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Microelectronics Clean Room

Electrical and Computer

EngineeringOrbital Tube Welder

by Clayton Gatewood

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Overview

General Information

Safety

Set-up

Tube Preparation: facing, cleaning

Operation

Weld Schedules

Weld Evaluation

by Clayton Gatewood

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Orbital Tube Welding

Gas Tungsten ArcWelding (GTAW)process

Fusion Welding

Model 8 WeldHead

Model 207A Power

SupplyArgon Gas

Cylinder

Facing Tool

ARC Machines, by Clayton Gatewood

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Gas Tungsten Arc Welding (GTAW)

Process

Used to weld tubing that remains in-place while the tungsten electrode

rotates around the target joint.

Material edges are heated by an arcand are fused together without a filler.

by Clayton Gatewood

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Safety

Electricity Hazard: Shock, RFStarting, Pacemaker, ElectricStorage Devices

Fire Hazard: Clothing, SealedContainers, Welded Material Hot to

Touch Harmful UV Radiation (eyes and

skin)

Toxic Fumes from WeldingStainless Steel, HexavalentChromium (lung cancer)

Air Displacement by Argon Gas

Factory Training Essential

Keep Hands and Fingers Clear

Compressed Gas Cylinders

Cleaning Chemicalsby Clayton Gatewood

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Set-Up

Ensure Power is Off

Connections: Weld

Head, Argon Gas,

main power cordApply Argon ( turn)

@ 20 psi

by Clayton Gatewood

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Tube Preparation

Facing

by Clayton Gatewood

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Welding Cleanliness

Materials to be welded must be free ofgrease, oil, rust, dirt, paint and other

contaminants.

Dirty materials can result in porosity,discoloration, slag deposits, and

generally poor quality welds.

by Clayton Gatewood

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Operation

Align target joint with

tungsten electrode

Connect Argon Purge Line

and set for 5 psi (for OD

tubing)

Select Weld Schedule

Ensure Power Supply is

Ready to Weld

Press Seq Start

Prepurge, Weld,Downslope,

Postpurge

by Clayton Gatewood

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Weld Schedule Development

An orbital tube

weld may be done

in 4 or more levels.

It must includeenough time for tie-

in before the

downslope.

by Clayton Gatewood

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Weld Schedules

Pre / Post PurgeTime

Up / Downslope

Rotation Direction

Rotation Delay Pulse Mode

Rotation Mode

RPM (Rotor Travel

Speed) Level Times

Level Amps

Background Amps

Pulse Timesby Clayton Gatewood

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Power Supply Sequence

by Clayton Gatewood

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Sample Weld Schedules

by Clayton Gatewood

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Weld Evaluation

60 to 80% overlapon outer diameter

Poor rotation delay

Borescope toinspect innerdiameter

Full penetration

No cracks,undercut,

crevices, pits, orembedded or

protruding materialby Clayton Gatewood

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Weld Profiles

by Clayton Gatewood

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Weld DefectsWeld Problem Probable cause(s)

Lack of

penetration to I.D.

1) Insufficient amperage

2) Tungsten offset

3) Change of heat number

4) Sulfur mismatch

5) Variable wall thickness

OD Concavity

1) Too much amperage

2) Gravity (heavy wall)

3) Very low sulfur

ID Concavity 1) Excessive ID purge pressure

Discoloration of ID

(oxidation)

1) Excessive oxygen and/or moisture in ID

purge gas

2) Moisture and/or oxygen in or on tubing

3) Chemical residue from EP

4) Leak in purging set up

5) Pinched gas hoseMisalignment

1) Dimensional tolerances - out of round

2) Wall thickness mismatch

3) Worn out TCIs

4) Poor workmanship

Porosity 1) Moisture in purge gas

2) Moisture or dirt on weld components

Excessive slagging 1) impurities in base material especially

oxides of aluminum, calcium, silicon

by Clayton Gatewood

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Argon Purge and Oxygen

Left to Right = effect of increasing

levels of oxygen in the argon purge

by Clayton Gatewood

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Possibilities

by Clayton Gatewood

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Works Cited"MODEL 207 Operator Training Guidelines." ArcMachines, Inc.CD-ROM.Pacoima, CA: Arc

Machines, Inc., 2007.

Model 207 Microprocessor-Controlled PowerSupply.1 Nov. 1996. Arc Machines, Inc.. 16

Oct.

2007..

by Clayton Gatewood