Elettro 455 Manuel D'instructions page 15

6.3. To pierce a workpiece using the machine torch
As with the hand torch, you can start a cut with the machine
torch at the edge of the workpiece or by piercing the
workpiece. Piercing will result in a shorter consumable life than
with edge starts.
The cut charts include a column for the height at which the
torch should be when starting a pierce and a column for the
delay of piercing.
Notes: when piercing maximum thicknesses, the ring of dross
that forms during the pierce may become high enough to
contact the torch when the torch begins to move after the
pierce is complete.
6.4. Common machine-cutting faults
- The torch pilot arc will initiate, but will not transfer. Causes
can be:
• The work cables connection on the cutting table is not
making good contact or the table is not properly
grounded.
• The torch-to-work distance is too great.
- The workpiece is not totally penetrated, and there is
excessive sparking on the top of the workpiece. Causes
can be:
• The work cable's connection on the cutting table is not
Inspect the consumables
Consumable part
Insulating diffusor
O-ring for torch
Examine
The centre hole for roundness.
The space between the shield cup
Shield cup
and the nozzle for accumulated
debris.
The centre hole for roundness.
Nozzle
Good
The centre surface for wear and verify
the pit depth
Electrode
The internal surface of the diffusor for
damage or wear and the gas holes for
obstructions.
The surface for damage, wear or a
lack of lubrication.
head
making good contact or the table is not properly
grounded.
• The voltage is set too low.
• The cut speed is too high.
• The consumables are worn and need to be replaced.
• The metal being cut exceeds the maximum capacity.
- Dross forms on the bottom of the cut. Causes can be:
• The cutting speed is not correct.
• The voltage is set too low.
• The consumables are worn and need to be changed.
- The cut angle is not right. Causes can be:
• The direction of the torch travel is incorrect. The high-
quality cut is always on the right with respect to the
forward motion of the torch.
• The torch-to-work distance is not correct.
• The cutting speed is not correct.
• The consumables are worn and need to be replaced.
- The consumable life is shortened. Causes can be:
• The arc current, arc voltage, cuting speed, and other
variables are not set as specified in the cut charts.
• Firing the arc in the air (beginning or ending the cut off of
the plate surface). Starting at the edge is acceptable as
long as the arc makes contact with the workpiece when
started.
• Starting a pierce with an incorrect torch height.
Worn
Maximum 1.5 mm
15
Action
If the hole is no longer round, replace the
shield.
Remove the shield cup and clean any material
away.
If the centre hole is not round, replace the nozzle
and the electrode together.
If the surface is worn or the pit depth is greater
than 1.5 mm deep, replace the nozzle and the
electrode together.
Replace if the internal surface is damaged or
worn or any of the gas holes are obstructed.
If the o-ring is dry, lubricate it and the threads with
a thin layer of silicone lubricant. If the o-ring is
cracked or worn, replace it.