Wire EDM Finish

Hey guys I have a question about a finish I am getting.
I have a form I am cutting in a piece of A-2 Rc-58 and .750 thick.
Tolerance is fairly tight ±.0002. I’ve cut one and it turned out good except I have one minor issue I don’t like.
I have some slightly visual lines on one side of my part. This side of the part hangs out into the tank while I am cutting. You can not feel them nor do they register with my indicator.
I have a couple ideas that it might be, on the other hand I don’t really know, I monitored the cuts and was happy with how the machine was cutting.
Could it just be my flushing and a little vibration going on? Any thoughts are appreciated, Thanks

Just an update if anyone is interested…

I did lower my flushing just a little bit since that leg of the part hung out in the tank a bit, and also on my final skim pass I took my SV down by 1 to make my gap slightly smaller, which in turn makes the SF a little faster. I use PIKA conditions on my final passes, literally just for surface finish to make it look pretty.

This seemed to take care of the lines I was seeing. I figure since I was just basically shining up the surface on my final pass that my flushing was giving the wire a little bit of vibration and my SF was somewhat slow.

Just some more food for thought, I’ve personally had some similar issues in the past where some very obvious lines were showing up cutting some heat-treated 440, not detectable with an indicator but still there after polishing. After a lot of head-scratching took it to the microscope and discovered little nodules of what seemed to be chromium or carbide. Invisible to the naked eye but large enough for the wire to cut differently when it passed over them. Every time I see some lines made in parts my first reaction is to study them with a microscope now.

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Hey thanks! I never would have thought of that.