I've got this book on the shelf, tons of information within: 'Build An
EDM -- Electrical Discharge Machining - Removing Metal By Spark
Erosion' by Robert Langlois, 1997, Village Press, The Home Shop
Machinist, ISBN 0-941653-52-8.
Contents
Part 1: The Introduction and Box Construction..............4-11
Part 2: The Spark Power Supply..............12-23
Part 3: The Stepper Motor Logic and Drive Board .............. 24-33
Part 4: Installing Stepper Motor Board and Stepper Motor .....34-39
Part 5: The Head and EDM Operation..............40-49
Part 6: Other Odds and Ends..............50-54
Spark Eroding a Broken Stud..............55-56
Excerpts:
"The purpose of an EDM is to cut metal by making little sparks. Its
advantages are that it will cut holes in metals that cannot be
machined by common tools. It will also cut unusually shaped holes in
all metals. But it will not compete with a drill to cut simple round
holdes in normal machinable metals because it is slow, slow, slow.
"Figure 1.2 shows the main components of the EDM. The power supply and
stepper motor drive are based on common, inexpensive, surplus
electronic components. The mechanical part, the head, is simple and
portable yet precise. It is built up from brass sheet and telescoping
brass tubing. The dielectric fluid is a safe, nonflammable mix of
water, antifreeze and oil. The pump is an aquarium pump and the sump
is a plastic box.
"This EDM project would not have come about had it not been for Chris
Ball who handed me an old ('76) Model Engineer article by C.R.
Amsbury. He asked, "I can't locate the electronic parts for this. Can
you redesign it?" "Hey, no problem," I answered. Well, there's a moral
here about being too confident, but six months later one was operating.
"It did not take long to design and breadboard both the electronics
and mechanical parts. In fact, I demonstrated the EDM at the next club
meeting one month later. What did take a bit of time was the
management of the tool. EDM is an art. There are so many variables in
the combined electronics, mechanics and fluids that industrial EDM
operators develop an intuitive approach to their job.
"In this six-part series, I will share with you my discoveries and
take you through the construction and operation of your own EDM.
". . . If you follow Parts 1 to 5 you will have a machine that will
be adequate to remove broken drills and taps more than a half-inch in
diameter and over an inch long. It will also erode small diameter
holes more than an inch deep. If you include Part 6 in your machine it
will also handle more demanding jobs, such as light milling.
"A careful search for surplus electronics components should keep the
basic cost below $100. The odds and ends to be built in Part 6 of this
series are an option. Most machinists will very likely find all of the
metal for this project in their scrap box and I give no cost estimate.
If you have not done much with electronics in the past, expect to
spend about 60 hours building the circuit. . . .
"This EDM project is intended for very limited use in a home workshop.
. . . I have built and operated an EDM. It has proved simple and safe
to use providing common sense and standard electrical and engineering
practices are observed. . . ."
.............................................................................................................
That gives a flavor of what the book (a compilation of several
articles published in The Home Shop Machinist magazine) is about.
I have a tabletop CNC mill, and the Vector CAD/CAM software
(www.imsrv.com) I use is EDM proficient. Here's a blurb about the
software:
> Vector is a full featured, 3D Cad drawing program with an integrated
Cam capability. The basic version includes CNC Milling, CNC Turning, 2
and 4 axis wire EDM, CNC Engraving, Routing, Laser, Plasma, Water Jet,
and other table based, 2 and 3 axis CNC machines. Optional features
include a 3D, "What You See Is What You Get" (WYSIWYG) rotary 4th
axis, an external programmable DDE, and our new 3D Surface modeling
and machining. IMService also provides additional programs to
supplement Vector's capabilities with V-tip cutter carving,
conversational Lathe Quick Code, and Raster to Vector software programs. <
Not only am I hoping the information in this post might be helpful to
some of you here on the board, I'm also wondering if I'm not pretty
well setup to get an EDM system operating in my shop. I'm going to
have to greatly increase my knowledge about EDM before I tackle
getting 'er done, though. I'm eager to discover what this EDM thread
here on the list will lead to.
-Brian
Brian Chapman
Evansdale, Iowa
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