02-11-2012, 11:03 AM
Welding Robot
Welding Robot.doc (Size: 734.5 KB / Downloads: 122)
Welding.ppt (Size: 346 KB / Downloads: 411)
INTRODUCTION
Welding technology has obtained access virtually to every branch of manufacturing; to name a few bridges, ships, rail road equipments, building constructions, boilers, pressure vessels, pipe lines, automobiles, aircrafts, launch vehicles, and nuclear power plants. Especially in India, welding technology needs constant upgrading, particularly in field of industrial and power generation boilers, high voltage generation equipment and transformers and in nuclear aero-space industry.
Computers have already entered the field of welding and the situation today is that the welding engineer who has little or no computer skills will soon be hard-pressed to meet the welding challenges of our technological times. In order for the computer solution to be implemented, educational institutions cannot escape their share of responsibilities.
INTRODUCTION TO AUTOMATION AND ROBOTICS
Automation and robotics are two closely related technologies. In an industrial context, we can define automation as a technology that is concerned with the use of mechanical, electronics and computer-based systems in the operation and control of production. Examples of this technology include transfer lines, mechanized assembly machines, feed back control systems, numerically controlled machine tools, and robots. Accordingly, robotics is a form of industrial automation.
There are three broad classes of industrial automation: fixed automaton, programmable automation, and flexible automation. Fixed automation is used when the volume of production is very high and it is therefore appropriate to design specialized equipment to process the product very efficiently and at high production rates. A good example of fixed automation can be found in the automobile industry, where highly integrated transfer lines consisting of several dozen work stations are used to perform machining operations on engine and transmission components. The economics of fixed automation are such that the cost of the special equipment can be divided over a large number of units, and resulting unit cost are low relative to alternative methods of production. The risk encountered with fixed automation is this; since the initial investment cost is high, if the volume of production turns out to be lower than anticipated, then the unit costs become greater than anticipated. Another problem in fixed automation is that the equipment is specially designed to produce the one product, and after that products life cycle is finished, the equipment is likely to become obsolete. For products with short life cycle, the use of fixed automation represents a big gamble.
INTRODUCTION TO WELDING
Welding is a process of joining different materials. The large bulk of materials that are welded are metals and their alloys although welding is also applied to the joining of other materials such as thermoplastics. Welding joins different metals or alloys with help of a number of processes in which heat is supplied either electrically or by means of a gas torch.
SPOT WELDING
As he term suggests, spot welding is a process in which two sheet metal parts are fused together at localized points by passing a large electric current using two copper electrodes, hence producing the weld. For relatively small parts a spot welding machine is used in which the parts are inserted between the pair of electrodes that are maintained in a fixed position. Where as for larger works such as in automobile bodies a portable welding gun is used which consists of a pair of electrodes and a frame to open and close the electrodes.
CONTINUOUS ARC WELDING
Arc welding is a continuous process as opposed to spot welding which might be called a discontinuous process. Continuous arc welding is used to make long welding joints in which an air tight seal is often required between the two pieces of metals being joined. The process uses an electrode in the form of a rod or a wire of metal to supply the high electric current needed for establishing the arc. Currents are typically 100 to 300A at voltages of 10 to 30GV. The arc between the welding rod and the metal parts to be joined produces temperatures that are sufficiently high to form a pool of molten metal to fuse the two pieces together. The electrode can also be used to contribute to the molten pool, depending on the type of welding process.
WHY CONTINUOUS ROBOTIC ARC WELDING?
Arc welding is performed by skilled workers who are assisted by a person called fitter. The purpose of the fitter is to organize the work and fixture the parts of the welder. The working condition of the welder is typically unpleasant and hazardous. The arc from the welding process emits ultra-violet radiations which is injurious to human vision. As a result welders are required to wear eye protection in the form of a welding helmet with a dark window. The dark window filters out the dangerous, but it so dark that the welder is virtually blind while wearing the helmet except when the arc is struck. Other aspects of the process are also hazardous. The high temperature created in arc welding and the resulting molten metals are inherently dangerous. The high electric current used to create the arc is also unsafe. Sparks and smoke are generated during the process are a potential threat to operators. Because of the hazards for human workers in continuous arc welding, it is logical to consider industrial robots for the purpose.
BENEFITS OF ROBOT ARC WELDING
HIGHER PRODUCTIVITY
Factors that contribute to the increased rate when robots used in batch production is the elimination of fatigue factor. Robots do not experience fatigue in the sense that human workers do. A robot can continue to operate in the entire shift with need of periodic rest breaks.
IMPROVED SAFTEY AND QUALITY-OF-WORK LIFE
Improved safety and quality-of-work environment result from removing the human operator from an uncomfortable, fatiguing and potentially dangerous work situation.
GREATER QUALITY OF PRODUCT
Greater product quality in robot arc welding results from the capability of the robot to perform the welding cycle with accuracy and repeatability than its human counterpart. This translates into a more consistent welding seam; one that is free of the start-and-stop builds up of filler metal in the seam that is the characteristic of many welds accomplished by human welders.
FEATURES OF ARC WELDING ROBOTS
An industrial robot that performs welding must possess certain features and capabilities. Some of the technical considerations in arc welding applications are discussed in the following.
WORK VOLUME AND DEGREES OF FREEDOM
The robot’s work volume must be large enough for the size of the parts to be welded. A sufficient allowance must be made for the manipulation of the welding torch. Five or six degrees of freedom are generally required for arc welding robots. The number is influenced by the characteristics of the welding job and motion capabilities of the parts manipulator. If the parts manipulator has two degrees of freedom, this tends to reduce the requirement on the number of degrees of freedom possessed by the robot.
INTERFACE WITH OTHER SYSTEM
The robot must be provided with sufficient input/output and control capabilities to work with other equipments in the cell. These other pieces of equipments are automobile fixturing units, conveyors, and parts of positioners. The cell controller unit must co-ordinate the path and path of robot with operation of parts manipulator and the welding parameters such as wire feed rate and power level.
PROGRAMMING
Programming the robot for continuous arc welding must be considered carefully. To facilitate the input of the program for welding paths with irregular shapes; it is convenient to use the walk through method in which the robot wrist is physically moved through its motion path. For straight welding paths, the robot should possess the capability for linear interpolation between two points in the space. This permits the programmer to define the beginning and points of the path the robot is capable of computing the straight trajectory between the points.
Welding Robot.doc (Size: 734.5 KB / Downloads: 122)
Welding.ppt (Size: 346 KB / Downloads: 411)
INTRODUCTION
Welding technology has obtained access virtually to every branch of manufacturing; to name a few bridges, ships, rail road equipments, building constructions, boilers, pressure vessels, pipe lines, automobiles, aircrafts, launch vehicles, and nuclear power plants. Especially in India, welding technology needs constant upgrading, particularly in field of industrial and power generation boilers, high voltage generation equipment and transformers and in nuclear aero-space industry.
Computers have already entered the field of welding and the situation today is that the welding engineer who has little or no computer skills will soon be hard-pressed to meet the welding challenges of our technological times. In order for the computer solution to be implemented, educational institutions cannot escape their share of responsibilities.
INTRODUCTION TO AUTOMATION AND ROBOTICS
Automation and robotics are two closely related technologies. In an industrial context, we can define automation as a technology that is concerned with the use of mechanical, electronics and computer-based systems in the operation and control of production. Examples of this technology include transfer lines, mechanized assembly machines, feed back control systems, numerically controlled machine tools, and robots. Accordingly, robotics is a form of industrial automation.
There are three broad classes of industrial automation: fixed automaton, programmable automation, and flexible automation. Fixed automation is used when the volume of production is very high and it is therefore appropriate to design specialized equipment to process the product very efficiently and at high production rates. A good example of fixed automation can be found in the automobile industry, where highly integrated transfer lines consisting of several dozen work stations are used to perform machining operations on engine and transmission components. The economics of fixed automation are such that the cost of the special equipment can be divided over a large number of units, and resulting unit cost are low relative to alternative methods of production. The risk encountered with fixed automation is this; since the initial investment cost is high, if the volume of production turns out to be lower than anticipated, then the unit costs become greater than anticipated. Another problem in fixed automation is that the equipment is specially designed to produce the one product, and after that products life cycle is finished, the equipment is likely to become obsolete. For products with short life cycle, the use of fixed automation represents a big gamble.
INTRODUCTION TO WELDING
Welding is a process of joining different materials. The large bulk of materials that are welded are metals and their alloys although welding is also applied to the joining of other materials such as thermoplastics. Welding joins different metals or alloys with help of a number of processes in which heat is supplied either electrically or by means of a gas torch.
SPOT WELDING
As he term suggests, spot welding is a process in which two sheet metal parts are fused together at localized points by passing a large electric current using two copper electrodes, hence producing the weld. For relatively small parts a spot welding machine is used in which the parts are inserted between the pair of electrodes that are maintained in a fixed position. Where as for larger works such as in automobile bodies a portable welding gun is used which consists of a pair of electrodes and a frame to open and close the electrodes.
CONTINUOUS ARC WELDING
Arc welding is a continuous process as opposed to spot welding which might be called a discontinuous process. Continuous arc welding is used to make long welding joints in which an air tight seal is often required between the two pieces of metals being joined. The process uses an electrode in the form of a rod or a wire of metal to supply the high electric current needed for establishing the arc. Currents are typically 100 to 300A at voltages of 10 to 30GV. The arc between the welding rod and the metal parts to be joined produces temperatures that are sufficiently high to form a pool of molten metal to fuse the two pieces together. The electrode can also be used to contribute to the molten pool, depending on the type of welding process.
WHY CONTINUOUS ROBOTIC ARC WELDING?
Arc welding is performed by skilled workers who are assisted by a person called fitter. The purpose of the fitter is to organize the work and fixture the parts of the welder. The working condition of the welder is typically unpleasant and hazardous. The arc from the welding process emits ultra-violet radiations which is injurious to human vision. As a result welders are required to wear eye protection in the form of a welding helmet with a dark window. The dark window filters out the dangerous, but it so dark that the welder is virtually blind while wearing the helmet except when the arc is struck. Other aspects of the process are also hazardous. The high temperature created in arc welding and the resulting molten metals are inherently dangerous. The high electric current used to create the arc is also unsafe. Sparks and smoke are generated during the process are a potential threat to operators. Because of the hazards for human workers in continuous arc welding, it is logical to consider industrial robots for the purpose.
BENEFITS OF ROBOT ARC WELDING
HIGHER PRODUCTIVITY
Factors that contribute to the increased rate when robots used in batch production is the elimination of fatigue factor. Robots do not experience fatigue in the sense that human workers do. A robot can continue to operate in the entire shift with need of periodic rest breaks.
IMPROVED SAFTEY AND QUALITY-OF-WORK LIFE
Improved safety and quality-of-work environment result from removing the human operator from an uncomfortable, fatiguing and potentially dangerous work situation.
GREATER QUALITY OF PRODUCT
Greater product quality in robot arc welding results from the capability of the robot to perform the welding cycle with accuracy and repeatability than its human counterpart. This translates into a more consistent welding seam; one that is free of the start-and-stop builds up of filler metal in the seam that is the characteristic of many welds accomplished by human welders.
FEATURES OF ARC WELDING ROBOTS
An industrial robot that performs welding must possess certain features and capabilities. Some of the technical considerations in arc welding applications are discussed in the following.
WORK VOLUME AND DEGREES OF FREEDOM
The robot’s work volume must be large enough for the size of the parts to be welded. A sufficient allowance must be made for the manipulation of the welding torch. Five or six degrees of freedom are generally required for arc welding robots. The number is influenced by the characteristics of the welding job and motion capabilities of the parts manipulator. If the parts manipulator has two degrees of freedom, this tends to reduce the requirement on the number of degrees of freedom possessed by the robot.
INTERFACE WITH OTHER SYSTEM
The robot must be provided with sufficient input/output and control capabilities to work with other equipments in the cell. These other pieces of equipments are automobile fixturing units, conveyors, and parts of positioners. The cell controller unit must co-ordinate the path and path of robot with operation of parts manipulator and the welding parameters such as wire feed rate and power level.
PROGRAMMING
Programming the robot for continuous arc welding must be considered carefully. To facilitate the input of the program for welding paths with irregular shapes; it is convenient to use the walk through method in which the robot wrist is physically moved through its motion path. For straight welding paths, the robot should possess the capability for linear interpolation between two points in the space. This permits the programmer to define the beginning and points of the path the robot is capable of computing the straight trajectory between the points.