Patent Description:
The present application claims priority to <CIT>.

Known methods of manufacturing rubber products include a method of manufacturing a product by placing unvulcanized rubber in a mold that matches the shape of the product and vulcanizing the rubber by applying heat and pressure, as in Patent Literature (PTL) <NUM>, and a method of placing unvulcanized rubber in a mold that is larger than the product, vulcanizing the rubber by applying heat and pressure, and then machining the rubber by cutting or the like to yield the shape of the product. Further reference may be made to methods of manufacturing rubber products disclosed in PTL2 and PTL3.

However, in the method of using a mold that matches the shape of the product, the mold needs to be modified or made anew when a change in the shape of the product occurs for a reason such as a change in product specifications. The production costs and the time and effort for processing have thus been problematic. Furthermore, in a method of using a mold larger than the product, there has been room for improvement in the manufacturing accuracy, such as dimensional accuracy during machining, depending on the physical properties of the rubber.

It is an aim of the present disclosure to provide a method of manufacturing a rubber product that can flexibly respond to changes in the shape of a product and can achieve high manufacturing accuracy.

We carefully studied how to solve the aforementioned problem and concluded that a desired product shape can be obtained without using a mold by considering the shape of the desired product as a laminated body of thin pieces yielded when cutting on a number of planes orthogonal to a predetermined axis, and by then stacking and bonding the thin pieces together to manufacture the product. After further investigating the aforementioned additive manufacturing, we discovered that the additive manufacturing can be applied to rubber products by performing appropriate treatment on the powder of uncrosslinked rubber to be used as a material and further crosslinking the powder of the uncrosslinked rubber, thereby completing the present disclosure.

A method of manufacturing a rubber product according to the present disclosure is a method of manufacturing a rubber product by bonding a plurality of thin pieces on a manufacturing table, the method including:.

According to the present disclosure, a method of manufacturing a rubber product that, without use of a mold, can flexibly respond to changes in the shape of a product and can achieve high manufacturing accuracy can be provided.

Methods of manufacturing rubber products according to embodiments of the present disclosure are described below. <FIG> is a flowchart illustrating an outline of a method of manufacturing a rubber product according to an embodiment of the present disclosure.

As illustrated in <FIG>, the method of manufacturing a rubber product according to the present disclosure is a method of manufacturing a rubber product by bonding a plurality of thin pieces on a manufacturing table, and as illustrated in <FIG>, the method includes treating uncrosslinked rubber powder, which is a material of the rubber product, to prevent mutual adhesion of the uncrosslinked rubber powder (an adhesion prevention treatment step S <NUM>), acquiring data on a plurality of thin pieces of the rubber product (thin piece data acquisition step S2), setting a manufacturing table to a state in which manufacturing can start (preparation step S3), supplying raw rubber powder, on which the adhesion prevention treatment has been performed, onto a surface of the manufacturing table uniformly in a layer of a thickness corresponding to a thin piece (first raw rubber powder supply step S4), irradiating the raw rubber powder layer with an electron beam according to a shape corresponding to the thin piece to crosslink the irradiated portion (first crosslinking step S5), adjusting relative positions of a surface of a crosslinked portion in the raw rubber powder layer and a surface of the manufacturing table to align the surface of the crosslinked portion with the surface of the manufacturing table (post-treatment step S6), supplying the raw rubber powder onto the surface of the crosslinked portion uniformly in a layer of a thickness corresponding to the next thin piece to be stacked on the thin piece (second raw rubber powder supply step S7), and irradiating the raw rubber powder layer with an electron beam according to a shape corresponding to the next thin piece to crosslink the irradiated portion (second crosslinking step S8). The post-treatment step S6, the second raw rubber powder supply step S7, and the second crosslinking step S8 are sequentially repeated to bond the plurality of thin pieces together and manufacture the rubber product.

<FIG> illustrates a rubber product <NUM>, which is an example of a rubber product to be manufactured by the method of manufacturing a rubber product according to the present embodiment. As illustrated in <FIG>, the rubber product <NUM> can, for example, have a cylindrical shape.

Here, thin pieces refer to layers that are divided by cutting at numerous planes orthogonal to the axis along the stacking direction of the rubber product to be manufactured.

In the example of the rubber product <NUM>, when the Z-axis direction is the stacking direction (height), a plurality of sliced layers are formed by cutting the cylindrical three-dimensional shape at numerous planes orthogonal to the Z-axis direction. Each layer in the plurality of sliced layers illustrated in <FIG> is a thin piece of the rubber product <NUM>. The stacking direction in additive manufacturing of the rubber product <NUM> refers to the Z-axis direction in <FIG>, but a suitable direction can be used as the stacking direction according to the shape, size, and the like of the rubber product to be manufactured.

Although the thin pieces L1 to L3 from the first layer to the third layer in the Z-axis direction of the rubber product <NUM> are illustrated in <FIG>, the rubber product <NUM> is actually converted into data on thin pieces L1 to LN (N is a natural number) for the number of layers required to manufacture the rubber product <NUM>.

In this way, the shape of the rubber product <NUM> is converted into the data on a plurality of thin pieces, and the thin pieces are then stacked and bonded together based on this data to manufacture the rubber product <NUM>.

In the adhesion prevention treatment step S <NUM>, uncrosslinked rubber powder, which is a material of the rubber product <NUM>, is treated to prevent mutual adhesion of the uncrosslinked rubber powder.

A material suitable for rubber products can be used as the material forming the uncrosslinked rubber powder in the present disclosure. Powders of polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), halogenated butyl rubber, acrylonitrile butadiene rubber (NBR), and other synthetic rubbers, in addition to natural rubber (NR), can be used as the rubber powder. Among these, powders of natural rubber (NR), styrene-butadiene copolymer rubber (SBR), and polybutadiene rubber (BR) are preferred. These rubber powders may be used alone, or a combination of two or more types thereof may be used.

The uncrosslinked rubber powder may also contain other materials other than natural rubber and synthetic rubber. As the other materials, fillers such as carbon black and silica, softeners, age resistors, zinc oxide, crosslinking accelerators, and the like may be selected as appropriate within a range not detrimental to the aim of the present disclosure. The other materials may be added not only by inclusion in the uncrosslinked rubber powder in advance but also after the treatment to prevent adhesion of the uncrosslinked rubber powder.

Furthermore, the uncrosslinked rubber powder includes calcium oxide, as an example of other materials. By the addition of calcium oxide into the uncrosslinked rubber powder, even when the rubber is heated to a temperature higher than the melting point during the crosslinking of the rubber, bubbles that might be generated in the rubber by heat can be suppressed, and cracks or tears can be prevented from occurring at the areas with bubbles.

The treatment on the uncrosslinked rubber powder to prevent mutual adhesion of the powder refers to the treatment for preventing the powder particles from adhering to each other and is performed by coating the surface of the uncrosslinked rubber powder with an adhesion prevention agent. As the adhesion prevention agent, any of synthetic resin, talc, silica, calcium carbonate, calcium stearate, zinc stearate, carbon black, and the like, for example, or any combination thereof, can be used.

While the means for coating the surface of the uncrosslinked rubber powder with the adhesion prevention agent is not particularly limited, a powdered adhesion prevention agent having a diameter smaller than that of the uncrosslinked rubber powder can be stirred and mixed with the uncrosslinked rubber powder to coat the surface of the uncrosslinked rubber powder, for example. The surface of the uncrosslinked rubber powder may also be coated by applying a dissolved solution or an aqueous dispersion of the adhesion prevention agent to the surface of the uncrosslinked rubber powder. When a dissolved solution or aqueous dispersion of the adhesion prevention agent is used, a coating layer of uniform thickness can easily be formed on the surface of the uncrosslinked rubber powder, but a step of drying the uncrosslinked rubber powder is required after the application. A powdered adhesion prevention agent is preferably used to prevent an increase in the number of production steps.

The adhesion prevention treatment step may be a step included in the preparation of the uncrosslinked rubber powder that becomes the material of the rubber product <NUM> or may be a separate step performed after the preparation of the uncrosslinked rubber powder.

According to the adhesion prevention treatment step, mutual adhesion of the uncrosslinked rubber powder can be prevented. That is, lumps are not formed due to mutual adhesion of the uncrosslinked rubber powder. This facilitates handling of the uncrosslinked rubber powder. In particular, when the uncrosslinked rubber powder is stored or applied to the additive manufacturing apparatus <NUM> described below, the manufacturing accuracy of the rubber product can be improved, and the uncrosslinked rubber powder can be easily stored and supplied.

The average diameter of the uncrosslinked rubber powder (raw rubber powder) to which the adhesion prevention treatment is applied is preferably from <NUM> to <NUM>. By the average diameter being <NUM> or more, floating during storage and other times can be suppressed, and the mutual adhesion of the raw rubber powder can more effectively be suppressed. By the average diameter being <NUM> or less, the manufacturing accuracy of the rubber product can be further improved.

In the below-illustrated steps from the preparation step onwards, the raw rubber powder is used to manufacture the rubber product <NUM>. The manufacturing apparatus is not particularly limited as long as the method of manufacturing a rubber product according to the present disclosure can be implemented, but an additive manufacturing apparatus <NUM> with the following form can, for example, be used.

<FIG> is a perspective view schematically illustrating the configuration of the additive manufacturing apparatus <NUM>, and <FIG> is a cross-sectional view schematically illustrating the configuration of the additive manufacturing apparatus <NUM>. <FIG> schematically illustrates a cross-section along line II-II of <FIG>.

As illustrated in <FIG> and <FIG>, the additive manufacturing apparatus <NUM> includes a manufacturing table <NUM>, a recoater <NUM>, and electron beam irradiation means <NUM>. The manufacturing table <NUM> includes a manufacturing unit <NUM>, a supply plate <NUM>, and a raw material supplier <NUM>.

The manufacturing unit <NUM> includes a manufacturing base <NUM> and a raising/lowering mechanism <NUM>, and the manufacturing base <NUM> includes a surface 111a for manufacturing rubber products. The manufacturing base <NUM> has a circular cylinder shape in the illustrated example but may have a polygonal cylinder shape or the like. The manufacturing base <NUM> can be raised and lowered in the up-down direction (Z-axis direction) by the raising/lowering mechanism <NUM>. The raising/lowering mechanism <NUM> can, for example, be provided with a piston member using hydraulic pressure or pneumatic pressure, or with a ball screw.

The supply plate <NUM> is disposed around the manufacturing unit <NUM> and includes a plate-like portion <NUM> and a support <NUM> (not illustrated). The plate-like portion <NUM> includes a surface 121a onto which raw rubber powder can be supplied. The plate-like portion <NUM> has a shape in which a part of a plate-like member is perforated according to the outer circumferential shape of the cylindrical manufacturing base <NUM> in the illustrated example, but the shape is not particularly limited. The support <NUM> can be any columnar or plate-like shape that supports the plate-like portion <NUM>. The support <NUM> may be provided with a raising/lowering mechanism, but is not coupled to raising/lowering operations by the raising/lowering mechanism <NUM> of the manufacturing unit <NUM>.

The raw material supplier <NUM> has a tank-shaped or box-shaped raw material housing <NUM>, which opens to the surface 121a of the supply plate <NUM> and extends in the thickness direction (Z-axis direction) of the supply plate <NUM>, and a raising/lowering mechanism <NUM>. The raw material housing <NUM> can contain raw rubber powder. A bottom portion 131b of the raw material housing <NUM> can be raised and lowered in the Z-axis direction by the raising/lowering mechanism <NUM>, and the raw rubber powder housed in the raw material housing <NUM> can be pushed out onto the surface 121a by the raising/lowering operation of the bottom portion 131b. The raising/lowering mechanism <NUM> can, for example, be a mechanism provided with a piston using hydraulic pressure or pneumatic pressure, or with a ball screw.

The arrangement and configuration of the raw material supplier is not limited to the example of the raw material supplier <NUM>. A configuration may be adopted in which a raw material housing and a nozzle are included, the raw material supplier is arranged at a position (upper side) separated in the Z-axis direction from the surface 121a, and the raw rubber powder is discharged onto the surface 121a.

The recoater <NUM> has a roller shape and is disposed on the surface 121a. The recoater <NUM> is connected at both axial ends to a drive mechanism (not illustrated) and can be moved while rolling in the X-axis direction. The recoater <NUM> can be separated from the surface 121a by a certain distance in the Z-axis direction, and this distance can be adjusted according to the thickness of the layer to be supplied onto the surface 121a. As illustrated in <FIG>, the axial length of the recoater <NUM> is larger than the longitudinal length of the opening in the surface 121a of the raw material supplier <NUM>. The recoater <NUM> is not limited to a member having a roller shape or a rotating member and may, for example, be a plate-like member (blade).

In the additive manufacturing apparatus <NUM>, the electron beam irradiation means <NUM> is arranged at a distance in the Z-axis direction with respect to the surface 111a. Although any electron beam irradiation means <NUM> can be used, at least one electron beam source <NUM> and an electron beam adjusting means <NUM> are preferably used.

The electron beam source <NUM> can be a thermal electron emission type electron gun. More specifically, for example, thermal electrons are generated by heating a cathode formed by tungsten, LaB<NUM>, CeB<NUM>, or the like, and an electron beam is generated by accelerating the thermal electrons.

The electron beam adjusting means <NUM> can, for example, include a magnetic field generator 152a and a focus controller 152b. Using the magnetic force of a permanent magnet, an electromagnet, or the like, the magnetic field generator 152a can adjust the convergence, deflection, and the like of the electron beam generated by the electron beam source <NUM>. The focus controller 152b can also adjust the focus of the electron beam at the irradiation target using an optical lens, an electromagnetic lens, or the like. Although one electron beam source <NUM> is depicted in the illustrated example, a plurality of electron beam sources <NUM> may be included, each of which may be controlled under different irradiation conditions.

By being housed in a chamber (not illustrated) or the like, the additive manufacturing apparatus <NUM> can be used in a high vacuum environment during operation of the electron beam irradiation means <NUM>.

Furthermore, the additive manufacturing apparatus <NUM> can be connected over a network to a control device <NUM>. The control device <NUM> includes a hardware processor, such as a central processing unit, and includes a thin piece data acquisition interface <NUM> and a manufacturing controller <NUM>.

The thin piece data acquisition interface <NUM> can acquire the data on the thin pieces necessary for manufacturing the rubber product <NUM>.

The manufacturing controller <NUM> can control the additive manufacturing by providing instructions and information, via a network, to each component of the additive manufacturing apparatus <NUM> based on the data on the thin pieces. That is, the manufacturing controller <NUM> can control the operations of the manufacturing table <NUM>, the recoater <NUM>, the electron beam irradiation means <NUM>, and the like, which configure the additive manufacturing apparatus <NUM>.

Each of the steps from the thin piece data acquisition process S2 onwards in the method of manufacturing a rubber product according to the present embodiment will be described below in detail with an example using the additive manufacturing apparatus <NUM>.

In the thin piece data acquisition step S2, the thin piece data on the rubber product <NUM>, which is necessary for manufacturing the rubber product <NUM>, is acquired by the thin piece data acquisition interface <NUM> of the control device <NUM>.

The thin piece data can, for example, be acquired by converting three-dimensional manufacturing data on the rubber product <NUM>. More specifically, the thin piece data acquisition interface <NUM> acquires the three-dimensional manufacturing data from an apparatus such as another computer that is connected to the control device <NUM> or that can transmit information to the control device <NUM>. Here, the three-dimensional manufacturing data for manufacturing the rubber product <NUM> is, for example, three-dimensional manufacturing data designed by three-dimensional CAD, or three-dimensional manufacturing data captured by a three-dimensional scanner, digitizer, or the like. The three-dimensional manufacturing data may be converted into Standard Triangulated Language (STL) format, in which the surface of the three-dimensional rubber product <NUM> is represented as a collection of triangles. This three-dimensional manufacturing data on the rubber product <NUM> is acquired by the thin piece data acquisition interface <NUM> and converted into data on thin pieces L1 to LN (N is a natural number).

Three-dimensional manufacturing data may also be converted to thin piece data by an apparatus such as another computer that is connected to the control device <NUM> or is capable of transmitting information to the control device <NUM>, and the thin piece data may then be acquired by the thin piece data acquisition interface <NUM>.

Next, the preparation step S3 will be described with reference to <FIG> and <FIG>.

To start manufacturing based on the thin piece data, the manufacturing table <NUM> is set to a state in which the manufacturing of the rubber product can be started in the preparation step S3. That is, the relative positions of the surface 111a of the manufacturing unit <NUM> and the surface 121a of the supply plate <NUM> are adjusted to align the surface 111a with the surface 121a. In other words, the surface 111a and the surface 121a are arranged so that they extend to the same position and are substantially flush. Extending to the same position refers to being at the same position in the Z-axis direction and extending in the X-axis direction.

Of the two ends, in the X-axis direction, of the surface 121a of the supply plate <NUM>, the recoater <NUM> is preferably arranged to be located at the end on the raw material supplier <NUM> side before the first raw rubber powder supply step S4.

A base material (not illustrated) made of a material that can be removed from the rubber product <NUM> may be disposed beforehand on the surface 111a of the manufacturing unit <NUM> so that the rubber product <NUM> can be easily removed from the surface 111a of the manufacturing unit <NUM> after all the steps are finished and the bonding of all the thin pieces is completed.

Next, the first raw rubber powder supply step S4 will be described with reference to <FIG> and <FIG>. In <FIG> and <FIG> and subsequent figures, the control device <NUM> is omitted.

In the first raw rubber powder supply step S4, the raw rubber powder is supplied onto the surface of the manufacturing table <NUM> uniformly in a layer of a thickness corresponding to the thin piece L1.

In the example using the additive manufacturing apparatus <NUM>, first, the raw rubber powder is stored in the raw material housing <NUM> of the raw material supplier <NUM>, and the bottom portion 131b is raised by the raising/lowering mechanism <NUM> in a direction approaching the surface 121a in the Z-axis direction, so that an amount of raw rubber powder capable of forming a layer of a thickness corresponding to the thin piece L1 is disposed on the surface 121a of the supply plate <NUM>. After the raw rubber powder is disposed on the surface 121a, the recoater <NUM> is rolled to pass over the surface of the manufacturing table <NUM>, i.e., the surface 111a of the manufacturing unit <NUM> and the surface 121a of the supply plate <NUM>, thereby supplying the raw rubber powder onto the surface 111a of the manufacturing unit <NUM> and the surface 121a of the supply plate <NUM> uniformly in a layer of a thickness corresponding to the thin piece L1 to form a raw rubber powder layer m1. At this time, it is essential that the recoater <NUM> be rolled while maintaining a distance, from the surface 111a of the manufacturing unit <NUM> and the surface 121a of the supply plate <NUM>, of a thickness corresponding to the thin piece L <NUM>.

The thickness corresponding to the thin piece L1 can be controlled by the control device <NUM> based on the thin piece data. The thickness corresponding to the thin piece L1, that is, the thickness t1 of the raw rubber powder layer m1, can be adjusted according to the irradiation conditions of the electron beam described below, the average particle size of the raw rubber powder, and the like, but is preferably <NUM> or less for uniform crosslinking over the thickness direction.

Next, the first crosslinking step S5 will be described with reference to <FIG> and <FIG>.

In the first crosslinking step S5, the raw rubber powder layer m1 formed by the first raw rubber powder supply step S4 is irradiated with an electron beam according to a shape corresponding to the thin piece L1 to crosslink the irradiated portion.

The electron beam irradiation means is not particularly limited, but the electron beam irradiation means <NUM>, for example, can be used. The electron beam generated by the electron beam source <NUM> of the electron beam irradiation means <NUM> is converged and deflected by the magnetic field generator 152a, and the irradiation position is moved based on the thin piece data to scan the raw rubber powder layer m1. Furthermore, the focus controller 152b enables adjustment of the position where the electron beam achieves just focus, i.e., the focus.

When the raw rubber powder layer m1 is irradiated with the electron beam, the rubber molecules of the raw rubber powder are provided with energy by high-speed electrons. The high-speed electrons cleave the molecular bonds, which generates radicals, and the radicals react between molecular chains to form a three-dimensional structure, yielding a crosslinking reaction.

According to the electron beam crosslinking means, the location to be crosslinked can be changed by controlling the position where the electron beam is irradiated, thus eliminating the need to prepare a mold and other such hassle, and enabling a flexible response to changes in product shape. Furthermore, a high manufacturing accuracy can be achieved. Rubber products with complex shapes that are difficult to remove from a mold, or that cannot be manufactured with a mold, can also be manufactured.

The irradiation conditions of the electron beam can be controlled by the control device <NUM> based on the thin piece data on the rubber product <NUM> that is to be manufactured. The specific irradiation conditions of the electron beam can be adjusted appropriately according to factors such as the thickness of the raw rubber powder layer and the average diameter of the raw rubber powder.

For example, the focusing of the electron beam is preferably set to achieve just focus on the surface of the raw rubber powder layer to generate a sufficient crosslinking reaction in the rubber.

Although the temperature at the time of electron beam irradiation is not particularly limited, the first crosslinking step S5 is preferably performed in a temperature environment lower than the melting point of the rubber. According to the above configuration, the crosslinking reaction can be produced at a lower temperature than with means for vulcanizing rubber by heating. Bubbles that might be generated in the rubber by heating can therefore be suppressed, and cracks or tears can be prevented from occurring at the areas with bubbles.

Furthermore, the electron beam irradiation is preferably performed in a high vacuum environment to prevent deactivation of the radicals by oxygen. For example, when the additive manufacturing apparatus <NUM> is housed in a chamber or the like, a high vacuum is created in the chamber.

By the first crosslinking step S5, a crosslinked portion M1 can be formed in the raw rubber powder layer m1 as illustrated in <FIG> and <FIG>. In the illustrated example, a ring-shaped crosslinked portion M1 is formed, corresponding to the thin piece L1 of the rubber product <NUM>.

The post-treatment step S6 after the first crosslinking step S5 will be described with reference to <FIG> and <FIG>. In the post-treatment step S6, after the first crosslinking step S5, the relative positions of the surface of the crosslinked portion M1 in the raw rubber powder layer m1 and the surface of the manufacturing table <NUM> are adjusted to align the surface of the crosslinked portion M1 with the surface of the manufacturing table <NUM>. That is, in the illustrated example, the relative positions in the Z-axis direction of the surface of the crosslinked portion M1 and the surface 121a of the supply plate <NUM> are adjusted to align the surface of the crosslinked portion M1 with the surface 121a of the supply plate <NUM>. To adjust the relative positions, the manufacturing unit <NUM> can be lowered, by the thickness of the crosslinked portion M1 of the raw rubber powder layer m1, away from the surface 121a in the Z-axis direction using the raising/lowering mechanism <NUM>, for example, to align the surface of the crosslinked portion M1 with the surface 121a of the supply plate <NUM>.

The relative positions of the surface of the crosslinked portion M1 and the surface 121a of the supply plate <NUM> may be adjusted by raising and lowering the supply plate <NUM> relative to the manufacturing unit <NUM>.

Before or after the post-treatment step S6, a step of removing the uncrosslinked raw rubber powder remaining on the surface 121a of the supply plate <NUM> may be provided. The means for removing the uncrosslinked raw rubber powder is not particularly limited, but suction means, for example, may be used. Alternatively, a collection hole (not illustrated) opening to the surface 121a may be provided on the outer periphery of the manufacturing unit <NUM> in the supply plate <NUM>, and the uncrosslinked raw rubber powder may swept by a brush or blown by air to the collection hole and removed. A passage connecting the collection hole to the raw material housing <NUM> may be formed to reuse the uncrosslinked raw rubber powder in a subsequent step.

The second raw rubber powder supply step S7 will be described with reference to <FIG> is a schematic cross-sectional view illustrating the second raw rubber powder supply step S7 and schematically illustrates the manufacturing table <NUM>, the recoater <NUM>, and the raw rubber powder layer m1.

In the second raw rubber powder supply step S7, the raw rubber powder is supplied onto the surface of the manufacturing table <NUM> including the surface of the crosslinked portion M1, i.e., the surface of the crosslinked portion M1, the surface of the raw rubber powder layer m1, and the surface 121a of the supply plate <NUM>, uniformly in a layer of a thickness corresponding to the next thin piece L2 to be stacked on the thin piece L1.

As in the first raw rubber powder supply step, first, the bottom portion 131b of the raw material housing <NUM> is raised by the raising/lowering mechanism <NUM> in a direction approaching the surface 121a in the Z-axis direction, so that an amount of raw rubber powder capable of forming a layer of a thickness corresponding to the thin piece L2 is disposed on the surface 121a of the supply plate <NUM>. After the raw rubber powder is disposed on the surface 121a, the recoater <NUM> is rolled to pass over the surface 121a of the supply plate <NUM> and the surface of the crosslinked portion M1 to supply the raw rubber powder onto the surface of the crosslinked portion M1 as a raw rubber powder layer m2. At this time, it is essential that the recoater <NUM> be rolled while maintaining a distance, from the surface 121a of the supply plate <NUM> and the surface of the crosslinked portion M1, of a thickness corresponding to the thin piece L2. In the illustrated example, the raw rubber powder layer m2 is supplied on the crosslinked portion M1, the raw rubber powder layer m1 containing the crosslinked portion M1, and the surface 120a of the supply plate <NUM>.

The layer of a thickness corresponding to the thin piece L2 can be controlled by the control device <NUM> based on the thin piece data.

Next, the second crosslinking step S8 will be described with reference to <FIG>. In the second crosslinking step S8, the raw rubber powder layer m2 formed by the second raw rubber powder supply step S7 is irradiated with an electron beam according to a shape corresponding to the next thin piece L2 to crosslink the irradiated portion.

The electron beam irradiation means <NUM>, for example, can be used for the electron beam irradiation. The electron beam generated by the electron beam source <NUM> of the electron beam irradiation means <NUM> is converged and deflected by the magnetic field generator 152a, and the irradiation position is moved based on the thin piece data to scan the raw rubber powder layer. Furthermore, the focus controller 152b enables adjustment of the position where the electron beam achieves just focus, i.e., the focus.

The irradiation conditions of the electron beam may be the same as the irradiation conditions in the first crosslinking step S5, or may be different.

For example, in the first crosslinking step S5, the focusing of the electron beam may be controlled so that the electron beam achieves just focus on the surface of the raw rubber powder layer, and in the second irradiation step, a plurality of electron beam supply sources may be used and the electron beams controlled to achieve just focus on the surface of the raw rubber powder layer and on the boundary with the adjacent raw rubber powder layer immediately below the raw rubber powder layer. According to the above configuration, the raw rubber powder layer can be sufficiently crosslinked, and the crosslinked portions M1 and M2 of the adjacent raw rubber powder layers m1 and m2 can be bonded together.

The focusing of the electron beam can be controlled so that the focusing is always the same, or the focusing can be changed.

In the second crosslinking step S8, although the temperature at the time of electron beam irradiation is not particularly limited, the crosslinking is preferably performed in a temperature environment lower than the melting point of the rubber, as in the first crosslinking step S5. According to the above configuration, the manufacturing accuracy can be further enhanced, and deterioration of the rubber product due to heating can be prevented.

The second crosslinking step S8 enables the formation of a crosslinked portion, in the raw rubber powder layer, corresponding to the next thin piece. In <FIG>, the crosslinked portion M2, which is a ring-shaped layer corresponding to the thin piece L2 in the second layer from the bottom in the Z-axis direction of the rubber product <NUM>, is stacked onto and bonded to the crosslinked portion M1.

After the second crosslinking step S8 is performed, the post-treatment step S6, the second powder supply step S7, and the second crosslinking step S8 are sequentially repeated to bond the plurality of thin pieces together.

That is, after the second crosslinking step S8, as illustrated in <FIG>, the relative positions of the surface of the crosslinked portion M2 in the raw rubber powder layer m2 and the surface of the manufacturing table <NUM> are adjusted to align the surface of the crosslinked portion M2 with the surface of the manufacturing table <NUM>. In other words, in the illustrated example, the relative positions in the Z-axis direction of the surface of the crosslinked portion M2 and the surface 121a of the supply plate <NUM> are adjusted to align the surface of the crosslinked portion M2 with the surface 121a of the supply plate <NUM>.

After the surface of the crosslinked portion M2 and the surface 121a of the supply plate <NUM> are aligned, the raw rubber powder is supplied onto the surface of the raw rubber powder layer m2, which is at the same position in the Z-axis direction as the surface 121a of the supply plate <NUM>, uniformly in a layer of a thickness corresponding to the next thin piece L3. The layer is then irradiated with an electron beam according to a shape corresponding to the next thin piece L3 to crosslink the irradiated portion. The raw rubber powder layer can thus be sufficiently crosslinked, and the crosslinked portions of the adjacent raw rubber powder layers can be bonded together. <FIG> illustrates a state in which raw rubber powder layers m1 to m8 are stacked and aligned after a crosslinked portion M8 is formed by electron beam irradiation of the raw rubber powder layer m8. In this way, by repetition of the post-treatment step S6, the second raw rubber powder supply step S7, and the second crosslinking step S8, a rubber product <NUM> having a plurality of thin pieces L1 to LN bonded together is manufactured.

The method of manufacturing a rubber product including each of the above steps S1 to S8 can flexibly respond to changes in the shape of the product and achieve high manufacturing accuracy.

After the last layer in the Z-axis direction is crosslinked, a step of removing the rubber product <NUM> from the surface 111a of the manufacturing unit <NUM> and removing the uncrosslinked raw rubber powder remaining at the outer and inner periphery of the rubber product <NUM> is preferably included.

The means for removing the uncrosslinked raw rubber powder is not particularly limited, but the powder can, for example, be removed by blowing water or air onto the rubber product <NUM>.

Another example of the rubber product is a rubber product <NUM> having a shape such that a cylindrical hollow 11a is formed inside a cylinder, with a hole 11b penetrating from the hollow 11a to the outer periphery of the cylinder, as illustrated in <FIG>. After crosslinking to yield the shape of the rubber product <NUM> by steps S1 to S8, the uncrosslinked raw rubber powder remaining in the hollow 11a can be discharged from the hole 11b. At this time, after the uncrosslinked raw rubber powder is discharged from the hole 11b, the hole 11b may be plugged with another crosslinked rubber material. In this way, a hollow rubber product can be easily formed.

Another example of the rubber product is a rubber product <NUM> having a shape such that the entire outer periphery is curved, a hollow is formed inside, and a hole 12b penetrates from the hollow to the outer periphery, as illustrated in <FIG>. After crosslinking to yield the shape of the rubber product <NUM> by steps S1 to S8, the uncrosslinked raw rubber powder remaining inside can be discharged from the hole 12b. At this time, after the uncrosslinked raw rubber powder is discharged from the hole 12b, the hole 12b may be plugged with another crosslinked rubber material. In this way, a hollow rubber product can be easily formed.

Claim 1:
A method of manufacturing a rubber product (<NUM>) by bonding a plurality of thin pieces (L1,L2,L3) on a manufacturing table (<NUM>), the method comprising:
an adhesion prevention treatment step (S <NUM>) of treating uncrosslinked rubber powder, which is a material of the rubber product (<NUM>), performed by coating the surface of the uncrosslinked rubber powder with an adhesion prevention agent, to prevent mutual adhesion of the uncrosslinked rubber powder;
a first raw rubber powder supply step (S4) of supplying raw rubber powder, on which the adhesion prevention treatment has been performed, onto a surface of the manufacturing table (<NUM>) uniformly in a layer of a thickness corresponding to a thin piece (L1);
a first crosslinking step (S5) of irradiating a portion of the layer (m1) of raw rubber powder with an electron beam according to a shape corresponding to the thin piece (L1) to crosslink the portion that is irradiated;
a post-treatment step (S6) of adjusting relative positions of a surface of a crosslinked portion (M1) in the layer (m1) of raw rubber powder and a surface of the manufacturing table (<NUM>) to align the surface of the crosslinked portion (M1) with the surface of the manufacturing table (<NUM>);
a second raw rubber powder supply step (S7) of supplying the raw rubber powder onto the surface of the manufacturing table (<NUM>), including the surface of the crosslinked portion (M1), uniformly in a layer of a thickness corresponding to a next thin piece (L2) to be stacked on the thin piece (L1); and
a second crosslinking step (S8) of irradiating a portion of the layer (m2) of raw rubber powder with an electron beam according to a shape corresponding to the next thin piece (L2) to crosslink the portion that is irradiated,
wherein the uncrosslinked rubber powder includes calcium oxide, and
wherein the post-treatment step (S6), the second raw rubber powder supply step (S7), and the second crosslinking step (S8) are sequentially repeated to bond the plurality of thin pieces (L1,L2,L3) together.