Creating Quality for Leather Interiors

Although more and more OEMs have leather trim packages for vehicles at all levels, you might be surprised to learn about how some of that material is processed.

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Roy Shurling spends a lot of time traveling. He’s visiting OEMs. Tier ones. And tanners. As in leather tanners, not people on the Cote d’Azur. Shurling is the global automotive business development leader for Lectra (lectra.com), a company that specializes in software, CAD/CAM equipment and services for industries that use materials including fabrics, textiles and leather (so in addition to automotive, for example, the company also deals with fashion and apparel).

Shurling says that he’s presently involved in helping transform the supply chain for leather—from the tanner of hides to the tier one suppliers that are producing the seats or other pieces of interior trim to the OEM—to a digital one.

Part of this drive is predicated on the fact that in Germany, he notes, Industry 4.0 is a big movement toward digitizing manufacturing across the board. (When you think of OEMs that use an extensive amount of leather in their interiors, you undoubtedly think of German vehicle manufacturers.) And another is from a quality perspective: things like seats can be designed better and the hides can be cut more precisely.

Shurling says that while computer-aided design tools are a matter of course for things like exterior vehicle designs, this is not the norm in leather seat design. He explains that for seats it is often a matter of a designer creating a prototype artifact—a clay or foam model—and then literally draping fabric over the model on the way to developing the seat. “It is a very tedious process and they have to go back and forth to find the right fit,” he says.

Their alternative is a 3D design system that can conduct feasibility studies (taking into account the leather properties) to get a first cover much faster and more accurately.

“The software can show where to change the location of the seams to get better quality, and it can show you how to change the patterns to save cost—through nesting it is common to find a 10 to 15 percent improvement on cost,” Shurling points out.

The number of companies that do this? A couple of OEMs, he answers. “There’s a lot of opportunity to improve quality in the early part of the design cycle,” he says.

(On the subject of time, Shurling adds that if the task is to develop an entire interior—wrapping everything from the seats to the steering wheel to the IP to the door trim—in leather, the software can save from four to six weeks in development time.)

Shurling suggests that some pushback to using the software is from those who think that the craftsman is being taken out of the process. He counters that the design software is just a tool: “When it is doing the feasibility it shows the strain and the stress and where the wrinkles are going to be. But it doesn’t fix it. It will tell you where they will be. Somebody has to say they can move a seam or cut a pattern differently to get the stress out.”

One of the particular quality challenges of designing and using leather for interior applications is that unlike steel or plastic, it is a natural material. “Even though it has been tanned and finished and they try to take out a lot of the quality issues, you can’t avoid some things like brands and bites and veins and things that appear in the leather. That has to be taken into account during all stages,” Shurling comments.

“The quality output is really based on the skill set of the people who mark the hides and look for the defects,” he adds.

But then there is the next step in the process, which is cutting the hides into the various shapes needed for creating the interior components. Shurling says that most—as in some 90 percent—of all hide cutting is done with steel rule dies. Operators must position the dies carefully so that defect zones are avoided during the cutting process.

However, he points out that sometimes the workers are paid on an incentive system that is based on the number of hides processed or pieces produced, which means that some of the workers might be inclined to not be quite as diligent as they otherwise might be. “A big tanner is cutting somewhere between 3,000 and 8,000 hides per day, so there are hundreds of people, with all different skills, placing dies every day. Maintaining quality is very hard,” he says.

The Lectra alternative is based on a system that optically scans the surface of the hide, picking up the chalk mark that indicates a defect. Then it calculates the best nesting and it also determines quality zones (e.g., usable, unusable, and different grades). For example, an area of a knee bolster or glove box that isn’t readily visible can be cut out of a piece of material that isn’t the top grade.

The actual cutting is performed with a “very small knife” that operates at 20,000 strokes per minute. Shurling says that the kerf with the knife is almost zero, whereas the steel rule dies can create a 2- to 3-mm gap. So the automated system can cut closer to defects, resulting in less overall waste.

“Ninety percent of leather is still cut with dies,” he says.

Clearly, a lot of upside opportunity for both cost and quality.