Robotic WeldingR.SRIDHAR

15MC010 M.E.MECHATRONICSTHIYAGARAJAR COLLEGE OF ENGINERING

Outline

1. Robot Technology State of the Art2. Robot environment and Driving Forces to Automation3. Difficulties in Automation4. Improvements needed in the near future.5. Welding Application - Overview6. Software architecture7. Remote Services8. Adding equipment9. Conclusions

Working Principle

The fusion is carried out under the protection of an inert gas (argon or helium), or mixture of an inert gas with much cheaper gases like oxygen or carbon dioxide (CO2), in order to prevent the pernicious contamination with some gases of the atmosphere (oxygen, nitrogen and hydrogen). Applying a high current to the electrode causes its tip to melt transferring in this way metal to the work-piece.

Contn.. The experienced and skilled manual welder is able to select

the welding process parameters based on similar cases previously encountered. In particular, he is able to:

1. Select the type of shielding gas, the 2.type and diameter of wire to use, 3.and the initial current and voltage

settings more suitable for the case in hand.4. Adjust continuously the process

variables by looking to the molten pool or by listening to the sound produced by the arc.

5. Maintain the torch in the correct position with precision and stability, which is fundamental for a good and constant weld.

Welding Technology Gas Tungsten Arc Welding / TIG Welding

-welding process where the arc is created between a non consumable electrode and the work metal. Gas Metal Arc Welding /MIG Welding

-welding process, uses the heat of the electric arc to melt the consumable electrode wire and the metallic components to be welded. Laser Beam Welding Resistor Spot Welding Friction Stir Welding

Power Source

Considering Parameters The input data is generally the Type of weld

-butt weld or -fillet weld The welding position -flat, -horizontal -vertical or -overhead

The output data is usually the welding parameters namely-current-voltage-welding speed and number of weld beads/layers

Common Welding Joints

What is Robotics

And how do we define robotics then? Is it a science? Is it a technique or collection of techniques? If the reader takes a robotics book then something like this appears:

“A robot is a re-programmable multi-functional manipulator designed to move materials, parts, tools, or specialized devices, through variable programmed motions for the performance of a variety of tasks”, from the book Robotics – Control, Sensing, Vision and Intelligence, Fu, Gonzalez, Lee, MacGraw Hill, 1987.”

Why to Automate Welding?

Actually robot manipulators are interesting machines in terms of flexibility, programmability and precision.

perform industrial tasks in a human-like manner with at least comparable quality for longer periods of time.

Robots manipulators present the best rate between “production cost” and “production volume” for small/medium production volumes

are unique flexible machines (mainly due to programmability) that can be adapted to perform very different tasks. Consequently

Manufacture of Welding Robots

1. Yaskawa / Motomam2. FUNUC3. ABB4. KUKA5. KAWASAKI6. COMAU7. PANASONIC,COOLS,NACHI

Robot Manipulator And Parameters

A T-pipe representing a type of work-piece that should benefit from a seamtracker which can compensate for both position and orientation changes

Features of Robot Manipulators Programmable control system, using powerful programming languages and

environments. It is possible to define positions/orientations, define reference systems,

parameterize trajectories and other actions, and play that continuously with high precision and repeatability.

Advanced PLC capabilities are also available, namely, IO control and data acquisition, and several communication interfaces and protocols. These functionalities enable robots to coordinate actions with other equipment's and sensors, and being integrated with other computers and manufacturing systems existing in the setup.

Sensors for Welding Robots 1. Sensors for Technological Parameters

Arc VoltageWelding Current

Hall Effect SensorCurrent Shunt

Sensors for Geometrical ParametersOptical SensorsThrough-arc Sensing

Sensor Type Sensor

Contact type(Weld seam tracking)

Mechanical Type - Roller Spring. Electromechanical type:1) Two probes across the seam line.2) A probe in the seam line.Electric control type with probe.

Non-contact type(Various Purposes)

A. Physical type:1) Acoustic – arc length control.2) Capacitance – distance control.3) Eddy current –seam tracking.4) Induction – seam tracking.5) Infrared radiation – penetration control.6) Ultrasonic – penetration and weld quality.7) Magnetic – detecting electromagnetic field.B. Through-the-arc type:1) Arc length control (arc voltage).2) Weaving with electric measurement (GTAW, GMAW).C. Optical/vision (image capture and process):1) Vision sensors.2) Laser sensors.3) Opto-electric sensors.

Fault Detection Using Monitoring

Parameters in GMAW which affect the weld penetration and bead geometry are for example:

Welding current Arc voltageWelding speedWire feed rateElectrode extensionElectrode composition and diameterShielded gas composition and flow rate

Robotic Welding: System Issues

Preparation phase: where the welding operator sets up the parts to be welded, the welding apparatus (power source, robot, robot program, etc.) and the welding parameters. The type of gas and the type of wire are also selected in this phase

Welding Phase the system should be able to maintain the torch orientation while following the desired trajectory (that may be different from the 106 Welding Robots planned one), perform seam tracking and change welding parameters in real-time.

Analysis Phase When advance sensors are used, like laser 3D cameras, this phase can be executed on-line during the welding phase. This is particularly interesting since evaluation of welding quality on-line may influence the ongoing welding process.

Robot Coordinate System*The world coordinate system relates the coordinate systems in a work cellwhere robots and other peripheral devices exist. *The base coordinate system is the coordinate system for the robot. *The hand coordinate system is at the face of the robot end effectorwhere tools are attached. *The tool coordinate system is at the tip of the torch and defines the Tool Center Point (TCP) and the Tool Center Line (TCL).

Trends in Welding Automation Technologies in Actual Fabrication

Unmanned Robot Welding System Narrow Gap Welding of Heavy Plates Field Girth Welding of Gas Pipelines Rail Welding Technologies

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