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The Xermac CNC control includes a sophisticated
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motion control system. It is possible to compensate for
the motion error. However, if the problem relates to the
leveling and adjustment to the leveling bolts, the machine
Q: My Xermac X-80 machine has developed a bow
in the Y-axis travel. When we move outward from
placed on the table. Before implementing a compensa-
home, the head moves up at the center, and drops
tion routine, the machine should be re-leveled following
down dramatically at the end. Is there any way to will distort to varying degrees as different workpieces are
the procedure in your machine tool user’s manual.
correct this?
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The Xermac CNC control uses a motion control subsys-
tem manufactured by Delta Tau Data Systems – see
A: The short answer is maybe. It depends where the
Figure 2. The controller, known as PMAC (Programma-
bow originates. If the bow is a result of mechanical wear
ble Multi-Axis Controller), is capable of both simple ball
to the linear bearings, they need to be replaced – end
screw compensation, and complex muti-axis cross-axis
of story. However, there are two other possibilities.
compensation. This is sometimes called volumetric
One possibility relates to the fact that the X-80 frame is
compensation. It allows the position of one axis to be
a weldment – see Figure 1. During construction, the
compensated not only by the errors inherent in that axis,
frame is stress relieved. This is an important step.
If not done, or not done correctly, over time the thermal
stresses will resolve themselves and the frame will distort The PMAC allows compensation to be applied by using
a series of tables. For each table, there is a source motor
– potentially causing the type of motion problem that but also by the position of other axes.
and a target motor. For simple ball screw compensation,
you are describing. However, considering that your frame
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these are the same. In the PMAC’s world, the idea of a
was fabricated over 25-years ago, whatever distortion
motor and that of an axis are two completely different
that would have occurred would have happened within
things – as it should be. The PMAC allows the Xermac
the fi rst few years. If this is a new development, it is likely
that there is another cause.
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Figure 1
Xermac X-80
The second possibility relates to the fl oor and leveling
pads. There are a series of large bolts that are in a fl ange
along the bottom of the machine. If the fl oor has shifted,
or if the machine has been moved, it is possible that the
frame may have become distorted due to the leveling
pads being misadjusted, or not bearing equal load. This
situation can be greatly exaggerated if a heavy workpiece 888-665-1118 MMKMATSUMOTO.COM
CUSTOM ROTARY TABLES
is placed on the table.
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EDM Today, Fall 2023 Issue