Fw: Off topic: Very small holes in steel

From: Monica & Glenn Whiteside (SiderWhite@worldnet.att.net)
Date: Thu Feb 04 1999 - 04:47:58 EET

>There are a number of processes to try, besides using lasers (although
>are a number of laser job shops out there), that will produce high quality
>and accurate hole diameters in the 0.005 - 0.020 inch range for 0.25 inch
>thick tool steel. Price-wise and thruput-wise they might be better also.
>I've summarized some of them below:
>1) Electrostream Drilling: This process uses a charged, high-velocity
>of electrolyte which will electro-chemically drill holes as small as 0.005
>inches in diameter. The largest diameter that can be produced by this
>process is 0.035 inch. There are two different ES-drilling techniques,
>penetration drilling and dwell drilling. Penetration drilling is what you
>would want because it can be used to drill through thicknesses up to 0.750
>inch. Dwell drilling can only handle up to 0.200 inch thick material.
>process was developed by the General Electric Aircraft Engine Group in
>Cincinnati, Ohio for drilling thousands of small cooling holes in nickel
>cobalt superalloys at high incident angles. The advantage of this process
>is that it does not alter the material properties around the holes and
>typical hole finishes range from 10-63 microinches, however the material
>drilled does have to be electrically conductive. With care, holes can be
>drilled at angles as shallow as 15 degrees from the surface and hole
>diameter tolerances can be held to +/- 0.001 inch and taper can be
>controlled to 0.003 in./in.
>Amchem Company, Inc. in Woburn, MA is an ES-machine manufacturer if you
>more information.
>2) Electrical Discharge Machining (EDM): This process is also well suited
>for drilling many small holes of one or multiple diameters. This process
>can achieve accuracies of anywhere from +/- 0.001-0.005 inch to +/- 0.0003
>if special care is taken. I've seen an example where a hole with a
>of 0.012 inch was drilled through a ball bearing. Precision injector
>holes in the automotive industry are drilled this way with a multiaxis CNC
>3) Electron Beam Machining (EBM): This process uses a focused beam of
>high-velocity electrons to perform high-speed drilling and cutting (and
>welding also). EBM will drill materials up to 0.394 inches thick at
>perforation rates that far exceed all other manufacturing processes!! The
>hole diameters that can be drilled range from 0.004 - 0.055 inches with
>typical tolerances of +/- 0.001 inch.
>4) "Needle" Plasma Arc Systems: These systems are used for fine detail
>and can also drill small holes but I'm not sure of the minimum diameter
>possible. Might be worth checking out.
>5) Ultrasonic Machining (USM): This process is a mechanical material
>process used to erode holes and cavities in hard or brittle materials by
>using shaped tools, high-frequency mechanical motion, and an abrasive
>slurry. Because the process is non-chemical and non-thermal, material
>properties are not altered. When performing drilling operations, USM can
>produce holes as small as 0.003 inch in diameter with tolerances of +/-
>0.001 inch or better. Hole depths up to 2 inches are usually no problem
>with optimum flushing techniques holes as deep as 6 inches are possible.
>and finally....
>6) Laser Processing (LP): Laser drilling, also known as laser percussion
>hole drilling, is accomplished by placing the workpiece at or near the
>point of the laser beam. A short pulse from the laser causes a small
>of the illuminated workpiece material to both partially melt and partially
>vaporize. The explosive escape of the vaporizing material causes most of
>the volume of molten material to be removed as a spray of droplets. Round
>holes with diameters of 0.005 - 0.050 inches can be produced at up to
>of 1 inch (depending on material). The diametral repeatability of
>percussion drilled holes is typically +/- 0.001 inches.
>Hope this helps and gives you a number of options to try...
>Glenn Whiteside
>I'm working with a company that wants to produce very small holes in steel.
>What would you use to produce 5 to 20 HGA diameter holes in 0.25 inch (6.5
>mm) thick tool steel. What is 5 to 20 HGA you ask? Well, to most
>Americans, it's 0.005 to 0.020 inch, .... and to the rest of the world,
>it's 0.125 to 0.5 mm. That's small, but I am under the impression that
>lasers are available that can produce holes that small?
>Terry Wohlers
>Wohlers Associates, Inc.
>OakRidge Business Park
>1511 River Oak Drive
>Fort Collins, Colorado 80525 USA
>Fax 970-225-2027
>P.S. I found the GA discussion creative and humorous! Thanks for
>lightening the day.
>For more information about the rp-ml, see http://ltk.hut.fi/rp-ml/

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