Laser welding: continuous and pulsed technologies

Laser welding has become a widely accepted method for joining various materials, from thin plastics to refractory metals. Its applications include the medical, aerospace, defense, energy, and many other high-tech industries. The welding process's high flexibility allows it to be used for creating microelectronic implants and welding rocket fuel tanks.
One of the first and most important questions that may arise when choosing a laser welding method is whether to use a continuous-wave (CW) or pulsed laser.

Laser welding: continuous and pulsed technologies

Laser welding today occupies a key position among modern methods for joining metals and alloys. It is used in a wide range of industries, from aircraft and automotive manufacturing to medicine and microelectronics. This technology enables high precision, minimal thermal impact, and strong welded joints. However, when selecting equipment, an important consideration is the type of laser— continuous wave (CW) or pulsed. Each has its own characteristics, advantages, and applications. In this article, we will examine the differences, operating principles, and selection criteria in detail, as well as explain where to purchase reliable laser welding equipment.

What is continuous laser welding?

A continuous-wave laser generates a constant beam of radiation. As the name suggests, the beam is uninterrupted and has a stable output. Fiber lasers are most commonly used in practice, offering high efficiency, excellent beam quality, and a long service life. They are suitable for processing a wide range of materials, from steel and titanium to aluminum and copper.

The main feature of continuous-wave lasers is their ability to achieve significant penetration depth. While many welding technologies achieve penetration depths of fractions of a millimeter, CW lasers can achieve depths of over 1.5 mm, and at high power levels, even tens of millimeters. This result is achieved through the continuous exposure of the laser beam to the material.

The power range of continuous-wave lasers is extremely wide: from 200 W to 100,000 W and more. For thin sheet materials, a few hundred watts is sufficient, while for welding thick workpieces in heavy industry, systems with tens of kilowatts are used. The choice of a specific source is always based on the material, the thickness of the parts, and the required throughput.

Continuous welding is performed at relatively high speeds—2.5 m/min and higher. This high speed compensates for the intense heat and prevents overheating of the area beyond the weld. It's important to understand that selecting power, feed rate, and focusing depth requires an individual approach; there are no universal parameters. It's precisely because of this precise adjustment that continuous lasers are used in industries where consistency and repeatability are essential.

Pulsed laser welding: operating principle and advantages

Unlike CW lasers, pulsed lasers produce a series of short pulses of radiation of a specific frequency and duration. Their average power may be relatively low, but the peak power per pulse can reach significant values ​​– often tens of times higher than the average. For example, a laser with a nominal power of 25 W can produce pulses with a peak power of up to 5 kW with a duration of just a few milliseconds. This allows for efficient material processing even with relatively low power consumption.

In this case, the weld seam is formed by a sequence of overlapping pulses. To ensure a tight and reliable joint, the pulse overlap rate should be 80–90%. This approach ensures a tight weld without defects or voids.

One of the key advantages of pulse welding is the minimal thermal impact on the workpiece. Thanks to the very short pulse duration, the material outside the welding zone is virtually unaffected by heat. This is especially important when working with thin workpieces, miniature parts, or complex-shaped components, where even the slightest thermal impact can cause deformation.

An additional advantage is the ability to process highly reflective materials, such as aluminum or copper. Continuous-wave lasers often struggle with these materials, but pulsed mode allows for this task to be handled successfully.

Continuous and pulsed lasers are used to solve various problems. Generally, several selection criteria can be identified:

·    Weld depth. If a deep weld is required, a continuous laser is preferable.

·    Process speed. For mass production, where productivity is paramount, CW welding is a better choice.

·     Precision.When spot welding and minimal thermal impact are required, a pulsed laser is the choice.

·    Materials. For aluminum, copper, and other reflective materials, it is advisable to use pulsed mode.

·    Sealing. When working with miniature parts and requiring a complete absence of micropores, pulsed lasers are better suited.

Thus, the two technologies do not directly compete, but rather complement each other. Some industries employ combined solutions, where different types of equipment are used within a single facility for different tasks.