OCTOBER 2005 GENERAL INFORMATION 91
SIEMENS
MAINTENANCE MANUAL
5.6.4 VMC OPTIONS
There are options that can be added to a standard VMC to help manage the thermal
expansion problems.
Probe
A probe in the spindle can be used as a part of the program to discover what
adjustments are required to compensate for thermal expansion. The probe can be used
to pick up the new home position at the beginning of each program, or even at various
times within the program. A probe can quantify the rate of expansion in the Z axis and a
change can then be made to the tool table. The probe can also track the Y axis and X
axis growth and, by using a macro, the fixture offsets can be altered without operator
intervention. Because the amount of expansion differs depending on where the fixture
is located on the table, each fixture should be relocated with the probe. A consideration
when using a probe is that if a chip is in the spindle or on the probe's holder the probe
will indicate an incorrect position.
Coolant ThruSpindle
FADAL's Coolant ThruSpindle option is designed to work in conjunction with specific
tooling (with a hole in the center) to allow coolant to be pumped deep into the part,
where normally coolant does not reach. This significantly improves the rate at which
heat is removed from the area of the cut, reducing the expansion of the part material. In
addition, there is less heat to be transferred through the tool to the spindle and the
head, so expansion of the spindle and the head is also significantly reduced, improving
Z axis positioning and accuracy.
Auto-Aim Servo Coolant
Auto-Aim Servo Coolant is an automatic positioning coolant nozzle system. A closed
loop servo motor automates the coolant stream. Servo Coolant memorizes where
coolant is aimed on each tool adjusting the nozzle position automatically while the
machine is running. The system consists of a nozzle assembly with closed loop servo
motor, a control unit, a remote adjustment knob, cabling, and mounting hardware. The
nozzle assembly is fastened to the machine’s head, oriented so the coolant stream is
aligned to the spindle centerline. Servo Coolant runs off the machines coolant pump.
The nozzle position is set, or taught, for each tool by turning the adjustment knob to
precisely aim the coolant stream. This is done once for each tool in the machine. From
that point on, coolant adjustment is automatic. There are no M-codes to write into your
program, and adjustments can be made and rememorized at any time during the
machining cycle.
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