very small holes in Tungsten 1

[vono]

thread281-278396

It has been almost 5 years and I am still trying to get these small holes drilled in Tungsten ( see thread)
Basically ~5 - 10 micron hole in .300mm thick tungsten. Needs to be a straight thru-hole no taper and smooth edges. ( laser leaves a rough edge and a taper) I am using laser cut apertures but they are not perfect. Is there any new EDM technology? Has anyone aver rough cut 1st with laser then EDM to bore ?
Any help is very welcome

 

[CoryPad]

Did you try Photofabrication?

 

[vono]

I think that tungsten is too thick (0.300mm)for that!

 

[3DDave]

Can you draw a tube down to get the desired diameter and then braze the tube in place. (Because solving a problem by adding a similarly difficult problem is always a great solution.)

 

[CoryPad]

Tungsten at 0.3 mm is not to thick for photochemical machining. Look at the following link, your dimensions are standard:

http://www.elconprecision.com/photochemical-machining.html

 

[btrueblood]

Did you ever talk to National Jet, like unclesyd suggested?

 

[dgallup]

Corypad - It's not the thickness that is the problem, it's the very small hole size and the large L/D. From your link:

Minimum Hole Diameter 1.2 x Material Thickness

That would require a 360 micron hole, a far cry from a 5 or 10 micron hole.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[vono]

Yes - National Jet responded " Unfortunately, we are not able to make the holes that you have requested. I am sorry that we cannot help this"
I was able to have Midwest Tungsten EDM ~50micron holes with some success and that is about the limit. As I said in an earlier post the LASER cut hole are not very round and the taper is an issue. No one seems to have ever tried laser first then EDM after! Drawing a tube would work if I could get the size requirement: Tungsten disc ~0.300mm thick x 1.5mm OD plus tungsten is quite brittle.
Thanks for the help and ideas!!

 

[3DDave]

Look what they do to tungsten filaments. Brittle is relative.

 

[MikeHalloran]

All I can think of is to grind half a hole in half a disc, then braze it the hard way to another half-disc, and braze them to another pair of discs with the seams crossed.

Or something similar, without the braze, preferably keyed, and stacked in a little steel cup and crimped for mechanical retention.

OR, sinter the whole thing from tungsten powder to net shape.



Mike Halloran
Pembroke Pines, FL, USA

 

[MintJulep]

Would Electron Beam Machining be an improvement over laser?

 

[btrueblood]

I like Mike's suggestion for a powder metal version.

One more idea that we've used is to photo-chemically etch the hole in thin foil, then stack several such foils together in a fixture, and diffusion bond the stack in a vacuum furnace. Getting registration of the holes might be a trick.

What is the issue with the taper? You might be able to open up the taper slightly by using a slurry flow-honing procedure.

 

[vono]

Great ideas all- thanks ...I have never use that the slurry flow-honing procedure" might be an option. I have to look into that , thanks btrueblood. As for stacking in a fixture, I am working on two possibilities:
1) have several thinner wafers made and stack in a fixture
2) I am going to try to shim a 2 sets of half-rounds and set then 90 degrees apart is a tube fixture ( square hole is okay)