It is difficult to produce the compensation necessary to form accurate parts when using only the tool offset function due to tool nose roundness in taper cutting or circular cutting. The tool nose radius compensation function compensates automatically for the above errors.
R Workpiece
Insufficient depth of cutting
Shape processed without tool nose radius compensation
Tool path without compensation Tool path with compensation
Tool nose
Fig 5.2 (a) Tool path of tool nose radius compensation
NOTE
To use tool nose radius compensation, set bit 7 (NCR) of parameter No. 8136 to 0.
5.2.1 Imaginary Tool Nose
The tool nose at position A in Fig. 5.2.1 (a) does not actually exist.
The imaginary tool nose is required because it is usually more difficult to set the actual tool nose radius center to the start point than the imaginary tool nose.
Also when imaginary tool nose is used, the tool nose radius need not be considered in programming.
The position relationship when the tool is set to the start point is shown in Fig. 5.2.1 (a).
A Start point
Start point When programmed using the tool
nose center
When programmed using the imaginary tool nose
Fig. 5.2.1 (a) Tool nose radius center and imaginary tool nose
CAUTION
In a machine with reference positions, a standard position like the turret center can be placed over the start point. The distance from this standard position to the nose radius center or the imaginary tool nose is set as the tool offset value.
Setting the distance from the standard position to the tool nose radius center as the offset value is the same as placing the tool nose radius center over the start point, while setting the distance from the standard position to the imaginary tool nose is the same as placing the imaginary tool nose over the standard position. To set the offset value, it is usually easier to measure the distance from the standard position to the imaginary tool nose than from the standard position to the tool nose radius center.
OFX (Tool offset in X axis)
OFZ (Tool offset in Z axis)
Setting the distance from the standard position to the tool nose center as the tool offset value
Setting the distance from the standard position to the imaginary tool nose center as the tool offset value
The start position is placed over the tool nose center The start position is placed over the imaginary tool nose
OFX (Tool offset in X axis)
OFZ (Tool offset in Z axis)
Fig. 5.2.1 (b) Tool offset value when the turret center is placed over the start point
Unless tool nose radius compensation is performed, the tool nose center path is the same as the programmed path.
If tool nose radius compensation is used, accurate cutting will be performed.
Tool nose center path
Programmed path Start- up
Start- up
Programmed path Tool nose center path
Fig. 5.2.1 (c) Tool path when programming using the tool nose center
Without tool nose radius compensation, the tool nose radius center path is the same as the programmed path.
With tool nose radius compensation, accurate cutting will be performed.
Imaginary tool nose path
Imaginary tool nose path Start-
up
Start- up
Programmed path Programmed path
Fig. 5.2.1 (d) Tool path when programming using the imaginary tool nose
5.2.2 Direction of Imaginary Tool Nose
The direction of the imaginary tool nose viewed from the tool nose center is determined by the direction of the tool during cutting, so it must be set in advance as well as offset values.
The direction of the imaginary tool nose can be selected from the eight specifications shown in the Fig. 5.2.2 (a) below together with their corresponding codes. This Fig 5.2.2 (a) illustrates the relation between the tool and the start point. The following apply when the tool geometry offset and tool wear offset option are selected.
Imaginary tool nose number 1 Imaginary tool nose number 2
Imaginary tool nose number 3
Imaginary tool nose number 4
Imaginary tool nose number 5 Imaginary tool nose number 6
Imaginary tool nose number 7 Imaginary tool nose number 8 X
Z G18 Y
X G17 Z
Y G19
Fig. 5.2.2 (a) Direction of imaginary tool nose
Imaginary tool nose numbers 0 and 9 are used when the tool nose center coincides with the start point. Set imaginary tool nose number to address OFT for each offset number.
Bit 7 (WNP) of parameter No. 5002 is used to determine whether the tool geometry offset number or the tool wear offset number specifies the direction of the virtual tool nose for tool nose radius compensation.
Imaginary tool nose number 0 or 9
5.2.3 Offset Number and Offset Value
Explanation
- Offset number and offset value
Tool nose radius compensation value (Tool nose radius value)
When tool geometry and wear compensation is disabled (bit 6 (NGW) of parameter No. 8136 is set to 1), the following numbers and values are used:
Table 5.2.3 (a) Offset number and offset value (example) Offset
number Up to 999 sets
OFX (Offset value on X
axis)
OFZ (Offset value on Z axis)
OFR (Tool nose radius compensa-
tion value)
OFT (Direction of imaginary tool
nose)
OFY (Offset value on Y axis)
001 002 003 004 005 :
0.040 0.060 0.050
: : :
0.020 0.030 0.015
: : :
0.200 0.250 0.120
: : :
1 2 6 : : :
0.030 0.040 0.025
: : :
When tool geometry and wear compensation is enabled (bit 6 (NGW) of parameter No. 8136 is set to 0), the following numbers and values are used:
Table 5.2.3 (b) Tool geometry offset (example) Geometry
offset number
OFGX (X-axis geometry
offset amount)
OFGZ (Z-axis geometry
offset amount)
OFGR (Tool nose radius geometry offset value)
OFT (Imaginary tool nose direction)
OFGY (Y-axis geometry
offset amount) G001
G002 G003 G004 G005
:
10.040 20.060
0 : : :
50.020 30.030
0 : : :
0 0 0.200
: : :
1 2 6 : : :
70.020 90.030
0 : : : Table 5.2.3 (c) Tool geometry offset (example)
Wear offset number
OFWX (X-axis wear offset
amount)
OFWZ (Z-axis wear offset amount)
OFWR (Tool nose radius wear offset value)
OFT (Imaginary tool nose direction)
OFWY (Y-axis wear offset amount) W001
W002 W003 W004 W005
0.040 0.060
0 : :
0.020 0.030
0 : :
0 0 0.200
: :
1 2 6 : :
0.010 0.020
0 : :
- Tool nose radius compensation
When tool geometry and wear compensation is enabled (bit 6 (NGW) of parameter No. 8136 is set to 0), the total of the geometry and wear offset amounts is used as the tool nose radius compensation value during execution.
OFR=OFGR+OFWR
- Imaginary tool nose direction
The imaginary tool nose direction is common to geometry and wear offsets.
- Command of offset value
A offset number is specified with the same T code as that used for tool offset.
NOTE
When the geometry offset number is made common to the tool selection by the parameter LGN (No.5002#1) setting and a T code for which the geometry offset and wear offset number differ from each other is
designated, the imaginary tool nose direction specified by the geometry offset number is valid.
Example) T0102
OFR=OFGR01+OFWR02
OFT=OFT01
By setting parameter WNP (No. 5002#7) appropriately, the imaginary tool nose direction specified with the wear offset number can be made valid.
- Setting range of offset value
The range of values that can be set as a compensation value is either of the following, depending on the bits 1 (OFC) and 0 (OFA) of parameter No. 5042).
Valid compensation range (metric input)
OFC OFA Range
0 1 ±9999.99mm 0 0 ±9999.999mm 1 0 ±9999.9999mm Valid compensation range (inch input)
OFC OFA Range
0 1 ±999.999inch 0 0 ±999.9999inch 1 0 ±999.99999inch
The offset value corresponding to the offset number 0 is always 0.
No offset value can be set to offset number 0.
5.2.4 Workpiece Position and Move Command
In tool nose radius compensation, the position of the workpiece with respect to the tool must be specified.
G code Workpiece
position Tool path
G40 (Cancel) Moving along the programmed path
G41 Right side Moving on the left side the programmed path G42 Left side Moving on the right side the programmed path The tool is offset to the opposite side of the workpiece.
Workpiece
G41
G42 X axis
Z axis
G40
G40 The imaginary tool nose is on the
programmed path.
Imaginary tool nose number 1 to 8
Imaginary tool nose number 0
Fig. 5.2.4 (a) Workpiece position