B–63505EN/02
2. HARDWARE
119
The CNC has been steadily reduced in size using surface–mount and
custom LS1 technologies for electronic components. The CNC also is
designed to be protected from external noise. However, it is difficult to
measure the level and frequency of noise quantitatively, and noise has
many uncertain factors. It is important to prevent both noise from being
generated and generated noise from being introduced into the CNC. This
precaution improves the stability of the CNC machine tool system.
The CNC component units are often installed close to the parts generating
noise in the power magnetics cabinet. Possible noise sources into the CNC
are capacitive coupling, electromagnetic induction, and ground loops.
When designing the power magnetics cabinet, guard against noise in the
machine as described in the following:
The cables used for the CNC machine tool are classified as listed in the
following table :
Bind the cables in each group as described in the action column.
Group Signal line Action
A Primary AC power line Bind the cables in group A separately
Secondary AC power line
(Note 1) from groups B and C or cover
group A with an electromagnetic shield
AC/DC power lines (containing the
power lines for the servo and spindle
motors)
group A with an electromagnetic shield
(Note 2).
Connect spark killers or diodes with
the solenoid and relay.
AC/DC solenoid
the solenoid and relay.
AC/DC relay
B DC solenoid (24VDC) Connect diodes with DC solenoid and
DC relay (24 VDC)
relay.
Bind the cables in group B separately
DI/DO cable between the CNC and
power magnetics cabinet
from group A or cover group B with an
electromagnetic shield.
Separate group B as far from group C
DI/DO cable between the CNC and ma-
chine
as possible.
It is more desirable to cover group B
with the shield.
C Cable between the CNC and
servo amplifier
Bind the cables in group C separately
from group A or cover group C with an
Cable for position and velocity feed-
back
electromagnetic shield.
Separate group C as far from group B
Cable between the CNC and spindle
amplifier
as possible.
Be sure to perform shield processing.
Cable for the position coder
Cable for the manual pulse generator
Cable between the CRT (LCD) and MDI
RS232C and RS422 interface cables
Cable for the battery
Other cables to be covered with the
shield
NOTE
1 The groups must be 10 cm or more apart from one another
when binding the cables in each group.
2 The electromagnetic shield refers to shielding between
groups with grounded steel plates.
2.11
ACTION AGAINST
NOISE
2.11.1
Separating Signal
Lines