AIRCUT
-101
I
,161
IW
,200
IW Inverter Plasma Cutting Machine
WARPP ENGINEERS PVT LTD
24
The three main dimension of nozzle are the diameter of nozzleφ, the hole pass
length ι and the compacted angle α, they all can affect the cutting. There should be a
certain proportion between ι and φ, the value is usually lower than 2, and it usually
takes
ι
= 1.5 ∼1.8
, the compact angle usually takes α
＝
30°
～
60°, and now it usually
Φ
takes α
＝
30°.
3) Cutting current and arc voltage
The selection of cutting current should be according to the diameter of the nozzle,
therelationship between thetwo should be as:I(current A)
＝
(70
～
100)×φ(mm). As the
increase of the metal thickness, the influence of arc current to the cutting speed will
become less. But as the increase of current, the burning damage will be worse for the
electrode and the nozzle. So when cutting a thick metal work-piece, usually the increase
of cutting speed is made by increasing arc voltage. The actual arc voltage is decided not
only by the gas type but also by the air flux and nozzle shape. Working voltage increases
with the increase of gas flux.
4) Gas flowQ
The arc voltage increases as the increase of air flow, that is, the arc power, the
cutting speed, as well as the cutting capacity and quality is improved accordingly.
Because the arc compression level increases, the energy is more concentrated, the arc
beam temperature, the arc spraying speed, as well as the arc current impulsion increases.
But overlarge current may cause the instability of the plasma arc. Usually no change is
made to air flow for one torch. But it can be adjusted a little when the cutting torch or
cutting thickness isdifferent.
5) Electrode inner contraction ∆L
y
When electrode inner contraction
∆L
y
is so small that electrode extends into spray
hole, electrode is damaged seriously by air flow impact and the combination function
between high temperature gas and electrode. This leads to the instability of plasma arc,
weak compression effect, and weak cutting penetration ability that cutting cannot be
proceeded. If ∆L
y
is too big, the arc is so unstable that the cutting ability is weakened.
The electrode end should be placed within siphoning zone of gas current under a relative
vacuum condition, and it will difficult to damage electrode by burning, as well as this is
beneficial for compression of arc.
∆L
y
is about 2-4mm.
6) The distance between the nozzle and the work-piece (d)
If the d is too big, the blow power of plasma arc for molten metal decreases, so does
the cutting ability, and the burr on the bottom increases, meanwhile the instability of
thearc increases. However,if the d is too small,it increases thepossibility of short circuit
between the nozzle and the work-piece. Usually d should be as small as possible on
condition that no short circuit is caused between nozzle and work-piece. The d under
normal cutting of air plasma is usually 2
～
5mm. The work-piece can also contact with
the nozzle during air plasma cutting, that is, the nozzle glide on the surface of the
work-piece. This cutting method is called contact cutting, and the cutting thickness is the
half as the ordinary cutting.
7) Open circuit voltage
The power source with high open circuit voltage is required for cutting thick
work-piece.Theopencircuitvoltageisrelatedwithairtype,forexample,byusingargon
