This primarily discusses sealed-off carbon dioxide laser tubes. A sealed-off tube refers to a laser tube where the gas inlet of the glass tube is sealed, meaning it's a disposable tube that doesn't require gas replenishment after removal. These tubes are inexpensive, widely used, and popular, commonly used in laser cutting machines for non-metal cutting.

It generally consists of a glass tube shell, lenses, electrodes, water cooling jacket, tubing, and high and low voltage wires.

The glass tube body is a finished product provided by the tube shell manufacturer. Key specifications include wall thickness, length, diameter, discharge tube material, inner diameter straightness, tube mouth diameter, and electrode connection method.

Lenses are available in both imported and domestic varieties from multiple suppliers, and the quality is generally reliable. Problems are infrequent; only a small number of materials with poor heat dissipation may exhibit cracks at the lens output due to dust accumulation and high temperatures. Imported materials have higher purity and lower absorption, resulting in less heat generation and generally a few watts higher power than domestic ones, but at a higher price.

Electrodes typically use oxidation-resistant metal materials or pre-oxidized metal materials. In short, they cannot react with gas ions due to high temperatures, as this would quickly consume gas, leading to an imbalance and power reduction. In the past, nickel was used for electrodes (like nickel wire in electric furnace filaments), which could withstand high temperatures in air for a long time. However, this proved unsuitable for laser tubes, lasting only a few thousand hours, supposedly due to the formation of nickel carbonate. Therefore, other metals were adopted; gold or gold plating would be ideal, but the cost is too high.

Water cooling jackets are manufactured and supplied by specialized manufacturers, available in glass, ceramic, plastic, brass, aluminum, etc. Their main purpose is to cool the lenses; as long as they don't leak and maintain high-voltage insulation, they are suitable.

The tubing should be industrial silicone rubber that resists aging, and the high-voltage wire must withstand more than 40KV, with 50KV being optimal, as the current is only tens of milliamps, a small wire cross-sectional area is sufficient. The ground wire similarly needs more than 0.5 square millimeters.

The manufacturing process generally involves the following steps:

1. Rough grinding of the tube mouth: The grinding surface should be as perpendicular to the discharge tube as possible to facilitate subsequent fine grinding. Otherwise, it will be difficult to find the crosshairs in the optical path, making manual grinding extremely difficult. The grinding equipment can be simple or complex; generally, it needs to be custom-made or self-made, as long as it is convenient to use and effective.

2. Tube cleaning: The purpose is to remove dust from the tube shell, as dust is fatal to the aging and damage of the tube. The finished tube must be dust-free. Special cleaning agents are used for glass cleaning, and cleaning equipment is usually custom-made for convenience.

3. Electrode fabrication and installation: This step typically uses a spot welder, not a common type, but a specialized one, mainly produced in one location domestically. Electrode installation must be secure to prevent arcing and overheating, which can damage the tube. It also cannot be loose. If the electrodes are found to be unconnected after the lens is attached, it must be disassembled and reinstalled.

4. Coating: Coating can increase lifespan and improve the discharge cavity reaction mechanism. The detailed principle is omitted here as it is industry-specific technology and cannot be publicly disclosed. Coating equipment is usually custom-made or self-made.

5. Lens attachment: Place the tube shell on the work stand, use a special telescope to align the telescope axis with the discharge tube axis, find the crosshairs of the rear mirror, and then manually grind and correct the mouth according to the crosshair offset until it coincides with the origin. Clean the tube mouth, clamp the lens, seal with special sealant, heat the tube mouth to facilitate sealant penetration, then grind the optical port, attach the new output lens, apply sealant, heat and penetrate, wait a few minutes to check for stability and deviation, carefully remove it from the stand, place it on a special tube rack, and then attach the next one.

6. Gas filling: Place the tube on the gas filling station, connect the gas filling port and the gas filling interface using a special torch, evacuate to below 10⁻³ Pa, use helium gas to clean the tube, evacuate again to below 10⁻³ Pa, and then fill the pre-mixed gas. After filling to the pressure matching the tube shell type, close the gas, test the power on the gas filling station, observe the effect, remove the qualified ones, troubleshoot and correct the unqualified ones and refill them, and remake the ones that still fail.

7. Water cooling jacket installation, debugging, and packaging: Not all tubes use water cooling jackets; those with lenses that don't generate much heat can use natural cooling. After attaching the front and rear water cooling jackets, debug, wipe, label, and package. Find the angle with the highest power, attach the directional label, and pack for storage.

Manufacturing carbon dioxide laser tubes is a specialized technology involving multiple process points. The same CO2 laser tubes on the market vary in durability and usability; the difference lies in the control and handling of process points, including imprecise production processes, failure to grasp key points, and poor gas formula optimization.