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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