JPH024771Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an injection mold for use in an injection molding device such as a die casting machine or an injection molding machine.

Die casting has been widely used as a method for mass producing products with precise shapes.

However, die casting requires high speed, high pressure,
Because molding is performed by rapid cooling, the product tends to contain many pinholes and shrinkage cavities. In recent years, especially
There is an increasing demand for healthy die-cast products with no cavities inside the product.
The air inside the mold is discharged using a decompression method to prevent pinholes from forming.

However, even with the above method, it has not been possible to solve the problem of shrinkage cavities that occur during solidification of the product.

Shrinkage cavities occur due to shrinkage during solidification of the product, and can be prevented by using a riser, but in order to ensure that the effect of the riser reaches the end of the product, it is important to adjust the shape of the product. This is not possible depending on the situation.

Generally, the product consists of a thick wall part and a thin wall part.
In conventional mold cooling using only cooling water,
The thin-walled portion solidifies earlier than the thick-walled portion, and because of the solidified thin-walled portion, the boiling water does not work on areas beyond the thin-walled portion.

The present invention is designed to maintain the mold temperature in areas where the injected molten metal should be relatively delayed in solidification, such as thin-walled parts, at a higher temperature than in areas where it is desired to solidify relatively quickly. This is an injection mold that enables the riser effect to be increased to

The present invention will be explained in detail below with reference to embodiments shown in the drawings.

FIG. 1 is an example in which a high-temperature section and a low-temperature section are partially realized by inserting a heat insulating material into the dividing surface of the nest and flowing cooling water and a heat medium.

In FIG. 1, 1 is a holding die on the fixed side, 2 is a holding die on the movable side, 3 is a product thin-walled part nest provided, for example, on the outer surface of the center part of the cavity 12, and 4 is a die for the upper and lower parts of the cavity 12, for example. 5 is a product thick wall part nest provided on the outer surface part, 5 is a product thin wall part 6, 6a in the center of the cavity 12, for example, is a product thick wall part in the upper and lower part of the cavity 12, and 7 is a product thin wall part in the nest 3. Part 5
8 is a product thick wall cooling water passage provided in the insert 4; 8a is a product thin wall cooling water passage provided in the insert 3; 9 is a product thin wall 5 insert 3 and others. 10 is a heat insulating material inserted into the split surface between the nest 3 and the holding dies 1 and 2;
1 indicates an injection sleeve.

As shown in FIG. 1, in the case of a product shape that has a product thick part 6 at the back (in the figure, above) of the product thin part 5 when viewed from the casting direction, the product thin part 5
Solidification is completed earlier than in the product thick-walled parts 6 and 6a. For this reason, the rising water effect is
, and does not reach the thick part 6 of the product. Then, the product thick-walled portion 6 which completes solidification without the riser effect generates shrinkage cavities inside due to its volumetric contraction.

Therefore, in order to ensure that the boiling water effect reaches the end of the product and to obtain a healthy product without shrinkage cavities, do not use a heat medium such as hot oil in the heat medium passage 7 until the solidification of the thick part 6 of the product is completed. The temperature of the product thin wall portion 5 is maintained at a relatively high temperature state, and at the same time the solidification of the product thick wall portion 6 is completed, the flow of the heat medium into the heat medium passage 7 is stopped, and the product thin wall cooling water passage 8a is Cooling water is flowed through to solidify the thin part 5 of the product at once. In addition, in the thin product part 5, the switching of the operation of stopping the flow of the heat medium in the heat medium passage 7 and starting the flow of cooling water to the product thin part cooling water passage 8a depends on the shape, size, material, and injection process of the injection product. Although it varies depending on the temperature, etc., this may be done based on the state of temperature change inside the insert 4 near the cavity surface in the thick part 6 of the product at the back, or based on the elapsed time from the start of injection. You can do it.

In the present invention, the nests 3 and 4 are made of a copper-based material with excellent thermal conductivity, instead of using iron-based material with poor thermal conductivity as in the conventional case. As a result, it has become possible to obtain good thermal responsiveness by performing the above-described control.

As a copper-based material with excellent thermal conductivity, that is, a copper-based alloy mainly composed of copper, for example, 0.01 to 5 wt%
Using a Cu-AI solid solution alloy consisting of AI and the remainder being Cu, this alloy is divided into Cu powder: Cu ₂ O powder: AI ₂ O ₃ powder =
1:(0.8 to 1.2):(0.8 to 1.5) and heated in a vacuum of 10 _-1 to _{10 -7} Torr.
By heating and holding at 800 to 1000℃ for 1 to 30 hours, O ₂ naturally enters the Cu-AI solid solution alloy, internally oxidizing the surface layer of this alloy, and forming fine and uniform AI ₂ O ₃ particles. A copper-based alloy was used in which a dispersed and precipitated oxide layer was formed on the surface layer of the alloy. in this way,
By internal oxidation, an oxide layer in which AI ₂ O ₃ particles are dispersed and precipitated is formed on the surface layer of a copper-based alloy.It has excellent thermal conductivity and has significantly higher high-temperature strength than pure copper. This material is very suitable as a mold material for castings such as die casting. Of course, the surfaces of the nests 3 and 4 made of a copper-based alloy with an oxide layer formed therein form part of the surface of the cavity 12.

In addition, the product thin-walled part nest 3 that needs to be kept at a relatively high temperature, the product thick-walled part nested 4 that needs to be kept at a relatively low temperature, and the holding dies 1 and 2.
Insulating materials 9 and 10 were inserted into the surfaces of the nest 3 where they are in contact with other parts, respectively, in order to prevent heat conduction to the parts.

When placing the nests 3, 4 and heat insulators 9, 10 in the mold, separately manufactured nests 3, 4 and heat insulators 9,
10 may be fitted into the recesses of the holdings 1 and 2, but if the mold is manufactured by casting, the heat insulating materials 9 and 10 may be inserted when the holdings 1 and 2 of the mold are cast. This can be done by placing both the nests 3 and 4 in predetermined positions, or by casting only the heat insulating material 10 installed in the place where you want to insulate, and then placing the heat insulating material 9 on each split surface. Holding nests 3 and 4 with
It may also be done by fitting it into a recess etc.

FIG. 2 shows the surface temperature distribution state of the nests 3 and 4 in a steady state when a heat medium is passed through the heat medium passage 7 and cooling water is passed through the product thick wall cooling water passage 8.

In the diagram in Figure 2, the dashed line is the insulation material 9, 1
The temperature distribution when there is no zero is shown, and the solid line shows the temperature distribution when the heat insulating materials 9 and 10 are inserted. Due to the heat insulating effect of the heat insulating materials 9 and 10, it was realized that the product thin-wall part nest 3 can maintain a sufficiently high temperature compared to the product thick-wall part nest 4. That is, the product thin wall portion 5 of the cavity 12 could be kept at a sufficiently high temperature during injection.

In this way, in this invention, by appropriately controlling the mold temperature separately for the high-temperature part and the low-temperature part, it is possible to make the rising water effect reach all the way to the end, and to cast a healthy product without shrinkage cavities. Can be done.

Of course, by appropriately controlling the mold temperature,
If injection is performed while the thin part of the product is slow to solidify and the thick part of the product following the thin part is kept at high temperature,
The injection pressure that is transmitted through the molten metal in the thin part of the product does not decrease and is sufficiently transmitted to the molten metal in the thick part of the product that follows the thin part of the product, so the rising effect reaches the end.

In addition, once the rising water effect has sufficiently worked, the thin part of the product can be cooled, and the injected product can be cooled easily and relatively quickly, making it easier to take out the product.

In addition, a nest through which a heat medium or cooling water flows is provided on the inner surface of the mold, and this nest is made of a material with good thermal conductivity, especially a copper-based alloy, and is made of an AI by internal oxidation. ₂ O ₃ particles are finely and uniformly dispersed and precipitated to form an oxide layer on the surface layer of the copper-based alloy, so it has excellent thermal conductivity and satisfactory strength, and the mold temperature can be easily controlled. Furthermore, the mold releasability is good, and the injection product can be easily released from the mold and taken out without paying much attention to the application of the mold release agent.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a longitudinal sectional view, and FIG. 2 is an explanatory diagram showing the temperature distribution state on the surface of the mold. DESCRIPTION OF SYMBOLS 1, 2... Holding die, 3, 4... Nest, 5... Product thin wall part, 6... Product thick wall part, 7... Heat medium passage, 8... Cooling water passage, 9, 10... Heat insulation material, 12
... Cavity.

Claims (1)

[Scope of utility model registration request] A nest that can partially control the temperature is provided on the inner surface of the mold around the product thin wall part and the product thick wall part of the mold cavity, and a heat insulating material is placed on the dividing surface between the nests, and A heat insulating material is placed on the dividing surface between the insert and the mold body, and the insert is made of a copper-based alloy surface layer with an oxide layer in which AI ₂ O ₃ particles are dispersed and precipitated. An injection mold that has a part that can perform both heating and cooling in the nest around the thin part, and a cooling medium passage in the nest part around the thick part of the product.