Truckin’ with AluminumAluminum Welding from A to Z

Zane MichaelChris Anderson

Outline

Aluminum Welding vs. Steel◦ Process differences

Aluminum Welding Process Features◦ Starting and Stopping

◦ Dual Pulse for Cosmetics

Wire Feeding: Push or Pull?◦ Anderson – case for push

◦ Zane – case for pull

Aluminum Trailer Production◦ Equipment considerations for larger structures

Robot Reach vs. More Robots

Wire delivery for mobile robots

Sensor selection

Aluminum vs. Steel - Basics

High Thermal Conductivity◦ Makes it difficult to get puddle to fuse at start(cold lap)◦ Heat travels along joint and “preheats” weld

Weld bead can widen if nothing else is changed

Low Melting Point◦ Once mat’l is heated it melts quickly◦ AL puddle is very fluid and can run quickly (esp. 4043)

Little color change between solid/liquid aluminum◦ Without red to orange color change in steel, it can be

difficult to judge how much heat is in AL part.

Fast Solidification Rate◦ Can often travel faster than steel◦ Rapid freezing of puddle leaves depression in crater

Aluminum Process Considerations

Arc Starting – Need to “burn in” at start◦ Hot Starting – Travel short distance with “Hot” settings

Steel uses dwell at start to build puddle, this will promote cold lap with AL

◦ Lift Starting – retracting wire with pull guns

Dual Pulse – Alternating Heat Settings at 2-5 Hz◦ Can produce GTAW like cosmetics with GMAW◦ Can balance Heat Input in long welds producing uniform bead width◦ May be power source or robot based; best when it includes a change in wire

feed speed to get high/low current settings

Arc Ending – Need more time to fill puddle◦ Will be at least 1 second and often more for larger welds◦ Two stage crater is advantageous for fill 1 and fill 2◦ Back stepping crater can help move depression from end of weld◦ Controlled burnback to minimize the ball (key to good start)

Travel Angle◦ 10-15 deg push angle promotes flat bead, reduces smut (steel=5-10 deg)◦ Faster freeze allows faster travel speeds

Arc Starting

High Thermal Conductivity◦ Makes it difficult to

get puddle to fuse at start(cold lap)

◦ Heat travels to thicker member and causes puddle to favor one side

Lack of fusion at toe of weld

Puddle favors upper leg

Arc Starting

Arc Starting – Need to “burn in” at start◦ Hot Starting – Travel

short distance with “Hot” settings

Steel uses dwell at start to build puddle, this will promote cold lap with AL

◦ Slope current– can gradually reduce heat (if supported)

Current

Motion

5-15 mm

Arc Starting

◦ Parameters can be balanced to minimize size of the start

Lift Starting –retracting wire with pull guns◦ Used to create more

stable arc start

Dual Pulse – TIG like cosmetics

Dual Pulse – Alternating Heat Settings at 2-5 Hz◦ Can produce GTAW like cosmetics with GMAW

◦ Can balance Heat Input in long welds producing uniform bead width

Dual Pulse Video

Frequency controls spacing

F = 2 Hz

F = 5 HzF = OFF

Power source or Robot based

Ref.

Sealed welds on tanks

Why did trucking customer reject welds?

Arc Ending – Fill the puddle

Arc Ending – Need more time to fill puddle◦ Will be at least 1 second

and often more for larger welds

◦ Two stage crater is advantageous for fill 1 and fill 2

◦ Back stepping crater can help move depression from end of weld

◦ Controlled burnback to minimize the ball (key to good start)

Arc End – Crater Fill

Single Step Crater Two Step Crater

Fill and slight depression

Fill1 and fill 2

Current< 100 Amps

Arc End

Arc End – Back Step Crater◦ Use heat of weld to

fuse end (dwell)

◦ Reverse direction a few mm and fill depression

◦ Reduces stress riser of crater

Current

Motion

5-15 mm

< 100 Amps

< weld current (Fill 1)

Dwell at End

Welding Considerations (1)

Travel Angle◦ 10-15 deg push angle promotes flat bead, reduces smut (steel=5-10 deg)

◦ Faster freeze allows faster travel speeds

Water Cooled Torch!◦ Reduces swelling of wire in tip

◦ Aluminum is hot spray arc even at low amps

Watch Gas Coverage◦ Straight bore nozzle; recessed tip

Fe Al

Welding Considerations (2)

Clean Material◦ Oil and excessive oxide will result in soot and porosity

◦ Clean with Stainless Steel brushes

Use SS tooling details with Al, does not melt together

U shaped drive rolls for Al

Teflon or plastic consumables◦ Avoid sharp edges and breaks in feed

Brass jump liner at tip –helps w/heat

Reduce breaks in feed

system

Welding Considerations - Sensors

Touch Sensing◦ Possible with Aluminum, but softer wire may limit

search speeds due to bending

◦ Don’t use wire brake! Pull gun can keep wire in constant position

Through Arc Tracking◦ Not possible with current signal only

◦ Some manufacturers working on hybrid signals

Laser Sensors◦ Generally, most reliable sensor on Aluminum

◦ Need to evaluate surface condition and reflectivity

Wire Feeding – Push vs. Pull

Push with Aluminum Pull Gun for Aluminum

Chris Anderson, Excellence in Robotic and Automated Arc Welding Award Winner

Zane Michael, Salesman

GMT 800 Radiator Support

Push Only Experience

Largest robotic aluminum welding installation at a single site in North America

◦ More than 120 welding robots

◦ 35,000 parts/week with 90+ welds/part

◦ 3,000,000 arc starts per week with push-only feed system

◦ More than eight years of production

Push Only Feed w/WC torch

Feeder on upper arm

◦ Limit feed distance

Motorized bulk dereelers

Power Source with positive starting

◦ 2,000 arc start test in 1990’s

Push Feeding for aluminum

Introduction of Thru-Arm robots has shortened feed distance and reduced torch cable bends and flexing

Push Only Video

Pull Torch for Al Feeding

Push-Pull Feed systems are often promoted by power source manufacturer

◦ Wire feed speed synchronized by power source control

◦ Improved arc starting (lift start) with wfs control at the torch

◦ Insurance for feeding soft alloys (3/64 4043)

◦ Water-Cooled for Aluminum

May be Pull only torch on robot with remote assist feeder

Motorized bulk assist feeders

Push Pull Video

Push-Pull req’d for thin mat’l

Push-Pull can provide specialty capability for thin mat’l

Push-Pull for Thru-Arm Robots

Fronius Robacta Lincoln SA Aluminum

Best of Both Worlds

Key Factors for Truck Welding

Larger size parts to weld◦ Long reach robots; push pull consideration

◦ Multiple Robots; cover longer rail assemblies

◦ Robots on tracks; wire drum on carriage

Sensors; touch sensing or laser sensors.. NOT through arc

Examples of some layouts for Trailer Mfg.

Long Reach Robots for Trailers

Combine Sub-Ass’y, Final Ass’y

Bulk Trailer System

Multiple Robots on Long Ass’ys

Flat Bed Trailer snip-it

Bulk Wire Feed for Al

Pull Torch for Feed Assist Feeder for Bulk

Robot on Track = Tow Wire Drum

Trailer System 1 Trailer System 2

Laser Sensors for Aluminum

Point Laser Seamfinder Appl

Tool Boxes Correguted Panels

Lap Joint on Boxes - OK

Al Sheet Panel – Too Reflective