Help!
we have been offered a large contract to wire EDM pcd, we've never cut anything like this before, but we know companies that do. Our machines are Hitachis, none are submerged.
Does anyone have any suggestions as regards power settings etc, we've tried a few settings without much success. We are pretty sure we can do it, but could do with some pointers.
Thanks in advance Mark...

What's pcd?

Klox

PCD=polycrystalline diamond

Wjman,
I did not know that these stuff could be wire-edm. Where are PCD used in the industry? Please fill us in on this topic.

Klox

Klox,
PCD or polycrystalline diamond is used for cutting tools, that have to cut very hard materials, ie rock or more commonly hardened steel, we use PCD tipped inserts on our lathe to turn hardened metals. I'm sure that's just the tip of the iceberg, maybe someone else can elaborate more. The PCD we are trying to cut is bonded to Tungsten carbide and they are removable inserts for a rock drill. BTW I've sent "chikara" an e-mail.
Talk to you soon Mark...

PCD blanks usualy have a tungsten backing or substrate that supports the diamond. The diamond is sintered with cobalt which is what actually is eroded in the edm process. The wire actually travels around the diamond crystals. So the process is dependant on several factors. The grade of diamond (cobalt content, crystal size). The generator on the machine.

How well does your machine cut carbide ? This may be an indication.

I think you are going to have to do some test cutting if you have an older unsubmerged machine and dont have tech support or existing technology files.

If your machine cuts it without excessive wirebreaks, rest assured the cut speed will be slow.

CAMmando,
The older edm machines with DC generators normally "battle" to cut materials (non ferrous alloys) out of the ordinary. For example you get discolouration when cutting tungsten & Ti. The newer AC generators cuts faster & better! I have read about "intelligent arcing adjustment" on new edm machines that keeps generator settings optimal and prevents the electrode from shorting out. Some machines have Digital dual voltage (high/low voltage). The current being synchronously discharged to ensure faster material removal rate, uniform suface finish & lower electrode wear.

I haven't come across PCD, if i have to cut it i would start out for settings for Ti/ tungsten and play around..........

Klox

Thanks CAMmando,
I know about the sintering process, our machines cut carbide quite well, so perhaps that's the approach ie using carbide settings.
Thanks again Mark...

Thank you also Klox,
Our replies crossed, our newest machine has an AC generator (still an unsubmerged machine though). I will try the carbide settings and let you know, cause I know you also have a Hitachi machine.
Thanks again Mark...

Klox,
PCD or polycrystalline diamond is used for cutting tools, that have to cut very hard materials, ie rock or more commonly hardened steel, we use PCD tipped inserts on our lathe to turn hardened metals. I'm sure that's just the tip of the iceberg, maybe someone else can elaborate more. The PCD we are trying to cut is bonded to Tungsten carbide and they are removable inserts for a rock drill. BTW I've sent "chikara" an e-mail.
Talk to you soon Mark...

Wjman, in actuality , CBN (Cubic Boron Nitride) is used to turn hardened metals (best results are seen when used on materials over 45 RC), whereas PCD (Polycrystalline) is used to non-ferrous applications (aluminum alloys, copper alloys, metal matric composites, hard plastics, carbon-fibre, sintered tungsten carbide, and precious metals).


I hope that this will clear up any confusion as to where PCD and CBN tools can be applied.

you need a high voltage setting, like over 200 vdc

try some copper underneath the pcd....(well clamped)

i use modified carbide settings cause you are basically cutting the bonding agent not the diamond. The settings are still kinda black magic cause you settings and finish depends on what size the diamonds the MFG is using. Micro fractures can happen just like in carbide. Oilfields love pcd and woodworking plants use pcd over carbide cause of the tool life.

if you want to cut pcd or cbn, get and old andrew ef (biege)series machine,
it is the defacto standard for cutting diamond.......hands down.
i can modify them with a new pc based cnc system, instead of the old pdp8.

i have 6 customers whose ONLY business is pcd and cbn cutting, and they have about 40 andrew ef's between them doing this job.

these machines can be had for as low as few hundred bucks, and edm network has full support on them.

the old agie 312(?) machines work excellent for this also.

these machines cut pcd/cbn without any modification at all, they cut it like soft butter.

If a grade of PCD can be used with a smaller grain size this should be easier to cut and have better geometry. I am currently cutting with .004 wire and if needed to a finish of 7 to 8 ra. Have had trouble when cutting small radii (ex .0008 r).