On Mon, 17 Aug 2015 18:23:26 -0700, Larry Jaques
wrote:
On Sun, 16 Aug 2015 14:19:38 -0700, Gunner Asch
wrote:
On Sun, 16 Aug 2015 07:36:19 -0500, Pete Keillor
wrote:
On Sat, 15 Aug 2015 17:59:24 -0700 (PDT), "
wrote:
On Saturday, August 15, 2015 at 6:00:47 PM UTC-4, Pete Keillor wrote:
I'd still need to build the carriage, stepper drive, controls, etc. I
have a Beaglebone Black which could be applied to that job. I can get
a reasonable stepper for $11 from the salvage place in town, plus some
linear bearings and a bellows coupler for not much.
Any known reasons the welder is a bad idea?
Thanks.
There are some DIY edm plans on the internet. You might look at some of them for ideas.
Many years ago, somewhere around 1969 a friend and I kludged up a edm. We used his drill press for the feed by setting the depth nuts and then leaned on the handle to feed the tool a very small amount. As I remember we used a good sized maybe 500 VA transformer and I think a voltage doubler. A light bulb in series with the supply had low resistanece when things were working and a higher resistance when we had the tool shorting to the work. A kludge , but it worked and we could put square holes into tool steel.
We were charging the cap to about 300 volts. So a bunch higher voltage than your welder would supply, but the plans on the internet all use lower voltage.
So in answer to your qoestion , I do not know.
Dan
Thanks all. Lloyd, yeah I'm retired and I think it'd be educational,
plus I already spent an hour or two picking and pecking at it.
Good ideas, Ed. I might combine that with Dan's drill press idea for
a test. I'll try the welder at much lower voltage. If that doesn't
work, then I'll ge further into Lanlois' design using some big caps.
Pete Keillor
You guys may..may wish to simply buy a used EDM machine. Used but
working good machines are simply thrown away all over the US because
they have become "obsolete"
Wire, sinker, spark....Ive tried to find buyers and wound up pushing
them into scrappers trucks with a forklift off the loading docks.
Ive destroyed at least 4 of these in the past 10 yrs..simply because
no one wanted them..and they were ALL in good working shape
http://www.ebay.com/itm/Electro-Arc-...item3cff60b45c
It's a shame they're going to the dump/scrap yard, but at $1k to ship
plus a lot of space to set it up, it's no big wonder. Are smaller
units built? I'll bet tiny EDMs find new homes a lot more easily,
especially with hobbyists like us.
It depends on what sort of EDM is in question. The simplist are spark
eroders..tap busters..all the way up through wire edms.
http://www.polcraft.com/edm2.htm
What is EDM?
EDM stands for Electrical Discharge Machining. The basic concept
of EDM is that you use an electrode to erode a workpiece using
electrical sparks. The electricity flows through the electrode in the
form of a square wave attacking the points of least resistance on the
workpiece similar to how a bolt of lightning would hit a tree before
it hits the ground. This "Zap" happens every time the current is
switched on in the square wave and then the current is switched off to
allow the debree to be flushed away. This process happens over and
over many times a second as the electrode is slowly advanced deeper
and deeper into the cut. The electrode never touches the workpiece
because the actual cutting is being done by the spark gap between the
electrode and the workpiece.
The process takes place submerged in a dielectric fluid such as
deionized water or dielectric oil. This fluid acts like the vacuum in
a light bulb. If you break a light bulb, the fillament which has
current flowing through it becomes oxidized and burns out. The same
would happen if you tried to EDM without any dielectric, the electrode
and workpiece would become oxidized and would not be able to perform
the cut. The Dielectric fluid performs multiple tasks; 1) Providing an
inert atmosphere in which the process can take place. 2) Flushes the
removed material or debree away from the gap. 3) Keeps the gap cool
and the temperature of the whole process stable.
There are three main types of EDM which are different according to
the type of electrode used.
Wire EDM cutting honeycomb stainless steel
Wire EDM in which the electrode is a brass wire that comes off
a spool and is fed through an upper and lower diamond guide and then
discarded after it is used. The wire is controlled by a CNC control
which allows you to program a path for the wire to travel along sort
of like a super precision band saw. The wire can range from .0120 to
..0008 inches in diameter. This form of EDM is the most accurate and is
able to hold size well under .0001 inches.
Sinker EDM
Sinker EDM in which the electrode is a machined shape made of
materials like graphite, copper, or copper-tungsten (to name a few)
and the machine uses this shape to erode the inverse shape in the
workpiece. This process is also very accurate and commonly used to
burn mold cavities where the electrode starts out the shape of the
final molded part and is used to erode a cavity in a mold that is
later used to make thousands or millions of parts.
EDM drill
Small hole EDM drill ("Hole Popper") in which the electrode is
a brass or copper tube ranging from .004 to .250 inches in diameter
that is used to blast holes through the workpiece. This process is
similar to Sinker EDM except that sinkers have very sensitive power
supplies to protect and conserve the electrode and the popper has a
very aggressive power supply to blast through the workpiece very
quickly. This type of EDM compliments the wire EDM by providing the
ability to drill pilot holes through heat treated materials and
carbide so that you can thread the wire through this pilot hole for a
place to start your wire cut.
Polcraft inc. employs all three types of EDM in addition to CNC
and conventional milling and turning to eliminate any out sourcing of
the manufacturing process so you get high quality parts in a timely
fashion.
(there is actually 4 kinds...the lowly tap buster being the first
kind..but its generally covered under EDM drill....
Check the photos...
http://www.mercatech.com/EDM%20Guide...20is%20EDM.htm
Gunner