Siemens sinumerik 840D sl Operating Manual page 344

Programming technology functions (cycles)
8.4 Milling
Parameters Description
Insertion Various insertion modes can be selected – (only for plane-by-plane machining method
and for ∇, ∇∇∇ and ∇∇∇ edge):
Predrilled (only for G code)

Perpendicular: Insert vertically at center of pocket

The tool executes the calculated depth infeed vertically at the center of the pocket.
Feedrate: Infeed rate as programmed under FZ
Helical: Insert along helical path

The cutter center point traverses along the helical path determined by the radius
and depth per revolution. If the depth for one infeed has been reached, a full circle
motion is executed to eliminate the inclined insertion path.
Feedrate: Machining feedrate
Note: The vertical insertion into pocket center method can be used only if the tool
can cut across center or if the workpiece has been predrilled.
FZ Depth infeed rate
(only for G code)
FZ or FX Depth infeed rate - (only for insertion, predrilled and perpendicular)
(only for (FZ for machining surface, face C/Y or FX for peripheral surface C/Y)
ShopTurn)
EP Maximum pitch of helix - (for helical insertion only)
The helix pitch may be lower due to the geometrical situation.
ER Radius of helix - (only for helical insertion)
The radius must not be larger than the cutter radius, otherwise material will remain.
Also make sure the circular pocket is not violated
Complete machining
Machining 
The circular pocket must be milled from a solid workpiece (e.g. casting).
(only for G code)
Remachining

A small pocket or hole has already been machined in the workpiece, which needs
to be enlarged. Parameters AZ, and ∅1 must be programmed.
FS Chamfer width for chamfering - (for chamfering only)
ZFS or XFS Insertion depth of tool tip (abs or inc) - (for chamfering only)
(ZFS for machining surface, face C/Y or XFS for peripheral surface C/Y)
AZ Depth of premachining - (for remachining only)
(only for G code)
∅1 Diameter of premachining - (for remachining only)
(only for G code)
344
Operating Manual, 07/2010, 6FC5398-8CP40-0BA0
Unit
mm/min
mm/min
mm/tooth
mm/rev
mm
mm
mm
mm
mm
Turning