Rockwell Automation 8520 9/Series CNC Lathe - Manual (Page 623)

Thread Cutting
Chapter 25
25-23
Tool Infeed
This multipass threading routine provides 4 different types of cutting tool
infeed determined by a P-word in the threading block. These different
infeeds are provided to allow operation with different types of cutting tools
and materials. These different infeed types all move the end-point of the
cutting tool when infeeding an amount referenced from the infeed
reference point.
P1 - Constant cutting volume, angular infeed along thread face. A
constant amount of material is removed in each pass (except possibly the
last few passes). The last few passes may reach the minimum infeed
amount set in AMP by the system installer. If the depth of cut is smaller
than the minimum depth of cut set in AMP, it is increased to equal that
minimum depth of cut. Only one edge of the cutting tool removes
material.
P2 - Constant cutting volume, zigzag infeed. With this parameter, the
control alternates the cutting edge of the tool after every pass. The amount
of material that is removed is constant every two passes.
Important: If the user programs one pass, the control halves the
programmed depth and makes two passes. Because of this, the number of
passes programmed must always be even; and the depth of the pass cannot
be too small. If it is too small, the cutting tool may only burnish the part,
instead of cutting it.
To prevent burnishing, the system installer can program in AMP a
minimum depth of cut. If the user then enters a depth of cut smaller than
the minimum depth of cut in AMP, the entered value is disregarded, and
the value in AMP replaces it.
P3 - Constant depth of cut, angular infeed along thread face. This method
is the same as P1, except that the cutting depth is kept constant with each
pass, and there is no minimum infeed applied. Only one edge of the
cutting tool removes material.
P4 - Constant depth of cut, zigzag infeed. This method is the same as P2
except that the cutting depth is kept constant for each pass, and there is no
minimum infeed applied. Each edge of the cutting tool removes material
on alternate passes.