JPH05124018A - Low pressure injection molding machine for ceramic slurry - Google Patents

Abstract

PURPOSE:To provide a low pressure injection molding device for ceramic slurry which can surely mold a net shape molded item having high strength under condition of short molding cycle even if a molded item of final product having complex shape and chamfered portion on the end surface of cylindrical part is molded. CONSTITUTION:A chamfered portion 15 which is gradually radially expanded is formed in a cylindrical gate hole 3a at the location of the forward end of a push rod 14. When ceramic slurry is fed, since an ultrasonic wave vibrator 16 is provided around the chamfered portion 15, fluidity of the slurry is increased, preventing thereby the air in said portion 15 from being drawn into the slurry. The push rod 14 sliding through the hole 3a maintains the pressure in a cavity 4, so that a net shape molded item in which a chamfer is formed on the end surface of cylindrical part is molded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a low pressure injection molding apparatus for a ceramic slurry, which is used in combination with a split mold to obtain a molded product by low pressure injection molding of a ceramic slurry. That is, when the final product made of ceramic has a complicated shape, a final molded product having a complicated shape is required to obtain the final product. The low-pressure injection molding apparatus for a ceramic slurry of the present invention obtains a molded product (hereinafter, referred to as a net shape molded product) similar to the final molded product.

[0002]

2. Description of the Related Art Conventionally, as a press-fitting molding apparatus for ceramic products used by being combined with a split mold, a discharge port communicating with a gate hole of a lower mold and a molding material through the discharge port into a cavity of the mold. An injection chamber for supplying and a metering piston slidably arranged in the injection chamber for injecting the molding material into the cavity from the discharge port through the gate hole by the forward movement and introducing the molding material into the injection chamber by the backward movement. The one provided is known (JP-A-57-32902).

When molding a molded product of a ceramic product by this press-fitting molding apparatus, first, the measuring piston is retracted to introduce the molding material into the injection chamber, and then the measuring piston is advanced to discharge the molding material in the injection chamber. It is injected into the cavity through the gate hole. Then, the measuring piston is further advanced to hold the pressure in the cavity, and a molded product is obtained.

[0004]

For example, in order to manufacture a final product having a complicated shape such as a ceramic turbo rotor,
To obtain the molded product, generally, a ceramic slurry having a low viscosity is prepared by mixing a large amount of a solvent with a ceramic powder together with a sintering aid, a dispersant, etc., and this ceramic slurry is molded by a low pressure injection molding method. To do.

However, if such a ceramic slurry is molded by the low-pressure injection molding device of the above-mentioned press-fitting molding device type, a metering piston sliding in the injection chamber injects the ceramic slurry into the cavity, and Since the pressure is also held, a part of the injection chamber forms a tab integral with the molded product, and a net-shaped molded product cannot be obtained. Therefore, if the molded product is post-processed into a net shape molded product, problems such as deformation of the molded product will occur, and it will be easy to cut the sintered product obtained by sintering the molded product to the final product. This would cause great difficulty.

Further, in the above-mentioned press-fitting molding apparatus, while the pressure of the ceramic slurry is being held by the measuring piston, the ceramic slurry cannot be introduced into the injection chamber for the next cycle, resulting in a long molding cycle. , The manufacturing cost of the final product will increase. Therefore, it is conceivable to equip the low-pressure injection molding apparatus of the press-fitting molding apparatus type with a push-cut rod as previously proposed by the present applicant (Japanese Patent Application No. 2-102669). In this low-pressure injection molding apparatus, the push-cut rod moves independently of the measuring piston while slidingly contacting the measuring piston. Then, the push-cut rod is slidably moved in the gate hole and the discharge port by retracting with respect to the measuring piston to open the discharge port. Further, the push-cut rod moves forward with respect to the measuring piston to slidably move in the discharge port while cutting off the ceramic slurry in the injection chamber to close the discharge port and slide in the gate hole. It moves freely to hold the pressure of the ceramic slurry injected into the cavity. Therefore, according to such a low-pressure injection molding apparatus, the push-cut rod, which is slidably contacted independently of the measuring piston, closes the discharge port and holds the ceramic slurry in the cavity, so that the injection chamber has a tab integrated with the molded product. It is possible to obtain a net shape molded product without forming it. Further, according to this low-pressure injection molding device, since the pressure of the ceramic slurry is held by the push-cut rod, while the push-cut rod holds the discharge port in the closed state, the measuring piston is moved backward to move the injection chamber. The ceramic slurry can be introduced into the mold, and the molding cycle can be shortened.

However, in the above-mentioned ceramic turbo rotor and the like, the shaft is formed in a cylindrical shape. In order to manufacture a final product having such a complicated shape and a cylindrical portion, if the net shape molded product is molded by the above-mentioned low-pressure injection molding device, the gate hole of the mold will have a substantially cylindrical shape. Need to be formed. However, unless the gate hole is formed in a substantially cylindrical shape in the low-pressure injection molding apparatus, the end face of the cylindrical portion of the net-shape molded product is formed when the push-cut rod slides in the gate hole to hold the ceramic slurry. A pin angle is formed on the net, and the net shape molded product has a very weak pin angle. Therefore, the final product is also very weak at this pin angle, and it is difficult to obtain a highly reliable final product. Therefore, as shown in FIGS. 3A to 3C, in order to form a chamfer on the end face of the cylindrical portion of the net shape molded product, the front end position of the push-cut rod (not shown) in the gate hole 31 is gradually increased. Expanded diameter chamfer forming portion 31a
Can be formed. However, when the chamfer forming portion 31a having an enlarged inner diameter is formed along the molding flow path in this manner, several thousand mPa · s injected by the push-cut rod.
The ceramic slurry S having a viscosity of about sec is shown in FIG.
As the flow of (c) to (c) occurs, the air A is entrained in the chamfer forming portion 31a, and the chamfer cannot be reliably formed on the end face of the cylindrical portion of the net shape molded product.
In addition, the ceramic slurry containing air may flow into the cavity and cause a defect in the molded product.
In such a case, in general resin molding, it is possible to almost ignore the entrainment of air by changing the die swell ratio, but in low pressure injection molding using a low viscosity ceramic slurry, this means is used. Cannot be adopted. Further, in the high pressure injection molding of the ceramic slurry for molding a molded product having a simple shape using the high viscosity ceramic slurry, the inside of the cavity is evacuated, but in the low pressure injection molding, a highly volatile organic solvent is used. A solvent may be used in some cases, and in this case, the tip portion of the ceramic slurry is solidified by vacuuming, jetting or the like may occur, and therefore this means cannot be used either.

The present invention has been made in view of the above circumstances, and even when a molded product of a final product having a complicated shape and a chamfered portion on the end face of a cylindrical portion is molded with a low-viscosity ceramic slurry. An object of the present invention is to provide a low-pressure injection molding device for a ceramic slurry that can reliably mold a high-strength net shape molded product under a short molding cycle.

[0009]

A low-pressure injection molding apparatus for a ceramic slurry of the present invention is used in combination with a split mold, and has a discharge port communicating with a gate hole of the mold and a discharge port through the discharge port. An injection chamber for supplying the ceramic slurry into the cavity of the mold, a raw material supply unit for supplying the ceramic slurry to the injection chamber, and a slide chamber that are slidably arranged in the injection chamber, and discharge the ceramic slurry by advancing. The metering piston, which is injected from the outlet into the cavity through the gate hole and introduces the ceramic slurry from the raw material supply section into the injection chamber by retreating, is independent of the metering piston while slidingly contacting the metering piston. And then retreat to slidably move in the gate hole and the discharge port to open the discharge port, and to move forward to push out the ceramic slurry in the injection chamber. And a push-cut rod that slidably moves in the discharge port to close the discharge port and slidably moves in the gate hole to hold the ceramic slurry injected into the cavity. The gate hole is formed in a substantially columnar shape, and a chamfer forming portion having a gradually enlarged diameter is formed at a front end position of the push-cut rod in the gate hole, and a vibrating means is provided in a peripheral region of the chamfer forming portion. Is provided.

[0010]

When a low-pressure injection molding apparatus for a ceramic slurry of the present invention is used to mold a final product having a complicated shape and a cylindrical portion such as a ceramic turbo rotor, first, a push-cut rod is used. Is moved relative to the metering piston to move inside the discharge port, thereby closing the discharge port. In this state, the measuring piston is retracted to introduce the ceramic slurry from the raw material supply section into the injection chamber.

Then, the push-off rod is retracted with respect to the measuring piston to move inside the discharge port, thereby opening the discharge port. Then, the metering piston is moved forward, and the ceramic slurry in the injection chamber is injected from the discharge port into the cavity through the gate hole. At this time, since the vibrating means is arranged in the peripheral area of the chamfer forming portion formed in the gate hole, the fluidity of the ceramic slurry injected through the gate hole is increased in the chamfer forming portion, and Does not cause air entrapment.

Thereafter, the push-cut rod is again moved forward with respect to the measuring piston to move inside the discharge port,
The ceramic slurry in the injection chamber is pushed off and the discharge port is closed, and the gate hole is moved to hold the ceramic slurry injected into the cavity. At this time, in this low-pressure injection molding apparatus, the push-cut rod that slides independently of the measuring piston closes the discharge port and holds the ceramic slurry in the cavity, so that the injection chamber forms a tab integral with the molded product. Never.

In this way, the ceramic slurry is held in the cavity through the substantially cylindrical gate hole, so that a net shape molded product having a cylindrical portion is formed. At this time, in this low-pressure injection molding apparatus, since the chamfer forming portion is formed at the front end position of the push-cut rod in the gate hole, when the push-cut rod slides in the gate hole to hold the ceramic slurry, the net A chamfer without air entrapment is reliably formed on the end surface of the cylindrical portion of the shape molded product. Therefore, the strength of the net shape molded product is ensured because there is no pin angle.

When the holding pressure of the ceramic slurry ends, the die is opened while the push-off rod is retracted, and the net shape molded product is taken out. While the push-cut rod closes the discharge port when the pressure is held or the mold is opened, the metering piston is retracted,
The ceramic slurry is introduced into the injection chamber from the raw material supply unit for the next cycle. Thus, in this low-pressure injection molding apparatus, the molding cycle can be shortened.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, this low-pressure injection molding apparatus is used by connecting an injection unit to a split mold composed of a movable mold 1, a slide core 2 and a fixed mold 3. A turbo rotor-shaped cavity 4 is formed in the slide core 2, and a cylindrical shaft forming hole 1 a that communicates with the cavity 4 and forms a part of the shaft of the turbo rotor is formed in the movable mold 1. A columnar gate hole 3a communicating with the cavity 4 and coaxial with the shaft forming hole 1a and forming a part of the shaft is formed in the shaft 3. A piston 6 pressed by the spring 5 toward the cavity 4 is slidably mounted in the shaft forming hole 1a of the movable die 1, and a center hole forming member 6a is fixed to the lower end of the piston 6. Further, the movable die 1, the slide core 2 and the fixed die 3 are formed with cooling holes 7 through which cooling oil is circulated in the peripheral regions of the shaft forming hole 1a, the cavity 4 and the gate hole 3a.

A push-cut rod 1 described later is provided in the gate hole 3a.
A chamfer forming portion 15 having a diameter increased by 45 ° is formed at the front end position of No. 4, and the chamfer forming portion 15 has a peripheral area of 45
An ultrasonic transducer 16 of kHz and 60w is arranged.
The fixed die 3 is in contact with a heat insulating material 8 which is in communication with the gate hole 3a and in which a communication hole 8a having the same diameter as the gate hole 3a is formed, and the injection unit is connected to the fixed die 3 through the heat insulating material 8. Are combined. In this injection unit, a discharge port 9 having the same diameter as that of the gate hole 3a, which communicates with the gate hole 3a through the communication hole 8a, is formed, and below the discharge port 9, the discharge port 9 is communicated with and a circle having a larger diameter than the discharge port 9 is formed. A columnar injection chamber 10 is formed. A heating hole 17 through which hot oil is circulated is formed in the peripheral areas of the discharge port 9 and the injection chamber 10. A supply pipe 12 which is opened and closed by an on-off valve 11 and is connected to a tank (not shown) is connected to the front end of the injection chamber 10. In addition, the injection chamber 10
Has an annular measuring piston 13 arranged so as to be able to move forward and backward, and a push-cut rod 14 that is movable independently of the measuring piston 13 while slidingly contacting the measuring piston 13 is provided in the center hole of the measuring piston 13. It is equipped. A center hole forming member 14a is fixed to the upper end of the push-cut rod 14.

A ceramic turbo rotor molded product was molded by the low-pressure injection molding apparatus having the above-described structure. First, silicon nitride, alumina, and yttria were mixed with industrial gasoline and a dispersant for 72 hours in a ball mill, and 10 volume% of 12-hydroxystearic acid was added under heating at 80 ° C. to a powder concentration of 50 volume%. A ceramic slurry of was prepared. At this time, the viscosity of this ceramic slurry was about 10,000 cps. The ceramic slurry is charged into a tank, the temperature of the cooling oil is set to 50 ° C, and the temperature of the hot oil is set to 80 ° C.
Set to.

After that, the push-off rod 14 is moved forward with respect to the measuring piston 13 and moved inside the discharge port 9, so that the discharge port 9 is closed. In this state, the metering piston 13 is retracted and the on-off valve 11 is opened to introduce the ceramic slurry from the tank into the injection chamber 10 via the supply pipe 12 and the on-off valve 11. Then, the push-cut rod 14
Is moved backward with respect to the metering piston 13 and moved in the discharge port 9 to open the discharge port 9, and at the same time, the on-off valve 11 is closed. After that, the measuring piston 13
And the ceramic slurry in the injection chamber 10 is injected from the discharge port 9 into the cavity 4 through the communication hole 8a and the gate hole 3a at a pressure of ² kg / cm ² and a speed of 5 cc / sec. At this time, in this low-pressure injection molding apparatus, since the ultrasonic transducers are arranged in the peripheral region of the chamfer forming section 15, the fluidity of the ceramic slurry injected through the gate hole 3a is increased in the chamfer forming section 15. It also increases in the horizontal direction, and air is not entrained in the chamfer forming portion 15.

After that, the push-out rod 14 is again moved forward with respect to the metering piston 13 and moved inside the discharge port 9 so that the ceramic slurry in the injection chamber 10 is cut off and the discharge port 9 is closed. , Further gate hole 3a
The inside is moved to the lower position of the chamfer forming portion 15, and the ceramic slurry injected into the cavity 4 is held under pressure for 3 minutes. At this time, in this low-pressure injection molding apparatus, the push-cutting rod 14 that slides independently of the measuring piston 13 holds the ceramic slurry in the cavity 4 and forms the center hole with the center hole forming member 14a. Therefore, unlike the conventional case, the injection chamber 10 does not form a tab integrated with the molded product. At this time, the piston 6 pressed by the spring 5 in the shaft forming hole 1a of the movable die 1
Opposes the push-cut rod 14, holds the ceramic slurry from the other side, and forms the center hole by the center hole forming member 6a.

In this way, the ceramic slurry is held in the cavity 4 through the cylindrical gate hole 3a,
A net shape molded product having a cylindrical portion is formed. At this time, in this low-pressure injection molding apparatus, the chamfer forming portion 15 is formed at the front end position of the push-cut rod 14 in the gate hole 3a, so that the push-cut rod 14 moves in the gate hole 3a.
When the ceramic slurry is held under pressure by sliding inside, a chamfer 20 without air entrapment is surely formed on the end surface of the cylindrical portion of the net shape molded product, as shown in FIG. For this reason, the net shape molded product has no pin angle, so that the strength is secured.

After the holding pressure of the ceramic slurry is finished and cooling is further performed for 2 minutes, the movable die 1 is raised while the push-off rod 14 is retracted, the slide core 2 is opened left and right, and the net shape molded product is taken out. While the push-cut rod 14 closes the discharge port 9 when the pressure is held or the mold is opened, the metering piston 13 is retracted, and the injection chamber 10 is used for the next cycle.
A ceramic slurry is introduced into the inside from a tank or the like. Thus, in this low-pressure injection molding apparatus, the molding cycle can be shortened.

[0022]

As described above in detail, in the low pressure injection molding apparatus for ceramic slurry of the present invention, since the structure described in the claims is adopted, a complicated shape and a cylindrical portion are formed. Even if the molded product of the final product is molded with a low-viscosity ceramic slurry, a high-strength net shape molded product can be reliably molded under a short molding cycle.

That is, specifically, the following excellent effects are obtained. (1) Even if the final product has a complicated shape such as a ceramic turbo rotor and has a columnar portion, the net shape molded product can be molded. Then, since the net shape molded product may be post-processed into a final molded product by a simple method, it is possible to solve problems such as shape collapse due to complicated post-processing. Further, since a final product is obtained by sintering the final molded product of the net shape molded product, it is possible to reduce the extremely difficult work of cutting the sintered product to the final product. (2) Even if the final product has a complicated shape and a columnar portion, the molding cycle can be shortened, so that the manufacturing cost of the final product can be reduced. (3) A chamfer can be formed on the end surface of the cylindrical portion of the net shape molded product by the chamfer forming portion formed on the substantially cylindrical gate. At this time, since the vibrating means is arranged in the peripheral region of the chamfer forming portion, the net shape molded product does not contain air, and the chamfer portion is also reliably formed. Therefore, since the net shape molded product has no pin angle on the end face of the cylindrical portion, the final product has high strength and high reliability.

[Brief description of drawings]

FIG. 1 is a sectional view of a low pressure injection molding apparatus according to an embodiment.

FIG. 2 is a cross-sectional view of a turbo rotor molded by the low pressure injection molding apparatus of the embodiment.

3 (a), (b) and (c) are cross-sectional views showing a main part of a low pressure injection molding apparatus in which a chamfer forming portion is provided in a gate hole.

[Explanation of symbols]

1 ... Movable type 2 ... Slide core 3
... Fixed type 4 ... Cavity 3a ... Gate hole 9
… Discharge port 10… Injection chamber 11… Open / close valve 1
2 ... Supply pipe 13 ... Measuring piston 14 ... Push-off rod 1
5 ... Chamfer forming part 16 ... Ultrasonic transducer

Claims (1)

[Claims] 1. A discharge port which is used in combination with a split mold and which communicates with a gate hole of the mold, and an injection chamber which supplies the ceramic slurry into the cavity of the mold through the discharge port. A raw material supply unit that supplies the ceramic slurry to the injection chamber, and a slide unit that is slidably disposed in the injection chamber, and forwardly injects the ceramic slurry from the discharge port into the cavity through the gate hole and then retreats. The metering piston for introducing the ceramic slurry into the injection chamber from the raw material supply section moves independently of the metering piston while being in sliding contact with the metering piston, and slides in the gate hole and the discharge port by retreating. The discharge port is freely moved to open the discharge port, and the ceramic slurry in the injection chamber is pushed forward to slidably move inside the discharge port to close the discharge port. A straw cutter rod pressure holding the ceramic slurry which is injected into the cavity by moving the bore slidably,
The gate hole is formed in a substantially columnar shape, and a chamfered formation portion having a gradually increased diameter is formed in the front end position of the push-cut rod in the gate hole, and a vibration is formed in a peripheral region of the chamfered formation portion. A low-pressure injection molding apparatus for ceramic slurry, characterized in that means are provided.