JPH03290214A - Powder injection molding method and its device - Google Patents

Abstract

PURPOSE:To prevent a green body from getting damaged and obtain high molding accuracy by releasing the green body together with fixed and movable insert dies out of a mold after injection molding, removing a binder, burning and then releasing a molded product from the fixed and movable dies. CONSTITUTION:Injection molding in a mold 1 for injection molding is carried out, and then mold opening is performed by moving a movable mold 3 on a surface 4, and a fixed insert die 11 is separated from a fitting section 12 of a fixed plate 6, integrated with a movable insert die 26 and moved together with the movable mold 3. Knockout rods 32 and 34 are moved upward by actuating a knockout plate 24 to knock out the movable insert die 26 and a runner 33. A green body 18 molded in a cavity 35 is released out of a fitting section 27 of a movable plate 23 together with fixed and movable insert dies 11 and 26 while gate cutting of the green body 18 is carried out, and removing a binder and burning are performed under the given condition in a degreasing and burning oven and a molded product 17 is molded. The fixed insert die 11 and the movable insert die 26 are opened and released to complete the powder injection molding of the molded product 17.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for molding powder, in particular, a method for molding powder, in particular, adding a binder to powder such as cera short ivy powder or metal powder to impart fluidity, and molding the molded product by injection molding. The present invention relates to a powder injection molding method and apparatus for obtaining a sintered part using the powder as a raw material by performing binder removal treatment, firing treatment, etc. after obtaining the powder.

[Conventional technology]

Conventionally, as a molding method to produce sintered crystals using powders such as ceramic powder and metal powders as raw materials, an organic binder is added to the powder to give fluidity and shape retention to make it into an injection molding material, such as screw extrusion. In flow molding using injection molding, a molded product (referred to as a green body or green part) is molded in a mold in the same way as synthetic resin, and after the molded product is taken out from the mold, the binder acid content is removed. A sintered part having a desired shape was obtained through a debinding process (degreasing process) to remove the binder and a firing process (sintering process) to harden the material.

Further, in some cases, the sintered parts have been subjected to post-processing, surface treatment, etc.

[Problem to be solved by the invention]

However, in the prior art, when the green body (injection molded product) molded in the injection mold is taken out from the mold, the bonding force of the powder in the green body is weak.
The green body is a thin-walled part (for example, the thickness is 1 [Il[1
(below), cracking or deformation (collapse of shape) may occur.

In addition, even if the green body does not crack or deform when taken out from the mold, deformation will occur when the green body is heated to remove the binder, so the green body should not be embedded in ceramic powder, etc. It was necessary to process the situation.

When embedded in ceramic powder or the like, it was necessary to remove the ceramic powder adhering to the surface of the sintered part.

Due to the above, the yield for obtaining sintered parts of desired shapes was extremely poor.

The present invention has been made in view of the above-mentioned problems, and the present invention is a powder injection method for sintered parts made from powder with an extremely good yield, which does not cause cracks or deformation in the green body and does not deform during binder removal processing. The purpose is to provide molding methods and equipment.

[Means and effects for solving the problems] The powder injection molding method of the present invention injects an injection molding material into an injection mold to injection mold a green body, and also injects the green body after the injection molding. The molded product is removed from the mold together with the fixed and movable inserts, and after binder removal and firing processing, the molded product is released from the fixed and movable inserts to be molded.

Moreover, the powder indexing molding apparatus of the present invention is provided with an exhaust hole in the fixed and/or movable insert forming the cavity, and the fixed and movable plate that holds the fixed and movable insert is fitted into the exhaust hole. It is constructed by protruding fitting pins.

Therefore, the present invention uses the above means to prevent deformation, cracking, and other damage during the post-processing of the green body after injection molding and during mold release, and achieves high molding accuracy that reverses the desired mold accuracy. In addition, the degassing effect generated during the binder removal and sintering processes in the post-process can be achieved by the exhaust holes provided in the fixed and movable inserts.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) Figures 1 to 3 show the first embodiment of the present invention, in which Figure 1 is a sectional view of an injection mold, and Figures 2 and 3 are green after injection molding. It is an explanatory view showing the post-process of the body.

The injection mold 1 shown in FIG. 1 is constructed by disposing a movable mold 3 on a PL (parting line) surface 4 with respect to a fixed mold 2 so as to be openable and closable.

The fixed mold 2 has a fixed plate 6 fixed to the fixed side mounting plate 5, and a sprue bush 8 having a sprue 7 is mounted thereon through the mounting plate 5 and the fixed plate 6, and is connected to the sprue bush 8 and fixed. It is constructed by attaching a locate ring 9 to a side mounting plate 5.

The fixing plate 6 also has a fitting portion 12 of a fixing insert 11 having a molded head 10 corresponding to the external shape of a desired green body.
Fitting pins 15 and 1 are provided and fit into exhaust holes 13 and 14 passing through the molded head lO of the fixed insert 11.
6 is provided protrudingly.

On the other hand, the movable mold 3 is constructed by fixing a movable plate 23 to a movable mounting plate 20 via a spacer block 21 and a receiver Fi 22, and mounting a protruding plate 24 that can move vertically between the spacer blocks 21. There is.

Further, the movable plate 23 is provided with a fitting part 27 for a movable insert 26 having a molded head 25 corresponding to the molded head 10 of the fixed insert 11, and an exhaust gas passing through the molded head 25 of the movable insert 26. Fitting pins 30 and 31 that fit into the holes 28 and 29 are provided in a protruding manner.

Furthermore, a protruding rod 32 for protruding the fixed and movable inserts 11 and 26 and a protruding rod 34 of a runner 33 are attached to the protruding plate 24.

Further, the fixed and movable inserts 11 and 26 that fit into the fixed plate 6 and the movable plate 23 have cavities 35 formed by the oval-shaped surfaces 10 and 25 of the fixed and movable inserts 11 and 26, respectively. The communicating gate 36,
It is provided between the runners 33 (see FIGS. 2 and 3 for details).

The fixed and movable inserts 11 and 26 are both removably fitted into the fitting portions 12 and 27 of the fixed plate 6 and the movable plate 23, and have a structure such as a bolt for fixing them. isn't it.

Therefore, when opening the fixed mold 2 and the movable mold 3, the fixed insert ll is opened while being integrated with the movable insert 26, and the exhaust holes 28 and 2 of the movable insert 26 are opened.
9 is fitted with the fitting pins 30 and 31 of the movable plate 23 when it is set to be fitted into the fitting part 27, and the fixed insert 1 is fitted into the fitting pin 9.
When the fixed insert 11 is fitted into the fitting part 12 of the fixed plate 6 during mold clamping, the fitting pins 15 and 16 are fitted into the exhaust holes 13 and 14 of No. 1 during injection molding. It is constructed so that it can maintain airtightness.

Injection mold 1 used in the powder cutting bottom shape method of the present invention
Based on the above configuration, the following describes a method for molding a molded product 17 consisting of a bottomed thin-walled part as shown in FIG. 3 from powder using the injection molding die 1 having the above configuration. Let's talk about.

First, in order to give fluidity and shape retention to the raw material powder (iron-Nisokel alloy) as a molding raw material, for example, an organic binder (acrylic resin) is mixed in at a volume ratio of 50% and a small amount of wax is mixed and kneaded. Granulate it and make a compound for injection molding.

Then, the compound is passed through a nozzle of an injection molding machine (not shown) as a powder melt to the sprue 7, runner 33, gate 36, etc. shown in the first figure. The material is filled into the cavity 35 through the molding die 1, and the molding die 1 is cooled by applying a holding pressure.

After completion of injection molding in the injection mold 1, P
The movable mold 3 is moved on the L surface 4 to open the mold.

At this time, the fixed insert 11 is separated from the fitting portion 12 of the fixed plate 6 and is moved together with the movable mold 3 integrally with the movable insert 26 .

In connection with the mold opening process, the protruding plate 24 is operated and the protruding rods 32 and 34 move upward, thereby protruding the movable insert 26 from the fitting portion 27 of the movable plate 23 and protruding the runner 33. I do.

After that, as shown in FIG.
The green body 18 formed in the cavities 35 of Nos. 1 and 26 is removed from the fitting portion 27 of the movable plate 23 together with the fixed and movable inserts 11 and 26 while gate-cutting the green body 18. Degreasing and firing furnace (not shown) integrated with fixed and movable inserts 11 and 26
Inside, a binder removal process and a firing process are performed under predetermined conditions (predetermined processing temperature, time, etc.) to form a molded article 17 from the sintered body.

Furthermore, after the above process is completed, as shown in FIG. 3, the molded product 17 is released from the mold while opening the fixed insert 11 and the movable insert 26, thereby forming the molded product 17 as a thin-walled molded part with a bottom.
Powder injection molding can be completed.

Further, after this, the fixed insert 11 and the movable insert 26 are combined and set in the fitting part 27 of the movable plate 23, and the above-mentioned steps are repeated to continuously mold the molded product 17. It can be carried out in

In particular, in the process of removing the binder and firing the green body 18 integrated with the fixed and movable inserts 11 and 26 after the injection molding of the green body 18, as shown in the second figure, the fixed and movable inserts 11 and 26 are The gas generated during the same process can be exhausted through the exhaust holes 13, 14, 28 and 29 penetrating through the molded product 1 during the same process.
7 can be appropriately prevented from deforming.

According to the above-described molding method, the green body 18 injection molded into the fixed and movable inserts 11 and 26 is
By performing degreasing and firing treatment together with Doujinshi 11 and 26, it prevents damage such as deformation and cracking during ejection, and allows the molding surface to be accurately reversed, allowing for high-precision powder injection molding. can manufacture products.

(Second Embodiment) FIGS. 4 and 5 show a second embodiment of the present invention.
The figure is a front view showing a main part of the injection mold in cross section, and FIG. 5 is a partially enlarged view of the main part.

The injection mold 1 in this embodiment has the fitting parts 12 and 27 of the fixed plate 6 and the movable plate 23, and the fixed and movable parts fitted therein, in the structure of the injection mold 1 of the first embodiment. The configuration of the inserts 11 and 26 in the fitted state is a tapered fit, and the fixing insert 11 is elastically fitted to the fitting portion 12 of the fixing plate 6 via an elastic member. It makes a difference.

That is, as shown in FIGS. 4 and 5, tapers 11a and 12a are formed in the shapes of the outer and inner diameters corresponding to the fitting portions 12 and 27 of the fixed and movable inserts 11 and 26 and the fixed plate 6 and movable plate 23. .

26a and 27a (in the drawings, the fixed insert 11 and the movable insert 26 have a conical outer circumferential shape, and the fitting portions 12 and 27 have a concave inner circumferential shape. ), and the fixing plate 6 is provided with mounting holes 37 and 38 for the springs 39 and 40, and the spring 3 is provided in the mounting holes 37 and 38.
9 and 40, and the fixed insert 11 is installed in the fitting hole 12.
The springs 39 and 40 are configured to fit together against the elastic force of the springs 39 and 40.

The other configurations are the same as those of the first embodiment, and the same components in the configurations in FIGS. 4 and 5 are designated by the same numbers and their explanations are omitted. Specific illustrations of the constituent parts of the first embodiment are omitted.

Now, the powder injection molding method of the molded product 17 using the injection molding die 1 having the configuration of this embodiment is carried out by the same method as in the first embodiment, and in particular, the injection molding die 1 of this embodiment is used. According to the configuration of the mold 1, the fixed and movable inserts 11 and 26 are fitted into the fitting portions 12 and 27 by tapers 11a, 12a, 26a,
27a, and the detachment operation can also be performed via the same tapers 11a, 12a, 26a, and 27a. Therefore, in the molding process of the molded product 17, especially the injection molding of the green body 18 and the degreasing thereof. It is possible to simplify and speed up the operation of attaching and detaching the fixed and movable inserts 11 and 26 to the fitting portions 12 and 27 during the firing process, and furthermore, the positioning accuracy of the fixed and movable inserts 11 and 26 is improved. can be improved.

Further, a spring 39 is provided between the fixed insert 11 and the fitting part 12.
and 40, the fixed insert 11 is moved to the movable insert 26 during the mold opening process after injection molding of the green body 18.
The fixed plate 6 is separated from the inside of the fitting part 12 while being pressed by the elasticity of the springs 39 and 40, and the mold opening is completed while the fixed insert 11 remains integrated with the movable insert 26. It has the effect of ensuring that

Furthermore, a step is provided between the PL surface 4 of the mold 1 and the joint surface 41 of the fixed and movable inserts 11 and 26, and the outer diameter shape of the lower end outer periphery of the fixed insert 11 is shown enlarged in FIG. As described above, by configuring the outer diameter of the fitting portion 27 of the movable plate 23 by providing a taper 11b corresponding to the inner diameter taper 27a, the precision of the two molds is improved.

Regarding other effects, it is possible to obtain the same effects as in the first embodiment.

(Third Embodiment) FIGS. 6 and 7 show a third embodiment of the present invention.
The figure is a longitudinal sectional view of the main part of the injection mold, and FIGS. 7a and 7b are a perspective view and a longitudinal sectional view of the molded product.

This example is an example in which a molded article 42 shown in FIGS. 7a and 7b is molded by applying the powder injection molding method of the present invention.

Thus, the molded product 42 shown in FIGS. 7a and 7b has four pivot pieces 45 having pivot holes 44 projecting from both opening edges of a cylindrical body 43 at mutually orthogonal positions, and also has four pivot pieces 45 projecting from the inside. It is a molded product 42 with a very thin internal pressure and a complicated shape, which has two protrusions 47 having through holes 46 at mutually opposing positions on the circumferential side.

Furthermore, the configuration of the injection mold 1 for the molded product 42 is as follows:
As shown in FIG. 6, a movable mold 3 is disposed facing the fixed mold 2 from the PL surface 4 so as to be able to clamp and open the mold freely. There is.

A nest 48 is mounted inside the movable plate 23 and can be protruded using an ejecting pin 32. The input 48 is
A movable side insert 51 whose lower end is fitted into the fitting portion 50 of the insert seat 49, a slide mold 52 that advances and retreats from four directions with respect to the movable side insert 51, and a slide mold 52 so as to sandwich each slide mold 52. The fixed side insert 53 is placed on the movable plate 23. In addition, the cavity 35 formed by the movable insert 51, each slide mold 52, and the fixed insert 53 includes a sprue 7, a runner 33, and a gate 36 (indicated by dotted lines in the figure) formed inward of the cavity 35. The injection molding material is injected through the tube (shown in ). Further, angiela pins 54 (out of four pins, two are shown in the figure) obliquely attached to the stationary side insert 53 are engaged with guide holes 55 of each slide mold 52, and The molded product 42 is formed by protruding two molding pins 56 that serve as molding portions of the through holes 46 of the protrusions 47 that protrude inside the molded product 42 .

Further, an exhaust hole 57 is formed in the crucible seat 49, and a fitting pin 58 that fits into the exhaust hole 57 is attached to the movable plate 2.
3, and when the insert 48 is set on the movable plate 23, the fitting pin 58 of the movable plate 23 is fitted into the exhaust hole 57, and the exhaust hole 57 is hermetically closed. When the child 48 is taken out from the movable plate 23, degassing during degreasing and firing of the green body 18 is carried out through the exhaust hole 5.
7.

The rest of the structure is the same as that of the first embodiment, and the same components in the figures are given the same numbers and explanations will be omitted, and explanations of the parts not shown will also be omitted.

Now, when molding a molded product 42 using the injection molding die 1 having the above-described configuration, raw material powder is passed from an injection molding machine (not shown) into the cavity 35 through a sprue, a runner, and a gate while the mold is closed. Green body 59 injected inside
After molding, by opening the mold 1,
When the protrusion plate 24 is operated, the insert 49 is protruded from the fitting portion 50 by the protrusion rod 32.

Then, the green body 59 after injection molding is inserted into the insert 49.
Degreasing and firing are performed while the fixed side insert 53 is separated from the movable side insert 51, and after separating each slide mold 52, the molded product is removed from the movable side insert 51. By releasing the mold 42, the molded product 42 shown in FIG.
can be manufactured.

Therefore, in this embodiment, a trowel is used which is particularly suitable for accurately molding the thin-walled molded product 42 having the pivot piece 45 and the protrusion 47, and which provides the same effects as those of the aforementioned embodiments. can.

Although the molded product 42 of this embodiment is illustrated as a thin-walled, complex-shaped part for medical use, it can also be used for other complex-shaped parts, such as complex-shaped, high-precision parts for information equipment. It is also suitable for molding; however, if the shape is complex, it may be difficult to release the gas generated during the degreasing and firing processes, and the countermeasures for such cases are as described above. In each embodiment, it is more effective to use a material with air permeability such as ceramics as the molding material, and to conduct the molding in a state where degassing is improved.

(Effects of the Invention) According to the present invention, since degreasing and firing are performed within the mold insert,
It can effectively prevent damage such as cracking and deformation when the green body is ejected, and it can also prevent deformation that occurs during degreasing and firing processes, and can produce high-precision molded products that accurately reverse the mold precision. It can be molded.

[Brief explanation of drawings]

1 to 3 show a first embodiment of the present invention, FIG. 1 is a sectional view of an injection mold, and FIGS. 2 and 3 show the post-process of a green body after injection molding. Explanatory drawings, FIGS. 4 and 5 show a second embodiment of the present invention, FIG. 4 is a front view showing a main part of an injection mold in cross section, and FIG. 5 is a partially enlarged view of the main part. , FIG. 6 and FIG. 7 show a third embodiment of the present invention, FIG. 6 is a vertical cross-sectional view of the main part of an injection mold, and FIG. 7 a and b are a perspective view and a vertical cross-section of the molded product. It is a front view. 1... Injection mold 2... Fixed mold 3... Movable mold 4... PL surface 5... Fixed side mounting plate 6... Fixed plate 7... Sprue 8... Sprue bush 9... Locate ring 10.25... Molding surface 11... Fixed insert 12.27... Fitting part 13.14.28.29... Exhaust hole 15.16, 30.31 ... Fitting pin 17 ... Molded product 18 ... Green body 20 ... Movable side mounting plate 21 ... Spacer block 22 ... Receiving plate 23 ... Movable plate 24 ... Projection plate 26...Movable insert 32.34...Protrusion rod 33...Runner 35...Cavity 36...Gate 37.38...Mounting hole 39.40...Spring 41... Joint surface 42...Molded product 43...Body 44...Pivot hole 45...Pivot piece 46...Through hole 47...Protrusion 48...Insert 49...Insert Pressure 50... Fitting portion 9 51... Movable individual element 52... Slide mold 54... Angular pin 55... Guide hole 56... Molding pin 57... Exhaust hole 58...・Mating bottle 59...green body 2,

Claims (2)

[Claims] (1) Injection molding material is injected into an injection mold to injection mold a green body, and the green body after injection molding is taken out from the mold together with fixed and movable inserts, binder removed, and fired. A powder injection molding method characterized in that after the treatment, the molded product is molded by releasing it from the fixed and movable inserts. (2) An exhaust hole is provided in the fixed and/or movable insert that forms the cavity, and a fitting pin that fits into the exhaust hole is provided in a protruding manner on the fixed and movable plate that holds the fixed and movable insert. A powder injection molding device characterized by comprising: