Siemens SINUMERIK 840D Maintenance Manual page 90

FADAL MACHINING CENTERS
of carrying away the heat of the cut and minimizing the effects of thermal expansion
resulting from that heat.
Yet another practice that deserves mentioning is machining parts at temperatures
significantly different from those at which the parts are inspected. If the inherent
expansion of the part material from the heat of the machining process is outside
tolerance once the part has cooled to inspection temperatures, the problem can only be
resolved by correcting for the heat generated during machining so as to keep the part
material closer to inspection temperatures while the part is being machined. Along
those same lines, it is important to use a gauge at approximately the same temperature
as the temperature at which the gauge was calibrated.
Finally, the use of blanks for which the outside dimensions have been established prior
to cutting is another practice which aggravates the effects of thermal expansion. Since
the blank is going to expand locally from the heat of cutting, the actual distance from
edge to feature may change.
84 GENERAL INFORMATION MAN-0126_ R1