JPS643587B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a molding method in a filling casting method using a fugitive model.

[Prior art]

A filling casting method is known in which a fugitive model made of foamed polystyrene or the like is buried in molding sand, which is a heat-resistant granular material, and molten metal is directly poured into the mold without removing the model from the molding sand. This filling casting method (1) eliminates the need to divide the mold into upper and lower molds and remove the models, (2) eliminates the need to use a core, and (3) eliminates the generation of flash during the product manufacturing process. It has characteristics such as being able to significantly reduce the amount of carbon dioxide, and taking advantage of this characteristic, it is widely used in the production of individual castings such as press molds and mass-produced castings.

In such a filling casting method, once a model is manufactured,
In principle, castings of any shape can be manufactured, but unless the model is sufficiently supported by molding sand, it is difficult to manufacture accurate castings. Therefore, the quality of the molding method becomes an issue.

The following methods are available as molding methods in this filling casting method.

(A) A method in which a fugitive model is placed in the casting flask in advance, and then molding sand containing a binder is filled.

In this method, since the molding sand contains a binder, the fluidity of the molding sand is poor, and therefore there is a problem in filling properties, which makes the molding work very difficult. In addition, this method required extra man-hours and costs to recover and regenerate the molding sand, resulting in poor yield.

In order to solve this problem, there is a method (B) of vacuum molding using molding sand that does not contain a binder (hereinafter referred to as non-caking sand). According to this method, the
Although the filling property is better than in case (A), it is not sufficient and also has the disadvantage that the strength of the mold is weak.

Furthermore, as an improvement to the above (B), there is a molding method (C) in which a pressurization/depressurization tank is provided at the bottom of the flask, non-caking sand is pressurized to flow, and the model is inserted and then fixed under reduced pressure. According to this method, the filling properties of molding sand and mold strength are (B)
However, when producing complex-shaped castings that require a core using a casting method other than the filling casting method, it is not easy to fill the area corresponding to the core with molding sand. Moreover, the strength of the complex-shaped portion was not sufficient to withstand the gas generated by the combustion of expanded polystyrene.

For this reason, the applicant proposed a new molding method (patent application 1984-41357) (unknown) that adds vibration to the above (C), but an even better molding method is needed for manufacturing parts with complex shapes. It was wanted.

[Purpose of the invention]

The present invention was made in order to solve the problems of the prior art described above, and an object of the present invention is to provide a molding method in a filling casting method that has good filling properties and excellent mold strength.

[Structure of the invention]

According to the present invention, such a purpose is to insert a fugitive model into a flask equipped with a pressure means and a depressurizing means at the bottom of the flask, and to embed the fugitive model in the flask with heat-resistant granules. A molding method in a filling casting method, wherein a fugitive model is inserted into a flask while heat-resistant granules are fluidized by the pressure means, and after the fluidization is stopped, the flask is vibrated while the depressurization means is applied. This is achieved by a molding method in the filling casting method, which is characterized by intermittent pressure reduction.

The feature of the present invention over the prior art is that vacuum is intermittently applied while vibration is applied during the molding process.

In the present invention, commonly used foamed polystyrene, foamed polyethylene, foamed polyurethane, etc. can be used as the model material.

Further, as the heat-resistant granules, molding sand, shot, etc. can be used.

In the present invention, the pressurizing means and the depressurizing means are the first
As shown in the figure, they may be provided as pressurized/depressurized tanks, or both may be provided directly within the mold.

In the present invention, the filling properties of the heat-resistant granules can be significantly improved by applying vibration. In particular, it is excellent for filling thin-walled parts and complex-shaped parts with heat-resistant granules, which not only improves filling performance compared to conventional methods, but also increases the packing density of the entire mold and increases the strength of the mold.

It is desirable that this vibration is applied in a direction that sufficiently heat-resistant granules are filled into thin-walled parts and complex-shaped parts while the model is buried. However, it is usually sufficient to add from either the top, bottom, or left/right direction. The magnitude, cycle, and application time of the vibration to be applied should be appropriately determined in consideration of the size, shape, etc. of the model.

In the present invention, the pressure is intermittently reduced at the same time as the vibration. The cycle of this pressure reduction can be determined as appropriate depending on the shape, size, etc. of the model, and can be performed, for example, at intervals of 10 seconds.

[Action of the invention]

According to the present invention, since the pressure is intermittently reduced while vibration is applied, the fluidity of the non-caking sand increases, and the non-caking sand repeats solidification when the pressure is reduced and loosening when the vacuum is stopped. The density gradually increases, and non-caking sand fully penetrates into complex-shaped areas.

〔Effect of the invention〕

Therefore, according to the molding method in the filling casting method according to the present invention, the ability to fill the fugitive model with non-caking sand is significantly improved compared to the conventional method, and filling defects are eliminated even in complex-shaped parts. Moreover, the strength of the mold is also improved. As a result, a cast product of excellent quality without casting defects can be obtained.

Further, according to the present invention, since the filling speed becomes faster, the molding workability is significantly improved.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

Here, FIGS. 1 to 3 are schematic configuration diagrams showing each step of the molding method in the filling casting method according to the present invention, and FIG. Fig. 2 shows a state in which it is buried, and Fig. 3 shows a state in which the pressure is intermittently reduced while applying vibration. Moreover, FIG. 4 is a graph showing the pressure change in the flask in FIG. 3.

In FIGS. 1 to 3, reference numeral 1 denotes a fugitive model made of expanded polystyrene, which consists of a sprue part 1a and a product part 1b. 2 is a flask, and the inside of this flask 2 is divided into upper and lower chambers by a perforated plate 3 with a porosity of about 40% and a pore diameter of 1 to 20 μm at the bottom, and the lower chamber is a pressurization/decompression tank 4. and is connected to the pressurizing/reducing means 5. Furthermore, non-caking sand 6 as heat-resistant granules is charged into the upper chamber of the flask 2, and the flask 2 is fixed on a vibrating device 7.

Further, the pressurization/depressurization tank 4 is connected to external pressurization means and depressurization means via a pressurization/depressurization pipe outlet 8. In this embodiment, a pressure source 9 and a vacuum source 10 are connected to the pressurization/depressurization tank 4 via a solenoid valve 11, and the solenoid valve 11 switches between pressurization and depressurization.

In addition, in FIG. 3, the pressure source 9 and the solenoid valve 11
The path connecting the air gauges 12 and air adjustment valves 1
3. A filter 14 is provided, and a vacuum gauge 15, a vacuum adjustment valve 16, and a valve 17 are provided in a path between the vacuum source 10 and the electromagnetic valve 11. Note that the vacuum system filter 18 is provided between the solenoid valve 11 and the pressurization/depressurization pipe outlet 8.

Using an apparatus having such a configuration, molding and vacuum filling casting were carried out as follows.

First, non-caking sand 6 is charged into the flask 2, and the solenoid valve 11 is switched to the pressurizing side to send air from the pressurizing source 9 to the pressurizing/reducing tank 4. This air causes the non-caking sand 6 to flow through the perforated plate 3. In this flowing state, the fugitive model 1 is buried in the flask 2 as shown in FIG. FIG. 2 shows a state in which the fugitive model 1 is completely buried in the non-caking sand 6. In FIG. 2, the cross-hatched areas are often not filled with the non-caking sand 6, resulting in poor filling.

Subsequently, as shown in FIG. 3, while applying vibration to the flask 2 using the vibration device 7, the vacuum source 10, which has been switched to the vacuum side by the solenoid valve 11, sends the flask through the pressurization/depressurization tank 4. The pressure inside the flask 2 is intermittently reduced. In this embodiment, the operating cycle is as follows:
Decompression was repeated for 8 seconds and decompression stopped for 4 seconds for 60 seconds. FIG. 4 shows the pressure change inside the flask 2 at this time.

According to this example, the non-caking sand that has solidified under reduced pressure is released by stopping the vacuum, and is depressurized again, which is repeated, giving fluidity to the non-caking sand and creating a complex structure. Non-caking sand is filled into every corner of the evanescent model.

Using the mold formed as described above, the upper surface of the flask was covered with a fugitive film, and the inside of the flask was depressurized to carry out vacuum filling casting. The resulting cast product was free of waste material and was of excellent quality. This confirmed that the mold of this example had no filling defects and had excellent strength.

In addition, in this example, after the disappearing model is buried,
It can be molded in 60 seconds, greatly improving work efficiency compared to conventional methods.

Although specific embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and includes various embodiments within the scope of the claims. .

For example, if it takes time to reach a predetermined degree of reduced pressure due to insufficient capacity of the vacuum source, the upper surface of the flask may be covered with a fugitive film 19 as shown in FIG.

In addition, a rotary actuator with a ball valve and a vacuum source can be used as external pressurization and depressurization means, and if this rotary actuator with a ball valve is used, the structure is simpler than in the embodiment. Can perform pressure and depressurization.

[Brief explanation of drawings]

1 to 3 are schematic configuration diagrams showing each step of the molding method in the filling casting method according to the present invention,
Figure 1 shows a state in which a fugitive model is buried by flowing heat-resistant granules, Figure 2 shows a state in which a fugitive model is buried, and Figure 3 shows a state in which a fugitive model is buried while applying vibration. FIG. 4 is a graph showing the pressure change in the flask in FIG. 3, and FIG. 5 is a schematic diagram showing another embodiment of the present invention. 1... Vanishing model, 1a... Sprue part, 1b...
Product department, 2... Casting flask, 3... Perforated plate, 4... Pressurization/decompression tank, 5... Pressurization/decompression means, 6... Non-caking sand (heat-resistant granules), 7... Vibration device, 8...
Pressurization/decompression pipe outlet, 9...Pressure source, 10...
... Vacuum source, 11 ... Solenoid valve, 12 ... Air gauge, 13 ... Air adjustment valve, 14 ... Filter, 1
5... Vacuum gauge, 16... Vacuum adjustment valve, 17...
...Valve, 18...Filter, 19...Erasable film.

Claims (1)

[Scope of Claims] 1. A filling casting method in which a fugitive model is inserted into a flask equipped with a pressure means and a pressure reduction means at the bottom of the flask, and the fugitive model is embedded in the flask with heat-resistant granules. In the molding method, a fugitive model is inserted into the flask while the heat-resistant granules are fluidized by the pressurizing means, and after the flow is stopped, the molding method is intermittently applied by the depressurizing means while applying vibration to the flask. A molding method in the filling casting method, which is characterized by reducing the pressure to .