Good morning Hello:
You've almost got it right.
The table moves in X and Y just like a milling machine.
The lower head never moves relative to the machine frame...the table moves around it.
By contrast, the upper head moves relative to the machine frame; the U and V axis slides are stacked just like the table slides are, and the UV assembly is bolted to the machine column.
The Z axis hangs from the front of the UV slide assembly and moves up and down.
The upper head is bolted to the Z axis slide.
The two table motors each control an axis X or Y.
The two head motors each control an axis U or V
The Z axis motor obviously controls Z (for those machines that actually have a Z axis motor...my old Sodick A320 did not...the head had to be hand cranked up or down)
So there are a minimum of four motors and each is mechanically independent of the others.
Each motor receives the proper inputs from the controller to move independently...the controller tells them how to co-ordinate to describe any non-orthogonal move, linear or circular.
When a taper command is executed, the machine calculates two paths; an X Y path and a U V path and executes them simultaneously, coordinating the motion of all four motors.
The calculation the control makes is obviously a translation of the G code to currents into the motors to make them move.
The details of the motion control are way beyond my pay grade.
The other big factor that separates EDM motion control from any other, is that the signals to move or not to move are responsive to a voltage sensing circuit that measures the voltage required to cross the gap between the wire and the workpiece and triggers a new kind of motion event when the voltage needed to jump the gap drops to a threshold value.
It will slow down or stop the motion or even reverse the axes (maintaining co-ordination between them) if the voltage drops below a second threshold.
So it moves just like a milling machine moves until sensing the conditions it requires both to trigger erosion pulses AND to signal the wire to proceed forward along the motion path in this new way or to stop or to back up, trying to always maintain the proper gap that is required to efficiently erode the workpiece.
That bit of electronic magic is at the heart of wire EDM motion control.
Hopefully this gives you a good framework to design your project.
Cheers
Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
