SEAM TRACKING SYSTEM FOR ROBOTIC ARC WELDING
JUSTIN JOSE
7 MECHANICAL
ROLL NO: 24

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INTRODUCTION
TYPE OF SENSORS
1.THRU ARC SEAM TRACKING(TAST)
2.ARC VOLTAGE CONTROL
3.LASER VISION SYSTEM
4.TOUCH SENSING

TAST
This method uses welding arc as sensor
Arc length is inversely proportional to current
Use with constant voltage arc welding
Lateral location of seam is determined by using wave function of robot.
A valley in current indicates torch is over the seam .
peak in signal represents torch is at either end of seam

TAST
Advantages of TAST
1. Low cost method.
2. No external sensor is required.
3. No additional cyclic time.
4. Minimum lap thickness(2mm).
5. Adaptive capabilities.
6. Suitable with GMAW PULSED GMAW Sub arc .

Disadvantages of TAST
1.Not a seam finder.
2.maintanance is high.
3.difficult to program.
4.noise interference.
5.Change in welding process affect considerably
AVC
Used for constant current arc welding.
Voltage is directly proportional to weld current.
Mainly used for vertical tracking
Can be used with GTAW PAW


Advantages of avc
Inexpensive method
No additional cyclic time
No sensor requirement
Low maintenance requirement
Programming complexity low compared to TAST
Disadvantages of AVC
Increased lap thickness(4mm)
Not a seam finder
No adaptive capabilities
Complicated to setup and maintain
Laser based vision system
Uses laser to scan across weld joint
Camera is used to monitor the laser
Search the joint location before starting the weld
Gives information about weld joint mismatch gap etc.
Sensor is attached to weld torch
Laser vision system
The sensor head contains a CCD camera and either one or two laser diodes. The lasers act as a structured light source and project a stripe of laser light at a pre-set angle onto the work piece surface under the sensor. Sensors are available with varying field of view to accommodate a range of working distances, seam types and sizes. This allows the camera to view the stripe directly under the sensor in any situation. In front of the camera is an optical filter that allows the light from the lasers to pass through, but filters out nearly all other light, such as the welding arc. The sensor is therefore able to operate very close to the welding source.
3d circular scanning

Advantages
Flexibility in type and size of joint
Seam finder
Adaptive capabilities
Reduction in repair cost
No arc need to be established
Low thickness of gap and lap
Suits with most welding processes

Disadvantages
Very expensive
Affected by everyday harsh environment
Additional cyclic time
Works with only non reflective metals
Maintenance requirement high compared to touch sensing

Touch sensing
Welding electrode or a separate pointer senses the joint
Finds weld seam and adjusts the entire weld path before starting the arc
Finds gap in weld joint which requires change in weld schedule


Touch sensing
Uses welding electrode or a separate pointer to make electrical contact with part.

Advantages
Maintenance requirement is low of all types
All materials can be welded
Seam finder
Most welding processes
Low cost method
Programming complexity low of all types



Disadvantages

Dynamic seam tracking
Root pass memorization

conclusion