JPH0655580A - Injection molding equipment - Google Patents

Abstract

PURPOSE:To inhibit defective appearance and the generation of molding strains in a molding die with a resin flow-adjusting mechanism adjusting the flow of a resin. CONSTITUTION:A resin flow-adjusting mechanism is formed in a resin flow path from a runner 15 to a ring gate 18, and composed of one or the combination of a mechanism by the change of the sectional area of a ring runner 16, the variation of the height of the bank of the ring runner 16 and the alteration of the width of the bank of the ring runner 16 and a mechanism by the eccentricity (or the eccentricity of a stationary side mold) of a stationary-side core pin 14 in a vertical ring runner 17, and flows, in which a resin simultaneously reaches each section of a ring gate 18 by utilizing flow path resistance, are formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding apparatus which suppresses appearance defects and molding distortion of a molded product due to weld lines and flow marks of the disk-shaped molded product. For example, the present invention relates to an injection molding apparatus capable of high-accuracy and high-rigidity molding without appearance defects such as a high-density information recording medium such as a video disc and a digital audio disc.

[0002]

2. Description of the Related Art For a mold in an injection molding machine,
How to attach a gate is an important issue in molding. The flow of the molten resin in the cavity of the mold changes depending on the shape, size, number, position, etc. of the gate. Therefore, the filling state of the molten resin directly affects the quality of the molded product such as rigidity, deformation, appearance, precision, and molding shrinkage.

The appearance defects that occur in the molded product include weld lines, flow marks, and peeling. The weld line is a thin wire formed at a portion where two or more flows of the molten resin that are press-fitted in the cavity of the mold join. This weld line is generated because the welded resins do not sufficiently melt due to a decrease in the temperature of the tip portions of the resins. Therefore, it can be made relatively unnoticeable by adjusting the molding conditions such as raising the resin temperature or raising the mold temperature.

However, when the ratio between the thickness of the molded product in the cavity and the distance to the confluence point becomes large, it becomes remarkable. Furthermore, it is difficult to eliminate the problem by adjusting the molding conditions in the case of a material having a low fluidity in which a reinforcing agent such as a resin filler is mixed.

Flow marks are used for molded products with complicated shapes,
In the case of a thin molded product, when the molten resin flowing in the cavity is press-fitted, it is generated by the flow resistance with the mold wall surface. Pressure drop in the cavity due to high injection pressure,
Although it is caused by the viscosity change between the molten resin and the wall surface of the mold, it is difficult to eliminate it by adjusting the molding conditions, although measures are taken as with the weld line.

When the projected area of the molded product is large with respect to the thickness, it is difficult to pressure-fill the cavity with resin in a short time, and a plurality of gates are provided. However, it causes weld lines and flow marks. Therefore, methods such as providing an air vent at the confluent portion of the molten resin to quickly escape air and volatile matter in this portion, or providing a material pool at the location where the weld is generated and transferring the weld to this portion and cutting it away later are possible methods. Although it is carried out, it is not always effective enough.

The applicant of the present invention has proposed a ring gate system (Japanese Patent Laid-Open No. 59-143622) as a technique for solving such a problem.
No.) was invented. This ring gate method
Since the gate is concentric with the cylindrical part to be molded and has a ring-shaped cross section, it is most suitable for molding small cylindrical parts with high precision. However, it is not sufficient to cover all thin-walled parts, large projected area parts, large parts, or higher quality parts. For high-density recording media represented by thin-walled and wide-projection area molding, precise pits and track pitches are required, and a mold that enables high-precision molding without molding distortion or peeling during mold release is desired. It is rare.

[0008]

The present invention has been made in view of the above circumstances, and in a molding die of an injection molding apparatus, a resin flow is made uniform in a resin flow path between a runner and a ring gate. It is an object of the present invention to provide an injection molding apparatus in which the appearance defect and the molding distortion of the molded product due to the weld line and the flow mark are suppressed by providing the resin rectifying mechanism.

[0009]

The injection molding apparatus of the present invention is a molding die in which a runner and a ring gate are connected by a resin flow path by a ring runner and a vertical ring runner. A resin rectifying mechanism for making the amount of resin flowing out from the ring gate substantially uniform over the entire circumference of the ring gate is provided.

The configuration of the resin rectifying mechanism of this injection molding apparatus is for continuously changing the flow passage cross-sectional area of the ring runner. Furthermore, the structure of the resin rectifying mechanism is a ring-shaped bank provided on the inner peripheral portion of the ring runner,
The height or width of the bank is continuously changed. Furthermore, the resin rectifying mechanism continuously changes the flow passage cross-sectional area of the vertical runner, and is formed by the eccentricity of the fixed-side core pin forming the inside of the vertical runner.

That is, by substantially equalizing the flow of resin from the runner of the molding die to the ring gate, a plurality of gates are not used, and a thin molded product having a large projected area and a precise molding strain It enables the molding of a few highly rigid molded products.

By configuring the resin rectifying mechanism before the resin flows out from the runner through the ring gate, it is possible to avoid a time lag before reaching all the corners of the molded product, and press-fit or join the resin substantially uniformly. Can be made.

Although the viscosity of the molten resin varies depending on the type and grade of the resin, and also varies depending on the resin temperature, by combining any one or a plurality of the above-mentioned resin rectifying mechanisms, each ring gate The flow of the resin that reaches the parts at the same time can be made, and the optimum resin rectifying mechanism can be selected.

[0014]

In the injection molding apparatus of the present invention, the resin flow-out mechanism is used between the runner of the molding die and the ring gate, and the resin is simultaneously discharged from each part of one ring gate to one molded product. Let The resin that flows out from the ring gate to every corner of the molded product is press-fitted under substantially uniform conditions,
The molten resin does not merge and no weld line is generated.

Since the conditions such as viscosity, temperature and pressure of the molten resin flowing out from the ring gate to the molded product are substantially the same, there is no deviation in the flow resistance between the molded product and the wall surface of the mold, and the thickness of the thin molded product Since the densities in the direction and the flow direction can be made uniform, the generation of flow marks is prevented, the generation of molding distortion is suppressed, and the appearance and quality of the molded product are further improved.

A high-rigidity molded product or a high-density molded product requires a large injection molding machine and a high-strength mold, and requires a long holding time, but the resin flow resistance from the ring gate is uniform. By this, the friction on the wall surface of the flow path of the molded product can be reduced, and the resin density between the wall surfaces is made uniform, so that a dense layer is formed. Therefore, a large-sized molded product having high strength can be molded and a precise molded product can be molded.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. The molded product will be described by taking a disk (hereinafter abbreviated as a disk) of a high density information recording medium as an example.

FIG. 1 is a sectional view showing a mold of an injection molding apparatus which is an embodiment of the present invention. 1 is a fixed side mounting plate, 2 is a stripper plate, 3 is a fixed side mold, 4 is a movable side mold,
Reference numeral 5 is a movable side receiving plate, 6 is a pedestal, and 7 is a movable side mounting plate.

First, the movable side will be described. A cavity 11 corresponding to a molded product disk is formed in the movable mold 4 and a positioning guide pin (not shown).
Is provided. A movable side core pin 24 is provided at the center of the disc formed in the cavity 11 and abuts the fixed side core pin 14, and a fitting hole formed through the movable side mold 4 is formed in the bottom face portion 11a of the disc. The ejector pin 10 is disposed through the ejector hole 11c and the ejector hole 11c, and the cavity 1 is moved by a pin driving device (not shown).
It is configured to project to 1. When the cavity 11 is designed so as to be separated from the sprue 12 and a large number of cavities, the sprue ejector pin 13 is replaced by the ejector pin 10.
It is appropriately arranged with the same configuration. The movable side mold 4 is arranged on a movable side receiving plate 5, and the movable side receiving plate 5 is held by a movable side mounting plate 7 via a pedestal 6. Further, the ejector pin 10 and the sprue ejector pin 13 are connected to the ejector plate upper part 8 and the ejector plate lower part 9 and are held on the upper part of the movable side mounting plate 7.

Next, the fixed side will be described. The sprue bush 1 in which the sprue 12 is formed on the fixed side mounting plate 1.
2a and the fixed core pin 14 are attached. The stripper plate 2 is arranged below the fixed-side mounting plate 1 so that the sprue bush 12a and the fixed-side core pin 14 pass through. Further, below the stripper plate 2, a runner 15 communicating with the sprue 12 and a fixed side core pin 14 are provided.
Ring runner 16 formed around the axis 14a of the
And a fixed side mold 3 having a resin flow path coupled thereto by a vertical ring runner 17 communicating with a ring gate 18 formed so as to communicate with a cavity 11 forming a disk of a molded product. The stationary mold 3 is provided with a positioning guide bush (not shown) for guiding the resin from the ring gate 18 to the cavity 11 so as to be disengageable from the positioning guide pin.

An air vent (not shown) is formed on a mating surface of the movable mold 4 and the fixed mold 3, that is, a parting surface 21. The resin flow path formed in the stationary mold 3 is provided with a resin rectifying mechanism 30 that rectifies the flow of resin. Next, the resin rectifying mechanism 30 will be described.

FIG. 2 shows an embodiment in which the resin rectifying mechanism 30 is formed by the ring runner 16. The cross-sectional area V'of the ring-shaped flow passage formed by the runner 15 side of the ring runner 16 and the fixed side core pin 14 is changed, and the cross-sectional area V'on the runner 15 side is a ', b', h'in the trapezoidal cross-sectional view. It is set by the numerical selection of. Similarly, the cross-sectional area V on the side opposite to the runner 15 side is also selectively set by a, b, and h, and is formed around the fixed side core pin 14 in the fixed side mold 3. Cross-sectional area V
′ Is made smaller than the cross-sectional area V to reduce the resin flow resistance as it goes deeper than the runner 15. a'and a,
It suffices to change any of the numerical values of b ′ and b and h ′ and h to change the cross-sectional areas V ′ and V, and it is not necessary to change all.

FIG. 3 shows an embodiment in which the resin rectifying mechanism 30 is formed by the bank 23 of the ring runner 16. A bank 23 is provided in the resin flow path communicating from the ring runner 16 to the vertical ring runner 17. The height of the bank 23 formed around the fixed core pin 14 from the runner 15 side of the ring-shaped bank 23 is changed. The height H'on the runner 15 side is made higher than the height H on the depth side of the runner to increase the flow passage resistance. The ring-shaped bank 23 changes the width W ′ on the runner 15 side and the width W on the depth side,
The flow path resistance on the runner 15 side is increased so that W ′> W.

FIG. 4 shows another embodiment in which the ring runner 16 and the vertical ring runner 17 are conically continuous to form a resin rectifying mechanism 30. Fixed mold 3 and fixed core pin 1
The cross-sectional area of the ring runner 16 and the vertical ring runner 17 is changed in the resin flow path formed by 4. That is, the resin is rectified by changing the cross-sectional area of the runner 15 side and the opposite side of the fixed core pin 14 to increase the flow path resistance on the runner 15 side. 5 (a) and FIG.
(B) is an AA sectional view and a BB sectional view of FIG.
4, FIG. 5 (a), FIG. 5 (b) and FIG.
The upper end and the lower end of the fixed-side die 3 connecting the respective axial centers X-X of the fixed-side core pin 14 and the ring gate 18 are O,
If O'is taken, the axis of the mold plate 3 is formed eccentrically by O'to the right side in the drawing from the upper end O of the fixed-side mold 3, and the flow passage cross-sectional area of the line runner 17 on the runner 15 side is a gap T ', t '
Therefore, U'and U formed by T and t are formed on the opposite side of the fixed core pin 14. In this case, if the flow path gaps t ′ and t of the ring gate 18 have the same size,
This is convenient in designing the cavity 11. This is necessary for molded products that are symmetrical with respect to the shaft center, such as disks.

FIG. 7 shows the flow paths U'and U of the vertical runner 17 which are eccentric at the upper end of the fixed mold 3 at the flow path end with the fixed core pin 14, and the eccentric amount s of the fixed core pin 14 is eccentric. Is O'with respect to the axis O-O of the fixed side core pin 14.
It is formed by the deviation from -O. The flow path gap is T '<
It becomes T and is rectified up to the ring gate 18 while suppressing the flow on the runner 15 side. In the figure, the flow path gap T ′ of the fixed core pin 14 is changed from step T to step T, but it is also possible to use a concentric shape with an eccentricity only in the axial center.

Further, as shown in FIG. 4, if the abutting portion between the fixed core pin 14 and the movable core pin 24 is a hemispherical pivot, the centering can be easily performed.

Further, as shown in FIG. 2, a primary gate 15 'having a narrowed portion is provided in the runner 15 between the runner 15 and the ring runner 16. Primary gate 1
The high-pressure and high-speed resin passing through 5'causes a secondary plasticization phenomenon due to shearing heat generation during passing, and the resin viscosity decreases,
It is possible to make the resin wrapping around to the vertical ring runner 17 substantially even.

The injection molding apparatus equipped with the resin rectifying mechanism 30 having the above-described structure is arranged such that the type, grade, and resin of the resin are provided between the spool 12, the runner 15, the ring runner 16, the vertical ring runner 17, and the ring gate 18. Resin can be rectified according to various conditions such as molding temperature and pressure.

A high-precision, thin-walled molded product such as a disc requires a large injection molding machine at high pressure, but a high-quality molded product can be molded with a simple structure. Further, it is needless to say that not only discs but also complicated precision molded products, large molded products and the like can be widely used, and it does not matter whether they are single-piece or multi-piece.

[0030]

According to the injection molding apparatus of the present invention, a resin rectifying mechanism for equalizing the flow of resin is provided between the runner and the ring gate, and the viscosity of the molten resin flowing out from the ring gate to the molded product is Since the conditions such as temperature and pressure are substantially the same, it is possible to prevent the formation of weld lines and flow marks in the molded product and improve the appearance quality. In addition, the friction of the molded product on the wall surface inside the mold can be reduced, and the density between the wall surfaces is made uniform, so that a dense and precise molded product, a large molded product,
A highly rigid molded product can be molded without using an injection molding machine or an expensive mold. Furthermore, since the friction of the molded product on the wall surface of the flow path in the mold is small, peeling of the surface of the molded product does not occur at the time of mold release, and the surface smoothness can be improved. It is possible to easily eliminate the problems in the mold design for the size and various shapes of the molded product.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a mold of an injection molding apparatus that is an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a resin rectifying mechanism which is one of the embodiments of the present invention.

3 is a cross-sectional view of a main part of the ring runner part of FIG.

FIG. 4 is a sectional view showing a resin rectifying mechanism that is an embodiment of the present invention.

5 (a) and 5 (b) are an AA sectional view and a BB sectional view of FIG.

6 and 7 are cross-sectional views of main parts showing different vertical runners of FIG. 4.

[Explanation of symbols]

 2 Stripper plate 3 Fixed mold 4 Movable mold 10 Ejector pin 11 Cavity 12 Sprue 14 Fixed core pin 15 Runner 16 Ring runner 17 Vertical ring runner 18 Ring gate 30 Resin rectification mechanism

Claims (8)

[Claims] 1. A molding die in which a runner and a ring gate are connected by a resin flow passage made up of a ring runner and a vertical ring runner, wherein the resin flow passage contains the amount of resin flowing out from the ring gate. An injection molding apparatus, which is provided with a resin rectifying mechanism for substantially uniformizing the entire circumference of the gate. 2. The injection molding apparatus according to claim 1, wherein the resin rectifying mechanism changes the cross-sectional area of the flow path of the ring runner. 3. The injection molding apparatus according to claim 1, wherein the resin rectifying mechanism is a ring-shaped bank provided on the inner peripheral portion of the ring runner. 4. The injection molding apparatus according to claim 3, wherein the ring-shaped bank has a height that is changed. 5. The injection molding apparatus according to claim 3, wherein the ring-shaped bank has a varying width. 6. The injection molding apparatus according to claim 1, wherein the resin straightening mechanism is a change in the cross-sectional area of the flow path of the vertical runner. 7. The injection molding apparatus according to claim 6, wherein the change in the cross-sectional area of the flow path of the vertical runner is formed by the eccentricity of the fixed-side core pin forming the inside of the vertical runner. 8. The injection molding apparatus according to claim 1, wherein a primary gate is provided between the runner and the ring runner.