JPH0565293B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing a mold by electrical discharge machining.

[Prior art]

Conventionally, electric discharge machining is often used to manufacture molds, and in this case, tool steel, stainless steel, tungsten carbide, or the like is generally used as the mold material constituting the mold. When performing electric discharge machining on the mold material, it is common to perform rough machining from the viewpoint of machining speed before reaching the desired shape, and the electrode wear during rough machining is different from that of steel versus copper. Even if low-consumption machining is possible, such as in the case of steel vs. graphite, electrode consumption of about 1 to 0.5% cannot be avoided, and deformation of the electrode shape cannot be avoided. For this reason, finishing electrodes were also required to process the material into the desired shape, and several electrodes had to be prepared.

In addition, when mold materials are combined and used as a mold, a first mold material and a second mold material that forms a required mold between the first mold material and the first mold material are provided. In many cases, the mold material is made of steel, so if electrical discharge machining can be performed by combining steel with steel, the machining accuracy will be higher than if the first mold material and the second mold material are processed separately and then combined. , it is natural that the time to completion will be shorter. However, in steel-to-steel machining, it is not possible to achieve low consumption processing as when using copper electrodes or graphite electrodes, and it is usually impossible to avoid consumption of about 10 to 20%.

[Summary of the invention]

This invention has been made in view of the above-mentioned problems, and has the following objectives.

(1) Even in electrical discharge machining of steel-to-steel combinations,
1, such as when using copper or graphite electrodes.
It is possible to perform machining with low consumption of about %.

(2) The desired shape can be quickly processed with a single electrode, and the material processed into the desired shape can be used as a mold material.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a first mold material whose perspective view is shown in FIG. 2, 2 is a box for storing the first mold material 1, and 3 is a wire-shaped or Rod-shaped thermal spraying material, 4 is thermal spraying material 3
5 is a drive device that drives the delivery roller 4; 6 is a melting gas supply device such as oxygen amoethylene gas that melts the thermal spraying material 3; 7
is an inert gas compressed into carbon dioxide gas, nitrogen gas, argon gas, etc. for turning the thermal spray material 3 melted by the gas 8 from the melting gas supply device 6 into spray-like particles 9.

Further, 10 is an ejection nozzle, 11 is an inert gas supply device, and 20 is a thermal spray layer formed on the first mold material 1, which forms a required mold with the first mold material 1 by the method described below. This material becomes the second mold material.

Next, a method of manufacturing the sprayed layer 12 having the above structure will be explained.

First, the first mold material 1 is fixed inside the box body 2,
Spray-like particles 9 of the thermal spray material 3 are injected onto the surface of the first mold material 1. The spray-like particles 9 are produced by feeding the thermal spraying material 3 through the jet nozzle 10 by the driving device 5 and the roller 4, melting it with the thermal spraying gas 8, and melting it with the compressed inert gas 7. is injected toward the mold material 1. Although the inert gas 7 is used to prevent oxidation of the particles 9, compressed air may be used instead of the inert gas 7. If this compressed air is used, oxides will be mixed in, so it is necessary to perform ring annealing in an atmosphere of hydrogen gas, carbon monoxide, etc. after thermal spraying to remove the oxides.

By the above method, spray particles 9 of the thermal spray material 3 are sprayed onto the first mold material 1 until a thermal spray layer 12 with a thickness of about 3 to 5 mm is formed. When this sprayed layer 12 is separated from the first mold material 1, it will have a shape transferred to the first mold material 1. At this time, by applying a mold release agent to the first mold material 1, the thermal spray layer 1
2 will be easier to leave. After the sprayed layer 12 is removed, it is turned upside down and a zinc alloy or superplastic alloy ( Molten metal (such as lead-tin alloy) is poured in, and pressure is applied as necessary.

Next, a method of finishing the sprayed layer 12 produced as described above as a second mold material will be described. The thermal sprayed layer 12 removed from the first mold material 1 cannot be used as the second mold material as it is because it is unavoidable to be slightly deformed when it is removed, and if it remains deformed it will become expensive. This is because it is unsuitable for molds that require high precision.

FIG. 3 is a diagram for explaining the manufacturing method of a mold by electrical discharge machining. In this diagram, the same reference numerals as in FIGS. The machining fluid 32 stored in the machining tank 30 is an electrode feeding device which gives the first mold material 1 an oscillating motion in addition to main shaft feeding. 33 is a processing power supply device, in which the first mold material 1 is connected to a positive electrode and the sprayed layer 12 is connected to a negative electrode.

With the above configuration, the first mold material 1 and the sprayed layer 1
2 facing each other with a slight gap in the machining fluid 31,
By performing well-known electrical discharge machining, the sprayed layer 12
is finished into a second mold material that constitutes a mold together with the first mold material 1. In addition, since the thermal spray layer 12 is a transfer of the first mold material 1, it roughly matches the first mold material 1, and the amount of machining required by electrical discharge machining is small. Processing time is extremely short.

The mold is manufactured as described above, but next, we will discuss the fact discovered in the experiments that led to the completion of this invention. The logic behind low consumption machining is explained below. That is, thermal spray metal is porous because it is made by spraying molten metal onto the metal. As a result, heat conduction decreases significantly, possibly by as much as 1/3. In that case,
It was discovered that the amount of wear caused by electrical discharge machining increases.

In fact, even with copper electrodes that can easily achieve low consumption, those manufactured by thermal spraying show a consumption ratio of 20 to 30% when processing steel.

The reason for this is that it is porous and has poor heat conduction.

The principle of low electrode wear of electrical discharge machining electrodes can be explained as follows.

When looking at the consumption ratio from the property of the material, it is best to think of it in terms of the product θm・λ of the material's melting point (θm) and thermal conductivity (λ). Materials with small θm・λ (such as porous materials) Even if the material has a large value of θm・λ, there is a region where the material simply experiences a temperature rise and is not processed. In other words, each material has a minimum energy density required for machining, and materials with large θm and λ have a high minimum energy density, and materials with small θm and λ have a low minimum energy density, so low electrode consumption machining requires a minimum energy density between these If you choose between them, one will be processed and the other will only be heated and not processed.

The same is true for thermal sprayed electrodes; if they are made of the same material, the thermally sprayed one will have smaller θm and λ, which means that even the same material can be processed with low consumption.

The embodiments of this invention have been described in detail above, but
When making the second mold material, a similar porous metal is obtained when powdered metal is sintered, so a box containing powdered iron powder (or powdered iron alloy iron powder) etc. is used instead of sprayed metal. It can be used as it is, pressed and fired, and after firing it can be finished by electric discharge machining in the same way.

Note that when a gap is required between the first mold material and the second mold material that make up the mold, the desired distance can be achieved by performing swing machining using numerically controlled electrical discharge machining. Obtainable.

〔Effect of the invention〕

As described above, the present invention includes a first mold material,
When manufacturing a mold consisting of the first mold material and a second mold material constituting a required mold by electric discharge, the second mold material is made of a porous metal body. At the same time, the second mold material is used as the consumable polar side electrode, and the first mold material is used as the other polar side electrode, and a discharge is formed between the two to produce the mold. Therefore, molds can be manufactured quickly with high precision at low cost, and are extremely effective industrially.

Further, the surface of the sprayed layer machined by electric discharge machining in the machining fluid becomes a surface layer that is once melted and re-solidified, and the machined surface itself becomes carburized and hardened.

[Brief explanation of the drawing]

The figures are for explaining a method of manufacturing a mold by electric discharge machining according to an embodiment of the present invention. FIG. 2 is a perspective view of the first mold material, and FIG. 3 is a diagram showing a state in which the mold is manufactured by electrical discharge machining. In the figure, 1 is the first mold material, 12 is the thermal spray layer, 31 is the electrical discharge machining fluid, 32 is the electrode feeding device, 3
3 is a processing power supply device. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. A method of manufacturing a mold by electric discharge, which consists of a first mold material and a second mold material that constitutes a required mold between the first mold material and the above-mentioned first mold material. The second mold material is made of a porous metal body, the second mold material is used as a consumable polar electrode, and the first mold material is used as another polar electrode. A mold manufacturing method using electric discharge, in which a mold is manufactured by forming electric discharge between the two. 2. The second mold material is formed by forming a sprayed metal layer of a required thickness on the first mold material and then peeling off the sprayed metal layer. A method for manufacturing a mold by electric discharge according to scope 1. 3. Claim 1, characterized in that the second mold material is formed by molding metal powder using the first mold material as a model and then sintering it. The method of manufacturing a mold using electrical discharge as described. 4. The method of manufacturing a mold by electric discharge according to claim 1, characterized in that electric discharge machining is performed by applying a rocking motion between the first mold material and the second mold material.