturing using the DED method, integrally with the prototype of the parabolic antenna mirror plate, to form the prototype of the parabolic antenna; a step of peeling the prototype of the parabolic antenna from the mold material, and releasing the prototype of the parabolic antenna from the mold material; and a step of mirror-finishing the prototype of the parabolic antenna.

11. A method for manufacturing a parabolic antenna as set forth in claim 10, wherein the intermetallic compound has a higher Vickers hardness and is more brittle than the mold material and the original shape of the parabolic antenna mirror plate.

12. A method for manufacturing a parabolic antenna as set forth in claim 10 or 11, characterized in that the step of releasing the original form of the parabolic antenna from the mold material is carried out by applying impact or vibration to the interface between the mold material and the original form of the parabolic antenna.

13. The method for manufacturing a parabolic antenna according to claim 12, wherein the method for applying the shock or vibration is either a mechanical shock, a thermal shock, or ultrasonic vibration.

14. A method for manufacturing a parabolic antenna as described in claim 10 or 11, characterized in that the step of releasing the original form of the parabolic antenna from the mold is carried out by fixing the mold with an anchor and pulling the original form of the parabolic antenna from the mold.

15. A method for manufacturing a parabolic antenna as described in claim 10 or 11, characterized in that the step of releasing the original parabolic antenna from the mold material involves heating the mold material and the original parabolic antenna, and releasing them by the difference in thermal expansion amounts resulting from the difference in the thermal expansion coefficients of the two.

16. A method for manufacturing a parabolic antenna according to any one of claims 10 to 15, wherein the intermetallic compound is an Fe-Al based, Ti-Al based, Ni-Al based, or Ni-Ti based intermetallic compound.

17. The intermetallic compound is FeAl ３ or Fe ２ Al ５ The method for manufacturing a parabolic antenna according to claim 16, 18. A method for manufacturing a parabolic antenna according to any one of claims 10 to 17, characterized in that the thickness of the intermetallic compound is 1 μm or more.

19. A method for manufacturing a parabolic antenna as set forth in any one of claims 10 to 18, characterized in that a step of forming TIG welding beads at intervals on the mold material is added before the step of forming the original shape of the mirror plate for the parabolic antenna, and the step of forming the original shape of the mirror plate for the parabolic antenna includes forming MIG welding beads along the TIG welding beads.

20. A method for manufacturing a parabolic antenna as set forth in any one of claims 10 to 19, characterized in that the mold has a mold base fitted with multiple reinforcing materials and a sheet member laid out on the mold base, the contact points between the mold base and the sheet member are welded with a weld bead, and the prototype of the parabolic antenna is additively manufactured on the sheet member.

21. A method for manufacturing a parabolic antenna as set forth in claim 20, wherein the portion of the base of the mold where the sheet material is laid out is in a grid pattern.

22. A method for manufacturing a parabolic antenna as described in claim 20 or 21, characterized in that the portion where the base of the mold and the sheet member come into contact with each other is welded with a weld bead formed by additive manufacturing using the DED method.

23. The method for manufacturing a parabolic antenna according to claim 22, characterized in that additive manufacturing using the DED method is performed along the weld bead with an output that does not melt the sheet member.

24. A method for manufacturing a parabolic antenna according to claim 22 or 23, characterized in that the weld bead is a part of the original shape of the parabolic antenna reflector plate.

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