The PLC is located in the top section of the Flow Control
and is a device capable of providing predefined outputs
depending on the state of the inputs. The precise condi-
tions are programmed and permanently stored in the PLC.
section 5
Because it is a solid state device the PLC is inherently
very reliable. It is also relatively compact.
The PLC will provide predefined outputs in response to
inputs from external devices. This exchange of signals
5.1
Programmable Logic controller (PLc)
can be confirmed by observing the LEDs on the top of
the PLC while troubleshooting. These indications are
useful in isolating a system failure to the most likely de-
The PLC is located in the top section of the Flow Control and is a device capable of providing predefined outputs depending
vice. They can be seen through window in the Flow Con-
on the state of the inputs. The precise conditions are programmed and permanently stored in the PLC. Because it is a solid
trol top cover.
state device the PLC is inherently very reliable. It is also relatively compact.
The LEDs are divided into two groups; Input (0-15) and
The PLC will provide predefined outputs in response to inputs from external devices. This exchange of signals can be con-
Output (0-11). Input LEDs light when the corresponding
firmed by observing the LEDs on the top of the PLC while troubleshooting. These indications are useful in isolating a system
signal is detected by the PLC. Output LEDs light when
failure to the most likely device. They can be seen through window in the Flow Control top cover.
the PLC issues a signal to an external device. The fault
LED (output 1) indicates the PLC has detected an error
The LEDs are divided into two groups; Input (0-15) and Output (0-11). Input LEDs light when the corresponding signal is
within the ESP and has caused the system to enter the
detected by the PLC. Output LEDs light when the PLC issues a signal to an external device. The fault LED (output 1) indicates
not ready (fault) state.
the PLC has detected an error within the ESP and has caused the system to enter the not ready (fault) state.
LEDs are highly reliable indicators. It is not likely that one
LEDs are highly reliable indicators. It is not likely that one will burn out. However, if the technician is not confident that the
will burn out. However, if the technician is not confident
LEDs are working the presence of a signal can be confirmed by using a meter to measure the appropriate pin. Refer to the
that the LEDs are working the presence of a signal can
schematic and wiring diagrams.
be confirmed by using a meter to measure the appropri-
ate pin. Refer to the schematic and wiring diagrams.
The signal exchange between the PLC and external devices are both time dependent and condition dependent. If a required
signal is not received in the proper sequence, the PLC will discontinue the process and generate a fault signal to the CNC.
The signal exchange between the PLC and external de-
vices are both time dependent and condition dependent.
If a required signal is not received in the proper sequence,
the PLC will discontinue the process and generate a fault
signal to the CNC.
Figure 5-1 PLc LeD Panel (Partial View)
Figure 4-1. PLC LED Panel (Partial View)
LED
FUNCTION
0
Start/Stop
1
Current Detector
2
Nitrogen Pressure
3
Oxygen Pressure
4
Interlock Plumb.Box
5
Cooling Water Flow
6
Cut Water Flow
7
Cut Gas Pressure
8
Run 1
9
O2/N2 Select
10
Emergency Stop
11
Cut Water On/Off
12
Test Cut Gas
13
Test Start Gas
14
Run 2
15
Test HF
4.2 Sequence Description
The program controlling the plasma system sequence is
made with the help of a group of conditional states. Inputs
from sensors, and the cutting machine are continuously
evaluated by the PLC to determine whether the program
stays in its present state or makes a transition to another
state.
The different states are shown as rectangles in figure 4-
2. The function of the seven states are described in the
following paragraphs.
0 - Ready state
The "Ready" state is the normal state for the system to be
in when not executing the cutting process. In this state,
the system awaits the start signal from the cutting ma-
table 5-1 PLc input / output LeDs
chine and monitors the selection keys and safety switches.
input
While in this state it is possible to activate the gas flows
and cut water flow for testing and purging the system.
LeD
Function
0
Start / Stop
1 - Preflow state
1
Current Detector
The "Preflow" state is a fixed duration and is reached only
2
Nitrogen Pressure
from state "0". Nitrogen is always the preflow gas in RUN
3
Oxygen Pressure
1 position. Selected cut gas type and flow is the preflow
4
Interlock Plumb. Box
gas in RUN 2 position. Cut water flow during preflow
whenever a water injection torch is used and cut water is
5
Cooling Water Flow
switched on at the front panel. The air curtain output is
6
Shield Gas Flow
energized at this time also.
7
Cut Gas Pressure
8
Run 1
2 - Open Circuit Voltage State
9
O
/ N
2
2
The main contactor of the power source is activated after
10
Emergency Stop
the preflow, and a short time is allowed for the open circuit
Shield Gas -
voltage to be reached.
11
Enabled / Disabled
68
12
Test Cut Gas
13
Test Start Gas
14
Run 2
15
Test HF
301
LED
FUNCTION
0
Process Running
1
Fault Signal
2
Power Source On/Off
3
Cut Water On/Off
tRoUBLesHootinG
4
5
6
Air Curtain
7
Cut Gas Metering
8
Cut Gas On/Off
9
Start Gas On/Off
10 HF On/Off
11
LeD
0
Process Running
1
Fault Signal
2
Power Source On/Off
3
Shield Gas On / Off
4
5
6
Air Curtain
7
Cut Gas Metering
8
Cut Gas On / Off
Select
9
Start Gas On / Off
10
HF On/Off
11
output
Function