Applications for CO2 lasers in the automotive industry

An overview of how CO2 laser technology assists automotive producers in product development and manufacture.

INTRODUCTION

Since the inception of the moving production line by Henry Ford in 1913, automotive manufacturers have continuously pursued process optimisation to reduce costs and enhance profits by minimising assembly times. In contemporary automotive production, automation is pervasive, and robots have become integral to manufacturing processes. To further improve efficiency and versatility, lasers have emerged as indispensable tools, supplanting conventional methods and offering numerous advantages in the automotive manufacturing landscape.

MATERIALS DIVERSITY

Automotive manufacturing utilises a huge range of different materials, including plastics, metals, textiles, glass and rubber.  High-end and luxury vehicles may feature state-of-the-art carbon fibre alongside traditional materials such as wood and leather.  Processing such a diverse range of materials requires a versatile tool, and this is where the CO2 laser comes in.  Invented in 1964, the CO2 laser is one of the oldest laser technologies, yet it remains a mainstay of modern manufacturing and finds a plethora of uses in the automotive industry today.  CO2 lasers are available with output powers ranging from a few tens of watts to several kilowatts, making them useful for a variety of different processes; low power levels are used primarily to mark and engrave, while higher powers can cut and weld with ease and precision.  As a result, laser-processed components find their way into almost all areas of a typical vehicle, both interior and exterior. 

PROCESSING PLASTICS

CO2 lasers find extensive use in processing plastic components, including interior panels, dashboard components, pillars, bumpers, spoilers, trims, number plates, and light housings. A broad spectrum of plastics is encountered, such as ABS, TPO, polypropylene, polycarbonate, HDPE, acrylic, and various composites and laminates. Plastics may be bare or painted, and may be combined with other materials, for example fabric-covered interior pillars, composite or veneered trim panels, and support structures filled with carbon or glass fibres 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 moulding process.  Headlamp housings and lenses made from clear plastic often require laser trimming to remove tabs of waste plastic left after moulding. 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 which require no post-process cleaning or further modification. 

Plastic cutting operations are typically 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.  Of course, the handling requirements may be complex, and cutting operations frequently require either the laser beam or the part to move in three dimensions; this is where robotic technology comes into its own.  

ROBOTIC INTEGRATION

In the era of highly automated automotive production, robots are indispensable. The integration of lasers into robotic systems presents unique challenges and can be approached in three ways:

1.           Mounting the laser directly on the robot arm with an articulated beam delivery system, enabling the robot to execute intricate cutting tasks while maintaining precise beam focus.

2.           Moving the workpiece in front of a stationary laser beam, a simpler approach suitable for smaller robots but the maximum size of the components is limited.

3.           Mounting an articulated arm on the laser, allowing the robot to position the arm for cutting tasks.

The first of these requires the laser to withstand the G-forces produced by the motion of the robot.  The robot must be large and powerful enough to support and move the laser; alternatively, the laser must be sufficiently compact and lightweight to allow mounting directly on the robot arm.  The second method often employs a galvanometer scanner to steer the laser beam as the part is offered up by the robot.  Holes and small features are cut at high speed, often completing several cuts at each robot position.   A typical application involves drilling small holes, typically around 1mm in size, across the surface of an instrument panel; this allows a vacuum on the back side to remove any air voids as the cover stock is adhered to the outer surface.  Larger holes and features may be cut in a similar way, for the installation of switches and sensors, for example. 

CUTTING TEXTILES

Laser technology also extends to cutting and patterning textiles used in car interiors, including fabric upholstery and leather.  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 plastic parts during the moulding 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. CO2 lasers with moderate power, such as Luxinar’s SR and OEM series, are typically used for these applications.  

SAFETY SYSTEMS

Fabrics are not only for decoration and comfort; technical textiles are utilised in a vehicle’s safety systems, namely seat belts and airbags.  Modern vehicles are typically fitted with multiple airbags as standard, to protect both driver and passengers.  Airbag materials are usually made from densely woven nylon or polyester fibres, and are often silicone-coated to obtain the desired air permeability.  Airbags may be flat-woven, where the bag is made up of several fabric pieces stitched together, or one-piece-woven (OPW), where the structure of the airbag is fully formed on the loom.  Both types require trimming, for which a CO2 laser is the ideal tool.  The laser process is efficient and reliable, minimising waste by cutting with consistently high quality.  The non-contact nature of the process means that handling of the fabric is minimised and the silicone coating is therefore less likely to incur any damage which may compromise the integrity of the airbag. 

It is testament to the versatility of the CO2 laser that the same technology can be used to score lines in the material of the car dashboard and door skins, selectively weakening the structure so that a flap breaks open to release the airbag in the event of a collision.  This laser scoring is implemented on the reverse side of the interior panels, so there is no aesthetic impact visible to the occupants of the vehicle and must be performed to extremely tight tolerances. 

SURFACE MODIFICATION

CO2 lasers are also employed in automotive manufacturing for surface modification and paint removal from selected areas of plastic or composite components. This ablation process is crucial when attaching components to painted or lacquered surfaces, where the laser precisely removes the top paint layer or roughens the surface for improved adhesion.

Here, the laser is used in conjunction with a galvanometer scanner to pass the laser beam in a raster or cross-hatched pattern over the required area at high speed.  The laser delivers just enough energy to ablate the surface without damaging the bulk of the material.  Precise geometries can be realised with ease, ablation depth and surface texture can be controlled, and ablation patterns can be changed as required with a minimum of effort.  In some cases laser technology may replace a process previously done by hand, resulting in considerable savings in time and improvements in quality and consistency.

CONCLUSION

Laser-based manufacturing extends beyond luxury cars; it is prevalent in everyday vehicles.  CO2 lasers impact various components: marking windows with security details, engraving tyres with product information, drilling rubber door seals and wiper blades for better water flow, cleaning brake discs, and selectively removing enamel from copper hairpins in hybrid or electric motors. CO2 lasers also cut or trim plastic parts such as number plates, instrument panels, door skins, lamp covers, interior pillars, filter housings and air intake ducts, among others.

CO2 laser technology has become indispensable in automotive manufacturing enhancing production processes and product quality, and today’s producers are constantly finding new ways to use this well-established and versatile technology to ensure their continued relevance in the ever-evolving automotive landscape.