JPH0242333B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The disclosed technology belongs to the technical field of preventing deformation during molding of injection molded products made of resin or the like.

<Summary of the gist> Accordingly, the present invention injects a molding material such as a resin material into a cavity of an injection mold from a runner of an injection molding device through a plurality of gates, and hardens the molding material within the cavity. This invention relates to a method for preventing deformation of an injection molded product during the process of molding, and in particular, the invention relates to a method for preventing deformation of an injection molded product during the process of molding. By providing a weir in a part of the cavity near the gate in the short direction, the flow resistance in the direction where the distance to the final destination of the molded material flowing through the cavity is short is increased, and the flow velocity is increased. This invention relates to a method for preventing deformation of an injection molded product by reducing the speed of the injection molded product.

<Prior Art> As is well known, injection molded products made of resin or the like are widely used in various industries due to the ability to freely set the product shape and high mass productivity.

In the molding of the injection molded product, as shown in Figs. 4 and 5, a molding material such as a resin material is passed from the runner 1 of the injection molding device to the cavity 4 of the injection mold through the gates 2, 2', 2''. , 4' and cured to manufacture the injection molded product 3. As a measure to prevent deformation of the injection molded product 3 during this curing process, the mold temperature of the injection mold is made uniform and deformation is expected. This is dealt with by using molds, etc.

<Problems to be Solved by the Invention> However, in the conventional method for preventing deformation of an injection molded product described above, when molding an injection molded product 3 having a shape as shown in FIG. There are differences in size and distance from each gate 2, 2', 2'' to each part inside the cavities 4, 4', and due to the asymmetrical shape, there is a difference in flow resistance inside the cavities 4, 4'. arise, each gate 2,
Compared to the flow velocity of the molding material flowing through the cavity 4, where the molding material reaches from each gate 2'2", the flow velocity of the molding material flowing through the cavity 4', where the molding material reaches from each gate 2' has a long distance. Lines 5, 5... (hereinafter abbreviated as flow fronts) connecting the arrival points of the molded material within the same time are shown in FIG.

As a result, in the curing process of the molding material, shrinkage differences occur in each part of the injection molded product 3, and when the mold is released, deformation occurs in the direction of the arrow shown in the figure, as shown in FIG. I'm leaving it behind.

In addition, in order to prevent deformation due to the above-mentioned shrinkage difference, it is necessary to provide a large number of gates 2 to connect the cavity 4 and the runner 1, which makes the injection molding apparatus complicated.

For example, as shown in the invention disclosed in Japanese Unexamined Patent Publication No. 54-129054, there is a technique in which a throttle is provided near the gate of the cavity to control the inflow speed of the molding material from the runner, but this type of prior art As stated in the specification, the purpose of this technology is to obtain a uniformly isotropic molded product, and the shearing force in the resin flow is increased.
The reheating and re-kneading of the resin is assisted and the resin pressure increases, which helps prevent the backflow of the resin from inside the cavity and prevents the occurrence of sink marks.It does not prevent the molded product from deforming due to differences in shrinkage after molding. There was a difference in technology.

The purpose of this invention is to solve the problem of preventing deformation of injection molded products based on the above-mentioned prior art, and to make the curing process uniform in each part of the injection molded product to eliminate molding defects. It is an object of the present invention to provide an excellent method for preventing deformation of injection molded products, which improves the reliability of the products and is beneficial to the fields in which molding technology is used in various manufacturing industries.

<Means for Solving the Problems> In order to solve the above-mentioned problems, the structure of the present invention, which is in accordance with the above-mentioned object and whose gist is the scope of the above-mentioned claims, is to move the molded material through a plurality of gates from the runner of an injection molding device. In this method, the molding material is injected into the cavity through the molding material to prevent deformation of the injection molded product while the molding material hardens, and the distance from the gate to the final destination of the molding material flowing from the gate is long. A weir is installed near the gate in the direction in which the distance to the final destination is shorter among the directions in which the distance to the final destination is shorter, and the flow velocity of the molded material in the direction in which the distance to the final destination of the molded material is shorter is determined. This is a method for preventing deformation of injection molded products by slowing down the speed.

<Function> Therefore, the direction in which the distance from the runner of the injection molding device to the final destination of the molding material flowing from the gate of the cavity of the injection mold through the plurality of gates to the final destination is longer or shorter is determined. The flow velocity of the molding material injected into the cavity is reduced by increasing the flow resistance by providing a weir or the like in the direction in which the molding material tends to flow, thereby reducing the flow velocity of the molding material in the direction where the distance is short. The speed in the short direction from the gate to the final destination is reduced relative to the speed in the direction where the distance is long, so that the arrival time of the molded material in the far distance part from the gate and the short distance part near the gate are almost the same. As a result, the curing speed of the molding material is equalized, there is no difference in shrinkage, preventing deformation of the injection molded product, and improving the finishing accuracy of the product.
It takes technical measures to improve reliability.

<Example> Next, an example of the present invention will be described below with reference to the drawings of FIGS. 1 to 3.

Incidentally, the same parts as in FIGS. 5 and 6 will be described with the same reference numerals.

FIG. 1 shows a cavity of an injection mold used in the present invention, and in this embodiment, a cavity 4 having a bent part in the center is used for manufacturing a resin molded product. is extended forward in the figure to form a vertical part, and the upper part of the vertical part in the figure is extended backward to form a cavity 4', and each cavity 4,
4' are formed to have the same thickness.

The runner 1 of the injection molding device is installed in the central bent part of the cavity 4, and the cavity 4
is connected to the runner 1 through gates 2 and 2' at the top of the figure, and connected to the runner 1 through gate 2'' at the bottom of the figure, and gate 2 = gate 2' In length, each gate 2,
The distance between the molding material 2' and the final reaching point of the molded material of the cavities 4 and 4' is longer in the latter.

Further, weirs 6, 6 are formed with a set width and a set height in the vicinity of the gates in the direction where the distance to the final arrival point of the molded material in the cavities 4, 4' is short, and that are oriented toward each gate 2, 2'. .

In the above configuration, when the molding material is injected from the runner 1 of the injection molding apparatus into the cavities 4, 4' through the respective gates 2, 2', 2'', each gate 2, 2' is injected into the cavity 4 at the upper part of the cavity 4 in the figure. Flow resistance is added to the molded material flowing into the cavity 4 by each weir 6, and the flow velocity of the molded material into the cavity 4 is reduced in the direction where the distance to the final destination is short, making it difficult to flow. The flow resistance to the molding material flowing to the cavity 4 becomes small, and the flow fronts 5, 5'... of the molding material draw an elliptical trajectory as shown in FIG. The arrival time from each gate 2, 2' to the intermediate portion is equal to the arrival time from each gate 2, 2' to the final destination in the cavity 4'.

Therefore, the hardening rate of the molding material in the vicinity of each gate 2, 2' of the cavity 4 is equal to the hardening speed of the part far from each gate 2, 2' of the cavity 4', and the molding material No distortion occurs during the curing process, and the injection molded product 3 does not deform when released from the mold.

It should be noted that the embodiments of the present invention are of course not limited to the above-mentioned embodiments. For example, a net or the like may be placed at a set location within the cavity to reduce the flow rate of the molding material, and the net or the like may be Various embodiments can be adopted, such as being included in the injection molded product so that the wall thickness of the injection molded product does not change.

Moreover, it goes without saying that injection molded products are not limited to those made of resin.

<Effects of the Invention> As described above, according to the present invention, the gate of the runner of the injection molding device can be freely set, the deformation of the injection molded product can be easily and reliably prevented, and the reliability of injection molding is improved. This provides an excellent effect.

Therefore, the flow velocity of the molding material injected into the cavity from the runner of the injection molding device through the plurality of gates is adjusted to be higher than that in the direction where the distance to the final destination of the molding material is longer in the vicinity of the gate of the cavity. By installing a weir in the direction where the distance to the final destination is short, the speed is reduced, so that the time it takes for the molded material to reach the area near the cavity gate and the area far from the cavity gate is equal. As a result, there is no difference in shrinkage during the curing process of the molded material, and the excellent effect of reliably preventing deformation of the injection molded product when demolding is achieved is achieved.

In addition, the above-mentioned means for reducing the flow rate of the molding material can be achieved by adding a weir or the like to a part of the conventionally used mold.
Therefore, an excellent effect is achieved in that deformation of the injection molded product can be easily and economically prevented.

Furthermore, since the above-mentioned method makes it possible to eliminate the shrinkage difference in the curing process of the molded material, the number of gates connecting the cavity and runner can be reduced compared to conventional methods, and gate setting becomes easier.
Therefore, there is also an effect that the runner structure of the injection molding apparatus becomes easier.

By preventing deformation of the injection molded product as described above, the product precision of the injection molded product is improved and the reliability of injection molding is significantly improved.

According to this invention, in the mold, the material is supplied to both the part of the cavity farthest from the gate where the distance to the final destination of the molded material is long and the part close to the cavity where the distance is short. During molding, a weir is installed near the gate in the part of the cavity that is closer to the gate in the shortest distance to the final destination of the molded material to reduce the flow velocity. The feeding speed of the molding material in the direction closer to the cavity and the shorter distance to the final destination of the molding material is slow, and the flow speed of the material in the direction of the longer distance to the final destination of the molding material farther from the cavity is faster. As a result, the time taken for the material to reach both cavities becomes equal, and the curing speed in both cavities becomes equal, which has the effect of preventing distortion of the molded product and preventing deformation of the injection molded product when the mold is released. This has the excellent effect of not causing any damage.

[Brief explanation of drawings]

The drawings in FIGS. 1 to 3 show one embodiment of the present invention, and FIG. The figures are Fig. 1 - sectional view, Fig. 3 is a flow front plan view of the molding material, Fig. 4 and the following are drawings of a method for preventing deformation of an injection molded product based on the conventional technology, and Fig. 5 is a plan view corresponding to FIG. 1, and FIG. 6 is a sectional view of FIG. 5. 1...Runner, 2,2',2''...Gate, 3
...Injection molded product, 4,4'...Cavity, 6...
...weir.

Claims (1)

[Claims] 1 In a method of injecting a molding material from a runner of an injection molding device into a cavity through a plurality of gates and preventing deformation of an injection molded product while the molding material hardens, Weirs are provided near the gates in the direction in which the distance to the final arrival point of the molded material is longer and in the direction in which the distance to the final arrival point is shorter, and the final arrival point of the molded material is A method for preventing deformation of an injection molded product, characterized by reducing the flow velocity of the molding material in a direction where the distance to the arrival point is short.