Tweco SC11 - Manual (Page 27)

Manual 0-2556 4-3 OPERATION
4.04 Sequence Of Operations
This Section describes the typical sequences for various
operations. The information is suppied to give the op-
erator an understanding of what is occuring during the
cutting cycle. Each of the following paragraphs describe
a different operation as follows:
• Paragraph ‘A’ - Fully Automatic Mode With Pierce
Start
• Paragraph ‘B’ - AUTO HT ON and FIND HT indi-
cators OFF
• Paragraph ‘C’ - AUTO HT Indicator OFF and FIND
HT Indicator ON
• Paragraph ‘D’ - Fully Manual Mode
• Paragraph ‘E’ - Starting Off The Plate
A. Fully Automatic Mode (AUTO HT and FIND
HT Indicators ON) With Pierce Start
1. The cutting machine controller sends a start signal to
the Standoff Control.
2. The Standoff Control starts to find height by rapidly
lowering the torch from the retracted position towards
the work. When the torch contacts the work or the
bottom of torch travel if not over the work, it opens
the normally closed (NC) torch on work (T.O.W.)
switch in the Lifter Motor Assembly.
3. When the T.O.W. switch opens the torch downward
motion is reversed and it slowly rises until the T.O.W.
switch closes which starts the PIERCE HT timer. The
torch continues upward for the time required to reach
the selected pierce height setting.
4. A start signal is sent to the Plasma Power Supply and
the Standoff Control PLASMA ON indicator turns
ON. The pilot starts after pre-flow and immediately,
if the initial height is correct, the cutting arc is estab-
lished at which time the Plasma Power Supply sends
a motion (OK-To-Move) signal to the Standoff Con-
trol through the Remote Control.
5. Receiving the motion (OK-To-Move) signal from the
Plasma Power Supply starts the PIERCE DELAY. As
the PIERCE DELAY ends the motion (OK-To-Move)
signal is sent to the cutting machine controller through
the Remote Control starting the horizontal travel.
6. At the same time, the T.H.C. ACTIVE indicator turns
ON and the torch moves to the desired cutting stand-
off as determined by the pre-selected ARC VOLTS
Control, unless the cutting machine standoff inhibit
(corner slowdown - CSD) is ON, or the arc voltage is
outside the range of 65 to 195V inhibiting it. Even if
the standoff is inhibited, because the cut is starting in
a corner, the controller is enabled for 1/2 second to
position the torch down to the proper cutting height.
Without this feature the first few inches could be cut
at excessive standoff adversely affecting the quality.
7. The piece is cut then the cutting machine removes the
start signal. The arc goes out removing the motion
(OK-To-Move) signal from the Plasma Power Supply.
8. When both the start and motion (OK-To-Move) sig-
nals are removed (allows for current ramp down for
systems that have that feature) the retract timer is ac-
tivated to rapidly raise the torch up to clear obstruc-
tions, such as cut out pieces that tilt up, while travers-
ing to the next piece to be cut. The amount of retract
is set from zero to 100% by the END OF CUT RE-
TRACT Control. The torch remains retracted until the
sequence repeats with the next start signal.
B. AUTO HT ON and FIND HT indicators OFF
The operator sets the torch height manually. Refer to
paragraph 'D' for "Starting Off The Plate (Workpiece)".
1. The cutting machine controller sends a start signal to
the Standoff Control.
2. A start signal is sent to the Plasma Power Supply and
the Standoff Control PLASMA ON indicator turns
ON. The pilot starts after pre-flow and immediately,
if the initial height is correct, the cutting arc is estab-
lished at which time the Plasma Power Supply sends
a motion (OK-To-Move) signal to the Standoff Con-
trol.
3. Receiving the motion (OK-To-Move) signal from the
Plasma Power Supply starts the PIERCE DELAY. As
the PIERCE DELAY ends the motion (OK-To-Move)
signal is sent to the cutting machine controller, start-
ing the horizontal travel.
4. At the same time, the T.H.C. ACTIVE indicator turns
ON and the torch moves to the desired cutting stand-
off as determined by the pre-selected ARC VOLTS
Control, unless the cutting machine standoff inhibit
(corner slowdown - CSD) or the arc voltage is outside
the range of 65 to 195v inhibiting it. Even if the stand-
off is inhibited, because the cut is starting in a corner,
the controller is enabled for 1/2 second to position
the torch down to the proper cutting height. Without
this feature the first few inches could be cut at exces-
sive standoff adversely affecting the quality.
5. The piece is cut then the cutting machine removes the
start signal. The arc goes out removing the motion
(OK-To-Move) signal from the Plasma Power Supply.
6. The torch does not retract.