Chapter 14: Plasma Arc Cutting (PAC)

CNC plasma cutting something for NASA. A close up photograph of the tip of a welding torch throwing off sparks as it cuts into a piece of metal.
Plasma Arc Cutting / Photo Credit: NASA, PD

Overview

Sparks fly as the arc is established. The rushing sound of the compressed gas fills the shop. The gantry of the burn table springs to life and races across the plate, leaving a narrow opening in the metal behind it. The operator watches as the cutting head twists and turns, his attention divided between the table itself and the computer screen that tracks its movements along the cut path. Every now and then, the cutting stream stops, and the torch is raised and moved to another spot on the plate. As it finds its new mark, the torch is lowered, and with a flash and a hiss, the cutting head is off again. The operator appreciates the speed at which this process moves, realizing that this complex part would take up to three or four times as long to cut by hand.

Plasma Arc Cutting (PAC) is one of the leading methods of thermally cutting metals in the welding industry today. The first time you make a cut using a handheld plasma torch, you will immediately see the difference from an oxy-fuel torch. PAC is recognized for its speed, versatility, and precision, especially when used in conjunction with automation. From the hobbyist in the home shop to multimillion-dollar companies, PAC is used to cut simple and complex parts out of a wide variety of metals quickly and accurately.

Plasma cut slots at an angle and around a corner. A metal box with rounded edges has two clean-cut slots that were done with plasma arc cutting. The cuts are at an angle and around a corner, and very precise.
Figure 14.1. Plasma Cutting Slots / Photo Credit: Devaes, CC BY-SA 3.0

In this chapter you will learn about the fundamental aspects of the PAC process. You will be introduced to some of the history of PAC, as well as current applications. You will be shown the components of the cutting system, and study techniques in order to become proficient with using this process.

A person wearing safety gear, including a helmet with a faceguard performs plasma cutting. Sparks generated by the cutting process flash from the metal being cut.
Figure 14.2. Hand Held Plasma Cutting / Photo Credit: U.S. Air Force photo by Senior Airman Michael Washburn, PD

Objectives

After completing this chapter, you should be able to:

  • List Plasma Arc Cutting (PAC) process’ uses in industry.
  • Identify equipment associated with PAC.
  • Identify gasses used with PAC and their benefits
  • Recall techniques for using PAC.

Key Terms

  • Plasma
  • Dross
  • Torch
  • Nozzle/Tip
  • Retaining Cap
  • Swirl Ring
  • Electrode

Attributions

  1. Chapter opening image: Advanced Metals and Composites Development Branch (Code RMF) by NASA in the Public Domain; United States government work
  2. Figure 14.1: Plasma cut by Devaes is released under CC BY-SA 3.0
  3. Figure 14.2: Yokota plasma cutter by U.S. Air Force photo by Senior Airman Michael Washburn in the Public Domain; United States government work

License

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Introduction to Welding Copyright © by Washington State Board for Community and Technical Colleges is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.