
B–63833EN/03
3. INSTALLATION
16
The CNC has been steadily reduced in size using surface–mount and
custom LSI 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 section.
The cables used for the CNC machine tool are classified as listed in the
following table:
Process the cables in each group as described in the action column.
Group Signal line Action
Primary AC power line
Bind the cables in group A sepa-
Secondary AC power line
rately (Note 1) from groups B
and C, or cover group A with an
A
AC/DC power lines (containing the
power lines for the servo and
spindle motors)
electromagnetic shield (Note 2).
See Subsec. 3.5.4 and connect
spark killers or diodes with the
solenoid and relay.
AC/DC solenoid
solenoid and relay.
AC/DC relay
DC solenoid (24VDC)
Connect diodes with DC sole-
noid and relay.
DC relay (24VDC)
Bind the cables in group B sepa-
rately from group A, or cover
B
DI/DO cable between the CNC
and power magnetics cabinet
group B with an electromagnetic
shield.
Separate group B as far from
DI/DO cable between the CNC
and machine
Group C as possible.
It is more desirable to cover
group B with the shield.
3.5
ACTION AGAINST
NOISE
3.5.1
Separating Signal
Lines