an on-demand state. "If we only
need 10% coolant fow, then we're
running the motor at 10% of its
capacity." The previous norm is
to have synchronous motors that
are either running or not, so if
you needed 10% coolant fow, the
motor would still run at 100%.
He says they're looking at spindle
speeds in relation to axis travel.
That is, say there is a long traverse
before cutting commences and
the spindle needs to be running
at 10,000 rpm for machining.
Typically today, the spindle is run
up to that speed as the axis motors
are bringing the spindle to where
it needs to be for machining. So
what they're doing at DMG MORI
is calculating the time for both
the time it takes to get the spindle
up to speed and the time it takes
for the spindle to be positioned
for the cut, and then adjusting
accordingly: "If the spindle gets to
maximum rpm half way through
the rapid movement, then we slow
the spindle down to save energy
without afecting the cycle time in
any way." That is, the spindle isn't
running at 10,000 rpm when it is
still on its way to getting to where
it needs to be.
Similarly, when it comes to face
milling, Hansel points out that
when the face mill clears the
workpiece, the machining is over.
"But," he points out, "ordinarily,
the feedrate is constant until the
entire face mill not only clears the
surface, but moves a distance past
the workpiece. If we can calculate
the edge of the workpiece, as soon
as the face mill is halfway over
the edge and it is done cutting,
we can go to a rapid feed and pick
up a couple of tenths of a second
for every pass. It adds up over
time."
"Anything we can do to shorten
cycle time," Hansel says, makes
the machine more sustainable."
And that's a good thing for
everyone.
AD&P; > July 2014 > FEATURE > How to Make Machine Tools More Sustainable > Gary S. Vasilash
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