Machining micro holes

[HilaryE]

Hi,

I need to machine through holes, 0.25mm diameter, approx. 2.5mm deep
I need to machine approx. 4000 of such holes. Those holes are located in a single row array. The pitch c/c is 0.4mm.
These holes will be drilled in a die. There will be approx. 30 dies manufactured a year.

I consider drilling those holes in brass (CZ121), mild steel (of average characteristic) and 316 stainless steel

1. My options for brass is micro-milling (least expensive, possible micro hole surface finish problem), EDM hard-tool (probably dearest option, high finish quality),

2. My options for mild and stainless steel - EDM hard-tool.

I also considered micro laser machining, however, I have been informed by a company which provides micro laser machining, that they cannot penetrate a material deeper than 1mm.

I would be very obliged for any suggestions.

Thank you.

 

[3DDave]

These holes are a little larger, but it's close

http://www.mmsonline.com/videos/video-drilling-0020-inch-holes-in-stainless-steel-aerospace-part

They refer to using a

http://cameronmicrodrillpress.com/

CNC drill, and their pages indicate holes down to .002 inches (0.05 mm) diameter.

Something to note is that drilling such small holes means having very little runout in the spindle to avoid fatigue failures and drill breakage.

Laser has a problem because it vaporizes the material, and the vapor is what pushes the vapor out. If the hole is too deep the vapor cools and condenses, refilling the hole. In addition the beam is typically tapered, so the hole will either be conical or the edge of the hole will eclipse too much energy to get the material at the hole bottom heated.

Have you considered brazing pieces of hypodermic tubing together? You could saw to length and then polish to get clean ends.