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Flying parts...

Jay Cee

Hot Rolled
Joined
Apr 24, 2006
Location
North East Ohio
As anyone who makes parts for things that fly knows, the heat effected zone is a major concern. I know wire has made huge progress in eliminating recast and micro-cracking in the past 4 or 5 years. Can the same be said of the new RAM's??
 
Also, does anyone have the contact information to an independent testing lab for recast depth and micro-cracking? Great Lakes area would be best. Thanks in advance!!!
 
I know wire has made huge progress in eliminating recast and micro-cracking in the past 4 or 5 years. Can the same be said of the new RAM's??
I don't care whose equipment it is...it is still removal of metal by a non-contact method utilizing an electric arc to MELT the work material away. It is much more refined these days, it is very thin these days, it is very controllable these days BUT....it is still there. The material has been melted and the portion that remains on the workpiece is re-cast...however minute. Whether it impacts your workpiece for its intended application is up to you.
 
This is from http://www.mmsonline.com/articles/020107.html


these results would be good enough for me... are the new RAM's using AC?


A Question Of Recast

Having been in the Wire EDM business for 25 years, Don has had to deal with the subject of recast in many instances. As EDM technology advanced, it became less of an issue, however, where critical applications are concerned, such as parts used in aerospace equipment, recast is still a valid factor and must be addressed.

Don explained that they do a great deal of prototype work, such as engineering projects for one particular company heavily involved in aerospace work. That company has a stipulation that any EDM work, if it goes into an aircraft part, must have no recast whatsoever, with a guaranteed 3X metal removal of the thickness of the recast layer. However, many times Wire EDM is used as a last resort, because there is no other way to produce the part, and no positive way to remove the recast layer. And if laps are used, there is no way of knowing if more material is removed from one side or the other.

Recently, EWT received a project, and Don explained to the company that he could not guarantee removal of the recast layer according to their stipulation. However, he suggested trial EDM machined parts, with the absolute minimum of recast, then cut apart and checked by the end user's metallurgy department. The trial parts were cut on one of EWT's Wire machines that incorporates full time AC circuitry. They employed several skim cuts that would insure the best results possible, and sent the parts off for metallurgical testing. The test results showed NO recast layer, and they got the job. Don commented that it would seem improbable that EDM could cut with no recast whatsoever, however, if metallurgical experts say so, it must be true.
 
Correct me if I'm wrong, but for flying parts the issue is primarily the micro cracking <HAZ>, rather than the recast layer.
The recast is mainly a dimensional issue, while the HAZ is structural.
Even in the early days, the recast layer was measured in tenths, yet the necessary conventional mat. removal was .004 for wire and .01 for sinker, so I thought that was for the HAZ?

Am I wrong?
 
Seymour... I have yet to ever see you wrong.

Maybe my customer is a bit simple. All I know is he wants minimal "recast". The job is really made for sinker as it's just a through hole. But "recast" currently dick-tates wire cut. The cost savings on MILLIONS (pinky in corner of mouth) of parts would obviously be huge if the RAMS have made the same progress with the AC power supply. I'm an idiot when it comes to latest RAM technology. Websites don't seem to mention anything about AC for Ram's. Hence, here I am asking the smartest guys on the globe.
 
Jay Cee
There was a rather lengthy article about HAZ and other EDM issue in an older EDM-Today magazine.
I'd be damned if I can find the magazine though, and there is no web-access for them.
You may want to call Charmilles or Fanuc direct. The reason for those is that I know Pratt & Whitney had their Wire machines in the past, so they may have something available for reducing the detremental effects on sinkers.
Also, there is Dan Tomalin who is a well respected EDM guru with very extensive knowledge. He is kind of like the Yoda of EDM and metallurgy, and I think he also wrote something about recast layer, HAZ, microcracking, generator types.
No phone# for him though, but if you E-mail someone at EDM Today, I'm sure they can help out with that.
 








 
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