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Plasma cutting and CNC machining are two popular methods in metal fabrication. Although both processes essentially involve cutting through metal, their underlying principles and practical applications vary quite a bit.
If you’re stepping into the metal fabrication industry, understanding the differences between these two approaches can really help in making informed decisions.
To do so, this article compares the two methods against a set of key parameters to guide practitioners in choosing the most appropriate metal cutting method.
Overview of Plasma Cutting
Plasma cutting is a thermal cutting method that uses a high-temperature, electrically ionized gas (plasma) to melt the metal and then blow away material from the workpiece. This method is particularly suited to create flat 2D shape patterns out of thick sheets of conductive metals like stainless, copper, brass, and aluminum. Sheet metal can be cut as well, but the precision is not as good.
Plasma cutting is considered one of the fastest methods to cut metal. The cutting process may be done manually via a handheld plasma torch. Or it can be automated, as in a CNC plasma cutting machine, where the computer system controls the movement of the plasma torch.
Advantages
- Plasma can easily cut up to 150mm metal thickness
- One of the fastest cutting methods, with speeds up to 200 IPM.
- Low setup and running cost.
Limitations
- Limited to cutting conductive metals.
- Low precision than other cutting options (laser cutting)
Overview of CNC Machining
The term CNC Machining is a broader term for material removal carried via a mechanical set of tools (mills, lathes, routers, etc.). Here CNC defines Computer Numeric Control i.e. a programmed computer software controls the movement of cutting tools.
In CNC Machining, the process starts with a block of metal that is turned into the desired shape by material removal via different cutting tools. CNC machining is known for its high precision and ability to produce complex parts with tight tolerances.
Advantages
- Intricate shapes and geometries can be made.
- High precision and tight tolerances up to 0.01mm can be achieved.
- Being automated, it’s highly consistent and requires less manual intervention.
Limitations
- Higher upfront cost.
- More material wastage compared to simple cutting processes.
Plasma Cutting vs CNC Machining: 8 Differences
After reviewing the basics of both processes, it’s time to do a comparative analysis. This approach gives you a very in-depth performance review, so you can decide respective process suitability for your case.
| Plasma Cutting | ||
|---|---|---|
| Cutting Mechanism | Electrically ionized gas (plasma) | Sharp mechanical tools |
| Materials | Electrically conductive (steel, aluminum, brass) | Both conductive and non-conductive |
| Geometry | Flat sheets, simple 2D shapes | Complex 3D forms, intricate features |
| Cutting Thickness | Up to 50mm (150mm industrial) | Depth 4-6x tool diameter |
| Precision | ±1.27mm (0.25 inches) | ±0.002mm |
| Speed | Up to 200 IPM | 80-120 SFM |
| Setup Costs | $1,000-$50,000 | $10,000-$500,000+ |
| Safety Risks | Fire hazards | Flying debris, noise risks |
| Applications | Frames, Structural parts | Engine parts, medical implants, precision molds |
Process Principle
One clear difference between the two processes is their operating principle i.e. how the material is being removed in each process.
Plasma cutting utilizes an electrically ionized gas (plasma) to slice through conductive materials, typically flat sheets. When the plasma machine is turned ON, a superheated channel of ionized gas through a plasma cutter creates an electric circuit between the cutter and the workpiece (which acts grounding clamp). Compressed gas is forced through a focused nozzle at high speed which blows away (cuts) the material.
In contrast, CNC machining uses a traditional mechanical cutting approach, employing sharp cutting tools. For instance, in a milling process, a solid block of metal (referred to as a workpiece) is clamped onto the machine bed. A rotating cutting tool moves along predefined paths to shape the workpiece into the desired geometry. The cutting tool carves away material layer by layer until the desired shape is achieved.
Material Compatibility
Plasma cutting works only with electrically conductive metals like steel, stainless steel, aluminum, brass, and copper. This is because the process relies on creating an electrical arc to generate plasma for cutting.
Whereas, CNC machining isn’t limited by the material’s conductivity. It can handle all metals suitable for plasma cutting and extends to non-conductive metals (tungsten, titanium), plastics, and ceramics.
Material geometry is different too. Plasma cutting primarily involves flat metal sheets or simple shapes that need linear or curved cuts. CNC machining, however, starts with a solid block of metal, which is shaped into intricate three-dimensional forms with precision and detail.
Applications
It’s easier to follow the application once you understand the material compatibility and specific geometry supported by each process.
Plasma cutters are primarily used for creating 2D profiles from flat metal sheets or simple geometric shapes. Although some plasma cutting systems can perform bevel and angled cuts, their complexity is far lower compared to what CNC machining can achieve. Typical applications are:
- Fabricating parts for metal frames
- Structural components
- Automotive repairs
- Artistic metal designs
In comparison, CNC machining is highly versatile and capable of producing complex 3D geometries, internal features, threaded holes, and multi-axis contours. Modern 5-axis CNC machines can accurately create almost any surface or intricate feature.
Common applications of CNC machining are:
- Aerospace components
- Medical implants
- Automotive engine parts
- Custom tooling
- Precision molds for industrial production
Cutting Thickness
Since plasma cutting works with flat sheets, the maximum cutting thickness is easier to define. Most standard plasma cutters handle up to 50mm, though some industrial systems claim to cut as deep as 150mm.
In CNC machining, we talk about thickness as the depth of cut. For milling operations, the depth of cut is usually four to six times the tool diameter. For example, with a 4mm cutting tool, the depth of cut can go up to 16 to 24 mm, depending on the material and the operation.
Precision and Speed
Among the two processes, CNC machining is the most precise one – it can produce parts with tolerances as low as ±0.002mm. However, plasma cutters have a significantly larger kerf with compared to other thermal cutting methods (like laser cutting). Their tolerance level goes up to ±1.27 mm (0.25 inches).
About the speed, overall, plasma cutting is faster than CNC machining because the tool has to move in one direction and just perform the cutting job. Whereas, the CNC machine may have a tool with motion in multiple dimensions.
Technically, the speed of plasma cutters is described in inches per minute (IPM). It defines how fast the plasma torch moves across the metal sheet. Plasma cutting speeds go as high as 200 IPM. In CNC Machining, the speed is usually defined in surface feet per minute (SFM) i.e. how fast the surface of the workpiece moves past the cutting edge of the tool. On average, the machining speeds are 80 to 120 SFM.
Setup Costs
Plasma cutting has lower initial setup costs compared to CNC machining. A standard handheld plasma cutter is available between $1,000 to $3,000, while high-end industrial plasma systems with automation can cost up to $20,000 to $50,000. The additional costs include consumables like electrodes and nozzles, along with safety gear.
CNC machining setup costs are quite high. A basic CNC milling machine starts at $10,000 to $50,000, while advanced multi-axis machines can range from $100,000 to over $500,000, depending on the number of axes and precision they offer. CNC operations also require tooling, software licenses, and skilled operators, all adding to the cost.
Safety Risks
Both processes have their safety risks, but plasma cutting requires more stringent precautions for several reasons. First, in its manual variant, the operator holds the torch directly, requiring face shields, safety glasses, and flame-resistant clothing to protect against intense heat, sparks, and potential UV radiation. Next, with high voltage involved, the process generates electric sparks, posing a constant fire hazard – even in automated systems – if flammable materials are nearby.
In CNC machining, although the process is fully automated, the cutting action produces chips and debris that can fly off at high speeds, which makes safety goggles necessary. Moreover, hearing protection is also recommended to mitigate the noise generated by high-speed machining operations. Proper ventilation is the key to both processes.
How Richconn can Help?
If you’re looking for reliable CNC machining services, whether it’s CNC milling, turning, or 5-axis CNC machining, Richconn is one of the leading machining services providers in the world.
Our ISO 9001-certified facility ensures quality at every step. We offer short lead times and handle a wide range of materials, including all common metals and plastics.
Have questions about the right machining process for your project? Our experienced team of engineers and machinists is ready to assist you. Contact us today and bring your product ideas to life with Richconn CNC!
