
B–63325EN/03
2. 15i SERIES HARDWARE
215
The CNC is becoming increasingly smaller as the surface mount
technology and custom LSI technology advance.
In many cases, as the CNC becomes more compact, the mounting
locations of its constituent units become closer to a noise source in the
power magnetics cabinet.
In general, noise is generated by electrostatic coupling, electromagnetic
induction, or a grounding loop, and is induced into the CNC.
The CNC incorporates sufficient countermeasures against external noise.
However, it is difficult to measure the level and frequency of noise
quantitatively, and many unknown factors are involved. So, to improve
the operation stability of a CNC machine tool system, noise generation
must be minimized, and the induction of generated noise into the CNC
must be suppressed.
For design of equipment including a power magnetics cabinet, take these
countermeasures on the machine side against noise into consideration.
The cables used with a CNC machine tool are classified as indicated
below. Handle the cables of each group according to the descriptions in
the “Action” column.
Group Signal Action
Primary side AC power line Bind the cables of this group sep-
arately from the cables of groups
Secondary side AC power line
arately from the cables of groups
B and C(*1), or electromagneti-
A
AC/DC power lines (including servo motor
and spindle motor power lines)
cally shield the cables of this
group from the cables of groups B
and C(*2). According to the de-
AC/DC solenoid
scriptions of noise suppressors in
Section 2.15.4, attach a spark kill-
AC/DC relay
er or diode to the solenoid and
relay.
DC solenoid (24 VDC) Attach a diode to the DC solenoid
and relay.
DC relay (24 VDC)
Bind the cables of this group sep-
arately from the cables of group
A, or electromagnetically shield
B
DI–DO cable between I/O unit power mag-
netics cabinets
the cables of this group from the
cables of group A.
Separate the cables of this group
from the cables of group C as far
DI–DO cable between I/O unit machines
from the cables of group C as far
as possible. Shielding is recom-
mended.
CNC–I/O unit cable Bind the cables of this group sep-
Cables for position loopback and velocity
loopback
arately from the cables of group
A, or electromagnetically shield
the cables of this group from the
CNC–spindle amplifier cable
the cables of this group from the
cables of group A.
Position coder cable
Separate the cables of this group
from the cables of group B as far
C
Manual pulse generator cable
from the cables of group B as far
as possible.
LCD unit–MDI cable or CNC–MDI cable(*3)
Shielding according to Section
2.15.5 is required.
RS–232C and RS–422 cables
2.15.5 is required.
Battery cable
Other cables whose shielding is specified
2.20
COUNTERMEASURES
AGAINST NOISE
2.20.1
Separation of Signal
Lines