Yamaha YK120X, YK180X owner manual Example of moment of inertia calculation

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/cm3.

R-axis

2cm

4cm

6cm

Stay 2cm

2cm

1cm

10cm

1cm

Chuck

Workpiece

4cm

2cm

Fig. 3-19

1) Moment of inertia of the stay

From Fig. 3-20, the weight of the

stay (Ws) is given as follows: Center line

Ws = ρabc = 0.0078 ⋅ 12 ⋅ 2 ⋅ 2

= 0.37 (kgf)

2cm

2cm

R-axis

5cm 12cm

Fig. 3-20

The moment of inertia of the stay (Js) is then calculated from Eq. 3-7.

	0.37 ⋅ (122+22)		+	0.37 ⋅ 52	2
Js =					= 0.014 (kgfcmsec	)
	12	⋅ 980		980

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