JPH06155480A - Molding die for plastic molded piece - Google Patents

Abstract

PURPOSE:To obtain a molding die for plastic molded piece capable of filling molding resin at a high speed having high molding precision of the plastic molded piece by accelerating discharge of remaining air. CONSTITUTION:Divided molding dies 2 and 3 divided by multiple division with a divided face 7 capable of releasing a plastic molded piece 1 are respectively made of laminated bodies of unit molding dies 2A and 3A divided by multiple division with a laminated face 8 vertical with respect to the divided faces. Gas vents 11 and 12 having small clearances (for example 10-30mum) are provided on the mating faces 7 and 8 of the laminated bodies.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for a plastic molded product used for manufacturing a plastic molded part of an electric machine tool using an injection molding machine or the like, and in particular, a cavity for enabling high-speed injection molding. The gas venting structure inside.

[0002]

2. Description of the Related Art Molds for plastic molded products are divided into, for example, upper molds and lower molds so that the plastic molded products molded in the internal molding space (cavity) can be released. A cavity is formed by dividing the mold into multiple parts, and forming a molding surface on which the outer shape of the plastic molded product is imprinted, and combining the multiple molds with the dividing faces (matching faces). A molding die for a plastic molded product containing the above is formed.

By the way, in injection molding of a plastic molded product using a mold for a plastic molded product, in order to improve the dimensional accuracy of the plastic molded product, it is effective to increase the fluidity of the resin in the cavity. Therefore, high-speed filling of resin into the cavity is an important issue. High-speed filling is possible by increasing the mold temperature to lower the resin viscosity, increasing the injection pressure to improve the filling speed, and devising the number and arrangement of gates and sub-gates to improve the inside of the cavity. Known methods include reducing the difference in filling time depending on the position and reducing the injection resistance due to the residual air in the cavity by reducing the pressure in the cavity.

[0004]

In the conventional measures for enabling high-speed filling, the filling speed can be improved to some extent by improving the mold temperature, the injection pressure, and the gate structure. However, if the inside of the cavity is depressurized too much, the filling resin will fire, so that the depressurization inside the cavity will be limited. Therefore, the residual air in the cavity is compressed in the process of filling the cavity with the resin at a high speed, and the compressed air is discharged to the outside, for example, through a slight gap (gas vent) in the dividing surface of the molding die. The high speed impedes high-speed filling because the resin in this part lags behind other parts in curing, leaving molding distortion in the plastic molded product, which causes deformation of the plastic molded product after mold release, resulting in dimensional accuracy. The problem of lowering occurs.

An object of the present invention is to obtain a molding die for a plastic molded product, which is capable of high-speed filling and has a high dimensional accuracy of the obtained plastic molded product by promoting discharge of residual air in the cavity.

[0006]

In order to solve the above problems, according to the present invention, there is provided a molding die which is divided into a plurality of division molding dies by a division surface capable of releasing a plastic molding. It is assumed that the split mold is composed of a laminate of unit molds divided into a plurality of laminate planes perpendicular to the division plane, and a gas vent having a minute gap is provided on a mating surface of each laminate.

Further, it is assumed that the minute gap length of the gas vent is in the range of 10 to 30 μm. Further, it is assumed that the mating surface of each laminated body is roughened, and a gas vent having a minute gap is formed in a gap generated by the unevenness. Furthermore, it is assumed that the rough surface on the mating surface of each laminate is simultaneously formed by wire cutting for cutting the split mold into unit molds.

[0008]

In the structure of the present invention, each split mold is a laminate of unit molds divided into a plurality of laminate planes perpendicular to the division plane, and a gas vent having a minute gap is provided on the mating surface of each laminate. By doing so, the residual air compressed by filling the resin into the cavity at high speed is discharged to the outside through the gas vents formed by being dispersed in various places in the cavity, so that the compressed air is not discharged. The function of eliminating the injection resistance of the resin caused by the delay can be obtained, the resin can be filled into the cavity at high speed, and the deformation amount of the plastic molded product can be reduced.

If the minute gap length of the gas vent is set within the range of 10 to 30 μm, the resin is prevented from entering the gas vent due to the difference in viscosity between the residual air and the molding resin, and only the residual air is discharged to the outside. The function is obtained. Furthermore, if the mating surface of each laminated body is roughened and a gas vent consisting of minute gaps is formed in the gap created by the unevenness, a gas vent with a maximum gap length of 10 to 30 μm can be processed simply by roughening the surface. Can be easily formed.

Furthermore, if the rough surface on the mating surface of each laminate is formed at the same time by the wire cutting process for cutting the split mold into the unit molds, the gas vent is formed simultaneously with the cutting process of the unit molds. As a result, it is possible to obtain a function that greatly saves the die machining.

[0011]

EXAMPLES The present invention will be described below based on examples. FIG. 1 is a development view schematically showing a molding die for a plastic molded article according to an embodiment of the present invention, taking a trip crossbar of an auto breaker as an example. In the figure, a trip crossbar -1 as a plastic molded product has a complicated shape, but the molding die for the plastic molded product has upper and lower split molds 2 and 2 divided by a dividing surface 7 capable of releasing the mold. It consists of three. Further, the upper die 2 is divided into a plurality of unit molding dies 2A, 2 by a lamination surface 8 perpendicular to the division surface 7.
B, 2C, and the like, and the lower mold 3 is also divided into a plurality of layers at a lamination surface 8 perpendicular to the dividing surface 7 to form a unit molding die 3A, 3B, 3C, etc. (Mating surface) 7 has a gas vent 11 consisting of a minute gap
However, gas vents 12 each having a minute gap are formed on the unit-type laminated surface (matching surface) 8.

The unit molds adjacent to each other are divided into parts having the same cross section of the plastic molded product, and the molding surface 6 thereof corresponds to the contour of the part of the plastic molded product 1 having the same cross section. , Two-dimensional curved surface,
Alternatively, the molding position 6 can be easily formed by cutting the plate-shaped unit molding material along the contour of the plastic molded product 1 by determining the dividing position so as to become the connecting surface.

FIG. 2 is a perspective view showing a gas vent in the embodiment with respect to a unit molding die.
The case where it is provided in a part in contact with is shown as an example. When formed in this way, the dimensional accuracy of the unit molding dies in the stacking direction and the dimensional accuracy of the mold dividing surfaces can be accurately maintained by the unit mating surfaces and the split mold mating surfaces that do not process the gas vents 11 and 12. Further, if the minute gap length of the gas vent is set within the range of 10 to 30 μm, the resin is prevented from entering the gas vents 11 and 12 due to the difference in viscosity between the residual air and the molding resin, and only the residual air is discharged to the outside. A transparent function is obtained. Further, as a method for processing the gas vent, any of a mechanical polishing method, a surface roughening method such as sandblasting, an electric discharge machining method, an etching machining method, or an electrolytic polishing method may be used.

In particular, according to the surface roughening method, the dimensional accuracy of the molding die is maintained by the convex portions dispersedly formed on the rough surface, and the recesses formed by communicating between the convex portions are formed. Since the gas vent consisting of minute gaps is formed, the gas vents 11 and 1 having a desired minute gap length depending on the surface roughness of the processed surface.
2 can be easily formed over part or all of the mating surfaces of each laminate.

On the other hand, when the wire cutting process is used to cut the split molds 2 or 3 into unit molds, the cutting surface becomes rough, so that the unit molds are cut at the same time. Because it can form a gas vent,
The advantage is that die machining can be significantly labor-saving and time-saving. FIG. 3 is a perspective view showing an assembling method of a molding die for a plastic molded product according to an embodiment. A plurality of divided unit molding dies are housed in a frame-shaped mold holder 9 and fixed by screws 10. A split mold 2 (upper mold) formed of a laminate of unit molds is formed, and a split mold 3 (not shown) is formed.
The same applies to the (lower mold). The upper mold and the lower mold thus formed are matched in the die set 20 at their dividing surfaces to form a molding die for a plastic molded product containing a cavity.

The cavity of the mold for the plastic molded product formed as described above is filled with resin at a high speed and opened.
As a result of injection molding the trip crossbar-1 of the breaker, the amount of deformation of the obtained plastic molded product at both axial ends was 0.1 to 0.2 mm. In addition, the upper mold 2 and the lower mold 3 are integrated into each other by using a conventional molding die for plastic molded articles, and a trip crossbar of an auto breaker is used.
As a result of injection molding No. 1, the amount of deformation at both ends in the axial direction of the obtained plastic molded product was as large as 1.5 to 2.0 mm. From this result, the high-speed filling effect of the resin in the mold for the plastic molded product of the example was verified.

[0017]

As described above, according to the present invention, the split mold is a laminate of a plurality of unit molds, and the laminated surface has 10 to 30 μm.
A gas vent having a minute gap length of m 3 was provided. As a result, the residual air in the cavity can be easily discharged, enabling high-speed filling of molding resin, which was difficult in the past.
It is possible to provide a molding die for a plastic molded product with a high molding accuracy that can be reduced to about 10.

Further, a great economic effect is obtained such that the cost and time required for the mold improvement such as the additional processing of the subgate and the adjustment of the mold temperature and the injection pressure, which have been conventionally required for improving the molding accuracy, are unnecessary. was gotten.

[Brief description of drawings]

FIG. 1 is a development view schematically showing a molding die for a plastic molded product according to an embodiment of the present invention, taking a trip crossbar of an auto breaker as an example.

FIG. 2 is a perspective view showing the gas vent in the embodiment with respect to a unit molding die.

FIG. 3 is a perspective view showing an assembling method of a molding die for a plastic molded article according to an embodiment.

[Explanation of symbols]

 1 plastic molded product (trip crossbar) 2 split mold (upper mold) 2A unit mold 3 split mold (lower mold) 3A unit mold 6 molding surface 7 mold split surface (matching surface) 8 unit mold laminated surface (Mating surface) 9 type holder-10 Screw 11 Gas vent (division surface side) 12 Gas vent (stacking surface side) 20 Die set

Claims (4)

[Claims] 1. A molding die divided into a plurality of division molding dies at a division surface capable of releasing a plastic molded product, wherein each of the division molding dies is divided into a plurality of lamination surfaces perpendicular to the division surface. A molding die for a plastic molded article, comprising a laminated body of unit molding dies, and a gas vent having a minute gap on the mating surface of each laminated body. 2. The minute gap length of the gas vent is 10 to 30.
The mold for a plastic molded article according to claim 1, which is in the range of μm. 3. The plastic molded product according to claim 1 or 2, wherein a mating surface of each laminate is roughened, and a gas vent consisting of a minute gap is formed in a gap generated by the unevenness. Mold for use. 4. The molding for a plastic molded product according to claim 3, wherein the rough surface on the mating surface of each laminate is formed at the same time by a wire cutting process for cutting the split molding die into unit molding dies. Type.