Received this question over the weekend. Here's a quick answer:
A machining condition that has a work piece that is completely flat on both sides (top & bottom) so that the machining nozzles can both be set to within under 0.008” (set to 0.020” on Makino). This close setting of the machine nozzles, which is very sensitive and critical, is done with the aid of a metal shim or gage. In addition to the work piece being completely flat, their must also exist a 0.200” wide zone of material all the way around the working geometry/shape to maintain seal-off and maintain flushing pressure, and their can be no thru or cross hole interruptions during the machining process (work piece and cut are thru completely solid materials). Any changes in any of these conditions will contribute to part inaccuracies, wire breaks, and greatly reduced machining speeds.
That really begs the question - what is a poor flushing conditon?
A poor flushing condition is any cut or process that does not allow one or both of the machining nozzles to be set to within the “optimum” nozzle setting of under 0.008” to the work piece. Poor flush typically involves non-flat work pieces that may include changes in part thickness, machined steps, thru holes, cross holes, counter-bores, etc. Poor flush can also occur in a completely flat work piece as a result of the work holding setup. It is quite common to see a completely flat work piece not allow one or both of the machining nozzles to be set to within the “optimum” flush condition height as a result of the nozzles needing to be raised away from the work piece to provide clearance for work holding and clamping.
