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Laser cutting as a contact-free slitting process

Laser cutting is a slitting process with which metallic and non-metallic raw materials of different material thicknesses may be cut. This is based around a laser beam which is guided, formed, and bundled. When it hits the workpiece, the material heats up to the extent that it melts or vaporizes. In this process, the whole laser power is concentrated on one point, with a diameter that is often less than half a millimeter. If more heat is introduced into this area than can dissipate through heat conduction, the laser beam will penetrate the material entirely – the cutting process has begun. While other processes involve applying large-scale tools with enormous power to the sheet metal, the laser beam completes its task without any contact. In this way, the tool does not incur wear, and no deformities or damage to the workpiece occur.

Advantages of laser cutting

The laser cutting process

The interaction between a focused laser beam and workpiece forms the basis of laser cutting. In order for this process to be carried out reliably and precisely, numerous components and additional equipment are used on and around the laser beam, which will be illustrated in the following graphic.

Prinzip des Laserschneidens

  1. Focusing optics: lens and mirror optics focus the laser beam on the processing point
  2. Laser beam: the laser beam hits the workpiece and heats it up until it melts or vaporizes.
  3. Cutting gas: the resulting melt is blown out of the kerf using cutting gas. The gas is emitted coaxially with the laser beam from the nozzle.
  4. Drag lines: during laser cutting, the cutting edge is given a typical drag line pattern. At a lower cutting speed, these drag lines are virtually parallel to the laser beam.
  5. Melt: the laser beam – bundled laser light – is guided along the contour and melts the material locally.
  6. Cutting point: on the workpiece, the kerf is barely wider than the focused laser beam.
  7. Nozzle: laser beam and cutting gas meet the workpiece through the cutting nozzle.
  8. Cutting direction: the kerf is created by moving the cutting head or the workpiece in a specific direction.

Various applications in the area of laser cutting

Lasergeschnittenes Bauteil

Virtually no visible burr formation: the gearwheel shows the excellent part quality produced by laser cutting even in thicker materials.

Laser cutting for CFRP components

Fibre-reinforced plastics are the ideal raw material for lightweight design. However, the unruliness of the material poses challenges for nearly all tools – except the laser. Customers benefit from the speed and flexibility in shape of the laser cutting tool in prototype construction in particular.

Musterteil BrightLine fiber

From mild to stainless steel all the way to highly reflective materials ­– all industrially common materials can be processed by the laser with high levels of quality.

Lasergeschnittene B-Säule

Fast, burr-free, and in three dimensions: this is how a laser cuts hotforming components such as B pillars in the automotive industry.

Musterteile aus Buntmetallen

In fusion cutting, the laser cuts thin stainless and mild steel with a thickness from 0.5 millimeters, very quickly and cost effectively.

Lasergeschnittenes Hitzeschutzblech für Abgasanlagen

Even components which are formed three-dimensionally such as heat protection sheets for exhaust gas systems may be precisely cut with a laser.

Schneiden von sprödharten Materialien wie Glas mit dem Laser

Even brittle materials such as glass can be processed using laser cutting machines and at high speeds with mirror-smooth results – without burrs or chips.

TruLaser 3030, Spiegelkante

BrightLine fiber is a sophisticated combination of special optics, flow-optimized nozzles, and additional technical innovations. The advantage: due to the high-quality cutting edges, parts do not get caught during part removal.

Lasergeschnittene Küchenmessen

Compared to mechanical slitting processes, a laser allows household knives to be produced faster and without requiring post-processing on the cutting edge.

Microprocessing with TRUMPF products

Short and ultrashort pulse lasers cut the most intricate structures at the micrometer level quickly and cost effectively. This is how laser-cut hands for the clock industry or laser-cut implants for medical technology are created.

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All laser cutting procedures at a glance

When it comes to cutting metal and non-metal raw materials, the laser is in many cases the first choice as a universal tool. The laser beam cuts nearly any contour quickly and with flexibility – regardless of how intricate and complex the shape is, or how thin the material. In the process, various cutting gases and pressures influence the machining process and the result.

Flame cutting

For flame cutting, oxygen is used as the cutting gas; this is blown into the kerf with a pressure of up to 6 bar. There, it burns and oxidizes the metal melt. The energy generated by this chemical reaction supports the laser beam. Flame cutting allows for very high cutting speeds and the processing of thick sheet metals and mild steels.

Fusion cutting

During fusion cutting, nitrogen or argon are used as a cutting gas. This is driven through the kerf with a pressure between 2 and 20 bar, and unlike flame cutting, does not react with the metal surface in the kerf. This cutting procedure has the advantage that the cutting edges remain free of burrs or oxides, and reworking is barely required.

Sublimation cutting

Sublimation cutting is primarily used for precision cutting tasks which require very high-quality cutting edges. In this process, the laser vaporizes the material with as little melting as possible. The material vapor creates a high amount of pressure in the kerf, which forces the melt out in an upwards and downwards direction. The assist gas – nitrogen, argon, or helium – shields the cutting areas from the environment and ensures that the cutting edges remain free of oxides.

Laser precision cutting

For laser beam precision cutting, individuals bores are joined together with pulsed laser energy; these overlap by 50 to 90% and form a kerf. The short pulses create very high levels of peak pulse powers and extreme irradiances on the workpiece surface. The advantage: heating up of the component is very minimal, which allows for the cutting of even the most intricate parts without heat distortion.

Parameters which influence the laser cutting process

Focus position and focal diameter

The focus position influences the irradiance and form of the kerf on the workpiece. The focal diameter determines the gap width as well as the form of the kerf.

Laser power

So that the processing threshold – the point at which the material begins to melt – is exceeded, a specific amount of energy per surface area unit is required. This is defined as: energy per surface area unit = irradiance x exposure time on the workpiece.

Nozzle diameter

Choosing the right nozzle is crucial for part quality. The form of the gas beam as well a the gas quantity are determined by the diameter of the nozzle.

Operating mode

Continuous wave operation or pulsing – the operating mode allows you to control whether the laser energy is to hit the workpiece continuously or with interruptions.

Cutting speed

The respective cutting task and the material to be processed determine the cutting speed. As a basic rule: the more laser power that is provided, the faster the cutting can be carried out. Additionally, the cutting speed is reduced with increasing material thickness. If the speed for the respective material has been set too high or too low, increased surface roughness and burr formation can occur as a result.

Degree of polarization

Nearly all CO2 lasers deliver linear polarized laser light. If contours are cut, the cutting result changes with the cutting direction: if the light oscillates parallel to the cutting direction, the edge will be smooth. If the light oscillates perpendicular to the cutting direction, this creates a burr. This is why linear polarized laser light is often switched over to circular polarized. The degree of polarization determines how well the target circular polarization was reached, and is decisive for cutting quality. Polarization must not be changed for solid-state lasers; it delivers direction-independent cutting results.

Cutting gases and cutting pressures

Different process gases are used depending on the cutting procedure; they are driven through the kerf at varying pressures. Argon and nitrogen as cutting gas, for example, have the advantage that they do not react to the melted metal in the kerf, while at the same time shielding the cutting area from the environment.

  

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