What type of material do you need to drill?

Steel

Probably ECM is suitable... using tubular electrode from copper.

In ceramics (yes, not steel, I know) you'd be using diffusion-bonded waveguide technology - 2 very flat and polished surfaces that one has a slot formed in it.  These are pushed together and diffusion bonding takes care of the rest.  This can generate holes of the diameter and over the length you indicate. Not sure if something like this can be applied to metals.

With this machine may be possible:

http://www.gfms.com/content/gfac/com/en/Products/EDM/hole-drilling-edm/blueline/sd-20.html

See also: http://vacaero.com/information-resources/the-heat-treat-doctor/1467-vacuum-diffusion-bonding-by-design.html

Forming a slot in a substrate is easier (e.g. with laser) than drilling a hole. The components can then be (diffusion) bonded together.

Laser Drilling...

Dear Dr. Schulze. Though I am comparatively new in this research area, still I would like to put my opinion. As far the technology has developed, such a deep hole drilling is never possible by EDM, ECM and ECDM. Since your require a hole of approximately 750 aspect ratio and that to in a steel plate, only LIGA processes seems to be feasible. Recently, I have found one article published by National University of Singapore in which the researcher have fabricated micro-holes of up to 100 aspect ratio on a metal plate. If required I can link you to the article. Hope this processes will be suitable for your purpose as it fulfils your another requirement of time constraint also.

750   aspect ratio is difficult to achieve  by ECM , ECDM, or EDM due to the difficulty of  delivering the machining medium  through the inter-electrode gap, Moreover  the accuracy level you are looking for  cannot achieved by ECM  or ECDM due to the side machining effect  which enlarges the  hole diameter.

LBM is impossible  to do that hole  depth because the removed vapor  will prevent the beam from entering the deep hole. the diameter will not be as uniform as EDM which is the most accurate compared to ECM, ECDM or LBM.

Thanks for the interesting comments

A small query to Dr. Jhavar.

Can you give me a publication that laser drilling conducted in these depths? Or they have their own experience in this area?

For hole diameters greater than 0.5 mm, I know that it comes with the EDM -Drilling.  But Laser Drilling ??

Laser in piercing modality can drill only a few milimiters. In another sense is very difficult to control the diameter and shape of the hole.

I had the possibility to see in Mitutoyo Brasil holes made by EDM drilling of 0,3mm and 150mm of length.

Agie Charmillles said in your web page than you drill needs can be possibles.

Laser Hole Drilling

http://www.laserod.com/applications/hole_drilling/

Small Hole Drilling

http://www.potomac-laser.com/services/core/micro-hole-drilling/

The Many Parts of High Precision

http://americanmachinist.com/features/many-parts-high-precision

High Speed CNC Milling & Drilling

http://www.cidraprecisionservices.com/cnc-milling-drilling.html

Primer on laser micromachining polymers

http://medicaldesign.com/contract-manufacturing/primer-laser-micromachining-polymers

http://www.laserstoday.com/2015/06/drilling-of-cooling-holes-by-using-high-power-ultrashort-pulsed-laser-radiation/

The information attach for Mr Jhavar shows that the holes made by laser have an taper shape, and the length is small, in all cases minor than 8mm.

Yes, Perfectness of the hole may vary with parameters. After all that's what for manufacturing scientists come into picture....:) 

The case presented is having very high aspect ratio. An aspect ratio up to 100 is reported in many articles. However article http://link.springer.com/article/10.1007/s003399900218 shows laser drilling can produce aspect ratio up to 600 (mostly in polymers). 

You can consider following publications for reference:

http://scitation.aip.org/content/lia/journal/jla/27/S2/10.2351/1.4906470

http://spie.org/Publications/Proceedings/Paper/10.1117/12.2222662

http://link.springer.com/article/10.1007/s00339-007-4300-6

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-18-2-566

http://link.springer.com/article/10.1007/s00339-002-1511-8

High aspect ratio hole like this would probably have to be EDM. Not even sure of the feasibility as I have never tried something as ambitious. Discussions with a specialist manufacturer would be the way forward. I don't believe any laser process could do this. If there is I would love to know!

I also think that the EDM provide the best ways to solve this problem, especially since I have a metallic material as a boundary condition. I knew many suggestions already, but just knew that they were used for a few millimeters deep.

Even something unclear if one can use the ECM.

Once again thanks for the lively discussion.

ECM has limited depth capabilities. Also since it takes time, the material at the surface gets a lot more exposure that the material down the hole so features are tapered and have rough edges.

I have seen EDM used for drilling long deep (ish) holes in turbine blades but larger dia holes not nearly so deep. I would imaging controlling a long thin electrode would be an issue (if you could make one straight enough. If you ask a manufactures let  me know what they say.

New one on me. Sounds interesting but the OD of the hole is only 200um. That would require an electrode tube of about 200um OD with an ID large enough to get the electrolyte down. You think the process would scale to that?

Exactly the question of the electrolyte supply in the gap, and particularly at large depths presents a problem. Of course, one can overlay the actual feed with an oscillation or to work with even much smaller wire diameters, which again limits the stability.

In the first orientation, it would not be so critical if entry hole and exit hole would differ. The exact requirement would apply more to the exit hole.

Quaestion is how many holes do you need. There is a complex solution which could work: make a larger hole and put inside a 200µm tube. This will reduce the L/d ratio and allow an easier manufacturing. With such a high ratio (750!) two problems will appear: the circulation of the fluid AND the relatively lower impedance of the frontal area versus the lateral surface. The last will make local energy density difficult to obtain. The high ratio puts as well the axial stability ptoblem push force will have to be VERY small so that combined with high resistance of circular gap in the pumping process will impose a low frequency.

Hi Nick,

I think your answer refers to EDM. The problems you have shown good flushing and gap width. With the reduction of the aspect I'm not quite compliant, because the problems of EDM aan remain a wire. Therefore, to solve the problem is not relevant how many holes I sinking. If I find an acceptable solution, then a tool with the arrangement of several tools is determined to improve my productivity. But I must note that I have a high wear in EDM Drilling.

Dear friends,

Thanks again for the good indications for deep drilling at high aspect. Interestingly, I have to say that most of the answers rely on publications or manufacturer brochures. Therefore, I would extend my question of whether someone has already himself made studies, which aspects were produced greater 100. What experiences have been made here?

Best regards

Hans-Peter Schulze

Using 0.5 mm diameter and 150 mm depth using tubular electrodes in EDM is possible. But to reach the same depth using 0.2 mm diameter, the dielectric has to flow inside and expel the debris generated. Peck drilling (intermittent EDM drilling where the tool moves up to some distance) may be considered but machining time will be high in that case.