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Mechanized,Automated, andRobotic Welding

welding know-how for engineers

MECHANIZED, AUTOMATED,AND ROBOTIC WELDING

Prepared by theWelding Handbook Chapter Committee on Mechanized, Automated, and Robotic Welding:J. S. Noruk, ChairTower Automotive, Inc.R. E. BromanTower Automotive, Inc.L. K. GrossMilwaukee Area Technical

CollegeT. B. HansenABB Flexible Welding ControlV. L. Mangold, Jr.KOHOL Systems, Inc.T. B. MorrisFanuc Robotics North

AmericaS. D. NelsonTrek Bicycle CorporationR. F. NochJohnson Controls, Inc.J. S. PhillipsDetroit Center ToolM. M. WeirPanasonic Factory

AutomationC. L. WoodmanThe Lincoln Electric Company

Welding Handbook Committee Member:J. H. MyersWelding Inspection &

Consulting Services

ContentsIntroduction 2Mechanized Welding 3Automated Welding 8Robotic Welding 17Planning for Automatedand Robotic Welding 24Conclusion 32Bibliography 32SupplementaryReading List 32

C H A P T E R 9

Photograph courtesy of Fanuk, Incorporated

2 MECHANIZED, AUTOMATED, AND ROBOTIC WELDING

INTRODUCTIONThe methods of applying the various welding pro-

cesses are categorized according to the degree of opera-tor involvement in the performance of weldingoperations. In manual welding, defined in the AmericanNational Standard Standard Welding Terms and Defini-tions, AWS A3.0:2001, as “welding with a torch, gun,or electrode holder held and manipulated by hand,”1, 2

the welder performs the welding function and main-tains continuous control of the welding operations byhand. In semiautomatic welding, defined as “manualwelding with equipment that automatically controlsone or more of the welding conditions,”3 the weldermanipulates the welding gun to create the weld whilethe electrode is automatically fed to the arc.

In mechanized welding, defined as “welding withequipment that requires manual adjustment of theequipment controls in response to visual observation ofthe welding, with a torch, gun, or electrode holder heldby a mechanical device,”4 the welder’s intervention con-sists of adjusting the equipment controls in response tovisual observation of operations.

1. American Welding Society (AWS) Committee on Definitions,2001, Standard Welding Terms and Definitions, AWS A3.0:2001,Miami, American Welding Society, pp. 50–51.2. At the time of the preparation of this chapter, the referenced codesand other standards were valid. If a code or other standard is citedwithout a date of publication, it is understood that the latest editionof the document referred to applies. If a code or other standard iscited with the date of publication, the citation refers to that editiononly, and it is understood that any future revisions or amendments tothe code or standard are not included; however, as codes and stan-dards undergo frequent revision, the reader is encouraged to consultthe most recent edition.3. American Welding Society (AWS) Committee on Definitions,2001, Standard Welding Terms and Definitions, AWS A3.0:2001,Miami, American Welding Society, p. 67.4. American Welding Society (AWS) Committee on Definitions,2001, Standard Welding Terms and Definitions, AWS A3.0:2001,Miami, American Welding Society, p. 51.

In automated welding, defined as “welding withequipment that requires only occasional or no obser-vation of the weld, and no manual adjustment of theequipment controls,”5 the welder’s involvement is limitedto activating the machine to initiate the welding cycleand observing the weld on an intermittent basis, if at all.

Robotic welding, defined as “welding that is per-formed and controlled by robotic equipment,”6 entailsno involvement on the part of the welding operator inperforming the weld, as the welding operations arecarried out and controlled by welding robots.

In both automated and robotic welding, however, theoperator plays an active role in quality control throughthe identification of the presence of weld discontinuities.When discontinuities are encountered, appropriate mea-sures must be taken on the part of maintenance or pro-gramming personnel to correct deviations.

Adaptive control welding is defined as “welding witha process control system that automatically determineschanges in welding conditions and directs the equip-ment to take appropriate action.”7 This process appli-cation relies on sensors to provide real-time dataregarding abnormalities to the computer controller. Thecontroller then makes the necessary changes in weldingparameters to produce quality welds. Thus, welding isperformed and controlled without operator interven-tion or supervision.

Figure 1 summarizes the capabilities of the differentwelding application methods.

5. American Welding Society (AWS) Committee on Definitions,2001, Standard Welding Terms and Definitions, AWS A3.0:2001,Miami, American Welding Society, p. 13.6. American Welding Society (AWS) Committee on Definitions,2001, Standard Welding Terms and Definitions, AWS A3.0:2001,Miami, American Welding Society, p. 64.7. American Welding Society (AWS) Committee on Definitions,2001, Standard Welding Terms and Definitions, AWS A3.0:2001,Miami, American Welding Society, p. 11.

MECHANIZED, AUTOMATED,AND ROBOTIC WELDING

C H A P T E R 9

MECHANIZED, AUTOMATED, AND ROBOTIC WELDING 3

MECHANIZED WELDING

Mechanized welding is often selected and implementedto reduce labor costs and improve quality, especiallywhen performing welding and cutting operations involv-ing large components or structures. It can be used toapply most fusion welding and thermal cutting processes.

In mechanized welding, the welding operation is per-formed under the observation and control of a weldingoperator. The mechanized welding equipment controlsthe following variables:

1. Initiation and control of the welding arc,2. Feeding the welding electrode wire into the arc,

and3. Control of movement and travel speed along the

joint.

The equipment may or may not perform the loadingand unloading of the workpieces.

Mechanized welding must allow sufficient time forthe welding operator to monitor and control the guid-ance aspects of the operation as well as the welding pro-cess variables. Weld quality and productivity are oftenenhanced as a result of the proper control of processvariables. To perform this task, the operator must bepositioned near the point of welding to observe theoperation closely. He or she interacts continually withthe equipment to ensure the proper placement and qual-ity of the weld metal. Changes to wire feed speed, cur-rent, voltage, torch position, torch extension, and travelspeed may be required.

The travel speed of the carriage is an importantwelding variable, as uniform speed and weld directionduring operation are vital for quality welds. Qualityalso depends on how rigidly the welding carriage is heldto the track because excessive vibration or dimensionalvariation can adversely affect the wire tip position.

Mechanized welding improves the efficiency of theprocess while minimizing operator fatigue, therebyincreasing the consistency and quality of the welds. This

Method of Application Manual Semiautomatic Mechanized Automatic Robotic Adaptive Control

Arc WeldingElements/Function

Starts andmaintainsthe arc

Person Machine Machine Machine Machine(with sensor)

Machine(robot)

Feeds theelectrodeinto the arc

Person Machine Machine Machine Machine Machine

Controls theheat for properpenetration

Person Person Machine Machine Machine(with sensor)

Machine(robot) (onlywith sensor)

Moves the arcalong the joint (travels)

Person Person Machine Machine Machine(with sensor)

Machine(robot)

Guides thearc alongthe joint

Person Person PersonMachine

via prearrangedpath

Machine(with sensor)

Machine(robot) (onlywith sensor)

Manipulatesthe torch todirect the arc

Person Person Person Machine Machine(with sensor)

Machine(robot)

Corrects the arcto overcomedeviations

Person Person PersonDoes not correct; hence, potential

weld imperfections

Machine(with sensor)

Machine(robot) (onlywith sensor)

Source: Adapted with permission from Cary, H. B., 1994, Modern Welding Technology, 3rd ed., Englewood Cliffs, New Jersey: Regents/Prentice Hall, Figure 12-1.

Figure 1—Methods of Applying Welding Processes