10 Axis and Spindle Installation 11.92
10.4.5 Distance-coded reference marks
3. Direction of linear scale as compared with the machine system
It should be made clear how the linear scale is applied to the machine system. Whether the
direction is positive or negative is defined in MD 1808*.
• NC MD 1808*, bit 2 = 0 Linear scale same direction as machine system
• NC MD 1808*, bit 2 = 1 Linear scale opposite direction to machine system
4. Determining the offset of (linear) scale and machine system
(Absolute offset)
Structure of the linear scale with coded reference marks:
(a/2
-n)
.
k
Reference mark
X min
1 2 3 4 5 6 7 k
(n-1) . a . k
a . k
(a/2+n)
.
k
a . k a . k a . k
(a/2+1)
.
k (a/2-1)
.
k (a/2+2)
.
k (a/2-2)
.
k (a/2+3)
.
k (a/2-3)
.
k
Measured length on scale
with n = a . k
Using the above example:
10-n
0.02
9.949.969.98 10.04 10.0610.02 10+n 0.02
X min
1 2 3 4 5 6 7 k
Reference mark
20 20 20 20
(n-1) . 20
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