
3. INSTALLATION
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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
A
AC/DC power lines (containing
the power lines for the servo and
spindle motors)
and C, or cover group A with an
electromagnetic shield (Note 2).
See Section 3.6.4 and connect
AC/DC solenoid
spark killers or diodes with the
solenoid and relay.
AC/DC relay
solenoid and 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 I/O unit
and power magnetics cabinet
group B with an electromagnetic
shield.
Separate group B as far from
DI/DO cable between the I/O unit
and machine
Group C as possible.
It is more desirable to cover
group B with the shield.
Cable between the CNC and I/O
unit
Bind the cables in group C sepa-
rately from group A, or cover
Cable for position and velocity
feedback
group C with an electromagnetic
shield.
Cable between the CNC and
spindle amplifier
Separate group C as far from
Group B as possible.
Cable for the position coder
Be sure to perform shield pro-
C
Cable for the manual pulse gen-
erator
cessing in Section 3.6.5.
Cable between the LCD and the
MDI
RS–232C and RS–422 interface
cable
Cable for the battery
Other cables to be covered with
the shield
3.6
ACTION AGAINST
NOISE
3.6.1
Separating Signal
Lines