JPH033384Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention is for injection molding of ribbed synthetic resin products such as synthetic resin outer panels for automobiles, instrument panels, and interior materials. It is about improvement.

[Conventional technology]

As is well known, this type of synthetic resin product always has ribs in order to maintain the rigidity of the molded product and prevent deformation. This becomes more complex as the part becomes larger and the number of ribs increases.

Generally, ribbed synthetic resin products are made by forming a desired space c with a fixed mold a and a movable mold b, as shown in FIGS. It is obtained by injecting and curing. The obtained synthetic resin product f integrally has ribs g corresponding to the spaces c.

[Problem that the invention attempts to solve]

However, as shown in FIG. 4, the synthetic resin product molded using this mold has a sink mark h on the opposite side of the location where the rib g is provided. This occurs in most synthetic resin products, depending on the physical properties of the synthetic resin, molding conditions, etc., and seriously impairs the aesthetic appearance. If there are significant sink marks, the product cannot be used.

As countermeasures against this sink, it has been proposed to increase the injection pressure, increase the injection holding time, and lower the resin temperature as the operating conditions of the molding machine, and to lower the mold temperature for the mold.

However, various factors are added to actual molding, and this method does not function satisfactorily as a measure to sufficiently prevent sink marks.

In support of this, M. Rowbotham, manager of Foord's Research and Engineering Center, says: The bonnet is an important exterior part, but it is extremely visible to the driver and sink marks must be avoided. If plastic can eliminate sink marks, anything can be done with body work. (European Plastic's News, May 1985 issue).

[Purpose of invention]

The present invention was devised to solve these conventional problems, and its purpose is to provide an injection mold that can prevent sink marks regardless of the molding conditions.

[Means for solving problems]

In order to achieve this purpose, the injection mold for synthetic resin products with ribs according to the present invention provides a space between the molds for forming a desired shape after filling with the synthetic resin, In an injection mold for a ribbed synthetic resin product, in which a space is provided in one of the molds to form a rib that will later be connected to the synthetic resin having the desired shape, a space is provided to form the rib after the synthetic resin is filled. A concave groove is formed in another mold that faces the mold that faces the space in which the ribs are formed.

[Effect]

In the present invention, synthetic resin is injected into the space formed by the molds, and when this synthetic resin hardens, the grooves provided in the area facing the ribs have a capacity corresponding to the sink mark. It supplements the synthetic resin and does not cause sink marks on the opposite side of the rib.

[Example of idea]

An embodiment of the present invention will be described below with reference to FIG.

In the figure, 1 is a fixed type provided with a spray 2 and a runner 3, and 6 is a movable type provided with a recess 8 for forming a rib 12.

The fixed mold 1 and the movable mold 6 form a space 9 that forms the shape of the desired product 11 with recesses 4 and 7 provided on their opposing surfaces, and ribs 1 are formed on the product.
A space 10 for integrally forming the parts 2 and 2 is formed.

A groove 5 for preventing sink marks is provided in the recess 4 of the fixed mold 1 at a location facing the space 10 for forming the rib 12. The shape, depth, etc. of this groove 5 can be determined as appropriate depending on the rib to be formed.

Next, the operation of this embodiment configured in this manner will be explained.

In order to obtain a product with a main body plate thickness of 2 mm and a rib 12 thickness of 1.5 mm, PP material at 200°C is injection molded into a mold at 30 to 40°C. On the other hand, the depth of the groove 5 was approximately 0.1 to 0.2 mm.

Spray 2, injected through runner 3
The PP material fills the spaces 9 and 10 and the groove 5.
The synthetic resin is then cured at a desired temperature. At this time, ribs 12 are formed in the space 10, and
On the other side, a phenomenon that causes sink marks appears.
However, since the portion formed along the groove 5 provided in the recess 4 protrudes, this sink mark pulls the protruding portion toward the rib 12, resulting in a substantially smooth surface.

As a result, the obtained product has a smooth surface opposite the ribs 12 and has an excellent appearance, as shown in FIG.

The size of the groove 5 may be appropriately selected depending on the type of synthetic resin used, temperature, etc., but a rib with a thickness of about 1 to 1/2 of the thickness of the main body of the synthetic resin product is recommended. It has been confirmed through experiments that it is suitable for those equipped with Further, in the above embodiment, the case where the groove is provided in a fixed type is explained, but it goes without saying that it may be provided in a movable type.

[Effect of idea]

As described above, according to the present invention, the occurrence of sink marks is suppressed by the grooves, and a synthetic resin product having a smooth surface can be easily provided.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing a mold according to an embodiment of the present invention, Figure 2 is a side view showing a synthetic resin product molded with the same mold, and Figure 3 is a conventional mold. The cross-sectional view and FIG. 4 are side views showing a synthetic resin product molded with the mold. 1... Fixed type, 2... Spray, 3... Liner, 4, 7, 8... Recess, 5... Concave groove, 6... Movable type, 9, 10... Space, 11... Synthetic resin product , 12...rib.

Claims (1)

[Scope of utility model registration request] A rib in which a space is provided between the molds to form a desired shape after being filled with synthetic resin, and a space is provided in any of the molds to form a rib that connects to the synthetic resin having the desired shape after being filled with synthetic resin. In a mold for injection molding of synthetic resin products, a concave groove is formed in a separate mold that faces the space where the ribs are formed after filling with the synthetic resin, at a location facing the space where the ribs are formed. An injection mold for synthetic resin products with ribs.