SMAW

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SMAW Shielded Metal Arc Welding Welding Machines
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• Definition
• Welding heat is generated by an electric arc
  between a consumable rod that is flux covered and
  the work.
• Electrical current can be from either a AC or DC
  source.

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• Three Types of Current Configurations
• AC
• DC Electrode Positive (DCEP)
• DC Reverse
• DC
• DC Electrode Negative (DCEN)
• DC Straight
• DC

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AC
Even melting rate Heat distributed evenly Most
common at home
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AC Current
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DC Electrode Positive (DCEP) DC Reverse DC
Slower melting rate Heat on the work Most common
in industry Usually best weld characteristics
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DC Electrode Negative (DCEN) DC Straight DC-
High melting rate Heat on the rod Not very common
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Welding Machines

• Constant Current
• SMAW and GTAW
• Current remains constant with fluctuations in
  voltage
• Aids with the stability of the arc
• Constant Voltage
• GMAW FCAW DSAW
• Current remains constant with changes in voltage.

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Constant Current (Plotted)
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Constant Voltage (plotted)
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Constant Current Machines

• Transformer
• Generator
• Inverter

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Transformer Welders

• Transformer
• Solid State
• Moving Coil
• Moving Core
• Tapped Secondary or Multiple Coil
• Transformers produce ac current
• (DC current is produced by using a bridge type
  rectifier)
• Cheap, Effective, Heavy, Simple, Low Maintenance

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Transformer Welders
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Typical Transformer
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Transformer TypesMoving coil
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Transformer TypesMoving Core
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Transformer TypesMultiple Coil or Tap
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Bridge Rectifier
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Generator

• Basic DC generator for dc current or an
  alternator with a rectifier for DC current

Portable, Heavy, High Maintenance, Expensive
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Inverter

• Like a transformer but the frequency is raised in
  the primary windings.
• Frequency is changed from 60 hz to 50,000 hz.
• Frequency size can be reduced by 70

Light Weight, Low Maintenance, Expensive, Light
Weight
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Inverter
Light Weight, Low Maintenance, Expensive, Light
Weight
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Welder Cost
225 amp transformer 600
225 amp inverter 2800
225 amp generator 600