Ever since Henry Ford introduced the first moving production line to the industry in 1913, automotive manufacturers have been constantly striving to streamline their processes, ultimately aiming to reduce costs and increase their profits by cutting assembly times. Modern automotive production is highly automated, and robots have been commonplace throughout the industry for many years. Lasers are now used in conjunction with this technology, replacing conventional tools and bringing a host of additional benefits to the manufacturing process.
Automotive manufacturing utilizes a diverse variety of materials, including plastics, textiles, glass and rubber, all of which can be successfully processed using lasers. In fact, laser-processed components and materials find their way into almost all areas of a typical vehicle, both interior and exterior. Lasers are employed at every stage of the car manufacturing process, from design and development through to final assembly. Not limited to mass production, lasers are even finding applications in high-end, bespoke car manufacturing, where throughput is relatively low and some processes are still done by hand. Here, the aim is not to scale up or speed up production, but rather to improve the quality, repeatability and reliability of processing, thus reducing rejection rates and wastage of costly materials.
One area where lasers are most widely used is the processing of plastic parts; these include interior and dashboard panels, pillars, bumpers, spoilers, trims, number plates and light housings. Automotive components can be made from a wide variety of plastics including ABS, TPO, polypropylene, polycarbonate, HDPE and acrylic, as well as various composites and laminates. Plastics may be bare or painted, and may be combined with other materials, for example fabric-covered interior pillars and support structures filled with carbon or glass fibers for reinforcement. Lasers can be used to cut or drill holes for fixing points, lights, switches, parking sensors and other components, as well as to degate or trim excess plastic left over from the injection molding process.
Headlamp housings and lenses made from clear plastic often require laser trimming to remove tabs of waste plastic left after molding. Lamp parts are usually made from polycarbonate, chosen for its optical clarity, high impact/shatter resistance, and its resistance to weather and UV rays. Although the laser process leaves this particular plastic with a rough finish, the laser-cut edges are not visible once the headlight is fully assembled. Many other plastics can be cut with a high-quality finish, leaving smooth edges that require no post-process cleaning or further modification.
For many of these applications, lasers work in conjunction with robot systems due to the 3-dimensional nature of the parts to be processed. In some cases, a robot will pick up a part and present it to a fixed processing head, manipulating it as required to complete the cut. Alternatively, the laser itself might be mounted on a robot arm in order to steer the beam around the 3-dimensional contours of the part.
Many processes are realized using a combination of these two methods, manipulating both the laser head and the workpiece in order to perform multiple cutting operations with maximum efficiency. In many cases several laser processes can be performed within a single robot cell, improving cycle times and production efficiency.
Laser operations can be performed on parts whose geometry would make some areas inaccessible with conventional tools. Waste is minimized, as is downtime – due to the non-contact nature of the process, there is no tool wear or breakage, and the laser requires minimal maintenance. Operator safety is ensured, because the whole process takes place inside a closed cell with no user intervention required; there are no moving blades, and therefore none of the associated hazards. Laser processing means that designs can be changed quickly and easily with no associated tooling costs, and consistent results can be produced throughout.
Plastic cutting operations can be performed with laser power anywhere from 125W upwards, depending on the time available to complete the task. The relationship between laser power and process speed is linear for most plastics, meaning that laser power must be doubled in order to achieve a twofold increase in cutting speed. Handling time must also be taken into account when assessing the total cycle time for a set of operations, so that the laser power can be chosen accordingly.
Laser processing of plastics is not restricted to cutting and trimming; in fact the same laser technology can be used for surface modification or paint removal from selected areas of plastic or composite. This is often necessary when a component is to be fixed with adhesive to a painted surface; the top layer of paint may need to be removed or the surface may need to be roughened in order to guarantee good adhesion. In this, case the laser is used in conjunction with a galvanometer scanner to pass the laser beam over the required area at high speed, delivering just enough energy to ablate the surface without damaging the bulk of the material. Precise geometries can be realized with ease, ablation depth and surface texture can be controlled, and ablation patterns can be changed as required with a minimum of effort.
Of course, cars are not composed entirely of plastic, and lasers can also be used to cut many of the other materials used in automotive manufacturing. A car interior typically includes several different textile materials, the most obvious of which is the cloth for the upholstery. Process speed depends on the type and thickness of the fabric, but a laser with more power will cut at proportionally higher speed. Most synthetic fabrics are cut cleanly, and the edges are sealed so that the material does not fray during the subsequent stitching and assembly of the car seats.
Leather, both real and synthetic, can be cut for car upholstery in the same way. The fabric coverings, which are often seen on the interior pillars of many consumer vehicles, are frequently finished using lasers. Fabric is bonded to these parts during the molding process, requiring the excess to be removed from the edges prior to fitting in the vehicle. Again, this is a 5-axis robotic process, with the cutting head following the contours of the part and trimming the fabric with precision. For this, lasers from both Luxinar’s SR and OEM series are typically used.
Fabrics are not only for decoration and comfort; technical textiles are utilized in a vehicle’s safety systems, namely seat belts and airbags. Flat-woven airbag materials are typically silicone-coated to obtain the desired air permeability and must be laser-cut to shape before stitching the parts together. One-piece-woven (OPW) airbags also require trimming, for which a laser is the ideal tool. In both cases the non-contact nature of the process means that handling of the fabric is minimized and the silicone coating is therefore less likely to incur any damage, which may compromise the integrity of the airbag.
As the automotive industry evolves, car manufacturers are constantly using lasers in new ways. The industry is currently undergoing a radical change towards electric and hybrid vehicles, with the introduction of the so-called “e-mobility” concept – namely the replacement of traditional internal combustion engines with electric drivetrain technology. This requires manufacturers to adopt a host of new components and manufacturing processes.
Electric motors utilize copper “hairpins” – thick, rectangular copper wires that generate a magnetic field within the motor’s stator. The hairpins are coated with a dielectric enamel that must be partially removed so that the hairpins can be welded. This process is carried out most effectively with a laser. A galvanometer scanner is used to pass the beam over the required area, turning the hairpin mid-process in order to ablate all sides, while leaving the copper undamaged. Although multiple passes are usually needed to ensure that the metal surface is completely clean and free from residue, the laser process is cleaner and faster than the equivalent mechanical operation.
Luxinar’s offering in the automotive industry is not restricted to industrial laser sources; the MULTISCAN CO2 laser marking system may also be used in various ways. In the rubber seal around car doors or tailgate, there are small drainage holes, each a few millimeters in diameter. These are drilled in the hollow rubber extrusion on the fly, using the MULTISCAN to track the moving product.
Rubber for windscreen wiper blades may be processed in a similar way. The MULTISCAN may also be used for marking various automotive parts with information for identification, traceability or security; these include plastic components, wiper blades, and car windows. Laser marking compares favorably with the alternatives; it eliminates the high consumable costs which are inherent in inkjet printing technology, and also produces a more permanent, indelible mark in most cases. Hot stamping offers permanence and mark quality, but this comes at the expense of flexibility, each mark requiring its own die. Laser marking, on the other hand, is fast, versatile and adaptable; information and graphics to be marked can be changed very easily, with no tooling changes and no downtime.
The advantages of laser processing are numerous. As well as delivering consistently good quality and reliability, laser processing is highly flexible, and adaptable to the huge diversity of components, materials and processes used within the automotive industry. Lasers can cut, drill, mark, weld, scribe and ablate; in other words, laser technology is endlessly versatile, making it an essential part of an industry which is constantly driving forward.