In the production process of enterprises, especially in the manufacturing of structural components, the first step is raw material cutting, also known as blanking. There are various blanking methods, including band saw cutting, shearing with a guillotine, wire-cut electrical discharge machining, punching and shearing with a punch press, oxy-acetylene flame cutting, plasma cutting with a plasma machine, laser cutting with laser equipment, and water jet cutting with high-speed water jet machines.
Now, let’s briefly discuss the application range and fields of various cutting equipment. Today, we will introduce CNC flame and plasma cutting machines, which are the most widely used equipment in the structural component production field.
In the past, blanking mainly relied on manual cutting using oxy-acetylene torches. This method had low efficiency, poor cutting accuracy, and high material waste. As production methods improved, profiling cutting machines emerged, enhancing cutting accuracy and efficiency. However, each cutting part required a template, which increased time and cost. With the advent of CNC equipment, these cumbersome and wasteful processes have been eliminated.
CNC cutting machines use computer-aided design (CAD) to generate automated cutting programs. These programs control the cutting trajectory, improving precision, efficiency, and material utilization through automatic nesting and layout optimization, significantly reducing raw material waste.
CNC cutting machines are generally classified into portable, cantilever, tabletop, and gantry types. The choice of machine depends on factors such as material size, composition, production environment, and factory conditions. Standard CNC cutting machines are equipped with flame torches, plasma torches, or both, with some also featuring laser torches. Today, we will focus on the first two, leaving laser cutting for another discussion.
Differences Between Flame Cutting and Plasma Cutting
Flame Cutting Flame cutting is primarily used for carbon steel plates, which are the most commonly processed materials. The cutting thickness can be adjusted by regulating the oxygen-acetylene gas flow, allowing for cutting carbon steel plates up to 200mm thick. This process heats the material to its melting point and then uses pressurized gas to blow away the molten metal, achieving cutting. However, this method creates a large heat-affected zone around the cut, altering material properties (such as hardening near the cut surface). It can also cause thermal deformation in thinner materials, making secondary machining difficult. Therefore, flame cutting is generally not used for materials thinner than 6mm or for components requiring further machining. For these cases, alternative methods like shearing, band saw cutting, or wire-cut EDM are preferred. If the material is thinner than 6mm, plasma cutting or other cold-cutting methods are recommended.
Plasma Cutting Plasma cutting has a broader application range than flame cutting, as it can cut almost all metal materials. Air plasma cutting machines use compressed air as the working gas and a high-temperature, high-speed plasma arc as the heat source to locally melt the metal, with high-speed airflow removing the molten material to form a narrow cut. Plasma cutting produces smoother and cleaner cut surfaces than flame cutting. Due to its smaller heat-affected zone, it has minimal impact on material properties.
Given these advantages, why isn’t plasma cutting universally adopted? The primary reasons are the high cost of plasma power supplies and consumables compared to flame cutting. For general production needs, flame cutting remains the preferred choice. In most structural component manufacturing, post-cutting welding is required, so cutting surface quality is not a critical factor. However, when processing non-carbon steel materials, requiring high-quality cuts, or cutting carbon steel thinner than 6mm, plasma cutting becomes necessary.
Key Considerations for Plasma Cutting
The most critical aspect of plasma cutting is selecting the appropriate plasma power supply. Common choices for CNC plasma cutting machines include imported brands like Hypertherm (USA) and Kjellberg (Germany), as well as some Taiwanese brands like Everlast. Domestic power supplies are generally not recommended due to stability concerns, which can affect CNC machine automation and production efficiency.
Selecting a CNC Flame and Plasma Cutting Machine
When choosing a CNC cutting machine, the following parameters should be determined:
- Material type, thickness, and sheet size.
- Required cutting precision and surface quality.
Based on this information:
- Choose between portable, cantilever, tabletop, or gantry-style machines depending on material size.
- Decide between flame or plasma cutting based on material type and thickness.
- Select the appropriate plasma power supply based on cutting requirements and surface finish standards.
Plasma power selection is generally determined by the material thickness, ensuring optimal cutting performance for specific applications.
