Consistent Material Thickness

This issue started with a Dowel Hole Burning thread and the feedback for it was very helpful. However, I think my issue is now more related to what I will call inconsistency in material thickness. The dowel hole that I am burning is not in a single homogeneous piece of steel. My 3" total thickness is actually made up of a sandwich of flat sheets of about 0.150" thickness each. The blanks have a starter hole that is laser burned.

Probably due to problems with the laser setup, some of the starter holes look pretty clean in the diameter while others have considerable “blowout” at the diameter on the side opposite of where the laser head cut. Once these individual blanks are stacked together for the EDM’ing of the dowel, there are inconsistencies in the thickness. For instance, 180 degrees of the starter hole might have a nice clean consistent 3" thickness due to the stacking of the 0.150" thick blanks. However, the opposite 180 degrees is where the blowout voids line up. These voids can be 0.030" deep.

Effectively when the wire is passing the portion of the hole that appears to be a clean 3" thickness it runs great. But on the opposite side of the hole the “thickness” that the wire sees may be as small as 1" thick. This “thickness” changes dependent upon the position of the wire. At 0 degrees for instance the top my be consistent for about an inch but the bottom 2" might be a void, and then at 20 degrees the bottom may be a consistent 1.5" and the top is a void.

Hopefully this makes sense. I am interested in anyone’s experience trying to cut something that the wire likely sees as being a variable thickness. Thanks as always.

I would lower my WT and up my WS. Probably adjust my SV up a little, lower the ON time and go up on the OFF time. Might cut slower but it might prevent the wire breaks. What kind of machine are you running?