WO2025187072A1 - Method for manufacturing parabolic antenna and method for manufacturing mirror surface plate for parabolic antenna - Google Patents

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

This disclosure relates to a method for manufacturing a parabolic antenna and a method for manufacturing a mirror plate for a parabolic antenna.

Traditionally, methods for manufacturing mirror plates for parabolic antennas have included forming a master mold for the mirror plate using injection molding or transfer molding, then depositing a metal film on the surface to form the mirror surface, or using aluminum die casting. However, these methods require large injection molding machines or press molding machines for large parabolic antennas with diameters exceeding 1m, which can be cost-prohibitive for production volumes approaching a few to a dozen units made to order.

As an alternative to using such large injection molding machines or press molding machines, a method has been disclosed in which metal spraying is applied to a parabolic mirror plate matrix to produce a thick-walled mirror plate for a parabolic antenna (see, for example, Patent Document 1). However, with this method, when a metal mold is used as the matrix, the metal spraying must be carried out at a low temperature to prevent reaction with the matrix, i.e., alloying. However, because the metal spray film thickness is thin, if the film thickness is on the order of millimeters, the temperature rises during processing, causing a reaction with the matrix, making it difficult to release the mirror plate produced by metal spraying from the matrix. Furthermore, when a wooden mold is used as the matrix, the mirror plate to be produced is large and thick, which poses the problem of the mirror plate peeling off from the matrix during the spraying process due to stress.

JP 51-83451

In order to avoid these problems, the inventors have been actively considering applying a manufacturing method called Directed Energy Deposition (DED), which is a manufacturing device for metal additive manufacturing using a technology called Additive Manufacturing (AM), is suitable for manufacturing large objects, has a fast manufacturing time, and can be used to manufacture mirror plates for parabolic antennas. The DED method uses wire or metal powder as the raw material and deposits the raw material in the required locations by welding.

However, with DED additive manufacturing, the surface roughness of the created object is on the order of millimeters, so when manufacturing objects that require a surface roughness at the μm level, such as mirror panels for parabolic antennas, the amount of grinding required in the post-process mirror finishing to achieve the required surface roughness is large, which poses a cost disadvantage.

The manufacturing method for 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 through additive manufacturing using the Directed Energy Deposition (DED) method, in which a filler material, different from the mold material that will form the parabolic antenna mirror plate's mold, is used as a filler material, which 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 to release the prototype of the parabolic antenna mirror plate from the mold material; and mirror-finishing the prototype of the parabolic antenna mirror plate.

Furthermore, the method for manufacturing a parabolic antenna 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 the DED method, in which a filler material is used for the mold material that will serve as the 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; 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; peeling the prototype of the parabolic antenna from the intermetallic compound and releasing the prototype of the parabolic antenna from the mold material; and polishing the prototype of the parabolic antenna to a mirror finish.

According to this disclosure, it is possible to manufacture parabolic antennas and mirror plates for parabolic antennas with reduced grinding amounts during the mirror finishing process.

1 is a perspective view of a mold 9 of the original shape of a parabolic antenna mirror plate according to a first embodiment; 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. FIG. 1 is an enlarged cross-sectional view showing how a prototype 29 of a parabolic antenna mirror plate is additionally manufactured on a mold 9 in the first embodiment. FIG. 10 is a perspective view showing a state in the middle of additionally manufacturing a prototype 29 of a parabolic antenna mirror plate on a mold 9 in the first embodiment. 1 is a cross-sectional view of a prototype 29 of a parabolic antenna mirror plate formed on a mold 9 in the first embodiment. FIG. 1 is a cross-sectional view showing a state in which the original 29 of the parabolic antenna mirror plate is released from the mold 9 in the first embodiment. FIG. 10 is a perspective view showing a modified example of how the base 29 of the parabolic antenna mirror plate is released from the mold 9 in the first embodiment. 1 is an enlarged cross-sectional view of a base 29 of a parabolic antenna mirror plate released from a mold 9 in the first embodiment. 5 is a cross-sectional view of a prototype 59 of a parabolic antenna reflector plate according to a comparative example. 1 is an enlarged cross-sectional view of a prototype 59 of a parabolic antenna reflector plate according to a comparative example. 10 is a cross-sectional view of a parabolic antenna prototype 31 formed on a mold 9 in the second embodiment. FIG. 10 is a cross-sectional view showing a state in which the prototype 31 of the parabolic antenna is released from the mold 9 in the second embodiment. 10 is a cross-sectional view of a base mold 10 of a parabolic antenna mirror plate according to a third embodiment. FIG. 10 is a cross-sectional view showing a state in which a TIG weld bead 40 is formed on a mold material 10 in the third embodiment. FIG. 10 is a perspective view showing a TIG weld bead 40 formed on a mold material 10 in the third embodiment. FIG. 10 is an enlarged perspective view showing a state in which a MIG weld bead 42 is formed along a TIG weld bead 40 on a mold 10 in the third embodiment. 10 is a cross-sectional view of a prototype 29 of a parabolic antenna mirror plate formed in the third embodiment. FIG. 10 is a perspective view of a base 49 of a mold, which is a part of the original mold 11 of the parabolic antenna mirror plate according to the fourth embodiment. FIG. 17 is a cross-sectional view of the base 49 of the mold shown in FIG. 16 in the fourth embodiment. 11 is a perspective view of a base mold 11 of a parabolic antenna mirror plate according to a fourth embodiment. 10 is a cross-sectional view of a mold 11 of the original shape of a parabolic antenna mirror plate according to a fourth embodiment. 10 is a cross-sectional view of a prototype 29 of a parabolic antenna reflector plate according to a fourth embodiment.

Details of embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts will be designated by the same reference symbols, and redundant explanations will not be repeated. Note that the embodiments described below are examples, and the scope of the present disclosure is not limited to the embodiments described below.

Embodiment 1.
A method for manufacturing a mirror plate for a parabolic antenna according to a first embodiment 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.

<Step A1: Step of forming the prototype of the parabolic antenna mirror plate>
First, a process for forming the prototype of the parabolic antenna reflector plate is carried out. The details of this process will be explained below with reference to FIGS. 1 to 5.

Figure 1 is a perspective view of a mold 9 for the original shape of a parabolic antenna mirror plate in embodiment 1. A concave surface is formed in the center of the mold 9, which will serve as the mold for the original shape 29 of the parabolic antenna mirror plate. The mold 9 has a bowl-shaped recess, and the original shape 29 of the parabolic antenna mirror plate is manufactured by performing additive manufacturing using the DED method on this portion. Here, the original shape 29 of the parabolic antenna mirror plate is a shaped object having the shape of a parabolic antenna mirror plate, which becomes a parabolic antenna mirror plate by applying a mirror finish to the surface on the mirror side. The mold 9 has a small surface roughness. Specifically, it is sufficient to use steel material that has been mirror-finished until the variation in surface irregularities is approximately 0.1 to 5 μm. 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.

As will be explained later, the mold 9 is created by connecting multiple work plates 19 with fixing jigs 21 and attaching hook hooks 20. For convenience, Figure 1 depicts the mold 9 without showing the work plates 19, fixing jigs 21, and hook hooks 20. Unless otherwise specified, this applies to other drawings as well.

Figure 2 is a cross-sectional view of the original mold 9 for the parabolic antenna mirror plate according to embodiment 1, taken along the cross-sectional line II-II in Figure 1. As mentioned above, the mold 9 was created by connecting multiple processed plates 19 with fixtures 21 and attaching hook 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, processed plates 19 made from 100 mm thick plate material were connected with fixtures 21. Furthermore, hook 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 allowed to dry thoroughly. Instead of using a zinc-based rust inhibitor, hot-dip galvanizing may be performed.

Figure 3 is an enlarged cross-sectional view showing the additive manufacturing of a prototype 29 of a parabolic antenna mirror plate on a mold 9 in embodiment 1. In this embodiment, a DED-type additive manufacturing device 200 was used to form the shape 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 type of device that performs DED-type additive manufacturing using a laser light source.

As shown in Figure 3, the additive manufacturing device 200 has a modeling head 1. A fiber laser oscillator 23, a near-infrared light source, is connected to the modeling head 1 via an optical fiber 27. The laser light emitted by the fiber laser oscillator 23 is guided via the optical fiber 27 to a duct within the modeling head 1, where it is focused from the center of the modeling 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 modeling position, a filler material, wire 3, is fed from the side of the modeling head 1 to form a weld bead 39, thereby performing additive manufacturing. The wire 3 is fed to the modeling position by feeding the wire 3 wound around a bobbin 2 using a wire feeding and straightening machine 26. A 1.2 mm diameter A5183 (JIS standard) aluminum welding wire was used for the wire 3. The modeling conditions were a laser output 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. A shielding gas spraying unit 25 is also connected to the modeling head 1, and 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 wire 3 to the model material 9 via a zinc-based rust inhibitor applied to the surface of the model material 9.

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 term "weld bead" as used herein 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 formed by additive manufacturing using the DED method. To form this intermetallic compound 16, a filler metal, i.e., a material for the wire 3, is used 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, the mold material 9 is _Fe and the filler metal is Al, so that an intermetallic compound 16 such as _FeAl3 or _Fe2Al5 is formed. Intermetallic compounds generally have a higher Vickers hardness and are more brittle than the original metals, making them prone to cracking. That is, the intermetallic compound 16 has a higher Vickers hardness and is more brittle than the mold material 9 and the weld bead 39, making them prone to cracking. In order to form such intermetallic compounds 16, it is only necessary to adjust welding conditions such as the welding temperature and the amount of filler metal supplied. 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.

Figure 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 embodiment 1. For convenience, the additive manufacturing device 200 is not shown. As shown in Figure 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 an arc-shaped shape with gaps between them.

Furthermore, the formation of the weld bead 39 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 the forming process. Then, by gradually connecting the weld beads 39 until the entire parabolic surface of the mold material 9 was filled with the weld beads 39, the prototype 29 of the parabolic antenna mirror plate was formed.

Figure 5 is a cross-sectional view of a prototype 29 of a parabolic antenna mirror plate formed on a mold 9 in embodiment 1. 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 that comes into 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.

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, intermetallic compounds ₁₆ such as FeAl3 and _Fe2Al5 are formed at the welding interface between the mold material ₉ and the original 29 of the parabolic antenna mirror plate. In order to form the intermetallic compound 16, it is sufficient to adjust welding conditions such as the welding temperature and the amount of filler material supplied.

The intermetallic compounds 16 are 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, various Fe-Al based intermetallic compounds 16 such as _Fe3Al , _FeAl , _FeAl2 , _Fe2Al5 , _FeAl3 , _Fe2Al6 , _{and Fe2Al9} 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, _FeAl3 and _Fe2Al5 in particular have higher Vickers hardness and greater brittleness than the original metals. The type and composition ratio of the intermetallic compounds 16 formed can be adjusted by welding conditions such as the welding temperature and the amount of filler material supplied.

By changing the combination of materials for the mold material 9 and filler metal, it is possible to form intermetallic compounds 16 other than those based on Fe-Al. For example, if Ti or Ni is used for the mold material 9 and Al is used for the filler metal, it is possible to form intermetallic compounds 16 such as Ti-Al or Ni-Al. If Ni is used for the mold material 9 and Ti is used for the filler metal, it is possible to form Ni-Ti intermetallic compounds 16. Intermetallic compounds generally have a higher Vickers hardness and are more brittle than the original metals, making them more susceptible 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 filler metal, making it more susceptible to cracking.

The thickness of the intermetallic compound 16 affects the bond strength at the interface. The thicker the intermetallic compound 16, the lower the bond strength at the interface, making it more susceptible to cracks. On the other hand, the thinner the intermetallic compound 16, the higher the bond strength at the interface. For this reason, 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 be thick. Specifically, it is preferable that it be 1 μm or thicker. The thickness of the intermetallic compound 16 can be adjusted by adjusting welding conditions such as the welding time and the amount of filler metal supplied.

<Step A2: Step of releasing the original shape 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.

Figure 6 is a cross-sectional view showing the state in which the original 29 of the parabolic antenna mirror plate has been released from the mold material 9 in embodiment 1. 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 Figure 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.

One method for releasing the parabolic antenna mirror plate original 29 from the mold 9 is to apply impact or vibration to the interface between the mold 9 and the parabolic antenna mirror plate. In this way, the parabolic antenna mirror plate original 29 peels off from the mold 9. In this embodiment, a mechanical impact is applied with a mallet. The impact may also be a thermal shock. Vibration may also be applied instead of impact, such as ultrasonic vibration. The impact or vibration does not necessarily have to be applied directly to the interface between the mold 9 and the parabolic antenna mirror plate original 29; it may be applied indirectly at a location other than the interface as long as the impact or vibration is applied to the interface.

In addition to applying impact or vibration, for example, the mold material 9 can be fixed with an anchor and the original form 29 of the parabolic antenna mirror plate can be pulled little by little to separate it from the mold. Alternatively, the mold material 9 and the original form 29 of the parabolic antenna mirror plate can be heated and separated from each other by the difference in the amount of thermal expansion that arises from the difference in the thermal expansion coefficients of the two. Specifically, this can be done by placing them in a furnace, or by placing a heat source and causing localized separation from the mold material 9 while gradually moving the position of the heat source to promote separation.

As another variation, as shown in Figure 7, the fixing jig 21 that holds the mold material 9 in place can be removed, and the processing plate 19, which is a component of the mold material 9, can be removed from the outside to release the original 29 of the parabolic antenna mirror plate. In this way, a mechanical shock can be applied to the vicinity of the point where the original 29 of the parabolic antenna mirror plate is to be peeled off from the mold material 9, allowing for more efficient release.

Figure 8 is an enlarged cross-sectional view of the original 29 of the parabolic antenna mirror plate released from the mold 9 in embodiment 1. For the original 29 of the parabolic antenna mirror plate shown in Figure 8, surface 18a is the surface released from the mold 9. In other words, 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 come into contact with the mold 9 during molding. In other words, 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.

As shown in Figure 8, the surface roughness of surface 18a is smaller than that of surface 18b. The reasons for this are as follows. First, because surface 18a is the surface released from mold 9, the surface roughness of surface 18a depends on the surface roughness of mold 9. Furthermore, as explained in Figure 1, a mold 9 with 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 9. However, intermetallic compounds 16 generally have a thickness on the order of μm. Even if they remain attached to surface 18a when the original 29 of the parabolic antenna mirror plate is released from mold 9, the effect of 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, the opposite side of surface 18a, is the surface that has not been released from mold 9, i.e., the surface that did not come into contact with mold 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 components such as mold materials has a high surface roughness. For this reason, the surface roughness of surface 18a is high. As a result, the surface roughness of surface 18a is smaller than the surface roughness of surface 18b.

<Step A3: Step of mirror-finishing the original shape 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.

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 may be used as long as it can achieve the required surface roughness of the mirror surface.
<Function Effect 1A>

As explained in Figure 8, the surface 18a on the mirror side has a smaller surface roughness than the opposite surface 18b. Therefore, the original 29 of the parabolic antenna mirror plate manufactured in this embodiment requires less grinding when grinding the mirror surface to the required order of surface roughness.

Next, a comparison with the surface of the original 59 of the parabolic antenna mirror plate according to the comparative example will be described. The original 59 of the 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 Figure 9. In other words, the original 59 of the parabolic antenna mirror plate is formed without contacting other parts except for the areas that come into contact with the base plate 57. After being formed, the original 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 it is additively manufactured on a flat base plate 57, rather than on the mold material 9 of the original shape of the parabolic antenna mirror plate.

Figure 10 is an enlarged cross-sectional view of prototype 59 of a parabolic antenna mirror plate according to a comparative example. As mentioned above, prototype 59 of the parabolic antenna mirror plate is formed on base plate 57 using additive manufacturing with the DED method, but is formed without contact with other components except for the area that comes into contact with base plate 57. Surface 58a is the surface that becomes the mirror side of the parabolic antenna mirror plate, the portion that does not come into contact with base plate 57 during fabrication. Surface 58b is the surface opposite the mirror side. The surface roughness of surface 58a is approximately the same as the surface roughness of surface 58b. In other words, unlike the present embodiment, the surface roughness of the mirror side is approximately the same as the surface roughness of the opposite side. When the fabrication conditions, such as laser output, were the same as those of the present embodiment, the variation in the unevenness of surfaces 58a and 58b was approximately 0.5 to 1.5 mm.

On the other hand, as explained in Figure 8, the mirror-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 laser output, are the same, the mirror-side surface 18a of the original 29 of the parabolic antenna mirror plate according to this embodiment shown in Figure 8 has a smaller surface roughness than the mirror-side surface 58a of the original 59 of the parabolic antenna mirror plate according to the comparative example shown in Figure 10. Comparing the surface roughness values mentioned above, the variation in unevenness of the mirror-side surface 58a of the original 59 of the parabolic antenna mirror plate is approximately 0.5 to 1.5 mm, whereas the variation in unevenness of the mirror-side surface 18a of the original 29 of the parabolic antenna mirror plate is approximately 50 to 100 μm.

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

Embodiment 2.
A method for manufacturing a parabolic antenna according to the second embodiment will now be described. The parabolic antenna according to this 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 the original parabolic antenna 31, and then releasing the molded original parabolic antenna 31 and polishing it to a mirror finish. The manufacturing method according to this embodiment includes steps B1 to B4. Steps B1 to B4 will be described below.

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

<Step B2: Step of adding a framework to the original shape of the parabolic antenna mirror plate>
Next, a process of additively manufacturing a framework for 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 B1 by additive manufacturing using the DED method, to form the prototype 31 of the parabolic antenna. The details of this process will be described below with reference to FIG. 11.

Figure 11 is a cross-sectional view of a parabolic antenna prototype 31 formed on a mold 9 in embodiment 2. The parabolic antenna prototype 31 is manufactured by integrally molding a framework 30 that supports the parabolic surface from behind onto the parabolic antenna mirror plate prototype 29 before releasing the parabolic antenna mirror plate prototype 29 formed in process B1 from the mold 9. Here, the parabolic antenna prototype 31 is a shaped object having the form of a parabolic antenna, which becomes a parabolic antenna by applying a mirror finish to the surface on the mirror side. The parabolic antenna prototype 31 is manufactured by forming and welding the framework 30 onto the formed parabolic antenna mirror plate prototype 29 using additive manufacturing with the DED method. The formation of the framework 30 was carried out continuously from the formation of the parabolic antenna mirror plate prototype 29 without changing the welding conditions. The framework 30 can be shaped to have a topology optimized design shape for the parabolic antenna mirror plate.

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 embodiment 1.

<Step B3: Step of releasing the original shape of the parabolic antenna>
Next, a step of releasing the original form of the parabolic antenna mirror plate is carried out. The original form 31 of the parabolic antenna 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.

Figure 12 is a cross-sectional view showing how the parabolic antenna prototype 31 is released from the mold 9 in embodiment 2. 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 wooden mallet is used to apply a mechanical impact to the interface between the mold 9 and the parabolic antenna prototype 31. In this way, the mold 9 and the parabolic antenna prototype 31 begin to peel from the intermetallic compound 16 at the interface, and the parabolic antenna prototype 31 is completely released from the mold 9.

In this embodiment, a mechanical shock is applied, but the means of applying the shock in this disclosure are not limited, and for example, a thermal shock may be applied. Furthermore, vibration may be applied instead of a shock, such as ultrasonic vibration. The application of shock or vibration does not necessarily have to be directly at the interface between the mold material 9 and the parabolic antenna prototype 31; it may be indirect, even at a location other than the interface, as long as the shock or vibration is applied to the interface.

In addition to applying impact or vibration, for example, the mold material 9 can be fixed with an anchor and the parabolic antenna prototype 31 can be pulled little by little to separate it from the mold. Alternatively, the mold material 9 and the parabolic antenna prototype 31 can be heated and separated by the difference in the amount of thermal expansion that arises from the difference in the thermal expansion coefficients of the two. Specifically, this can be done by placing them in a furnace, or by placing a heat source and causing localized separation from the mold material 9 while gradually moving the position of the heat source to promote separation.

<Step B4: Mirror-finishing the original shape of the parabolic antenna>
Finally, a step of mirror-finishing the parabolic antenna prototype 31 is carried out. The parabolic antenna prototype 31 released in step B3 is mirror-finished.

A mirror finish is applied to the mirror side surface of the parabolic antenna prototype 31. The mirror finish can 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 way, the parabolic antenna according to this embodiment is manufactured.

<Function Effect 1B>
In this embodiment, unlike the first embodiment, a parabolic antenna base 29 and a framework 30 are continuously and integrally molded to form a parabolic antenna base 31. Therefore, in this embodiment, unlike the first embodiment, a parabolic antenna can be manufactured instead of a parabolic antenna base. On the other hand, in order to complete the parabolic antenna in the first embodiment, after manufacturing the parabolic antenna base in the first embodiment, it is necessary to connect or integrally mold a framework that supports the parabolic surface from behind.

<Action 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. The specular surface 18a of the original parabolic antenna mirror plate 29 is also the specular surface of the original parabolic antenna 31. 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.

Embodiment 3.
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 base 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.

<Step C1: Step of forming the prototype of the parabolic antenna mirror plate>
First, a process for forming the prototype 29 of the parabolic antenna mirror plate is carried out. The details of this process will be described below with reference to FIGS.

Figure 13 is a cross-sectional view of the original mold 10 for the parabolic antenna mirror plate according to the third embodiment. Mold 10 is the mold for the original shape 29 of the parabolic antenna mirror plate. Mold 10 has a bowl-shaped recess. Unlike mold 9 according to the first and second embodiments, mold 10 was manufactured by casting, rather than by fixing multiple processed plates 19 with a fixture 21. Stainless steel casting SCS13 was used as the material for mold 10. The dimensions of the recess were adjusted to a diameter of 1.1 m and a depth of 0.35 m. The parabolic surface side of mold 10 was ground so that the surface roughness had a variation of approximately 0.1 to 5 μm. Like mold 9, mold 10 uses a mold with a small surface roughness.

Figure 14 is a cross-sectional view showing the formation of a TIG weld bead 40 on a mold 10 in embodiment 3. The surface of the mold 10 to be TIG welded is roughened in advance using a wire brush. Furthermore, because the material of the mold 10, stainless steel casting SCS13 (JIS standard), has a strong oxide film, flux is applied to the roughened surface. As shown in Figure 14, the TIG weld bead 40 was formed by melting a welding rod 38, which serves as a filler material, and overlay welding 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 is attached to one input terminal of the arc welding power source 35 via a conductor 34, and a ground electrode 36 is attached to the other input terminal via a conductor 34 and is grounded to the mold 10. The current was adjusted to approximately 100-120A, 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 prevent oxidation of the TIG weld bead 40. Ar gas was used as the shielding gas.

TIG welding requires manual addition of filler metal to a molten pool on the surface of the base metal, which has been melted by an arc. This requires sufficient heat input, making it easy for the molded member 10 to melt at the weld. Therefore, as shown in Figure 14, a TIG weld bead 40 is formed by engraving a certain amount into the molded member 10, as shown in Figure 14. 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 allows for lower heat input energy control than TIG welding, and the engraving depth can be reduced to approximately 100 μm. On the other hand, TIG welding has high energy, making it easy to weld with 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 wattage and feed rate than laser welding, making welding easier.

Figure 15 is a perspective view of a mold 10 with TIG weld beads 40 formed on it in embodiment 3. 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 melts sufficiently, forming intermetallic compounds 16 between the TIG weld beads 40. At this time, the intermetallic compounds 16 are formed over the entire weld interface, as described in Figure 5.

16 is an enlarged perspective view showing the formation of MIG weld beads 42 along TIG weld beads 40 on the mold 10 in embodiment 3. Using an additive manufacturing device 201, MIG weld beads 42 were formed on the mold 10 at intervals along the TIG weld beads 40 described in FIG. 15. The additive manufacturing device 201 is a type of device that performs DED-type additive manufacturing using MIG welding, a type of arc welding. Unlike TIG welding, MIG welding automatically supplies filler metal using the additive manufacturing device 201. For this reason, MIG welding can be controlled to keep heat input lower than TIG welding, and the amount of engraving into the mold 10 is small, at approximately 1 mm. Because the MIG weld beads 42 are weakly bonded to the mold 10, it is preferable to form them along the TIG weld beads 40, which are relatively strongly bonded to the mold 10.

As shown in Figure 16, the additive manufacturing device 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 building 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 device 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 embodiment 1, a 1.2 mm diameter A5183 (JIS standard) welding aluminum wire was used for the wire 3. The building conditions were adjusted to an arc current in the range of 120 to 160 A and an Ar gas flow rate of 15 L/min. In addition, a shielding gas spraying unit 25 is connected to the modeling head 1, and 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.

In the manufacturing process, as in embodiments 1 and 2, the MIG weld beads 42 were not stacked continuously, 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 receiving excessive heat locally, which can cause peeling during manufacturing. The MIG weld beads 42 were then gradually connected until the entire parabolic surface of the mold 10 was filled with MIG weld beads 42 and TIG weld beads 40, thereby forming the original 29 of the parabolic antenna mirror plate. Because the TIG weld beads 40 are thin, the MIG weld beads 42 were gradually connected so that they covered the TIG weld beads 40.

Figure 17 is a cross-sectional view of the original 29 of a parabolic antenna mirror plate formed in embodiment 3. TIG weld beads 40 are formed at intervals in the recesses of the mold 10, and MIG weld beads 42 are formed all over to cover the TIG weld beads 40. The TIG weld beads 40 and MIG weld beads 42 are joined to each other to form the original 29 of the parabolic antenna mirror plate. The TIG weld beads 40 and MIG weld beads 42 have different depths of penetration into the mold 10, with the TIG weld bead 40 being more deeply penetrated than the MIG weld bead 42. As mentioned above, TIG welding is prone to high heat input because the filler metal is supplied manually, but MIG welding is performed by automatically supplying the filler metal, so heat input is controlled to prevent excessive heat. 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 facing the mold 10, i.e., the mirror surface side. The height of this raised portion is approximately 2 mm to several mm. This is because, as mentioned above, the TIG weld bead 40 is dug into the mold 10 by approximately 3 mm to several mm, while the MIG weld bead 42 is dug into the mold 10 by approximately 1 mm. In addition, intermetallic compounds 16 are formed at the interfaces between the TIG weld bead 40 and the MIG weld bead 42 and the mold 10.

In order to form this intermetallic compound 16, the filler metal, i.e., the material of the wire 3 and the welding rod 38, is a material different from the mold material 10, which forms the intermetallic compound 16 at the interface with the mold material 10 when dissolved or mixed with the mold material 10. In this embodiment, the mold material 10 is Fe and the filler metal is Al, so that the intermetallic compound 16, such as _FeAl3 or _{Fe2Al5 ,} is formed. In order to form the intermetallic compound 16, it is sufficient to adjust welding conditions such as the welding temperature and the amount of filler metal supplied.

The intermetallic compounds 16 are 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, various Fe-Al based intermetallic compounds 16 such as _Fe3Al , _FeAl , _FeAl2 , _Fe2Al5 , _FeAl3 , _Fe2Al6 , _{and Fe2Al9} are formed at the weld interface. These intermetallic compounds 16 have higher Vickers hardness and greater brittleness than the original metals Fe and _Al . Among these, _FeAl3 and _Fe2Al5 in particular have higher Vickers hardness and greater brittleness than the original metals. The type and composition ratio of the intermetallic compounds 16 formed can be adjusted by welding conditions such as the welding temperature and the amount of filler material supplied.

By changing the combination of materials for the mold material 10 and filler metal, it is possible to form intermetallic compounds 16 other than Fe-Al-based compounds. For example, if Ti or Ni is used for the mold material 9 and Al is used for the filler metal, it is possible to form intermetallic compounds 16 such as Ti-Al-based or Ni-Al-based compounds. If Ni is used for the mold material 9 and Ti is used for the filler metal, it is possible to form Ni-Ti-based intermetallic compounds 16. Intermetallic compounds generally have a higher Vickers hardness and are more brittle than the original metals, making them more susceptible 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 filler metal, making it more susceptible to cracking.

The thickness of the intermetallic compound 16 affects the bond strength at the interface. The thicker the intermetallic compound 16, the lower the bond strength at the interface, making it more susceptible to cracks. On the other hand, the thinner the intermetallic compound 16, the higher the bond strength at the interface. For this reason, 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 be thick. Specifically, it is preferable that it be 1 μm or thicker. The thickness of the intermetallic compound 16 can be adjusted by adjusting welding conditions such as the welding time and the amount of filler metal supplied.

<Step C2: Step of adding a framework to the original shape of the parabolic antenna mirror plate>
Next, a process of additively manufacturing a framework for 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 C1 by additive manufacturing using the DED method, to form the prototype 31 of the parabolic antenna.

As explained in Figure 11, the 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 the topology-optimized design shape for the parabolic antenna reflector plate.

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 embodiment 1.

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

As explained in Figure 12, a hook 33 is attached to the framework 30 of the shaped parabolic antenna prototype 31, and while a slight upward force is applied using a wire rope 32 connected to the hook 33, a mechanical impact is applied to the interface between the mold material 11 and the parabolic antenna prototype 31 using a wooden mallet. By doing this, the mold material 10 and the parabolic antenna prototype 31 begin to peel from the intermetallic compound 16 at the interface, and the parabolic antenna prototype 31 is completely released from the mold material 10.

In this embodiment, a mechanical shock is applied, but the means of applying the shock in this disclosure are 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 shock or vibration does not necessarily have to be directly at the interface between the mold 10 and the parabolic antenna prototype 31; it may be indirect, even at a location other than the interface, as long as the shock or vibration is applied to the interface.

In addition to applying impact or vibration, for example, the mold material 10 can be fixed with an anchor and the parabolic antenna prototype 31 can be pulled little by little to separate it from the mold. Alternatively, the mold material 10 and the parabolic antenna prototype 31 can be heated and separated from each other by the difference in the amount of thermal expansion that arises from the difference in the thermal expansion coefficients of the two. Specifically, this can be done by placing them in a furnace, or by placing a heat source and causing localized separation from the mold material 10 while gradually moving the position of the heat source to promote separation.

<Step C4: Step of mirror-finishing the original shape of the parabolic antenna mirror plate>
Finally, a step of mirror-finishing the parabolic antenna prototype 31 is carried out. The parabolic antenna prototype 31 released in step C3 is mirror-finished.

A mirror finish is applied to the mirror side surface of the parabolic antenna prototype 31. The mirror finish can 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 way, the parabolic antenna according to this embodiment is manufactured.

<Action Effect 1C>
As described with reference to Figure 17, 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. MIG welding has lower energy than TIG welding, so the MIG weld beads 42 are weakly bonded to the mold 10, while the TIG weld beads 40 are relatively strongly bonded to the mold 10. By forming the TIG weld beads 40 that are relatively strongly bonded to the mold 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 10 and the parabolic antenna prototype 31 made up of these weld beads. In this way, it is possible to control the releasability of the parabolic antenna prototype 31 from the mold 10.

<Action Effect 2C>
In this embodiment, unlike the first embodiment, a parabolic antenna base 29 and a framework 30 are continuously and integrally molded to form a parabolic antenna base 31. Therefore, in this embodiment, unlike the first embodiment, a parabolic antenna can be manufactured instead of a parabolic antenna base. On the other hand, in order to complete the parabolic antenna in the first embodiment, after manufacturing the parabolic antenna base in the first embodiment, it is necessary to connect or integrally mold a framework that supports the parabolic surface from behind.

<Action Effect 3C>
As illustrated in FIG. 17 , before being released from the mold 10, the original 29 of the parabolic antenna mirror plate according to this embodiment has a depth of about several millimeters in the area of the TIG weld bead 40 and about 1 mm in the area of the MIG weld bead 42. Therefore, the original 29 of the parabolic antenna mirror plate has a localized surface roughness on the order of several millimeters on the mirror-side surface, which is the height difference between the area of the TIG weld bead 40 and the area of the MIG weld bead 42. On the other hand, the original 59 of the parabolic antenna mirror plate according to the comparative example illustrated in FIG. 10 has an overall surface roughness on the order of several 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 several 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.

Embodiment 4.
A method for manufacturing a parabolic antenna according to the fourth embodiment will now 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 will explain steps D1 to D4.

<Step D0: Step of manufacturing mold material>
First, a process for manufacturing a mold material is carried out. Details of this process will be explained below with reference to FIGS. 18 to 21.

Figure 18 is an oblique view of the mold base 49, which is part of the original mold 11 of the parabolic antenna mirror plate in embodiment 4. The mold base 49 is the part that forms the base of the original mold 11 of the parabolic antenna mirror plate. When manufacturing 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 concave surface in the depth direction. In addition, 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 concave portion of the mold base 49 is shaped like a grid. The reinforcing members 43 and 44 were machined to a thickness of 10 mm using hot-rolled steel SS400 (JIS standard) and prepared by cutting them out to fit together. Additionally, rings 45 are attached to the upper end surfaces of reinforcing members 43 and 44, defining the outermost periphery of the recess in mold base 49. A zinc-based rust inhibitor is applied to the recess in mold base 49 with a brush and allowed to dry thoroughly.

In this embodiment, a large parabolic antenna with a diameter of 2 m is manufactured, and therefore the mold material is also large. For this reason, due to cost considerations and size constraints, 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.

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

Figure 20 is a perspective view of the original mold 11 of the parabolic antenna mirror plate according to the fourth embodiment. The mold 11 is the mold for the original 29 of the parabolic antenna mirror plate. The mold 11 was manufactured by temporarily fixing #300 stainless steel mesh 46 in the crisscross recess of the mold base 49 described in Figures 18 and 19, and welding the areas where they come into contact. The original 29 of the parabolic antenna mirror plate is additively manufactured on top of the stainless steel mesh 46. When laying the stainless steel mesh 46 in the crisscross recess, care must be taken to prevent the stainless steel mesh 46 from loosening in the hollow areas that form the gaps between the crisscross sections.

Stainless steel mesh 46 is a mesh-like sheet material with stainless steel threads woven into it. However, other sheet materials may be used instead of stainless steel mesh 46, as long as they can be laid out in the recesses of the mold base 49 and melt due to the heat generated during welding to form intermetallic compounds 16 between the reinforcing materials 43 and 44 and the filler metal.

The welding of the stainless steel mesh 46 to the reinforcing members 43 and 44 was performed using additive manufacturing equipment 200. A 1.2 mm diameter A5183 (JIS standard) welding aluminum wire was used for 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 is formed in the laser-welded area. In the area where the grid-shaped weld bead 47 is formed, the stainless steel mesh 46 is melted by the heat during welding. As a result, the grid-shaped weld bead 47 is welded to the reinforcing members 43 and 44 that support the stainless steel mesh 46 as a base. An intermetallic compound 16 is formed at the interface between the grid-shaped weld bead 47 and the reinforcing members 43 and 44.

Figure 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 laid out on the mold base 49, and the mold base 49 and the stainless steel mesh 46 are welded together at their contact points with 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, forming an intermetallic compound 16.

In order to form this intermetallic compound 16, the filler material is a material that is different from the mold material 11 and that, 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 material base 49, which is a part of the mold material 11. In this embodiment, the mold material 11 is Fe and the filler material is Al, so that the intermetallic compound 16, such as _FeAl3 or _{Fe2Al5 ,} is formed. In order to form the intermetallic compound 16, it is sufficient to adjust welding conditions such as the welding temperature and the amount of filler material supplied.

The intermetallic compounds 16 are 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, various Fe-Al based intermetallic compounds 16 such as _Fe3Al , _FeAl , _FeAl2 , _Fe2Al5 , _FeAl3 , _Fe2Al6 , _{and Fe2Al9} 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, _FeAl3 and _Fe2Al5 in particular have higher Vickers hardness and greater brittleness than the original metals. The type and composition ratio of the intermetallic compounds 16 formed can be adjusted by welding conditions such as the welding temperature and the amount of filler material supplied.

By changing the combination of materials for the mold material 11 and filler metal, it is possible to form intermetallic compounds 16 other than Fe-Al-based compounds. For example, if Ti or Ni is used for the mold material 11 and Al is used for the filler metal, it is possible to form intermetallic compounds 16 such as Ti-Al-based or Ni-Al-based intermetallic compounds. If Ni is used for the mold material 11 and Ti is used for the filler metal, it is possible to form Ni-Ti-based intermetallic compounds 16. Intermetallic compounds generally have a higher Vickers hardness and are more brittle than the original metals, making them more susceptible 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 11 and filler metal, making it more susceptible to cracking.

The thickness of the intermetallic compound 16 affects the bond strength at the interface. The thicker the intermetallic compound 16, the lower the bond strength at the interface, making it more susceptible to cracks. On the other hand, the thinner the intermetallic compound 16, the higher the bond strength at the interface. For this reason, 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 it be 1 μm or thicker. The thickness of the intermetallic compound 16 can be adjusted by adjusting welding conditions such as the welding time and the amount of filler metal supplied.

<Step D1: Step of forming the prototype of the 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.

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 connected to form the base 29 of the parabolic antenna mirror plate on the mold 11. The build-up welding was performed using the same additive manufacturing equipment 200 used in process D0, with only 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 areas of the mold base 49.

Figure 22 is a cross-sectional view of a prototype 29 of a parabolic antenna mirror plate according to embodiment 4. 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 Figure 21. The prototype 29 of the parabolic antenna mirror plate consists of a lattice-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 lattice-shaped weld bead 47, and therefore the lattice-shaped weld bead 47 also becomes part of the prototype 29 of the parabolic antenna mirror plate.

As shown in Figure 22, at the interface between the lattice-shaped weld bead 47 and the base 49 of the mold (reinforcement material 43), no stainless steel mesh 46 is present, but intermetallic compound 16 is formed. As mentioned above, this is because the stainless steel mesh 46 is melted to weld the lattice-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 mentioned 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 lattice-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, of the parts that make up the base 29 of the parabolic antenna mirror plate, the build-up weld portion 48 is not joined to the mold 11, and the lattice-shaped weld bead 47 is joined to the mold 11 via the intermetallic compound 16.

<Step D2: Step of adding a framework to the original shape of the parabolic antenna mirror plate>
Then, a process of additively manufacturing a framework for 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.

As explained in Figure 11, the 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 the topology-optimized design shape for the parabolic antenna reflector plate.

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 embodiment 1.

<Step D3: Step of releasing the original shape of the parabolic antenna>
Furthermore, a step of releasing the original form of the parabolic antenna mirror plate is carried out. The original form 31 of the parabolic antenna formed in step D2 is released from the mold material 11.

As explained in Figure 12, a hook 33 is attached to the framework 30 of the shaped parabolic antenna prototype 31, and while a slight upward force is applied using a wire rope 32 connected to the hook 33, a mechanical impact is applied to the interface between the mold material 11 and the parabolic antenna prototype 31 using a wooden mallet. By doing this, the mold material 11 and the parabolic antenna prototype 31 begin to peel from the intermetallic compound 16 at the interface, and the parabolic antenna prototype 31 is completely released from the mold material 11.

In this embodiment, a mechanical shock is applied, but the means of applying the shock in this disclosure are not limited, and for example, a thermal shock may be applied. Furthermore, vibration may be applied instead of a shock, such as ultrasonic vibration. The application of shock or vibration does not necessarily have to be directly at the interface between the mold material 11 and the parabolic antenna prototype 31; it may be indirect, even at a location other than the interface, as long as the shock or vibration is applied to the interface.

In addition to applying impact or vibration, for example, the mold material 11 can be fixed with an anchor and the parabolic antenna prototype 31 can be pulled little by little to separate it from the mold. Alternatively, the mold material 11 and the parabolic antenna prototype 31 can be heated and separated from each other by the difference in the amount of thermal expansion that arises from the difference in the thermal expansion coefficients of the two. Specifically, this can be done by placing them in a furnace, or by placing a heat source and causing localized separation from the mold material 11 while gradually moving the position of the heat source to promote separation.

In addition, as in the embodiment described in Figure 7, the original 31 of the parabolic antenna mirror plate can be released from the mold 11 by removing its constituent parts from the mold 11. Specifically, as explained with reference to Figure 21, the reinforcing member 44 is removed by pulling it out from below relative to the reinforcing member 43. In this way, a mechanical shock can be applied near the point where the original 29 of the parabolic antenna mirror plate is to be peeled off from the mold 11, allowing for more efficient release.

<Step D4: Step of mirror-finishing the original shape of the parabolic antenna mirror plate>
Finally, a step of mirror-finishing the parabolic antenna prototype 31 is carried out. The parabolic antenna prototype 31 released in step D3 is mirror-finished.

A mirror finish is applied to the mirror side surface of the parabolic antenna prototype 31. The mirror finish can 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 way, the parabolic antenna according to this embodiment is manufactured.

<Action Effect 1D>
Unlike the first to third embodiments, the present 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 the present 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 the present embodiment.

<Action Effect 2D>
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, making it easier to separate the original form 29 of the parabolic antenna mirror plate from the mold material 11.

<3D Action and Effect>
In this embodiment, unlike the first embodiment, a parabolic antenna base 29 and a framework 30 are continuously and integrally molded to form a parabolic antenna base 31. Therefore, in this embodiment, unlike the first embodiment, a parabolic antenna can be manufactured instead of a parabolic antenna base. On the other hand, in order to complete the parabolic antenna in the first embodiment, after manufacturing the parabolic antenna base in the first embodiment, it is necessary to connect or integrally mold a framework that supports the parabolic surface from behind.

<Action and 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. As described in FIG. 8 , the specular surface 18a of the original parabolic antenna mirror plate 29 is the surface released from the mold 11, which has a small surface roughness. The specular surface 18a of the original parabolic antenna mirror plate 29 is also the specular surface of the original parabolic antenna 31. 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.

1. Printing head, 2. Bobbin, 3. Wire, 9, 10, 11. Mold material, 16. Intermetallic compound, 19. Processing plate, 20. Hook catch, 21. Fixing jig, 29. Parabolic antenna mirror plate prototype, 30. Frame, 31. Parabolic antenna prototype, 39. Weld bead, 40. TIG weld bead, 42. MIG weld bead, 43, 44. Reinforcement material, 45. Ring, 46. Stainless steel mesh, 47. Grid-shaped weld bead, 48. Weld build-up, 49. Mold base, 200, 201. Additive manufacturing equipment, 300. TIG welding machine

Claims (24)

A process 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 be used 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 peeling off the original shape of the parabolic antenna mirror plate from the mold material to release the original shape of the parabolic antenna mirror plate from the mold material;
and a step of mirror-finishing the original shape of the parabolic antenna mirror plate.
A manufacturing method for a parabolic antenna mirror plate. The method for manufacturing a parabolic antenna mirror plate according to claim 1, wherein 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. The method for manufacturing a parabolic antenna mirror plate according to claim 1 or 2, characterized in that the step of releasing the original form of the parabolic antenna mirror plate 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 mirror plate. The method for manufacturing a parabolic antenna mirror plate according to claim 3, wherein the method for applying the impact or vibration is either mechanical impact, thermal shock, or ultrasonic vibration. The method for manufacturing a parabolic antenna mirror plate according to claim 1 or 2, characterized in that the step of releasing the original form of the parabolic antenna mirror plate from the mold is performed by fixing the mold with an anchor and pulling the original form of the parabolic antenna mirror plate from the mold. The method for manufacturing a parabolic antenna mirror plate according to claim 1 or 2, wherein the step of releasing the original form 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. The method for manufacturing a parabolic antenna reflector plate according to any one of claims 1 to 6, wherein the intermetallic compound is an Fe-Al, Ti-Al, Ni-Al, or Ni-Ti intermetallic compound. 8. The method for manufacturing a parabolic antenna reflector plate according to claim 7, wherein the intermetallic compound is _FeAl3 or _{Fe2Al5 .} The method for manufacturing a parabolic antenna mirror plate described in any one of claims 1 to 8, characterized in that the thickness of the intermetallic compound is 1 μm or more. A process 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 will be used as a mold for the parabolic antenna mirror plate, and 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 process of 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;
a step of peeling off the original form of the parabolic antenna from the mold material to release the original form of the parabolic antenna from the mold material;
and a step of mirror-finishing the original form of the parabolic antenna. The method for manufacturing a parabolic antenna described 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. The method for manufacturing a parabolic antenna described in claim 10 or 11, characterized in that the step of releasing the parabolic antenna prototype from the mold material is carried out by applying impact or vibration to the interface between the mold material and the parabolic antenna prototype. The method for manufacturing a parabolic antenna according to claim 12, wherein the method for applying the shock or vibration is either mechanical shock, thermal shock, or ultrasonic vibration. The method for manufacturing a parabolic antenna described in claim 10 or 11, characterized in that the step of releasing the original form of the parabolic antenna from the mold material is performed by fixing the mold material with an anchor and pulling the original form of the parabolic antenna from the mold material. The method for manufacturing a parabolic antenna described in claim 10 or 11, characterized in that the step of releasing the parabolic antenna prototype from the mold material involves heating the mold material and the parabolic antenna prototype, and releasing them by using the difference in thermal expansion amounts resulting from the difference in the thermal expansion coefficients of the two. The method for manufacturing a parabolic antenna described in any one of claims 10 to 15, characterized in that the intermetallic compound is an Fe-Al-based, Ti-Al-based, Ni-Al-based, or Ni-Ti-based intermetallic compound. The method for manufacturing a parabolic antenna according to claim 16, wherein the intermetallic compound is _FeAl3 or _{Fe2Al5 .} The method for manufacturing a parabolic antenna described in any one of claims 10 to 17, characterized in that the thickness of the intermetallic compound is 1 μm or more. Before the step of forming the original shape of the parabolic antenna mirror plate, a step of forming TIG welding beads at intervals on the mold material is added,
The method for manufacturing a parabolic antenna according to any one of claims 10 to 18, characterized in that the step of forming the original shape of the parabolic antenna mirror plate includes forming a MIG welding bead along the TIG welding bead. The mold member has a mold member base into which a plurality of reinforcing members are fitted, and a sheet member laid on the mold member base,
The base of the mold and the sheet member are welded together by a weld bead at their contacting portions,
The method for manufacturing a parabolic antenna according to any one of claims 10 to 19, characterized in that a prototype of the parabolic antenna is additionally manufactured on the sheet member. The method for manufacturing a parabolic antenna described in claim 20, characterized in that the portion of the base of the mold where the sheet material is laid out is in a grid pattern. 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. The method for manufacturing a parabolic antenna described in claim 22, characterized in that additive manufacturing using the DED method is performed along the weld bead at an output that does not melt the sheet member. The method for manufacturing a parabolic antenna described in claim 22 or 23, characterized in that the weld bead is part of the original shape of the parabolic antenna mirror plate.