HEIDENHAIN TNC 426, User Manual

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270 8 Programming: Cycles
8.4 Cy
cles f
o
r milling poc
k
e
ts, st
uds and slots
SLOT MILLING (Cycle 3)
Roughing process
1 The TNC moves the tool inward by the milling allowance (half the
difference between the slot width and the tool diameter). From
there it plunge-cuts into the workpiece and mills in the longitudinal
direction of the slot.
2 After downfeed at the end of the slot, milling is performed in the
opposite direction. This process is repeated until the programmed
milling depth is reached.
Finishing process
3 The TNC advances the tool at the slot bottom on a tangential arc
to the outside contour. The tool subsequently climb mills the
contour (with M3).
4 At the end of the cycle, the tool is retracted in rapid traverse FMAX
to set-up clearance. If the number of infeeds was odd, the tool
returns to the starting position at the level of the set-up clearance.
Before programming, note the following:
This cycle requires a center-cut end mill (ISO 1641), or pilot
drilling at the starting point.
Pre-position to the center of the slot and offset by the tool
radius into the slot with radius compensation R0.
The cutter diameter must be not be larger than the slot
width and not smaller than half the slot width.
Program a positioning block for the starting point in the
tool axis (set-up clearance above the workpiece surface).
The algebraic sign for the cycle parameter DEPTH
determines the working direction. If you program DEPTH
= 0, the cycle will not be executed.