JPH03199015A - Manufacture of molding die - Google Patents

Abstract

PURPOSE:To form the part of a core as a cavity and obtain a mold with high strength and an excellent dimensional accuracy and an exterior appearance by employing a matrix comprising heat resisting synthetic rubber as a core, and casting a low melting point alloy around the outside thereof, and further splitting it into two pieces for extracting and removing the matrix of the core therefrom. CONSTITUTION:A matrix 1 being an identical shape and identical configuration with an article is manufactured from resin blocks of ABC resin or the like. Next, the matrix 1 is inserted as a core into a predetermined position within the inner part of a casting mold frame 2 comprising acrylic resin or the like, and liquidus curing silicone rubber is cast-molded into the outside thereof and then hardened, thereafter, a cast-molded body 3 obtained is split into two pieces in order to extract and remove the 1 of the core therefrom. In this fashion, into the cavity of the silicone rubber molding die 3 formed with the cavity in the inner part thereof, liquidus silicone rubber cast-molded, which has a higher heat resistance than that of the low melting point alloy used herein; as a result, a cast-molded body 4 is formed which is an identical shape and identical dimension with the matrix 1. Following this, by employing the cast-molded body 4 as a core, a low melting point alloy 5 being 200 deg.C or below in melting point is cast around the outside thereof, and after pressing and cooling, it is split into two pieces for taking out the core therefrom; finally, the cast die obtained herein is finished in its outer surface.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for manufacturing a simple mold for molding made of a low melting point alloy, and particularly relates to a method for manufacturing a simple mold for forming made of a low melting point alloy. 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.

[Problem to be solved by the invention] However, although such a method can provide a mold with durability superior to that of Machikata Shot, it requires many days to manufacture one mold. , 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, there are an increasing number of requests for modifications to product shapes and changes in product design.

Therefore, if a conventional mass-production mold manufactured by machining is used as a mold for molding such a product, there is a problem that it does not pay off in terms of cost and leads to an increase in the product price. there were.

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 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) casting a heat-resistant curable liquid synthetic rubber into the cavity of the synthetic rubber mold and curing it to make the mold made of the heat-resistant synthetic rubber. A step of manufacturing a mother mold; (d) using this mother mold made of heat-resistant synthetic rubber as a core, and casting a low melting point alloy having a melting point of 200°C or less on the outside thereof, and then forming a mother mold made of said heat-resistant synthetic rubber; A method for manufacturing a molding die, comprising a step of removing and removing the molding die to obtain a molding die having a cavity having the same shape and dimensions as the mother mold,
A mold made of a low melting point alloy produced through the steps (a) to (d) above is heated and melted and used as the low melting point alloy in the subsequent step (d). It is said that

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, the heat-resistant curable liquid synthetic rubber that is cast into the cavity of this synthetic rubber mold to form the cast body that will become the final core of the mold has an extremely high melting point that is higher than the melting point of the low melting point alloy described below. Heat-resistant liquid silicone rubber,
Alternatively, it is desirable to use liquid fluororubber.

Furthermore, a low melting point alloy with a melting point of 200°C or lower, which is cast on the outside of a mother mold made of such heat-resistant synthetic rubber as a core, is usually called wood metal and has a melting point of 120°C. An alloy mainly composed of bismuth and lead at 125°C, or bismuth with a melting point of 138 to 170°C.
A tin-based alloy or the like may be used.

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

[Operation] In the method for 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 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 extracting and removing, the shape is the same as the mother mold that was pushed in,
A synthetic rubber mold having a cavity having the same dimensions, ie, the same shape and dimensions as the product to be molded, is obtained.

Next, by pouring highly heat-resistant synthetic rubber into the cavity of the resulting synthetic rubber bottom mold, the mold is again made into the same shape and dimensions as the mother mold, i.e., the same shape and dimensions as the product to be molded. A matrix made of heat-resistant synthetic rubber is obtained.

After that, this matrix was made into a medium T, and the outside had a melting point of 200.
By casting a low melting point alloy below ℃, dividing it into two parts, and removing the core matrix, the core part is formed as a cavity, which has high strength, J゛ method accuracy, appearance, etc. A good mold can be obtained.

In the present invention, when the mold obtained here is no longer used due to the discontinuation of production of the product, or when it is damaged and it becomes necessary to manufacture the same mold again, - the mold is thermally melted, It is used again as a low melting point alloy material in the final step.

That is, a new mold is manufactured by casting on the outside of a mother mold made of heat-resistant synthetic rubber that has been produced through the steps described above based on a new product drawing. When remanufacturing due to damage to the mold, there is no need to create a new mold.
It 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 FIG. 1, 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 1 is inserted 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, liquid silicone rubber, which has higher heat resistance than the low melting point alloy used, is poured into the cavity of the silicone rubber mold 3, which has a cavity with the same shape as the mother mold 1. A cast body 4 having the same shape and dimensions as the mold 1 is formed.

(Fig. 2 (C)) After this, as shown in Fig. 2 (d), the obtained cast body 4
is used as a core, and a low melting point alloy 5 having a melting point of 200° C. or lower, for example, a bismuth-lead alloy, is cast on the outside of the core.
As shown in ~(i), a mold 16 having a cavity of a different shape, which has been cast from a low melting point alloy and has already been used as a forming mold, is heated and melted for use. That is, the second
In Figures (e) to (i), 11 is a mother mold made from a resin block such as ABS resin based on the product drawing;
13 is a casting frame; 13 is a silicone rubber mold having a cavity of the same shape and size as the mother mold 11;
Reference numeral 14 denotes a cast body made of heat-resistant silicone rubber having the same shape and dimensions as the mother mold 11, and the mold 16 uses the cast body 14 as a core and has a low melting point material having a melting point of 200° C. or less on the outside thereof. It was obtained by casting Alloy 15, pressurizing it, cooling it, then splitting it into two pieces and taking out the core.

The heated melt of the mold 16 previously manufactured and used in this way is cast as a casting material on the outside of the cast body 4, and then pressurized and
After cooling, it is divided into two parts, the core is removed, and the outer surface of the resulting mold is finished.

The mold 6 made of the low melting point alloy thus obtained has the same dimensional accuracy as the mold 16 made of the low melting point alloy manufactured previously.
It has a good appearance and sufficient heat resistance and mechanical strength.
In addition to being used as a mold for casting synthetic resins, it can also be used as a mold for injection molding thermoplastic resins such as polyethylene and polypropylene.

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

Note that when these molds are used as molds for injection molding, they are usually used in combination with a metal mold plate 7, as shown in FIG. 2(j), and the fixed side mold part 8 and A mold cavity 10 between the pair of movable side mold parts 9 is filled with heated and melted resin 1.1 times through a sprue runner and a gate.

As described above, the molds obtained in the examples require fewer man-hours to manufacture, and the manufacturing cost is reduced because the molds are manufactured by reusing used molds. 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, and it is also possible to quickly respond to requests for modification or modification of the product shape, making it ideal for high-mix, low-volume production. Suitable as a mold.

Moreover, heating and melting a previously manufactured 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 made of ABS resin etc. is
By manufacturing in consideration of the Ii rate, etc., machining for adding a draft angle etc. after casting can be omitted, and the number of man-hours can be further reduced.

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 low melting point alloy mold and pressurizing it again, strength, A new or updated mold with good 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 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... Resin mother mold 3... Silicone rubber mold 4...
...Heat-resistant silicone rubber cast body 5...
...Low melting point alloy 6...Low melting point 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 liquid curable synthetic rubber and curing it, 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 dimensions as the matrix; c) casting heat-resistant curable liquid synthetic rubber into the cavity of the synthetic rubber mold and curing it to produce a matrix made of the heat-resistant synthetic rubber; After casting a low melting point alloy having a melting point of 200° C. or less on the outside of the core, the mother mold made of heat-resistant synthetic rubber is removed and a cavity having the same shape and dimensions as the mother mold is formed. A method for manufacturing a molding die, which comprises the step of obtaining a molding die having the following properties, in which a molding die made of a low melting point alloy produced through the steps (a) to (d) above is heated and melted. , a method for manufacturing a forming die, characterized in that it is used as a low melting point alloy in the subsequent step (d).