15. Tool Length Compensation
Tool length is a very important concept, when we
program a machining part, we must first specify the
programming center of the part, and then establish
the workpiece programming coordinate system.
And this coordinate system is only a workpiece
coordinate system, zero point is generally on the
workpiece. Since the length of each tool is different,
the length compensation is only related to the Z
coordinate.
16. Example
we want to drill a hole of 50 m depth and tap a hole
of 45 m depth with a drill of 250 m length and a tap
of 350 m length.
First, use a drill to drill a hole with a depth of 50
mm. At this time, the machine tool has set the
workpiece at zero point.
When tapping is replaced, if both tools start
processing from the set zero point, the tap is longer
than the drill and the tap is too long which may
damage tools and workpieces.
17. At this time, if the tool compensation is set, the
length of the tap and the drill are compensated.
Due to the existence of compensation when the tap is
called, the zero Z coordinate has automatically
compensated the length of the tap to Z+ (or Z), to
ensure the correct processing zero.
Tool length offset is carried out by instructions G43,
G44, and G49, which can compensate for the change
of tool length at any time without changing the
program.
20. Tool nose radius compensation (TNRC)
Tool nose radius compensation (TNRC) is a CNC
programming feature that ensures accurate machining
of complex contours by accounting for the rounded tip
of the cutting tool, also known as the tool nose radius.
Without TNRC, tapers, radii, and chamfers would be
inaccurate due to the tool's nose radius leaving excess
material or removing too much.
TNRC recalculates the tool path so the nose radius,
rather than the theoretical tool tip, follows the
programmed contour.
21. What is Tool Nose Radius Compensation ?
When we set tool offsets for a tool, we typically make
a cut along the face, one on the diameter, and set the
offsets based on this. We actually set the offsets for
the point indicated by the red dot in the picture, the
Theoretical Tool Tip (TTT).
When we program the tool to move to a certain
point, its TTT is the one that actually moves to the
commanded point. In the picture below, when we
move the tool to point A, the TTT is at point A while
the radius is in air, not touching the part.
23. TURNING /FACING
Plain diameter and face You get the correct
dimensions, since the tool radius and the TTT
coincide on the face and diameter.
26. How is TNRC implemented ?
You must
do 3 things
1. Add TNRC
commands
(G41/G42/G40
) in the
program.
2. Enter the nose
radius of the tool
on the machine,
in the tool
offsets page.
3. Enter the tool
orientation (see
picture below) on
the machine, in the
tool offsets page.
