JP3797581B2 - Injection mold - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an injection mold, and in particular, can mold an injection-molded product (hereinafter referred to as “molded product”) free from warpage, deformation, residual stress, and the like, and molding problems such as defective dropping and damage of the molded product. The present invention relates to an injection mold (hereinafter referred to as “mold”) in which no occurrence occurs.
[0002]
[Prior art]
In injection molding, the resin injected into the cavity is cooled and solidified there, then released from the fixed mold by mold opening and once left on the movable mold, and then when the mold is further opened, it enters the movable mold. Usually, the ejector pin is pushed by the provided ejector pin and is ejected at the same time as it is released from the movable mold, and falls between the fixed mold and the movable mold.
[0003]
In general, the mold for injection molding has a mirror-like finish on the entire inner surface of the cavity so that a molded product having a good surface condition can be obtained. Furthermore, depending on the molding material used, hard chrome plating may be applied. Further, the die is usually given a draft so that the molded product is easily released.
[0004]
However, in the case of a molded product having a small thickness with respect to the projected area, such as an optical disk or a magnetic disk, it is difficult to provide a draft, and it is difficult to uniformly eject the ejector pins when the mold is opened. As a result, warpage and deformation may occur and a product with good appearance and dimensions may not be obtained, or residual stress may occur and desired strength and optical performance may not be obtained.
[0005]
For example, as shown in FIG. 1, in the case of a molded product M1 in which crosspieces R1 having the same shape and the same height are provided on both sides across the parting surface PL, When molding is performed using a mold whose entire inner surface is mirror-finished or plated, the frictional resistance between the cooled and solidified molded product M1 and the cavity inner surface parallel to the mold opening / closing direction when the mold is opened ( (Hereinafter referred to as “mold opening resistance”) is almost equal on both sides of the parting surface PL. As a result, the molded product M1 is not necessarily released first from the fixed mold and remains on the movable mold, but remains on the fixed mold and does not drop, or the protrusion is incomplete and between the fixed mold and the movable mold. There are cases where troubles such as crushing while being pinched and damage to the mold occur.
[0006]
Further, as shown in FIG. 2 such as a part and b part, a molded product in which crosspieces R2 are provided in a lattice pattern on the same side of the parting surface PL, or with a very uneven interval, or the parting surface PL In the case of a molded product M2 in which the distance between the opposite crosspieces R2 on both sides is extremely uneven, if the mold is made using the same mirror finish or plating finish on the entire inner surface of the cavity, the mold opening resistance will be reduced. Due to non-uniformity in parting surface PL or uneven mold opening resistance at opposite positions on both sides of parting surface PL, excessive force, bending moment, and twisting are applied to each part of molded product M2. The moment acts to warp the molded product M2, cause appearance defects such as deformation, residual stress, etc., or cause troubles as described above during mold release.
[0007]
Therefore, in order to solve such problems in the molding of optical disks and magnetic disks, a mold release vacuum breaking means for sending compressed gas to the mold boundary surface of the molded product in the cavity part at the time of mold opening process or mold opening completion. An injection molding apparatus (see JP-A-6-170898), an ultrasonic peeling apparatus (Japanese Utility Model Laid-Open No. 62-111814) for releasing a mold from a mold by intermittently applying ultrasonic vibration to a molded product after molding. Reference) and the like.
[0008]
However, the injection molding apparatus described in JP-A-6-170898 and the ultrasonic peeling apparatus described in Japanese Utility Model Laid-Open No. 62-111814 have a complicated structure and are relatively simple such as a disk shape or a cylindrical shape. It can be applied to a molded product having a shape or structure, but it is applicable to the manufacture of a molded product having a complicated shape or a non-uniform shape such as the molded product M1 shown in FIG. 1 or the molded product M2 shown in FIG. There is a problem that it is difficult.
[0009]
In addition, there may be a difference in draft angle to provide a part that is easy to release and a part that is difficult to release, but there is a problem that it is not an effective means in the case of a molded product that is difficult to give a draft.
[0010]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described problems of the prior art, and even when a molded product having symmetrical shapes on both sides of the parting surface is molded, the molded product remains in the stationary mold and falls. The purpose is to provide a mold that does not cause troubles such as failure to occur or improper protrusion, which remains between the fixed mold and the movable mold and is pinched and crushed or the mold is damaged. .
[0011]
In addition, even when molding a molded product in which the shape and arrangement on one side of the parting surface are significantly unbalanced, or a molded product in which the shapes at opposite positions on both sides of the parting surface are significantly different, the molded product warps, deforms, It is an object of the present invention to provide a mold that does not cause residual stress or the like and does not cause the above-described molding trouble and has a simple structure.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the mold according to the first aspect of the present invention is characterized in that a finish is applied to the entire or part of the cavity inner surface parallel to the mold opening and closing direction.
[0013]
The metal mold of the present invention according to claim 2 is characterized in that a finish finish is applied so that the movable mold full opening resistance is larger than the fixed mold full opening resistance.
[0014]
The mold according to the first aspect of the present invention is characterized in that the inner surface of the cavity of the movable mold or the fixed mold is subjected to a ground finish having a different surface roughness so that the mold opening resistance is different. And
[0015]
In the present invention, the surface finish means “non-directional matte surface finish with an evenly roughened surface” (see JIS-H-0201 “aluminum surface treatment terminology”) or “mechanical or chemical, etc. "The method of roughening the surface" (refer to JIS-H-0400 "Aluminum surface treatment terminology").
[0016]
Examples of the mechanical finishing method include cutting with a machine tool, grinding, sanding, sandpapering, sandblasting, shot peening and the like. Further, as a chemical finishing method, etching is usually performed, but additional surface processing such as various plating processing and resin processing may be further performed thereon.
[0017]
Also, the finish can be made to have any different surface roughness depending on the part by changing the finishing method, the degree of finishing, and the finishing range.
[0018]
(Function)
According to the present invention, the friction coefficient with the molded product cooled and solidified is adjusted by applying a surface finish with an appropriate surface roughness to an arbitrary portion of the inner surface of the cavity parallel to the mold opening / closing direction. By making the full mold opening resistance of the mold larger than the full mold opening resistance of the fixed mold, the molded product can be surely left on the movable mold first. Further, the mold opening resistance of each of the movable mold and the fixed mold can be made substantially the same depending on the location, so that the cooled and solidified molded product can be released without difficulty.
[0019]
The present invention according to claim 2 forms a molded product M1 in which, for example, as shown in FIG. 1, a grid-like beam R1 having the same shape and the same height is provided on both sides of the parting surface PL. In the case of a mold, the inner surface of the fixed mold is left mirror-finished, and the entire surface of the inner surface of the movable mold has the same surface roughness. By making it larger than the opening resistance, it is possible to ensure that the cooled and solidified molded product M1 remains on the movable mold.
[0020]
In the present invention as defined in claim 1 , for example, as shown in FIG. 2, grid-like bars R2 are provided at asymmetric or non-uniform intervals on the projection surface, and the bars are located at opposite positions on both sides of the parting surface PL. In the case of a mold for molding a molded product M2 having a different number and interval of R2, the molded product M2 can be obtained by applying a surface finish with partially different surface roughness to the cavities of the movable mold and the stationary mold. The mold can be released on the average without causing bending or twisting.
[0021]
As a result, it is possible to prevent the molded product from warping, appearance defects such as deformation, residual stress, or troubles during molding.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings and examples. 3 is a sectional view of a fixed mold and a movable mold of the mold of the present invention for molding the molded article shown in FIG. 1, FIG. 4 (A) is a partial front view of the fixed mold of the mold of the present invention shown in FIG. (B) is a partial front view of the movable mold, FIG. 5 is a sectional view of the mold of the present invention for molding the molded product shown in FIG. FIG. 6 is a front view of a fixed mold of the mold of the present invention shown in FIG. 5, and FIG.
[0023]
Example 1
The mold 1 shown in FIGS. 3 and 4 is symmetrical with respect to the parting surface PL, and has a long side a = 120 mm, a short side b = 90 mm, a thickness h = 20 mm, and a thickness R = 2 mm of the crosspiece R1. This is a mold for molding a molded product M1 made of PMMA as shown in FIG.
[0024]
In the mold 1, the surface roughness of the inner surface 21 of the cavity of the fixed mold 2 and the inner surface 31 of the cavity of the movable mold 3 is 1.6S (maximum height Rmax: 1.6 μm) specified in JIS-B-0601. However, the molded product M1 may remain on the fixed mold 2 when the mold is opened, causing molding trouble.
[0025]
Therefore, the inner surface 21 of the cavity parallel to the mold opening / closing direction of the fixed mold 2 is left as it is in the first mirror finish, and the inner surface 31 of the cavity parallel to the mold opening / closing direction of the movable mold 3 is left as the abrasive of grain size # 36 (JIS- R-6001 (see Abrasive Grain Size)) is used to achieve a surface finish with a surface roughness of 18S (Rmax: 18 μm), and the movable mold 3 has an all-opening resistance of the fixed mold 2 It adjusted so that it might become larger than opening resistance.
[0026]
As a result, the molded product M1 was reliably left on the movable mold 3 when the mold was opened. Next, the product was ejected with an ejector pin in the movable mold, and a good product without appearance defects such as warpage and deformation and no residual stress could be obtained.
[0027]
(Example 2)
The mold 4 shown in FIGS. 5 and 6 has the same long side, short side, thickness, and thickness of the crosspiece as the molded product M1 shown in Example 1 (FIG. 1). As shown in FIG. This is a mold for forming a molded product M2 made of PMMA in which crosspieces R2 are provided in a lattice pattern at asymmetric or non-uniform intervals with respect to the parting surface PL.
[0028]
That is, in the molded product M2, the distance between the upper right portion (a portion) toward the front side (FIG. 2B) is closer than the other portions, and the lower right portion toward the back side (FIG. 2C). The distance between the crosspieces in (b part) is closer than the other parts.
[0029]
In the mold 4, the entire inner surface of the cavity of the fixed mold 5 and the entire inner surface of the cavity of the movable mold 6 were finished to have a mirror surface with a surface roughness of 1.6S. Molding troubles such that the part b is difficult to release from the movable mold 6 and the molded product M2 is warped and bent and further torn off have occurred.
[0030]
Therefore, as shown in FIG. 6 (A), the cavity inner surface 51 in the zone 5a of the fixed mold 5 is left in the first mirror finish, and the cavity inner surface 52 in the zone 5b is used with an abrasive of grain size # 100. Sand blasting was used for a finish.
Further, as shown in FIG. 6B, the inner surface 61 in the zone 6a of the inner surface of the cavity of the movable mold 6 is sandblasted using an abrasive having a particle size # 60, and the inner surface 62 in the zone 6b is made of a particle size # 36. Sand blasting was performed using abrasives to obtain a finish.
[0031]
In this way, in the fixed die 5 and the movable die 6, the mold opening resistance of the part R2 of the molded product M2 is made larger than the mold opening resistance of the part where the crosspiece R2 is relatively dense. The total mold opening resistance of the movable mold 6 was adjusted to be larger than the total mold opening resistance of the fixed mold 5. As a result, when the mold was opened, the molded product M2 was released from the fixed mold 5 on the average and was reliably left on the movable mold 6. Next, it was ejected by an ejector pin in the movable mold 6, and a good product having no appearance defects such as warpage and deformation and no residual stress could be obtained. In addition, other molding troubles did not occur.
[0032]
【The invention's effect】
As is apparent from the above description, the injection mold according to the first aspect of the present invention is configured as described above, so that the mold opening resistance of the cavity inner surface parallel to the mold opening and closing direction is adjusted, thereby First, the molded product is first released from the fixed mold without difficulty, and is reliably left on the movable mold, and then is released from the movable mold on average and is ejected. As a result, it is possible to obtain a good product having no appearance defects such as warpage and deformation, and no residual stress. Moreover, occurrence of molding troubles such as defective dropping, crushing, and tearing of the molded product is prevented.
Furthermore, the surface of the cavity parallel to the mold opening / closing direction need only be finished with an appropriate surface roughness depending on the location, and a complicated shape and driving means are not required, so the structure is simple.
[0033]
In addition, since the injection mold according to the second aspect of the present invention is configured as described above, the molded product that has been cooled and solidified reliably remains on the movable mold. Therefore, occurrence of molding troubles such as defective dropping, crushing, and tearing of the molded product is prevented.
[0034]
In addition, since the injection mold of the present invention according to claim 1 is configured as described above, the molded product that has been cooled and solidified is released on average so as not to be twisted from the fixed mold and the movable mold, warped, It is possible to obtain a good product without appearance defects such as deformation and residual stress.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory view showing an example of a molded product, in which (A) is a side view, (B) is a view taken in the direction of arrow B in (A) (front view), and (C) is in (A). C arrow line view (rear view).
FIGS. 2A and 2B are explanatory views showing another example of a molded product, in which FIG. 2A is a side view, FIG. 2B is a front view, and FIG.
3 is a cross-sectional view of a fixed mold and a movable mold of the mold of the present invention for molding the molded article shown in FIG. 1. FIG.
4A is a partial front view of a fixed mold of the mold of the present invention shown in FIG. 3, and FIG. 4B is a partial front view of a movable mold.
5 is a cross-sectional view taken along the line XX of FIG. 6 of the fixed mold and the movable mold of the mold of the present invention for molding the molded article shown in FIG. 2;
6A is a front view of a fixed mold of the mold of the present invention shown in FIG. 5, and FIG. 6B is a front view of a movable mold.
[Explanation of symbols]
1,4 Injection mold 2,5 Fixed mold 3,6 Movable mold 21 Fixed mold cavity inner surface (mirror finish)
31 Movable cavity inner surface (finished surface with # 36 abrasive)
51 Fixed cavity inner surface (mirror finish)
52 Fixed mold cavity inner surface (surface finish with # 100 abrasive)
61 Movable cavity inside surface (finished surface with # 60 abrasive)
62 Movable cavity inner surface (surface finish with # 36 abrasive)
M1, M2 injection molded product R1, R2 Crosspiece PL Parting surface

Claims (2)

A whole surface or molding die out morphism that have satin finish is applied to a portion of the mold opening and closing direction parallel to the cavity inner surface, as a cavity inner surface of the movable die or the stationary die is the mold opening resistance different, An injection mold characterized in that a random surface finish with a different surface roughness is applied to any part.   2. The injection mold according to claim 1, wherein a finish finish is applied so that the movable mold opening resistance is larger than the fixed mold opening resistance.

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