4.
4.1
The
CABINET DESIGN FOR HEAT
FACTORS
SELECTION OF HEAT EXCHANGER
cabinets to contain the CNC unit and other units should beef a
totally -enclosed type. The inner-air temperature differential inside
the cabinets should be less than 10”C. Heat exchangers may be
needed inside the cabinets depending on the heat generated by the
installed electric equipment. Determine the heat exchanger
capacity as follows :
AT: Air temperature rise inside cabinet (“C)
Pv : Total heat generated by electric equipment (W)
k : Cabinet heat transmission [W/(m2 . ‘C)]
Calculate based on 6W/(m’ ‘C) if a circulating fan is
installed.
A : Effective radiation area of cabinet (m’)
qh : Heat exchange ratio of necessary heat exchanger.
1. Calculate the total heat value Pv of the electric equipment.
Pv=Z (Heat value of each unit)
2. Calculate the effective heat radiation area A.
A=2
x {W (width) x H (height) }+ 2 {W (width)
x D (depth)] + 2 {D (depth) x H (height))
The surfaces that are not exposed to external air are ineffective
areas.
L
A
A
~ : INEFFECTIVE AREAS
Note : If 50 mm or less from the floor,
bottom areas are ineffective.
3. Calculate the allowable heat value Pv’ that ensures the
temperature increase within cabinet (AT) to be less than 10°C.
Pv’=k. A. AT (W)
Llo”c
L-
6W (mz. “C)
4. A heat exchanger is not needed if total heat value Pv S allowable
heat value Pv’.
5. A heat exchanger has to be installed with the following heat
exchange ratio (heat exchanger capacity) qh if total heat value
Pv > allowable heat value Pv’.
qh=
(pv-pv’)/ AT (W/”C)
Llo”c
4.2 HEAT VALUES OF UNITS
4.2.1
4.2.2
NC UNIT
Table 4.1 Heat Values of NC Unit
Unit I Heat Value (W)
CNC Unit*
I
103
CNC Operator’s Panel
I
17
Tape Reader
25
1/0 Module
I
5
*
Heat value of CNC unit changesby adding the option.
SERVO UNIT
Table 4.2 Heat Value of Servo Unit
Unit
Type
Total Heat
Internal Heat
Regenerative
SGDB-
Value (W)
Value (W)
Resistance (W)
05AD
50
25
28
lOAD
I
70
I
35
I
28
15AD
I
90 45
28
20AD
130
65
28
30AD
I
180
I
90
I
28
44AD
I
210 105
28
60AD
370 135
75AD
480 240
1AAD
600 300
Notes :
1.The servo unit uses two shafts, and its load factor should be 70 to 80%.
2. The internal heat value is the heat value remaining inside if the heat fin
is installed outside.
3. Heat value created by regenerative resistance will differ depending on
the frequency of rapid feed starts and stops.
4. Regenerative circuits are incorporated in the unit types SGDB-05 to
1A and are mounted externally for the types SGDB-60 to 1A as
options.
5. Capacity of regenerative circuit is calculated by 200% of allowable
dissipation.
3
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