Advanced Welding Processes: Technologies and Process Control

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Advanced welding processes
welding conditions. Programming and storage of welding parameters is made
even easier if microprocessor control systems are used as described above.
3.5.4 External computer control
Control of electronic power sources by means of an external micro-computer
has also been used. This has mainly been for research applications where a
wide range of process variables are under investigation, but many
microprocessor-controlled power sources now have the facility to communicate
with a host computer using standard serial communications protocols (RS232,
RS423, USB, CAN, etc). This allows welding parameters to be ‘downloaded’
to the equipment as well as facilitating remote control and monitoring. This
technique may also be used in production applications and the robotic system
being developed for remote-controlled repair welding of turbine runners is a
good example of this approach.
3.6 Practical implications of electronic power
regulation and control
The changes in the technology of welding power sources described above
have some significant practical implications: the power sources can be
manufactured using modern electronic assembly techniques and the dependence
of these designs on expensive raw materials, such as iron for transformer
cores and copper for the windings, is reduced. This should enable the
manufacturers of these more advanced power sources to offer them at costs
similar to those of conventional designs. These designs also offer the user the
following advantages:
∑ improved repeatability;
∑ increased ease of setting;
∑ enhanced process capabilities.
Improved repeatability has a direct impact on the quality of the welded joint
and the ability to maintain welding parameters within the range specified in
the welding procedure, and is likely to reduce the repair and rework costs
discussed in Chapter 2. The increased ease of setting should improve the
operating efficiency and reduce the risk of operator error. The enhanced
process capabilities result from the ability to change various process output
parameters of an electronic power supply during welding. The output
characteristics are not predetermined and may be varied (within the limits of
the transformer output) to produce beneficial effects. For example, in the
case of GMAW, constant-current output characteristics may be used for
improved control and the output may be modified dynamically to provide
self-adjustment. In MMA welding systems, the current may be increased