JP3186907B2 - Injection mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling pipe for a mold which enables uniform cooling of a curved portion of a product in injection molding of an elbow or the like made of synthetic resin.

[0002]

2. Description of the Related Art Conventionally, with regard to the design and processing of a cooling pipe of an injection molding die, an expected temperature condition has been set due to difficulties in temperature analysis inside the die, problems of processing technology for the die becoming more complicated, and the like. It was difficult to get. For example, even in the case of a mold having a simple structure, assuming the temperature difference of the cooling water, designing the amount of water, the cross-sectional area of the water pipe, the flow velocity sufficient to generate turbulence, and the pressure loss necessary to generate this flow velocity, etc. I had to calculate. ("Injection Mold" (Issued by the Industrial Research Council) pages 18-19)

[0003] Further, even in a simple shape, as in the joint die shown in Fig. 2, cooling holes 51 and 51 'provided in the slide cores 2 and 3 respectively are formed from the surface of the cooling hole to form a molded product. The difference in distance between the straight pipe portion and the curved pipe portion of the molded product became large, and a state occurred in which the cooling of the curved pipe portion of the molded product far from the cooling pipe was insufficient. In the straight section and curved section of the product,
The temperature difference became large, which had an adverse effect on quality and increased the molding cycle.

[0004]

As for the uniform cooling of the injection mold, a technique for working the cooling pipe in the mold and a technique for analyzing the temperature distribution in the mold have been required in accordance with the demand for improving the processing accuracy of the injection molded article. Progress was desired. However, the degree of freedom of design for determining the shape and arrangement of the cooling pipe in the mold is small, and much time is required until the design is completed. In particular, FIG.
As shown in the figure, the conventional mold is not in a state where the cooling pipe can cool the whole mold uniformly, but the distance from the pipe wall of the cooling pipe to the straight pipe part of the molded product and the curved pipe part of the molded product The difference from the distance has increased, which has adversely affected the quality and increased the molding cycle.

[0005] Regarding the processing of the cooling pipe, drilling machines,
A drill hole by a lathe or an end mill hole by a milling machine is generally used, and it is difficult to obtain a desired hole shape. In general, it has been dealt with by adjusting the amount of water according to manufacturing conditions. However, the method of adjusting the amount of water requires checking the water temperature and securing a flow velocity sufficient to cause a turbulent flow, which requires extra man-hours.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a fixing device having two communicating insertion ports for molding a synthetic resin elbow having a curved portion. A cavity formed of a mold and a movable mold, and two slide cores fitted into the insertion opening, wherein the two slide cores have a curved portion at a tip portion following a head portion and a straight portion. In the injection mold, the part is brought into contact with the curved part center surface of the insertion port communicating with the cavity, the slide core has a cooling hole whose axis is the head, the center of the straight part, The cooling hole forms a straight part from the end face of the head of the slide core to the height of the inner wall surface of the insertion port into which another slide core is inserted, and forms a pointed head at the tip of the straight part. , The surface to the outside of the curved part of the molded product should be substantially concentric with the outer surface of the curved part of the molded product. Rutotomoni, wherein the dimensions of the cooling Anajika wall surface to the molded article straight portion wall, from the tip of該尖head cavity parting line and the slide core parting line twisting positions become moldings curved portion center outside of It is an object of the present invention to provide an injection molding die characterized in that dimensions up to the position of the inner surface are made equal.

[0007]

According to the design of the cooling hole of the mold according to the present invention, the distance from the surface of the cooling hole to the surface of the molded product becomes substantially uniform, so that the temperature distribution of the mold becomes uniform. For this reason, the temperature distribution of the molded article becomes uniform, the product quality is improved, and the molding cycle can be shortened.

[0008]

An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a sectional view showing an example of the injection mold of the present invention. In the drawing, 1 is a cavity fixed type, 2 and 3 are slide cores, 21 and 31 are slide core heads, and 22 and 32.
Is a slide core straight portion, 23 and 33 are slide core curved portions,
4 is a molded product, 5 and 5 'are slide core cooling holes, and 6 and 6'
Denotes a partition plate, 7 denotes a cooling hole direct portion, and 8 denotes a cooling hole peak.

The cooling holes formed in the slide core are measured from the inner wall surface of the cooling hole straight pipe portion to the inner wall surface of the straight pipe portion of the molded product in FIG. The dimension from the wall surface to the outside of the tube portion to the inner wall surface outside the curved tube portion of the molded product is made substantially equal. In detail, the dimension from the wall surface of the cooling hole directly to the inner wall surface of the molded product, and the curved part of the molded product where the cavity parting line and slide core parting line are twisted from the tip of the point of the cooling hole.
The dimensions up to the position of the inner wall surface outside the center are equalized. For this reason, the cooling delay is eliminated even at the position of the inner wall surface outside the center of the curved part of the molded product where the cavity parting line and the slide core parting line where the cooling has been delayed the most are twisted positions .

The partition plate structure in the cooling holes 5, 5 'may be a jet pipe or a spiral type.

FIG. 2 is a view showing a conventional mold. As shown in the figure, in the conventional mold, the dimension from the cooling hole wall surface to the molded product wall surface has a large difference between the straight pipe portion and the curved pipe portion of the molded product, causing temperature unevenness of the mold. This caused an increase in the molding cycle.

FIG. 3 is an enlarged sectional view of the slide core of the mold in FIG. The cooling hole machined in the slide core is measured from the inner wall surface of the cooling hole in FIG. 1 to the inner wall surface of the straight pipe portion of the molded product, and from the inner wall surface of the sharp hole of the cooling hole to the outside of the curved tube portion of the molded product. The tip is asymmetric in order to make the dimension of the molded product up to the inner wall surface outside the curved tube portion substantially equal.

For this purpose, after drilling a hole by a drill or an end mill, an electrode as shown in FIG. 5 is formed, and a pointed hole at the tip of the cooling hole is drilled by a die sinking electric discharge machine.

FIG. 4 shows an embodiment of drilling a tip of a cooling hole when an electric discharge machine cannot be used. When the cross section of the hole is a circle, a large-diameter cooling hole 9 is machined along a central axis by a drill, and then the cooling hole 10 is machined to near the tip by a small-diameter drill. If cooling is incomplete with a small diameter drill hole, the tip 10 of the cooling hole 9 is machined to near the tip with an end mill.

[0015]

[Table 1] As can be seen from Table 1, in the injection molding die having the cooling holes according to the present invention, the temperature difference on the mold surface is made uniform, and the temperature difference is smaller than that of the conventional die having the cooling holes processed. 1 /
Decreased to 3. (12 ℃ → 4 ℃)

[0016]

[Table 2] Further, as can be seen from Table 2, the molded article manufactured by using the injection mold having the cooling holes formed therein according to the present invention has significantly improved angular error, roundness and impact value. (The values in the table are rain gutter PVC joints (nominal diameter 50 mm, thickness 2 mm))

[0017]

As shown in Table 1, the difference in the surface temperature of the mold can be reduced by the method for processing the cooling hole of the injection mold according to the present invention. By this effect, as shown in Table 2, the angle error of the product, the roundness, and the strength (impact value) of the product can be improved. In addition, the reduction in the temperature difference between the molded products makes it possible to shorten the molding cycle, thereby significantly increasing the production efficiency.

[0018]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of an injection mold according to the present invention.

FIG. 2 is a cross-sectional view of a conventional injection mold.

FIG. 3 is a sectional view of the slide core of the present invention.

FIG. 4 is a cross-sectional view of a slide core drilled by a drill and an end mill.

FIG. 5 is a diagram of an electrode used for machining a cooling hole tip.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cavity fixed type 2, 3 Slide core 21, 31 Slide core head 22, 32 Slide core direct part 23, 33 Slide core tip 4 Molded product 5, 5 'Slide core cooling hole 51, 51' Slide core cooling hole 6 , 6 'Partition plate 7 Cooling hole direct part 8 Cooling hole point 9, 10 Cooling hole

Claims (1)

(57) [Claims] 1. A cavity formed of a fixed mold and a movable mold having two communicating openings for molding a synthetic resin elbow having a curved portion, and a cavity fitted into each of the openings.
Of the two slide cores, the head and the leading end following the straight portion form a curved portion, and the curved portion is in contact with the curved portion center plane of the insertion port communicating with the cavity. In contact with the injection molding die, the slide core has a cooling hole whose axis is the center of the head and the straight part,
The cooling hole forms a straight portion from the end face of the head of the slide core to the inner inner wall surface of the insertion opening into which another slide core is inserted, and forms a point at the tip of the straight portion. The surface facing the outside of the curved part of the molded product is formed as a curved surface substantially concentric with the outer surface of the curved part of the molded product, the dimension from the wall surface of the cooling hole directly to the inner wall surface of the molded product, and An injection mold characterized in that the dimensions from the cavity parting line and the slide core parting line to the position of the inner wall surface outside the center of the molded product curved part where the part is twisted are equalized.