[attachment=11444]
Introduction:
Welding Processes:
Welding is the most economical and efficient way to join metals permanently. Welding is used to join all of the commercial metals and to join metals of different types and strengths.
A weld is produced either by heating the materials to the welding temperature with or without the application of pressure alone with or without the use of filler metal. There are different kinds of welding processes who all use different sources of heat, for instance arc welding which uses an electric arc as a heat source. Another commonly used welding process is spot welding (resistance welding).
This is the age modern technology any thing we want to weld , may be done by manually, but modern process have done these miraculously by adopting the technology of 21st century such as robot welding. Robot welding means welding that is performed and controlled by robotic equipment
A robot is a mechanical or virtual, artificial agent. It is usually a system, which, by its appearance or movements, conveys a sense that it has intent or agency of its own. The word robot can refer to both physical robots and virtual software agents, but the latter are usually referred to as bots to differentiate
While there is still discussion about which machines qualify as robots, a typical robot will have several, though not necessarily all of the following properties:
• is not 'natural' i.e. artificially created
• can sense its environment, and manipulate or interact with things in it
• has some ability to make choices based on the environment, often using automatic control or a preprogrammed sequence
• is programmable
• moves with one or more axes of rotation or translation
• makes dexterous coordinated movements
• appears to have intent or agency
Basics of robot welding:
Rectilinear robots move in line in any of three axes (X, Y, and Z). In addition to linear movement of the robot along axes there is a wrist attached to the robot to allow rotational movement. This creates a robotic working zone that is box shaped.
Articulating robots utilize arms and rotating joints. These robots move like a human arm with a revolving wrist at the end. This creates an irregularly shaped robotic working zone known as the work arc.
There are many factors that need to be considered when setting up a robotic welding facility. Robotic welding needs to be engineered differently than manual welding. Some of the considerations for a robotic welding facility are listed below:
The selected welding programme include start / stop, gas pre flushing , electrode feed and nozzle flushing. Robots have been used about 15 years to weld complete automotive body assembly and sub assembly components. In general equipment for automatic arc welding is designed differently from that used for manual arc welding. Automatic arc welding normally involves high duty cycles, and the welding equipment must able to operate under those conditions. In additions , the equipment components must have the necessary features and controls to interface with the control system
The number of items of any one type to be welded must be high enough to justify automating the process. If the joints are to be welded on a work piece are few , straight and easily accessible , a rack automatic gas metal gas welding (GMAW) gun or gas tungsten arc welding (GTAW) torch may be suitable for key welds.
An automatics gun also can be used in a fixed position or on a curved track for a curved or circular weld such as joining two pieces of pipes or welding a flat base to a cylindrical shape—a task in which a work piece can be rotated past the gun. If parts are normally need adjustment to fit together correctly , or if joints are to be welded are too wide or different positions from piece to piece , automating the procedure will be difficult or impossible.
The tabletop size robot is used to maximum effect- welding work piece is one side of a revolving jig . Each side of jig also can be revolved to allow access to both sides of work piece.
Robots work well for repetitive tasks on similar pieces that involve welds in more than one axis or where access to the piece is difficult. Welding robots are used in two ways in manufacturing – as elements in production line and as stand-alone units for batch production. Few companies move from all manual welding to a completely automated production line , so many people introduce robotic welding with a stand alone cell
At fabrication or welding trade shows, a variety of welding robots can be seen performing complex maneuvers and elegant pirouettes similar to a troupes ballet dancers. These displays are designed to demonstrate the speed and flexibility of today’s generation of robots. The fact is , dance moves aside, today’s robots can handle a wide range of welding applications.
Types of welding that robots can perform:
Automatic welding:
An autonomous mobile robot system with a visual sensor for automatic welding was developed. Algorithm for recognition of welding line and automatic seam-tracking was constructed. The robot has a movable arm of which position is controlled on cylindrical coordinates and two driving wheels which are equipped at both sides of the vehicle body. The CCD camera is equipped on the movable arm and detects welding line from upper side of base materials. The constructed system can recognize welding line with a visual sensor robustly and track welding line with enough precision and speed as basic performance of welding robot. Consequently, it was confirmed that the system has enough availability and effectiveness to automatic welding. The following welding operations that can be performed by robots are as follows:
1) Arc welding
2) MIG welding
3) TIG welding
4) Spot welding
5) Stick welding
Arc Welding - A Popular Method
Representing 20% of all robotic applications, arc welding is one of the most common functions in industry today. During this process, electricity jumps from an electrode guided through the seam, to the metal product. This electric arc generates intense heat, enough to melt the metal at the joint. Sometimes the electron is simply a conductor that guides the arc. Other times the rod or wire is composed to become part of the weld
Creating a Fusion Bond
The resulting fusion bond is a seamless addition to the product. The mix of metals has the same strength as the original metals. This is one of the reasons arc welding is preferred to soldering or brazing. Non-fusion methods can be weaker because they fail to duplicate the mechanical and physical properties of the metals.
Automated Arc Welding Benefits Include:
Consistency of quality welds
Repeatability
Lowered production costs
Fewer scrapped parts
Increase your return on investment (ROI)
Fewer injuries from weld splatter or fumes
Speed - faster part cycle time
MIG Welding
Gas Metal Arc Welding (GMAW) is frequently referred to as MIG welding. MIG welding is a commonly used high deposition rate welding process. Wire is continuously fed from a spool. MIG welding is therefore referred to as a semiautomatic welding process.
MIG Welding Benefits
All position capability. Higher deposition rates that SMAW..
MIG Welding Shielding Gas
The shielding gas forms the arc plasma, stabilizes the arc on the metal being welded, shields the arc and molten weld pool, and allows smooth transfer of metal from the weld wire pool. There are three primary metal transfer modes: Spray transfer, Globular transfer, and Short circuiting transfer. The primary shielding gasses used are: Argon, Argon-1 to 5% Oxygen, Argon-3 to 25% CO2, and Argon/Helium. CO2 is also used in its pure form in some mig welding processed. However, in some applications the presence of CO2 in the shielding gas may adversely affect the mechanical properties of the weld.
Common MIG Welding Concerns
Weld discontinuities. Undercutting. Excessive melt-through. Incomplete fusion. Incomplete joint penetration. Porosity. Weld metal cracks
Arc Welding Process: Gas Tungsten
Gas Tungsten Arc Welding (GTAW) is frequently referred to as TIG welding. TIG welding is a commonly used high quality welding process. TIG welding has become a popular choice of welding processes when high quality, precision welding is required. In TIG welding an arc is formed between a non-consumable tungsten electrode and the metal being welded. Gas is fed through the torch to shield the electrode and molten weld pool. If filler wire is used, it is added to the weld pool separately.
TIG Welding Benefits
Superior quality welds. Welds can be made with or without filler metal. Precise control of welding variables (heat). Free of spatter. Low distortion
Shielding Gases
Uses the following shielding gases: Argon. Argon + Hydrogen. Argon/Helium. Helium is generally added to increase heat input (increasing welding speed or weld penetration). Hydrogen will result in cleaner looking welds and also increase heat input, however, Hydrogen may promote porosity or hydrogen cracking