JPH02292026A - Molding method of foam casting model - Google Patents

Abstract

PURPOSE:To prevent moisture from being contained inside, and save the drying process by filling a predetermined foamable beads into a molding cavity formed with a core mold and cavity mold provided with no vent hole opened in the cavity forming surface, and supplying steam behind the mold. CONSTITUTION:By the use of molds (cavity mold 18, core mold 20) not provided with a vent hole, predetermined foamable beads made up of polystyrene resin completed in a prefoaming and maturing process are filled into a molding cavity 22 formed by putting both molds in superposed relation. Heating is conducted by introducing steam through the pipes 14, 14 disposed behind the molds 18, 20, wherein the foamable beads in the molding cavity are foamed sufficiently, and water is spouted instead of steam through the pipes 14, 14, a foamed molding in the molding cavity 22 is cooled up to predetermined temperature. In the interior of a formed molding obtained herein there is not contained water, thus, a drying process is unnecessary.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a method for molding a foam casting model, and in particular, to advantageously molding a foam casting model used in the full molding method by preventing moisture from penetrating inside. It is about the method.

(Background Art) Conventionally, as one of the casting methods, a model made of resin such as expanded polystyrene is used, the model is buried in a predetermined molding sand, and then a predetermined molten metal is poured into the part of the model. Therefore, a full mold method is adopted in which the model is made to disappear by the heat of the molten metal, and the molten metal is filled into the part where the model disappears to form a casting having the same external shape as the model.

Incidentally, such a foam casting model, in other words, a vanishing mold, is generally formed using a molding device (forming mold) as schematically shown in FIG. 1, for example.

That is, by using a cavity mold 4 and a core mold 6 made of metal such as aluminum alloy, first, the outer shape of the target model is given, in which heating and cooling spaces are respectively formed in the back due to the presence of the frame 2. A space (molding cavity) 16 between the cavity mold 4 and the core mold 6 is filled with a predetermined volume of foamed beads that have undergone a predetermined pre-foaming and aging process from a feeder (not shown) via a raw material supply hose 10. be done. At this time, the air present in the molding cavity 16 is evacuated by a vacuum pump (not shown) through a plurality of vent holes 8 provided to open inside and outside the cavity mold 4 and the core mold 6. It has become. Note that 12 is a suction pipe that also serves as an ejector bin, and is integrally provided so as to communicate with the raw material supply hose 10, and when filling is completed, the foamed beads remaining in the hose 10 are pulled back by suction. , and its ejecting action allows the formed foam molded article to be released from the mold.

Then, after filling the foamed beads, the vibrator 1 is placed in the empty space behind the cavity mold 4 and the core mold 6.
4.14, steam is introduced to heat the cavity mold 4 and core mold 6 from the back, and the steam is also blown into the molding cavity 16 through the vent hole 8. As the filled foam beads further foam, the foam beads fuse together, filling the gaps between the foam beads and forming a shape corresponding to the molding cavity 16.

After the end of such foaming, through the pipe 14.14,
After water is injected instead of steam and the foamed molded product in the molding cavity 16 is cooled to a predetermined temperature, the cavity mold 4 and core mold 6 are released, and the desired foamed molded product is usually It will be extracted according to this method.

By the way, in the foamed molded product obtained in this way, during heating during molding, steam blown into the molding cavity 16 through the vent hole 8 condenses inside the foamed molded product. Water that remains or used for cooling after foaming similarly enters the foamed molded product through the vent hole 8, so the foamed molded product taken out after the completion of the molding process is usually ,
Contains approximately 10-20% water.

When this foam molded body is used as a foam casting model and a casting is manufactured by the full mold method,
The injected high-temperature molten metal rapidly vaporizes the moisture contained on the surface and inside of the foam molded body,
This causes defects in the resulting casting. Therefore, in order to prevent such defects, the foam molded product taken out from the cavity mold 4 and the core mold 6 is usually subjected to a drying operation such as natural drying or hot air drying.

However, in such a drying process, depending on the shape and size of the foam molded product, natural drying results in a drying time of 2 to 4
Approximately 2 to 4 weeks with hot air drying at approximately 50°C
Since drying time of several hours is required, and appropriate equipment is also required, there are problems in terms of productivity and manufacturing costs.

(Solution Section H) The present invention has been made against this background, and the problem to be solved is that the foam casting model used in the full mold method etc. It is an object of the present invention to provide an advantageous method of molding without allowing moisture to be contained, and thus without requiring a drying step.

(Solution Means) In order to solve the above-mentioned problems, the present invention uses a core mold and a cavity mold that are not provided with a vent hole that opens on the cavity forming surface, and forms a cavity with both of these molds. The foam beads are filled with a specified number of foam beads into a molding cavity, and steam is supplied behind the core mold and the cavity mold to heat the foam beads, and then the mold is cooled. hand,
The gist of the present invention is a method for forming a foam casting model, which is characterized in that the intended foam casting model is taken out of the mold.

(Specific Configuration) Below, in order to clarify the present invention more specifically, the configuration of the present invention will be explained in detail with reference to the drawings.

Note that an example of the molding die (device) used in the present invention is
Although shown schematically in FIG. 2, structures similar to the conventional example are designated by the same reference numerals as in the conventional example shown in FIG.

First, the cavity mold 18 and the core mold 20 are provided with a frame 2 on their backs, and heating and cooling spaces are provided behind them, as in the past, but unlike in the past, these cavities are No vent holes are provided on the forming surface. Then, using the cavity mold 18 and the core mold 20, a predetermined amount of foamed beads made of polystyrene resin that has undergone the normal pre-foaming and aging process is fed into the cavity through the raw material supply hose IO in the same manner as before. A molding cavity 22 formed by overlapping the mold 18 and the core mold 20 is filled. At this time, the air existing in the molding cavity 22 is sucked to the outside of the space 22 by a vacuum pump (not shown) provided in communication with the molding cavity 22, and the filling of the foamed beads is stopped. It can be done in the closest way. Note that, after the filling is completed, the foamed beads remaining in the raw material supply hose 10 are discharged to the outside via the suction pipe 12.

As the cavity mold 18 and the core mold 20 used here, metal such as aluminum alloy is usually suitably employed, but the material, shape, thickness, etc. may be changed as appropriate depending on the intended foam molded product. will be selected.

After the filling is completed, the cavity mold 1 is heated by steam introduced at a predetermined steam pressure and time through predetermined pipes 14 and 14 disposed in the spaces behind the cavity mold 18 and the core mold 20, respectively.
8 and core mold 20 are heated, thereby foaming the foamed beads filled in the molding cavity 22, and melting the foamed beads to each other so as to fill the molding cavity 22. be done. In this step as well, the inside of the molding cavity 22 is maintained under reduced pressure by the vacuum pump, and the air between the foam beads is sucked during foaming of the foam beads, so that the foam beads are successfully foamed. It is.

Next, water is injected into the cavity mold 18 and the core mold 20 for a predetermined period of time through the pipes 14, 14, so that the foamed molded product in the molding cavity 22 reaches a temperature below a predetermined temperature, in other words. The material is cooled to below the softening point of the foamed resin material such as polystyrene resin. In addition, in the present invention, in addition to cooling by water cooling,
It is also possible to employ any of the usual cooling methods, such as air cooling, natural cooling, etc., or a suitable combination thereof.

Thereafter, the cavity mold 18 and the core mold 20 are released, and the molded foamed product is taken out by an ejection operation using the suction pipe 12 or according to a normal extrusion operation using compressed air, an eject pin, etc. do,
A foam casting model containing no moisture can be obtained.

(Examples) Examples of the present invention will be shown below to clarify the present invention more specifically, but the present invention is not limited in any way by the description of such examples. It goes without saying that this is not the case.

In addition to the following examples and the above-mentioned specific description, the present invention includes various changes, modifications, and changes based on the knowledge of those skilled in the art, as long as they do not depart from the spirit of the present invention. It should be understood that improvements and the like may be made.

First, using a mold without a vent hole as shown in FIG. 2 (cavity mold 1B, core mold 20), in a molding cavity (22) formed by overlapping both molds, Expanded beads made of polystyrene resin that had undergone a predetermined pre-foaming and aging process were filled for 4 seconds. Then, a steam pressure of 0.0. By introducing steam and heating under the conditions of 6 kg/cm" and heating time = 12 seconds,
After the foamed beads in the molding cavity were sufficiently foamed, water was injected instead of steam for 12 seconds through the pipe (14.14) to cool the foamed product in the molding cavity (22) to a predetermined temperature. . After cooling, the foam molded product (foam casting model) taken out from the mold has a size of 300 M openings x 10 mm, and an internal moisture content of 0.4.
%Met.

On the other hand, for comparison, a mold (cavity mold 4, core mold 6) in which a predetermined number of vent holes (8) are provided as shown in FIG. In the same manner as described above, foamed beads made of polystyrene resin were filled into the space 16) for 4 seconds. Next, the pipe (14.1) placed behind the mold (4, 6)
4) Steam pressure: 0. 6 kg/cm”
After heating the foamed beads by spraying steam under the conditions of heating time = 10 seconds, the foamed beads were sufficiently foamed, and then water was added instead of steam through the pipe for 10 seconds.
The mixture was sprayed for a second, and the foamed molded product was cooled to a predetermined temperature. After that, remove it from the mold and heat it with warm air at 50°C for 30 minutes.
Furthermore, it was dried naturally for about 3 weeks, and the result was 30OII.
A foam molded body (foam casting model) with a diameter of IIll opening x 10 mm'- was obtained. In this foamed molded article, the moisture content contained inside was 8%.

As is clear from this result, the foam casting model obtained according to the present invention has a low moisture content inside, and therefore, using the foam casting model, a desired casting can be made by the full mold method. Even when casting, there are no defects in the resulting casting.

(Effects of the Invention) As is clear from the above description, the present invention provides a method for molding a foam casting model using a cavity mold and a core mold in which no vent hole is provided, and the molding process thereof. During heating and cooling, the foamed beads and foamed molded product do not come into direct contact with steam or water, so there is no moisture contained inside the resulting foamed molded product, so a drying process is not necessary. Since the molding time can be significantly shortened, productivity can be advantageously improved.

In addition, since the equipment necessary for the drying process is not required,
Its manufacturing costs can also be advantageously reduced.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional explanatory diagram schematically showing an example of a conventionally used molding device, and FIG. 2 is a cross-sectional explanatory diagram schematically showing an example of a molding device used in the present invention. . Figure 1 2: Frame lO: Raw material supply hose 14: Pipe 18: Cavity type

Claims (1)

[Claims] A core mold and a cavity mold that are not provided with a vent hole that opens on the cavity forming surface are used, and the molding cavity formed by these two molds is filled with specified foam beads. A foam casting model characterized in that the foam beads are foam-molded by supplying steam to heat the foam beads, and then the mold is cooled to take out the desired foam casting model from the mold. molding method.