HEIDENHAIN CNC Pilot 4290 - Manual (Page 159)

HEIDENHAIN CNC PILOT 4290 147
Deep-hole drilling G74
G74 is used for axial and radial bore holes in several stages using
driven or stationary tools.
”1st drilling depth P” is used for the first pass. The CNC PILOT then
automatically reduces the drilling depth with each subsequent pass by
the ”reducing value I”, however, without falling below the ”minimum
hole depth J.” After each pass, the tool is retracted either by ”return
distance B” or to the starting point of the hole.
The cycle is used for:
■ Individual bore hole without contour description
■ Bore holes with contour definition (individual bore hole or hole
pattern) in the following program sections:
■ FRONT
■ REAR SIDE
■ SURFACE
The type of drill determines when a feed rate reduction begins:
■ Indexable inserts and twist drills with 180° drilling angle:
Reduction at end of hole – 2 * safety clearance
■ Other drills:
Drill end – length of first cut – safety clearance
(length of first cut=drill tip; safety clearance: see machining
parameter 9 ”Drilling” or G47, G147).
Parameters
NS:
Contour block number with geometry of bore hole (G49, G300/
G310-Geo) – no input: Individual bore hole without contour
definition
X, Z: Position, length – end point of axis/radial holes (X diameter value)
P: 1st drilling depth
I: Reduction value – default: 0
B: Retraction distance – default: to starting point of hole
J: Minimum hole depth - default: 1/10 of P
E: Period of dwell (for chip breaking at end of hole) – default: 0
V: Feed rate reduction (50%) – default: 0
■ V=0 or 2: Reduction at start
■ V=1 or 3: Reduction at start and at end
■ V=4: Reduction at end
■ V=5: No reduction
Exception with V=0 and V=1: No reduction when boring when
indexable insert drills and twist drills with 180° drilling angle are
used
D: Retraction speed and infeed within the hole – default: 0
■ D=0: Rapid traverse
■ D=1: Feed rate
K: Retraction plane (radial holes, diameter) – default: to starting
position or to safety clearance
4.9 Dr
illing Cy
cles
Cycle run
1 Bore hole without contour definition
Precondition: Tool is located at the safety distance
from the bore hole (”starting position”).
Bore hole with contour definition
The tool approaches the starting position at rapid
traverse according to ”K”:
■ K not programmed: Approach to clearance height.
■ K programmed: Approach to ”K,” and then to
clearance height.
2 Start drilling bore hole – feed rate reduction
according to ”V.”
3 Drill hole in several passes.
4 Drill through – feed rate reduction according to ”V.”
5 Retract at rapid traverse or feed rate according to
”D.”
6 Position to which tool retracts depends on ”K”:
■ K not programmed: Retract to starting position.
■ K programmed: Retract to position ”K.”
■ Single hole without contour description:
Program +X or Z+ as alternative.
■ Hole with contour description: Do not
program X, Z.
■ Hole pattern: NS refers to the bore hole
contour (and not the definition of the
pattern)).
■ A ”feed rate reduction at end” goes into
effect only at the last drilling stage.