Hi again:
My comments on people getting experience with running an EDM is Not
directed at any one person. It's just that this art form is so different from
what most people have experienced in machine shops. Go play with one and many
of these mysteries will become clearer.
> Or is there a better material to make the electrode from?
You'll be rich when you figure that out. Find a way to 3-D print an electrode
and you'll set the world on fire. Or 3-D print the heat-treated steel mold
cavity directly!
Many writers (not me because I don't know) state that electrode wear occurs
at the initiation of the spark and that the wear is due to heat at the
electrode surface that isn't conducted away fast enough. For those who haven't
seen it, that is likely why finish electrodes/ burns have such high wear rates.
They endure so very many more sparks than a roughing burn which has sparks of
higher power but longer duration so there are far less of them.
Question:
Does anybody know the typical frequency or pulses per second for finishing
burns? I think it's on the order of 3-5kHz but will look into it of someone
doesn't already know. 40kHz servo response is very responsive but not
necessary if the spark frequency is less than that.
Pete Gruendeman
--------------------------------------------
On Wed, 3/2/16, Gene Heskett <[email protected]> wrote:
Subject: Re: [Emc-developers] EDM gap control (Control parameters)
To: [email protected]
Date: Wednesday, March 2, 2016, 11:38 PM
On Wednesday 02 March
2016 23:53:36 TJoseph Powderly wrote:
> sorry Pete
> I
disagree, any time spent in the wrong position is time spent
making
> bad discharges
> which can damage surface by overheating
> or
> spend time
throwing snowballs that fall short of hitting the target
> imo, update postion as fast as possible
> the average velocity ( a RESULT) will be
low
> but the process will be more
stabile and the surface will not be hard
> and crusty
> abd the
time will be lower
> oops power fail in
ChiangMai
> ttyl8r
>
tomp
One thing I have
always felt needed to be asked, but don't recall seeing
it discussed, is when doing a sinker edm to
imprint a carbon mold like
I've seen
pix of, like engraving a relieved signature, is there an
optimum current per square, either in cm2 or
in2 to design the process
to so it
functions best?
And in
terms of wear on the shaped carbon electrode, is there a
best
current per square in terms of the
metal removed vs the carbon wasted
that
will prolong the electrode life vs metal removed? I've
seen other
processes where optimizing one
is not optimizing the other.
Or is there a better material to make the
electrode from?
> On
03/02/2016 10:05 PM, Pete_Gruendeman wrote:
> > Hi Nicklas:
>
> Correct that looping once per millisecond is
definitely fast
> >
enough. On my machine, 40,000 encoder counts =
1 inch. Spark
> > lengths, even for
finishing operations are 0.001" or longer, or 40
> > encoder counts to go from first spark
to the electrode making
> > physical
contact and that's in 1/25th of a second. That's
not a
> > problem if the machine is
moving at 2- 4 inches per minute. At 4
> > IPM, coming to a stop in 0.001 inches
requires an acceleration of
> >
-0.01852 feet per second squared or -0.00058 g's of
acceleration.
> > No problem.
> >
> > The
other axes would be the same in that gap voltage/current
> > measurement at 1,000 times per second
is plenty fast enough. In
> > fact,
the program I wrote upon detection of gap voltage too low
> > waits on location for 10 milliseconds
and then checks again as often
> > the
situation of the electrode being too close clears itself in
that
> > much time. I didn't
differentiate between gap voltage being too low
> > and it being zero (physical
contact). If I did, then the signal to
> > back out should have been given
without any delay.
> >
> > Pete Gruendeman
>
>
> >
--------------------------------------------
> > On Wed, 3/2/16, Nicklas Karlsson
<[email protected]>
> > wrote:
> >
> > Subject: Re:
[Emc-developers] EDM gap control (Control parameters)
> > To:
"Pete_Gruendeman" <[email protected]>,
"EMC developers"
> > <[email protected]>
Date: Wednesday, March 2,
> > 2016,
4:12 AM
> >
>
> > ...
>
> > All of this start, stop, backup
motion
> >
>
> will result in an average rate of travel
that is on the
> > order
of inches per hour. It's not fast. Though the
> > positioning rate for
forward and reverse motion can be
>
> inches per minute.
>
>
> > > ...
> >
>
> Then it is so slow as at
> > maximum inches per
minute there is no point with
>
> position/velocity loop faster than once
each millisecond?
> >
> > For Z-axis there would
be no
> > problem with
40kHz servo loop if needed.
> >
> > Regards Nicklas
Karlsson
> >
> >
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Cheers, Gene
Heskett
--
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(Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>
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