1. Overview of Laser Cutting

1.1 Principle of Laser Cutting

Laser cutting uses a high-power, high-density laser beam to irradiate the workpiece. The beam melts, vaporizes, or fractures the material to complete the cutting process, as shown below.

1.2 Main Laser Cutting Modes

Laser cutting is a versatile technology with different cutting modes for various materials and applications. The main modes include gasification cutting, melt cutting, oxidation-assisted cutting, and controlled fracture cutting.

1.2.1 Gasification Cutting

In gasification cutting, a high-energy, high-density laser beam rapidly heats the workpiece and raises the material surface to its boiling point. Part of the material is vaporized, while the remaining material is expelled from the cutting seam with the help of auxiliary gas. This process removes material and forms the cut.

Gasification cutting is mainly used for brittle metal materials and selected non-metallic materials, including wood, carbon materials, plastics, and rubber. For example, the Thunder Laser Nova series laser cutter primarily uses this method because it is effective for these materials.

1.2.2 Melt Cutting

Melt cutting uses a high-energy, high-density laser beam to heat the workpiece until the material melts. At the same time, a high-pressure, non-oxidizing gas, such as argon, helium, or nitrogen, is blown through a nozzle to remove the molten material and create the cut.

This cutting mode is suitable for materials that are less prone to oxidation, as well as active metals such as stainless steel, titanium, aluminum, and their alloys.

1.2.3 Oxidation-Assisted Melt Cutting

Oxidation-assisted melt cutting uses a high-energy, high-density laser beam as a preheating source. At the same time, a nozzle directs high-pressure oxygen or another active gas onto the material as the cutting gas.

This method has two functions. First, the high-pressure oxygen reacts with the cut metal and generates additional oxidation heat. Second, the molten oxide and melted material are expelled from the reaction zone, forming the cut.

Oxidation-assisted melt cutting is commonly used for easily oxidized metal materials, including carbon steel, titanium steel, and heat-treated steel.

1.2.4 Controlled Fracture Cutting

Controlled fracture cutting is used for brittle materials. A high-energy, high-density laser beam creates a large thermal gradient and severe mechanical deformation, forming a small groove through thermal evaporation. External force is then applied to initiate a fracture along the groove and create the notch.

This method is especially useful for scribing ceramics and wafers, where precise control over the fracture process is required.

2. CO2 Laser Cutting Machine System Composition

2.1 Overall Structure of a CO2 Laser Cutting Machine

According to the relative movement between the laser cutting head and the worktable, CO2 laser cutting machines can generally be divided into three types:

• Fixed Beam: Also known as a fixed optical path system. In this configuration, the cutting head remains stationary while the worktable moves along the X and Y axes.
• Mobile Beam: Also called a flying optical path system. The cutting head moves along the X and Y axes while the worktable remains fixed. This structure supports larger processing sizes and helps save floor space.
• Hybrid Structure: A semi-fixed and semi-mobile design that combines elements of both fixed and mobile configurations, offering flexibility in precision and adaptability.

2.1.1 Fixed Beam Structure

In a fixed beam structure, the cutting head does not move during the cutting process. Instead, the worktable moves along the X and Y axes.

2.1.2 Mobile Beam Structure

In a mobile beam structure, the cutting head moves along the X and Y axes while the worktable remains fixed. This design allows for a larger processing area, reduces the equipment footprint, and usually does not require the workpiece to be clamped. It is a mainstream structure for laser cutting machines.

2.2 Laser Sources for CO2 Laser Cutting Machines

2.3 Laser Light Guiding and Focusing System

The laser light guiding and focusing system is a critical part of a CO2 laser cutting machine. It directs and focuses the laser beam accurately onto the workpiece to support stable cutting and engraving performance.

2.3.1 Function of the Laser Light Guiding and Focusing System

Precision is essential in laser cutting and engraving. The light guiding and focusing system performs two key functions:

• Guiding the Laser Beam: The system directs the laser beam to the correct position on the workpiece according to processing conditions, workpiece shape, and cutting or engraving requirements.
• Focusing the Laser Beam: The system concentrates the laser beam into a fine spot, allowing the beam to cut or engrave effectively.

2.3.2 Composition of the Laser Light Guiding and Focusing System

In a small CO2 laser cutting machine, the laser light guiding and focusing system usually includes the following components:

• Light Guide System: This part includes fully reflecting mirrors. These mirrors redirect the laser beam and guide it to the required position.
• Focusing System: This system includes focusing mirrors that converge the laser beam into a small, powerful spot for accurate cutting or engraving.

2.4 Laser Cutting Control System

2.4.1 Control System Composition

The main control objects of a CO2 laser cutting machine include the laser, the stepper motor driver in the motion mechanism, the blowing system, the exhaust fan, and the chiller, as shown below.

2.4.2 Control System Software and Hardware

The control system hardware includes an industrial personal computer, control panel, main control card, interface board, driver, stepper motor, and related components.

2.4.3 Central Controller Operation

The central controller receives operation and control commands from the computer and the control panel. It controls motor operation, manages the laser generation system, and monitors and displays various equipment states.

2.4.4 Control Panel and Supported File Formats

The control panel includes buttons for start, laser high voltage, reset, manual laser output, pause, and direction control, along with status indicators and a laser energy regulator.

The control software supports PLT, BMP, and DXF file formats generated by common graphics software. It uses a mixed vector and bitmap working mode to complete engraving and cutting tasks.

2.5 CO2 Laser Cutting Machine Sensing and Detection System

The positive and negative stroke limit system of the X-axis is shown below.

2.6 CO2 Laser Cutting Machine Cooling and Auxiliary System

The cooling and auxiliary system of a CO2 laser cutting machine includes components such as an exhaust fan, blowing pump, water chiller, and cutting platform.

2.6.1 Cutting Platform

There are two common types of cutting platforms. The honeycomb platform is suitable for processing cloth, leather, and other soft materials. The blade platform is more suitable for plexiglass, thick plates, and other hard materials.

Some equipment with higher adsorption requirements may also use a vacuum adsorption platform.

2.6.2 Exhaust Fan, Ambient Temperature, and Chiller

• Exhaust Fan: The exhaust fan helps maintain smooth ventilation and smoke extraction during cutting and engraving.
• Ambient Temperature: When the ambient temperature exceeds 35℃, the operating stability of the equipment may decrease.
• Chiller: The chiller helps ensure that the cooling water temperature does not exceed 30℃.