Finishing tools designed for a long life of grinding and blending are a key to seamless fabrication and keeping automotive plants competitive.

Figure 1: Automotive manufacturers are using laser brazing and welding to decrease weight and create a seamless body, Source: Rex-CutFigure 1: Automotive manufacturers are using laser brazing and welding to decrease weight and create a seamless body, Source: Rex-Cut

To meet the latest safety and emission standards being enacted around the globe and increasing aesthetic expectations, automotive manufacturers are using laser brazing and welding to drastically decrease weight and create a seamless body in white.

Laser brazing joins different metals using a lower melting temperature filler metal that melts to form a bond using precise laser technology and generates a more aesthetic joint quickly. Volkswagen, an early adopter of this innovation, employs a diode laser along with a silicon copper filler metal on the zinc-coated steel roof of the Touran Van at 4.4 meters per minute. The near-perfect seams are brazed together leaving tiny heat-affected zones in less than a minute.

It is no surprise that the white-body market is growing and is projected by FMI to hold strong through at least 2028. To remain competitive, automotive manufacturers should retool and adjust processes to save costs and increase efficiency when creating unibody vehicles.

Removing braze from parent metals

Automotive engineers prefer high-strength steel and aluminum for creating lightweight, fuel-efficient vehicles, and laser brazing successfully joins these dissimilar metals on a unibody vehicle. Unlike laser welding, laser-brazed joints consist of three different metals (typically steel, aluminum and the brazing alloy) that have different densities and finishing needs.

For instance, General Motors uses laser brazing to expediently attach a lightweight aluminum frame to the steel body panels of the Cadillac CT6. Audi joins two outer skins by laser welding aluminum with a diode laser. The seam is small, yet aluminum bonding has more splatter than steel brazing and requires proper finesse to remove the excess without damaging the uniform visual quality.

Laser brazing and welding are high-speed robotic processes that leave a minuscule margin for error. The time savings will go to waste if finishing removes too much braze or weld bead and gouges the metal structure. To efficiently move a body in white to the paint floor, robots should be optimized with the right customized abrasives for laser seams.

Standard robotic deburring machines are outfitted with unitized wheels, but they are slow and inefficient for removing excess braze or weld.

Customizing cotton fiber wheels

Cotton fiber wheels are versatile, fast finishing solutions for white-body blending and finishing. For example, Type 1 laser braze finishing wheels are made in the U.S. and are constructed from cotton fiber, yielding a high-density surface that can blend and finish in one step.

This style of multilayered abrasive is non-loading and designed for use in both automated and off-hand use. Cotton creates a cushion that prevents wheel chatter and the wheels are engineered to have the optimal speed and accuracy needed for finishing tight seams for white-body applications.

Rather than changing abrasives again and again during the day, non-woven cotton fiber abrasive wheels have a long working life, allowing the line to keep moving without interruption. Type 1 laser braze finishing wheels are loaded with aluminum-oxide grain in a specialized bond, providing a strong yet soft product. Fresh abrasive grain is continuously revealed while the wheel works, grinding and blending the bead quickly while leaving a consistent high-quality paintable finish on both steel and aluminum.

Compared to standard unitized wheels, non-woven cotton fiber abrasive wheels will blend and finish in half the time with a 70% longer working life, saving the assembly plant from spending extra time changing tools mid-process.

Adjustments for corrosion resistant metals

Hot-dip galvanized sheets are increasingly common in constructing car bodies, and the relatively small heat impact area of laser brazing makes it the right process for the job. Hot-dip proves to be more corrosion resistant than its electro-galvanized predecessor, but it also comes with manufacturing challenges to create a smooth final surface.

When laser brazing hot-dip galvanized sheet metal, micro spattering can occur near the joint. The spatter is virtually unnoticeable until after the part is painted, and can require a step backward in production, thus costing a shop days’ worth of work. Shops with unlimited resources choose to invest in triple-spot module technology to reduce the spatter. Using premium abrasives engineered for automotive roof gutter width is another smart, cost-conscious solution to this problem.

Quickly finishing the splattered surface of a hot-dip galvanized sheet is possible with an abrasive wheel that is manufactured to a specific thickness and size. Contacting the abrasive manufacturer directly will open the door to creating the right abrasive for the job and is the fastest way to reduce costs without sacrificing quality.

Eliminating process to adapt to innovations

Laser brazing is here to stay. In addition to those models previously mentioned, the Audi Q3, 2018 Honda Accord, Lexus IS and the 2018 Nissan Altima are just a few of the many vehicles across the industry that have laser brazed components. The initial investment in a robotic laser system is large and necessary for automotive manufacturers to stay relevant. A laser system already reduces the part cost per vehicle by flange elimination, ditch joint elimination and tailgate component reduction.

With flange elimination, the door opening on a body-in-white no longer needs reinforcement. Instead, manufacturers can run a continuous seam where the door will be attached. Meanwhile, with ditch joint elimination, which entails laser joining the roof to the body sides, the ditch joint and filler trim are no longer necessary. Likewise,with tailgate component reduction, laser brazing creates a seamless tailgate and eliminates any deep draw parts.

Manufacturers should look at the subsequent operations to reduce costs, increase productivity and stay competitive. Assembly plants are able to move cars through the line at a faster speed thanks to the faster finishing rate of non-woven cotton fiber abrasive wheels. The consistency of the finish quality delivered by the wheels results in virtually no repair or touch up, which saves on labor costs and prevents employee burnout.

With the right tools in hand, plants can minimize cost and increase efficiency in robotic processes that are now commonplace in automotive manufacturing across the globe.

About Rex-Cut

Rex-Cut is the only company that can customize to automotive industry needs. Learn more about finishing laser brazing and how to outfit a plant with premium abrasives by visiting Rex-Cuts website.