Lasers are enablers for more sustainability

By: Dr. Sven Breitung

Climate protection is an important topic for the modern industry and sustainability has always been an integral constituent of the laser industry’s DNA. The machines are designed for durability and backward compatibility over many years, and providing replacement parts over this period is a matter of course. In many industrial applications laser systems have afforded key contributions towards greater climate protection.

Lasers in the automotive industry

The central role of lasers is demonstrated by the following examples from the automotive industry:

• In bodywork, short pulse lasers are replacing chemical applications harmful to the environment.

• Laser diodes used to dry materials for electric vehicle batteries achieve substantial cost and energy savings compared with conventional industrial kilns.

• Laser processes can significantly reduce the abrasion of brake discs and thus fine dust emissions.

  
  

Car and battery makers are facing great challenges. Production has not only to be green, it must also involve less costs – and satisfy the equivalent rise in quality requirements. The laser enables the automotive industry to overcome these challenges.

Today’s cleaning processes in the automotive industry typically employ chemicals. Often, this is unnecessary. For instance, carmakers often need to clean only certain areas on a component that are to take the cold adhesive.

Short pulse lasers make exactly that possible. As a result, the automotive industry saves the water and chemical detergents otherwise needed for conventional cleaning methods. Also, carmakers must prepare the surfaces for permanent bonding, e.g. by incorporating special microstructures.

The short pulse laser offers a clean alternative to chemical etching. One expects in the next few years a strong growth in incoming orders for the laser treatment of surfaces.

The laser has already proved its usefulness in many applications in electromobility. A further, highly promising application involves the drying of battery films for electric vehicles. Here, laser diodes can apply heat directly and uniformly over the whole length of the battery film. At the same time, laser diodes consume far less energy and take up considerably less space on the production line than standard kilns. The demand for laser systems therefore finds an additional boost from electromobility.

In 2025, Euro 7 will come into force, heralding trenchant changes in the automotive industry: For the first time, there will be regulation affecting not only the emissions from IC engines, but also, for instance, brake particulates – and the fine dust emissions must be reduced drastically on many models. In response, OEMs and parts suppliers are seeking a new solution for the braking system, with current approaches favouring coated brake discs as the ideal answer.

To apply different coating systems in a process-safe and efficient manner within the scope of large-capacity production, laser metal deposition is ideal for brake disc coatings.

The threshold for all new vehicles from 2025 is only 7 milligrams of fine dust per kilometre, yet today a passenger car emits between 5 and 40 milligrams, depending on the model. This is a major challenge for manufacturers, especially since the brake is a critical safety component whose design is very complex in detail. Against this background, coated brake discs offer a solution: the conventional brake disc simply gets a new coating that offers protection against corrosion, wear and fine dust.

The laser metal deposition on brake discs is ideally suited for this and is a production solution that is cost-effective, suitable for large-scale production, reliable and flexible, for it can be applied to a great many combinations of coating and coated materials.

Supplied through a duct in the laser tool, the coating powder fuses with the surface of the disc at the welding temperature. Here the so-called surface rate is as high as 5 m2 per hour, and this with minimum coating thicknesses of 0.01 millimetres and less.

Diode laser and its applications

Compared with all other laser beam sources, the diode laser is the most efficient at converting electricity into laser light. The diode laser transforms electric current directly into photons, i.e. light. In contrast, all other beam sources require an additional active medium, for instance a disc or a fibre for the disc or fibre laser respectively. This additional medium impacts the electrical efficiency, which may drop as much as 30% below that of the diode laser. Today’s diode lasers, specifically direct diode laser beam sources, have an electrical efficiency as high as 55%, and therefore stand alone in the conversion of electricity into light.

Yet the quality of their beam does not make diode lasers suitable for all applications, but more about that later. Today’s direct diode lasers incorporate semiconductors that exhibit in many applications a very high MTTF (mean time to failure) of several hundred thousand hours. Diode lasers are therefore often used e.g. in the automotive industry, with service lives as high as 14 years in three-shift mode extending over two model series.

As I mentioned earlier, the diode laser is not suitable for all applications, but the applications it is very good for can benefit greatly from its sustainability.

When coating, the diode laser acts as an excellent, focusable heat source that melts the surface of the substrate and the coating material, supplied in the form of a powder or wire, in the one operation. These coatings can protect the exposed surfaces of components against abrasion and corrosion and extend greatly their service lives. One example from the field of coating is provided by the repair of components like rollers, gear wheels, tools, etc. This serves to extend service lives and save costs; cracks and damaged protective layers can be resealed or repaired; fractured parts can be reassembled; and ultimately the metal component reinstated in its full functionality.

Repair coatings applied by means of diode lasers require only moderate heat inputs, exhibit pore-free surfaces, and facilitate easy and quick repairs even on filigree components. The blue laser is ideal for welding and additive manufacturing with copper and its alloys. A great challenge to the use of infrared (IR) lasers is posed by the low energy absorption of highly reflective metals like copper and gold when exposed to wavelength ranges of 1 µm. The required high initial intensities induce processes that are often marked by turbulent melt pools and spattering: critical factors in the processing of electrical componentry. Attempts have been made to compensate for these problems encountered with IR lasers, resulting in complex beam modulations, many of them based on scanners. Copper alloys absorb blue light ten times better, so the blue diode laser returns excellent results, easily and reliably, with far less consumption of energy than alternative methods yielding the same result.

In additive manufacturing, blue diodes can deliver more than five times the deposition rate of IR with the same laser power, at the same time achieving a powder efficiency greater than 80% – an excellent performance on copper-based components. This example illustrates how the right choice of beam source can promote the efficiency of production, reduce the consumption of energy, and minimise the draw on resources for a significant contribution towards their protection.

Hardening with diode lasers

Most hardening processes applied to steel components are one of two kinds: induction hardening and laser hardening. Technologies based on diode lasers present a convincing array of results and energy consumption. Induction hardening often heats areas of a component’s surface that do not need to be heated at all. In addition, the heated components must be subjected to cooling showers or baths, which also requires energy. And often there is a need for further mechanical work to reinstate the original geometry. Combined with precision-focusable optics, the laser beam lends itself to the selective application of heat treatment only to those areas of a component’s surface relevant to hardening. And the self-quenching properties can help to cut additional energy costs needed for cooling measures. And thanks to the highly local and low heat input, a mechanical post-treatment very often becomes unnecessary. In some cases the laser method could save 90% of the energy that would otherwise have been needed for induction.

The laser can be used in a variety of ways, not only in the processing of metal, but also in the production of packaging. A lot of boxes are made from a material called corrugated cardboard. That’s a good material for several reasons. First of all, it’s recyclable. It’s also renewable. It’s made from wood pulp which can be grown and harvested sustainably – and not derived from petrochemicals. Corrugated cardboard is also biodegradable. Plus, it’s lightweight – which minimizes the fuel needed to transport it.

To make these boxes, they start with big, flat sheets of corrugated cardboard. The sheets are cut up and then folded to make the finished box. The cutting is usually done with a mechanical die – basically a piece of wood with several pieces of sharp metal embedded in it that cut the desired pattern. Die cutting works great but is only cost-effective when you’re making a fairly large number of identical boxes. And this means that the green advantages of corrugated cardboard boxes aren’t always accessible to companies who only need smaller quantities. Or even to bigger companies who sometimes want to produce a few speciality items from corrugated cardboard – like point-of-purchase displays. Of course, someone who needs a small quantity of shipping boxes can just buy a standard size box off-the-shelf. But unless they get lucky and that standard box is exactly the right size for them, there is some waste involved. Because if the box is too large, they’re going to have to fill the empty space with bubble wrap or something else. That’s wasteful. And, using a larger box than necessary means that fewer boxes can fit in a given volume. That ends up wasting fuel because it takes more vehicles to deliver a given number of products.

Lasers can change this whole equation. Specifically, laser-based digital cutting machines can replace die cutting and make short run production of custom sized boxes, product packaging, or other speciality items economical and practical. Just like in a lot of other laser-based materials processing applications, the cutting pattern is supplied to these machines digitally, enabling it to cut any pattern needed without physical tooling or much setup time. The corrugated cardboard material is usually around 3 mm thick. And it must be cut quickly. The CO2 laser is really the only source that can meet the requirements of digital converting for corrugated cardboard. This is because it produces mid-infrared light, which is absorbed much better by the cardboard than shorter wavelengths. This makes it cut very efficiently and enables it to cut thicker pieces.The laser power largely determines the maximum throughput of a digital converting tool. Also, this kind of digital converting also requires relatively high power – like in the kilowatt or multi-kilowatt range. High power CO2 slab lasers with excellent beam quality and pointing stability enable converters to produce packaging optimized to their customers’ requirements. They can also easily customize or individualize products by adding features like logos or specialised cut-outs. In fact, laser cutting offers greater capabilities for producing detailed features as compared to mechanical die cutting. This makes the packaging more attractive to their customers, since now they can use it for branding purposes.

Further applications

Laser glass cutting has replaced mechanical methods in many industries. It often produces a smooth finished surface that doesn’t require any further processing. This eliminates mechanical grinding or other post-processing steps that use energy and create debris which has to be disposed of.

Laser marking has replaced ink printing or chemical etching in many applications. Here, lasers reduce the use of consumables and eliminate the need for disposal of chemicals.

Lasers are sometimes used to strip paint or other coatings from surfaces. This can replace the use of hazardous chemical solvents.

The application examples show how lasers are already today making a key contribution to climate protection. On the one hand, the laser is a tool with the highest efficiency, and, at the same time, laser technology opens up many different applications to produce sustainably. Therefore, we invite you to learn more about this at EMO Hannover. More than 90 laser manufacturers will show their products and solutions there.