JPH07241730A - Manufacture of metallic mold - Google Patents

Abstract

PURPOSE:To improve accuracy of a metallic mold and shorten the delivery term by using an electrode for electric discharge machining as a casting mold for casting a metallic mold, and executing casting and electric discharge machining so as to manufacture a metallic mold. CONSTITUTION:A block made of isotropic graphite (block) 31 is fixed to a metallic holder 30. Next the block 31 is fixed to a vertical type machining center, and Nc cutting is performed so as to manufacture an electrode 32 serving both in a casting and in electric discharge machining. Next, the electrode 32 is fixed to a casting, formwork 33 molten zinc alloy 35 is pored through the pouring port of the metallic holder 30 and cooled down to the prescribed temperature, and hence a zinc alloy casting 36 is formed. The graphite casting mold 32 together with the holder 30 are separated from the zinc alloy casting 36. The bottom face 37 of the zinc alloy casting 36 cooled at ordinary temperature in the formwork 33 is machined so as to form a reference face, and it is fixed on the table 40 of the working tank 39 of an electric discharge machine. Working liquid 41 is filled in the tank, and electric discharge machining is executed by the use of the electrode 32. Serving both in a casting and in discharge machining.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a mold for molding resin or light metal, for example.

[0002]

2. Description of the Related Art A conventional mold product manufacturing method is, as shown in the schematic process diagram of FIG. 2, (1) a mold design 11 is performed based on a product design drawing 10, According to 11, a casting model 13 (usually a wooden mold is used) and an electrode 12 for electric discharge machining are manufactured. The casting model 13 has a rough shape with respect to the product shape, while the electric discharge machining electrode 12 is precisely machined into the product shape. (3) Next, the casting model 13 contains silica sand as a main component. Mold 14
(Hereinafter referred to as "sand mold") and cast molten metal 15
(4) The cast metal (hereinafter referred to as "casting") is cooled, the mold 14 is crushed, and the casting 16 is taken out.
(5) Then, the casting 16 is machined 17 such as cutting or grinding as necessary. (6) Next, the casting 16 is formed into a product shape using the electric discharge machining electrode 12.
(7) A casting that has been precision machined by the electric discharge machining 18 is subjected to finishing machining 19 such as polishing and used as a mold 20. Generally, both a casting model and an electric discharge machining electrode are required.

[Problems to be Solved by the Invention]

However, in the above conventional mold manufacturing method, a sand mold containing silica sand or carbon as a main component is used for casting the mold. The strength of the sand mold is generally low, and it is difficult to cast a desired detailed shape of the mold. Therefore, in order to manufacture the sand mold, a casting model designed and manufactured to have a rough shape with respect to the product shape is required, and since the casting by the casting model also has a rough shape, machining and electric discharge machining after casting are required. There are many parts and processing costs. Therefore, in order to obtain the processing accuracy of the mold,
It is necessary to carry out multi-step machining, or to manufacture a plurality of electrodes for electric discharge machining and perform electric discharge machining. There was a problem. The present invention has been made to address the above problems, and its object is to reduce the mold by casting and processing the mold with high accuracy using the mold for the electric discharge machining electrode. It is to provide a manufacturing method that can improve cost, short delivery time, and high accuracy.

[0004]

In order to achieve the above-mentioned object, the structural feature of the present invention is to provide an electric discharge machining electrode used for the electric discharge machining in at least a method of manufacturing a die using casting and electric discharge machining. Used as a mold for casting the mold,
Also, separating the cast product from the cast product while the mold cast by the mold is being cooled. Further, the electric discharge machining electrode is made of a graphite material.

[Operation and effect of the invention]

In the present invention constructed as described above,
As shown in the schematic process diagram of FIG. 1, an electric discharge machining electrode 23 is manufactured according to a mold design 22 from the product design drawing 21. Since the metal mold is cast 24 using the electric discharge machining electrode 23 as a mold, a sand mold according to a conventional casting model is not required, and at the same time, a highly accurate casting can be manufactured by the mold. Further, the sand mold according to the conventional technique is partially stressed by the cooling after the molten metal is cast, and cracks occur. In the present invention, since the mold is released from the mold 25 in the process of cooling and shrinking the casting, cracks generated in the mold can be prevented. As a result, it is possible to manufacture a cast product with a small machining allowance for the product shape, and it is possible to easily perform machining 26 and electric discharge machining 27 after casting, and it is possible to meet the demands for high accuracy, short delivery time, and low cost.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 3 schematically shows a method for manufacturing a metal mold for injection molding a resin bumper for an automobile according to the embodiment. There is. In this mold manufacturing method, an isotropic graphite material is processed into a product shape, and after the shape is approved by a designer, it is used as both a casting mold and an electric discharge machining electrode.

First, an isotropic graphite block 31 was fixed to a metal holder 30. An isotropic graphite block 31 fixed to the holder 30 is fixed to a machining table of a vertical machining center, and an electrode 32 for both mold and electric discharge machining by NC cutting based on the product design drawing of the resin bumper.
Was produced. The cutting process at this time was performed dry using a cemented carbide tool, and the cutting powder was collected by a high pressure dust collector.

Next, the mold / electric discharge machining electrode 32 was fixed to a casting mold 33 prepared in advance. Then, a zinc alloy melted to about 430 ° C. is poured from a pouring port provided in the metal holder 30 to cast the zinc alloy 35.
Was gradually cooled by a cooling mechanism in the mold 33 (not shown). When the zinc alloy 35 is cooled to about 300 ° C.,
A graphite mold (also an electric discharge machining electrode) 32 fixed to the holder 30 was vertically separated from the zinc alloy casting 35 together with the holder. Then, the zinc alloy casting 36 in the mold 33 is cooled to room temperature, and the mold 33 is cooled.
Removed.

The lower surface 37 of the zinc alloy casting 36 was machined at a machining center to form a reference surface. Also, the lower surface 3
On the basis of 7, the upper surface 38 of the zinc alloy casting 36 was cut.

Next, the zinc alloy casting 36 was fixed on a table 40 provided in a machining tank 39 of an electric discharge machine and filled with a machining liquid 41. Further, the holder 30 to which the template / electric discharge machining graphite electrode 32 was fixed was fixed to the head of the electric discharge machine (not shown) at a position facing the table 40, and electric discharge machining was carried out according to a conventional method. After that, the electrical discharge machining of the zinc alloy casting was performed by polishing and graining to obtain a mold.

In the above manufacturing method, the casting model required in the prior art is not necessary, and since the cast zinc alloy casting has a high casting accuracy and a small electric discharge machining allowance, the electric discharge machining required about 40 hours in the past is required. Was reduced to about 8 hours. As a result, it is possible to manufacture molds with the same or higher precision as before with a short delivery time, and it has become possible to reduce costs by 30%.

[Brief description of drawings]

FIG. 1 is a schematic process diagram for explaining a method of manufacturing a mold according to the present invention.

FIG. 2 is a schematic process diagram for explaining a method of manufacturing a mold according to a conventional technique.

FIG. 3 is a schematic diagram for explaining a manufacturing process when the mold manufacturing method according to the present invention is used for an injection molding mold of a resin bumper of an automobile.

[Explanation of sign]

 30 ... Metal holder 31 ... Isotropic graphite block 32 ... Graphite mold / electric discharge machining electrode 33 ... Form 34 ... Casting port, 35 ... Zinc alloy 36・ ・ ・ Zinc alloy casting 37 ・ ・ ・ Reference surface 39 ・ ・ ・ Processing tank 41 ・ ・ ・ Processing liquid

Claims (3)

[Claims] 1. A method of manufacturing a mold using at least casting and electric discharge machining, wherein an electric discharge machining electrode used for the electric discharge machining is used as a mold for casting the mold. 2. The method for producing a mold according to claim 1, wherein the mold is separated from the mold in the process of cooling the mold cast by the mold. 3. The method of manufacturing a mold according to claim 1, wherein the electric discharge machining electrode is made of a graphite material.