Siemens SINUMERIK 840D Maintenance Manual page 92

FADAL MACHINING CENTERS
on the table. Because of its large size, the table seems less affected by the heat of
machining. It will expand, but it takes longer to heat or cool the entire table. In addition,
the use of coolant tends to stabilize the temperature of the table at or close to coolant
temperature.
A machining operation using rapid moves and low spindle speeds, with additional
cooling at the part through FADAL's servo coolant subsystem, will generate much more
thermal expansion in the ball screws, and hence the X axis and Y axis, than will be
seen in the Z axis from the spindle or in the part material from the cutting. An operation
using very high RPM spindle speeds with slower interpolated moves would experience
more Z axis expansion, but would experience less expansion in the X axis and Y axis,
and might actually experience less expansion in the part material because the high rate
of chip removal carries much of the heat away from the part.
Each machining operation has a unique combination of factors that apply to predicting
and managing the thermal expansion inherent in machining. Finding the right solution is
a matter of combining various approaches, many of which are outlined in the pages that
follow.
86 GENERAL INFORMATION MAN-0126_ R1