Operator’s panel
A machine tool of the door and the operator’s panel are contiguous, please attach the rubber or a damper for the measures of shock when opening and closing the door.
Machine door
3.3 THERMAL DESIGN OF THE MACHINE TOOL MAGNETIC CABINET
The internal air temperature of the cabinet increases when the units and parts installed in the cabinet generate heat. Since the generated heat is radiated from the surface of the cabinet, the temperature of the air in the cabinet and the outside air balance at certain heat levels. If the amount of heat generated is constant, the larger the surface area of the cabinet, the less the internal temperature rises. The thermal design of the cabinet refers to calculating the heat generated in the cabinet, evaluating the surface area of the cabinet, and enlarging that surface area by installing heat exchangers in the cabinet, if necessary.
Such a design method is described in the following subsections.
3.3.1 Temperature Rise within the Machine Tool Magnetic Cabinet
The cooling capacity of a cabinet made of sheet metal is generally 6 W/°C per 1m2 surface area, that is, when the 6W heat source is contained in a cabinet having a surface area of 1 m2, the temperature of the air in the cabinet rises by 1°C. In this case the surface area of the cabinet refers to the area useful in cooling, that is, the area obtained by subtracting the area of the cabinet touching the floor from the total surface area of the cabinet. There are two preconditions : The air in the cabinet must be circuited by the fun, and the temperature of the air in the cabinet must be almost constant. For example, the operator’s panel cabinet may contain an LCD-mounted type control unit. To keep the temperature in the cabinet at 58°C or below when the ambient temperature is 45°C, the equation below must be satisfied.
Internal heat loss P [W] ≤
6[W/m2⋅°C] × surface area S[m2] × 13[°C] of rise in temperature
(A cooling capacity of 6 W/°C assumes the cabinet is so large that agitation with the fan motor does not make the temperature distribution uniform. For a small cabinet like the operator's panel, a cooling capacity of 8 W/°C, indicated in Subsection 3.3.3, may be used.)
For example, a cabinet having a surface area of 4m2 has a cooling capacity of 24W/°C. To limit the internal temperature increase to 13°C under these conditions, the internal heat must not exceed 312W. If the actual internal heat is 360W, however, the temperature in the cabinet rises by 15°C. When this happens, the cooling capacity of the cabinet must be improved using the heat exchanger.
3.3.2 Heat Output of Each Unit
Table 3.3.2 Heat output
Unit Heat output Remarks
LCD-mounted type control unit
8.4”LCD unit Option 0 slot 32W Note 1)
Option 2 slots
10.4”LCD unit Option 0 slot 32W Note 1)
Option 2 slots
15”LCD unit Option 0 slot 37W Note 1)
Option 2 slots Optional board Fast Ethernet board
(when used as data server functions)
3W (3.3W)
HSSB interface board 4W
PROFIBUS-DP master board 5W
PROFIBUS-DP slave board 2W
DeviceNet master board 3W
DeviceNet slave board 3.5W
CC-Link remote device station board 3W
MDI units 0W
NOTE
1 The values listed above do not include any heat output of the option boards. To obtain the total heat output of the control unit, add the heat output from the any option boards.
2 See Chapter 6 for the heat output of the separate detector interface unit.
3 See Chapter 8 for the heat output of each I/O unit.
4 Refer to the PANEL i Connection and Maintenance Manual (B-64223EN) for the heat output of the PANEL i.
3.3.3 Thermal Design of Operator's Panel
With a small cabinet like the operator's panel, the heat dissipating capacity of the cabinet is as shown below, assuming that there is sufficient mixing of the air inside the cabinet.
Coated metal surfaces: 8 W/m2°C Plastic surfaces: 3.7 W/m2°C
An example of the thermal design for the cabinet shown in Fig. 3.3.3 is shown below.
Fig. 3.3.3
Assume the following.
Thermal exchange rates
Coated metal surfaces : 8 W/m2⋅°C Plastic surfaces : 3.7 W/m2⋅°C
Allowable temperature rise : 13°C higher than the exterior temperature
Surface area of metallic sections : 0.5722 m2 Surface area of plastic sections : 0.2632 m2
In this case, the allowable total heat dissipation for the cabinet is:
8 × 0.5722 × 13 + 3.7 × 0.2632 × 13 = 72 W.
In consequence, it can be concluded that the units shown in Table 3.3.3 on the next page can be installed in this cabinet.
Table 3.3.3
LCD-mounted type control unit (with 10.4”LCD unit) 32W
Standard machine operator's panel 15W(Note)
120-mm square fan motor for air mixing 8W
Total heat dissipation of the above 55Ｗ
NOTE
The 15 W quoted for the standard machine operator's panel represents an example heat output value when half of all the input signals are turned on. This value varies, depending on the mechanical configuration.
3.4 COUNTERMEASURES AGAINST NOISE AND GROUNDING
In general, noise can occur because of electrostatic coupling, electromagnetic induction, and ground loop and get in a control unit.
On the control unit side, due consideration is paid to a protective measure for external noise. However, it is hard to measure the magnitude and frequency of noise quantitatively and there are lots of uncertainties with noise. So, it is important to take measures for minimizing noise occurrence and keeping any noise from entering the control unit in order to enhance stability in CNC-based machine tool system operation.
Grounding the power magnetics cabinet and devices is very important to prevent an electric shock and suppress a noise influence. The CNC system uses the following three types of grounding:
(1) Signal grounding
This type of grounding is used to supply a reference potential (0 V) for the electrical signal system.
(2) Frame grounding
This type of grounding is used for safety reasons as well as to suppress external and internal noise.
For example, grounding is provided for the device frames, panels, and shielding on the interface cables connecting the devices.
(3) System grounding (PE)
This type of grounding is used to connect frame grounds, which are provided for the individual devices or between the units, to the ground as a system at a single point.
When designing the power magnetics cabinet, guard against noise in the machine as described in the following section.
3.4.1 Grounding as Noise Suppression Measures
3.4.1.1 Grounding methods
Typically, noise that becomes a problem is high–frequency noise. To suppress high–frequency noise, it is important that the devices are grounded at low impedance(NOTE).
The grounding schemes for this purpose are described below.
NOTE