Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 450)

Programming Feedrates
Chapter 18
18-2
Feedrates for linear and circular interpolation are “vector” feedrates. That
is, all axes move simultaneously at independent feedrates so that the rate
along the effective path is equal to the programmed feedrate (see
Figure 18.1).
Figure 18.1
Feedrate Tangent To Tool Path
X X
Y Y
Linear interpolation Circular interpolation
programmed
feedrate
Y axis
feedrate
start
point
X axis
feedrate
end
point
programmed
feedrate
end point
Y axis
feedrate
start
point
X axis
feedrate
For example, if a feedrate is programmed as F100.0 millimeters per minute
and a linear move is made from X0, Y0 to X10., Y10. the feedrate along
that 45 degree angular path would be 100.0 mmpm. The actual feed rate of
each axis will be approximately 70.7 millimeters per minute.
When the cutting tool is offset from a programmed path, (as in the case of
cutter compensation) the programmed feedrate is applied to the center of
the tool radius for all linear and outside arc paths. This discussion deals
with the speed at which the outside surface of the tool passes across the
workpiece surface disregarding tool rotation speed.
For linear paths, the result is not significant because the speed of the
outside surface of the tool relative to the part surface remains the same as
the programmed feedrate.
For outside arc paths, the resulting speed of the outside surface of the tool
relative to the part surface is less than the programmed feedrate. This
generally causes no problem and so the control does not take corrective
action.
18.1.1
Feedrates Applied During
Cutter Compensation