JP2552376B2 - Manufacturing method of hollow disappearance model - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a method for manufacturing a hollow vanishing model.

(Prior Art) One method of making a casting is to use a so-called vanishing model that can be used only once. For example, in the full-mold method, a model is made of expandable polystyrene (hereinafter abbreviated as beads), molten metal is injected and burned and vaporized while it is buried in foundry sand, and the shape corresponding to this is substituted for the model. Make a casting. As described above, the model used in the full-mold method burns and disappears due to the heat of the molten metal, and therefore can be used only once and is counted as one of the disappeared models.

Taking this full molding method as an example, as a vanishing model used therein, for example, when manufacturing a hollow hollow vanishing model 40 having a curved cylindrical shape as shown in FIG. 14, conventionally, the central axis C of the curved core 41 is used. _{The second} which divides the model 40 into two in the plane containing ₂
The two parts 40a and 40b shown in FIG. 13 are separately molded by using respective molds, and the two parts 40a and 40b are bonded with an adhesive.

That is, the mold 42 shown in FIG. 11 corresponds to the part 40 shown in FIG.
Two molds for molding a, which mold the part 40a inside the outer frame 43, that is, an outer main mold 44 and an inner core mold.
45 is incorporated, and the lid 46 is placed as shown in FIG. 12 to complete the mold matching. A space (cavity) 47 in the shape of the part 40a is formed between the main mold 44 and the core mold 45. A bead injection device 48 is connected to the main mold 44,
When the rod 49 retracts and the valve 50 opens the bead outlet 51,
Pre-expanded beads are injected and filled into the cavity 47 from the bead outlet 51. At this time, the air flow that blows out the beads passes through a large number of vent holes 52 provided in the respective molds 44 and 45, and passes through two spaces 53 and 54 in the outer frame 43, and spaces 53 and 54, respectively.
The air is exhausted through the openings 55 and 56 communicating with the. Then rod 49
When the valve 50 closes the bead outlet 51 by advancing, the steam is blown into the space 53 from the one opening 55, the beads in the cavity 47 are steam-heated through the mold 44, and the part 40a is foam-molded. It At that time, the steam is sucked and exhausted through the vent hole 52, the other space 54, and the opening 56. Cooling lid 46
Remove the mold and take out the foam-molded part 40a. Similarly, the other part 40b is also foam-molded using a mold for molding the part 40b. The two parts 40a, 40b thus obtained are bonded and integrated with an adhesive.

(Problems to be Solved by the Invention) As described above, in the above-described conventional technique, when manufacturing a hollow disappearance model having a curved hollow, it is difficult to remove the core for molding the curved hollow after molding. Due to this, it is difficult to integrally mold a curved hollow model.Therefore, such a hollow model is divided into at least two parts, each part is molded separately in each mold, and then each part is bonded with an adhesive. It had to be integrated.

As a result, taking the hollow disappearance model shown in FIG. 14 as an example, in order to join two separately molded parts 40a and 40b with an adhesive, the adhesive applied to the joint surface 57 of each part 40a and 40b. The agent tends to stick out to the surface of the model 40 at the time of joining, and burrs tend to be generated on the surface of the model 40 along the joining surface 57. In addition, in order to finish the hollow inner surface shape after joining smoothly, each part 40
A high dimensional accuracy is required for the dimensions of the joint surface 57 of a and 40b, but it is difficult to achieve such high dimensional accuracy because each part 40a and 40b is molded in a separate mold, and the problem of burrs mentioned above is also added. Therefore, it is difficult to secure a smooth inner surface shape of the core 41. Furthermore, the fact that a dedicated mold for molding each of the parts 40a, 40b is required is also a problem in terms of an increase in the number of steps and costs.

The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a method of manufacturing a hollow vanishing model capable of integrally molding even a curved hollow vanishing model.

[Means for Solving the Problems] (Means for Solving the Problems) The present invention for achieving the above-mentioned object is achieved by using a shape memory alloy for a core forming a hollow of a hollow disappearance model in which the hollow is curved. The core is coated with a heat-resistant coating material for smoothing the hollow inner surface of the hollow disappearance model, and the core coated with the coating material After incorporating the child into the main mold for molding the external shape of the hollow disappearance model, injecting a foaming resin material and heating to foam-mold the hollow disappearance model, deforming the core, and taking out. Is characterized by.

(Operation) In this way, the hollow disappearance model can be easily removed by foaming the hollow disappearance model and then deforming the shape-memorized core, so that it becomes possible to integrally form a curved hollow disappearance model. In combination with the use of the covering material, the hollow inner surface shape can be finished more smoothly.

(Example) Hereinafter, one example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a manufacturing process diagram showing an outline of a manufacturing process of a hollow vanishing model by a method of manufacturing a hollow vanishing model according to an embodiment of the present invention, and exemplifying a manufacturing process of a vanishing model used in a full molding method. There is.

In the description of this manufacturing process, the case of manufacturing a hollow vanishing model used for casting the automobile exhaust manifold 1 having the shape shown in FIG. 2 will be described as an example. The automobile exhaust manifold 1 has a curved cylindrical hollow 2 as shown in the figure, and the hollow vanishing model to be manufactured has the same shape as the automobile exhaust manifold 1. So this exhaust manifold 1 for automobiles
The hollow disappearance model for casting is numbered 1a.
The curved hollow of 1a will be numbered 2a.

First, regarding the molding of the core for molding the curved hollow 2a of the hollow disappearance model 1a, a thin plate material 3 of TiNi shape memory alloy having a stepwise cross section S as shown in FIG. 3 is prepared as a core material. . Then, the thin plate material 3 of this TiNi shape memory alloy is subjected to shape memory treatment, and as shown in FIG. 4, the thin plate material 3 is spirally wound to form a core 4 having the same shape as the hollow 2a shape of the hollow disappearance model 1a. make. A hollow 5 is formed inside the core 4, and the hollow 5 communicates with the outside through a fitting gap 6 of the thin plate member 3. Incidentally, FIG. 5 shows the core 4 shown in FIG.
FIG. 9 is a partial cross-sectional view of the center axis C ₁ of FIG.

In order to smooth the inner surface of the hollow 2a of the hollow disappearance model 1a, the core 4 molded by performing the shape memory process in this way has a coating material on the outer surface of the core 4 as shown in FIG. A heat resistant urethane film sheet 7 is attached. This film sheet 7 has a high temperature (about 110
C.), and the sticking method is preferably vacuum sticking in order to eliminate the gap between the film sheet 7 and the core 4 as much as possible. This film sheet 7
Has a large number of fine holes 8 having a diameter of about 0.1 mm. Therefore, even if the film sheet 7 is stuck to the core 4, the fine holes 8 of the film sheet 7 and the core 4 make a gap between them. The communication state with the outside of the hollow 5 of 4 is maintained (see FIG. 7).
It should be noted that the core 4 is molded in a size modified by the thickness of the film sheet 7.

In this embodiment, the core molding process is completed when the film sheet 7 is attached to the core 4, and the core is not assembled.

6 is a schematic vertical cross-sectional view of the hollow disappearance model 1a molding die, FIG. 7 is a partially enlarged view of FIG. 6, and FIG. 8 is a schematic cross-sectional view of the hollow disappearance model 1a molding die, In each case, beads that are foaming resin material (foaming polystyrene) in the cavity
Is filled and foam-molded.

As shown in FIG. 8, the mold 10 forming the hollow disappearance model 1a is composed of a lower mold 11 and an upper mold 12, and is a main mold for molding the outer shape of the hollow disappearance model 1a inside the outer frames 11a and 12a, respectively. The molds 11b and 12b constituting the above are incorporated. This mold 11b, 12b
A large number of vent holes 13 are provided in the. Further, the internal space 11c of the lower mold 11 and the internal space 12c of the upper mold 12 communicate with each other through the opening 14.

The core 4 covered with the film sheet 7 is housed in the lower mold 11, and then the upper mold 12 is matched to complete the molding mold 10 of the hollow vanishing model 1a as shown in FIG.
At this time, a cavity 15 having the shape of the hollow disappearance model 1a is formed between the main molds 11b and 12b and the core 4 (strictly speaking, the film sheet 7 attached to the core 4). As shown in FIG. 6, lids 16 are attached to both ends of the core 4 (only one is shown), and an opening 17 is provided in either one of the lids 16. Further, an opening 18 is provided in at least one of the outer frames 11a and 12a.

As shown in FIG. 6, a bead injection device 19 is connected to the main mold 11b (or 12b), and the rod 20 is retracted so that the valve 21
When the bead outlet 22 is opened, the beads pre-expanded from the bead outlet 22 are injected and filled into the cavity 15. At that time, the airflow from which the beads are blown out from the vent hole 13 through the internal spaces 11c and 12c through the opening 18 or from the fine holes 8 of the film sheet 7 and the fitting gap 6 of the core 4 through the hollow 5 of the core 4. The gas is exhausted through the opening 17. Then rod
When 20 moves forward and valve 21 closes bead outlet 22, opening 18
110 ° C steam is blown into the internal spaces 11c and 12c from the main mold 1
The beads in the cavity 15 are heated via 1b and 12b.
By heating the beads with steam, the hollow disappearance model 1a is foam-molded in the cavity 15. During this time, the steam blown into the internal spaces 11c and 12c is the fine holes 8 of the film sheet 7 and the core 4.
It is sucked and exhausted from the fitting gap 6 through the hollow 5 of the core 4 to the outside through the opening 17.

Then cool the mold 10. As the mold 10 is cooled, the spiral core 4 is sufficiently cooled, and as shown in FIG.
Pull out one end from the mold 10, pull out in the direction of the arrow in the figure, and take out. At this time, the heat resistant film sheet 7 attached to the outer surface of the core 4 is also taken out while being destroyed along with the deformation of the core 4. Then, the mold is removed to take out the foam disappeared hollow disappearance model 1a.

The core 4 taken out while being deformed is subjected to a shape recovery treatment and reused after removing the film sheet 7 attached to the outer surface thereof. That is, the taken-out core 4 is heated to restore its shape to the same shape as the hollow 2a shape of the hollow disappearance model 1a that is spirally wound.

Further, FIG. 9 shows a piping elbow, and in manufacturing the hollow disappearance model 30a used for casting the piping elbow 30 having the shape shown in the figure, for example, a core 32 shown in FIG. 10 is used. Then, the hollow 31a of the hollow disappearance model 30a corresponding to the curved core 31 of the pipe elbow 30 is formed.

The hollow 32 shown in FIG. 10 uses a CuZnAl shape memory alloy as a core material, and a shape-meshing process is applied to the knitted mesh to form a hollow 31a of the hollow disappearance model 30a, as shown in FIG. The shape is stored in the same shape as the shape.
This hollow 32 has a core 33 formed inside.
The reference numeral 33 communicates with the outside through the mesh of the mesh core 31a.
Further, a heat-resistant cloth 34 made of polyester-based thread is attached to the outer surface of the mesh core 31a, and even if the cloth 34 is attached, the outside of the core 33 of the core 31a is exposed through the gap. Communication with is maintained.

Since the subsequent manufacturing process of the hollow disappearance model 30a is the same as the manufacturing process of the hollow disappearance model 1a described above, the description thereof will be omitted.

Therefore, according to this embodiment, the shape memory treatment is performed on the TiNi shape memory alloy or the CuZnAl shape memory alloy, and the core 4,
Since 32 is molded, it becomes possible to integrally mold the hollow disappearance models 1a and 30a in which the cores 2a and 31a are curved. Therefore, in combination with coating the outer surfaces of the cores 4 and 32 with the heat-resistant film sheet 7 or the cloth 34, the inner surfaces of the hollows 2a and 31a of the hollow disappearance models 1a and 30a are finished more smoothly. It has become possible.

Further, according to the present embodiment, one mold 10 is required to mold the hollow disappearance models 1a and 30a, and the deformed and taken out cores 4 and 32 are repeatedly used if shape recovery processing is performed. Therefore, it is advantageous in terms of the number of steps and cost as compared with the conventional manufacturing method.

In the present embodiment, the shape memory of TiNi shape memory alloy and the shape of CuZnAl shape memory alloy are stored in a spiral pipe shape and a wire mesh shape, respectively. Whether it is easy to memorize the shape of the hollow shape of the hollow disappearance model considering the characteristics of the shape memory alloy,
It is good to decide in consideration of whether it is easy to take out after cooling.

Further, in this embodiment, a heat-resistant urethane-based film sheet 7 having a large number of fine holes 8 provided in a spiral pipe-shaped core 4 and a heat-resistant polyester-based yarn in a wire mesh-shaped hollow 32 are used. However, this combination is not essential and the reverse combination may be used. Furthermore, a coating material other than the above may be applied as long as it is a material capable of withstanding the temperature at the time of foam molding and has a function of smoothing the hollow inner surface of the hollow disappearance model.

Further, in the present embodiment, the production of the disappearance model used in the full molding method is illustrated, but the present invention is not limited to this, and the present invention can be applied to the case where the disappearance model is manufactured by using a bark or the like. it can. Further, it is needless to say that the present invention can be applied not only to the case where the hollow disappearance model has a curved hollow as in the present embodiment, but also to the manufacture of the hollow disappearance model having a hollow without a curve.

[Effects of the Invention] As is clear from the above description, according to the present invention,
Since the core is made of a shape memory alloy, it becomes possible to integrally form a hollow disappearance model in which the hollow is curved. Therefore, in combination with the use of the covering material, the hollow inner surface shape of the hollow disappearance model can be finished more smoothly.

Further, according to the present invention, in addition to requiring only one mold for molding the hollow disappearance model, the deformed and taken out core can be repeatedly used if subjected to a shape recovery treatment. It is also advantageous in terms of.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram showing an outline of a manufacturing process of a hollow vanishing model by a method of manufacturing a hollow vanishing model according to an embodiment of the present invention, FIG. 2 is a perspective view of an automobile exhaust manifold, and FIG. Fig. 2 is a view showing a core material for molding the hollow of the hollow disappearance model for manufacturing the exhaust manifold shown in Fig. 4, Fig. 4 is a view showing a core made of the core material shown in Fig. 3, and Fig. 5 is FIG. 4 is a partial cross-sectional view, FIG. 6 is a schematic vertical cross-sectional view of the hollow disappearance model molding die in which the core shown in FIG. 4 is stored, and FIG. 7 is a partially enlarged view of FIG. FIG. 8 is a schematic cross-sectional view of the hollow vanishing model molding die in which the core shown in FIG. 4 is stored, FIG. 9 is a perspective view of an elbow for piping, and FIG. 10 is manufacturing of an elbow for piping shown in FIG. FIG. 11 is a view showing a core for molding a hollow of a hollow disappearance model for use in FIGS. 11 to 14, and is a view for explaining the prior art. 1a, 30a ... Hollow vanishing model, 2a, 31a ... Hollow model, 4, 32
... core, 7 ... film sheet (covering material), 34 ... cloth (covering material), 11b, 12b ... main mold, 15 ... cavity, 19 ... bead injection device (foaming resin material injection device).

Claims (1)

(57) [Claims] 1. A core for forming a hollow of a hollow vanishing model having a curved hollow is molded by applying a shape memory treatment to the shape memory alloy using a shape memory alloy, and the outer surface of the core. Then, a heat-resistant coating material for smoothing the hollow inner surface of the hollow disappearance model is coated, and the core coated with this coating material is incorporated into a main mold for molding the outer shape of the hollow disappearance model and then foamed. A method for manufacturing a hollow disappearance model, characterized in that a hollow resin disappearance model is obtained by injecting and heating a resinous material to foam-mold the hollow disappearance model and deforming the core.