Burning the perfect hole

[sungaikantan]

Hi metal burners. This is my first post, so please go easy if Im asking a basic question. I tried to find previous threads about similiar problem but could not find any. But Im sure this is a a common problem for beginners like me.

Im working with Agie Charmilles wire EDM and would like to burn cylindrical rings with internal diam and outer diam of 9mm and 18mm. The problem I have is the unwanted marks on the entry/leaving point of the wire on the perimeter of the hole. There always dig in marks or uncut material when the ring fell off.

I got this idea of either putting a tangential radius at the entry point, before the wire cut the actual ring, so that the transition is smooth. I also think I should over travel when cutting the ring, but there is an issue of holding the ring when the profile is cut.

Do you have any ideas? I really need a smooth rings!

[sodickappsguy]

if the ring has to be "perfect" a few extra steps will go a long ways. On the ID cut the Id smaller than the target by about .01-02 of an inch to remove the slug. Once you have the slug removed have the program burn at normal offsets for the target Diameter. With these passes (yes the more the better) arc onto the part and arc off the part. at the end of each pass rotate the program 45 Degree so that each pass will travel over the previous witness mark (ie 0 degree,45 degree,90 degree,135 degree 180 degree ect). I am not familiar with charmillies power settings but with a Sodick i rough with larger offset and then use a Water5 tech (high energy rough with 3 skims and one Pika pass) and have had several customer parts come out .00005 or better when checked with a CMM. Depending on the material you may not have to do the first pass that removes the slug with additional offset and the number of passes may also be less. Are you also trying to make a "perfect circle on the OD?

[sungaikantan]

thanks for the reply. I have done similiar what you have described, thanks to your help, and the I got a considerably very good hole. The entry marking on the surface of the hole are not visible anymore and the dimension are true towards whats I specified. I was planning to rotate the program but since it came out good I dont find it is necessary in my case.

Now, Im trying to get the OD. Its seems the entry point is worse than the ID. Im trying to put a paper shim (spacer) so it will hold the ring in position, while the machine cutting the last bit without the ring falling down. I may use a metal shim so it will let current through for the cutting.

I will appreaciate any help on this one! cheers

[RICHARD ZASTROW]

We put silicon caulking in the finished part of the cut. If the dropping part was too heavy for the caulking method, we CAREFULLY placed small wedges into the cut.

Then there was the "Super Glue" method. Glue supporting strips accross the cut area after the wire passed by.

Dick Z

[sungaikantan]

hmm.. that is interesting Richard. I will try to use the methods you suggested.
I tried the paper shim and failed due being soaked by the dielectric.
I imagine the superglue would work. I just hope the conductivity will not be an issue. Cheers