
B–63083EN/02
3. INSTALLATION
31
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
p
arately (Note 1) from grou
p
Secondary AC power line
B and C, or cover group A with an
electromagnetic shield (Note 2)
A
AC/DC power lines (containing the
power lines for the servo and spindle
motors)
.
See Subsec. 3.6.4 and connect
spark killers or diodes with the
solenoid and relay.
AC/DC solenoid
AC/DC relay
DC solenoid (24VDC)
Connect diodes with DC
solenoid and relay.
DC relay (24VDC)
Bind the cables in group B
separately from group A, or
p
B
DI/DO cable between the CNC and
power magnetics cabinet
cover group
w
an
electromagnetic shield.
Separate group B as far from
p
p
DI/DO cable between the CNC and
machine
.
It is more desirable to cover
group B with the shield.
3.6
ACTION AGAINST
NOISE
3.6.1
Separating Signal
Lines