In the last few years, laser-based processes have found application in nearly every sector. Practically every machining operation, that has traditionally been performed by mechanical tools, finds a laser equivalent. Lasers can currently cut, weld, drill, heat treat, kiss cut a very wide range of materials.

For the industrial sector, CO2 laser sources are widely adopted. The features of their laser beam make them suitable for a great variety of manufacturing applications and materials. A CO₂ laser is definitely what you need if you are considering switching to a laser based production process.

But what are the advantages of adopting a laser system and in particular a CO2 laser? How can it improve the productivity of your lines? Let’s make this clear using the example of laser cutting.

1. You won’t need strong fixturing

Since CO2 laser cutting is a non-contact process, you need no strong fixturing to keep your material centered on the working area, as in conventional machining. In CO2 laser based process, no mechanical forces are implied: the laser head will deliver the laser beam where required.

This feature will speed up the transition from part to part or between sheets of different materials through a production run. In a small amount of time you will be able to cope with different design patterns for both additive manufacturing or fabrication.

2. Cutting flexible materials will be a joke

The absence of touching parts and strong fixturing speeds up the cutting operations of flimsy materials like paper or plastic film. When performing a cutting procedure, a laser beam is as sharp as a scalpel. Forget the fear of accidental distortions or cracks: a laser beam won’t push on objects with which they come in contact. Hence a CO2 laser will be suitable for both soft and hard materials.

3. Computer is on your side

Computer numerical control (or CNC) will give you a complete control of essential parameters such as the kerf and direction of cut. Thanks to the narrow cutting kerf allowed by CNC CO2 laser cutting you will obtain the most intricate and beautiful design patterns.

4. Reduce the wastage of material

This means that you also will be able to make the most of your base material. It will be easy to optimize the arrangement of the figures to be cut out from the surface, so as to minimize the wastage of the base material and optimize your ressources.

5. A slight heat affected zone means that your material will be safe

Laser cutting processes like CO2 laser cutting use the energy and heat conveyed by the laser beam to cut through a material. You might think that such a process would damage material as delicate as paper, plastic film or cardboard. Actually, the heat affected zones are so small that laser cutting operations are perfectly suitable for heat sensitive materials.

6. Cutting operations will be done at the speed of light

A CO2 laser cutting system is very fast. It takes only a few instants to cut even the most intricate and arbitrary contours from a sheet of various materials.

7. Perfectly refined and uniform parts

Lasers are so precise that they cut through without leaving any imperfection. Your produced parts will be perfectly and completely refined and uniform.

8. Minimize tooling costs

A great advantage of CO2 laser cutting over mechanical machining is that there is virtually no tool wearing. A laser beam will always be a sharp cutting knife, producing clean, smooth, round edges. Needless to say, tooling costs will be dramatically reduced, especially in sectors that process very tool consuming materials (e.g. abrasive materials and sand paper production).

In conclusion, laser based machining processes are fast, reliable and cost effective tools for your production lines. They allows great flexibility and repeatibility of the process, ensuring small to no variations between the parts. Switching to a laser cutting system will dramatically improve your productivity rate and make your work more easy and fast.

Let’s continue exploring the applications of CO2 lasers. In this article we will be talking about acrylic and CO2 laser.

Acrylic, also known as PMMA or plexiglas is one of the plastic materials that can be laser processed with success. In particular, CO2 laser is the right to do the job.

What is acrylic and why it is so successful

Acylic was discovered in the 1920s. However, the material only really gained ground only after WWII as a cheap and effective replacement to glass. Easy to manufacture and process, rugged and flexible, acrylic has imposed itself as a successful material for a wide range of uses.

CO2 laser and acrylic

Acrylic is also known as PMMA. This acronym stands for Poly Methyl Methacrylate and refers to its chemical formula which includes atoms of carbon. For this reason acrylic materials responds very well to the wavelength of CO2 laser, which is 10.6 micrometers. At this wavelength, acrylic is opaque to CO2 laser, which is therefore absorbed very well by the material. This feature, coupled with low thermal conductivity and a relatively low sublimation point (300 °C), allows acrylic processing to be done quickly and easily. As a matter of fact, the fabrication of acrylic materis is one of the applications in which CO2 lasers give the best results.

Laser cutting acrylic

The main laser processing technique for acrylic is probably laser cutting. As se we have seen, the interaction between the laser and acrylic is very efficient. That means that when a CO2 lasers interacts with an acylic surface, the latter absorbs a large part of the energy conveyed by the laser, which is focused then on a tiny spot.

High energy on a very small surface means instantly vaporizing the material and as a result we obtain the cut. This process is called by sublimation of the material. Sublimation causes the material to evaporate and therefore does not create residues, making laser cutting an extremely clean process.

The end results of this process is extreme precision and quality. The cut has clean and smooth straight edges that don’t require further finishing.

The acrylic laser cutting process is also incredibly fast. Speed ​​is related to the thickness of the material and the power of the laser source. But whatever the thickness, the processing speed will be significantly higher than the mechanical cutting methods, even if it is a CNC method.

The possibilities of laser machining are endless and, ultimately, only limited by the designer’s imagination.

Do you need a laser cutting system?

At El.En. we have a long experience in producing laser systems for the fabrication of acrylic. We can design complete laser system or integrate our CO2 laser in existing laser. For whatever request or question you might have just contact us!

Modified atmosphere packaging, follows unique dynamics that you do not find in regular packaging supplies. It requires a precise regulation of parameters such as gas mixture and gas exchanges. It must take into account the fact that fresh products continue to exchange gases even after being put into the package. Laser technology is perfect tool to control those parameters through the manufacturing micro perforated packaging.

The domain of flexible packaging

Plastics polymers are used a lot in the food packaging industry, most successfully for fresh produce. Their versatility and resistance to chemical agents make them perfect for this type of application.

Their high capacity for transpiration makes them ideal for fresh produce. Every material, has its own natural traspirability that is its permeability to different types of gas molecules, particularly oxygen, carbon dioxide and water vapour.

This particular characteristic is fundamental for the conservation of fresh produce. The metabolic processes aren’t interrupted once the produce is picked. Processes such as cellular respiration and maturing, continue even after the produce has been packaged. If not appropriately counteracted, these processes can be responsible for a fast deterioration of the product. This is the reason why one of the biggest challenges of the fresh food industry is to slow down the metabolic processes that make the product unfit for consumption.

Packaging technology has found different solutions to circumvent the problem of produce deterioration. Disinfecting treatments, both chemical and mechanical or antifungal, go hand in hand with protective barriers such as plastic film.

Great progress has been made after the introduction of produce packaging in controlled atmosphere. This process takes advantage of the high transpirability of plastic film. The driving principle is to find the right balance between the gases within the packaging in order to counteract the deterioration process. Because every type of fresh produce has different metabolic processes going on, it is fundamental to choose the appropriate type of film that allows the best exchange of gas between the inside of the packaging and the outside.

Unfortunately, many films don’t enable the right relationship between the gas entering and exiting the packaged product. What can be done, then? Laser microperforation can solve the problem. It makes it possible to make microscopic holes on the surface of the plastic film. Depending on the size of the perforations (that can range between 50 to 200 micrometers), it becomes possible to control the gases that go in and out and therefore maintain the right balance between gas and humidity within the packaging.

The advantage of this type of process is that it is easily integrable in a controlled atmosphere produce packaging plant. Let us imagine a company that deals with different types of produce. Each one needs to be packaged according its own specificities. The packaging has to be tailored to each product in order to have the right balance of gas inside the packaging. Laser technology allows for the optimisation of the entire production cycle. Each type of produce can be packaged without any change of machinery; a simple reprogramming of the laser control software is all that is needed.

The food industry has long been experimenting the use of thermoplastics for food packaging. Materials such as polyester are easy  to  manipulate and inexpensive. Plus, the fact that they are sterile, strong and waterproof make them ideal for the packaging of fresh or ready to use food products.

In this article we will discuss how to seal plastic containers using a CO2 laser scanning process. This technique can substitute the traditional mechanical application based of heat and pressure. It becomes possible to notably speed up the sealing process, increase its flexibility and reduce the consumption of resources.

The packaging of food products

Traditionally, food containers are sealed by applying heat and pressure to a thermoplastic sheet. The machines used for this process are very bulky and require strong fixturing of the containers to be processed. They have to be kept perfectly still while the sealing head applies pressure and heat to the plastic film in order to seal the container.

This process has some limitations. Since it is above all a mechanical process, the parts that come into contact with each other get worn with time and have to be replaced. The tools have to be tailor-made to adapt to each type of container which makes the production line hard to change quickly. These types of machines require constant cleaning and maintenance. Finally, one needs to consider the cost of stocking and upkeeping the various pieces of machinery.

Nowadays, this type of production is hard to sustain. Flexibility and speed of execution are determining factors that will allow a company to promptly take on the changing requests of the market. The CO2 laser sealing makes it possible to overcome the previously mentioned inconveniences as well as seal plastic containers in a fast and flexible way.

How does laser sealing of food containers work?

In a laser sealing process, productivity is key. A high powered laser source that works in tandem with a highly performing laser scanning head allows for high production rates. The laser source produces the beam that generates the necessary energy and heat to seal the thermoplastic sheet to the container. The higher the power of the laser source, the shorter the production cycle.

A scanning head directs the CO2 laser exactly where needed. A highly performing laser scanning head has galvanometer mirrors with very high angular velocity, that ensure an instant response and therefore a fast production process.

Thanks to this system, the laser doesn’t only do welding: the same source can be used to finish off the product, for example, cutting off the parts that exceed the size of the container.

This process is very versatile and suitable for every type of container. It is particularly useful for multi-compartment containers. As opposed to mechanical processes, laser welding is contactless and therefore a completely sterile process which makes it perfect for the food industry. There are no costs related to maintenance or the deterioration of tools and it isn’t necessary to change any machinery pieces for different production runs. The process is fully computerised and the change of production is practically instantaneous.

In conclusion, the use of the CO2 laser for the sealing of food containers is a fast and flexible process. It makes it possible to take full advantage of the company’s resources.

Laser drilling consists of creating micro-holes on various types of materials. It is one of the first applications of laser for material processing.

The technique is based on the sublimation process by a focused laser beam. The laser concentrates the energy on the surface of the material, making it pass instantly from a solid state to a gaseous state. In fact, the material is vaporized and what remains is a perforation of the desired measurements.

Types of laser perforation

There are different types of laser drilling. Some are cleaner or more efficient than others.

single-pulse drilling: a single pulse creates the hole. This technique makes it possible to make holes smaller than a millimeter on materials up to 1 mm thick

double-pulse drilling: works like the previous one, but in this case the hole is created by two pulses in rapid succession

percussion drilling: the hole is created by sending multiple laser pulses on a single point

trepanning: the laser beam follows the perimeter of the hole to be made. This type of processing allows for larger holes – smaller than 3 millimeters – to be made on materials less than 3 millimeters thick

helicoidal drilling: the laser moves in a spiral starting from the center of the hole and progressively removes material as it travels. This technique allows you to create small holes on materials as thick as 25mm

The type of application and processing will depend on the intended result and type of material used.

Laser drilling advantages

The drilling of materials with traditional methods, is a slow and delicate process. When carried out mechanically the risks range from breaking the material (in cases of fragile materials such as ceramics) to the impossibility of precisely controlling the characteristics and distribution of the holes.

Yet, laser drilling is a non-contact method and therefore many of the typical disadvantages of traditional processes can be overcome.

The advantages of laser drilling are numerous:

• It creates very quickly a great number of holes
• It drills any material (however hard) capable of absorbing the laser radiation
• parameters such as shape and size of the holes can be tightly defined
• the material can be pierced at almost any angle
• the processing speed is very high
• the hole tapers can be controlled in a very precise way
• the density of the holes on the surface can be definined precisely
• processing waste are eliminated

In which sectors is laser drilling used?

Laser drilling is used in a wide variety of sectors. The ability to control the shape, size and number of holes per unit area has made it very popular. Here are some examples.

As a first example of application, we can cite is the manufacturing of acoustic panels. By varying the laser parameters it is possible to make sound-absorbing panels perfectly calibrated to the frequency that needs to be absorbed. With the same processing it is thus possible to create panels for every application, from the automotive sector (panels that absorb engine noises) to architecture and decoration (panels to optimize the acoustics of concert halls and other public spaces).

Another very useful application is the manufacturing of micro-drilled plastic bags for produce packaged in a modified atmosphere. If properly made, the holes make it possible to optimize the gas exchange between the inside and the outside of the packaging and therefore considerably extend the shelf-life of these products.

Which materials can be subjected to laser drilling

Laser drilling can be performed on a great number of materials. CO₂ laser, which works with both metals and non-metals, is particularly versatile. Here is a list of materials that can be laser drilled:

• paper
• cardboard
• acrylic plastic
• plastic film
• wood and plywood (mdf)
• ceramic

Examples of laser drilling

Which sources are suitable for laser drilling

CO₂ laser sources are best suited for laser drilling on non-metallic materials and on some types of metals. Their wavelength makes them very versatile and flexible for a large number of applications.

If you are considering to start a production based on a laser drilling process, you can contact us. Our expert will be happy to give all the information you need to find a laser material processing solution.

Laser magnet wire stripping is one of the many applications of the laser ablation process. This process is used in the most technologically advanced sectors. In contrast to conventional stripping, laser stripping works precisely and selectively. This makes it ideal for sectors where precision and quality workmanship are necessary.

What is a magnet wire?

A magnet wire, enamelled wire or winding wire is a copper or aluminium wire covered with a thin insulating layer. Its main field of application is in the production of conductive material coils. As you can imagine, the insulating layer is used to prevent the coil from short-circuiting simply by contact between the wires.

In order to do this, manufacturers immerse the conducting wire in a bath of polymeric material which completely covers it. The thickness of the insulating layer can range from 0.08 mm to 1.6 mm. Depending on the temperature at which the enamelled wire is to operate, the insulating layer can be made of different materials. The most commonly used materials are polyester, polyurethane and polyamide, in various formulations.

The enameled wire stripping process

Enamelled wire coils have a wide range of applications. These components are fundamental in the production of devices such as inductors, transformers, electromagnets, pickups, actuators, etc. In some cases, manufacturers may need to remove all or part of the insulating layer. One reason, for example, might be to solder the coil to larger components, or to make special connections in the circuit. To achieve these results, the enamelled cable must then undergo stripping operations to remove the insulating layer and enable it to operate.

The stripping process can be done using four techniques:

• Brushing
• Chemical process
• Stripping with blades
• Thermal process

Let’s go over them one by one.

Brushing

This technique uses rotating fibreglass or steel brushes. The fibreglass brushes rotate at high speed, produce friction and thus heat, and the heat melts the insulation layer. A smooth and polished surface is achieved.

The rotating steel brushes work thanks to the sharp action of the steel bristles. The result is a rougher surface. Because the brushes have a greater abrasive effect, they are used for larger surfaces where greater force is required for welding.

Chemical process

This technique involves immersing the enamelled wire in a chemical bath with a solvent action which dissolves the insulating coating. The coil is then cleaned to remove oxides and any residue.

Stripping with blades

This type of stripping uses rotating blades which, by moving at high speed, remove the insulating layer from the electrical cable.

Thermal process

In the thermal process, heated blades are used to melt the insulating layer. The heat combined with the movement of the blades removes the insulating layer from the enamelled wire.

The laser magnet wire stripping process

Laser stripping of enamelled wire is a viable alternative to these techniques. In this application, a laser ablation process is used to remove the insulating layer from the surface of the electrical cable.

The laser easily interacts with thermoplastic polymers. Compared to traditional removal methods, the laser has some important advantages:

• It is selective, the laser only interacts with the polymeric material and not the metal.
• It is precise, the laser can intervene extremely precisely on specific points on the surface.
• It is a green, unlike other techniques, laser stripping does not produce any processing residue.

All these advantages make the laser stripping technique ideal for cases in which material removal needs to be done in an extremely precise manner, typically in high-tech applications.

Contact us

Would you like to develop a laser stripping application for enamelled wire? Contact us: our engineers will study the right application for your needs!

Bags and pouches of all kinds have been conquering the packaging market for several decades now. Flexible packaging adapts to the shape of the object it covers, so less material gets wasted. Laser perforation, also known as laser drilling, is a processing technique that allows the manufacturing of new packaging designs that at the same attract the eye and have advanced functional features. Laser perforation is but one of the many processing technique that can be employed in packaging manufacturing through laser.

In general, the great success of flexible packaging is due to its functional characteristics. The main functions of packaging are to first protect and preserve products, and second, to facilitate sales. Flexible packaging perfectly fulfills both functions in a terrific way. Not only does it protect the product from external influences, but it can also be easily processed to give it the shape that best enhances the product’s characteristics.

Here are some examples of the wide variety of shapes and configurations flexible packaging can have:

• stand-up doypack pouches
• heat-sealed plastic bags
• envelopes for product samples used for promotional purposes
• pre-printed plastic film reels

Packaging of this type is employed in various industrial sectors. The food industry is one of the ones that makes the most common use of it. Flexible packaging provides the delicate products of this industry with an optimal balance between weight, protection, hygiene and functional and commercial characteristics. Other sectors such as cosmetics, health care and detergent industries also make extensive use of them.

The materials used to produce these forms of packaging fall into into 3 basic families:

• plastic film – Polyethylene and polypropylene are the main thermoplastic polymers used, they provide high insulation properties
• aluminium foil – Aluminium foil is used when high protection against light or temperature changes is required
• polycarbonate – These are created by combining materials from the previous two families to combine the advantages of both materials

Laser perforation for flexible packaging

As we have already mentioned, flexible packaging has found widespread use in the food sector in particular. As more and more people live in cities, work and have little time to cook, the demand for fresh, ready-to-cook food has increased.

This type of packaging is used the most for products such as vegetables. In the fresh produce section of supermarkets, bagged vegetables have become the norm, and a convenient solution for people who want to eat vegetables but have no time to prepare them.

The challenge for producers here is not only to adopt sustainable packaging but also to maximise the shelf life of their products.

After being harvested, fresh food goes through a series of biological transformations that manifest themselves in the release of gases, water vapour and chemicals inside the bag. As a result, unsuitable conditions for product preservation are created inside the bag.

What is laser perforation?

Laser perforation makes it possible to overcome this problem. The creation of holes in the surface of the wrapper makes it possible to optimise the gas exchange between the inside and the outside environment. It then becomes easy to maintain the optimum conditions for better product preservation.

This technique is part of laser cutting processes. In this application, laser technology is used to create holes in the material. The most remarkable aspect of this process is that it makes it possible to define the characteristics of the holes very precisely, from their diameter to their shape. This gives this process a considerable advantage over conventional packaging methods. Whereas previously a manufacturer had to find the most suitable packaging already available on the market, with laser perforation they can customise the packaging to ensure optimum product preservation.

The advantages of laser perforation

Compared to traditional perforating methods for flexible packaging, laser perforation provides a number of advantages:

• Precision: like all digital processes, laser perforation offers all the precision given by the use of software. The size of the holes can therefore be changed according to a wide range of parameters, even during the same process.
• Protection of materials: laser technology minimises the possibility of accidentally damaging the material from which the plastic film is made.
• Automation possibilities: laser perforation is a fully automatable process. It can be incorporated into existing production processes in order to fully automate and increase the manufacturing quality of the whole production line. It can be used for roll-to-roll or sheet-to-sheet processing.
• Flexibility: different processes, within the same production cycle, can be performed with laser technology. The same machine can perform more than one process, like for example, perforating plastic film and marking information for product traceability.

What materials can laser perforation be performed on?

The best results in laser perforation are obtained with plastic film. Most thermoplastic polymers absorb the radiation of the CO₂ laser well and therefore lend themselves perfectly to this type of processing. As we have seen, polyethylene and polypropylene are the materials on which the best results are obtained. On these materials, the cutting edges are perfectly defined, the processing precise and clean.

How a laser perforation system works

Choosing the right laser perforation system amongst the wide range of options on the market depends on the material used, the type of application and the final purpose of the project. However, we can identify some constants in all systems.

A laser perforation system normally consists of 2 components:

• a CO₂ laser source: this is the device that produces the laser beam. You can find laser sources with different power options in the El.En. catalogue.
• a scanning head or focusing head: the laser scanning head is the device that moves the laser beam over a surface. In this way, perforations can be distributed over the surface according to production needs. This smart tool uses integrated control software and can follow any type of pattern. For simpler machining operations, this system can be replaced by a focusing head, which does not have a control system but allows the laser beam to be focused on a specific point that can be moved on one or two axes depending on requirements.

This combination of basic elements can be integrated into an infinite range of systems, from industrial in-line systems to stand-alone machines that do the processing independently. Laser systems can act on moving material from reel to reel or on sheets of material.

Contact us

The possibilities of laser perforation are endless. This article only covers one of the many possible applications. This technique can be used to create filters, disposable packaging, and packaging with particular and perfectly defined functional characteristics. Each application has its own peculiarities. Our job is to find the laser solution that gives you the best results for your application. If you think laser perforation might be right for you, send us a message and we will be happy to help you identify the best laser solution for your needs.

CO2 laser and fiber laser are the two most widely used types of laser in the industry sector. Both technologies have proven to be reliable and efficient. They offer high productivity, flexibility of application and accuracy of results.

But no two lasers are the same. The difference between these two technologies lies in the length of the laser beam. For fiber lasers, the typical wavelength is 1064 nanometres, while for carbon dioxide lasers it is 10.6 micrometers.

This difference in wavelength is substantial because it influences the type of material that can be processed.

Fiber laser, the king on metallic materials

Fiber laser is mainly used in metal applications. Fiber technology enables higher energy densities to be achieved on the surface of metals for two reasons. The first is that metals absorb the wavelength of the fiber laser well, whereas they tend to reflect and scatter the wavelength of the carbon dioxide laser. The second, is that fiber laser allows a smaller focal diameter on the working surface than the carbon dioxide laser. As a result, the fiber laser achieves a higher energy density for the same power than the CO2 laser.

The main shortcoming of fiber laser technology is its lack of flexibility. The wavelength of the fiber laser is absorbed well by metals, but not only. A limitation of the fiber laser is that many materials absorb its wavelength. This makes it difficult to select which materials the laser should affect, especially on multilayered materials.

CO2 laser, the most versatile laser

Selectivity is one of the advantages of the CO2 laser. The 10.6 micrometer wavelength is absorbed well by all carbon-based materials. These include most of the materials used in manufacturing processes.

Below are some of the materials on which the carbon dioxide laser is most efficient:

• Plastics and polymers in general
• Wood and wood-based materials
• Paper and cardboard
• Biological materials

These materials absorb the wavelength of the CO2 laser very well, which makes these laser sources very efficient in their processing.

CO2 laser vs. fiber laser for laser engraving

Laser marking and laser engraving are two variants of the same process. In both applications, laser technology is used to remove a layer of material. In laser marking, the laser removes a very thin layer of material. The mark produced is therefore superficial. In engraving, the laser goes deeper, removing a greater layer of material. The mark is therefore deeper and can often be felt by touch.

Both carbon dioxide and fiber lasers can perform marking and engraving. Based on what we have previously said, it should be obvious that the main difference lies in the materials on which the processing is applied.

As far as fiber technology is concerned, marking and engraving is mainly used for product traceability, i.e. to indelibly engrave identification numbers, serial codes or data matrices on metal parts. The high energy density and small focal point make it ideal for this type of application on metal materials.

Marking and engraving, on the other hand, is one of the most widely used processes of the CO2 laser. This process has a wide variety of applications. In addition to the simple marking of identification codes, CO2 laser achieves more sophisticated decorative patterns, so much so that it is used in the fashion industry. One of the applications that has been developed in recent years is, for example, laser marking of denim fabric for the production of jeans.

Contact us

El.En. Laser is a company that specializes in the production of CO2 lasers. Since 1981, we have contributed to the development of this technology, which has become a great asset to the industrial sector. We produce CO2 laser sources, laser scanning heads and laser systems for Industry 4.0. Contact us for more information or to get a consultation on how to build the right laser system for your business.

Laser marking is one of the most widely used laser processes in the industrial sector. It is typically used to apply information to packaging: expiry dates, traceability codes, production batches, logos and other graphics. The fundamental advantages of laser marking over traditional methods are the very high processing speeds and the high levels of precision that can be achieved.

But the advantages don’t stop there. Laser technology not only allows manufacturers to increase processing efficiency parameters, but also to perform types of processing that would be impossible to do with traditional methods.

How does laser marking work?

Laser marking is a processing technique in which a laser is used to produce an engraving on the surface of a product. As with all laser-based processes, this technique exploits the laser’s ability to concentrate large amounts of energy on one spot with a diameter of a tenth of a millimetre. At the site where the laser touches the material, very high energy densities are reached, which cause the temperature to rise within a few seconds, triggering physical and chemical transformations.

A key feature of laser processing is the high degree of control. It is possible to decide with great precision how deep the laser’s action should go. With laser marking, the mark is only produced superficially, on a layer that goes from a few microns to one or two millimetres. Past this depth, one no longer speaks of laser marking but of laser engraving. The two processes, although similar, differ in the depth of the laser marking which in turn changes its perception. Laser engraving creates marks that are more visible and perceptible to the touch. In laser engraving, the mark is visible but not very perceptible to the touch.

Laser marking and packaging

In all laser processing, the type of power used depends on two factors: the material one wants to process and the speed one wants to reach. As you may already know, every laser emits a beam of polarised light at a defined wavelength. Some materials absorb certain wavelengths well but not others. In the packaging sector, the CO2 laser is the one that gives the best results. Its 10.6 micrometer wavelength belongs to the far infrared region which is very well absorbed by the organic materials most frequently used for packaging (e.i: paper, cardboard, thermoplastic polymers, glass).

Advantages of laser marking

Traditionally, the following methods are used to mark information on packaging:

1. inkjet printing
2. thermal transfer printing
3. stamping
4. hot stamping
5. mechanical engraving

These techniques are always based on contact between the tool and the workpiece. Compared to them, the laser has several advantages:

1. reduced cost: the information is engraved directly on the product, which eliminates the need for any other material, such as ink and labels
2. indelibility: it is resistant to wear, solvents, scratches, light and counterfeiting attempts.
3. automation: the process is fully automatable.
4. flexibility: laser marking can imprint any type of information, however complex.
5. contact-free: materials are not subjected to mechanical stress.

Materials and laser marking

As mentioned above, the characteristics of the material used influence the specific characteristics of the marking operation.

Paper and cardboard packaging

Paper and cardboard are made from cellulose, a material of organic origin produced through wood processing. The laser acts on the paper by vaporising a thin layer of material. The resulting mark has the same light colour as the material and may therefore offer little contrast. The contrast can be increased by adding a dark-coloured overlay. In this case the laser only removes the coloured surface layer to reveal the light part underneath. The contrast between the white of the paper and the darker colour of the surrounding layer creates a very legible mark.

Laser marking on plastics

Plastic is a synthetic organic product based on carbon-based polymers. On certain types of plastic, the CO2 laser is very efficient and gives optimum results. The plastics that are best suited for laser marking are those most commonly used in the packaging industry, such as polyethylene, PET or polypropylene. Polypropylene is also suitable for laser cutting.

Laser marking on plastics is carried out by chemical transformation (the laser breaks polymer chains). The fact that the light affects the mark differently to the surrounding material makes it quite visible. Depending on the additives applied to the plastic, different levels of contrast can be achieved.

Laser marking on glass

Laser marking can also work with glass. Marking on glass is carried out through the physical transformation of the material. Glass is a very fragile and inflexible material that traps micro-bubbles of air inside itself. When the laser strikes the surface of the material, the air bubbles expand due to the heat, creating micro-fractures. This changes the transparency of the material and creates the mark.

Beyond packaging

In some cases, laser marking can eliminate packaging. In recent years, laser marking on food has become a well-established technique. It is mainly used on produce or cured meat and cheese but can be used on any compatible product. In this application, the marking is done directly on the surface of the product. A layer, a few microns deep, is removed from the surface. The laser beam does not penetrate into the product so its freshness is preserved. Several studies have shown that laser marking does not affect the quality of the product in any way. Food distributors rely on it to save on tons of packaging materials each year, including self-adhesive labels.

Equipment for laser marking in packaging

The technical requirements for a laser marking system are a CO2 laser source, which produces the beam, a scanning head, which moves the beam over a surface, and a software controller, which coordinates the system.

The laser source

In the El.En. catalogue we have laser sources that range from 60W to 1200W of power. Greater power corresponds to greater energy per unit area, which can be translated into greater execution speed. Our catalogue has a selection of laser sources optimised for certain packaging materials. BLADE RF177G and BLADE RF333P with their two different wavelengths of 9.3 um and 10.2 um are perfect for the materials used in the packaging industry and in kiss cutting for adhesive labels.

Our Never Ending Power sources use Self-Refilling technology that potentially makes the laser’s life endless. This involves the addition of a consumable, the gas cartridge, which contains the propagation medium and can be easily replaced when it runs out. In this way, sources can maintain their performance over time. Unlike sealed lasers, this eliminates the time-consuming and costly refurbishment process.

The scanning head

Applications such as marking are called galvo laser scanning because they use galvanometric mirrors to move the laser beam across the surface.

The main feature of our scanning heads is that they have a z-dynamic motor, which allows the focus to be adjusted in height and thus maintain constant parameters on the work area.

The digital controller

The CO2 laser source and the scanning head need software to coordinate their movements in order to perform the required machining. Our heads also include this control system, which can be easily integrated with common operating systems.

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In recent decades, lasers have become a widely used processing tool. Its role as a production tool is increasingly established, both in traditional applications such as laser cutting, laser welding or laser marking, and in more advanced ones such as laser paint removal, laser surface treatment or laser microperforation.

The success of this tool is due to the advantages it offers in terms of process flexibility. The same laser source can be used to perform different processes such as cutting and marking on different materials such as plastic and wood, even within the same operating cycle.

This great flexibility translates into process complexity. In general the working mechanism of the laser is very simple. A laser is a light source capable of concentrating a very high energy density, so much so that it can be used as a heat source. In practice yet, the interaction between the laser and the material is influenced by numerous factors that make it very complex.

Conceptually, cutting, drilling, engraving and marking share the same processing mechanism: laser energy is used to create chemical and physical transformations in the material. These transformations can range from the simple colouring of the material, as is the case with laser marking, to the complete removal of the material by sublimation as is the case with laser cutting. In order to switch from one process to another, it is sufficient to modify the laser parameters using the appropriate control software.

For this reason, each application must be studied according to the characteristics, of the laser, of the process and of the material.

In this article we will analyse the main parameters that come into play in laser processing, with particular reference to the CO2 laser.

Laser-related parameters

Unlike traditional production tools, laser technology has a wide range of configuration options. Each parameter affects the end result of the process and must therefore be configured appropriately according to the desired result on the material.

The laser parameters to pay attention to are:

• laser source power
• beam spatial mode
• beam temporal mode
• laser wavelength
• beam polarisation

Laser source power

The power of the laser source is a very important parameter. It regulates the laser’s processing speed and the depth of the engraving. The more powerful the laser, the greater the amount of processed material in the same amount of time. Furthermore, the more powerful the laser, the thicker the material that the laser will cut can be,although, as we will see further on, this parameter depends in part on the characteristics of the material.

If you are using a low-power laser, it may not be possible to cut a material from side to side. On the other hand, a laser with a higher power than the one needed to carry out a specific process, can cut through the material, with the risk of obtaining a lower quality cut, with burnt and uneven edges due to the slag produced by the excessive power of the laser.

As a general rule, the choice of the power of a laser source should be made in excess so that the power can be lowered until the desired result is obtained.

Spatial mode of the laser beam

This parameter defines the cross-sectional profile of the laser beam. A laser beam can have several modes, i.e. it can have different profiles.

The most commonly used mode in laser cutting applications is the Gaussian mode, as it allows maximum energy density to be produced, i.e. the beam is concentrated in a very small diameter point.

In this way, it is possible to obtain cuts and engravings with very reduced dimensions, with high processing speeds and the possibility of cutting larger thicknesses.

Other spatial modes, on the other hand, allow the beam to be focused on a larger surface area, thereby achieving lower energy densities.

Time mode of the laser beam

Lasers can be used in two modes, continuous wave or pulsed mode. The continuous wave mode is the most widely used (mainly in mass production), and allows very smooth cuts and thicker materials to be cut. The pulsed mode is used for more precise work, often with a low-power laser.

Wavelength

The way different materials absorb laser radiation depends on their wavelength. While some materials absorb the wavelength of the CO2 laser very well, others require different wavelengths and therefore other types of laser.

Aluminium and copper, for example, absorb the wavelength of the CO2 laser very little and require very high powers to be cut, which reduces production efficiency. Non-metallic materials such as wood and synthetic materials such as polymer plastics, on the other hand, absorb the CO2 laser radiation perfectly. Metals such as mild steel and stainless steel can also be cut with the CO2 laser with excellent results.

Polarisation

Polarisation refers to the ability of the laser beam to radiate in only one direction. This property differentiates the laser from non-polarised light sources, which radiate in all directions.

This parameter is important insofar as it affects certain characteristics of the cut. Generally speaking, when the cutting direction and polarisation have the same orientation, very thin, sharp-edged and vertical cuts are obtained. When the direction of the cut is the opposite of the one of the polarisation, the energy absorption of the material is reduced, resulting in a reduction in the speed of machining and a wider cut with rough, irregular edges.

Material characteristics

When configuring a laser system, the characteristics of the material must be taken into account. Not all materials are laserable. Some do not absorb certain wavelengths; others produce unsatisfactory results when subjected to the laser beam.

Thermal properties and reflectivity are the parameters of a material that need to be taken into account.

Thermal properties

From the point of view of laser processability, materials can be divided into two categories, metals and non-metals. The two groups respond differently to laser radiation and therefore offer different degrees of processability.

Metals have high thermal conductivity, a higher melting point and high optical reflectivity. For this reason, laser processing is very inefficient in most cases.

Non-metals, on the other hand, absorb laser radiation very well, particularly that of the CO2 laser, and can therefore be processed very efficiently. All it takes is a small concentration of laser energy to initiate the material transformations that carry out the processing.

Reflectivity

This property is especially relevant for metals. While we can generally say that all metals have a high degree of reflectivity, it is not a fixed parameter. The reflectivity of a metal can vary as the physical properties of the metal change. For example, reflectivity decreases when a metal is heated or when shorter wavelengths are used.

The reflectivity of a metal can be limited by the use of a non-reflective film applied to the surface of the material.

The polarisation of the beam also affects the reflectivity of a material.

Process characteristics

The laser machining process can be carried out in many different ways and use different technologies.

The following features of the machining process influence the final result:

• beam travel speed
• assist gas
• nozzle shape
• stand-off distance
• focal plane position and focal length

Beam travel speed

The travel speed of the beam is crucial in determining the final processing result. The thicker the material, the slower the laser has to travel because if it is too fast, it cannot penetrate the material.

In some cases this principle can be used for a purpose, such as laser marking and engraving.

On the other hand, if the laser proceeds too slowly, the material gets too hot, increasing the heat in the affected zone, which can lead to charring and damage to the material.

The right speed is the one that achieves the best quality for the desired result, as efficiently as possible.

Gas assist

In some cutting processes, the laser emission may be accompanied by a gas jet. This technique makes it possible to improve the efficiency, speed or quality of machining.

Some of the most commonly used gases are oxygen, used to cut mild steel, nitrogen, to cut nickel alloys. Helium, argon and other inert gases and simple compressed air are also used.

The gas jet can be either coaxial to the laser beam or directed. The final decision depends on the characteristics of the desired processing.

Nozzle shape

The nozzle is the device through which the laser beam is irradiated onto the processed surface. Its configuration has an influence in determining cutting characteristics such as shape, size and edges.

Stand-off distance

This parameter is determined by the distance between the nozzle and the processed surface. The spray distance affects the gas flow. Too great a distance can cause turbulence, which creates irregularities in the cut. If, on the other hand, the nozzle is too close to the work surface, splashes of molten material can damage the laser’s focusing lens.

Focal plane e position and focal length

The laser needs to be focused on the working surface at all times. The focus point must therefore always be on the processed surface, in order to achieve maximum energy density and precision. Controlling this parameter is essential to obtain good quality and uniform processing along the entire path of the laser.

Every laser configuration is specific

In summary, it is clear that it is not possible to standardise laser applications. The processed materials, the characteristics of the process and the technical characteristics of the laser system determine the type of configuration one should use. Contact us: our experts can define a process that suits your needs!