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How long on an EDM to cut this part?

rsilvers

Cast Iron
Joined
Nov 11, 2003
This part needs 6 slots cut that are 1/64 wide. The steel is 4140 at rockwell 28c, and it is 0.047 thick for 0.566" and 0.255 thick for 0.134" inches. That is 0.700 total length of cut.
Evo9_3lug_front_001.sized.jpg


Is this an EDM job or a slit-saw job?

It seems like a wire-EDM could cut two slots at a time.

How many minutes of EDM time will this consume per part?

Thanks.
 
My calculations show that if the machine was running at 12 square inches an hour (which is based on 2 inch thick material I am told) then it should run in 0.8 seconds for the entire 6 slots.

(not counting setup and part rotation).
 
Good calculator, bad display...
Did you mean .8 hours?

My guesstimate is maybe 3 minutes/slot, times 3 indexing. Total machine time in the low teens.
 
No, less than 1 second as far as cutting rate. But I know the machine cannot move that fast, so I was thinking it would realistically be more like 30 seconds per part.

Machines are rated to cut 25 square inches of 2 inch thick steel per hour. That is for a rough finish. If it runs at 1/25 of this speed for a fine finish it should still be able to remove the required amount of steel in under 12 seconds. With indexing, I am guessing 30 seconds.

Factoring in human time to insert and remove parts, I was thinking maybe 30 parts per hour?

Way off?
 
rsilvers,

Those "in²/hr" numbers never really work out unless cutting in a reasonably straight line in at least 1" thick material.

Unless the operator wants to get slick with the programming, the power settings will have to be leaning toward the low side to prevent wire breaks in the .047" thick sections.

Not only that, but flushing will be extremely poor due to the nature of the part.

Not only that #2, <grin>, but if you're wanting to do a nice job on this part, the way to cut it would be run down the middle of the slot, then use trim settings to go down each side of the slot at lower power.

I'm sure Seymour nailed it -- ~10 minutes per part "floor to floor" to do a really nice job.

------

Follow-up... just saw your next reply.

Sounds as if you're looking to simply get the job done as quickly as possible. Yes... .013 wire could be used, and just crank it up and burn in there as quickly as possible and come right back out.

I suspect if you didn't care about finish or nailing the width of the slot, it could be cut in maybe 20 seconds. 2 indexings, and then change the part... maybe 3 minutes per part if you really didn't care how it looked and were just going for max speed.

Definitely not my style of wire work, ;) but there are plenty of shops that would probably jump on the job if the quantity was huge.

Have you gotten quotes from anyone yet, or is the query here your first attempt?


PM
 
I need it to look nice.

Yes, I envision one cut up the middle and then a cut up each side.

So doing it that way, and looking pretty nice -- 12 minutes? Even with a .013 wire? You can still make 3 passes with a .013 wire since the slot is about 0.016 wide.

No quotes yet. I just want to know what to expect and don't want the quote padded too much.

How are slots on collets cut??? I doubt they use EDM. Is the process they use lower cost?
 
Prec

Do you really think that slot can be cut in 20 seconds?
Not sure how? That would mean 2"/min feedrate in .510 " thick, poor flushing, interrupted cut....
Doesn't compute....
 
If nailing size is important, it would be better to use .010" wire and take a trim cut down each side. Using .013" wire won't leave anything to trim if you want a .016" slot.

I believe slots in a collet are cut with a slitting saw of some type.

What kind of quantity are you looking to get cut?
 
Seymour, you're right. I should've read his dimension a bit more closely.

I think using .013" wire, the .566" long at 2x .047" thick would probably take maybe 15-20 seconds?

.134" long at 2x .255" thick should take maybe 30-40 seconds? I'd imagine a power change in the program about .125" into the cut would be in order?

Should be able to back out of the cut in 15 seconds.

Maybe 1:00-1:15 per slot once things were really worked out? (definitely not on the first or even the first dozen parts!).

Got to index twice and do a part change. Now it's a 5+ minute part.

That sounds like it would be possible with big wire and no regard for surface finish.

I could be way off base though... I simply don't cut things where speed is ever the primary concern, and I've never run .013" wire (and hope I never do). ;)

I just saw that rsilvers posted once more and said that the cut needs to look nice. Kinda sounds like your original number was dead on!
 
.013 wire??? I'd like to see that done.

This is more like an .008" wire job. Don't forget that you have to offset the spark gap in front AND on the sides of the wire. .005-.007 might be a normal spark gap for .010 or .012 wire settings.

.013 wire with a .007 spark gap per side would be nearly double the .015625 slot he is trying to achieve.

Using .008" wire, with poor flushing and the stepped cut, on a submerged machine, you should see around .120 on the thin parts, and .080 or so on the thicker areas. So average .100"/min over .700" inches, you get rougly 7 minutes per slot, and three cuts, 21 minutes not including draining and filling the tank, and indexing the part.
 
Also, don't forget this is in soft 4140, a pretty crappy material to cut on WEDM. It's dirty and typicly contains icusions giving fits of time wasting wire breakage.
 
it depends on the machine,,, the setup, and availability of a rotary axis. In my shop, 1986 vintage H frame DWC110H, non submersable, no wire threader, I'd say 10 minutes per slice x 3 setups per part + 15 minutes each x 3 setups. total time about 2.0 hours billable with inspection and post blast.
 
MitsTech......What ARE you talking about?....ever hear of "zero offset"?
Hollistergc has it right, thank you.

harrytm, yes. Of course the program can be run in G40.

But that does not change the properties of EDM, and that is there will ALWAYS be a spark gap between the wire and the part, on all three sides; front left, and right. If the slot was not larger than the wire, than there could be no spark gap, and thus no EDM. It would also run in contact all the time. So you can run in G40, but the spark gap will still be whatever is listed as a rough cut offset in the technology files.

Yes you can run with very little overburn by running very low power settings, but the feedrate slows down to thousandths per hour instead of inches or feet per hour. I think the original poster here is looking for speed over any other factor.

harrytm, take a look at a technology data sheet sometime. You will see thousands of different offsets and offset combinations depending on material, thickness, wire diameter, numbe of skims, accuracy requirements, speed requirements, etc. All of those offsets are given (at least in Mits books) from the edge of the wire, not the center. The machine comps the center to the edge of the wire just like a mill when it reads G41 or G42.

Anyway, you can figure the total overburn on two sides by looking at the tech table for a given power setting, finding the offset, multiplying it by two then adding the wire diameter. So if you're using .010" wire, and the offset is .0047", your total slot width will be .0047x2+.010=.0194. This is, of course, for a rough cut only scenerio.
 
Well MitsTech,

I guarantee I could cut that slot using G41 and/or G42 using .010 wire with a rough and a skim cut and it would measure .0156" plus or minus .0002".
 
All of those offsets are given (at least in Mits books) from the edge of the wire, not the center.
When did Mits start THAT???
The technology sheets for our SX20 give the offset values to the center of the wire.
Same with the programming parameters in ESPRIT.

I'll second harrytm's claim. I'd use a "first skim cut" e-pack to rough the slot on center and skim from there.
 
Dave Haven, you are right MitsTech is mistaken. The offsets are from the center of the wire for Mitsubishi wire machines. I would use .008" wire for that job.

Bill
 
Aren't we sawing sawdust here? It's a slot. A measly little slot. Nothing more than a slot.
Can it be done with a .010 wire? Yes. .012? Prolly but not very accurately. .013 or .014? No way.
You want to make time? You ain't gonna skim it for sure. Rough on one side, skim back on the other. Will get around +/-.001 after a few cuts.
Want to make an accurate slot? Rough up on center, rapid back and skim on both sides.

It's only a slot. Not a .8 sec one though, nor is it a 2 hour one. 10 mins, give or take a little. It's a simple slot.
 








 
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