1. Microelectronics Clean Room Electrical and Computer Engineering Orbital Tube Welder by Clayton Gatewood

2. Overview General Information Safety Set-up Tube Preparation: facing, cleaning Operation Weld Schedules Weld Evaluation by Clayton Gatewood

3. Orbital Tube Welding 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

4. 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. by Clayton Gatewood

5. Safety 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

6. Set-Up Ensure Power is Off Connections: Weld Head, Argon Gas, main power cord Apply Argon (¼ turn) @ 20 psi by Clayton Gatewood

7. Tube Preparation Facing by Clayton Gatewood

8. 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. by Clayton Gatewood

9. Operation 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

10. Weld Schedule Development An orbital tube weld may be done in 4 or more levels. It must include enough time for tie- in before the downslope. by Clayton Gatewood

11. Weld Schedules 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

12. Power Supply Sequence by Clayton Gatewood

13. Sample Weld Schedules by Clayton Gatewood

14. Weld Evaluation 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

15. Weld Profiles by Clayton Gatewood

16. Weld Defects Weld ProblemProbable 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 Concavity1) 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 hose Misalignment 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 slagging1) impurities in base material especially oxides of aluminum, calcium, silicon by Clayton Gatewood

17. Argon Purge and Oxygen Left to Right = effect of increasing levels of oxygen in the argon purge by Clayton Gatewood

18. Possibilities … by Clayton Gatewood

19. 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.. by Clayton Gatewood