26-11-2012, 05:02 PM
A SEMINAR REPORT ON ROBOT WELDING TECHNOLOGY
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ABSTRACT
Welding is manufacturing process in which to pieces of metal are joined by usually by heating them until molten and fused and by applying pressure. Welding operations performed by robot vastly. Welding of two types on e is arc welding and another spot welding.In arc welding two metals are joined along its continuous path. An electric arc is generated there.Spot welding is the largest application for industrial robots in US, accounting for about for 35 percent of installed robots. Welding robots typically use point-to-point programming to maneuver a welding gun. Robots weld more consistently faster and with higher quality than humans
ROBOT WELDING
When should robots be used for welding?
A welding process that contains repetitive tasks on similar pieces might be suitable for automation. The number of items of any type to be welded determines whether automating a process or not. If parts normally need adjustment to fit together correctly, or if joints to be welded are too wide or in different positions from piece to piece, automating the procedure will be difficult or impossible. Robots work well for repetitive tasks or similar pieces that involve welds in more than one axis or where access to the pieces is difficult.
Why robot welding
The most prominent advantages of automated welding are precision and productivity. Robot welding improves weld repeatability. Once programmed correctly, robots will give precisely the same welds every time on workpieces of the same dimensions and specifications.
Automating the torch motions decreases the error potential which means decreased scrap and rework. With robot welding you can also get an increased output. Not only does a robot work faster, the fact that a fully equipped and optimized robot cell can run for 24 hours a day, 365 days a year without breaks makes it more efficient than a manual weld cell. Another benefit of automated welding is the reduced labor costs. Robotic welding also reduces risk by moving the human welder/operator away from hazardous fumes and molten metal close to the welding arc.
What welding processes are suitable for robot welding?
Most production welding processes can be used in automated applications. The most popular, used in perhaps 80 percent of applications, is the solid wire GMAW process. This process is best for most high production situations because no postweld cleanup is required.
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).
Welding is considered to be the most complex of all manufacturing technologies. In order to transform welding from a manual operation to an automated production process, it is necessary to understand the scientific principles involved.
ROBOT ARC WELDING
Robot welding means welding that is performed and controlled by robotic equipment. 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 be able to operate under those conditions. In addition, the equipment components must
have the necessary features and controls to interface with the main control system.
A special kind of electrical power is required to make an arc weld. A welding machine, also known as a power source, provides the special power. All arc-welding processes use an arc welding gun or torch to transmit welding current from a welding cable to the electrode. They also provide for shielding the weld area from the atmosphere.
The nozzle of the torch is close to the arc and will gradually pick up spatter. A torch cleaner (normally automatic) is often used in robot arc welding systems to remove the spatter. All of the continuous electrode wire arc processes require an electrode feeder to feed the consumable electrode wire into the arc.
Welding fixtures and workpiece manipulators hold and position parts to ensure precise welding by the robot. The productivity of the robot-welding cell is speeded up by having an automatically rotating or switching fixture, so that the operator can be fixing one set of parts while the robot is welding another.
ARC WELDING ROBOT
During the short time that industrial welding robots have been in use, the jointed arm or revolute type has become by far the most popular. For welding it
has almost entirely replaced the other types except for the Cartesian, see (robot kinematics), which is used for very large and very small robots. The reason for the popularity of the jointed arm type is that it allows the welding torch to be manipulated in almost the same fashion as a human being would manipulate it. The torch angle and travel angle can be changed to make good quality welds in all positions. Jointed arm robots also allow the arc to weld in areas that are difficult to reach. Even so, a robot cannot provide the same manipulative motion as a human being, although it can come extremely close. In addition, jointed arm robots are the most compact and provide the largest work envelope relative to their size. Usually arc-welding robots have five or six free programmable arms or axes.