JPH09272139A - Injection molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce mold clamping forces and make the change of the conditions such as the pressure and speed of injection possible independent of cavities by a method wherein the injection into a first cavity is performed under the condition that the valve gates communicating with the remaining cavities are closed and, just before the finish of the above-mentioned injection, a valve gate communicating with a second cavity is opened. SOLUTION: After the finish of charging in a first cavity, the valve of the first cavity is closed and simultaneously the valve of a second cavity is opened. At the successive injection to the cavity after the charging to the second cavity, the overlapping time in the respective opening valve timings is set to be 0-2sec. By injecting in a third cavity and the rest in the same timing as mentioned above in the following, the maximum value 4 of a mold clamping force in the whole molds shows a value smaller than the sum of the maximum values 3a and 3b of the mold clamping forces in the respective cavities.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding method for a hot runner mold having a plurality of valve gates and having the same shape or different shapes.

[0002]

2. Description of the Related Art Conventionally, in injection molding of a multi-cavity hot runner mold having a plurality of valve gates, in the case of the multi-cavity multi-cavity injection, all cavities are injected at the same timing, resulting in different shapes In case of multi-cavity injection, all cavities are being injected at the same timing, or the cavities are used to adjust the amount of resin, and only the injection start or injection end timing is shifted by the valve gate opening / closing timing. Was ejecting.

[0003]

However, in the above-mentioned molding method, since the resin filling process is almost at the same timing, the time when the mold clamping force shows the maximum value is almost the same in all the cavities. Therefore, the maximum value of the mold clamping force in the entire mold is as shown in FIG.
That is, in FIG. 2, if 2a is a mold clamping force generated when one cavity A is taken, and 2b is a mold clamping force generated when one cavity B is taken, the cavity A
The mold clamping force generated when the cavity B is set is 1 and the maximum value 5 of 1 is equal to the sum of the maximum value 3a of 2a and the maximum value 3b of 2b. That is, the maximum value of the mold clamping force in the entire mold is the sum of the mold clamping force generated in each cavity, and a large molding machine corresponding to that is required. Further, in the case of a mold with a large number of different shapes, it is possible to change the amount of resin measured by the cavity, but it is impossible to change the conditions of injection pressure and injection speed depending on the cavity. There has been a problem that it is difficult to set molded articles with the same mold.

[0004]

In order to solve the above problems, the present invention is characterized in that molding is performed by the following procedure.

Injection into the first cavity is performed with the valve of the valve gate leading to the other cavity closed.
0 to 2 seconds before the end of injection, the valve of the valve gate leading to the second cavity is opened and injection into the second cavity is performed. Further, the valve of the valve gate leading to the first cavity is closed after the injection into the first cavity is completed. Injection into the third and subsequent cavities is similarly performed.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is a multi-cavity hot runner mold, wherein each cavity has a hot runner valve gate, and the valve opening / closing timing is arbitrary. In the mold that can be set, when the valve of the first cavity is closed after the filling of the first cavity is completed and the valve of the second cavity is opened at the same time, the second cavity is filled and the cavities are sequentially injected. The opening overlap time of each valve timing is set to 0 to 2 seconds, and the molding method is to inject at the same timing from the third cavity onward, and the molding is performed by this means.
The maximum value of the mold clamping force for the entire mold is as shown in FIG. 1 because the time for which the mold clamping force from the resin filling process takes the maximum value varies depending on the cavity. That is, FIG.
2a is the mold clamping force generated when one cavity A is taken, and 2b is the mold clamping force generated when one cavity B is taken, the cavities A and B
The mold clamping force generated when the set is taken is 1 and the maximum value of 1 is 4 and the maximum value of 2a is 3a and the maximum value of 2b is 3
It is smaller than the sum of b. That is, since the maximum value of the mold clamping force in the entire mold is smaller than the sum of the maximum values of the mold clamping force in each cavity, it is possible to perform molding with a molding machine smaller than the conventional one. .

According to a second aspect of the present invention, in a multi-cavity hot runner mold having a plurality of valve gates, molding conditions such as injection speed, injection pressure, and injection amount are arbitrarily set for each cavity. The molding method according to claim 1, which is capable of performing, in a mold having a large number of differently shaped molds, there is little overlap between injection into one cavity and injection into another cavity. For example, if the injection is performed under the injection conditions suitable for the second cavity at the time when the injection into the first cavity is completed, it is possible to set the optimum injection conditions for each cavity. Further, it has an effect that the optimum conditions for the third and fourth cavities can be sequentially selected.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings. When the two molded products of A and B each take one, when they have a process as shown in FIG. 1 and when they show the mold clamping force as shown in FIG. Injection to A is performed with the valve of the valve gate leading to the cavity of B closed, and 0 to 2 seconds before the end of injection, the valve of the valve gate leading to the cavity of B is opened and injection to the cavity of B is performed. To do.
The valve of the valve gate leading to the cavity of A is closed after the injection into the cavity of A is completed. The process and mold clamping force at this time are shown in Fig. 2, and the maximum value of the mold clamping force becomes smaller than the sum of the maximum values of the mold clamping force in the case of taking one piece respectively. Reduction is possible. Further, since the time when the injection into A and the injection into B into the cavity overlap is small, it is possible to set the injection conditions according to the respective cavities of A and B.

[0009]

In the injection molding of a multi-cavity hot runner mold having a plurality of valve gates, it is possible to reduce the mold clamping force and set the molding conditions for each cavity.

[Brief description of drawings]

FIG. 1 is a diagram showing a multi-cavity process and a mold clamping force (example of 2-cavity) in the present invention.

FIG. 2 is a diagram showing a conventional multi-cavity process and mold clamping force (an example of two-cavity production).

[Explanation of symbols]

1 Clamping force generated when cavity A and cavity B are set 2a Clamping force generated when cavity 1 is taken 2b Clamping force generated when cavity B is taken 1a Maximum of 3a 2a Value 3b Maximum value of 2b 4 Maximum value of 1 when the molding method according to the present invention is used 5 Maximum value of 1 when the conventional molding method is used

Claims (2)

[Claims] 1. A multi-cavity hot runner mold having a hot runner valve gate for each cavity, and a valve opening / closing timing of the mold can be arbitrarily set. After the completion, the valve of the first cavity is closed, the valve of the second cavity is opened at the same time, the second cavity is filled, and when sequentially injecting into the cavity, the open overlap time of each valve timing is 0. An injection molding method in which injection is performed for a period of up to 2 seconds, and in which the third cavity and thereafter are injected at the same timing. 2. In a multi-cavity hot runner mold having a plurality of valve gates, each molding condition such as an injection speed, an injection pressure and an injection amount can be arbitrarily set for each cavity. 1. The injection molding method according to 1.