Monday, August 30, 2010
Q - Is it possible to have a RAM-type EDM attachment on a WEDM? Would such a thing ever work?
A - Makino offers a fine hole sinker (EDGE2-FH) with a wire EDM electrode dressing attachment, but nothing more. The dressing attachment is a rudimentary wire drive system used, for example, to make a graphite rod into a triangle for making diffuser holes in blades and vanes for turbine engines. It runs off of the sinker generator. Wire and sinker EDM generators are different (electronics, waveform generation and shapes, etc.). Wire EDM typically uses much higher frequencies than sinker EDM. This is relative to duty cycle, based on the 'ON TIME' and 'OFF TIME' values, as well as voltages and amperage. Also, wire EDM typically uses de-ionized water as the dielectric, and sinker EDM uses oil. There's also a huge difference in the design of the Ram for sinker EDM and the upper/lower heads for wire EDM. I suppose a hybrid machine could be designed that would incorporate two generators - a ram for sinker, upper/lower heads containing flushing and wire guide components, and a selectable water/oil dielectric system - but I think you can see where this is going……….$$$$$$$$$$.
-Jeff-
Wednesday, August 18, 2010
Q - We’re looking to perhaps buy an EDM but we would use it for a variety of things. One of the main things we’d use it for is excising samples from billets of material, as well as forgings/castings. Most of the samples would be for things like tensile testing, fatigue testing, etc. In many cases, the layout of these specimens is somewhat complex, in which many pieces are taken from a billet in a variety of directions. In that case, as far as I know, a wire EDM would be best. But in other ways, sinker EDM would suit our needs as well. So my question is this: can a sinker EDM reasonably be used to take out specimens like that? Or would it need to wear away all of the surrounding material before you would get a specimen out?
A - From what you describe, I would have to direct you to Wire EDM machines. Sinker EDMs are used more for machining details and cavities. Using a sinker to cut out samples and coupons would result in large amounts of material removal around the area in question. Sinkers are also inherently somewhat slow. Wire EDMs (WEDM) would be the way to go here. Using WEDM, you would be able to remove a sample or coupon from a large piece of material fairly quickly, and with good results. WEDM would be useful as long as the cut can go through the entire thickness of the part.
-Jeff-