Wire EDM (Electrical Discharge Machining) and Cutting with Ram E
Designers are rediscovering the use of surface decoration as a valid form of design expression. Industrial techniques have been borrowed from engineering applications and are used to create highly intricate patterns, as decorative as if they have been abstracted from nature or fairy-tale narratives.
Many unusual methods have been invented for cutting complex patterns into difficult materials. Dating back to when the phenomenon was first observed in the 1770s, electricity has been harnessed by scientists for use in cutting and machining materials. EDM (electrical discharge machining) is one of the latest processes to exploit electricity for cutting intricate patterns.
Since its commercial development in the 1970s, wire EDM has become an increasingly popular method of machining metals. Together with processes such as water-jet cutting
(see p.42) and laser cutting (see p.46), Wire EDM is a non-contact method of cutting materials. Less commonly used than the other two and more suited to extremely hard steels and other hard-to-cut metals such as high-performance
alloys, carbides and titanium,it is, nevertheless, able to achieve the same level of intricacy.
Based on a type of spark-erosion (it is sometimes also referred to as spar machining or spark eroding), wire EDM is used to cut very hard, conductive metals by using sparks to melt away
the material. The spark is generated by a thin wire - the electrode - which follows a programmed cutting path (determined by a CAD file). There is no contact between gap and melts the material. De-ionised water is simultaneously jetted towards the melting point, cooling the material and washing the waste away.
There is another sort of EDM machine, the 'ram'. As the name suggests, the ram method involves a machined graphite electrode mounted on the end of an arm (the ram) being pushed onto the surface of the material to be cut.
Volumes of production
The process and shape can be controlled manually by an operator or from a CAD file. so it is equally suited to one -off pieces and automated mass production.
Unit price vs capital investment
Requires no tooling.
Speed
The latest generation of EDM machines can cut up to 400 square millimeters per minute, depending other electrical resistance of the material and, of course, its thickness A50 millimeters piece of steel can be cut at a rate of approximately
4 millimeters per minute.
Surface
Wire EDM is well known for its ability to achieve an excellent finish.
Types/complexity of shape
The delicate wire can cut very intricate shapes from the toughest materials.
Scale
Depending on the material,the generator size and the power, the process can cut through massive hunks of metal up to an astonishing 500 millimeters thick,although this well be very time consuming, with cutting occurring at a rate of less than 1 millimeter per minute.
Tolerances
Wire EDM is extremely accurate and can achieve sub micron tolerances.
Relevant materials
Restricted to conductive metals The process is ideally suited to hard metals, the hardness of which does no affect the cutting speed.
Typical products
One of the big markets for this process is for the super hardened dies and cutters that are used in industrial production. Other applications include super tough components for the aerospace industry.
Similar methods
Laser cutting and electron-beam machining(EBM).
Sustainability issues
Power consumption is very high, especially as the cutting rate is slow, which results in long cycle times. The offcut materials need to be melted down and recycled back into the process to reduce material consumption and waste.
