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Galil / Re: galil thc
« on: January 06, 2010, 06:46:14 AM »http://www.candcnc.com/
see dthc section
basically it requires an analogue input to read from a voltage divider circuit ( 0-400v dc at torch cathode output divided down to give 0-10 v at galil input)
the operator sets initial pierce height (variable for different material/thickness etc) above the metal which is higher than the cut height, also a variable parameter set by the operator for material to be cut.
the plasma should have a floating head with height rference switch touch off on it. ( z reference lowers the torch, in switched off condition to metal . the torch continues down until it activates the the z reference switch fitted to the floating head. at this point the z is raised by the travel of floating head to z ref switch plus pierce height to give correct pierce height above the metal
an output is then given to the torch on relay. starts plasma arc and pierces metal
the plasma outputs an arc ok signal back to control to tell control it is on once arc is established
the control dwells for a parameter set time (to allow full pierce of the material)
the z is now lowered to the parameter set cutting height
motion commands given to start cutting movement
during movement the voltage divided signal is referenced continually and any change moves the torch up or down to keep the arc at the precise voltage.
the voltage / current loop is what makes for a perfect cut.
this movement must be virtually instantaneous to keep the arc set as required.
also this needs to be able to be disabled or reduced at very slow feed rates ie tight corners to stop the torch diving down into the metal in corners where it is cutting faster than its moving