Sink Electrical Discharge Machining

[diarmaid]

Hi,

What is SEDM?
What do you use it for?
What are its advantages/limitations.

Just asking after coming across this:
http://www.camtronics-cnc.com/
(SEDM in 'Products' section)

[cdlenterprises]

It might be referring to a traditional or ram type of EDM where the electrode is "sunk" into a part vs. a wire EDM that uses a wire to profile. I've heard these machines referred to as "sinkers" many times...

[diarmaid]

Is that the type of machine used for cutting foam?

[matsuura]

no

it's used cut everything that cunduct electricty .we use it to cut hardened steel and weird shapes.

excuse. i dont write much often in english

den

[cdlenterprises]

An EDM(wire or otherwise) can cut any material that will conduct electricity. It basically works like a gigantic spark plug. Electricity is fed through the electrode(usually copper or graphite) When the electrode comes close to the part, the voltage in the electrode causes multiple sparks to "jump" the gap between the electrode and the part, thereby eroding or cutting the part. I must admit, I've never heard of or seen anyone cut foam on one...

[matsuura]

this is a foam cutter.

http://www.homecnc.org/index.php/Cheap_Foam_Cutter

[diarmaid]

Thanks all. I knew what a foam cutter was and thats why I asked. It didn't seem like it would be used for cutting foam. Why use an EDM instead of a Plasma Cutter or milling machine, is there a specific niche that it fits that cant be done with another machine? Thanks.

[CNCgr]

Originally Posted by diarmaid Why use an EDM instead of a Plasma Cutter

Because EDM can do 3-axis vs the plasma cutter's 2-axes

Originally Posted by diarmaid or miling machine

Because it can cut in hard to reach spots (e.g. odd shaped undercuts) and doesn't care about the material hardness

[smoa1980]

sinkers are used to do a lot od mold work. you can burn a sharp internal corner. The are very acurate.

[Geof]

Originally Posted by diarmaid .... Why use an EDM instead of a Plasma Cutter or miling machine, is there a specific niche that it fits that cant be done with another machine? Thanks.

EDM can cut fully hard tool steel which is more or less impossible with a milling machine. Plasma cutter can cut hard material but is limited to thinner material than EDM is much less accurate and because it melts the material away it leaves a heat affected zone adjacent to the cut surface. The material adjacent to an EDM cut is pretty much un-affected. Sunk EDM can do weird shaped through holes or blind holes that could be impossible by any other method.

[cdlenterprises]

EDM machines are extremely accurate with some machines approaching grinder accuracy. They are generally special purpose machines and not all shops will have a use for them. Unlike traditional milling machines, EDM's never touch the part and therfore leave the cut surface stress free. They can cut extremly intricate features, such as thinwalled parts where a milling machine would cause vibration, square holes with perfectly sharp corners, and odd shaped 3d contours to name a few. A sinker EDM like the one that started this thread, can be used to finish a mold or die cavity and eliminate hours of polishing time. A wire EDM....well just think of a guitar string that can cut 64 HRc steel... Charmilles, Fanuc, and Mitsubishi are some of the larger EDM manufacturers. Check out their websites for more info....

[ZipSnipe]

hey Diarmaid, I just started working at a tool & die shop, they have 4 different edm machines, I have not seen them running but I have seen the results, and they are amazing machines, cut thru 4" of aluminum like butter, very smooth finish. I told the boss to call me when they are goimg to run edm again and I,ll come in early just to watch. :-)