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3-27
CHAPTER 3 Installation
7-3 Example of moment of inertia calculation
Let's discuss an example in which the chuck and workpiece are at a position
offset by 10cm from the R-axis by a stay, as shown in Fig. 3-19.
The moment of inertia is calculated with the following three factors, assuming
that the load material is steel and its density ρ is 0.0078kg/cm
3
.
10cm
2cm
2cm
R-axis
1cm
1cm
2cm
2cm
4cm
6cm
4cm
Stay
Chuck
Workpiece
Fig. 3-19
1) Moment of inertia of the stay
From Fig. 3-20, the weight of the
stay (Ws) is given as follows:
Ws = ρabc = 0.0078 × 12 × 2 × 2
= 0.37 (kgf)
The moment of inertia of the stay (Js) is then calculated from Eq. 3-7.
Js =
0.37 × (12
2
+2
2
)
+
0.37 × 5
2
= 0.014 (kgfcmsec
2
)
12 × 980 980
Fig. 3-20
12cm
2cm
2cm
Center line
5cm
R-axis