Laser cutting | Info on laser technology

What is laser cutting?

 

Where is laser cutting used?

Due to the highly focused laser radiation and the high traverse speed, the thermal input into the material is limited to a narrowly defined area. This means that the components do not deform as much during laser cutting, which results in very high precision.

Laser cutting is mainly used in the automotive industry, in precision engineering, the semiconductor industry or by manufacturers of optical instruments. This cutting technology is used in all industrial sectors dealing with metalworking and cutting technology in general. The materials to be processed range from rubber to diamond stone. This cutting technology is mainly used for steel sheets of all types and grades, for stainless steel sheets and for non-ferrous metals such as aluminium and brass. Other suitable materials for laser cutting are titanium, plexiglass or acrylic glass, wood or bronze.

Laser cutting technology is predestined for use on a CNC cutting system. Modern laser cutting systems combine the advantages of the laser with the possibility of multifunctional processing on a CNC machine. Today's CNC lasers offer a wide range of configuration options for processing sheet metal, pipes and profiles. Thus cutting, drilling, tapping, countersinking, marking or bevel cutting – for example for weld edge preparation – is possible on one cutting machine.

 

Solid-state laser compared to CO2 laser

There are different versions of focused high-power lasers that are used in laser beam cutting. The most frequently used are the CO2 laser (a gas laser) or the fiber laser (solid-state laser). The CO2 laser is the more established cutting technology and has been used successfully for many decades. For some years now, however, the gas laser has been increasingly competing with the fiber laser. This special form of solid-state laser is particularly convincing due to its high efficiency compared to the well-known cutting system. The Nd:YAG laser, which like the fiber laser belongs to the group of solid-state lasers, is also becoming increasingly important in laser cutting. However, it is mainly used for micro-drilling and welding.

Compared to CO2 lasers (carbon dioxide lasers), fiber lasers have significantly lower operating and maintenance costs. Thanks to the most modern and sophisticated technologies, they are at least on par with established lasers in terms of precision with different material thicknesses. However, the fiber laser is being used more and more frequently in laser cutting technology and is competing with the CO2 laser. Compared to the still dominant CO2 lasers, solid-state fiber lasers score with a number of strengths – first and foremost with the cost factor. Thanks to modern and sophisticated technologies, even supposed weaknesses can be eliminated. This makes the fiber laser a more than attractive alternative to the existing system.

 

The CO2 lasers belong to the group of gas lasers and are also called carbon dioxide lasers or carbon dioxide lasers. They are based on a carbon dioxide gas mixture, which is electrically excited. CO2 lasers score with a very good cutting quality and are mainly used for metallic materials but also for non-metallic materials like wood, textiles, plastics, foils, acrylic, glass, paper and leather. In contrast to fiber lasers, carbon dioxide lasers can also be used to process even thicker stainless steel sheets with good cutting quality – even at high feeding speeds. The CO2 laser is the established laser type that has been used for decades and enables high quality with a wide range of material thicknesses. The disadvantage is the comparatively high operating and maintenance costs for the laser gases as well as for consumables working in the laser source. The efficiency is around 10 percent.

 

The fiber laser, which is a special form of solid-state laser, is on the advance. It scores with its cost-effectiveness, low operating costs and long service life of the wear parts. Thanks to a beam wavelength that is ten times shorter than that of the CO2 laser, the fiber laser is also suitable for cutting materials that are otherwise difficult or impossible for the CO2 laser to cut, especially non-ferrous metals (NF metals). For higher material thicknesses, a variable focus diameter is necessary to compete with the cutting quality of the carbon dioxide laser. The laser sources are also highly effective and consume significantly less input current for the same power. The so-called socket efficiency of the fiber laser is about 40 percent.

 

Like fiber lasers, Nd:YAG lasers are solid-state lasers and are also known as crystal lasers or vanadate lasers. Nd:YAG laser is the abbreviation for neodymium-doped yttrium-aluminum-garnet laser. A YAG crystal is used as host crystal. This technology is used less for laser cutting, but rather for engraving, welding and micro-drilling. Metals, metals with coatings and plastics are processed with this solid-state laser. In contrast to fiber lasers, however, this cutting technology has a high wearing of pump diodes. In addition, the lifetime of the neodymium-doped YAG crystal is shorter than that of the fiber laser.

 

Advantages and disadvantages of the fiber laser

The decisive advantage of fiber lasers is obvious: With this solid-state laser, up to half the costs for operation and maintenance of the CNC laser cutting system can be saved. This fact is of course significant for the increasing popularity of this technology. Not only does this cutting technology require no gases for beam paths, but the laser sources are also highly effective: the nominal power of a 4 kW fiber laser (with a cooling device) is about 14 kW compared to 57 kW for a 4 kW-CO2 laser. Several maintenance costs of a carbon dioxide laser are also eliminated: the costs that depend on the life cycle of the discharge tubes or on the turbine in the cooling circuit of the laser gases or the vacuum pump. These account for an enormous part of the comparatively high maintenance costs of the CO2 laser.

There are, however, other physical characteristics that are advantageous to the fiber laser: Thanks to a beam wavelength that is ten times shorter, fiber lasers can achieve a smaller beam diameter (i.e. a higher energy density) at the center of the cutting head – thus thin material can be cut faster than with the CO2 laser. However, the thicker the material, the more this characteristic becomes a disadvantage due to the very thin kerf and a resulting risk of kerf filling with the discharge material (slag).

It is therefore necessary to have a larger focus diameter for cutting thicker materials. In the interest of industrial use, the laser cutting head should be able to change the focus diameter automatically – without the intervention of operating personnel, e.g. by manually changing lenses. In order to meet the versatile requirements of the market – i.e. to enable cutting over the entire material thickness range – MicroStep uses laser cutting heads from leading manufacturers such as Highyag, Precitec and Thermacut, tailored to the customers' needs, for maximum productivity in 2D cutting and bevel cutting of sheet metal, pipes or profiles. Due to the possible fully automatic control of focus position and focus diameter in combination with fast focus movements on the material, materials up to 50 mm thickness and significantly more can be processed with a single fiber laser, depending on the laser source. The cutting heads do not require changing the ocular lens – only the cleaning of the protective glass is part of the operator's tasks.

The quality of fiber laser technology has improved considerably in recent years. Depending on the laser power and material, modern fibre lasers can now cut materials up to 50 mm thick and far beyond. For example, a 20 kW laser enables the precise cutting of mild steel with a thickness of more than 40 mm, stainless steel up to 40 mm, aluminium up to 40 mm, brass up to 25 mm and copper up to 15 mm. However, the available laser power is constantly increasing.

 

Cutting range

Laser cutting technology has undergone enormous development in recent years. It is still used mainly in the smaller and smallest thickness range. The cutting range in modern laser cutting is from 0.5 to 50 mm and significantly more, depending on the material and the power of the beam source, with optimum environmental variables.

Laser components

A laser consists of three basic parts:

• Energy source
• Laser medium
• Resonator

The energy source, also called pump or pump source, has the task of "pumping" energy into the system. This creates a population inversion. The source can be electrical, but also light, heat or even another laser. Sufficient energy must be transferred into the laser medium to achieve population inversion – this means that the number of particles in the excited state must be higher than the number of particles in the ground state. The light of the laser is produced by spontaneous emissium in the excited laser medium and is amplified by stimulated emission. The resonator consists of two curved mirrors, one of which is partially transparent. Radiation originating from spontaneous emission and having the correct wavelength, phase and direction is reflected back and forth between them. Part of the radiation escapes as a focused laser beam through the partially transparent mirror and the other part is reflected back for further amplification.

Laser technology

In laser cutting, also known as laser beam cutting or CNC laser cutting, the focused laser beam is absorbed at the cutting front and thus generates a melt and metal vapour which is blown away downwards by a gas stream immediately after it is generated. A cutting gap remains, which can take on any contours depending on the feed direction of the laser beam.

 

 

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Expert interview: What possibilities does laser cutting technology offer?

Interview with our two laser experts Matthias Korn and Patrick Scheuner

Table of contents

• How do you become a laser expert?
• What fascinates you about the job in Service & Support?
• Which parameters influence the quality of the cut laser parts?
• What precision can be achieved with laser cutting machines from MicroStep?
• How important is appropriate training for operating a laser cutting machine?
• What safety aspects must be taken into account when operating a laser cutting machine?
• How costly is the maintenance of a laser cutting machine?
• What service life can a company expect when purchasing a laser cutting machine?
• What options are there for automating the storage, loading and unloading of sheets?
• Is retrofitting possible if a company's requirements for the functions of a laser cutting machine change?
• What developments can be seen in the industry with regard to laser cutting machines?

You are part of the team of experts in laser cutting systems at MicroStep Europa. First question: How do you actually become a laser expert?

Matthias Korn: As far as I know, there is no direct vocational training in the field of laser machines. Of course, there were and still are physicists who have driven the development of lasers and there are now a few degree courses that deal with laser technology and the theoretical design and layout of lasers. I studied mechanical engineering and gained my first experience in the field of lasers during my practical semester and the subsequent diploma phase at a large German laser manufacturer, where I subsequently worked for many years in the application and research & development departments. In the field of mechanical engineering, a lot is still learning by doing. You have a basic knowledge thanks to your studies, but you have to acquire the rest.

Patrick Scheuner: I started out as a metalworker and became a master metalworker after my apprenticeship. In my company at the time, I operated a laser cutting system, among other things, and later also programmed it. With this prior knowledge, I was then able to delve deeper and deeper into the subject at MicroStep. Through exchanges with colleagues, with manufacturers and with many of my own tests, I gained experience and my understanding of the physical components grew. Every problem that you are allowed to solve takes you further.

What fascinates you about your job in Service & Support?

Matthias Korn: There is no foreseeable end to the development of laser technology. Since my studies, lasers and their application in industry have continued to develop. This makes the job extremely diverse and interesting in the long term.

Patrick Scheuner: Of course, this means that you are always faced with new tasks – whether in laser cutting or in another cutting technology. You are on site or in our own technology center and solve tasks, set up parameters and work closely with the operator so that the customer can ultimately work in the best possible way. Be it during commissioning, training or support. You work with customers from different industries, see a wide variety of applications, state-of-the-art technology and experience many small and large successes.

Let's take a more general look at laser cutting. Modern laser cutting systems are used for a wide variety of materials. What parameters influence the quality of the cut laser parts? Are there differences depending on the material?

Matthias Korn: A laser can of course be used to cut very different materials – there are different laser processes depending on the task. In principle, you first look at what the customer wants to cut and then select the type of laser with the right wavelength for the material group. Glass or wood, for example, cannot be cut with all laser types. The beam parameters and process parameters are then designed depending on the material group and the material thicknesses to be cut. The most important of these are the cutting speed, the focus position, the laser power and, of course, the cutting gas and the cutting gas pressure. In order to achieve the best possible results, the parameters must be adapted to the respective material or alloy.

What precision can be achieved with laser cutting machines from MicroStep?

Matthias Korn: A distinction must certainly be made here between the different types of laser cutting machines. Small precision cutting systems can achieve accuracies in the single-digit µm range, while the laser systems used in industrial production today have a higher accuracy, usually in the range of 0.1 mm and smaller, depending on the material thickness to be cut.

How important is it to train your own staff to operate a laser cutting machine?

Patrick Scheuner: A laser machine is often one of the most expensive systems in operation. Of course, the operation of such a system is becoming more and more optimized and the control systems used are becoming increasingly intelligent, but the operator still plays a decisive role in the efficiency of such a system. Due to the wide variety of applications, the best possible results can only be achieved with the right knowledge. And what could be more expensive than the machine standing still or having to rework cuts because the operator lacks the necessary knowledge.

Matthias Korn: In addition, laser systems are highly complex systems that can only develop their full potential with the right training. This includes, for example, giving the operator an understanding of the interaction between the individual components of a laser system during training, as well as explaining the individual machine and laser parameters for the cutting process.  

The topic of safety on the workplace is becoming increasingly important. What safety aspects must be taken into account when operating a laser cutting machine?

Matthias Korn: Beam protection is the most important part of a laser system. This is because the laser beam is the most dangerous component. There is also the danger posed by moving parts such as the shuttle table and the potential for injury from sharp-edged parts. At least the sharp edges are not foreign to the metalworker, even without a laser.

How time-consuming is the maintenance of a laser cutting machine?

Patrick Scheuner: The use of fiber lasers has significantly reduced maintenance times. When using a CO2 laser in a laser cutting system, the beam source is simply the most maintenance-intensive component. The fiber laser, on the other hand, is completely maintenance-free in this respect. This means that fiber laser cutting systems only require maintenance of the machine construction, axes, etc. The maintenance effort is similar to that of a CO2 laser. As with other types of cutting systems such as plasma, the amount of maintenance required simply depends on the size of the system, the degree of automation and the operating hours. We recommend maintenance every 2000 operating hours or at least once a year.

What service life can a company expect when purchasing a laser cutting machine? What factors does this depend on?

Matthias Korn: Of course, the machine equipment, care, maintenance and operating hours play a major role here. Experience shows that you can expect the machines to last between 10 and 15 years, although with good care and complete maintenance, you can produce for much longer.

What options are there for automating the storage, loading and unloading of sheet metal?

Matthias Korn: There are different variants depending on the requirements:

• The simplest variant is an automatic shuttle table that enables loading and unloading from and into the laser cabin.
• This can be expanded to include a material handling system such as the MicroSteps MSLoad, which can be used for parallel loading and unloading and also automates the feeding and removal of the sheet metal to the shuttle table.
• In conjunction with a storage system such as the MSTower, virtually unmanned production can be achieved.
• There are also solutions for the variable processing of large-format sheets and systems that enable the automated material handling of pipes and profiles.

A company's requirements for the functions of a laser cutting system can change over the years. Is it possible to retrofit the machine in this case?

Patrick Scheuner: It is certainly possible to retrofit a machine, but depending on the requirements, it is often unprofitable. If you want to cut thicker materials or significantly increase the cutting speed, you may have to replace a lot more than just the laser source. This can even include reinforcing the shuttle table, new servomotors, etc. Here it is important to analyze the individual case in detail.

Finally, what developments can be seen in the industry with regard to laser cutting machines? What are users demanding and what are manufacturers pushing for?

Matthias Korn: The trend continues towards achieving higher speeds with higher laser power and cutting thicker sheets. As a result, an ever-increasing degree of automation is also required. After all, I don't want to lose the time I have gained with a faster laser when handling parts. In addition, advancing digitalization in the sense of Industry 4.0 is a groundbreaking aspect. Everything comes together in the quest for ever more efficient production methods.

 

You might also be interested in:

• Laser cuttin wood
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• What does laser cutting cost?
• How does laser cutting work?
• Expert interview on the subject of laser cutting