TPT November 2013

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November 2013 123
Polysoude SAS Article
Polysoude SAS – France
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Use of a welding robot is also recommended for anything
other than circular trajectories or where the industrial company
wishes to acquire a more versatile tool.
There are no particular considerations for solutions involving
torches intended for applications up to 45mm. A retractable
nozzle torch offers a multipurpose solution provided that
electrode changing can be accepted as a non-automatable
operation.
For heavy wall thicknesses, torch weights and dimensions
must be integrated and robots compatible with wrist loads of
10 to 50kg selected. The notion of trajectory remains linked to
the profile of the torches which limits movements and implies
studying torch positioning along the usual three axes.
The use of a Narrow Gap torch renders the notion of
automated preventive maintenance, such as electrode
changing, somewhat illusory.
The other approaches are specific to robot use and are to be
addressed according to workpiece dimensions and the level
of automation (gantry, multi-robot station, seam tracking, etc).
Narrow Gap TIG welding is no longer a solution for exceptional
circumstances. It is important to consider it whenever the
thickness to be welded exceeds 30mm.
An initial analysis is imperative to ascertain the potential
benefit, verify the absence of notable contraindications and
above all to choose the methodology and equipment best
suited to the context.
There are a multitude of solutions with a significant level of
industrial maturity confirmed by numerous concrete examples.
Figure 12: Narrow Gap welding with robot
The difficulties involved in implementing the welding
procedures vary according to the chosen technique. The
temptation to take a simplistic approach and skip a case-by-
case assessment must, however, be avoided as there is no
universal solution.
Moreover, in terms of tools, the entire 30 to 300mm thickness
range is covered with numerous variants and adaptation
possibilities for special cases.
For the welding process, knowledge and mastery of TIG are
highly important and enable the technique to be popularised,
with recourse in the event of difficulties. From the point of
view of industrial companies, the implementation of a Narrow
Gap application calls for a structured approach with marked
steps. In parallel, corresponding approaches for machining
facilities, tracking and traceability of materials and inspection
techniques may need to be undertaken requiring validation
steps close to those used in welding.
All of these anticipatory measures are justified by the
prospect of substantial gains compared with the use of more
conventional techniques.