High volume though flush...

Can high volume flush increase electrode wear when using graphite?
I'm burning .15 down on a .375dia trode into a blind area. A tool maker here decided to do me a favor and make me trodes. He made them with through flush which I didn't feel was necessary given the depth. After not achieving the burn time he thought we should see, he came over and cranked up the flushing pressure/volume. It did nothing for the time what so ever. It did seem to wear the trode a LOT faster.
I know it seems as if I'm answering my own question, but he won't believe me until some of you experts confirm.
Can you help a brother out and set tool-boy straight???
Just enough flush to move the stuff around??
This application didn’t need through flush??

Tell him to keep his F%@&ing hands off the machine

That depth = no through flush, only jump.
Through flushing will increase electrode wear, especially at the through hole and the edges of the contour. Plus you still have to chase another electrode in there to get rid of the blasted "dimple".

Too much flushing pressure is as bad (if not worse) than not enough. The spark can get disturbed (read blown out) at the areas of highest flow thus causing uneven distribution of the power across the gap.

Greg

Use vacuum to flush with. I have been running ram EDM machines for 25 years, I would never consider burning without a flush hole using vacuum or pressure 1 or the other. What kind of graphite are you using and what kind of machine? That burn should take no more than 20 minutes to complete if the machine is set up right and the flush is properly set.

I have to agree with both Hollistergc and mcruff.

A low volume draw through the electrode always gave me better results on deeper holes and pockets in time, electrode wear, and finish.

That depth shouldn't have required through flush of any kind. Kind of counter-productive, as you discovered. Cross flushing should have been more than adequate.

Suggest you thank your "friend" profusely, but insist on "doing it yourself" from now on.

Depending upon the required tolerance and corner radius, this job might have taken only one electrode without a flush hole and using spindle jump flushing alone, and two at most if it required good detail (at a standard finish... let's say anything 24 VDI and above). "Tool-boy" didn't do you any favors here, but thank him anyway.

I'll agree that you probably didn't need it, in that application.

I do a lot of high ratio holes with tight finish and size tolerances, for example, 1/2" diameter 4" deep. On these parts, through flush is critical, but you have to be careful with the pressure, too much will slow you down, and cause excess electrode wear.

I do these with an on center hole from the back side, and an offset hole in the outboard end. Then I rotate with the "C" axis, to prevent the "dimple" that Hollistergc mentioned. In this type of situation you have to remember that the dielectric is trying to flow through the gap on the bottom, which is likely only a few thousands.

The reason suction works better is you are removing the debris up through the electrode, instead of pushing back up past the side walls, which causes secondary erosion, and possibly DC arcing. Cavities done with through pressure are more prone to be tapered undersize at the bottom.

Cheers!

Roy Solomon

Thank you all.
I will now be receiving a free lunch because of your efforts and his screw-up(s)... Quizno's sounds good to me. Mmmmm tasty... Of course I feel kind of bad having him pay since he was only trying to help me out in the first place... Oh well, a free lunch is a free lunch. And he did put his little hands somewhere he shouldn't have.
The machine is a Charmilles Roboform 35P. An excellent machine as far as I'm concerned. The graphite is the good stuff. Poco.. I have enormous stock piles of the stuff and use nothing but.
I haven't played with the vacuum style flush yet but it makes a lot of sense. I will most definitely make a point to add it into my job planning thought process.
Thanks again guys!!!

Don't be a sore winner Jay Cee. You never know when you might REALLY need his help.

I am a fan of Vacuum flushing... The problem with pressure flushing is the Hydraulic effect.. Just a few PSI on an electrode can exert a lot of force back on the ram.. on larger electrodes, it can even distort the electrode.. Yes, pressure flushing does cause increased sidewall draft..

Just wanted to thank all who recommended vacumm flush. Boy oh boy did that make a big difference. Cut over 20% off of the cycle time. Of course I then had to use those electrodes that Tool-Boy made with the through hole. And of course I then returned the free lunch that I got from him. Guess there really is no such thing as a free lunch... Thanks again guys. If your ever in town, Quizno's on me!

I have done a fair amount of experiments using pressure vs vacuum flushing.. I used to burn as many as 100 duplicate cavities, so time saved really adds up. Vacuum almost always proved better, as far as size control, finish, and time.

While on the topic of vacuum flushing, I think there are a couple of additional considerations which come into play when you are deciding whether to use it or not. Vacuum flushing, regardless of its undeniable benefits, also has its own drawbacks. When you are removing a considerable amount of stock, the very low volume of dielectric flow you'll get with vacuum flushing will also allow a great deal of heat to build up in the part... enough said. Also, if the electrode has much of an internal cavity through which you use vacuum flushing, there is a potential of igniting gasses inside the electrode. Unattended, this can be very damaging. Like every other part of EDM, there is a time and a place for this method... Choose Wisely!!

Vacuum flush
Clean filter
High quality graphite (Poco 3 or eq.)

These three rules in combination with a low pressure external flush to keep particulates away from the work will be best for more than 50% of your burn situations.

Another rule: It's volume, not pressure!

The rest is strictly experience with each individual machine as to what settings to use. There is an unknown balance between the arc and the flush. Remember that you are creating thousands of miniature controlled hydrogen explosions. The fluid will encapsulate the debris. The flushing moves it clear of the work. Pulsing the cycle may also be necessary to clear debris.

Unless you have a lot of draft on the sides of your electrodes, you are probably burning most of the time at the bottom of the electrode. Wherever you burn, you will have wear on the electrode (or buildup in certain settings). If you pressure flush you will be moving crud past areas you have already burnt which will cause overburn and wear on the sides of the electrode. Stopping mid-way through a burn and lightly hand dressing the electrode with a piece of 600 grit will knock off welded on bits that slow the burn.

While not perfect for all situations, vacuum flushing generally makes a cleaner burn and is better for finish electrodes.

If you want speed and accuracy with no arcing, you will have to pay attention to what the machine is telling you and nurse it through the burn. EDM sinkers should be in quiet section of the shop so you can hear the efficiency of the burn.

Don't worry, go slow and pay attention to the machine. Speed will come.

hi.
i am cutting 12 inches tall titanium on robofil
440cc , anyone outthere had encounter with this material,please give me some advice on:
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i am deeply gracefull.