JPS61245941A - Vacuum molding method - Google Patents

Abstract

PURPOSE:To eliminate the defect by the blow of a casting by discharging forcibly the gas generated from a core to the outside of a casting mold through a vent hole provided to a core print part. CONSTITUTION:A suction device 39 such as vacuum pump is disposed via a communicating pipe 38 to the top of the vent hole 26. The gas generated from the core 24 is discharged through the hole 26 and the pipe 38. A riser cavity 27 acts consequently as the intrinsic vent hole and the external air is admitted therein accordingly. The gas generated from the core is forcibly discharged by the suction device disposed to the vent hole in the above-mentioned manner, by which the defect arising from the blow of the casting is eliminated.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to improvement of metal casting manufacturing technology,
The aim is to improve quality by adding innovation to the reduced pressure molding method, which has been widely put into practical use in recent years.

(Conventional technology) In the vacuum molding method, which uses a mold whose surroundings are covered with a plastic film and whose interior is suctioned by a vacuum pump, the apparent hardness of the mold increases due to the pressure difference between the inside and outside of the mold, making it difficult to cast molten metal. In this case, if a ventilation hole is provided in the product cavity to supply sufficient outside air, the pressure difference will be maintained even if the film is burned out, resulting in a casting that is both healthy and beautiful in appearance. .

However, when producing castings that require a core in shape using this method, scum is generated due to combustion of the hardening agent for the core, such as resin, and defects in appearance such as blow-outs are likely to occur.

For this reason, vents were built in the baseboards to allow the gas to escape.

(Problem that the invention seeks to solve) However, as the core used becomes larger or is placed so as to be wrapped in the product, a large amount of gas is generated and it becomes impossible to exhaust it all using the ventilation holes in the baseboard etc. . Moreover, in the case of large items, the molten metal is easily inserted, and the core also requires a coating mold. Since an organic agent such as alcohol is used as a solvent for the coating mold, the amount of combustion gas increases, which causes blowing defects.

As mentioned above, it is an important issue how to effectively discharge the gas generated during the casting of products using cores using the vacuum molding method.

(Means to solve the problem) The present invention solves the aforementioned problems.

In other words, careful efforts were made to force the gas generated from the core's hardening agent or the coating solvent to be forced out, rather than letting it escape naturally, through vents installed in the small wood.

(Operations and Embodiments) The operations of embodiments of the present invention will be explained with reference to the drawings.

FIGS. 1 and 2 are schematic longitudinal cross-sectional views in which ventilation holes are provided in the core wood in the horizontal vacuum molding method.

FIG. 1 shows a conventional example, and FIG. 2 shows an example of the present invention.

As shown in Figure 1, in the vacuum molding method, molds (upper mold 1, lower mold 2)
The outer periphery of the plastic film 5, 13 and the flask 9,
14, and remove the dry silica sand 12.17 from the suction tube 1.
It was sucked and held by a vacuum pump (not shown) through 0.11 and 15.16. When pouring molten metal, the film burns due to heat, but the vent hole 6 or riser 7
By allowing more outside air to flow in and preventing negative pressure in the product cavity 3, the mold will not break due to the pressure difference between the inside and outside of the mold, and a beautiful-looking casting can be produced.

However, for products whose shape requires a core 4, consideration must be given to a means for exhausting the gas generated by the core.

That is, since gas is generated from the core during pouring, the pressure in the product cavity 3 becomes high, and outside air does not flow in. Rather, the generated gas is discharged through the vent hole 6. At the beginning of the molten metal solidifying, there is an escape route for the generated gas, but at the end, the surrounding area is blocked, resulting in residual gas defects in the product. In order to prevent this, it is necessary to forcibly discharge the gas and use the vent as a natural inflow path for outside air.

As an example, as shown in FIG. 2, a suction device 39f such as a vacuum pump is connected to the end of the ventilation hole 26 through a communication pipe 38.
Just place it. As a result, the gas generated from the core is discharged via the ventilation hole 26 and the 38ft communication pipe, so the riser cavity 27 acts as a proper ventilation hole and outside air flows in (the air flow is shown by the arrow (↑)). will be done. In this embodiment, the suction device 39 is disposed outside the mold, but an existing suction device can also be used to connect directly to the suction pipe 30 inside the mold.

(Effects of the Invention) As described above, by disposing the suction device in the ventilation hole, the gas generated from the core can be forcibly discharged, and defects caused by blowing of the casting can be eliminated.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional view of a conventional horizontal vacuum molding method, and FIG. 2 shows an embodiment of the present invention. 1.21? Mold (upper mold), 2.22 = mold (lower mold),
3.23=Product cavity part, 4.24: Core, 5,1
3.25.33: Film, 6.26: Ventilation hole, ? ,2
7: Riser, 8.28: Sprue, 9.14.29.34:
Casting flask, 10.11.15, 16°30.3], 35.3
6: Suction tube, 12.1? , 32°37.32.37:
Silica sand, 38: Communication pipe, 39: Suction device (vacuum pump). Figure 1

Claims (1)

[Claims] In the horizontal vacuum molding method, where the outer periphery is covered with a plastic film and a casting flask, and the inside is maintained at negative pressure, when manufacturing castings including cores, the gas generated by the core is placed in the baseboard. A vacuum molding method characterized by forcibly discharging the mold to the outside of the mold through a vent hole using suction means.