JPH0367604B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a casting mold that eliminates the influence of curing shrinkage on cast products.

[Conventional technology]

FIG. 4 is a front view showing a conventional mold, and FIG. 5 is a sectional view taken along the - line in FIG. 4. 1 is a main body made of aluminum or the like, 2 is a supply port, 3 is an internal conductor integrated with a thermosetting resin 4 to be described later, 4 is a thermosetting resin, and 5 is a heater as a heat source.

FIG. 6 shows the temperature rise of the thermosetting resin in the mold according to the conventional mold. F ₃ is the temperature change in the area where the heater is attached, and F ₄ is the temperature change in the area where the heater is not attached. t ₀ is the room temperature around the mold, t ₁ is the temperature at the completion of injection, and t ₂ is the predetermined curing temperature.

Thermosetting resins used for manufacturing cast products generally undergo shrinkage during curing. At this time, it is known that when local shrinkage occurs, it can lead to fatal defects such as formation of cavities on the surface of the cast product and, in some cases, the occurrence of cracks.

One way to prevent this is to apply a temperature difference to the mold to create a difference in the reaction rate of the thermosetting resin inside the mold, so that the thermosetting resin in the mold is sequentially cured and shrunk, and the shrinkage is replenished from the replenishment port. It is being

Therefore, in the past, a heater 5 was installed in a part of the main body 1.
Attach a heat source such as and heat it in a room temperature t ₀ atmosphere.
A temperature difference F ₃ −F ₄ was generated in the mold.

[Problem that the invention seeks to solve]

In the conventional method, it is expensive and time-consuming to attach a heat source to each mold, and the mold structure becomes complicated. Furthermore, since the temperature difference during curing occurs until the curing is completed, there are problems such as the degree of curing of the cured product itself is different and the homogeneity is impaired.

This invention was made to solve the above-mentioned problems, and aims to eliminate the need for a heat source and to obtain a cured product with a uniform degree of hardening.

[Means for solving problems]

In the casting mold according to the present invention, the heat source of the mold is set to the heating furnace atmosphere temperature _t2 , and in order to prevent local curing shrinkage, curing proceeds sequentially from the part farthest from the thermosetting resin supply port. This is to differentiate the heat absorption rate of the mold. Specifically, the surface may be blackened, or it may be constructed from members with different thermal conductivities.

[Effect]

In the casting mold of the present invention, by increasing the absorption rate of a part of the surface of the main body, a difference is created in the reaction rate of the thermosetting resin in the mold, and the casting mold is cured and shrunk sequentially. Replenish the amount from the supply port. Since the heating furnace temperature is constant at t ₂ , a uniform degree of curing of the cured product itself can be obtained in the end.

[Embodiments of the invention]

Embodiments of the invention will be described below with reference to the drawings. FIG. 1 is a front view showing a casting mold according to the present invention, and FIG. 2 is a sectional view taken along the - line in FIG. 1.

In the figure, 6 is a blackened part that has been blackened by coloring with dye, painting with paint, formation of metal oxide, etc., and the flow path of thermosetting resin 4 starts from the point farthest from the supply port 2. has been processed to a predetermined point. FIG. 3 shows the temperature rise of the thermosetting resin in the mold according to the present invention, where _t2 is the heating furnace temperature around the mold, which is the conventional curing temperature. F ₁ is a temperature rise in the blackened portion 6, and F ₂ is a temperature rise in a portion that has not been blackened.

Next, the effect will be explained. In Figures 1 to 3, the mold injected with thermosetting resin (mold temperature
t ₁ °C) into a heating furnace (heating furnace atmosphere temperature t ₂ °C).

Since t ₂ > t ₁ , the mold absorbs heat from the heating furnace atmosphere and its temperature increases. At this time, the ambient temperature
If the amount of absorbed heat reaching the mold from t ₂ is Ekcal/h per unit area of the mold, the absorption rate of the mold material is a, and the surface area of the mold is Am ² , then the total amount of absorbed heat Q of the mold is:
Q=E・a・Akcal/h. The absorption rate a is the absorption rate of a blackbody with a maximum value of 1. The roughness of the aluminum used in the mold is 0.06. By blackening part of this surface, the absorption rate can be increased.
Improved to about 0.9.

In this way, by increasing the absorption rate, the temperature rise of the thermosetting resin in the mold of the blackened part 6 is reduced to F ₁
The temperature rise is larger than that of the aluminum mold part ( _F2) . That is, the same effect as the conventional method of causing a difference in the reaction rate of the internal thermosetting resin can be obtained, and curing shrinkage occurs sequentially. Then, the shrinkage amount is replenished from the supply port. Furthermore, since the entire mold reaches a constant temperature _t2 after a predetermined period of time, the degree of hardening of the cured product itself can be more homogeneous than in conventional methods.

In the embodiments described above, the support part into which the internal conductor 3 is fitted is made of aluminum, which is soft and easily worn out, so iron or the like is sometimes used by inserting it into the main body 1. In this case, since the thermal conductivity of iron is lower than that of aluminum, the reaction rate of the thermosetting resin in contact with this portion is delayed and local shrinkage occurs, which tends to cause poor appearance. In this case as well, this problem can be solved by applying the present invention and blackening the surface of the iron.

Further, in the above embodiments, differences in heat absorption rate were provided by surface treatment, but differences in thermal conductivity may also be utilized.

Furthermore, similar effects can be expected by utilizing the difference in heat capacity of the bodies that make up the mold.

〔Effect of the invention〕

As described above, according to the present invention, by creating a difference in the curing speed of the thermosetting resin in the mold, local shrinkage can be prevented, and the degree of curing of the cured product itself is uniform. It has the effect of getting something.

[Brief explanation of drawings]

FIG. 1 is a front view of a mold according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the - line in FIG. 1, and FIG. 3 is a temperature rise of the thermosetting resin in the mold according to FIG. 1. 4 is a front view showing a conventional casting mold, FIG. 5 is a sectional view taken along the - line in FIG. 4, and FIG. 6 is a thermosetting inside mold according to FIG. 4. It is an explanatory view showing temperature rise of resin. In the figure, 1 is a main body, 2 is a supply port, 4 is a thermosetting resin, and 6 is a blackened part. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A thermosetting resin is injected, heated at a predetermined temperature, and cured while replenishing the thermosetting resin, such that the heat absorption rate is lower on the side closer to the replenishment port. A casting mold characterized by the following: 2. A casting mold according to claim 1, characterized in that the flow path of the thermosetting resin is blackened from the farthest point from the replenishment port to a predetermined point toward the replenishment port. Type. 3. A casting mold according to claim 1, characterized in that the casting mold is treated so that the degree of blackness gradually decreases from the point farthest from the replenishment port toward the replenishment port. 4. A casting mold according to claim 1, characterized in that the mold is configured such that the heat capacity increases sequentially from the point farthest from the replenishment port toward the replenishment port. 5 In a device that injects thermosetting resin and heats it at a predetermined temperature, and cures while replenishing the thermosetting resin, the side closer to the replenishment port is made of a member whose thermal conductivity is lower than that of the side farther away. A casting mold featuring: 6. For casting, in which a thermosetting resin is injected, heated at a predetermined temperature, and cured while replenishing the thermosetting resin, the surface farther from the vicinity of the replenishment port is blackened. Mold.