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Burning from both sides???...

Jay Cee

Hot Rolled
Joined
Apr 24, 2006
Location
North East Ohio
I recently quoted a job for a customer that gets a formed plunge EDM'd into both sides of the part leaving a .005" thick wall of material left between. The customer told me that their currently supplier was holding the part tipped up and burning both sides at the same time. Huh???
Ok, lets assume that we have two separate power supplies and two separate CNC's enabling the physical movements possible. Doesn't the physics of the spark itself render this burn impossible?? Maybe if the two power supplies were linked as to always have one on the off cycle while the other was on... This sounds like an extremely complex machine for a nitch application. If it's even possible... Any one seen such a beast?
??
 
Jay,
At one time (early 90's). Makino had a 2 headed machine... Course it was a huge machine and I don't think any of them were actually sold, at least none in the US.
Separate controls, separate generators etc... Basically 2 machines with a common casting and single work tank.

I also know of one customer who made their own work tank and had 2 machines using the common tank and table. Again, very big machines. Course you didn't mention the size of the part.
 
I am guessing that what your customer means is that both sides are burned in the same set-up, or that the same electrode even burns both sides (while orbiting, of course) at the same time. This is routinely accomplished by producing electrode features oversized on the I.D. of a "hollow" electrode, (imagine that we're burning detail around the end of a core pin, or a forming punch) and orbiting "down to size". In the EDM trade, most refer to this method as a "cap-over" burn. Now, to address simultaneous yet independent burning of the same workpiece: yes, this is also possible. Some builders have played with dual-wave generators and even independent heads with dual generators, as mentioned above. Since each generator is producing its own wave, a common ground (or work table) does not affect the independently generated waves (In much the same way that stereo headphones utilize only 3 conductors at the input, but give you two entirely independent channels). Multiple head machines are still built and sold. Off the top of my head, I know Makino and Belmont (Maxi-cut) both currently have offerings in that arena.
 
I do a series of parts that have thin floors, .010/.015". Thet are stainless, titanium, or inconel.

Depending on the ability to "heat sink" them, internal, and external flush, they have a tendency to move, ie "suck up". I've found I have to leave more generous stock allowances and conservative burn settings to get them to come out ok.

The advantage of doing this part with access to both sides is so you can use a "rocker" orbit, and work the cavaties in at the same time, instead of finishing one side, and then trying to finish the second side.

Cheers!
 








 
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