Flushing tall parts

Hi all, here's the description.

I am burning Inconel 718. The part is 4 inches in diameter, and 6.75 inches tall. I have a .040" start hole 1.75 inches off center. I am burning out to 1.8" radius, and then a full 3.600" diameter cut. Basically making a tube.

My machine is a Mitsubishi FX10K, and there is a variety of information on setting the upper and lower nozzles, some of which is contradictory. The instructions range from leaving a .002" gap, to a .012" gap. They seem to lean toward a smaller gap on the bottom, than on the top. The rate is set by volumetric flow meters.

I'm not worried about accuarcy, I'm just roughing the parts for the lathe department. If the head or lower arm spring from the pressure it would not be a problem. On the Agie's I've run in the past, you would put the nozzles right on the part for maximum speed. The 315's had a floating flush cup, and the newer Challenge had one with an integrated rubber element to help facilitate the same thing.

When I try doing that on the Mits, it seems it's sealed too tight, with no room for the debris to exit the kerf. What seems to work best so far is the lower nozzle at a .002" gap, and I start the upper nozzle at Z+.005(plus a .002 gap)and use reduced settings until I've burned far enough to let the flush come out of the kerf behind the nozzle. Then I move the head down to Z zero, and change the technology settings.

Using the above method keeps the flow between 3 and 4 liters per minute. I have burned a couple of these so far, but I have 75 more to do, so any suggestions would be greatly apprecited. I'm using OKI PZN .012" wire, I'm sure I'd do better with something zinc coated, but my boss wants to keep the consumable cost down. TIA.

Cheers!

I have a CX-20 and I normally set the lower head at .006 below the table,and if I need to shorten that distance I use the nozzle shims (.002) provided.I set the upper at .008 -.006 .
I am cutting an 8.00" tall part as I'm typing ,The lower head is now .0045 below the table and the upper is set to.008 above, she's old and less powerful than the FX but I am cutting between .012 -.026 ipm. (using 6.00" settings,8.00" not in book)
Flow nozzles full open.
Hope this helps.

I am cutting a 10" high part stainless steel at .850 inches per hour or .014 ipm on a Charmilles 310

Thanks for the replies.

Customill, you are getting 8.5 square/hr. What I'm doing so far is just under 11 square, so I souldn't complain <G>.

Sharpe428, that confirms some info I got from Tom Frick at Intricate EDM, who used to work for Mits. It seemed counter-intuitive to me, but I've been trying larger gaps, and it is giving me better results, more speed, less breakage, it even sounds bettter!

My latest attempt was 7:20 for 12 inches linear, so I guess I'm doing ok for that machine. For the record, my technology book only goes up to 6' tall for .010 wire, but has settings for .012 wire (which is what I'm using), uo to 17' I think. Thanks.

Cheers!

Roysol,
Just curious, are you using the PM option on your FX-10? I love that thing... Set-it to +5 and walk away...

CustomIII,
first.. why does everyone call you "Customill" second... doesn't your 310 have a cycle that automatically sets the upper head to the perfect flushing height? I'm curious as to what the machine detected "perfect height" is??? Wonder what it looks for? Max pressure before back-pressure??

Jay Cee, I have used Power Master for what I thought it was mostly intended for, thin parts, and parts with varying heights, which means bad flush, by definition.

I have not tried it for "regular" parts, do you think you do better this way than the "fixed" settings?

As for my mistake with "customlll" (sorry dude), I think it's that human thing about making sense from disorder. If what we see does not conform to our expectations, our brain is likely to make it so. There was a study recently about reading words where only the first and last letters where correct. Even when the middle was jumbled, most people could make sense out of it.

Cheers!

You have to really think about "consumable cost" when doing burns like this. Is the cheaper wire really cheaper if it has to run for 10-40% more time, thus using 10-40% more of your "cheap" wire?

Not to mention electric and, perhaps more importantly, expensive machine time that you could be using for another paying project. I'm not saying it WILL make a difference, but when you have such a time consuming job, it's worth trying for sure. You might even be able to get a few wire vendors to send you a sample spool. What have you to loose?

Yes it has an automatic hieght. But how it works is when you do a nozzle set up you measure a piece, install it in the machine, move the top head down till you have the pressure you want, then post the height in the machine, now when you put a different hieght part in you just post the hieght of the part and the machine goes to that hieght and the machine will have the same clearance between the head and piece so you will have the same pressure. No autmatic pressure sensors. CustomIII comes from our logo, it is Custom with 3 slashes. So thats where that comes from. I just looked, it has 4 slashes. I talked to the tech guy at Charmilles and 8 square inches an hour is where it should be at for 10" thick. I played around with some settings and I am almost at 9

Thanks for the suggestion, MitsTech. I know the math pretty well. My circumstances are different than most Edm shops.

I'm support for a production machine shop. I do tooling for the sheetmetal department, and some tooling and fixturing for the lathe and mill departments, and a fair amount of piece part production, usually things that have signifigant milling and turning, but some feature that requires Edm.

I have one wire, and one sinker, and I haven't run ethier one to capacity in the 4 years I've been here. Decreasing burn time by using more expensive consumables would just give me more hours per year when the machine is sitting empty.

To make it pay off the burn time would have to increase by the same amount as the percentage increase in the cost of the wire. Based on the results I'm getting now, versus what can generally be expected from this machine, I don't think there's any chance that could happen. Have you ever seen an FX10K burning 18 square?

I did try the H.E.A.T. wire from Edm Sales in a bad flush one off job, it did seem better. On the other hand, with a 1.5KG spool, it's not much of a test. Thanks again for your input.

Cheers!