Random corner erosion

[nlancaster]

This part is glued up titanium and ceramic, cut on our Sodick AG600L

Grounding clamps connect to all parts that are being sperated.

We WEDM the ID to .1574+/-.0005.

We then separate all the segments.

These should have sharp corners at the ID for each segment.

Mostly they do, but we seem to get way to many of them where in one section, not the entire vertical length, of the corner looks like it has had random arking and erosion on it.

Sodick suggested increasing tension and decreasing Flushing pressure but it still seems to have the same issue.

Bedra Cobracut TypeA zinc coated .006 wire.

New diamond guides, new carbide contacts.

Water is at 100,000-110,000 ohm/cm3 resistivity.

Filters are fairly new, with low but constant pressure on the gauge while filtering.

In the past we have tried increasing flusing pressure, flushing only from the top or the bottom.

 

[Madco]

Are you cutting inside->out or outside->in ?

Do you maybe have an picture of the problem or at least close up from the problem zone? I
Also understand if you don't want to post customers part.

I would cut from the inside->out, while reducing the power, or (depending on the thickness of the part) cut it with first skimming cut.

 

[nlancaster]

We cut the ID first, and then the slots, from inside to outside.

not a great picture but best I have ever been able to manage.

The slot in the picture is around .00935 in size.

 

[nlancaster]

The part is 2.95 inches tall, with a total cut length of around 2.5 inches.

 

[plastikdreams]

Need a better picture. Could be secondary edm from something. Maybe find a better way to hold things together, like in a fixture. Of course if they are always different shapes this could be an issue.

More pics needed.

 

[nlancaster]

It is a ceramic ring with an uncut part glued into it. stays glued after seperation. Best picture I could get, its really small and hard to see inside.
we have a clamp that screws on with pressure plates against the individual segments to keep them grounded after separation.

 

[plastikdreams]

I mean it could be random arc wander. I know they said reduce the flushing but my experience would say to increase it. That it doesn't happen every time is odd which leads me to believe it's arc wander maybe by the nature of the material. But really my guess is as good as yours, or anyone at that matter.