Reason to use the electric discharge method for processing of WC-Co (Carbide)
Since the WC-Co (Carbide) is superior in abrasion and impact resistance, it would be widely used for a die and a cutting tool.
How can we process such a quite hard WC-Co (carbide)? Our company is working out the cutting and forming the WC-Co (carbide), while the cutting and/or the direc curving are not common in the real world. Yet there is some limitation for the processing shape. Even though the punch and the pin could be processed by the direc curving, not yet for the deep hole shape.
Therefore, the electric discharge machining that is conductive, such as the wire cut and/or the sinker electric discharge machining, would be coming into the appropreate method regardless of the hardness of material.
Difficult point of the sinker electric discharge machining to We-Co (Carbide)
Because the melting point of main ingredient of WC-Co (carbide), tungsten carbide (WC), is high as 2,900 ℃, it is required more energy for processing. Therefore we need the high energy density, in other words, a high peak electric current and the short pulse width.
Unlike the sinker electric discharge machining that can processi the steel material with almost non consuming electrode, under the processing condition of the WC-Co (Carbide), the consumption of electrode is relatively high and delivering deterioration of the processing accuracy.
Therefore, we would reduce the consumption level of the electrode by using the high melting point and the thermal conductivities electrode such as copper tungsten or silver tungsten, At the same time through considering the consumption amount of the elecrode, we would design the electrode and develop the NC program.
The deep Hole Processing to WC-Co (Carbide)
The sinker electric discharge machining is one of the non-contact processing method by hitting the spark intermittently and processing repeatedly for melting, cooling and scattering of metal.
Therefore unlike the contact processing such as the cutting that uses the drill and/or the end mill, for the sinker electric discharge machining, it is not so necessary the strength on the electrode itself.
In order to do the deep hole processing where we need the greater pushing power to the hard material such as the WC-Co (Carbide), we can process it by the sinker electric discharge machining or the small hole drilling EDM. The former machining can process regardless of the hardness of materials and not so required strength of the electrode itself. The latter machining can process by using the pipe-shaped electrode with starting processing liquid from the electrode tip to exhaust the processing waste easily.
There is a guidepost called the aspect ratio to evaluate the deep hole machining for small diameter of the hole. Thus ratio is culuculated for dividing the depth of processing hole by the diameter of the hole, For instance in the case of 0.1mm in hole diameter around, the aspect ratio comes to 10 times (1.0mm in depth) and in the case of more than 0.2mm in hole, it comes 50 times (10mm in depth).
Incidentally, the electric dischage machining such as the wire cut, the sinker machining are used for the producing the electrode for the processing of the high aspec ratio as above. Because those machining methods are not giving much load and/or stress to the workpieces.
irregular shape Hole Processing to WC-Co (Carbide)
As a characteristic of the sinker electric discharge machining, the electric discharge would occur in a corner and an edge. And the irregular shape hole processing which have above character present the decline of the precision accuracy by the elecrode consumption and as a result, its designingand production of the electrode and processing itself become severer.
In our company, we have been good at the production of the electrode by using long years devoted know-how and using the presision micromachining center IQ300, and as well as the processing of a complex shape by the skill of the expert craftsman.