Chapter 2 Engineering Design of Servo Mechanism
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2.1.4 Notes for Designing
The sliding resistance of the mechanism controlled by the SMT7 should be as follows.
Sliding resistance (torque conversion) 0.2
× motor rated torque (T )
[ 1 ] Sliding resistance of ball screw
Fig. 2-8 Sliding resistance of ball screw
1) Friction torque by external load
T
Fa l
P
2
T
p
: Friction torque by external load (Nm)
Fa: Shaft direction load (N)
Fa = F +
W
F: External load (N)
W: Workpiece weight + Table weight (N)
: Friction coefficient of slide surface (0.003 - 0.004)
l: Lead (m)
: Effectiveness (0.9)…Ball screw
(1.0)…LM guide
2) Friction torque by pre-load
Tk
Fao l
D
2
T
D
: Friction torque by pre-load (Nm)
Fao: Pre-load (5% of Ca) (N)
l: Lead (N)
k: Internal friction coefficient of pre-load nut (0.1 - 0.3)
Ca: Basic load rating (N)
F (External load)
Wor
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