2 - Fagor Automation

Selection criteria
5.
SELECTING CRITERIA
Selection of the synchronous motor and its associated drive
232
DDS
HARDWARE
Ref.1307
206
The continuous torque M S :
is due to:
• the friction between table with its ways and with the ballscrew M F ,
• the weight of the table when not moving horizontally M W,
• the cutting force of the tool M C .
Friction torque M F :
where:
M
S
= M
F
+ M
W
+ M
C
M
CONTINUOUS
= M
FRICTION
+ M
WEIGHT
+ M
CUTTING
M
F
M F –
+ M
TABLE F –
BALLSCREW
1
= -- =
i
MF Torque due to friction in N·m.
m Table mass in kg.
d Leadscrew diameter in m.
g Gravitational acceleration, 9.81 in m/s².
h Leadscrew pitch per turn in m.
µ The friction coefficient between the table and the ways it moves on:
typical µ values depending on material:
Iron 0.1 ÷ 0.2
Turcite 0.05
Roller bearings 0.01 ÷ 0.02
Torque due to the weight of the table Mw :
When the table does not move horizontally, but at an angle like in figure
F. H5/1 the torque due to the weight of the table must also be considered.
M W
mg sinh ------------------------------------
2
%
---i
MW Torque due to the weight of the table in N·m.
Inclination angle of the ballscrew with respect to the horizontal axis.
% Table weight compensation factor that can vary between 0 and 1.
If the total table weight is compensated for by means of some sort of hydraulic
system or counterweights so the motor makes the same effort to
move the table up as to move it down, the % factor will be 0. At the other
end, if no compensation is applied, % will be 1.
Torque due to the needed cutting force Mc: There is a cutting force between the tool and the part and this means a
hindrance for moving the table. The torque necessary at the motor to
make this movement is calculated as follows:
MC Torque due to the cutting force of the tool in N·m.
F Cutting force of the tool in kg-force.
g Gravitational acceleration, 9.81 in m/s².
=
M
C
=
Fgh ------------------
2
1
--
i
mg h
d---------------------------
+ -----
2 10
1
--
i