JPH0464301B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a foamed synthetic resin fugitive model material used in a full mold casting method, particularly a method for molding a thick material.

(Prior art) Foamed synthetic resin, such as foamed polystyrene, which is used as a model material used in the full mold casting method, is made by impregnating polystyrene, which is made by polymerizing styrene monomer made from benzene and styrene with a foaming agent. is heated to cause primary foaming, which is then made into beads. These beads are further foamed and molded for use, but as a model manufacturing method, the beads must be of a certain size (e.g. 1800×
There are two methods: one is to cut out the required shape from a foam-molded block (900 x 400mm) and assemble it in the same way as with wood, and the other is to foam-mold using a mold with the same shape as casting.

The subject of the present invention is the case of molding the former block, but as a means for secondary foaming using beads, it is possible to Insert the appropriate amount of beads,
By blowing heated gas into the inside of the mold from the outside and heating the mold from the outside, beads are foamed and a foam-molded model material (block) is obtained.

(Problems to be Solved by the Invention) In the molding die, the surface portion (20 to 30 mm) of the foam that is in contact with the inner surface of the mold quickly undergoes secondary foaming and is thermally fused, making the surface portion heat-insulating. As a result, heat from the outside does not reach the center of the mold sufficiently.
Therefore, sufficient foaming and thermal fusion does not occur in the center, resulting in a crunchy state in which the beads to foamed particles are not fused.

The model material (block) thus formed is
There is no particular problem when only the surface is used, but as explained earlier, when creating a model by cutting or carving the block into the required shape,
During the cutting process, some of the foamed particles may fall apart, or even if they do not separate, there are many open voids between the foamed particles on the surface of the cut surface. Another drawback is that the molding agent and moisture enter the open cavity, and these invaders react with the molten metal that has been cast, creating numerous small pores on the surface of the casting.

(Means for Solving the Problems) The present invention solves the above-mentioned problems and provides an excellent product in which secondary foaming is sufficiently completed to the inside of the material block and the foam particles are thermally fused to each other. As a molding method to achieve this purpose, a large number of small holes bored in the central area of at least one outer wall of a mold having a large number of heated gas injection holes are used to form a large number of needle-shaped holes provided in a movable plate. The nozzle is moved toward the center of the mold by moving the moving plate toward the mold, and heated gas is blown through the nozzle and gas blowing hole to cause secondary foaming to the beads in the mold. Then, by moving the movable plate outward from the mold while continuing to blow heated gas from the gas blowing hole, all the needle nozzles exit from the mold almost simultaneously, and the needle nozzles A structure was adopted in which the needle holes formed in the molded foam were closed by the subsequent expansion of the secondary foam.

(Function) The foamed polystyrene beads housed in the molding mold are exposed to heated gas from the outside of the mold, from the heating gas blowing holes 3 and 6 provided in large numbers on the top plate 5 and the bottom plate 2, and in large numbers on the moving plate. A needle-like nozzle 15 provided
Secondary foaming is performed by heating gas blown in from the heating gas. The needle-like nozzle 15 is located in the center area of the mold body 1, and the tip of the nozzle 15 penetrates into the center area, so the heated gas blown from the nozzle 15 causes the inside of the mold body 1 to be heated. The beads are heated from the center area, and further heated by the external surface of the mold and the heated gas injected from the heated gas blowing holes 3 and 6 of the top plate 5 and the bottom plate 2, so that the beads undergo sufficient secondary foaming, and the foamed particles are thermally fused to each other. wear. Taking this situation into consideration, all the needle nozzles 15 are moved out of the mold almost simultaneously by moving the movable plate outward from the mold while continuing to blow heated gas through the gas blowing hole. The needle hole formed by the nozzle 15 is disappeared and sealed by the subsequent expansion of the secondary foam by the heated gas continuously blown from the gas blowing holes 3 and 6. At this time, all the needle nozzles 15 can be exited at approximately the same time by moving the movable plate to the outside of the mold, so that the heating conditions inside the block become approximately uniform, and the needle nozzles 15 can be moved out of the mold. Coupled with the small diameter of the needle hole, not only will no nozzle marks remain anywhere inside the block, but
A block that is uniformly foamed throughout is obtained.

(Example) An example of the molding method of the present invention will be described with reference to the drawings of FIGS. 1 to 5.

FIG. 1 is a cross-sectional view of a molding die used in the present invention, FIG. 2 is a cross-sectional view taken along the - line in FIG.
The figure is a plan view of FIG. 1. In these figures, 1 is a box-shaped mold body with an open top, and its bottom 2
A large number of heated gas blowing holes 3 are provided over the entire surface of the bottom portion 2, and support stands 4 are fixed in parallel on both sides of the lower surface of the bottom portion 2. Reference numeral 5 denotes a top plate that closes the opening of the main body 1, and this top plate 5 also has a large number of heated gas blowing holes 6 and a large number of small holes 7 through which heated gas blowing nozzles (described later) pass through the top plate 5.
The main body 1 and the top plate 5 are fastened and fixed by using brackets 4', 4' protruding outward from the support stands 4, 4 of the main body 1 and protruding outward from the top plate 5. Connect the installed brackets 5' and 5' with bolt 8 and nut 9.
This is done using fixtures such as.

The top plate 5 is further provided with stoppers 10 near the four corners of its upper surface, and guide posts 11 are erected near the four corners, respectively.

Reference numeral 12 denotes an elevating plate which is a movable plate having approximately the same shape and size as the top plate 5, and this elevating plate 12
1 and can move up and down freely. Also, on both sides of the upper surface of this elevating plate 12, there are operation handles 13, 1.
3 is fixed. On the other hand, the elevating plate 12 is further provided with a through hole 14 corresponding to the small hole 7 provided in the top plate 5, and a gas blowing nozzle 15 is inserted into this through hole 14.
The proximal end of is fixedly fitted. The nozzle 15 is a needle-shaped pipe with a diameter of about 2 mmφ, and its length is such that when the elevating plate 12 is at its lowest point and its lower surface abuts the stopper 10 on the top plate 5, the tip of the nozzle 15 is on the main body 1. It is desirable that it be located approximately in the center position in the height direction.

Next, a method of molding a model material using the above molding die will be explained. Stellene grains pre-foamed to the required expansion ratio of the calculated capacity are housed in the mold body 1. Next, a top plate 5 equipped with an elevating plate 12
is placed on the upper part of the mold main body 1, and the main body 1 and the top plate 5 are fastened and fixed using fixing devices with bolts 8 and nuts 9, as shown in FIG. At this time, the elevating plate 12 is
This is not the state shown in FIG. 2, but the state shown in FIG. 5, which is the lowest position. Although not shown in the drawings, if the entire mold is housed in a heating chamber and heated gas is blown into the heating chamber, the heated gas will flow through the blow hole 3 provided in the bottom 2 of the mold body 1 or the top plate 5. Heated gas is blown into the mold body 1 from the blowing hole 6, and further from the needle nozzle 15 provided on the lifting plate 12.
blown inside. Therefore, the pre-foamed foamed sterene particles in the mold body 1 are heated from both the outside and inside of the mold, further causing secondary foaming, and the inside of the mold body 1 is filled with foam, causing foaming. The grains are thermally fused to each other. Next, while observing this state, the elevator plate 12 is raised via the operating handle 13. At this time, the lifting limit of the lifting plate 12 is regulated by a stopper 16 provided at the upper part of the guide post 11, so that the entire lifting plate 12 does not come off accidentally. At this time, the needle hole of the needle nozzle 15 remains in the foam formed inside.
The heated gas continuously blown in from the gas blowing holes 3 and 6 causes the needle hole to disappear and close due to the subsequent expansion of the secondary foam. When the foaming in the mold is thus completed, the mold is cooled and cured, and then taken out from the heating chamber, bolts 8 and nuts 9 are removed, and the entire top plate 5 including the lifting plate 12 is moved to the mold body 1. One step of molding is completed by removing the model material, which is a foam block molded within the main body 1.

In the above embodiment, the needle nozzle 15 enters the inside of the mold body 1 from the top plate 5, but it may also enter from other side walls, bottom plate, etc. of the main body 1. Further, in the above embodiment, the elevating plate 12 moves toward the mold body 1, but conversely, the mold main body 1 may move relative to the elevating plate 12 (fixed at this time), or both may move toward the mold body 1. It can also be something that moves. Further, in the above embodiments, the heating chamber (not shown) is provided at a location separate from the mold, but it may be a heating device that includes the mold and surrounds the entire mold.

(Effects) The present invention allows a large number of needle nozzles provided on a movable plate to be connected to a large number of small holes drilled in the central area of at least one outer wall of a molding die provided with a large number of heated gas blowing holes.
By moving the movable plate toward the mold side, it enters into the center area of the mold, and blows heated gas through the nozzle and gas blowing hole to perform secondary foaming on the beads in the mold, Thereafter, by moving the movable plate outward from the mold while continuing to blow heated gas through the gas blowing hole, all the needle nozzles are exited from the mold almost simultaneously, and the foaming by the needle nozzles is completed. Since the needle holes formed in the body are sealed by the subsequent expansion of the secondary foam, the secondary foaming is suitably completed to the center even though the formed model material is thick. The foamed particles are well bonded to each other by heat. Furthermore, all the needle nozzles can be exited at almost the same time by moving the movable plate outward from the mold, so the heating conditions inside the block are also approximately uniform. Coupled with the small diameter of the holes, not only no nozzle marks remain anywhere inside the block, but also a block that is uniformly foamed to the inside. Therefore, when cutting out this foamed material (block) to make a model, the cut surface does not have many dents or openings, which makes painting and repair easier, and by extension castings made from this model. has the effect of producing a beautiful cast surface.

[Brief explanation of the drawing]

The drawings show a mold for carrying out the method of the present invention, FIG. 1 is a sectional view, FIG. 2 is a sectional view taken along the line -- in FIG. 1, FIG. 3 is a plan view of FIG. FIG. 5 is an enlarged sectional view of the main part showing the raised position of the lifting plate, and FIG. 5 is an enlarged sectional view of the main part showing the lowered position of the lifting plate. 1...Mold body, 3, 6...Heating gas blowing hole, 5...
Top plate, 7... Small hole provided in the top plate 5, 11... Guide post, 12... Lifting plate, 15... Needle nozzle.

Claims (1)

[Claims] 1. A large number of needle nozzles provided on a movable plate are moved from a large number of small holes drilled in at least one outer wall central area of a molding mold provided with a large number of heated gas blowing holes to the mold side. The heated gas is blown into the center area of the mold by blowing the heated gas through the nozzle and gas blowing hole to blow the beads into the mold.
Next foaming is performed, and then, while continuing to blow heated gas through the gas blowing hole, the movable plate is moved to the outside of the mold, so that all the needle nozzles are exited from the mold almost simultaneously. A method for molding a thick-walled foamed synthetic resin fugitive model material, characterized in that needle holes formed in a foam molded by a needle-like nozzle are closed by subsequent expansion of secondary foam.