JPH03281311A - Manufacture of mold - Google Patents

Abstract

PURPOSE:To manufacture a new mold or a renewed mold, both having high strength, favorable precision in size and a good appearance, by a simple method and at a low cost by melting a used or unusable mold for die casting alloy under heating and casting the molten mold again under pressure. CONSTITUTION:In the case where a mold 16 for die casting alloy becomes unuseful due to discontinuation of manufacturing products, or it becomes necessary to make the same mold 16 again owing to damage, the used mold is once melted under heating and is used again as an alloy material for die casting. More particularly, the molten alloy 5 for die casting is cast to the outside of a matrix 1 made on the basis of a new product drawing and composed of an inorganic composition, and a new mold 6 is made. On the other hand, when the mold 6 is remade owing to the damage of the same, the new mold 6 can be made based on the original matrix 1 without the need for newly making the matrix 1.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method of manufacturing a simple mold for molding made of a die-casting alloy, and particularly relates to a method of manufacturing a simple mold for forming a die-casting die made of a die-casting alloy that has been previously cast and used. This invention relates to a manufacturing method that aims to recycle molds.

[Prior Art] Conventionally, the manufacturing of molds used for injection molding of synthetic resins, etc. has been based on a mold drawing prepared from a product drawing, and then an NC (
(Numerical control) After machining the product part (cavity) of the mold using a machine tool, etc., injection molding is performed using the mold thus manufactured, and the shape of the resulting molded product is measured and evaluated. The mold is modified several times based on this evaluation.

[Problems to be Solved by the Invention] However, although such a method can produce a mold with superior durability of several thousand to more than enemy shots, it takes many days to manufacture one mold. However, there was a problem in that 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 conventional mass-production molds manufactured by machine processing are used as molds for molding such products, it will not be cost effective and will lead to an increase in product prices. There was a problem.

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. The cavity is formed by casting resin containing metal powder.

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 synthetic resin that is easy to manufacture, can reduce manufacturing costs, has good strength, dimensional accuracy, appearance, etc., and is suitable for high-mix, low-volume production. The object of the present invention is to provide a method for manufacturing a mold for molding.

[Means for Solving the Problems] The method for manufacturing a molding die of the present invention includes the steps of: (a) producing a mother mold having the same shape and dimensions as the product to be molded by machining using hard plastic; (b) Using this hard plastic matrix as a core, liquid curable synthetic rubber is cast on the outside and cured, and then the hard plastic matrix is removed and the shape is the same as this matrix. , manufacturing a synthetic rubber mold having cavities of the same size, and (c) injecting and filling a curable liquid inorganic composition into the cavity of the synthetic rubber mold and curing it to form a matrix made of the inorganic composition. (d) casting a molten die-casting alloy on the outside of the mother mold made of the inorganic composition as a core, and then removing the mother mold made of the inorganic composition; A method for producing a molding mold, which includes the step of obtaining a molding mold having a cavity having the same shape and dimensions as the mother mold, the method comprising the steps of obtaining a molding mold having a cavity having the same shape and dimensions as the mother mold, the method comprising the steps of: obtaining a molding mold for die casting that has been previously manufactured through the steps (a) to (d) above; It is characterized in that a mold made of the alloy is heated and melted and used as the alloy for die casting in the subsequent step (d).

In the present invention, it is preferable to use plastics made of the same material as the product as the hard plastic for producing a matrix having the same shape and dimensions as the product to be molded. Any plastic material can be used. An example of such a resin is ABS resin (acrylonitrile-butadiene-styrene copolymer), which is known as a relatively inexpensive resin with good mechanical properties and heat resistance, as well as excellent moldability and dimensional stability. There is.

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

Furthermore, injecting and filling into the cavity of this synthetic rubber mold,
As the curable liquid inorganic composition, 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 die-casting alloy that is cast on the outside of the mother mold made of the inorganic hardened material formed in this way is, for example, made of zinc and aluminum, and has a melting point of 380°C and is cast after casting. Mechanical expansion force is 26-34
)cg/- alloys can be used. Commercial products of such alloys include, for example, MAK (trade name) manufactured by Mitsubishi Metal Industries, Ltd.

In the present invention, a mold that is first cast from such a die-casting alloy and is no longer used due to a request for modification of the product shape, etc. is heated and melted, and then used as a subsequent casting material. .

[Operation] In the method of manufacturing a molding die of the present invention, first, a block of hard plastic 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 into the inside of a casting frame, and after casting a liquid curable rubber such as liquid silicone rubber on the outside of the mold, it is divided into two parts to form a core mother mold. By removing the mold, a synthetic rubber mold having a cavity having the same shape and dimensions as the inserted mother mold, that is, the same shape and dimensions 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.
A matrix made of an inorganic composition having the same dimensions, ie, the same shape and dimensions as the product to be molded, is obtained.

After that, this mother mold is used as a core, and a molten die-casting alloy is cast on the outside of the core, and the core is formed into a cavity by splitting it into two parts and removing the core mother mold. , an alloy mold with high strength, good dimensional accuracy, good appearance, etc. can be obtained.

In the present invention, when the mold obtained here is no longer used due to discontinuation of production of the product, or when it is damaged and it becomes necessary to manufacture the same mold again, it is heated and melted. It is used again as an alloy material for die casting in the final step. That is, a new mold is manufactured by casting on the outside of a mother mold made of an inorganic composition produced through the steps described above based on a new product drawing. If the mold is to be remanufactured due to damage, there is no need to create a new mold, and the mold can be manufactured from the original mold.

In the present invention, the molds are melted and reused repeatedly in this way, and new molds with high strength, good dimensional accuracy, good appearance, etc. are manufactured or renewed one after another.

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

FIG. 1 is a flow chart for explaining the steps of an embodiment of the present invention.

In the example, first, based on a drawing of a new product to be molded, machining is performed using an NC machine tool using NC tape, and a resin block such as ABS resin is machined as shown in Figure 2 (a).
As shown in the figure, a mother die 1 having the same shape and dimensions as the product is manufactured.

Next, as shown in FIG. 2(b), this mother mold is inserted as a core into a predetermined position inside the 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 1, and is solidified and then fired. , a plaster mold 4 of the same size is formed. (Second
(C)) After that, as shown in Fig. 2(d), the obtained plaster mold 4 is used as a core, and a zinc alloy for die casting 5 having a melting point of 380° C. is pressure cast (die) on the outside of the core. Cast), but at this time, first, as a zinc alloy for die casting,
In a similar manner, as shown in FIGS. 2(e) to 2(i), a mold 16 having a cavity of a different shape, which has been cast from a zinc alloy and has already been used as a forming mold, is heated and melted for use. .

That is, in FIGS. 2(e) to (i), 11 is a mother mold made from a resin block such as ABS resin based on the product drawing, 12 is a casting frame, and 13 is a mother mold inside. 11 is a silicone rubber mold formed with a cavity of the same shape and size, 14 is a plaster mold with the same shape and size as the mother mold, and mold 16 uses the plaster mold 14 as a core,
Zinc alloy 1 for die casting with a melting point of 380℃ on the outside
5 was pressure cast, and after cooling and hardening, it was divided into two parts and the core was taken out.

The heated molten material of the mold 16 previously manufactured and used is used as a casting material to be pressure cast onto the outside of the plaster mold 4, and after being cooled and hardened, it is split into two to take out the core, and finally Finish the outer surface of the resulting mold.

The mold 6 made of zinc alloy for die casting thus obtained has good dimensional accuracy and appearance, and has sufficient heat resistance and mechanical strength, like the mold 16 made of zinc alloy for die casting manufactured previously. As shown in FIG. 2(j), it can be used as a mold for injection molding in combination with a template 7.

When the mold is used and becomes unnecessary, or when it becomes necessary to renew the mold due to damage etc., the mold 16 described above
Similarly, it can be heated and melted and used again as a molding material for new or updated molds.

In addition, when these molds are used as molds for injection molding, they are used as a pair of a fixed side mold part 8 and a movable side mold part 9, and the mold cavity 10 between them is heated and melted. The resin is injected and filled through the sprue runner and gate.

The mold obtained in this example is mainly used as a mold for injection molding, but the number of man-hours required for manufacturing is small, and the mold is manufactured by reusing a used mold, so it is easy to manufacture. Cost is lower. 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.Furthermore, it is possible to quickly respond to requests for modification or remodeling of the product shape, so it is suitable for high-mix, low-volume production. It is suitable as a mold.

Furthermore, heating and melting a previously used mold and using it as a casting material is advantageous not only in terms of reducing material costs but also in terms of effective use of resources.

In addition, in the manufacturing method of the example, the mother mold 1 of ABS resin
By manufacturing the molded product by considering the draft angle, undercut, resin shrinkage rate, etc., it is possible to omit machining to add draft angle after casting, further reducing the number of man-hours. can.

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

[Effects of the Invention] As explained above, according to the manufacturing method of the present invention, by heating and melting a used or unusable die-casting alloy mold and pressure-casting it again,
A new or renewed mold with good strength, dimensional accuracy, appearance, etc. can be manufactured easily and at low cost.

Furthermore, the method of the present invention is useful as a method for manufacturing molding dies for high-mix, low-volume production because it can quickly respond to requests for modification or remodeling of product shapes.

Furthermore, it has the advantage of being able to effectively utilize resources and reduce usage.

[Brief explanation of the drawing]

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...Resin matrix 3...Silicone rubber mold 4...
Plaster mold 5... Alloy for die casting 6... Alloy mold for die casting. 16...Used alloy mold

Claims (1)

[Claims] (1) (a) A process of machining a matrix of the same shape and dimensions as the product to be molded using hard plastic; A process of casting and curing liquid curable synthetic rubber, and then removing and removing the matrix made of hard plastic to produce a synthetic rubber mold having a cavity of the same shape and size as the matrix; c) injecting and filling a curable liquid inorganic composition into the cavity of the synthetic rubber mold and curing it to produce a matrix made of the inorganic composition; and (d) manufacturing a matrix made of the inorganic composition. After casting a molten die-casting alloy on the outside of the mold using the mold as a core, the mother mold made of the inorganic composition is removed and removed to obtain a molding die having a cavity of the same shape and size as the mother mold. A method for manufacturing a molding die in which the molding die made of the die-casting alloy manufactured through the steps (a) to (d) is heated and melted, and then the molding die made of the die-casting alloy is heated and melted. A method for manufacturing a forming die, characterized in that it is used as an alloy for die casting in the step (d).