Thursday, September 9, 2010

What are the reasons to oscillate a weld process


Vince H. from Oshkosh Truck asks,

"What are the reasons to oscillate a weld process?"

There are a number of ways and reasons a weld process would be oscillated. Oscillation is the side to side manipulation of a weld in progress. It is measured in amplitude (how far), frequency (how often) and dwell time (for how long).

Spend any time around GMAW (Mig) robots and you'll notice the torch is in a constant side-to-side motion. Typically referred to as a weave, this form of oscillation helps that robot find its way along the joint by monitoring changes in the arc. Another good example of oscillation would be a Pipefitter using the GTAW (Tig) process and a "Walkin' the Cup" technique. He or She will do this to minimize fatigue on their body, increase bead width and improve tie-in at the welds toe. A real craftsman will rock that Tig cup along the joint and make a beautiful finish weld, with a consistent face, completely around that pipe joint. It can be a real work of art (or a real cobbled mess for that matter).

Other types of oscillation may be manipulating the molten weld pool by using a magnetic force. Common with (but not limited to) mechanized GMAW and GTAW processes, this magnetic force will move the molten puddle (not the torch) from side to side. I've used this technique to increase bead width for customer appeal, but it can equally be used to improve sidewall fusion or tie-in at the weld toe. Some wire fed processes (SAW or ESW) will actually twist the electrode as it is fed as a form of oscillation.

Oscillation helped a Steel Worker using Electroslag to fabricate components for San Francisco's Bank of America building. It aided the arm fatigue of a Pipefitter as he built Louisiana's River Bend nuclear power plant. It will also assist the Iron Worker that will build the One World Trade Center, to achieve better weld toe fusion, allowing his or her welds to transfer stress smoothly between support beams.

Want to know more about “Walkin’ the Cup”? Follow this link:

(http://www.millerwelds.com/resources/articles/TIG-gtaw-cup-walking-pipe-welding/)

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