Notes For Designing - Denso SMT7 Instruction Manual

Chapter 2 Engineering Design of Servo Mechanism
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
[ 1 ] Sliding resistance of ball screw
Screw shaft
1) Friction torque by external load
Fa l

T
P  
2
T :
p
Fa: Shaft direction load
Fa = F +
F:
W:

:
l: Lead (m)

: Effectiveness (0.9)...Ball screw
(1.0)...LM guide
2) Friction torque by pre-load
 
T k
D
T : Friction torque by pre-load
D
Fao: Pre-load (5% of Ca)
l:
k:
Ca: Basic load rating
Nut
Fig. 2-8 Sliding resistance of ball screw


Friction torque by external load

W
External load
Workpiece weight + Table weight
Friction coefficient of slide surface

Fao l

2
Lead
Internal friction coefficient of pre-load nut
motor rated torque (T )
×
F (External load)
Workpiece
weight
+
Table weight
Gear B
20
Gear A Motor
(Nm)
(N)
(N)
(N)
(0.003 - 0.004)
(Nm)
(N)
(N)
(0.1 - 0.3)
(N)