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6.2 Focus position
Focus position is a key parameter, which shall be correctly adjusted.
Influence of focus position on cutting section
Zero focal length
Focus is on the
workpiece
surface
Applicable to thin plate.
(Cut surface)
The focus is positioned on upper workpiece
surface, so the cutting width is narrow and
the cutting speed is faster.
Negative focal
length
Focus is under
the workpiece
surface
This method is applied in thick aluminum
plate, stainless steel, copper plate and
other workpieces.
(Cut surface)
Comparing with the condition adopting
zero focal length, with the focus located at
the center, the cutting width, flow rate of
cutting gas and the time of piercing is
greater due to the wide range of smooth
surface.
Positive focal
length
Focus is above
the workpiece
surface
Applied when cutting thick steel plate.
When the thick steel plate is cut down, the
oxidation of cutting oxygen shall thoroughly
run from the upper surface to the bottom
surface. Wider cutting width can be
obtained on a plate due to its own needs.
The cut surface is rough due to the oxygen,
which is similar to the surface cut off by gas.
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