JPH0528966B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an injection molding method, and particularly to an injection molding method for eliminating warpage of a plate-shaped molded product.

[Conventional technology]

8 to 11 are explanatory views showing a plan view, a partial sectional view, a bottom view, and a sled of a block toy molded by injection molding.

The unit 1 of this block toy consists of a main body 10 in the shape of a thin rectangular block with an open bottom, and a large number of cylindrical projections 11, for example, 50, integrally protruding from the top surface of the main body. It is played by assembling buildings and vehicles by combining individual block toys.

Hereinafter, a conventional injection molding method for injection molding the unit 1 of the above-mentioned block toy will be explained with reference to FIGS. 12 to 16.

In the figure, 2 is a mold clamping mechanism, and this mold clamping mechanism 2
A movable platen 21 is fixed to the tip of a mold clamping ram 20, and a movable die 22 is attached to this movable platen 21. This mold clamping mechanism 2 has a knock rod 2.
3. Ejector plate 24, product ejection pin 25
etc. are equipped.

3 is a raw material injection mechanism, and this raw material injection mechanism 3 has a fixed plate 31 fixed to the injection end of the injection machine 30, and a runner stripper plate 32 and a cavity plate 33 of the die on the fixed side are fixed to the fixed plate 31. , locate ring 34, sprue bush 35, stripper bolt 36, runner 3
8 take-out machine 37, etc. are attached.

The steps of the conventional injection molding method using the above-mentioned injection molding apparatus will be explained.

First, the mold clamping ram 20 is advanced to clamp the die (the movable die 22, the fixed runner stripper plate 32, and the cavity plate 33) (see FIG. 13). Next, the raw material injection mechanism 30
is activated to inject and fill the cavity of the die with molten molding material (see FIG. 14). Then, when the molding material in the cavity is solidified, the mold clamping ram 20 is moved back to open the die (see FIG. 15). At the same time, the product ejecting pin 25 is advanced to take out the molded product 4 (see FIG. 16).

[Problem that the invention seeks to solve]

When a plate-shaped molded product such as the unit 1 of the above-mentioned block toy is injection molded, as shown in FIG.
Warpage (that is, a state in which the center of the top surface is lowered and both ends are warped and raised) 40 occurs. For example, in the illustrated block toy unit 1, the length is about 160 mm, and warping 40 occurs about 0.3 to 0.5 mm. When this warpage 40 occurs, it may not fit properly with other block toys, and eventually assembly may become impossible.

Therefore, in the conventional injection molding method described above,
As a way to eliminate warpage, use product ejection pin 2.
When extruding the molded product 4 in step 5, the molded product 4 is forcibly extruded to try to eliminate warping. However, in the step of taking out the molded product 4, the warpage cannot be corrected because the molded product 4 has already solidified.

An object of the present invention is to provide an injection molding method that can eliminate warpage.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention is characterized in that the die is opened before the material in the cavity solidifies, the molded product is then reversely rolled and cooled, and the molded product is taken out after cooling. shall be.

[Effect]

In the present invention, the die is opened before the material in the cavity solidifies and the molded product is reversely warped, so that warpage occurs while the molded product cools and solidifies, and the warp offsets the aforementioned reverse warp. , it is possible to produce molded products with extremely small warpage.

〔Example〕

Hereinafter, a first embodiment of the injection molding method of the present invention will be described.
This will be explained with reference to FIGS. 7 to 7.

In the figure, the same reference numerals as in FIGS. 12 to 16 indicate the same parts. In the figure, 26 is a foldable ejector plate that rotatably supports one end of the product ejection pin 25. On the other hand, an adjusting block 27 is removably attached to the ejector plate 24 supported by the knock rod 23, and the center-folding type ejector plate 26 is supported by the adjusting block 27. By changing the adjustment piece 27, the center-folding angle of the center-folding type ejector plate 26 can be freely changed.

Next, the injection molding method of the present invention using the injection molding apparatus shown in FIGS. 1 and 2 will be explained.

First, the mold clamping ram 20 is advanced to clamp the die (the movable die 22, the fixed runner strip plate 32, and the cavity plate 33) (see FIG. 3). Next, the raw material injection mechanism 3 is operated to inject and fill the cavity of the die with the molten molding material (see FIG. 4). The steps up to this point are the same as those of the conventional injection molding method, but the next steps are the steps of the injection molding method of the present invention. That is, before the material in the cavity is solidified, the clamping ram 20 is moved back to open the die (see FIG. 5). At the same time, the ejector plates 24 and 26 are advanced one step, and the molded product 4 is slightly protruded and cooled while being forcibly warped (see FIG. 6). At this time, warpage occurs while the molded product 4 cools and solidifies, and the warp offsets the reverse warp that was forcibly generated by protruding the molded product 4 described above, and the warpage throughout the molded product 4 is reduced. becomes extremely small. For example, in the block toy unit 1 shown in FIGS. 8 to 11, the length is about 160 mm, but the warp is about 0.05 to 0.1 mm, and the warp is the same molded product 4 made by the conventional injection molding method. It is small at 1/3 to 1/10 of the sled.

When the above-described cooling and solidification of the molded product 4 is completed, the ejector plates 24 and 26 are advanced two steps to take out the molded product 4 (see FIG. 7).

Note that the steps of the injection molding method of the present invention described above are as follows:
Although the ejector plates 24 and 26 are advanced in two stages, this can naturally be operated automatically in the same manner as in conventional injection molding methods by setting a timer or limit switch.

〔Effect of the invention〕

As is clear from the above, in the injection molding method of the present invention, the die is opened before the material in the cavity solidifies, and then the molded product is reversely rolled and cooled, so that the molded product is cooled and solidified. The warpage that occurs in between cancels out the above-mentioned reverse warp, and the warp can be made extremely small.

[Brief explanation of drawings]

1 to 7 show an embodiment of the injection molding method of the present invention, FIG. 1 is a front view showing an injection molding apparatus used in the injection molding method of the present invention, and FIG. 2 is an ejector plate as well. Figure 3 is an explanatory diagram showing the mold clamping process, Figure 4 is an explanatory diagram showing the injection process, Figure 5 is an explanatory diagram showing the mold opening process, and Figure 6 is an explanatory diagram showing the mold opening process. FIG. 7 is an explanatory diagram showing the process, and FIG. 7 is an explanatory diagram showing the molded product removal process. 8th
Figures 9, 10, and 11 are plan views of the molded product (single block toy), and A- in Figure 8.
They are an A-line sectional view, a bottom view, and a front view. Fig. 12 is a front view showing an injection molding apparatus used in a conventional injection molding method, Fig. 13 is an explanatory drawing showing the mold clamping process, Fig. 14 is an explanatory drawing showing the injection process, and Fig. 15 is an explanatory drawing showing the injection process.
The figure is an explanatory diagram showing the opening of the mold, and FIG. 16 is an explanatory diagram showing the process of taking out the molded product. 1... Single block toy (molded product), 2...
Mold clamping mechanism, 22... die, 26... center-folding ejector plate, 3... raw material injection mechanism, 33... cavity plate.

[Claims]

1 Consists of a hollow frame-shaped main body having a bottom wall and a mounting leg that integrally projects upward from the main body,
The main body portion includes an annular protrusion that frames the lower surface of the bottom wall, an annular protrusion with a triangular cross section that is provided downward in multiple layers inside and outside the recess surrounded by the protrusion, and the annular protrusion. A gate portion formed by cutting out the edge;
a primary molded part made of a hard resin, which communicates with the gate part and has an introduction groove formed radially across the annular protrusion; A secondary molded part is formed of a soft resin having a higher melting temperature than the resin of the primary molded part, which embeds the annular protrusion and protrudes flatly from the annular protrusion. The surface of each annular protrusion of the part and the inner peripheral surface of the annular protrusion are melted with a soft resin during molding of the secondary molded part, and are welded and integrated with the secondary molded part. Rubber legs for equipment.