JPH06126796A - Method for controlling temperature of mold for injection molding - Google Patents

Abstract

PURPOSE:To correct a warpage, deformation and failure of a side without performing correction of a mold by disclosing the mechanism of deformation and controlling the principal factor causing the warpage. CONSTITUTION:In the case of molding a product 1 provided with at least a bottom wall 11 and a sidewall 12 continued thereto by injection molding, cooling pipes 31, 32 are provided in the core 21 side and the cavity 22 side of a mold 2 so as to approach the intersections 13 of the bottom wall 11 and the sidewall 12 of the product 1 along the same. The internal surface and the external surface of the product 1 in the crossing parts 13 are individually cooled and controlled by the respective cooling pipes 31, 32.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding die used for injection molding of thermoplastics, and more particularly to a bottom wall and a side wall continuous with the bottom wall such as a box shape and a cylindrical shape. The present invention relates to a method for controlling the temperature of an injection mold for molding a product having

[0002]

2. Description of the Related Art For example, when a box-shaped product shown in FIG. 7 or a cylindrical product shown in FIG. 8, that is, a product having a bottom wall and a side wall continuous with the bottom wall is formed by injection molding, it is shown in FIG. As described above, in the case of the box-shaped body, the center portion of the side wall warps inwardly, and as shown in FIG. 10, in the case of the cylindrical shape, the handle portion receives an outward force. Deformation defects occur where the non-existing part warps inward.

Conventionally, since the mechanism of this deformation has not been clarified, the amount of warp of the side wall has been empirically obtained or predicted by using CAE or the like. Then, based on the obtained value or the predicted value, the side surface shape of the mold is made to be convex or concave. In addition, for example
As disclosed in Japanese Patent Laid-Open No. 06710, there is also proposed a product in which a side surface and a bottom surface of a molded product are provided with a notch at an intersecting portion on the inner surface side to prevent warpage.

[0004]

However, in the case where the side surface shape of the mold is made to be convex or concave, it is necessary to process the side surface into a curved surface when processing the mold, so that it is difficult to process the mold. Need technology. Further, in the case of using CAE or the like, there is a problem that the trial manufacture and modification of the mold have to be repeated because the prediction of the warp amount is not accurate. Therefore, there is a problem that it takes a long time to develop a product and the development cost is high.

Further, in the case where the notch is provided at the inner surface side intersection of the side surface and the bottom surface of the molded product, there is a problem that a high technique is required for processing and the strength of the molded product is reduced as in the above case. It was

The present invention has been made in view of the above circumstances, and an object thereof is to clarify the mechanism of deformation and control the main factors of warpage generation, so that the side warpage can be performed without modifying the die. An object of the present invention is to provide a method for controlling the temperature of a mold for injection molding that enables correction of deformation defects.

[0007]

In order to solve the above problems, a method for controlling the temperature of an injection molding die according to the present invention is
It is applied to an injection-molding mold for molding a product having at least a bottom wall and a side wall continuous with the bottom wall and a core side of the mold so as to be close to the intersection of the bottom wall and the side wall of the product. A cooling pipe is provided on the side of the cabinet, and the inner surface and the outer surface of the intersection of the product are individually cooled by the cooling pipes.

[0008]

[Operation] First, the mechanism of warpage will be described.

In injection molding, a resin is heated to a molten state, press-fitted into a mold, cooled and solidified to obtain a molded product (product).
Take out.

In the course of this cooling and solidification, the volume of the molded product decreases, that is, shrinks, as the temperature decreases. When the temperature at the intersection of the bottom wall and the side wall of the molded product at the time of cooling and solidification (at the start of shrinkage) is higher than the temperature on the inner surface side as shown in FIG. 3, for example, 80 ° C. on the inner surface side. Since the outer surface side has a large amount of volume change (shrinkage amount) on the inner surface side (40 ° C. or the like), the side wall falls inward.

In the case of the box shape, the left and right ends of the side wall intersect at right angles with the left and right ends of the adjacent side walls, so that the left and right ends of the side wall have higher rigidity than the central part. as a result,
Since the inward lean amount (inward warp amount) of the end portion is smaller than that in the central portion, it is considered that the inward warp of the side wall occurs as shown in FIG.

In the present invention, based on such a warp generation mechanism, cooling pipes are provided on the core side and the cavity side of the mold so as to be close to the intersection of the bottom wall and the side wall of the product,
The inner surface and the outer surface of the intersection portion of the product are individually cooled and controlled by the respective cooling pipes. That is,
By changing the inner surface temperature and the outer surface temperature of the product, it becomes possible to control the amount of warpage of the side wall.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the structure of an injection molding die to which the temperature control method of the present invention is applied. However, in this embodiment, a mold structure for molding the box-shaped product shown in FIG. 4 is shown.

That is, the bottom wall 11 and the side wall 12 of the molded product 1
In order to independently control the temperature of the inner and outer surfaces of the intersection 13 of the mold 1, the core 21 side and the cavity 22 side of the mold 2 are cooled so as to be close to the intersection 13 of the product 1. Pipes 31 and 32 are provided. Further, in order to ensure temperature control, the mold material in this portion is divided (reference numeral 21).
1, 221). Reference numeral 4 in the figure indicates a cooling pipe conventionally provided.

FIG. 2 shows each cooling pipe 4 provided on the mold 1.
It is the figure which showed the arrangement | positioning of 31 and 32 typically.

That is, the cooling pipe (shown by the solid line) 31 provided on the core 21 side is arranged along the entire circumference of the intersection 13 of the molded product 1, and is provided on the cabinet 22 side. The cooling pipe (shown by the one-dot chain line) 32 is arranged only along the intersection 13 between the longer side wall of the molded product 1 and the bottom wall 11. The arrangement of the cooling pipes 4 provided conventionally is indicated by a broken line.

Using the mold having such a structure, injection molding is carried out under the molding conditions shown in FIG.
The temperature of the refrigerant was changed to solidify by cooling to prepare a box-shaped molded product shown in FIG. Then, the amount of warpage of the molded product at that time was measured by a known three-dimensional measuring device. The measurement result is shown in FIG.

That is, the temperature on the outer surface side (the temperature on the side of the cavity 22) of the intersection 13 of the molded product 1 is the temperature on the inner surface side (the core 2).
If the temperature is higher than the temperature on the one side), external warpage occurs, and the greater the temperature difference, the greater the amount of warpage. Also,
When the temperature on the outer surface side (the temperature on the side of the cavity 22) of the intersection 13 of the molded product 1 is lower than the temperature on the inner surface side (the temperature on the core 21 side), inward warpage occurs, and the greater the difference between the two temperatures, the more It can be seen that the amount of warp is also increasing. And molded product 1
It can be seen that the smaller the temperature difference between the inside and the outside, the smaller the amount of warp, and that a good product with no deformation defects can be molded.

That is, when the box-shaped product shown in FIG. 4 is molded, the refrigerant temperatures of the cooling pipes 31 and 32 may be controlled so that the temperature difference between the inside and outside of the intersection 13 of the molded product 1 becomes small. It will be. Thus, it was confirmed that the temperature control method of the present invention can reduce the amount of side wall warp deformation without modifying the mold.

In the present invention, the structure in which the cooling pipes 31 and 32 are provided on the core 21 side and the cavity 22 side of the mold 2 respectively has been described, but instead of the cooling pipes 31 and 32, a heater or the like is used. It is possible to provide a heat medium and control the temperature by this heat medium.

[0022]

According to the method of controlling the temperature of the mold for injection molding according to the present invention, the cooling pipe is provided on the core side and the cavity side of the mold so as to be close to the intersection of the bottom wall and the side wall of the product. By providing cooling control of the inner surface and the outer surface of the product by the mold individually, the temperature balance of the inner and outer surfaces of the product can be changed to control the warp amount. The warp deformation defect of the side wall of the product can be corrected without correction. Therefore, the development period can be shortened and the development cost can be reduced by reducing the number of die modifications, and the product quality can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing a structure of an injection molding die to which a temperature control method of the present invention is applied.

FIG. 2 is a diagram schematically showing an arrangement of cooling tubes provided in a mold.

FIG. 3 is a diagram showing an example of an inner surface temperature and an outer surface temperature of a product when it is cooled and solidified.

FIG. 4 is a diagram showing an example of a box-shaped molded product.

FIG. 5 is a list showing molding conditions.

FIG. 6 is a graph showing the measurement results of the amount of warpage of a molded product after injection molding.

FIG. 7 is a perspective view showing an example of a box-shaped molded product.

FIG. 8 is a schematic view showing an example of a cylindrical molded product.

9 is a perspective view showing how warpage deformation of the molded product shown in FIG. 7 occurs.

FIG. 10 is a schematic diagram showing how warpage deformation of the molded product shown in FIG. 8 occurs.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molded product 2 Mold 4 Cooling pipe 11 Bottom wall 12 Side wall 13 Intersection 21 Core 22 Cabin 31, 32 Cooling pipe

Claims (1)

[Claims] 1. A mold for injection molding for molding a product having at least a bottom wall and a side wall continuous with the bottom wall, wherein the mold of the mold is provided so as to be close to an intersection of the bottom wall and the side wall of the product. A method for controlling the temperature of an injection molding die, wherein cooling pipes are provided on the core side and the cabinet side, and the inner surface and the outer surface of the intersection of the product are individually controlled by the cooling tubes.