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CNC Thread Mill Programming |
Compensating the Program Feed Rate For the
Centerline of the Tool
This third and most important element is why 80% of
canned cycles do not work. A helical tool path takes an enormous amount
of data processing capacity for even the latest microprocessor hardware.
Many controllers that employ automatic feed and tool diameter compensation
features bypass these formulas when a true helical move is programmed.
For this reason, Greenfield recommends programming controlled
feed rates within the program for the centerline of the spindle (or tool).
Using this method assures absolute feed control of the tool through the
entire thread milling operation.
Referring to the drawing below, a tool representing
70% of a 1/2" major thread diameter to be milled will have a centerline
tool path that is 30% of the thread produced. Therefore the programmed
feed rate for the centerline must be 30% of the intended IPM to be achieved
for the periphery of the mill.
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