Features of the “orbital” technique
The “orbital” technique is applied to the EDM process for the forging of some component parts, dies, etc. tooling. This reduces the stress between the tool (the die) and the component part in the contact area thus increasing tool life. Moreover, smaller size (diameter) tools could be used to machine larger cavities or holes of a shape which is completely different from the shape of the die. Moreover, the tool moves in an “orbital” manner, rotating around a certain axis with its operational end or at the beginning of its length, performing a movement similar to the orbital path of planets.
The figure shows the principal drawing of the die, which “swings” similar to a flywheel around the axis O, such that O1 in its upper end moves along a circumference (ellipse, etc.), i.e. performs an “orbital” movement. Moreover, the flat radius R forms the recess of an OD = D, the forces required to press the material of the workpiece in the area around points M being smaller that what would be required if the entire area S = .D2 /4 was to be pressed by a single stroke of the die without the “orbital” movement. The “orbital” technique is applied not only to the EDM process, but also to the ECM process, etc.
Applying the “orbital” technique to the EDM process
The “orbital” technique is applied to the EDM manufacturing process with the tool, the electrode (-), performing a similar movement to the described in above figure. An example of one such application.
1. Tool holder
1.1 Tool (electrode)
2. Workpiece (round grinding machine)
3. Machine chuck
Let us consider an application of the EDM process for a machine featuring horizontal spindle and chuck 3 used to support the workpiece to be machined, with the holder 1 feeding the tool 1.1 along the X direction, the feeding of the tool resulting in gradual change of the angle from 0to . The workpiece 2 rotates around X – X with the chuck 3. This results in shaping (cutting) the cavity of an OD = D, having the shape of a pear. Different cutting shapes can be achieved through synchronizing the movement of the workpiece, tool and tool feed.
The “orbital” movement of the electrode can also be applied to conventional machines of vertical tool axis and die-sinking. This will require the rotational movement of the spindle of the machine to provide for the “orbital” movement in point O1 (operational end) of the electrode. The workpiece can alternatively be fixed to the machine worktable. Thus, smaller size (diameter) electrode could be used to cut or grind larger-size cavities or holes of shapes which are completely different from the cylindrical shape, as well as toroid-shaped, etc. cavities.