JP6882004B2 - Injection molding, injection molding manufacturing method, and gear manufacturing method - Google Patents

Description

The present invention relates to an injection molding mold made of a resin mold, a method for manufacturing the injection molding mold, and a method for manufacturing a gear using the injection molding mold.

When manufacturing industrial products such as parts such as gears by injection molding of a resin material, a metal mold (mold) may be used. In general, in injection molding using a metal mold, the mold is often designed so that the parting line corresponding to the mold division position comes to the end face of the gear in consideration of the mold release of the molded product. In addition, in consideration of the workability of the tooth profile, the mold may be designed so that the parting line comes to the corners of the tooth surface and the side surface.

On the other hand, metal dies, so-called dies, are generally manufactured by using cutting with a machining center, turning with a lathe, grinding with a lathe, and electric discharge machining with a copper electrode / wire electric discharge machine. Although the mold component obtained by this is highly accurate, it takes a long time to complete the mold because it is processed through a plurality of steps and because there are a large number of mold components. For this reason, when a prototype of an experimental part or the like is prototyped by injection molding, a metal mold is created each time, which causes a problem that the trial production time becomes long and the trial production cost increases.

Therefore, conventionally, a method using a resin mold has been proposed (for example, Patent Document 1 below). In the method described in Patent Document 1, a cavity type is obtained by injecting a thermosetting resin around a gear model created by some method.

Japanese Unexamined Patent Publication No. 7-124953

On the other hand, in recent years, it has become possible to directly manufacture parts using 3D printing technology. For example, it is conceivable to use 3D printing technology when making a prototype of the above gear. There are three main methods of 3D printing. The first is powder additive manufacturing, in which a thin layer of resin or metal powder material is laid, the part where the model is to be formed is irradiated with laser light, and melting and solidification are continuously repeated to obtain a three-dimensional model. This method is called the SLS method or the like. The second is to irradiate the surface of the liquid tank filled with a photocurable liquid resin material or the lowermost part where the modeled object is to be formed with ultraviolet rays, and continuously perform photopolymerization to create a dimensional modeled object. It is called the SLA method or the like in the stereolithography method obtained. The third method is an inkjet additive manufacturing method in which a photocurable liquid resin material is discharged and laminated from a nozzle to a portion where a modeled object is to be formed to obtain a three-dimensional modeled object.

However, in 3D printing of parts such as gears directly, there are problems with physical properties such as the types of modeling materials are limited compared to injection molding materials, and the tension, bending, and impact strength are significantly inferior to injection molding materials. In some cases, the molding result may not be worthy of evaluation. Therefore, a method of producing a resin mold by 3D printing, which can be manufactured relatively easily, and performing injection molding using this resin mold has attracted attention.

However, when injection molding is performed using a resin mold, there is a problem that burrs are likely to occur on the parting line if molding is performed with the same specifications as the metal mold. For example, if the gear is injection-molded using a resin mold having a parting line arranged on the tooth surface, the meshing accuracy of the gear may be significantly lowered. In order to deal with this, it is conceivable to perform post-processing to improve the meshing accuracy of the gear after injection molding, but there is a possibility that burrs cannot be sufficiently removed.

Therefore, an object of the present invention is to enable high-precision production of resin gears by injection molding using a resin mold.

In order to solve the above problems, in the present invention, particularly in the configuration of the injection molding mold, the first resin mold and the second resin mold, which are divided into the core mold and the cavity mold, are mounted on the injection molding machine, respectively. wherein the resin-made gear a injection mold for injection molding, said first resin mold is Ri integral member der having a transfer surface for transferring the entire tooth surfaces of the gears, the transfer surface adopting a configuration in which Ru includes an overhang portion for transferring the edge portion continuous with the tooth surface.

According to the above configuration, since the entire tooth surface of the gear can be transferred by the transfer surface of the first resin mold, the resin gear can be manufactured with high accuracy by injection molding using the resin mold.

It is sectional drawing which showed the state which the 1st and 2nd resin molds which adopted this invention were attached to the die set of an injection molding machine. FIG. 5 is a cross-sectional view showing a detailed configuration example of a resin mold configured as a resin piece that can be attached to a die set in the configuration of FIG. 1. It is a perspective view which showed the gear made of resin which was injection-molded by the resin mold of FIG. 1 or FIG. It is a perspective view which showed the main part of the resin gear of FIG. 3 in an enlarged manner. It is explanatory drawing which showed the burr direction and position which may occur in the vicinity of the tooth surface of a gear in the mold division of the resin mold of FIG. 1 or FIG. It is explanatory drawing which showed the burr direction and position which may occur in the vicinity of the tooth surface of a gear in a conventional injection molding die. It is explanatory drawing which showed the state of manufacturing the resin mold which adopted this invention by the laminated molding by a 3D printer. It is explanatory drawing which showed the state after contraction of the gear formed by the resin mold which adopted this invention. A configuration example in which a reinforcing ring for use in reinforcement and mold release is arranged on the outer periphery of the resin mold adopting the present invention is shown. FIG. b) is an exploded perspective view of the resin mold and the reinforcing ring. It is a perspective view which showed the structure of the tooth surface of the resin gear which was injection-molded by the resin mold which adopted this invention, and the end edge part connected with it. It is a perspective view which showed the different structure of the tooth surface of the resin gear which was injection-molded by the resin mold which adopted this invention, and the end edge part connected with it.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. The configuration shown below is merely an example, and for example, a person skilled in the art can appropriately change the detailed configuration without departing from the spirit of the present invention. Further, the numerical values taken up in the present embodiment are reference numerical values and do not limit the present invention.

In the following embodiments, an injection molding die for injection molding a resin gear, particularly a first resin mold (2) divided into a core mold or a cavity mold that can be mounted on an injection molding machine, and a second resin mold, respectively. The configuration of the injection molding mold provided with the resin mold (3) is shown. The first and second resin molds (2, 3) can be, for example, in the form of so-called "pieces" that can be attached to the die set (1) provided in the injection molding machine.

In particular, one of the first and second resin molds, for example, the first resin mold (2), is an integral member having a transfer surface (33) for transferring the entire tooth surface of the gear. .. As a result, the accuracy of the tooth surface of the gear to be injection-molded is not impaired by burrs or the like. Therefore, the resin gear (28) is injection-molded using the first and second resin molds configured as described above, and the resin gear (28) is injection-molded using the resin mold. ) Can be manufactured with high precision.

Further, preferably, the first resin mold (2) includes an end edge portion (34) connected to the tooth surface (32) of the gear to be molded, for example, an overhang portion (14) for transferring a corner portion or the like. The configuration is as follows. As a result, the first resin mold (2) can be transferred so as to wrap the entire tooth surface (32) of the gear (28), and the accuracy of the tooth surface (32) is not impaired by burrs or the like and is made of resin. Gear (28) can be injection molded. Further, the overhang portion (14) of the first resin mold (2) is preferably configured to transfer an inclined chamfer shape to an end edge portion (34) connected to the tooth surface (32) of the gear (28). can do.

The first resin mold (the same applies to (2) or the second resin mold (3)) can be manufactured by laminated molding such as 3D printing. Further, the protrusion amount (protrusion length) of the overhang portion (14) is preferably 0.5 mm or less. By setting the dimensions of the overhang portion in this way, the first resin mold (2) can be manufactured without any trouble by using laminated modeling such as 3D printing. For laminated modeling such as this 3D printing, for example, a method of forming the first or second resin mold (2, 3) by irradiating a modeling layer of a resin material with a laser beam and repeating the laminated modeling. Can be used.

Further, in the injection molding of the resin gear (28) using the first resin mold (2, 3) configured as described above, the property that the material is resin is utilized, and the first resin mold (2, 3) is used. The molded gear (28) can be released by elastically deforming or irreversibly deforming 2). For example, after casting the resin material, the first resin mold (2) is elastically or irreversibly deformed in the mold release direction or in the radial direction from the center of the molded gear (28) toward the outer periphery, and the first resin is formed. Remove the molded gear from the mold. As a result, even when the first resin mold (2) has an undercut shape defined by the overhang portion (14), the injection-molded gear can be easily released.

As described above, when the first resin mold (2) is elastically deformed or irreversibly deformed, it is effective to make the first resin mold (2) into a shape or size that is easily deformed. In addition to this, a reinforcing ring (50) can be arranged around the first resin mold (2) in order to guarantee the rigidity at the time of casting and molding.

Further, in order to facilitate elastic deformation or irreversible deformation of the first resin mold (2), a recess such as a notch (51) can be arranged at an appropriate portion of the first resin mold (2). By elastically deforming or irreversibly deforming the first resin mold (2) through the notch (51), the gear (28) formed from the first resin mold (2) can be released from the mold. Further, an external force may be applied to the portion of the notch (51) to elastically deform or irreversibly deform (break) the first resin mold (2) at this portion to perform mold release.

<Embodiment 1>
FIG. 1 shows an example of a cross-sectional configuration of an injection molding mold for injection molding a resin gear while mounted on a die set of an injection molding machine.

The injection molding mold of the present embodiment includes a first resin mold 2 (for example, a core) and a second resin mold 3 (for example, a cavity type), respectively. The resin mold 2 and the resin mold 3 can be configured as "pieces" having a standard outer shape that can be mounted on the die set 1 (standard die set) of the injection molding machine.

In order to be put into molding in a short period of time, it is advisable to standardize the dimensions and other specifications of the die set 1, especially the mounting part of the piece, according to the size of the part to be molded. If standards such as the dimensions of the die set 1 have been determined, only resin molds 2 and 3 are manufactured according to the specifications, and they can be put into injection molding simply by mounting them on an injection molding machine. In this way, the commutativity of the die set 1, the resin mold 2, and the resin mold 3 can be enhanced, and trial production and manufacturing by injection molding of gears can be performed in a short period of time.

In the configuration of FIG. 1, for example, a center pin 4 for performing mold release is arranged on the side of the resin mold 2. The resin of the material is injected through the resin inflow port 5 arranged on the side of the resin mold 3, the sprue runner 6, and the gate 7 held by the gate bush 8. In FIG. 1, other parts of the injection molding machine, for example, a pressure system for injecting molten resin connected to the resin inflow port 5, a drive system for the die set 1 and the center pin 4, and the like are not shown. As for the members of these injection molding machines, the same configurations as those known can be used.

The resin mold 2 and the resin mold 3 are molded from a resin material so that a cavity 9 for transferring the shape of the gear to be molded is defined between them. The gear transferred by the cavity 9 (28, which will be described later) shows the shape of its cross section by hatching of narrow diagonal lines in FIG. 1, and the reference line of its tooth surface is shown by a dotted chain line according to the custom. Further, in FIG. 1, the center of rotation of the gear (28 described later) or the center of the center pin 4 (or the resin molds 2 and 3) corresponding thereto is shown by the alternate long and short dash line at the center. The cross sections of the center pin 4 and the gate bush 8 are shown by hatching with wide diagonal lines.

At the time of injection molding, as shown in FIG. 1, the first and second resin molds 2 and 3 are mounted on the die set 1 and molded, and the cavity 9 defined between the resin molds 2 and 3 is formed. The molten resin is injected and filled through the resin inflow port 5 to the sprue runner 6 to the gate 7. After that, the resin molds 2 and 3 are opened via the die set 1 at the timing when the resin in the cavity 9 is substantially solidified. The configuration and operation for releasing the gear (28 described later) formed from the resin mold 2 will be described later.

For example, POM (polyoxymethylene) can be used as the resin material for injection molding the gear 28. Alternatively, a resin material of PA (polyamide), PBT (polybutylene terephthalate), PC (polycarbonate), PPS (polyphenylene sulfide), or TPE (thermoplastic elastomer) can be used for molding the resin mold 2. The resin material used for injection molding of the gear 28 is arbitrary, and a person skilled in the art may adopt an appropriate material other than the above.

Resin molds 2 and 3 are made of an epoxy-acrylate-based ultraviolet-curable and thermosetting resin material, for example, according to the manufacturing method described later, and their rigidity and toughness are not so high. Therefore, the filling pressure at the time of injection molding is set to a low pressure as much as possible, whereby damage to the resin molds 2 and 3 can be avoided. Further, the resin molds 2 and 3 made of the above-mentioned materials are not so resistant to heat. Therefore, when the gear 28 is continuously formed, it is preferable to cool the gear 28 for each shot. For example, by spraying air or a highly volatile liquid on the resin molds 2 and 3 for each shot and confirming that the temperature becomes 30 ° C. or lower, the next injection molding is performed to perform the next injection molding on the resin molds 2 and 3. It may improve durability.

Further, the temperature of the resin used for injection molding should be started from the lowest temperature recommended by the material manufacturer, and gradually increased (every 5 ° C.) as necessary according to the filling condition of the resin. The molten resin is filled with the resin until the shape of the part is almost formed, and the holding pressure after that is preferably 30 Mpa or less and the holding time is about 2 s or less in order to prevent mold breakage.

Further, in injection molding using a resin mold as in the present embodiment, unlike normal molding, the molded product is not taken out after the solidification is completed, but the time when the internal pressure drops after the pressure holding process is completed is observed. It is also possible to perform the mold opening operation and take out the resin mold containing the filled resin as it is. Therefore, it is not always necessary to cool the resin molds 2 and 3 or control the temperature thereof.

FIG. 2 shows the cross-sectional structure of the resin molds 2 and 3 of FIG. 1 in more detail. In the present embodiment, as shown in FIG. 2, the first resin mold 2 is configured as an integral member including a transfer surface 33 that transfers the entire tooth surface 32 of the gear 28 to be molded. In particular, as shown in FIG. 2, the transfer surface 33 of the first resin mold 2 transfers the tooth surface of the gear 28 (the tooth surface 32 of FIGS. 3 and 4), and the portion of the tooth surface (32). It has a shape that wraps around the entire circumference.

The shape of the tooth surface 32 transferred by the cavity 9 is arbitrary, but the tooth surface 32 is preferably formed of an involute curved surface or the like in consideration of operating noise and strength.

Further, as shown in FIG. 2, the mold dividing lines of the resin molds 2 and 3 are further above the upper side in the drawing of the gear 28. Further, the transfer surface 33 for transferring the tooth surface 32 of the gear 28 includes an overhang portion 14 for transferring the upper edge portion (corner portion) connected to the tooth surface of the gear 28 to be formed.

In the present embodiment, the resin molds 2 and 3 are divided (molded) as shown in FIG. 2, and the cavity 9 between the resin molds 2 and 3 is formed into the shape shown in the figure. As a result, the entire tooth surface 32 of the gear 28 from the lower side to the upper side in the drawing can be transferred by the transfer surface 33 of the first resin mold 2 which is an integral member.

FIG. 3 shows the configuration of the gear 28 that can be injection-molded by the resin molds 2 and 3 configured as shown in FIGS. 1 and 2. In FIG. 3, the shaft hole at the center of the gear 28 and the structure around the shaft hole are not shown in detail. In FIG. 3, the edge portion 34 of the tooth surface 32 of the gear 28 is the edge portion transferred by the overhang portion 14 of the first resin mold 2 described above. The edge portion 34 can be transferred into various shapes depending on the configuration of the overhang portion 14 of the resin mold 2.

For example, the overhang portion 14 of the first resin mold 2 of FIGS. 1 and 2 has a chamfered shape in which the end edge portion 34 connected to the tooth surface 32 of the gear 28 is inclined as shown in an enlarged manner in FIG. Can be configured as a transfer surface.

5 and 6 show a state in which the resin mold 3 is separated from the resin mold 2 of FIGS. 1 and 2 in order to take out the molded gear 28 after casting. The resin mold 2 of FIG. 5 is configured as an integral member having a transfer surface 33 for transferring the entire tooth surface 32 of the gear 28. That is, the resin mold 2 of FIG. 5 (and the corresponding resin mold 3 (not shown) has the same mold division form of the present embodiment as that shown in FIGS. 1 and 2.

On the other hand, unlike FIG. 5, the resin mold 2 (and the corresponding resin mold 3 not shown) of FIG. 6 substantially coincides with the side surface portion connected to the tooth surface 32 of the gear 28 via the corner portion. As a result, the divided surfaces of the resin mold 2 (and the corresponding resin mold 3 (not shown)) are taken.

Generally, the same applies to the case of a mold, but irregularly formed portions called burrs or the like are formed along the joints of the divided surfaces of the plurality of divided resin molds. In the mold division form as shown in FIG. 6, the division surface of the resin mold 2 (and the corresponding resin mold 3 (not shown) is taken so as to substantially coincide with the side surface portion of the gear 28. Therefore, burrs are generated in the direction shown by arrow 36. If burrs (irregularly formed portions) are generated so as to protrude from the tooth surface 32 in this way, the molding accuracy of the tooth surface 32 may decrease. If the divided surface of the resin mold 2 (and the corresponding resin mold 3 (not shown) is lower than that in FIG. 6 and is close to the center of the tooth surface 32 in the drawing, the position where the burr occurs is the center of the tooth surface 32. Occurs in the part. If burrs (irregularly formed parts) occur, post-processing such as grinding is required. When the tooth surface 32 has burrs as shown in FIG. 6, the post-processing needs to be performed precisely in accordance with the mechanical accuracy required for the gear 28, and the cost and time of the post-processing are required. Increases.

On the other hand, in the configuration shown in FIG. 5, the resin mold 2 is configured as an integral member including a transfer surface 33 that transfers the entire tooth surface 32 of the gear 28. Therefore, the divided surfaces of the resin molds 2 and 3 are on the side surfaces of the gear 28 shown on the upper side in the drawing. In such a mold division form, the direction of the burr generated along the mold division surface is as shown by the arrow 35 in FIG. As described above, in the mold division form as shown in FIGS. 1, 2 and 5, when burrs are generated, they are generated in the direction of growing from the side surface of the gear 28 on the upper side of FIG. 5, and the teeth are generated as shown in FIG. No burrs are formed that have a direction in which they grow from the surface 32. Even if post-processing for removing burrs as shown by arrow 35 in FIG. 5 is required, the processing accuracy is not as high as required for post-processing on the tooth surface 32. Therefore, according to the mold division form as shown in FIGS. 1, 2 and 5, post-processing of the gear 28 for removing irregularly formed portions such as burrs can be performed at low cost and in a short time. ..

Next, with reference to FIG. 7, a suitable method for manufacturing the first resin mold 2 will be described. As shown in FIG. 7, the first resin mold 2 can be manufactured by laminating molding using a 3D printer. In the manufacturing method shown in FIG. 7, the first resin mold 2 is molded by irradiating the molding layer near the liquid surface 13 of the resin material 12 with a laser beam (not shown) and repeating the laminated molding. The method of laminating the resin mold using the 3D printer may be different from that described in FIG. 7 below. Further, although not shown in detail in the present embodiment, of course, the resin mold 3 paired with the first resin mold 2 can also be modeled by the same method.

FIG. 7 shows only the main parts of the 3D printer used for laminated modeling. The resin material 12 for modeling in the molten state is housed in a container (not shown), and the build plate 10 is arranged below the liquid level 13.

The build plate 10 is in the vicinity of the liquid level 13 at the initial stage of modeling, and the modeling layer near the liquid level 13 is irradiated with a laser beam (not shown) from the information in the drawing. Then, each time one layer is cured, the build plate 10 is moved downward as shown by an arrow in FIG. 7 by a driving means (not shown) of the 3D printer. As a result, the resin mold 2 is laminated and molded one layer at a time in order from the lower structure thereof. The direction and orientation of the laminated modeling are arbitrary, but in consideration of drawing accuracy, for example, in the stereolithography modeling posture as shown in FIG. 7, the profile of the gear (28) transferred by the cavity 9 is drawn horizontally. It is good to arrange it so that it is done.

The molding of the lowermost layer of the resin mold 2 may be started from directly above the build plate 10 by laser irradiation, but in the case of FIG. 7, in order to facilitate the separation of the molding resin mold 2 from the build plate 10. First, the support 11 is modeled. In this example, the support 11 is composed of a large number of conical or pyramid-shaped small supports that support the bottom surface portion of the resin mold 2. However, the shape of the support 11 is arbitrary, and any shape may be used for the support 11 as long as the entire bottom surface portion of the resin mold 2 can be prevented from sticking to the build plate 10 side as much as possible.

FIG. 7 shows a state immediately after the resin mold 2 is laminated to the uppermost portion, and a cavity 9 similar to the above is formed on the upper surface of the resin mold 2 in the drawing. In this example, an overhang portion 14 is formed on the uppermost portion of the resin mold 2 facing the cavity 9 in order to realize the mold division form of the resin molds 2 and 3 described above. In FIG. 7, the center of the resin mold 2 (corresponding to the rotation axis of the injection-molded gear (28)) is indicated by a chain line.

In the molding of the resin mold 2 (or 3) by the laminated molding of the present embodiment, for example, an epoxy-acrylate-based UV-curable and thermosetting material can be used as the resin material (12: FIG. 7). , An ultraviolet curing laser is used as the laser beam for modeling. Further, as the resin material used for the stereolithography of the resin mold 2, an epoxy-based or acrylate-based resin can be used. For example, as the acrylate-based oligomer, urethane acrylate-based, epoxy acrylate-based, polyester acrylate-based, acrylic acrylate-based, and the like can be considered.

In the case of laminated modeling such as 3D printing, the amount of protrusion of the overhang portion 14 of the resin mold 2 (FIG. 7) for transferring the end edge portion 34 connected to the upper side surface of the gear 28 in FIGS. 3 and 4. (Overhang amount) is preferably set to a value as small as possible, for example, 0.5 mm or less. In stereolithography by laser irradiation, good modeling is difficult if there is no shape underneath, but if the overhang portion 14 is set to a value as small as 0.5 mm or less, the overhang portion 14 can be modeled relatively well. Can be done. If the overhang portion 14 has a large protrusion amount, a support portion that serves as a base for laminated modeling is required. It is not unthinkable to use such a support for modeling the overhang portion 14. However, in that case, there is a possibility of leaving a trace of the support portion near the tooth surface 32, and there may be a problem that post-processing for removing the trace is required or the support trace cannot be removed. .. On the other hand, if the overhang portion 14 is set to a value as small as 0.5 mm or less, the overhang portion 14 can be molded relatively well without the need for a support portion that serves as a base for laminated molding.

In the following, the cavity 9 between the resin molds 2 and 3 is filled with resin, the resin molds 2 and 3 are opened, and then the gear 28 formed from the state as shown in FIG. 5, for example, is released from the resin mold 2. Here are some techniques for doing so.

As described above, the resin mold 2 is an integral member that is transferred so as to wrap the tooth surface 32 of the gear 28, and the resin mold 2 has an undercut shape defined by the overhang portion 14, and the gear 28 has an undercut shape. It is molded inside it. In order to release the gear 28 from such a state, for example, it is conceivable to utilize the contraction of the gear 28 after molding as shown in FIG. Further, a method of releasing the gear 28 by elastically deforming or irreversibly deforming (destroying) the first resin mold 2 with the configuration shown in FIGS. 9A and 9B may be used. ..

FIG. 8 shows the state of the resin mold 2 after the resin mold 3 is opened as in FIG. 5, and the dimension of the diameter (horizontal direction in the figure) of the gear 28 in the figure shrinks after injection molding. Is getting smaller. In FIG. 8, the gear 28, particularly the tooth portion 17 constituting the circumferential portion thereof, contracts to form a gap 16 between the gear 28 and the transfer surface 33 of the tooth surface of the resin mold 2. If the gap 16 is sufficiently large, the gear 28 formed by passing between the overhang portions 14 to 14 constituting the undercut can be released from the resin mold 2. The mold release utilizing the contraction of the gear 28 has the size of the gap 16 by considering, for example, the size of the cavity 9 of the resin mold 2, the final size of the gear 28, and the selection of the resin material used for molding the gear 28. It is possible by controlling.

On the other hand, under injection molding conditions where the contraction of the gear 28 cannot be used for mold release, for example, the mold release method as shown in FIGS. 9A and 9B can be used. 9 (a) is a cross-sectional view of the gear 28 and the resin mold 2 showing the same state as in FIGS. 5 and 8, and FIG. 9 (b) shows the resin mold 2 and the reinforcing ring used in the configuration of FIG. 9 (a). It is an exploded perspective view of 50.

As described above, the resin mold 2 has a transfer surface 33 having a shape that wraps the entire tooth surface 32 of the gear 28, or further has an overhang portion 14. However, the gear 28 can be released from the gear 28 by elastically deforming or irreversibly deforming (breaking) by utilizing the characteristic that the material of the resin mold 2 is resin.

As shown in FIG. 9B, the resin mold 2 of FIG. 9 is formed into a cylindrical shape having a shape and dimensions that can be mounted in the recess of the die set 1. As shown in the figure, the cavity 9 having the transfer surface 33, the overhang portion 14, and the like is defined on the upper portion of the base portion 2b of the resin mold 2. The periphery of the upper portion of the resin mold 2 having the cavity 9 is configured as a stepped portion 2a notched in a circumferential shape.

As a result, the portion where the cavity 9 of the resin mold 2 is defined is smaller than the diameter of the base portion 2b, and the portion on the outer periphery of the cavity 9 is a thin portion 2c. The gear 28 can be easily released by elastically deforming or irreversibly deforming (destroying) the thin-walled portion 2c by forming the peripheral portion of the resin mold 2 having the cavity 9 as the thin-walled portion 2c. it can. However, even though it is a thin portion 2c, it is necessary to secure the minimum rigidity and toughness at the time of injection molding. For example, in the resin mold 2 laminated and molded from the epoxy-acrylate-based resin material as described above, it is necessary to secure at least about 0.6 mm in the thickness of the portion of the cavity 9 corresponding to the tooth tip of the gear 28.

Further, in the resin mold 2 of FIG. 9B, a reinforcing ring 50 having a corresponding shape can be fitted to the upper stepped portion 2a cut out to form the thin-walled portion 2c. As shown in FIG. 9B, the reinforcing ring 50 is inserted and attached to the stepped portion 2a on the upper portion of the resin mold 2 prior to injection molding. In the configurations shown in FIGS. 9A and 9B, the reinforcing ring 50 is preferably made of a highly rigid metal such as an aluminum alloy, a copper alloy, or steel.

With such a configuration using the reinforcing ring 50, the rigidity and toughness of the resin mold 2 at the time of injection molding can be ensured. Then, when the gear 28 is released from the resin mold 2, the reinforcing ring 50 may be removed, whereby the thin portion 2c of the resin mold 2 can be easily elastically deformed or irreversibly deformed (broken).

Further, FIGS. 9A and 9B show a configuration for easily elastically deforming or irreversibly deforming (breaking) the portion where the cavity 9 of the resin mold 2 is formed. This configuration includes a notch 51 formed at a substantially lowermost end portion of the upper portion of the resin mold 2 surrounded by a stepped portion of the resin mold 2.

As shown in FIG. 9A, the notch 51 (recess) is formed into a groove shape having a substantially V-shaped cross section, for example. The resin mold 2 having the structure shown in FIGS. 9A and 9B can be easily and inexpensively manufactured by optical lamination molding by 3D printing as described in FIG. 7.

If the resin mold 2 is provided with the notch 51 as described above, the reinforcing ring 50 is removed, and an external force is applied to the notch 51 through, for example, an appropriate tool or jig to accommodate the cavity 9 of the resin mold 2. The portion can be easily elastically deformed or irreversibly deformed (broken). For example, the formed gear 28 can be released from the cavity 9 downward in the drawing by breaking the accommodating portion of the cavity 9 of the resin mold 2 from the portion of the notch 51 (FIG. 9A).

The reinforcing ring 50 does not necessarily have to be made of a material such as a metal having high rigidity as described above. The reinforcing ring 50 may be made of resin or the like as long as it can guarantee the strength required for the peripheral portion of the cavity 9 during the resin filling period of injection molding or the like.

In order to elastically deform or irreversibly deform (break) the resin mold 2, a radial external force is applied from the center of the resin mold 2 toward the outside along its radius by using an appropriate tool or jig. The method may be adopted.

As described above, according to the present embodiment, the first resin mold 2 and the second resin mold 3 which are divided into the core mold and the cavity mold, which are mounted on the die set 1 of the injection molding machine, are included. , The resin gear 28 is injection molded. In the present embodiment, the first resin mold 2 adopts a configuration in which the first resin mold 2 is an integral member including a transfer surface 33 that transfers the entire tooth surface 32 of the gear 28. Therefore, the entire tooth surface 32 of the gear 28 can be transferred by the transfer surface 33 of the first resin mold 2, and the resin gear 28 can be manufactured with high accuracy by injection molding using the resin mold. ..

<Embodiment 2>
In the above-described first embodiment, as shown in FIG. 4, the overhang portion 14 of the first resin mold 2 is used to transfer the inclined chamfered shape to the end edge portion 34 connected to the tooth surface 32 of the gear 28. ..

In the configuration of FIG. 4, the inclined chamfered shape of the edge portion 34 connected to the tooth surface 32 of the gear 28 transferred by the overhang portion 14 is a continuous edge portion of the concave and convex tooth surfaces 32 as shown in the drawing. Is shaped like a series of ridges.

The inclined chamfered shape of the edge portion 34 connected to the tooth surface 32 of the gear 28 transferred by the overhang portion 14 does not necessarily have to be the shape shown in FIG. For example, as shown in FIG. 10, the shape of the edge portion 31 is a flat surface or a curved surface in which each of the teeth having a convex portion on the tooth surface 32 is scraped off at an appropriate inclination angle. .. In FIG. 10, the boundary 37 shows a boundary line between the side surface of the gear 28 and the end edge portion 31, and faces the portion of the tooth tip from the boundary 37, which is a convex portion on the tooth surface 32. A sloping chamfer is constructed.

The chamfered shape similar to or similar to that of the edge portions 34 and 31 shown in FIGS. 4 and 10 is the same or similar to the chamfered shape of the edge portions 34 and 31 shown in FIGS. The resin mold 2 can be configured to be transferred by the transfer surface.

When injection molding is performed with a resin mold (2, 3) as in the first and second embodiments, the filling pressure of the molten resin is lower than that of the injection molding with a mold, and the gear of the molded product. 28 may be highly brittle. Therefore, for example, in injection molding of a gear in which the number of modules exceeds 0.8, the end edge portion connected to the tooth surface 32 of the gear 28 is inclined as shown in the edge portions 34 and 31 shown in FIGS. 4 and 10. By forming the chamfered shape, it may be possible to prevent the resin teeth from being chipped. Further, the chamfered shape inclined to the edge portion connected to the tooth surface 32 of the gear 28 may reduce the noise during the operation of the gear 28.

<Embodiment 3>
In the above embodiments 1 and 2, an example in which the overhanging portion 14 of the resin mold 2 transfers an inclined chamfered shape to the edge portions 34, 31 of the tooth surface 32 of the gear 28 as shown in FIGS. 4 and 10. Indicated. However, the portion of the resin mold 2 transferred by the overhang portion 14 does not necessarily have to have the above-mentioned shape.

For example, as shown in FIG. 11, the overhang portion 14 of the resin mold 2 may transfer the end edge portion 30 of the tooth surface 32 of the gear 28 so as to be flush with the side surface 38 of the gear 28. Absent. In this configuration, the side portion of the tooth of the gear 28 is not chamfered, but the gear 28 can be manufactured without any problem in practical use depending on the specifications of the number of modules of the gear 28 even by injection molding using a resin mold.

Although FIG. 11 does not show a portion like the boundary 37 in FIG. 10, the side surface 38 of the gear 28 has a portion of FIG. 10 depending on the configuration of the overhang portion 14 and the combination of the mold shape with the resin mold 3. A boundary line such as the boundary 37 of the above may remain. Alternatively, a specification may be adopted in which the boundary line such as the boundary 37 is removed by post-processing such as grinding.

1 ... die set, 2 ... resin type (core type), 3 ... resin type (cavity type), 4 ... center pin, 5 ... resin inflow port, 6 ... sprue runner, 7 ... gate, 8 ... gate bush, 9 ... Cavity, 10 ... build plate, 11 ... support, 12 ... resin material, 13 ... liquid level, 14 ... overhang part, 28 ... gear, 31 ... edge part, 32 ... tooth surface, 33 ... transfer surface, 34 ... end Edge, 50 ... Reinforcing ring, 51 ... Notch.

Claims (10)

An injection molding mold that is mounted on an injection molding machine and includes a first resin mold and a second resin mold, which are divided into a core mold and a cavity mold, respectively, and injection-molds a resin gear.
Injection of the first resin type of Ru with an overhang portion for transferring the edge portion Ri integral member der having a transfer surface for transferring the whole of the tooth surface of the gear, in which the transfer surface is connected to the tooth surface Molding mold. The injection molding die according to claim 1 , wherein the overhanging portion transfers the edge portion to a chamfered shape. The injection molding die according to claim 1 or 2 , wherein the protrusion amount of the overhang portion is 0.5 mm or less. In the injection molding mold according to any one of claims 1 to 3, the first resin mold is a core mold and the second resin mold is a cavity mold. A injection mold manufacturing method according to claim 1, any one of 4, the first resin mold or the second resin mold, an injection mold for molding the layered manufacturing of the resin material Production method. In the injection molding mold manufacturing method according to claim 5, the injection molding mold for molding the first or second resin mold is manufactured by irradiating the molding layer of the resin material with a laser beam and repeating the laminated molding. Method. A method for manufacturing a gear in which a resin gear is injection-molded using the first and second resin molds according to any one of claims 1 to 4. In the method for manufacturing a gear according to claim 7, after casting a resin material, the first resin mold is elastically deformed or irreversibly deformed in a mold release direction or a radial direction from the center of the molded gear toward the outer periphery. A method for manufacturing a gear that releases a gear molded from the first resin mold. A method for manufacturing gears by injection molding resin gears.
The injection molding machine including the first resin mold and the second resin mold, which are divided into the core mold and the cavity mold, respectively, is mounted on the injection molding machine.
Casting the resin material into the injection molding mold and
After the casting, the molded gear is separated from the first resin mold by elastically deforming or irreversibly deforming the first resin mold in the mold release direction or the radial direction from the center of the molded gear toward the outer periphery. Including typing
The first resin mold is an integral member having a transfer surface for transferring the entire tooth surface of the gear.
Wherein prior to casting, the first place the reinforcement ring around the resin mold, and before the release after the casting, the manufacturing method of the gear divided the reinforcing ring. In the method for manufacturing a gear according to claim 9, the first resin mold is provided with a notch in a portion around which the reinforcing ring is arranged, and after removing the reinforcing ring, an external force is applied to the notch. A method for manufacturing a gear in which the first resin mold is elastically or irreversibly deformed and the gear molded from the first resin mold is released.

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