arc welding Method Not Allowed

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ROBOTICS ARCWELDING


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Introduction

Robotics Terminology1. Robot:

An electromechanical device with multipledegrees-of freedom (DOF) that is programmableto accomplish a variety of tasks.

2. Industrial robot:The Robotics IndustriesAssociation (RIA) defines robot in the followingway:

An industrial robot is a programmable,multi-functional manipulator designed tomove materials, parts, tools, or specialdevices through variable programmed

motions for the performance of a variety of


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Robotic Welding

The use of mechanized

programmable tools (robots), whichcompletely automate a weldingprocess by both performing the weldand handling the part.


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Automation of Welding

Automation of welding became possibleand practical with the acceptance ofcontinuous electrode wire arc weldingprocesses.

The advantage of automation weldingis: Consistency of quality welds Repeatability

Reduction of production costs

Fewer scrapped parts


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The robotic welding automation commonly

have five stations that is:

Arc Welding

Laser Welding

Spot Welding


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Automation of Welding

Automated welding systemconsists of:

1. Welding arc

2. Master controller

3. Arc motion device

4. Work motion device

5. Work holding fixture

6. Welding program

7. Consumables


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Some of the equipment of the robotic


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Robotic Welding Concept

A special kind of electrical power isrequired to make an arc weld.

The nozzle of the torch is close to thearc and will gradually pick up spatter.

A torch cleaner (normally automatic) isoften used to remove the spatter.

All of the continuous electrode wire arcprocesses require an electrode feederto feed the consumable electrode wire

into the arc.


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Robotic Welding Concept


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Arc Welding Robot

Arc welding robot 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.


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Other times the rod or wire iscomposed to become part of the weld.During the short time that industrialwelding robots have been in use, the

jointed arm or revolute type hasbecome by far the most popular.The reason for the popularity of thejointed arm type is that it allows thewelding torch to be manipulated in

almost the same fashion as a humanbeing would manipulate it. The torchangle and travel angle can be changedto make good quality welds in allpositions. Jointed arm robots also allow

the arc to weld in areas that are difficult


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Robot Manipulator

The robot manipulator can be divided into twosections, each with a different function: Arm and Body - The arm and body of a robot

are used to move and position parts or tools

within a work envelope. Wrist - The wrist is used to orient the parts or

tools at the work location. The robot manipulator is created from a

sequence of link and joint combinations. Thelinks are the rigid members connecting the

joints, or axes.


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Robot Safety

Depending on the size of the robots work

envelop, speed, and proximity to humans.

safety considerations in a robot environment

are important and particularly forprogrammers and maintenance personal who

are in direct physical interaction with robots.


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Control For Automatic Arc Welding

A control system is required to run thewelding program.

Mechanized and automatic welding have

more complicated programs and controladditional functions, including travel or

motion, torch position and fixture motion.

Adaptive welding, which varies weld

parameters in accordance with actual

conditions, has a complicated computer

control system that include sensing devices

and adaptive feedback.


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In semiautomatic, welding a control

mechanism in the wire feeder actuates

electrode wire feed and starts the welding

current and shielding gas flow when the

welder presses the gun trigger.


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WELDING CONTROLLER


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Robot Controller

For robotic arc welding system, a much more

complex controller is required.

Controller include a high speed

microprocessor since coordinated,

simultaneous, continuos motion of up to eight

axis and all welding parameters may be

required.


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Robot Controller


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Robot Controller

The machine tool industry introduced numerical control(NC) years ago,

these are known a Point To Point(PTP) control system.

Point are location in two dimension in one plane

For arc welding robot, the arc is moved from one point to the next in

space.

The location of the arc is known as the tool center point(TCP)

The path of the TCP is programmed and stored in memory.

For spot welding, pick and place and machine loading, point to point

playback is used.

For arc welding, playback of the arc motion is a continuos path in

space.

The robot controller must be cooerdinated so that each axis movement

begins and end at the same time.


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Programmer Function

accept the input of many point locations.

relate welding parameter to the path tought.

store this information in memory. play it back to execute a welding program.

The major points of interest are the teach

mode, memory and playback or execution.


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The method of teaching or programming the robot

controller:

Manual method: The manual method is not used for arc welding robot

but it is used mainly for pick and placed a robots.

Walk through: The walk through method requires the operator to move

the torch manually through the desired sequence of movement. . Each

move is recorded into memory for playback during welding. The weldingparameter are controlled at appropriate positions during the weld cycle.

Lead through: The lead through method is a popular way in

programming a robot. The robot welding operator accomplishes this

using the teach pendant. By means the keyboard on the teach pendant,

the torch is driven through the required sequence of motion. In addition,

operator inputs electrode wire speed, arc voltage, arc on, counters,output signals, job jump function and much more. All of this function are

related to a particular point along the taught path. In this way, if the

speed of robot is changed, it is not necessary to change the time for

certain actions to happen.


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Off-line programming:

Off-line programming involves the preparation of the program on a

computer. An appropriate languages must be used. The program is

entered into the robot memory very quickly. This increase the use of the

robot,since lead-through teaching ties up the robot during programming.Off line programming is becoming more widely used, but requires

experienced personnel.


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Weld Execution

1) Weld can be made only when the power is on all components,electrode wire is installed, and the controller is in playback or operatemode

2) The material must be in the fixture and ready

3) Pushing the start button will initiate the operation

4) The robot will move the torch to the start point.

5) The welding equipment will begin its cycle of operation (gas preflow,start the arc).

6) The robot controller will determine that the arc has started and thenstart motion.

7) Points along the taught path will initiate other activities programmed8) At the end of the taught path, the welding equipment will terminate the

weld program and the robot controller will determine that theelectrode wire has separated from has separated from the work


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9) After this the robot will return to its home

position, ready for another cycle.10)At this points the weld should be checked for

quality.

11) The program should be checked and editedto improved the weld if necessary and tominimize the air cut path and increase air cutspeed.

12) When the weld quality is acceptable andcycle time is at a minimum, it is time to freezethe program and start production.


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Robotic sensor

Robotic sensor is a system that detects variations in partsand compensates for the variation by shifting the roboticprograms.

A sensor is effective when it is difficult to keep programmedpoints in consistent locations and there are part accuracy

problems requiring the operator to frequently adjust taughtrobot points. When this occurs, sensors can be used toautomatically shift the welding points.

Block Diagram of fuzzy controller


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End-of-arm sensor and tool centre point calibration is a

critical aspect of successful system implementation. End-of-arm sensing, in the context of robotic welding, is used todetect the actual position of the seam on the workpiecewith respect to the robot tool frame.


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Result of welding pool control. (a) with control ; (b) withcontrol


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TCP-Calibration Unit(Tool

Center point)

Tool Center point calibration unit

used to detect the actual position of the seam onthe workpiece with respect to the robot toolframe.

While end-of-arm sensor based control wouldappear to solve both robot accuracy andworkpiece position error problems, this is only so

if the sensor frame end frame and tool frame

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arc welding Method Not Allowed