JP2579860Y2 - Mold for thin plate injection molding - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a gate of an injection mold.

[0002]

2. Description of the Related Art Conventionally, when a flat plate is formed by injecting a resin, various gate systems are used according to the size, shape, and required dimensional accuracy, but a thin (3.0 mm or less) large product (200 cm ² At this point, the gate exceeds the flowable range of the resin at one point and does not reach the end of the cavity and is not filled. Therefore, the multipoint dispersed gate method is adopted.

For example, as shown in FIG. 2A, an upper mold 3 including two split molds 3a and 3b is disposed on a lower mold 2 having a cavity 1 equal to the outer shape of a flat plate to be molded. The molten resin 6 is injected into the cavity 1 from the gate 5 through the runner 4 in the upper mold 3 and, after cooling, the upper mold 3 is pulled up as shown in FIG. Since the cooling resin is cut and separated at the tip of the lower mold 2, the flat plate 9 formed by the push-up pins 8 of the lower mold 2 is pushed up from the lower mold 2 and taken out. The reason why the upper mold 3 is divided is to remove the cooling resin in the runner 4.

In this case, as shown in FIG. 3 (a) showing the molten resin being injected and FIG. 3 (b) showing the flat plate being taken out, the position of the formed flat plate 9 corresponding to the gate is enlarged. A trace 10 protruding from the surface of the flat plate is generated. To sufficiently Yukiwatara the molten resin 6 to the end of the cavity 1 in the lower die 2, first of all, as far as possible the gate tip 7
It is necessary to increase the cross-sectional area of the injection port, but if it is too large, in order to take out the cooled flat plate 9, a large force is required to cut the cooling resin at the tip of the gate, making separation difficult. since there is a possibility that traces 10 directly under the gate becomes large, from the viewpoint of practical use, typically, the gate tip 7
The diameter of the injection port is 0.5
２．０2.0 mm.

[0005]

However, when a heat-resistant conductive thin flat plate is formed from a hard-to-flow resin such as a combination of a conductivity-imparting agent and a fibrous reinforcing material, when the performance is required to be high, the flatness is generally increased. The fluidity of the resin suddenly deteriorates, the flow resistance of the resin at the tip of the gate increases, and there is a possibility that the resin will not sufficiently spread to the end of the cavity. Also be modified to reduce the resistance of the gate position by increasing the cross-sectional area of the injection port of the gate tip, the cutting force at the gate position when taking out the molded flat plate, the cross-sectional area of the exit of the gate tip And the separation becomes difficult. In addition, an extra step may be required to remove the traces 10 protruding from the surface of the formed flat plate 9.

[0006]

The present invention SUMMARY OF THE INVENTION intended to solve the above problems, this is a mold for molding a thin plate by injection flame fluid resin into the cavity, said thin
At least one cavity surface that forms the main surface of the plate
Pinpoint gate for resin injection (hereinafter simply referred to as
Knife-edge projection around the tip)
In a direction perpendicular to the cavity surface.
The present invention provides a thin plate injection molding die characterized by being provided so as to protrude inside, and is particularly suitable for molding a hard-to-flow resin containing a fibrous reinforcing material.

Hereinafter, the present invention will be described in detail with reference to the drawings. In FIG. 1A, a thin plate of a split mold 3a of the upper mold 3 is shown.
5 provided on the cavity surface forming the main surface of
Is provided around the tip of the cutting die 3a, which is perpendicular to the cavity surface of the split mold 3a.
Protrudes into the cavity 1 in direction. Then, after injecting the molten resin 6, it is cooled and the split mold 3a and the lower mold 2 are released,
When the molded flat plate 9 is taken out, as shown in FIG. 1 (b), even if the cooling resin is cut and separated at the tip of the gate to leave a trace 10, it does not protrude from the surface of the flat plate 9, so a step of particularly removing it is necessary. And not.

According to the invention of the present application, by using a mold having such a knife-edge-shaped projection 7a, the molded flat plate 9 is formed near the knife-edge-shaped projection 7a by a sudden change in the flow of the molten resin. Since it has a large resin orientation stress and a notch effect appears in this part, it can be easily cut and separated with a small amount of force. Therefore, polystyrene (PS), polypropylene (PP), Resin such as polycarbonate (PC), glass fiber (GF), carbon fiber (CF)
Even hard-flowing resin blended with fibrous reinforcement such as
The cross-sectional area of the gate 5 can be made relatively large, the resistance at the time of cutting the gate can be minimized by the notch effect, and the fillable range per gate can be maintained to the maximum.

The molten resin flows from the gate 5 into the cavity 1 as shown by an arrow in FIG. 1A, but the resin containing the reinforcing material or the like tends to be oriented in the flow direction. In particular, in the vicinity of the knife-edge-shaped protrusion 7a formed around the tip of the gate, the resin flowing downward through the gate 5 suddenly changes its flow direction upward along the knife-edge-shaped protrusion 7a, so that the notch is formed. Becomes Also, since the tip of the gate 5 is oriented parallel to the surface of the cavity 1, the gate 5
The resin is oriented parallel to the surface of the flat plate 9 around the tip of the flat plate 9, in particular, directly below the gate 5. When the split mold 3a of the upper mold 3 is pulled up in such an oriented state, the cutting by the notch effect is started, and the resin immediately below the gate 5 is also cut off. Thus, the cooling resin immediately below the gate 5 can be easily separated.

[0010]

(Example 1) PC in a cavity of a mold provided with a gate (gate diameter 1.5 mm, height of a knife-edge-shaped protrusion 0.5 mm, diameter of a bottom 2.0 mm) of the present invention. When a hard-flowing resin in which fibrous reinforcing materials such as GF and CF are variously mixed within a range of 5 to 50% is injected at three points, a diameter of 255 mm and a thickness of 1.0 to 2.0 mm are obtained. Unfilled part of disk
It could be easily formed without any.

Comparative Example 1 An attempt was made to form a disk in the same manner as in Example 1 except that a mold having no knife-edge-shaped protrusion was used for comparison. In this case, the gate resistance is large and the end of the cavity is not filled, and in order to avoid such unfilling, a large injection pressure is required for molding,
Moreover, large distortion remained on the disk, and good molding could not be performed. In this case, in order to perform good molding, three gates having a gate diameter of 2 mm had to be provided, and the thickness of the disk had to be considerably increased (3.5 mm or more).

[0012]

According to the present invention, the thickness is 0.5 to 3.0.
Even when a large flat plate with a small thickness of 2 mm is molded from a hard-to-flow resin, no unfilled portion is generated with the minimum number of gates.
Ku can be easily injection molded only can the resin in distortion to reduce the gate resistance is small.

[Brief description of the drawings]

FIG. 1 shows the operation of the upper and lower molds near the gate according to the present invention.
FIGS. 4A and 4B are partially enlarged longitudinal sectional views illustrating a state, in which FIG. 4A shows a state during resin injection and FIG .

FIG. 2 illustrates a manufacturing process using a conventional injection molding die .
Part enlarged longitudinal sectional view, (a) represents the end injection molding that,
(B) shows that the flat plate is being removed.

FIG. 3 illustrates an operation state near a gate of a conventional upper and lower mold.
In partial enlarged longitudinal sectional view of a light, (a) shows the resin injection,
(B) shows that the flat plate is being removed.

[Explanation of symbols]

1 cavity 6 push up the molten resin 2 lower mold 7 gate tip 3 upper mold 7a knife-edge-like projections 3a split mold 8 the pin 3b split 9 flat 4 runners 10 traces fifth gate

Claims (2)

(57) [Scope of request for utility model registration] 1. A mold for molding a thin plate by injecting a hard-flowing resin into a cavity , wherein a main surface of the thin plate is formed.
Formed on at least one of the cavity surfaces
Around the tip of the resin injection pinpoint gate
The edge-shaped protrusion is oriented at right angles to the cavity surface.
A thin plate injection molding die, which is provided so as to protrude into a cavity . 2. The thin plate injection molding die according to claim 1, wherein said hard-flowable resin containing a fibrous reinforcing material is formed into a thin plate.