JPS59106942A - Molding method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method for molding a ring-shaped molded product by injection molding of plastic.

Prior Art Figures 1 and 2 show the shape of a fixing ring (υ), which is formed with a female thread (2) and has four legs (3 bars, 4 bars, 5) protruding from the opposite H surface. ) (6), the end face of which is a G plane.These legs (3) -
As shown in the figure, (6) is different in its protruding shape and spacing. This fixed ring has the function of a so-called helicoid seat for the helicoid unit of a camera lens.In other words, the rotational movement of the distance ring moves the lens system back and forth for focusing. The ring is operated by the photographer's touch, and this feeling is greatly affected by the fit of the screws. Therefore, in the case of the fixing ring shown in Fig.
2) Good roundness is required.

In this regard, it is generally said that in order to obtain an accurate perfect circle in the molding method, it is better to use multi-point gates and inject resin. For example, a three-point gate method is used for gears and the like. Therefore, even when molding a molded product such as the identification ring shown in Figure 1, it is expected that the resin will be filled in a well-balanced manner by using 3, 4, or 6 gates. If a multi-point gate system such as a three-point gate is adopted, the arrangement of runners, etc. becomes complicated.In addition, when a large number of runners are used, the manufacturing structure becomes complicated, making it difficult to implement. I'm pregnant.

the purpose The present invention was made in view of these points.

It is an object of the present invention to provide a method for molding a ring-shaped molded product having four legs with different protruding shapes and intervals, which can improve roundness with a small number of gates. □ Structure An embodiment of the present invention will be described with reference to the drawings.

First, the molded product targeted in this example is the fixing ring shown in FIG. 1, and the gate position A is shown in FIG.
- Point F (indicated by a black circle) is set and a molding test is conducted using various combinations. Here, A, B, D, E
Each point is sb, C, on the end face (G plane) of legs (3) to (6).
Each point of F [I (is located on the surface, and the diameter of all pinpoint gates is φ068. Figure 4 shows the outline of the mold, and various templates (7) (8 bars 9), reduction piece α ,0αυα4(2
), a cavity (141) is formed, and a nozzle (
By injecting resin into the cavity α◆ through the runners a and a′i), a molded product, that is, a fixing ring (1) is formed. In addition,
PL is a parting line, and after molding, the template (7) is separated from the roof (8) and removed from the mold piece αq by turning the fixing ring (1). Further, FIG. 5 shows the arrangement of the runner a9 and the gate αη, and corresponds to FIG. 3.

Therefore, molding tests were conducted using various combinations of gate positions, and the roundness results are shown in Table 1.

Table 1 Here, for example, when the gate position is tA, resin should be injected only from the gate aη at point A, and resin should not be injected from the other gate positions B-F shown in Fig. 3. means. Further, the roundness is a value measured by a roundness measuring machine (using Roncom 2D manufactured by Tokyo Seimitsu Co., Ltd.) for the φ59 part 0 shown in FIG.

The molding conditions are: resin: polycarbonate,
Molding machine: Sumitomo Nestal Neopine) 150/75, injection speed: 45111/MICs holding pressure crab 850
Kg/cd.

Holding pressure time: 5. Osec, mold temperature near 8~80'C
shall be.

According to the results of such forming tests, even if the number of gates is 1, if the gate position is 1 (circularity: 46μ),
In the case of gate position B (52 μm), gate position D (52 μm)
pm) and gate position E (40 μm), the circularity is small and satisfies the predetermined standard.

That is, by setting a pinpoint gate on the end face of any of the legs (3) to (6), it is possible to improve the roundness by using a single point gate.

Also, even if the number of gates is 2, the gate position is A.

B (4Bpm) (D case and gate position, E (
58 μm), it satisfies the predetermined standard.

In other words, by setting a pinpoint gate on each end face of two closely adjacent legs (3), (4) or (5), and (6) to create a two-point gate, the roundness can be improved. This will improve the results. In this way, it is possible to obtain a fixing ring (1) with good roundness by using a small number of gates with one or two points, and the helicoid unit has a good thread fit and smooth operation. It can be done. In addition, there are other gate positions such as A, B, and D that show good roundness, but these three-point gate systems have complicated runner arrangements, so they are excluded. It is.

Effects As described above, the present invention is simple because pinpoint gates are set at one point on the end face of any of the legs or at two points on the end faces of two closely adjacent legs, and resin is injected. The roundness of the ring-shaped molded product can be improved using a small number gate method.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention; Figure 1PJ1 is a front view, Figure 2 is a sectional view taken along the line X-X, Figure 3 is a front view showing the gate position arrangement, and Figure 4 is a mold. FIG. 5 is a rear view.

Claims (1)

[Claims] In a method for molding a ring-shaped molded product having four legs with different protruding shapes and different intervals, one of the end faces of any one of the legs is
Set a bin point gate at a point or at two points on the end faces of two adjacent legs. A molding method characterized by injecting resin.