**3. Evolution and comparison of the techniques and methods used for measurement and estimation of the geometry of weld bead**

An analysis made in [7] about techniques and methods used for measurement and estimation of the geometry of the weld bead found publications and patents

#### *Welding - Modern Topics*

since 1971, but it is not until the 1980s that a greater interest in this subject was observed. Recently, in the last decade, the number of publications is increased. **Figure 20** shows this growing interest.

The technological development and cost reduction of sensors and the need for welding process control in an industrial environment (robotic welding) stimulated the number of scientific works about these topics.

An example is the development of infrared sensors that since the 1970s were available but in the 1980s were given classified contracts by the US Department of Defense to Honeywell and Texas Instruments to develop uncooled infrared sensor technology. In 1992, the US Government de-classified this technology for commercial products, allowing the sale of their devices to foreign countries, but kept close the manufacturing technologies. In the next decade, several countries developed uncooled imaging systems [25] with a drastic reduction of uncooled array cost.

**Figure 20.**

*Evolution of the number of publications about measurement and estimation of the weld bead geometry (adapted from [7]).*

**Variable**

**95**

**Costa/accuracyb**

**From welding power**

**source**

Welding voltage Welding current

Wire feed speed

Welding speed Welding angle

Orbital angle Contact tip-to-work

distance

Welding joint

dimensions

Weld bead width

Weld bead reinforcement

Weld bead penetration

*a*

*b*

*L—Low accuracy; M—medium*

*cThis method is used together with one or several video cameras.*

*dThis method is used alone or together with welding power source* 

**Table 1.** *Comparison*

 *between the most used methods to measure the variables of welding processes, considering*

*L—Low cost; M—medium*

 *cost; and H—high cost.*

 *accuracy; H—high accuracy.* *measurements*

 *(e.g., arc variables).*

 *the cost and accuracy of the method.*

 L/H

 L/M L/H

L/H

L/H

L/M

M/H

H/H

H/H

M/M M/M

H/H

 M/H M/M

 H/M

L/L

M/L

H/H

 M/H

 M/H

 L/H

 **of measuring**

 **method**

**From robotic**

**Laser distance**

**Laser**

**Structural**

**Pyrometerd**

**Thermographic**

**Acoustic**

**Weld pool**

**signald**

**oscillationc**

*Online Measurements in Welding Processes DOI: http://dx.doi.org/10.5772/intechopen.91771*

**camerad**

**scanner**

**lightc**

**sensor**

**system**

**Figure 21.** *Evolution of techniques used to measure the weld bead geometry [7].*

