
B-63945EN/02 5.MATTERS COMMON TO BOTH LCD-MOUNTED TYPE AND STAND-ALONE TYPE (HARDWARE)
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5.11 COUNTERMEASURES AGAINST NOISE
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.
5.11.1 Separation of Signal Lines
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
Secondary side AC power line
AC/DC power lines (including servo motor and
spindle motor power lines)
AC/DC solenoid
A
AC/DC relay
Bind the cables of this group separately from the cables of
groups B and C(*1), or electromagnetically shield the cables of
this group from the cables of groups B and C(*2). According to
the descriptions of noise suppressors in Section 5.8.4, attach
a spark killer or diode to the solenoid and relay.
DC solenoid (24 VDC)
DC relay (24 VDC)
DI-DO cable between I/O unit power
magnetics cabinets
DI-DO cable between I/O unit machines
B
24-VDC input power cables for the control unit
and its peripherals
Attach a diode to the DC solenoid and relay.
Bind the cables of this group separately from the cables of
group A, or electromagnetically shield 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 as possible. Shielding is recommended.
CNC-I/O unit cable
Cables for position loopback and velocity
loopback
CNC-spindle amplifier cable
Position coder cable
Manual pulse generator cable
CNC-MDI cable (*3)
RS-232C and RS-422 cables
Battery cable
C
Other cables whose shielding is specified
Bind the cables of this group separately from the cables of
group A, or electromagnetically shield the cables of this group
from the cables of group A.
Separate the cables of this group from the cables of group B
as far as possible.
Shielding according to Section 5.8.5 is required.