Telwin Plasma 31 Bedienungsanleitung Seite 8

the main power supply.
- Table 1 (TAB. 1) shows the recommended sizes for the delayed fuses
on the power supply line, calculated according to the max. nominal
output current of the machine, and to the rated power supply voltage.
WARNING! Failure to comply with the above rules will
render the manufacturer's (class I) safety system ineffective, with
consequent serious risks to people (e.g. electric shock) and to
property (e.g. fire).
CUTTING CIRCUIT CONNECTIONS
WARNING! BEFORE
CONNECTIONS MAKE SURE THAT THE POWER SOURCE HAS BEEN
SWITCHED OFF AND DISCONNECTED FROM THE MAIN POWER
SUPPLY.
Table 1 (TAB. 1) shows the recommended values for the return cable (in
mm ), based on the maximum current output from the machine.
2
Compressed air hookup (FIG. G).
- Prepare a compressed air distribution line with minimum pressure
and capacity as given in table 2 (TAB. 2), for those models where it is
provided.
IMPORTANT!
Do not exceed the maximum input pressure of 8 bar. Air containing
substantial quantities of moisture or oil may cause excessive wear on
the consumable parts or damage the torch. If the quality of the available
compressed air is doubtful, we recommend using an air dryer, to be fitted
upstream of the input filter. Use a flexible pipe to connect the compressed
air supply to the machine, fitting one of the supplied connectors to the
input air filter on the back of the machine.
Connecting the cutting current return cable.
Connect the cutting current return cable to the piece to be cut or to the
metal support bench, taking the following precautions:
- Make sure there is a good electrical contact, especially when cutting
sheet that has an insulated coating or is oxidised etc.
- Make the earth connection as close as possible to the cutting area.
- Using metal structures that are not part of the workpiece as the
cutting current return conductor may endanger safety and result in an
inadequate cut.
- Do not make the earth connection to the part of the piece that is to be
cut away.
Connecting the plasma cutting torch (FIG. H) (where provided).
Insert the male terminal of the torch into the centralised connector on
the front panel of the machine, matching the polarisation key. Tighten
the locking ring nut, clockwise as far as it will go, to ensure air and current
passage with no leaks.
For some models the supplied torch is already connected to the power
source.
IMPORTANT!
Before starting a cutting operation, make sure the consumable parts have
been fitted correctly by inspecting the head of the torch, as described in
the chapter on "TORCH MAINTENANCE".
6. PLASMA CUTTING: DESCRIPTION OF THE PROCEDURE
The plasma arc and the application principle in plasma cutting.
Plasma is a gas that is heated to an extremely high temperature and is
ionised so that it becomes an electrical conductor. This cutting procedure
uses the plasma to transfer the electric arc to the metal piece that is
melted by the heat and hence separated. The torch uses compressed
air form a single source, for both the plasma gas and the cooling and
protection gas.
HF strike
This type of strike is normally used on models with currents of over 50A.
Cycle start is determined by a high frequency/high voltage ("HF") arc that
is used to strike a pilot arc between the electrode (-ve polarity) and the
torch nozzle (+ve polarity). When the torch is brought close to the piece
to be cut, which is connected to the (+) polarity of the power source, the
pilot arc is transferred to set up a plasma arc between the electrode (-) and
the piece itself (the cutting arc): The pilot arc and HF strike are disabled
as soon as the plasma arc is established between the electrode and the
piece.
Pilot arc hold time is set in the factory at 2 s; if there is no arc transfer
within this time the cycle is automatically stopped, apart from the
MAKING THE FOLLOWING
continuance of cooling air.
To re-start the cycle it is necessary to release the torch button and then
press it again.
Shorting strike
This type of strike is normally used on models with currents of less than
50A.
Cycle start is determined by movement of the electrode inside the torch
nozzle, which is used to strike a pilot arc between the electrode (-ve
polarity) and the nozzle itself (+ve polarity).
When the torch is brought close to the piece to be cut, which is connected
to the (+) polarity of the power source, the pilot arc is transferred to set
up a plasma arc between the electrode (-) and the piece itself (the cutting
arc):
The pilot arc is disabled as soon as the plasma arc is established between
the electrode and the piece.
Pilot arc hold time is set in the factory at 2 s; if there is no arc transfer
within this time the cycle is automatically stopped, apart from the
continuance of cooling air.
To re-start the cycle it is necessary to release the torch button and then
press it again.
Preliminary operations.
Before starting cutting operations, make sure the consumable parts have
been fitted correctly by inspecting the head of the torch, as described in
the chapter on "TORCH MAINTENANCE".
- Switch on the power source and set the cutting current (FIG. C-1),
basing it on the thickness and type of the metal that is to be cut. TAB.
3 shows the cutting rate for various thicknesses of aluminium, iron and
steel.
- Press and release the torch button so that there is an outflow of air (
≥30 seconds of post-air).
- During this period, adjust the air pressure until the reading on the
pressure gauge corresponds to the required value in "bar" for the
particular torch being used (TAB. 2).
- Operate the air button so that the air flows out of the torch.
- Adjust the knob: pull upwards to release it and turn it to adjust the
pressure to the value given in the TECHNICAL INFORMATION ABOUT
THE TORCH.
- When the required reading (bar) is shown on the pressure gauge, press
the knob to lock the pressure at the adjusted value.
- Allow the last air to flow out naturally in order to facilitate removal of
any condensation that may have formed inside the torch.
Important:
- Contact cut (with torch nozzle in contact with piece being cut): this
can be applied with a max current of 40-50A (higher current values will
immediately destroy the nozzle-electrode-nozzle holder).
- Space cutting (with a spacer mounted on the torch, FIG. I): this can be
applied for currents of over 35A;
- Extended nozzle and electrode: this can be applied where provided for.
Cutting operations (FIG. L).
- Bring the torch nozzle close to the edge of the piece (at about 2 mm),
press the torch button; after about 1 second (pre-air) the pilot arc will
strike.
- If the distance is right the pilot arc will immediately transfer to the
piece, causing the cutting arc to strike.
- Move the torch at a constant rate over the surface of the piece along
the ideal cutting line.
- Adjust the cutting rate according to the thickness and the selected
current, making sure that the arc comes out of the lower surface of the
piece at an inclination of 5-10° to the vertical in the opposite direction
to the cutting direction.
- If the torch and piece are too far apart or if there is no material (end of
cut) the arc will immediately be cut off.
- It is always possible to break the (cutting or pilot) arc by releasing the
torch button.
Drilling (FIG. M)
When this operation is necessary, or to start cutting in the centre of the
piece, strike the arc with an inclined torch and bring it gradually to a
vertical position.
- This procedure will stop arc returns or melted particles from damaging
the nozzle hole and causing rapid wear.
- It is possible to drill pieces directly when their thickness is below 25%
of the maximum allowed range.
- 8 -