Microelectronics Clean Room
Electrical and Computer Engineering
Orbital Tube Welder
by Clayton Gatewood
Overview
General Information
 Safety
 Set-up
 Tube Preparation: facing, cleaning
 Operation
 Weld Schedules
 Weld Evaluation
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by Clayton Gatewood
Orbital Tube Welding
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Gas Tungsten Arc
Welding (GTAW)
process
Fusion Welding
Model 8 Weld Head
Model 207A Power
Supply
Argon Gas Cylinder
Facing Tool
ARC Machines, Inc.
by Clayton Gatewood
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 arc and
are fused together without a filler.
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by Clayton Gatewood
Safety
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Electricity Hazard: Shock, RF Starting,
Pacemaker, Electric Storage Devices
Fire Hazard: Clothing, Sealed
Containers, Welded Material Hot to
Touch
Harmful UV Radiation (eyes and skin)
Toxic Fumes from Welding Stainless
Steel, Hexavalent Chromium (lung
cancer)
Air Displacement by Argon Gas
Factory Training Essential
Keep Hands and Fingers Clear
Compressed Gas Cylinders
Cleaning Chemicals
by Clayton Gatewood
Set-Up
Ensure Power is Off
 Connections: Weld
Head, Argon Gas,
main power cord
 Apply Argon (¼ turn)
@ 20 psi
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by Clayton Gatewood
Tube Preparation
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Facing
by Clayton Gatewood
Welding Cleanliness
Materials to be welded must be free of
grease, oil, rust, dirt, paint and other
contaminants.
 Dirty materials can result in porosity,
discoloration, slag deposits, and generally
poor quality welds.
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by Clayton Gatewood
Operation
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Align target joint with
tungsten electrode
Connect Argon Purge Line
and set for 5 psi (for ¼” OD
tubing)
Select Weld Schedule
Ensure Power Supply is
“Ready to Weld”
Press “Seq Start”
Prepurge, Weld, Downslope,
Postpurge
by Clayton Gatewood
Weld Schedule Development
An orbital tube weld
may be done in 4 or
more levels.
 It must include
enough time for tiein before the
downslope.
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by Clayton Gatewood
Weld Schedules
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Pre / Post Purge Time
Up / Downslope
Rotation Direction
Rotation Delay
Pulse Mode
Rotation Mode
RPM (Rotor Travel
Speed)
Level Times
Level Amps
Background Amps
Pulse Times
by Clayton Gatewood
Power Supply Sequence
by Clayton Gatewood
Sample Weld Schedules
by Clayton Gatewood
Weld Evaluation
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60 to 80% overlap on
outer diameter
Poor rotation delay
Borescope to inspect
inner diameter
Full penetration
No cracks, undercut,
crevices, pits, or
embedded or
protruding material
by Clayton Gatewood
Weld Profiles
by Clayton Gatewood
Weld Defects
Weld 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
1) Too much amperage
2) Gravity (heavy wall)
3) Very low sulfur
1) Excessive ID purge pressure
OD Concavity
ID Concavity
Discoloration of ID
(oxidation)
Misalignment
Porosity
Excessive slagging
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 hose
1) Dimensional tolerances - out of round
2) Wall thickness mismatch
3) Worn out TCIs
4) Poor workmanship
1) Moisture in purge gas
2) Moisture or dirt on weld components
1) impurities in base material especially
oxides of aluminum, calcium, silicon
by Clayton Gatewood
Argon Purge and Oxygen
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Left to Right = effect of increasing levels
of oxygen in the argon purge
by Clayton Gatewood
Possibilities …
by Clayton Gatewood
Works Cited
"MODEL 207 Operator Training Guidelines." Arc
Machines, Inc.CD-ROM.Pacoima, CA: Arc
Machines, Inc., 2007.
Model 207 Microprocessor-Controlled Power
Supply.1 Nov. 1996. Arc Machines, Inc.. 16 Oct.
2007.<http://www.arcmachines.com/prodMed/m2
07ps/m207ps.html>.
by Clayton Gatewood