JPH0313309A - Insert molding method of base - Google Patents

Abstract

PURPOSE:To enable the insert-molded object of a base with less molding strain to be easily produced by a method in which two pars made of thermoplastic resin placed on a platelike member spaced by distance L are mutually connected by the runner of the shape with the central angle A deg. (degree), and upon insert- molding, the width W of the runner is specified. CONSTITUTION:The functional parts 10 and the functional parts 11 made of thermoplastic resin provided on a base spaced by a prescribed distance are mutually connected by the runner 8 of arc-shape. When the central angle of the arc is A deg., and the minimum distance between both functional pars 10, 11 is L (mm), the width W (mm) of the runner 12 is shown as following. W<=[(L.A)/280]. The lower limit of the width W of the runner 12 is not determined, but any runner sufficient for the flowing of molten resin may be used, and the height of the runner 8 is suitably determined according to the width W of the runner 12. The direction of the runner 12 may be on the same surface and also on front and rear. Thus, the residual stress in a molded object may be minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a substrate in which a functional part made of thermoplastic resin is disposed by insert molding on a substrate made of a flat plate made of metal or the like and having a predetermined shape and high rigidity. This invention relates to an insert molding method.

[Background of the Invention 1 The circuit boards of clocks, tape recorders, video recorders, various office equipment, etc. have bearings 9 mounted on highly rigid boards such as metal.
It is necessary to attach a large number of thermoplastic resin parts such as assembly rough joints and slide parts.

In such a case, the second. As shown in Fig. 3, mounting holes 2 are drilled in the board 1, and functional parts 3 and 4 made of thermoplastic resin are formed.
, 5.8 should be molded and attached. That is, as shown in FIG. 4, a board 1 with required mounting holes is held in a mold 7 provided with a cavity of a predetermined shape, and molten resin is poured into the mold 7 to mold each component. 1 can be installed.

When performing the above-described molding, it is necessary to provide a flow path for the molten resin, that is, a runner 8', on either the front or back surface of the substrate 1 in order to cause the molten resin to flow into the cavity of each component. The runner 8' remains in the molded product as a runner slug 8 (see Figures 1 and 2). At that time, the runner slug 8 described above contracts, but the substrate 1 does not, so internal stress occurs in the molded product. However, there are problems in that the substrate may be deformed or excessive stress may be applied to the components.

(Prior art and its problems) In order to solve the above-mentioned problems, in the past, it has been widely practiced to bypass the resin runner to make the runner easily distorted to absorb stress.However, this method If the runner is detoured too much, the residual stress may not be sufficiently reduced, and as a result of excessive detouring, excess molding material will be used.Furthermore, if the detouring of the runner is large, the flow resistance of the molten resin will increase, making molding difficult. There was also the problem of instability.

[Problem to be Solved by the Invention 1] The present invention has been made in view of the above-mentioned points, and includes a functional component made of thermoplastic resin by insert molding on a flat substrate having a predetermined shape with high rigidity. The object of the present invention is to provide a method for molding a board insert component that reduces the internal stress of the molded product when molding a plurality of resin functional components on the board.

[Means for Solving the Problems 1] In order to achieve the above-mentioned object, the substrate insert molding method according to the present invention includes two thermoplastic resin parts spaced apart from each other on a plate-like member with a central angle of Ao. When connecting arcuate runners and performing insert molding, the width W of the runners is set to [(
L-A)/280] or less.

[Example 1 Embodiments of the present invention will be described based on the drawings.

In FIG. 1, reference numerals 10 and 11 are functional parts made of thermoplastic resin that are provided on the board at a predetermined distance, and the functional parts 10 and 11 are connected on the board by an arc-shaped runner 8. ing. Then, the central angle A' of the circular arc mentioned above
(degrees), and when the minimum distance between the two functional parts IO and 11 is L (ms), the width W of the runner 8 (■
It has been found that the residual stress in the molded product can be made extremely small by formulating (2) as shown in the following equation.

W≦ [(L-A)/2801 There is no particular lower limit for the W of the runner 8, but it should be sufficient to allow the molten resin to flow, and the height of the runner 8 has little to do with residual stress. However, since a predetermined cross-sectional area is required from the viewpoint of formability, it may be appropriately determined according to the width W of the runner 8 defined by the above formula. Further, the direction of the runner 8 may be the same as shown in Fig. 1, or may be on the front and back. When insert molding is performed by connecting two functional parts with an arc-shaped runner, the width W of the runner is determined based on the relationship between the distance between the two functional parts and the center angle of the arc, so that the detour of the runner is not made large. The result is a runner with low residual stress.

[Effects of the Invention 1] The substrate insert molding method according to the present invention insert-molds two parts made of thermoplastic resin on a plate-like member with a distance glL between them, and the two parts have a center angle of A6. The width W of the runner is [(L・A)
/2801 or less, we were able to create a runner with sufficiently low residual stress without having to increase the detour of the runner, making it possible to easily produce board insert molded products with little molding distortion while saving molding material and space. It has become possible.

[Brief explanation of drawings]

FIG. 1 shows a molded product molded by the molding method of the present invention, and is a front view of the board of the runner slug portion of the board insert molded product. Figure 2 is a perspective view of a conventional board insert molded product;
FIG. 3 is a cross-sectional view of the runner east metal shown in FIG. 2, and FIG. 4 is an explanatory view of a cross-section of a mold for substrate insert molding. 10.11: Functional part, 12: Runner, L: Minimum distance between both parts, A: Center angle of circular arc, W: Width of runner. Figure 1 Figure 1 Figure 1

Claims (1)

[Claims] Two parts made of thermoplastic resin are connected at a distance L on a plate-like member by an arc-shaped runner with a central angle of A°, and when performing insert molding, the width W of the runner is set to [(L・A)/280
] A substrate insert molding method characterized by the following.