4。It is immune to the arc process like spatter and can withstand radiated heat。

5。The system is unaffected by ambient lighting conditions and can track all weldable materials。

6。The system offers true 3D laser measurements of joint geometry dimensions。

7。The high-speed digital laser sensor makes fast and reliable joint recognition possible。

8。The system is suitable for high-speed welding pro- cesses like tandem gas metal arc welding and laser hybrid welding。

9。The system has a direct interface with most brands of robot by advanced communication protocol on a serial or Ethernet link。

10。A large joint library is included, which allows almost any weld seam on any weldable material to be tracked and measured geometrically。

11。The adaptive welding module can adjust for joint geometry variability for optimization of the size of the weld and thus elimination of defects and reduced over-weld。

Figure 9 shows robotic arc  welding  in  conjunction with the Power-Trac system for seam finding and track- ing (Servo Robot Inc 2013b)。

Laser Pilot (Meta Vision Systems Ltd。) This sensor featuring laser vision enables  sensing  of the actual parts to be welded for seam finding and seam tracking。 It corrects part positioning errors as well as errors due to thermal distortion  during  the  welding  process。 Some of the variants of the Laser Pilot system are de- scribed below:

●Laser Pilot MTF

Laser Pilot MTF is a seam finder and can be used in robotic welding applications which involve a series

of short welds, as commonly found in the automotive industry, that do not require real-time tracking, although correct placement of the weld torch in the beginning of the weld is needed。 MTF uses a standard interface for communication to the robot controller。

●Laser Pilot MTR

Laser Pilot MTR is a seam tracker and available with interfacing with various leading robot manufacturers’ products。 In addition to the seam-finding function, it can track seams in real time while  welding

(Meta Vision  Systems  Ltd 2006)。

Circular Scanning System Weld-Sensor  The   Circular

  Scanning   System   (CSS)   Weld-Sensor   (Oxford Sensor

Technology Ltd。) consists of a low-power laser diode that projects a laser beam through an off-axis lens onto the surface being analyzed, as shown in Fig。 10。 A linear CCD detector views the spot through the same off-axis lens。 The distance between the CSS Weld-Sensor and the surface to be measured is calculated based on a triangulation method。 An inbuilt motor rotates  the off-axis lens, causing the laser spot to be rotated and forming a conical scan (Mortimer 2006)。 The circular scanning technology enables  measurement  of 3D shaped corners in a single measurement and has the advantage of an increased detection ratio compared to other sensors (Bergkvist 2004)。 The CSS Weld-Sensor can  also be  used  with highly reflective materials  such as  aluminum  (Mortimer 2006)。

A manufacturing system designed by Thyssen-Krupp- Drauz-Nothelfer (TKDN) with integrated  CSS  Weld- Sensor in conjunction with a MIG welding torch and an ABB 2400–16 robot was used in welding of the aluminum C-pillar to the aluminum roof section of Jaguar’s sports car XK, as shown in Fig。 11。 This welding has importance as regards both esthetics and strength because  the  sec- tion is at eye level and there should not be any visible external joints and  defects。  The  sensor  reads  the seam’s position, width, depth, and  orientation。  There are some six or eight measurements involved in the welding process and  each measurement  takes less   than