Hi All:
First of all the OP states the error is 2.5 micron and then goobers the conversion to inches.
2.5 microns as some have pointed out correctly is about a tenth, or 0.0001"
That's not bad for a wire but not great either.
How it got that way is a subject of some conjecture but here is my own experience trying to make things accurately on such a machine.
Fundamentally, all high end wire EDM machines have exquisitely good motion control and can follow a path very accurately, but the outcome of that exquisite precision is not always translated to the same precision in the workpiece.
The most common culprit is material movement from stress release, and this occurs even during skim cuts and after unclamping the workpiece from the machine.
The next most common is the wire not going where it was expected or told to go and there are two principal reasons why.
First is the influence of flushing pressure on the sideways deflection of the wire.
The second is the clearance required between the wire guides and the wire so it's never EXACTLY where you think it is, it's only APPROXIMATELY where you think it is.
Next in importance is the machine's condition and the environmental stability.
If you imagine the motion task and appreciate the forces and cantilevers involved in driving a machine table with a workpiece around, you can begin to understand the magnitude of the problem; the corollary is that disrupting the system even a bit has magnified consequences so something as simple as a dragging tank seal can throw the whole motion control system out of specification enough to produce the error the OP is complaining of.
Certain machine designs are better for some tasks than others, so the Agie Vee giude system has advantages over the doughnut guides used by most others, and linear motors have advantages over ballscrews and etc etc, but pretty much every machine that states a given positioning precision and repeatability can hit that stated precision but ONLY if it's in good condition, and that's why wire EDM is so maintenance dependent.
Having said all that, the OP will need to make systematic tests to identify what the source of the error is and eliminate the possible variables one by one.
The best way to achieve that is to tap into the expertise of the OEM's engineers; they will best know how to to stage the tests to get to the bottom of his complaint.
Sadly all other approaches are not likely going to be successful; so that's how and where I'd start.
Likely, the very first thing the factory technicians will need to verify is that the machine is in good shape and moving within spec...after that the detective work can begin.
Cheers
Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
