Page 87 - Welding Robots Technology, System Issues, and Applications

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Sensors for Welding Robots

3.1 Introduction

The demand for better control and sensing in welding has increased with
automation and welding processes involving new and advanced materials. This
requires precise control of the welding process to produce the desired weld with
respect to productivity and quality. Consequently, there is a need for different
technologies to control precisely the process with respect to the different welding
operating parameters. In doing so, sensors play a crucial role as the major source of
input to the control system that manage and control the behavior and output of the
welding system. Here, the term “sensor” is used for devices that measure
observable parameters related to the welding process which is used to control the
process in accordance with defined specifications.

In general, most robotized welding processes that produce a continuous weld are
based on the MIG/MAG process, or GMAW (Gas Metal Arc Welding). Within this
application field, the use of sensors has been modest. However, the development
and introduction of new welding processes like high speed welding, laser welding,
etc., emphasize the importance of accurate control of the process. The development
of new products also makes use of new materials with possibilities to decrease
thicknesses. A result of this is a need to be able to work with tighter tolerances.
Thus, the need is increasing for sensors that can meet the requirements from new
processes and product specifications and is in many cases a necessity.

The main task of the sensors is to provide the control system with information to
generate proper actions to produce a result that corresponds with defined
specifications. In welding this is not as easy as we might think. From a welding
process perspective, the process is performed mainly by two subsystems; the
welding equipment and the robot. The welding equipment includes the welding
power source and the devices that deliver the energy from the welding power
source, like the wire feed system, conduit, welding torch and so on. The robot

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