YASKAWA SGM series User Manual page 91

APPLICATIONS OF Σ-SERIES PRODUCTS
3.2.5 Using Electronic Gear cont.
3
80
c) Determine the reference unit to be used.
Reference unit is the minimum unit of posi-
tion data used for moving the load.
(Minimum unit of reference from host con-
troller)
Examples:
0.01 mm, 0.001 mm, 0.1°, 0.01 inch
Reference input of one pulse moves the load
by one reference unit.
Example: When reference unit is 1 μm
If a reference of 50,000 pulses is input, the load moves 50 mm (50,000 x 1 μm).
d) Determine the load travel distance per revolution of load shaft in reference units.
Load travel distance per revolution of load shaft (in reference units)
Example: When ball screw pitch is 5 mm and reference unit is 0.001 mm
5/0.001 = 5,000 (reference units)
Ball Screw
Load shaft
1 revolution
=
Reference unit
e) Determine the electronic gear ratio
If the load shaft makes "n" revolutions when the motor shaft makes "m" revolutions,
the gear ratio of motor shaft and load shaft is n m .
Electronic gear ratio
Travel distance per revolution of load shaft (in reference units)
NOTE Make sure that the electronic gear ratio meets the following condition:
If the electronic gear ratio is outside this range, the Servopack does not work
properly. In this case, modify the load configuration or reference unit.
Load travel distance per revolution of load shaft (in unit of distance)
=
Disc Table
P: Pitch
1 revolution
P
=
Reference unit
 
B
.
A
 
B
=
A
Number of encoder pulses x 4

0.01 ≤ Electronic gear ratio
To move a table in 0.001 mm units
Reference unit: 0.001 mm
Determine the reference unit according to
machine specifications and positioning
accuracy.
Reference unit
Belt & Pulley
Load shaft
Load shaft
D: Pulley diameter
360°
1 revolution
=
× m n

B
≤ 100
A
π D
Reference unit