放電加工

Electrical Discharge Machining

The latest electrical discharge machines are capable of processing difficult-to- mill
materials for which high-speed machining centers optimized for high- precision milling are
not suitable. Work that cannot be milled using a machining center includes materials that are even harder than the cutting tool, difficult-to- mill materials, and narrow or deep cavities. For
these, electrical discharge machining is the solution. First, a high-speed graphite electrode
machine is used to fabricate the male electrodes from graphite, which is easy to mill. These
are then used in an electrical discharge machine to make the molds and female dies.
For example, it is not possible to mill an object with deep, narrow grooves using a machining
center, but it is possible to mill a male die that is the inverted configuration of the object.
Once one has a male electrode, an electrical discharge machine can be used to mill the desired
mold. In this way, a high- speed graphite electrode machine and an electrical discharge
machine can be used in tandem to fabricate molds with difficult-to-mill configurations. In
addition, the use of high-precision automated machine tools makes continuous unattended
operation possible. This contributes to shorter delivery times and reduced cost.
For products where the cosmetic design is an important consideration, and where there is a
need to check the final form against a design model, a prototype can be fabricated in graphite.
This makes it possible to confirm the final form of the product and to produce a mold that
matches the design model precisely. Once the final confirmation is complete, an electrical
discharge machine is employed to fabricate the mold, using an electrode made of graphite.

Electrical discharge machine combining excellent precision and
automated operation
Makino EDNC series machine tools provide state-of-the-art performance in terms of both ease of operation and automation, making
them indispensable for mold production. Their biggest features are an automation system combining an Auto Work Changer* (AWC),
an Auto Tool Changer* (ATC), and the New Expert System*. The latter’s P Pulse milling status optimization function uses
numerical control to precisely monitor spark discharge, a job that was previously performed by a skilled human operator. Stable and
optimal machining is made possible by the A Jump function, which controls jump operation, and S Control, which eliminates instability
immediately after milling starts. The Smokeless* (SL) system, which uses suction to remove smoke and chips, is particularly
effective when milling large work pieces. Additional features include the Multi Application* (MA) head, which rotates to introduce a
series of electrodes, and Mini CIM*, which supports the operation of multiple machine tools from a single personal computer. These
features combine to provide superior functionality, reliability, and ease of operation, making Makino’s electrical discharge machines the best currently available. Such top-class machine tools make it possible for us to manufacture a wide variety of molds
reliably and to provide service our clients can depend on.

* Product data provided by Makino Milling Machine Co., Ltd.

■Machine Tool Processes
	●Electrode Fabrication Program data designed using CAD/CAM is input to a high-speed graphite electrode machine, which mills the electrodes. Electrical discharge machining is then employed to make the molds, using the graphite electrodes as the basis. Graphite is used because it is easy to mill, requiring approximately one-fourth the time needed to mill copper, for example. Using this ideal electrode material reduces the overall machining time and increases milling precision.

	●Mold Rough Milling Before the electrical discharge machining stage, a high-speed machining center is used to perform rough milling of the work piece. In the past we used to employ electrical discharge machining for the entire milling process, but adding this extra stage actually ends up shortening the total amount of time required. In addition, it can be performed simultaneously with electrode fabrication, so the work can be mounted in the electrical discharge machine immediately after rough milling is finished. This eliminates machine idle time and helps ensure that machining proceeds efficiently and according to schedule. At Morikawa Kanagata we take great care when acquiring new equipment to ensure a well- balanced lineup of machine tools so that the work process can progress smoothly.

	●Electrical Discharge Machining The electrode fabricated using a high-speed graphite electrode machine and the rough milled work piece are mounted in an electrical discharge machine. Electrical discharge machining then takes place, guided by program data input to the electrical discharge machine. This process produces results that are highly precise and accurate. Since it is automated, it can proceed day and night, 24 hours a day.

	●Mold Completion The completed mold next undergoes quality checking, finishing, dimensional inspection, and assembly, before being shipped to the manufacturer who ordered it. All stages of the process take place on a production line where the machines are kept in full operation at all times to eliminate waste. This is accomplished through the generation of program data based on a detailed work schedule. At Morikawa Kanagata we bring our machining expertise and creativity to bear on the tasks of boosting speed and improving performance. We are always looking ahead in search of new advances.

■Process from Design Program Onward