burning multiple tiny slots...can I pull it off?

[implmex]

Good morning sinker EDM guys:
I've been handed a challenging little job in the hope I can do it.
6 slots each 0.012" x 0.040" through 0.200" of 420M tool steel.
Here is the electrode wire cut out of copper tungsten.
Each blade is 0.010" x 0.038" and 0.400" long.


No room for orbit... wand and jump flushing only.
What do you think my chances are of pulling this off?

I'm going to try it this afternoon.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

 

[plastikdreams]

I'd make another electrode a) just in case and b) for a possible finish burn. 420 can eat ectrodes, especially thin ones. Biggest issue will probably be corner rounding.

But I know you can do it.

 

[SteveEx30]

Should be fine with 1 trode depending on what you have for edm !

I definitely wouldn't pass 2 trodes thru there you made the right call with 1 taller one.

 

[wesg]

If it's for a die, I would have sectioned it ;-)

 

[implmex]

Hi All:
Thanks for the commentary, it's appreciated.
These are for fluid passages in a miniature hydraulic valve, so no great precision requirement.
My main concern with stuff like this is getting DI oil down to the business end.
It's a 20:1 LD ratio, so I do have a long way to go.

It's been burning for an hour now and I'm down an eighth of the way, so it's going to be a slow burn.

I don't have a very modern sinker...it's an old Hansvedt MS4 Foreman from 1996.
So it's pretty primitive but with luck I'll get through it.

Just for interest, what would you guess a burn time might be on a more modern machine?
Nobody cares about finish, or about dimensions, or about corner erosion...just a simple burn much like you might make for a wire EDM start hole but rectangular(ish) rather than round.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

 

[SteveEx30]

1 to 1.5 hours be a guess

If tolerances were that loose I would have asked how wide you could go. Every couple thou would help.

 

[implmex]

Hi SteveEX30:
Excellent point!
This is for an Alpha prototype, so there is really no tolerance defined yet
Perhaps "as Skinny as Possible" is a way they can express it best at this point.

No one knows what we will be able to get away with.
Nobody even knows if this thing should be 0.200" thick or 0.020" thick which obviously means very different things as far as what it's going to take to make it.

Alpha prototyping with this particular customer is often like that...we guestimate what we think might be needed and then we try to build one and destroy it to find out what the limits are.

They have a misplaced confidence in what I can build and their engineers are all very young in experience so I get some pretty extreme requests.
This one I thought I could take a kick at.

But your point is very well taken, and if I have to orbit the trode to get it to cut, I will.
That will become the new design limit for these features and then they can decide if they want to revise or prefer to abandon the design and start again.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

 

[plastikdreams]

I used to burn a .360 od graphite thru coolant electrode in hardened 420ss down about .250 in around 20 minutes with orbit...granted that was on a 750k mits sinker with all the bells and whistles lol.

 

[SteveEx30]

As an owner of several Mits Sinkers I can agree they are great machines.

If that detail was just a bit thicker even .014" wide I'd just cut a graphite trode and sink that detail before I was done my morning coffee.

 

[BOB-OO]

I bet its done and perfect Marcus!

With my many minutes of EDM experience, the EDAF would likely do it in a bit over an hour. The z rapids really do seem to help flush until depth exceeds .7"-then things slow down.

We cut these little guys about .250" thick, S7 & M42, much easier to flush then your part, memory is slipping on the cut width .014"?, took about an hour.

We're all eternally grateful to you for suggesting Telco!!

 

[bob]

I tried it, made electrode from brass because it was handy but not ideal. Started the burn seemed ok but burnt the tips off almost immediately. Better electrode material and less amps might work.
Bob

 

[Matt@Hi-techEDM]

Should be fine with 1 trode depending on what you have for edm !

I definitely wouldn't pass 2 trodes thru there you made the right call with 1 taller one.

I’d have to agree, the one electrode at a longer length will work
Perfectly fine and eliminates room for error assuming you don’t manufacture your own electrodes

Hi All:
Thanks for the commentary, it's appreciated.
These are for fluid passages in a miniature hydraulic valve, so no great precision requirement.
My main concern with stuff like this is getting DI oil down to the business end.
It's a 20:1 LD ratio, so I do have a long way to go.

It's been burning for an hour now and I'm down an eighth of the way, so it's going to be a slow burn.

I don't have a very modern sinker...it's an old Hansvedt MS4 Foreman from 1996.
So it's pretty primitive but with luck I'll get through it.

Just for interest, what would you guess a burn time might be on a more modern machine?
Nobody cares about finish, or about dimensions, or about corner erosion...just a simple burn much like you might make for a wire EDM start hole but rectangular(ish) rather than round.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

What was your total run time in the end?

 

[SteveEx30]

I tried it, made electrode from brass because it was handy but not ideal. Started the burn seemed ok but burnt the tips off almost immediately. Better electrode material and less amps might work.
Bob

This is why I love the Fuzzy on the Mits machines... that stuff just never happens..

 

[RJT]

I'd guess about 2 hours to burn it. How long did it take to made the electrode?

 

[RJT]

We have used our hole popper with .012" diameter tubes, then tread a .008 wire and wire EDM it. It's tough to get the wire in the middle of the hole to start, but it can be done. Hole popper is not that accurate.

 

[implmex]

Hi All:
So a progress report.
Almost 10 hours to get down 0.200".
I'm never going to be able to bill that much time on it, so I'm thinking I'll bill the average of what you guys are telling me it would take on your machines.
The trode took an hour to burn on the wire

RJT, I thought about hole popping it and then wiring it, but I don't have a hole popper so I'd have to send it out for that.
If I do that, I may as well send the whole works out.
I don't care that much how efficient or not it is...it just noodles away in the background while I do other things.
So I let it clunk away.
Now it's on the wire for all the other features it needs.

Cheers

Marcus

 

[RC Mech]

On my 1995 Chevalier sinker I’d have expected about 8 hrs. I’m historically under on time estimates.

Great thinking RE the longer trode for finishing. Not a common occurrence where you could get away with that.

 

[RJT]

Still interested in how long it took to make the electrode? We do very little with anything except graphite and copper infused graphite.

 

[implmex]

Hi RJT:
You wrote:
"Still interested in how long it took to make the electrode?"
One hour on the wire, but I did already happen to have a piece of copper tungsten already squared up and roughly the proper size.

I avoid graphite because I'm too cheap to put the proper means in place to control the dirt.
I cannot personally tolerate the aftertaste of copper graphite either, so I avoid it too, in spite of its many benefits.

I could probably have ground a graphite trode in less time than it took to wire one from copper tungsten.
But like everything else in my (retired) world, I don't have to care all that much so long as the wire can run unattended.
I don't need to make time and I don't need to make payroll anymore either.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

 

[implmex]

Hi again everyone:
Just thought I'd post some pictures of the completed slots and the used up electrode.
I still have other top secret features to finish so I can't show the finished part, but here you go:




All things considered I'm pretty pleased.
Especially gratifying is how little of the trode was consumed...copper tungsten works pretty damned nice for stuff like this and it's a lot easier to wire cut than graphite is.
The slots are tapered by almost 0.001" per side though...fine for this job, but hopeless if this were for a punch die

So overall, I'm a happy dude!

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com