Specifications

11– 11
11
11.SELECTION
11-9 Selection example
(1) Selection of control parameters
1) Setting of electronic gear (command pulse multiplication numerator, denominator)
There is the following relationship between the multiplication setting and travel per pulse
∆R.
∆R=
(ball screw lead)
8192 x (gear ratio)
x
CMX
CDV
()
When the above machining specifications are substituted in the above equation:
CMX
CDV
= 0.005 •
8192 • 8/5
16
=
512
125
Acceptable as CMX/CDV is within 1/50 to 20.
2) Input pulse train frequency for rapid feed fo
fO =
V o
60 • ∆R
30000
60 • 0.005
= =100000 [pps]
Acceptable as fo is not more than 200kpps.
(2) Servo motor speed
NO =
Vo
Pb
• n = 3000[r/min]
(3) Acceleration/deceleration time constant
Tpsa = Tpsd = to -
R
V
o /60
- ts = 0.05 [s]
*ts: settling time. (Here, this is assumed to be 0.15s.)
Machine specifications
Servo
motor
Servo
amplifier
FX – 1GM
Gear ratio 5:8
Pulse train
Speed of moving part during fast feed Vo = 30000mm/min
Travel per pulse ∆R = 0.005mm
Travel R = 400mm
Positioning time t
o = within 1s
Number of feeds 40 times/min.
Operation cycle t
f = 1.5 s
Gear ratio n = 8/5
Moving part weight W = 60kg
Drive system efficiency η = 0.8
Friction coefficient µ = 0.2
Ball screw lead Pb = 16mm
Ball screw diameter 20mm
Ball screw length 500mm
Gear diameter (servo motor) 25mm
Gear diameter (load shaft) 40mm
Gear face width 10mm