Weldclass Weldforce 155M, Руководство по эксплуатации

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Weldforce 155
M &
175
MST
© Weldclass 2020 | E.&O.E. 33
10 GENERAL GUIDE TO WELDING
10.1 Duty Cycle Rating
Weldforce welding machines are fitted with thermal overload protection which means the machine will cut
out when it reaches a certain temperature, to prevent damage to components. The machine will then re-
start when it returns to a safe temperature.
Duty cycle is a measure of the percentage of time a machine will operate within a certain time period at a
given amperage. For example a duty cycle of 160A @ 25% means that a machine will operate at 160A for 2
½ minutes in a 10 minute time period. The machine will have to rest for the remaining 7 ½ minutes to
enable it to cool down.
The international standard for duty cycle rating is based on an ambient air temperature of 40°C with 50%
humidity, over a 10 minute period. In an environment with temperatures exceeding 40°C, the duty cycle
will be less than stated. In ambient temperature less than 40°C, duty cycle performance will be higher. There
are numerous other factors that can influence actual duty cycle performance.
10.2 Choosing a Welding Process – MIG, Stick or TIG?
10.2.1 The Stick (MMA) Process
10.2.1.1 Description
The acronym MMA (or MMAW) stands for Manual Metal Arc Welding. ‘Manual’ refers to the fact
that the MMA process requires the operator to apply filler metal (in contrast to MIG ‘semi-automatic’
welding where the machine feeds the filler metal into the weld). ‘Metal’ refers to the fact that the
filler metal itself (the stick electrode) is used to conduct the welding current to the job. MMA welding
is commonly known as ‘stick-electrode’ or ‘arc’ welding.
10.2.1.2 Process
The MMA process involves the electrode being touched on the job to ignite the arc. The electrode is
held in the electrode holder and must be continually replaced as it is consumed. The electrode
consists of a metal core, which is the filler metal, covered by a flux coating which shields the weld
and prevents it from oxidising. During welding the flux forms into a slag covering the weld which is
chipped off after the weld has formed.
10.2.1.3 Advantages
MMA welding offers several advantages over alternative welding processes. Primarily it has a greater
capacity than MIG welding, or in other words it can weld heavier materials with the same amperage
output. For this reason small, portable inverter welders like the Weldforce machines, have the
capacity to weld with up to 3.2mm or 4mm electrodes making it suitable for a vast range of
applications without the complication of shielding gas or wire feeding. Moreover, MMA welding is
typically more ‘forgiving’ than MIG or TIG when welding rusty or dirty materials (which makes it ideal
for maintenance applications).
10.2.1.4 Limitations
Traditionally, welding thin materials whilst avoiding “blow-through” can be tricky with the MMA
process. This being said, however, welding thin materials with a Weldforce machine will be
noticeably easier because the arc is so stable and the output can be very finely adjusted down to
very low amps.
10.2.1.5 Materials
MMA welding can be used with a wide variety of electrodes including general purpose, low
hydrogen, stainless steel, iron powder, hard facing & cast iron just to name a few.