JPS6192820A - Manufacture of thin planar resin form - Google Patents

Abstract

PURPOSE:To manufacture the thin planar resin form, having no camber or curvature and good in the removal of trace of a gate, by a method wherein molten resin is poured into a forming cavity from a submarine gate through the boss section of the form. CONSTITUTION:The boss section A is formed by an axial hole 4, formed in a fixed mold 1, and a groove 5a, formed on an ejector pin 5, while the boss section A is communicated with the submarine gate 7 connected to a runner 6. The total sectional area of the gate is sufficient, therefore, the number of gate may be reduced compared with conventional pin point gate system and the flow of molten resin may be improved while the flatness of the form may be maintained in high. Resin piece, remaining at the trace of the boss section A, is removed after forming. This method is suitable for the manufacture of a half case for accommodating a floppy disk or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method for manufacturing a thin-walled resin molded product used for storage containers for floppy disks, etc. Containers for discs, compact discs, video discs, etc. are thin, compact, strong, and highly protective of the stored items.
It is desired that it has good precision, no curling or bending, excellent shape retention, and is lightweight.

For this reason, conventionally, as the above-mentioned container, a container made of synthetic resin is made by manufacturing two thin-walled half-cases by injection molding of synthetic resin, and then joining them together as a backing.
available for use.

By the way, when injection molding the above-mentioned thin-walled half case, for the purpose of improving the flow of molten resin, etc.
The molten resin is supplied to the molding cavity by multiple (for example, four) pinpoint gates.

``Problems to be Solved by the Invention'' However, when multiple pinpoint gates are used as described above, the gate marks after molding protrude beyond the finished surface of the half case, resulting in defective products. J shit d
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fi b←JJ/2 Subtly changes in Musto,
There is a problem in that undesirable internal stress is generated when the molten resin solidifies, resulting in warping or bending of the molded product.

Note that there is also a method of molding using a fan gate instead of a bottle point gate, but this has the disadvantage that finishing work for the molded product becomes troublesome.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a thin-walled sheet resin molded product that is free from warping and bending and has a good finish such as edges and gate marks.

In order to achieve the above objects, the present invention combines a set of molds to form a thin-walled molding cavity, and the molds include: A boss portion located on one side of the molding cavity and communicating with the molding cavity, and a submarine gate communicating with the boss portion are provided, and molten resin is injected from the submarine gate into the molding cavity via the boss portion. A thin-walled resin molded product is molded, and then the mold is opened, the resin molded product is removed, and the resin at the boss portion is removed, and it is used as a submarine gate. The number of gates can be reduced while maintaining a good flow of molten resin, and since the resin at the boss portion is removed after the molded product is released, the finished surface is also good.

"Example" Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

1 and 2 show an example of an apparatus used to carry out the method of the present invention. In this figure, reference numeral 1 indicates a stationary mold, and 2 a movable mold, which together form a thin-walled molding cavity 3. This molding cavity 3 is for molding the half case H shown in FIGS. 3 to 5, and the surface formed by the stationary mold 1 is the back surface (inner surface) of the half case H.
It becomes.

Further, the fixed side mold IK is provided with two shaft holes 4 which communicate with the molding cavity 3 and whose axes are substantially perpendicular to the molding cavity 3 and are spaced apart from each other by a certain distance. , square ejector pins 5 whose base ends are attached to an ejector plate (not shown) are slidably inserted in a fluid-tight manner. Each ejector pin 5
8, a groove 5 & whose depth becomes shallower toward the tip is formed on the outer circumferential surface of the tip. During injection molding, each ejector pin 5 is positioned so that the end surface of its tip exactly matches one surface of the molding cavity 3, so that the groove 5& of the tip and the shaft hole 4 form the boss ISA. are busy forming each one.

Further, the stationary side mold IK is formed with a runner 6 that communicates with a sprue (not shown), and this runner 6 is formed at a portion where each boss portion A is formed at the tip of each shaft hole 4 by a submarine gear 7. are communicated with each other.

The position of each of the bosses relative to the molding cavity 3 is 70° near the side edge of the molded case H.
The half case H, which supports the installation and operation of the Tupee disk, is made up of two pieces, one for the upper part and one for the lower part, and these are combined to form one storage container. It is provided for each of the half case H and the lower half case H. And, the position of the boss evil person with respect to each molding cavity 3 is half K-XH.
In the combined state 9t/C, the respective boss portions A are provided so as not to be in positions facing each other.

Next, a method of the present invention for manufacturing a thin-walled resin molded article using the above-mentioned apparatus will be explained.

First, the mold is tightened, and the fixed mold 1 and the movable mold 2 are combined to form a molding cavity 3. Next, when the molten resin is injected from an injection molding machine (not shown), the molten resin sequentially passes through the sprue and runner 6 formed in the stationary mold l, and enters the molding cavity 3 through the submarine gate 7 and the boss part A. ni71+4←l/ 1i71:21
Sound 1. By doing so, the ejector bin 5 is pushed out. and,
Nouf case H molded in molding cavity 3,
It is ejected and taken out by this ejector pin 5. This removed half case HVc has some resin remaining at the position corresponding to the boss portion A, but this is broken off and removed.

After manufacturing the thin-walled half-case (I) as a set of two in this way, a floppy disk is housed inside the case and the two are integrated by gluing or the like to complete the final product.

Here, in the above method, since two submarine gates 7 are used, the molten resin flows in only two places during injection molding, and the conditions such as temperature and pressure of the molten resin at each gate can be easily uniformized. Half case H
The flatness is extremely good. Furthermore, since the submarine gate 7 is used, a sufficient total gate cross-sectional area can be obtained even if the number of gates is two. In other words, in the case of a conventional 4-point pinpoint gate, each gate diameter is set to 191 mm, for example.
If it is one house, the total cross-sectional area of the gate will be 2.54 + shi, whereas in the above example, each gate diameter is 1.5 am y5
The total cross-sectional area of the gate can be set to 53-.

Furthermore, in the above method, a cold slag is formed on the boss part and the runner 6, so that the flow of the molten fat is improved, and the quality of the molded product is improved. In addition, when using a conventional pinpoint gate, defects such as gate marks protruding from the finished surface are likely to occur, but with the above method, after molding the half case H, the gate remains at a position corresponding to the first boss part. Since the resin f is removed, the finished surface is good.
Moreover, since the residual resin f is tapered at the proximal end, it can be easily removed. Moreover, even if some of the residual resin f remains, it will remain on the back side of the half case H, so it will not be considered a defective product, and
When combining upper and lower half cases H,
Since the remaining resins f are placed at positions shifted from each other, the allowable amount thereof is relatively large.

In addition, in the above method, it is not possible to proceed to the assembly process without going through the process of removing the residual resin t, so even if a mistake is made in the process, a defective product will not be sent out.

By the way, in the above embodiment, the square pin was used as the edge pin y5, but it is also possible to use a round bottle.

"Effects of the Invention" As explained above, the method for manufacturing a thin-walled resin molded product of the present invention uses a boss part and a sapmer gate.
Therefore, since the number of gates is reduced while taking enough space for each gate line break, it is possible to maintain a good flow of molten fat and maintain high flatness of one molded product. Since the resin on the boss portion is removed after molding, the surface finish of the molded product is also extremely good.

[Brief explanation of drawings]

1 and 2 show an example of an apparatus for carrying out the method of the present invention, and FIG. 1 is a sectional view of the main part, and FIG. 2 is a sectional view taken along arrow 14 in FIG. 1. . In addition, Figures 3 to 5 show an example of a molded Nokhef case, where Figure 3 is a plan view, Figure 4 is a view from the N-W arrow in Figure 3, and Figure 5 is a view from the N-W arrow in Figure 3. -V arrow view. 3... Bottom shape Φ Yapitei, 5... Ejector pin, 7... Submarine gate, A...
...Boss department. 59.11.14 Showa Year, Month, Day 1, Indication of the case 1982 Patent Application No. 213839 2, Name of the invention Method for manufacturing thin-walled planar resin molded products 3, Person making the amendment

Claims (1)

[Claims] A pair of molds are combined to form a thin-walled molding cavity, and the mold has a boss portion located on one side of the molding cavity and communicating with the molding cavity, and a boss portion communicating with the boss portion. A submarine gate is installed to
Molten resin is injected from this submarine gate into the molding cavity through the boss part to mold a thin-walled resin molded product, and then the mold is opened and the resin molded product is taken out.
A method for manufacturing a thin-walled resin molded product, characterized by removing the resin from the boss portion.