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CNC Plasma Cutting – The Basics

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by Stephan Carpenter
Jan 28, 2019

If you're thinking of getting into the world of CNC plasma cutting, there are a few things you need to consider first. This basic guide will take you through what CNC plasma cutting is and how it works.

CNC Plasma Cutting What Is It?

Plasma cutting in progress.
Plasma cutting in progress. Source: Wikipedia

CNC plasma cutting refers to the cutting of metals using a plasma torch controlled from a computer. Plasma cutters operate by forcing a gas or compressed air at high speeds through a nozzle. Once an electric arc is introduced to the gas, ionized gas or plasma is created, the fourth state of matter. It, in turn, cuts through the metal.

CNC plasma cutters vary widely in size, price, and functionality. The machines are highly accurate and fast cutting through, slicing metals at speeds of up to 500 inches per minute. Plasma cutters require a plasma gas and an assist gas to function, and they vary according to the material being cut.

CNC Plasma Cutting Table Setup

CNC plasma cutters require a great deal of space.
CNC plasma cutters require a great deal of space. Source: Cao Jackson / YouTube

When it comes to the machines themselves, the most important considerations are space and safety. Unlike many hobby CNC systems, a plasma cutter needs a large amount of space in a well-ventilated area in order to operate it safely. It is not a machine you can tuck safely into a corner such as you might a 3D printer.

The machine needs area all the way around as a buffer for any stray sparks. Likewise, the floor should be concrete or another flame resistant material.

Space is also required for a gas or compressor as well as for a computer system. To prevent the plasma arc from interfering with the computer itself, the machine must be Earth-grounded, and the computer should be on an uninterruptible power supply (UPS) to assure constant reliable power.

If you plan on setting up your own CNC plasma cutter, make sure your shop’s power source is sufficient (according to the specifications). Plans for a DIY CNC plasma table can be found on Instructables.

CNC Plasma Cutting Shop Ventilation

Adding air to a water table's submerged chamber raises the level of water.
Adding air to a water table's submerged chamber raises the level of water. Source: esabna.com

With respect to ventilation, there are two main types of plasma tables: downdraft and water. 

Downdraft tables have built-in ventilation, designed to pull fumes and debris away from the metal being worked on. Most often, the working surface contains holes, through which particulates are sucked. In this case, one should attach a turbine style of exhaust system to the plenum, in the center of the table.

A water table allows the part being worked on as well as the plasma torch to quickly be submerged and resurfaced, carrying away debris and keeping parts cool. In this case, normal workshop ventilation should suffice.

CNC Plasma Cutting Gas Types

Different gases are used to cut different materials.
Different gases are used to cut different materials. Source: ferrepro.mx

A variety of gasses are used in plasma cutting depending on the quality of the cut and type of material:

  • Oxygen is used for mild steel up to 1 1/4 inches thick but produces a rough-looking cut on stainless steel and aluminum.
  • An argon and hydrogen mix is preferred for smooth cuts in stainless steel and aluminum, as it gives a high-quality cut.
  • In a smaller shop, compressed air is the most common gas used as both a plasma gas and an assist gas. It works well for low current cutting applications in metals up to one inch thick.
  • Other gasses used in CNC plasma cutting are nitrogen and methane, which are most often utilized when cutting thin stainless steel.

CNC Plasma Cutting Software

DXF artwork.
DXF artwork. Source: Amazon

Although most CNC plasma cutters will come with their own software packages, including some form of CAD platform, others may not. In that case, there are several free CAD options available, such as Google Sketchup and DraftSight.

The ability to make your own DXF file or a library of premade files will allow you to begin cutting almost immediately after your system is set up.

CNC Plasma Cutting Materials and Consumables

Plasma cutting tips.
Plasma cutting tips. Source: harborfreight.com

When starting out, mild steel is a good material. It’s less expensive than stainless steel or aluminum and more user-friendly for the beginner. Additionally, mild steel can easily be cut with compressed air.

As your skill level and confidence grows, you can move to the more difficult to cut metals. When you do, you’ll need to use the appropriate gasses. It’s also recommended to keep extra nozzles on hand, as they will wear out as time goes by.

CNC Plasma Cutting Making Money

People will pay high prices for precisely-cut metal parts.
People will pay high prices for precisely-cut metal parts. Source: fabricatingandmetalworking.com

A well thought-out plan is the key to making money with any hobby. Remember to factor in material cost as well as machine and design time when pricing your finished parts. CNC plasma cutters are not as common in many small shops as other types of CNC equipment, so your newfound skill can demand a higher price than many CNC-produced goods.

License: The text of "CNC Plasma Cutting – The Basics" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.

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