JPS6121820B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an injection mold for plastic processing. A groove 22 is provided around one of the templates 4, and a knife edge 1 faces the inner surface of the groove 22.
9 into the groove 22 of the fixed side mold plate 3 and the movable side mold plate 4.
This invention relates to an injection mold characterized in that a mold is provided around the other side of the mold that is not provided.

Conventionally, in injection molding processes, excess material flows out as burrs mainly around the periphery of the molded product. This resulted in a loss of material and required secondary processing to remove burrs, resulting in a significant loss in terms of time and man-hours.

The causes of burrs include, for example, poor mold finishing accuracy, low mold strength and deformation due to injection pressure, insufficient mold clamping force, high injection pressure, and poor material fluidity. Various causes can be considered, such as if it is too good, if the injection amount is too large, etc. In terms of actual molding processing, in order to obtain a completely expanded molded product, it is necessary to remove air, water vapor, and generated gas contained in the material. A vent must be provided in the mold. If a vent is installed, the material will overflow along with the gas.
This will lead to the occurrence of burrs. Therefore, in order to obtain a perfect molded product, it has become essential to generate a minimum amount of burrs.

The present invention has been made in consideration of the above-mentioned points, and an object of the present invention is to provide sufficient degassing in plastic injection molding, as well as to almost eliminate the occurrence of burrs, thereby improving the cavity. An object of the present invention is to provide an injection mold in which excess material overflowing from a parting surface onto a parting surface can be reduced.

The present invention will be explained in detail below with reference to Examples. FIG. 1 illustrates an embodiment of the injection molding die according to the present invention, and FIG. 2 shows the injection molding die shown in FIG. 1 in an open state. The injection mold includes a fixed side mounting plate 1, a runner stripper plate 2, a fixed side mold plate 3, a movable side mold plate 4, a receiving plate 5, a spacer block 6, a movable side mounting plate 7, and a core 8. It is composed of etc. A sprue bush 9 is fitted in the center of the fixed side mounting plate 1, and the sprue bush 9 is provided with a sprue 10 for injecting plastic whose diameter increases downward as shown in Fig. 1. ing. In addition, guide pin holes 11 are drilled at the end of the fixed side mounting plate 1 so that the runner stripper plate 2, fixed side template 3, movable side template 4, and receiving plate 5 can be assembled accurately. 12 is inserted. Furthermore, the fixed side mounting plate 1 and the runner stripper plate 2 are connected by fitting a runner lock pin 13 and a strip bolt 14 so that they can be separated and accurately positioned. A recess 15 is provided in the center of the runner stripper plate 2, into which the tip of the sprue bush 9 can be fitted. A runner 1 is placed on the upper surface of the fixed side template 3 as shown in Fig. 2.
A gate 18 is further bored in a part of the runner 16, and the gate 18 is connected to the upper mold 17 on the lower surface and becomes smaller in diameter toward the bottom. The upper mold 17 has a mold formed on the lower surface of the stationary mold plate 3 along the upper surface of a predetermined plastic molded product, and has a triangular cross section on the outer periphery of the upper mold 17 as shown in FIGS. 2 and 3. A shaped knife edge 19 extends smoothly and integrally downward. A core 8 is fitted into the center of the movable template 4 in a replaceable manner. The core 8 has the upper mold 17
A lower die 20 is provided protrudingly so as to be able to fit into the upper die 17 and the lower die 20, and a cavity is formed so that plastic material can be poured into the gap between the upper die 17 and the lower die 20 through a gate 18 to form a plastic molded product in a predetermined shape. 21
We are trying to form a As shown in FIGS. 2 and 3, a groove 22 is provided around the outer circumferential side of the lower mold 20 that protrudes above the movable mold plate 4, and the inner peripheral surface of the groove 22 and the upper mold 17 The knife edge 19 is adapted to face and fit into the inner circumferential surface of the knife edge 19 . Further, a protruding pin hole 23 for separating the plastic molded product is bored in the middle part of the core 8, and a protruding pin 24 is inserted therein so as to be able to protrude freely. A receiving plate 5 is in contact with the lower surface of the movable mold plate 4, and a spacer block 6 is provided at the end of the receiving plate 5, and a support 25 is provided in the center.
is installed and the movable side mounting plate 7 is attached. 2
6 and 27 are protruding plates, and 28 is a guide support. Furthermore, each of the runner stripper plate 2, the fixed mold plate 3, the movable mold plate 4, and the receiving plate 5 is connected to one end surface thereof by a tension link 29 so as to be detachable and detachable.

Then, arrange each injection mold as shown in FIG.
Position it with
0 to connect the runner stripper plate 2 to the fixed side mounting plate 1, and after achieving the sealed state shown in Fig. 1 as specified, the movement of the movable side mounting plate 7 is stopped and the mold is tightened. Bring the pressure to zero or very low. While injection is started and the molten material flows into the cavity 21 via the spray 10, runner 16, and gate 18, the mold clamping pressure is maintained at zero or slight pressure. Therefore, the gas contained in the molten material is released from the parting surface 31 to the outside. At this time, the movable mold plate 4 and the core 8 are slightly pushed open according to the gas pressure, allowing for sufficient gas release. When the cavity 21 is almost filled with the molten material, sufficient clamping pressure is applied to mold the molten material into a predetermined shape.

In the above molding, the groove 22 is provided around the parting surface 31 on the upper surface of the core 8, and the knife edge 19 is provided around the lower surface of the corresponding fixed side mold plate 3, so that the molten material flows into the cavity 21. During this period, gas is fully vented from the parting surface 31, and due to the structure shown in Figure 3, there is almost no overflow of burrs from the molded product even when sufficient mold clamping pressure is not applied. This is something that can be done. Therefore, it is possible to reduce excess material overflowing from the cavity onto the parting surface, and also to reduce the time and effort required for deburring after molding.

Depending on the shape of the molded product, the groove 22 may be provided on the stationary template 3 and the knife edge 19 may be provided on the movable template 4.

As described above, the present invention provides a concave groove on the peripheral edge of the cavity formed by the fixed side template and the movable side template, and Since the knife edge that faces the inner surface of the groove is placed around the fixed side mold and the movable side mold plate, the other side that does not have a concave groove around it, it can be formed when the fixed side mold plate and the movable side mold plate are matched. During the period in which the molten material flows into the cavity, the gas contained in the molten material passes between the inner surface of the groove and the knife edge and is sufficiently extracted from the parting surface. By applying sufficient mold clamping pressure of the side mold plate, the knife edge can be slid on the inner surface of the concave groove to form the mold. At the same time, material leaked from the mold, but in the present invention, it is possible to completely eliminate burrs leaking from the cavity to the parting surface, thereby saving molding material and reducing the trouble of deburring after molding. This is something that can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of an embodiment of the present invention, FIG. 2 is an exploded side sectional view of the same, and FIG. 3 is an enlarged sectional view of part A in FIG. , 4 is a movable template, 19 is a knife edge, 21 is a cavity, and 22 is a groove.

Claims (1)

[Claims] 1. A groove is provided around the periphery of the cavity formed by the fixed side template and the movable side template on either the fixed side template or the movable side template, and the inner surface of the groove is faced. An injection mold characterized in that a knife edge is provided around the other of the fixed side mold plate and the movable side mold plate, the other of which does not have a groove around it.