JPH03182313A - Manufacture of mold - Google Patents

Abstract

PURPOSE:To obtain a mold having a cavity provided with the same configuration and same size as those of a matrix by a method wherein a cavity of a synthetic rubber mold is filled with inorganic composition poured thereinto, and the composition is cured to manufacture the matrix consisting of the inorganic composition while molten alloy for die casting is cast around the matrix, and thereafter the matrix consisting of the inorganic composition is extracted and removed. CONSTITUTION:A matrix 1, having the same configuration as a product to be molded, is manufactured from the block of ABC resin and the matrix 1 is inserted into a predetermined position in the frame body 2 for a casting mold consisting of acrylic resin or the like as a core to pour liquidous hardening silicone rubber around the core and cure it, then, obtained molded form 3 is cut into two pieces to extract and remove the core or the matrix 1. Next, plaster is poured and filled into the cavity of a silicone rubber molding mold 3, in which the cavity having the same configuration as that of the matrix is formed, to cure it and, thereafter, the plaster is calcined to form a plaster mold 4 having the same configuration as the matrix. Subsequently, the plaster mold 4 is used as a core and zinc alloy 5 for die casting, which is provided with a melting point of 380 deg.C, is pressurized and cast around the core while the mold is cut into two pieces after cooling and the core is taken out. According to this method, the mold may be used as the mold for injection molding while combining the core with a template 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a simple mold for molding made of a die-casting alloy.

[Conventional technology] Conventionally, when manufacturing molds used for injection molding of synthetic resins, etc., the mold is first manufactured using an NG (numerical control) machine tool, etc. based on a mold diagram created from a product drawing. After machining the product part (cavity), injection molding is performed using the mold thus manufactured, the shape of the resulting molded product is measured and evaluated, and the mold is designed based on this evaluation. The modifications have been repeated several times.

[Problems to be Solved by the Invention] However, with this method, although it is possible to obtain a mold with excellent durability of several thousand shots or more, it requires a very large number of shots to manufacture one mold. There were problems in that it required several days and the manufacturing cost was extremely high.

On the other hand, in recent years, the development of new products and prototypes using synthetic resin moldings has progressed, and product cycles have become shorter.As a result, high-mix, low-volume production methods have been adopted in the molded product manufacturing field. This is happening more and more often. Furthermore, requests for modification and remodeling of product shapes are increasing.

Therefore, if a conventional mass production mold manufactured by machining is used as a mold for molding such a product, it will not be cost effective and will lead to an increase in the product price. was there.

Furthermore, molds for prototypes or molds for products with a particularly small number of molded products have traditionally been made by spraying a low melting point alloy onto a product model (matrix) such as a wooden or metal mold. A cavity formed by casting resin containing metal powder is used.

However, the molds manufactured by this method are inferior in properties necessary for a mold, such as pressure resistance, strength, mold releasability, and appearance, so it is difficult to obtain a satisfactory molded product even as a simple mold. It was difficult.

The present invention was made to solve these problems, and is a method for manufacturing a synthetic resin mold that requires fewer manufacturing steps, has good strength, dimensional accuracy, appearance, etc., and is suitable for high-mix, low-volume production. The purpose is to provide

[Means for Solving the Problems] The method for manufacturing a molding die of the present invention includes a step of manufacturing a mother mold of the same shape and size as the product to be molded by machining using hard plastic, and A mold made of plastic is used as a core, and liquid curable synthetic rubber is poured onto the outside of the mold and cured, and then the mold made of plastic is pulled out and removed to form a cavity having the same shape and dimensions as the mold. a step of manufacturing a synthetic rubber mold; a step of injecting and filling a curable wavy inorganic composition into the cavity of the synthetic rubber mold and curing it to manufacture a matrix made of the inorganic composition; After casting a molten die-casting alloy on the outside of a mother mold made of a material as a core, the mother mold made of the inorganic composition is removed and molded to have a cavity of the same shape and size as the mother mold. It is characterized by obtaining a mold.

In the present invention, the hard plastic for manufacturing a matrix having the same shape and dimensions as the product to be molded includes:
Plastic materials conventionally used as engineering plastics can be used, but ABS resin (acrylonitrile -butadiene-styrene copolymer) is preferably used.

Curable liquid silicone rubber can also be used as the curable synthetic rubber that is cast on the outside of such a hard plastic matrix to form an intermediate mold.

Furthermore, injecting and filling into the cavity of this synthetic rubber mold,
As the hardenable liquid heat-resistant inorganic material, gypsum, sand, iron powder, a mixture of ceramic powder and a binder, etc. can be used.

Usually, in these materials, a cured product with high strength can be obtained by performing baking after molding.

Furthermore, the heat-resistant inorganic cured product formed in this way is used as a core, and die-casting alloys that are press-cast on the outside include, for example, alloys mainly containing zinc and aluminum.
The melting point is 380℃ and the mechanical expansion force after casting is 26-34
kg/ms2 alloys can be used.

Commercial products of such alloys include, for example, MAK (trade name) manufactured by Mitsubishi Metal Industries, Ltd.

[Operation] In the method for manufacturing a molding die of the present invention, first, a hard plastic block is machined using an NC machine tool or the like based on a product drawing, so that it has the same shape and dimensions as the product to be molded. A mother mold is produced.

Next, this mother mold is inserted as a core inside a casting frame, and after casting liquid curable synthetic rubber such as liquid silicone rubber on the outside, it is divided into two parts to form a core mother mold. By removing it, the shape is the same as that of the inserted mother mold,
In other words, a synthetic rubber mold having a cavity having the same shape as the product to be molded is obtained.

Next, a liquid curable inorganic composition such as gypsum is injected into the cavity of the resulting synthetic rubber mold, solidified, and then fired to create the same shape as the mother mold again.
That is, a heat-resistant inorganic cured product having the same shape and dimensions as the product to be molded can be obtained.

After that, this hardened product is used as a core, and a flat lead alloy for die casting is pressure cast on the outside of the core, which is split into two parts and the core part is removed and removed, so that the core part forms a cavity. As a result, an alloy mold with high strength, dimensional accuracy, and good appearance can be obtained.

[Example] Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a flowchart showing the steps of an embodiment of the present invention.

In the example, first, based on the drawing of the product to be molded, machining is performed using NC tape using an NC machine tool.
As shown in FIG. 2(a), a mother mold 1 having the same shape as the product to be molded is manufactured from a block of ABS resin.

Next, as shown in FIG. 2(b), this mother mold 1 is pushed as a core into a predetermined position inside a casting frame 2 made of acrylic resin, etc., and liquid curable silicone rubber is applied to the outside thereof. After casting and curing, the obtained cast body 3 is divided into two, and the core matrix 1 is extracted and removed.

Next, gypsum is injected into the cavity of the thus obtained silicone rubber mold 3, which has a cavity in the same shape as the mother mold, and is solidified and fired. Form mold 4. (Fig. 2 (C)) Next, the obtained plaster mold 4 was used as a core, and on the outside thereof, a zinc alloy 5 for die casting with a melting point of 380°C was pressure cast (die cast), and after cooling and hardening, two Break it open and take out the core. (FIG. 2(d)) Finally, finish the outer surface of the mold.

The mold made of zinc alloy 5 for die casting manufactured in this way has good dimensional accuracy and appearance, and has sufficient heat resistance and mechanical strength. It can be used in combination with 6 as a mold for injection molding.

When used as a mold for injection molding, the fixed side mold part 7 and the movable side mold part 8 are used as a pair, and the resin heated and melted in the mold cavity 9 between them is used as a sprue runner. , and is injected and filled through the gate.

In this way, the mold of the example is mainly used as a mold for injection molding, but it requires less man-hours for manufacturing, is inexpensive to manufacture, and can quickly adapt to requests for modification or remodeling of the product shape. Therefore, it is suitable as a mold for high-mix, low-volume production.

In addition, the inner surface of the cavity is smooth and has good mold releasability, so
There is no need to finish the inner surface.

In addition, in the method of the embodiment described above, by manufacturing the ABS resin matrix 1 taking into consideration the draft angle of the molded product, undercut, resin shrinkage rate, etc. Machining of the mold can be omitted, further reducing the number of man-hours.

Furthermore, it is not only possible to directly process the obtained alloy mold to form a cooling medium flow path, but also to add an extrusion function by processing parts other than the mold cavity. .

[Effects of the Invention] As explained above, according to the manufacturing method of the present invention, by pressure casting a zinc alloy for die casting, a cavity having the same shape as the product to be molded is formed, and the strength, dimensional accuracy, appearance, etc. are improved. It is possible to obtain a mold that has good properties and is suitable as an injection mold.

Furthermore, the method of the present invention requires only a small number of manufacturing steps and does not require much cost, so it is useful as a method for manufacturing simple molds for high-mix, low-volume production.

[Brief explanation of drawings]

FIG. 1 is a flowchart for explaining an embodiment of the method for manufacturing a molding die of the present invention, and FIG. 2 is a schematic diagram for explaining the steps of the same embodiment. 1...ABS resin matrix 3...Silicone rubber cast body 4...
...Gypsum mold

Claims (1)

[Claims] (1) A process in which a matrix of the same shape and dimensions as the product to be molded is manufactured by machining using hard plastic, and this matrix made of hard plastic is used as a core, and liquid hardening synthetic rubber is applied to the outside of the core. After casting and curing, the mold made of plastic is removed and removed to produce a synthetic rubber mold having a cavity of the same shape and size as that of the mold, and the inside of the cavity of the synthetic rubber mold is A process of injecting and curing a liquid inorganic composition that can be cured into a mold to produce a matrix made of the inorganic composition, and a process for die casting in which the matrix made of the inorganic composition is used as a core and melted on the outside. A method for manufacturing a molding die, which comprises casting an alloy and then removing a matrix made of the inorganic composition to obtain a molding die having a cavity having the same shape and dimensions as the matrix.