What is CNC plasma cutting?

These blog article will explain some facts about CNC plasma cutting. PoLabs team works on project CNC plasma cutter with intention to even improve our support and make our machine shop even better also use our CNC plasma cutting equipment.

In this blog we will presented bases of CNC plasma cutting, which are very important in process of manufacturing your own machine or for undestanding how CNC plasma works.

What is CNC plasma cutting?

CNC plasma cutting is the manufacturing process of cutting the material with plasma. The CNC plasma cutting process is a very well-known manufacturing process, which is used during 1980. Plasma cutting grew out of plasma welding in the 1960s and emerged as a very productive way to cut sheet metal and plate. It had advantages over traditional cutting of producing no metal chips, giving accurate cuts, and producing a cleaner edge.

How does CNC plasma cutter work?

CNC plasma cutter machine is specifically designed to cut through electrically conductive material by using a computer to control and direct an accelerated jet of hot plasma at the material being cut.

CNC plasma cutting machines are computer-run systems that have the ability to move a high-definition plasma torch in various directions by using numerical coding(G-code) that has been programmed into the computer. The high-definition plasma cutter itself operates by forcing a gas or compressed air through a nozzle at high speeds. An electric arc is then introduced to the gas and creating a plasma that is able to cut through metal.

CNC plasma cutters are available in different sizes, prices, and functionalities. These machines are highly accurate and can cut through material up to 12 700mm/min-(500 inches/min). While high-definition cutters require gas and assist gas to function, the type of gas will wary depending on the material being cut. More about gases, it is described in one of the chapters below.

Firstly, the most important when you buy, manufacture or produce a CNC plasma cutter is electronics. Polabs – Pokeys electronics offers: USB CNC CONTROLLER for controlling all axes- (stepper motor driver), Homing sensors (switches), input/output signals, TORCH HEIGHT CONTROLLER.

Here are also blog posts that are very important, when building a CNC plasma cutter or some other project, where PoKeys electronics is needed:

Also, very important equipment on the CNC plasma cutter is plasma TORCH. Many manufacturers have had a problem with plasma torches. Why are there so many differences? These suggestions are our and customers’ experiences: Torches are different types and qualities. Quality of product is connected with price. More about quality and what you must pay attention at buying in one of the chapters below (Torch options).

CNC plasma TORCH
Plasma torch

What is a CNC plasma cutter used for?

CNC plasma cutters are used for cutting sheet metals, metal signs, metal arts, metal tubes&pipes, and other metal fabrication projects. CNC plasma cutters are also used in many workshops to create decorative metalwork. For instance, commercial and residential signage, wall arts, outdoor garden art. Plasma cutters are not only professional CNC machines, there is a lot of DIY CNC plasma cutters project, which depends on needs, workshop space, finance…

CNC plasma table build.

The plasma table builds, this is the decision that is connected with needs, costs, usage, and also space in our workshop.

On many forums, blogs, and other technical magazines we can find many options for building our CNC plasma machine. It is useful and recommendable if we check first some plans of machines on market ( professionals and DIY versions).

It all starts with the type of table, there are many options, but the most known or used are:

  • welded-heavy duty CNC plasma tables ( rigid),
  • Assembled with aluminium extruded profiles ( many types and options),
  • assembled ( tubes + sheet metal)

Those are basic versions, there are subcategories:

  • Console – one side guided Y axis,
  • both side guideded Y axis,
  • motion with spindle ( ballscrew, trapezoid),
  • motion with pinion and rack,

When we solve and select the type of CNC plasma table, then we are looking for mechanical parts and electronics.

CNC Plasma table build types
CNC plasma – some table types

CNC plasma mechanical components

CNC cutting machines have many different mechanical parts, which depend on which type of machine. The main mechanical parts of machines are:

  • rail guides,
  • precision shafts,
  • linear ball bearings,
  • ball screws,
  • support units,
  • bearings,
  • Table- frame
  • work table
  • holders
mechanical parts - CNC plasma
Some of the mechanical parts used in CNC plasma table.

Torch options

The plasma torch is one of the most important parts of a CNC plasma machine. Why? Quality of product (electrode, air diffusor, nozzle, external nozzle…), the start of cutting, cooling of the torch.

The quality of products is proven at the turbulence of air (cutting), perpendicularity of cut, cut starting. Quality products are our advantage, for that reason pay attention when buying a plasma torch.

Torch options: Short, long, angled, straight. Torches are made for both hand-held and mechanized cutting and gauging, as well as CNC or robotics cutting.

TORCH types

CNC plasma electronics

The CNC reads the part program and then outputs signals to the machine’s drive system which moves the torch in the desired direction at the programmed speed. The CNC reads the encoder feedback and makes corrections to the drive signals as required to keep the torch motion on the programmed path. All of the electronics in the CNC and drive system work and communicate very quickly, often measuring and updating position information every few milliseconds. This allows the machine motion to be smooth and accurate enough to produce plasma cut parts with a smooth, straight, consistent edge quality, and precise part dimensions.

CNC plasma electronics
Connection to HV or divided output

CNC plasma setup

For plasma setup we need some basic tools: it depends on which type of machine we are building.

Mechanical: screwdriver, different wrenches, pins, liners, measuring instruments.

electronics- electrical: multimeter, the plasma assembly products manuals.

Be careful when assembly, Safety is in the first place.

Table setup

The table is the base of the CNC machine. The surfaces and planes must be flat as possible. Because flatness and parallelism is very important if we want an accurate machine and make quality pieces and in tolerances.

Gas types

The best gas to use depends on three primary considerations: cut quality, productivity, and economy.

  • 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. For plasma cutting with compressed is important to use dryer of compressed air in compressed air system, because the water or moisture in compressed air can cause some problems at cutting.
  • Other gasses used in CNC plasma cutting are nitrogen and methane, which are most often utilized when cutting thin stainless steel.
  • AIR: Air is the most versatile plasma gas, it produces good cut quality and speed on stainless steel, steel and aluminium. Air also lowers costs because it is not necessary to purchase gases. However, air is not free. Shop air must be cleaned to remove contamination such as oil mist, moisture. Air is a good option for many shops for its versatility, good speed, low dross levels, and parts life up to 600 starts.
  • OXYGEN: Oxygen has become the standard in the industry at cutting mild steel, because it provides the best, clean-cut quality and the fastest cutting speed of any plasma gas. However, a plasma cutting aluminium or stainless steel plate with oxygen plasma gas is not recommended. The disadvantages of oxygen are the cost of the gas and the life of consumable parts. State of the art plasma oxygen systems use inert starting gases, such as nitrogen, to archive similar parts life to nitrogen or air systems. These systems have parts life in the 800-1500 start range.
  • NITROGEN: Nitrogen was used in most early plasma cutting processes. It is still the best choice if you cut a lot of stainless steel or aluminium. In general, air is the best secondary gas, when using nitrogen plasma. CO2 also works well, slightly improving the finish, cutting speed and parts life over the use of air.
  • ARGON-HYDROGEN:Argon hydrogen is the plasma of choice for thick stainless steel and aluminium cutting. The mixture typically uses 35% hydrogen and 65% argon. Argon hydrogen is the hottest burning plasma gas and provides the most cutting power. Argon hydrogen is used in water injection torches to up to 1000 amps to cut up to 6″ stainless steel. Its provides a straight cut and a smooth, almost polished surface on stainless steel. Nitrogen in usually used as a shield gas with argon hydrogen. The disadvantage of this set up is the expense.

Software

Although most CNC plasma cutters will come with their own software packages, including some form of CAD platform, others may not. On market, we have many different CAD/CAM programs. Some programs are also free.

Look carefully at the software offered by each CNC plasma table manufacturer before buying as the learning curve can differ greatly.

Many machines on the market and a major part of home build machines use MACH3 and MACH4 plasma software. Because it is open software and we configure the machine to our needs and can add some devices or sensors.

CNC plasma cutting configuration

Some affordable CNC plasma tables come without a TORCH HEIGHT CONTROLLER- THC to hit a lower price point. Don’t go this route. If you want the best plasma table, a good height control is critical to plasma cutting in terms of cut edge angularity and consumable life.

Pokeys - CNC plasma settings

2D plasma cutter

Also called flat-bed Plasma Cutting, produces flat profiles from plate or sheet, with straight cut edges at 90 Degrees to the profile surface. Typically, high-powered Plasma Cutting beds are configured in this way, giving the largest depth of cut of between 100-150mm.

3D plasma cutter

Similar to 2D Plasma Cutting, and also commonly referred to as flatbed Plasma Cutting, this variation adds a third dimension through the introduction of an angular cut or beveled edge through the sheet or plate material. Typically, High Definition Plasma Cutting beds are configured in this way, giving the greatest flexibility, accuracy, and/or speed.

Tube/section plasma cutter

The stock material and the cutting axes are the major changes and enhancements in comparison with flatbed Plasma Cutting. The Plasma Cutting Head is typically stationary whilst the section or pipe is maneuvered under the beam creating not only end profiles but slots, tags, and holes within the section or pipe.

These machines may or may not be fitted with a tilting head or 3rd axis, enabling not only the cutting of the section but the bevelling of its edges or countersinking of holes – as with the above described “3D Plasma Cutting”

Why should buy a CNC plasma cutting machine?

CNC plasma cutting machine is a very productive and cost-efficiency machine.

This ensures happy customers on your end, which often turn into repeat customers. Because you will be producing more cuts that are high in quality and retaining happy repeat customers, investing in a CNC plasma cutting system is a smart choice that will more than pay for itself in a short matter of time.

A CNC plasma machine is easy to use and requires minimal training to learn how to operate effectively. This drastically reduces onboarding costs for shops looking to hire machine operators and also provides increased accessibility for one-man shops looking to add a CNC plasma tool to their arsenal.

About

Polabs, develop and manufacture electronic products for many different areas and needs and also make some machines to make work easier, more productive and high quality. Here are some interesting projects- blog posts, please check.

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