JP2003220622A - Method for manufacturing foamed molding good in appearance quality - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a foamed molding good in appearance quality which prevents the occurrence of an annular mark around a gate. <P>SOLUTION: In the method for manufacturing the foamed molding, injection from a molding machine into a mold is started by a signal from a valve gate 2 for opening/closing a communication opening between a hot runner 4 and a cavity 1. An imaginary gate is installed in a signal system separately from the valve gate 2. First, the injection of a resin from the molding machine to the hot runner 4 is started by the opening signal of the imaginary gate. After the inner pressure of the hot runner 4 is increased to a prescribed pressure, the valve gate 2 for opening/closing the communication opening is opened, and the resin is packed in the cavity 1 to mold the molding. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a foam molded article having a good appearance and used for interior parts of automobiles. 2. Description of the Related Art Foam molded products are widely used for automobile interior parts such as door trims and dashboards. Among such automobile interior parts, molded articles are not used for high-grade vehicles. Since the surface is covered with a finishing material, the appearance quality of the surface does not matter, but in the case of inexpensive vehicles, it was molded without covering the surface except for some ornaments etc. from the viewpoint of cost. Generally, the skin is left as it is, and its appearance quality is emphasized. In a conventional general method of molding a foamed product, a valve gate for opening and closing a communication port between a hot runner and a cavity is opened by an open signal from a molding machine.
When the opening of the valve gate is confirmed on the molding machine side, a resin is injected from the molding machine to form a foam molded article in the cavity. For this reason, a delay time occurs between the opening of the valve gate and the injection of the resin from the molding machine, and even before the resin is injected from the molding machine, the resin is opened by the foaming pressure at the same time as the opening of the valve gate. Had been injected into the cavity. FIG. 3 shows a change in the speed at which the resin is injected into the cavity. When the valve gate is opened at the time A, the resin is injected into the cavity by the foaming pressure, and the valve by the molding machine is used. By confirming the opening of the gate, the injection of the resin starts at the time point B. In such a series of processes, as shown in FIG. 4, the resin first injected into the cavity by the foaming pressure is cooled to form a skin layer, and then the resin injected from the molding machine is injected into the cavity. Then, the skin layer is deformed by the injected resin as shown in FIG. Due to the deformation of the skin layer, a ring-shaped mark is generated in the gate portion, and there is a problem that the appearance quality of the molded product is deteriorated. SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and provides a method for producing a foam molded article having a good appearance quality without a ring-shaped mark generated around a gate. It was done to do so. [0006] In order to solve the above-mentioned problems, the present invention provides a method of manufacturing a foam molded article having good appearance quality, which comprises a valve for opening and closing a communication port between a hot runner and a cavity. In the method of manufacturing a foam molded product in which injection from a molding machine to a mold is started by a signal from a gate, a virtual gate is set in a signal system separately from the above-described valve gate, and first, a virtual gate release signal is set. Injection of resin from the molding machine to the hot runner starts, and after the internal pressure of the hot runner rises to a predetermined pressure, a valve gate that opens and closes the communication port with the cavity is opened, and the resin is filled into the cavity and foam molding is performed. It is characterized in that the product is molded. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a mold used when carrying out the method for producing a foam molded product having good appearance quality according to the present invention. A cavity 1 for molding the molded product is provided. Valve gates 2 and 2 are provided. The valve gates 2 and 2 are opened and closed by operating mechanisms 3 and 3 operated by signals from the molding machine, respectively, and a hot runner 4 for guiding resin supplied from the molding machine to the valve gates 2 and 2 is provided. It is. In addition,
Although not shown, it goes without saying that a mold opening / closing mechanism, a mold clamping mechanism, a molded product discharging mechanism, and the like are provided. However, since this point is the same as that of a conventional apparatus of this type, description thereof is omitted. . In the present invention, a virtual gate is set in the signal system of the molding machine (not shown) separately from the valve gate, and after the molding machine issues a virtual gate release command signal, the virtual gate is set at a fixed time period. An opening confirmation signal is returned to the molding machine. When the molding machine receives the opening confirmation signal of the virtual gate, injection of the resin is started, and then an opening command signal of the valve gates 2 and 2 is issued. is there. [0009] In the above configuration, the molding machine first issues a virtual gate opening command signal. FIG.
Indicates a change in the speed at which the resin is injected into the cavity, and when a virtual gate opening command signal is given at the time of A, a virtual gate opening confirmation signal is returned to the molding machine after a certain period of time, Injection of the resin starts at the point B. Subsequently, a signal is given from the molding machine to the operation mechanisms 3 and 3, the valve gates 2 and 2 are opened, and the resin is injected into the cavity 1 from the valve gates 2 and 2. The dotted line indicates the amount of resin injected into the virtual cavity by the foaming pressure, assuming that there is a virtual cavity connected to the virtual gate when the virtual gate is opened. Thus, in the conventional method, as described above,
The resin first injected into the cavity by the foaming pressure forms a skin layer, which is deformed and deteriorates the appearance quality of the foam molded product. It is a gate, and since the actual valve gates 2 and 2 are not opened, only the pressure of the hot runner 4 is increased by the foaming pressure.
Therefore, the resin in the hot runner 4 is not injected into the cavity 1 due to the foaming pressure.
The deformed skin layer as described above is not formed on the foam molded article, and the appearance quality of the foam molded article is not deteriorated. As described above, according to the present invention,
In a method of manufacturing a foam molded product in which injection from a molding machine to a mold is started by a signal from a valve gate that opens and closes a communication port between a hot runner and a cavity, a virtual gate is used as a signal system separately from the valve gate described above. First, the injection of the resin from the molding machine to the hot runner is started by the virtual gate release signal, and after the internal pressure of the hot runner rises to a predetermined pressure, the valve gate for opening and closing the communication port with the cavity is opened. Since the foam is formed by opening the cavity and filling the cavity with resin, the molded product molded in the main cavity has a skin formed by the resin that is first injected into the cavity by the foaming pressure from the hot runner. There is no deformation of the layer, and therefore, it is possible to mold a high quality foam molded article without deteriorating the appearance quality of the foam molded article. Accordingly, the present invention greatly contributes to the industry as providing a method for producing a foam molded article having good appearance quality which has solved all the conventional problems.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing an example of a mold used to carry out the present invention. FIG. 2 is a diagram showing a change in a speed at which a resin is injected into a cavity during molding by the molding method of the present invention. FIG. 3 is a diagram showing a change in a speed at which a resin is injected into a cavity during molding by a conventional molding method. FIG. 4 is a cross-sectional view showing a state in which a resin is injected by foaming pressure during molding by a conventional molding method. FIG. 5 is a cross-sectional view showing a state in which a resin is injected by injection when molding by a conventional molding method. [Description of Signs] 1 Cavity 2 Valve gate 4 Hot runner

   ────────────────────────────────────────────────── ─── Continuation of front page    F term (reference) 4F202 AB02 AG20 AH26 AP03 CA11                       CA23 CB01 CK06 CK07 CK11                 4F206 AB02 AG20 AH26 AP036                       JA04 JF04 JL02 JM04 JN15                       JQ81

Claims (1)

Claims: 1. A method for producing a foam molded product, wherein injection from a molding machine to a mold is started by a signal from a valve gate that opens and closes a communication port between a hot runner and a cavity. The virtual gate is set in a signal system separately from the valve gate, and first, the injection of the resin from the molding machine to the hot runner is started by the virtual gate release signal, and the above-described operation is performed after the internal pressure of the hot runner rises to a predetermined pressure. A method for producing a foam molded article having good appearance quality, characterized in that a valve gate for opening and closing a communication port with a cavity is opened to fill the cavity with a resin to mold a foam molded article.