JPH04329802A - Molding method for thim walled parts - Google Patents

Abstract

PURPOSE:To produce the thin walled molding with good accuracy by executing integral double molding using the molding of a resin material which is gasified and splashed in debinder treating and sintering stages as a reinforcing member. CONSTITUTION:Only the molten binder resin is supplied to a supply port 12 to obtain the molding 24. A thin cavity 17 is constituted if a die 6 is exchanged with 16. A binder resin contg. metallic powder (a resin material having the thermal deformation temp. lower than the thermal deformation temp. of the 1st molding) is injected from a supply port 13 to obtain the integral molding 26. The degreasing (debinder treating) and sintering stage are executed in the ensuing stage, by which the 1st molding 24 is gasified and splashed and the binder resin of the molding part of the 2nd stage is gasified and splashed as well and, therefore, the thin product of the metal of the 2nd molding is obtd.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for powder injection molding of thin-walled parts.

0002

BACKGROUND OF THE INVENTION In recent years, a molding method has been developed in which thin-walled parts are obtained by injection molding using a molding die using pellets made of powder and resin material. As a document related to this molding method, there is JP-A-59-145104. In the technology described in this publication, a core that has an outer peripheral shape similar to the inner peripheral surface of a cylindrical core and has dimensions that take into account the shrinkage rate during sintering is first installed in an injection molding machine. A mixture of molten ceramic powder and a resin material (binder resin) is injection molded into the injection molding space formed by the outer mold and the core, and the resulting molded material is inserted into the outer mold. This is a manufacturing (molding) method in which a predetermined rotary transformer core is obtained by debinding the body, decomposing and disappearing the core by heating, and then sintering the molded body.

[0003] In the molding method described in the above publication, the material obtained by kneading the powder and the binder has the desired strength only after being degreased (binder removal treatment) and sintered after molding. At this stage, there is a possibility that plastic deformation is extremely likely to occur. In other words, in the conventional technique, when a ring-shaped thin part 30 with a thickness of 0.3 m/m is molded as shown in FIG. Conventionally, as a countermeasure to this problem, a core is used to take out the molded product, since mold resistance occurs and causes large deformation. However, when using this core, the above-mentioned problem (deformation) is solved, but the problem is that the core must be inserted into the mold and installed, and the core must be manufactured separately. There was a problem of high costs.

0004

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to eliminate the use of a core in the molding of thin-walled parts where cracks, cracks, etc. naturally occur in ordinary powder molding methods. The object of the present invention is to provide a highly productive method for molding thin-walled parts into a desired shape and precision.

[0005]

[Means for Solving the Problems] The present invention provides a method for molding thin-walled parts by powder injection molding, in which a first molded product is injection molded with a resin material made only of resin in a pair of molds, and Either one of the pair of molds is replaced, and a second molded product is created using a mixed material made of a resin containing inorganic powder in a cavity composed of the replaced mold and the first molded product. The first and second molded products are injection molded, and after the first and second molded products are released from the mold, the integrally molded product is degreased and subjected to a sintering process to obtain a thin metal part.

[0006]

[Operation] According to the above molding method, a first molded product obtained by injection molding a resin material made only of resin in a pair of molds in a first step, and one of the pair of molds described above. A second mold is obtained by replacing the mold, forming a cavity with the replaced mold and the first molded product, and injecting a resin containing metal into the cavity to obtain an integral molded product. After the molded product formed in this second step is released from the mold, it is subjected to a degreasing and sintering step, thereby obtaining a highly accurate thin-walled part that does not suffer from deformation, cracks, cracks, etc.

[0007]

[Embodiment 1] An embodiment of the method for molding thin-walled parts of the present invention will be explained based on FIGS. 1 to 4. FIG. 1 is a sectional view showing essential parts for explaining a molding method using a mold according to the present invention. FIG. 2 is a cross-sectional view showing a main part of a molding method using a mold, which is a step following FIG. 1. FIG. 3 is a perspective view showing a molded product formed by the mold shown in FIGS. 1 and 2. FIG. FIG. 4 is a perspective view showing a thin-walled molded part that has undergone a post-mould-release treatment process.

As shown in the figure, at the center position of the lower end surface of the fixed upper mold 2 of the pair of molding molds 1, there is a circular recess formed corresponding to the outer diameter and height dimensions of the molded product to be molded. 5 is drilled. Further, at the center position of the upper end surface of the movable lower mold 3 joined to the lower end surface of the fixed upper mold 2, there is a recess 5 of the fixed upper mold 2.
A cylindrical protrusion 6 is formed to have a height corresponding to that of the cylindrical protrusion 6, and has a space (cavity) 4 having the thickness of the molded product between its inner circumferential surfaces. Furthermore, near the outer periphery of the recess 5 on the lower end surface of the fixed upper die 2, a protrusion 7 having a wedge-shaped cross section is formed on the surface. A protrusion 7 is located near the periphery of the protrusion 6 on the upper end surface of the movable lower die 3 that is joined to the protrusion 7, that is, at a position corresponding to the protrusion 7 of the fixed upper die 2.
A groove 8 having a shape corresponding to the shape of the groove 8 is formed, and the grooves 8 are configured to be detachable so as to fit more precisely into each other's tapered surfaces.

Further, on the upper surface of the fixed upper mold 2, there are supply ports 12 and 1, which communicate with the inside of the cavity 4 at a desired interval and have through holes 10 and 11, respectively, for injecting resin.
3 is provided. Furthermore, screw cylinders 14 and 15 are respectively disposed at the supply ports 12 and 13, as shown in the figure, to inject a predetermined resin into the cavity 4.

Further, as shown in FIG. 2, the fixed upper mold 2 is equipped with a movable lower mold 9 having substantially the same shape as the movable lower mold 3, in order to replace it with the movable lower mold 3 shown in FIG. is now installed. That is, the outer diameter of the mold protrusion 16 formed at the center position of the upper end surface of the movable lower mold 9 is smaller than the protrusion 6 of the movable lower mold 3 shown in FIG. is now configured. Furthermore, holes 20 and 21 are bored in the movable lower mold 9 to allow ejector pins 18 and 19 that operate when the molded product in the cavity is released from the mold to pass therethrough.
9 are inserted through each of them. Further, near the periphery of the protrusion 16 of the movable lower mold 9, there is a groove 22 that fits into the protrusion 7, which has a wedge-shaped cross section and is provided on the fixed upper mold 2, similar to the movable lower mold 3.
is formed so that the movable lower mold 9 precisely matches the fixed upper mold 2. Note that the through hole 11 connected to the supply port 13 for supplying the resin material of the fixed upper mold 2 is connected to the cavity 17.
is placed on top.

Next, the molding method according to this embodiment will be explained using the mold having the above configuration. First, in the configuration shown in FIG. 1, only molten binder resin (resin material consisting only of resin) is supplied to the supply port 12 and injected into the cavity 4 through the through hole 10 by the screw cylinder 14. The inside of the cavity 4 is filled with binder resin. Then, when the movable lower mold 3 is operated, the movable lower mold 3 is separated from the fixed upper mold 2, and the inner diameter of the molded product (first molded product) 25 and the outer diameter of the protrusion 6 of the movable lower mold 3 are separated from each other. do.

Following the above molding, the upper end surface of a separately provided movable lower mold 9 is placed on the lower end surface of the fixed upper mold 2 separated from the movable lower mold 3 at the same position after the movable lower mold 3 is separated. Fit and install. That is, as shown in FIG. 2, the groove 22 formed on the upper end surface of the movable lower mold 9 and the protrusion 7 formed on the lower end surface of the fixed upper mold 2 are fitted and attached to each other. The projection 16 of the circular molded part at the center of the end face is inserted into the inner diameter of the previously molded product 25 and fitted.

In the above configuration, a binder resin containing metal powder (a resin material having a lower thermal deformation temperature than the resin material of the first molded product) is passed through the supply port 13 and the through hole 11 by the screw cylinder cider 15. Then, when injected into the cavity 17 formed between the inner diameter of the molded product 25 previously molded and the outer diameter of the protrusion 16 of the movable lower mold 9, the binder resin is filled into the cavity 17, and the mixed material is molded. The product (second molded product) 24 is molded, and the previous molded product 25
A molded article 24 is obtained which is integrally molded with.

[0014] The binder resin filled in the above step is selected to have a lower thermal deformation temperature than the binder resin filled in the previous step, so the molded parts injected in the previous step will not be thermally deformed. . By moving the movable lower mold 9 downward, the molded product 24 integrally molded in this way is separated from the outer diameter of the molded part 24 and the inner diameter of the circular recess of the fixed upper mold 2, and It descends together with the movable lower mold 9. The released molded product 25 is released from the protrusion 16 of the movable lower mold 9 by the operation of the ejector pins 18 and 19, and the molded product 25 is released from the mold as shown in FIG.
The molded product 26 is taken out as shown in FIG. That is, the ring-shaped molded product 24 previously molded in the first step
A molded product 26 is obtained by integrally molding the thin-walled molded product 25 (FIG. 4) formed in the second step within the inner diameter of the molded product.

The molded article 26 formed by the above steps is as follows:
By performing the degreasing (binder removal treatment) and sintering processes in the next process, the first molded product made of the binder resin molded previously is gasified and scattered, and the molded product is not molded in the second process described above. Since the binder resin of the second molded product is also gasified and scattered, only the metal of the second molded product remains, and a thin circular molded part 27 is obtained as shown in FIG. Although this embodiment has been described using metal powder, other inorganic powders such as ceramic powder or a mixed powder of metal powder and ceramic powder may also be used.

[0016]

[Effects of the Invention] According to the present invention using the above-mentioned molding method, a molded product made of only a resin material injection-molded by a pair of molds, and a mold in which this molded product and either one of the molds described above are replaced. The molded product is injection-molded with metal-containing resin in a newly constructed cavity and then released from the mold. This eliminates the need for a separately manufactured core and eliminates cracks and cracks during mold release. It is possible to mass-produce thin-walled parts of a desired shape with extremely high precision, quality, and at low cost without causing problems such as the following.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the main parts of a mold related to the molding method of the present invention.

FIG. 2 is a cross-sectional view showing the main parts of the mold in a step subsequent to FIG. 1;

FIG. 3 is a perspective view showing a molded product formed by the mold shown in FIGS. 1 and 2. FIG.

4 is a perspective view showing a thin molded part obtained by molding the molded product shown in FIG. 3 through processing steps such as degreasing.

FIG. 5 is a perspective view showing a thin-walled part formed by conventional molding.

[Explanation of symbols]

1 Molding mold 2 Fixed upper mold 3,9 Movable lower mold 4, 23 Cavity 5, 17 Recess 6, 7, 16 protrusions 8, 22 groove 10,11 Through hole 12,13 Supply port 14,15 Screw cylinder 18, 19 Ejector pin 20, 21 holes 24, 25, 26 Molded products 27,30 Thin-walled molded parts

Claims (1)

[Claims] 1. A method for molding thin-walled parts by powder injection molding, wherein a first molded product is injection molded from a resin material made only of resin using a pair of molds, and one of the pair of molds is , and replace the replaced mold with the first mold.
A second molded product is injection molded using a mixed material made of a resin containing inorganic powder in a cavity composed of a molded product and a molded product formed by integrally molding the first and second molded products. A method for forming a thin-walled part, which is characterized in that after releasing from the mold, the integrally molded product is subjected to a degreasing and sintering process to obtain a thin-walled part made of metal.