LGK-100.160.200IGBT OPERATOR’S MANUAL
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cutting speed include workpiece thickness, cutting current, air flux and nozzle aperture. A
proper drag is allowed during cutting. The cutting speed should be increased as much as
possible, but the incision quality must be guaranteed.
2.
Eliminate the cutting burr
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The characteristics of the incision burr
The ordinary cutting surface is smooth and clean, but if the parameter selection is not
suitable, and electrode centering is not good, then burr may be formed on the cutting
surface.
Slag is formed by molten metal and its oxide which is adhesive to the bottom edge of
incision and solidified. The reason for forming this slag is that the molten metal adhesive
strength is bigger than the gravity and blow strength of metal oxide.
When cutting the alloy steel, the molten metal is difficult to be blown away because
of its bad fluidity, in addition, the alloy steel have bad thermal conductivity, the incision
bottom is over-heated easily, the left molten metal and incision bottom melts into one,
thereby the irremovable and tough burr is formed.
On the contrary, the incision bottom is difficult to be melted together with molten
metal, and the burr formed under incision is come off easily.
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The factors affecting the forming of burr
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The fluidity of the molten metal is not good, when the power is too small or the plasma
arc compression effect is not good, the temperature of molten metal during the cutting
process is low, fluidity is weak, even if the air current blow force is strong, it is still
difficult to blow away the metal completely, so the burr is formed.
¾
When cutting the thick plate, the burr is caused by the drag of overlarge cutting seam.
During the cutting process, the heat received by different parts of metal is different, the
heat on the upper incision is larger than that of the lower incision, so the upper part
melting speed is faster than that of lower part, thereby a distance between them is formed,
it is called drag L of cutting seam. The drag size is related to plasma arc shape and cutting
speed. When the flame is short while the cutting speed is too fast, drag L increases, so
the vertical and horizontal blow force of the arc is formed, the vertical one helps to blow
away the molten metal, while the horizontal one makes the molten metal flow backward
along with incision bottom, this over-heated metal will melt parts of the bottom metal
again, then the burr is formed when they cool down and melt together.
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The burr is caused by overheat bottom. When the cutting speed is too slow, but the
incision bottom is so over-heated that it melts, the liquid metal flows to bottom metal and
combines into one which makes the difficulty to blow away molten metal by air current,
and then the burr is formed.
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The air current blow force is not enough. When cutting with plasma, the arc blow force
consists of the air current blow force and the arc electromagnetic force, the air current
blow force acts the main function. If the air current blow force is not strong enough, it
cannot ensure all the burr is flown away, then the burr is formed.
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The measurement to eliminate burr
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Ensure the centering between electrode and nozzle precisely, so that the compression
of the plasma arc is not damaged, the concentration of flame and cutting capacity can be
guaranteed.
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Enough power to ensure the fluidity of molten metal, as well as increase the stability
of the cutting speed and operation. This makes it possible to adopt large air flux to enlarge
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