GF Machining Solutions
Although the interiors of premiumÂ German cars have long been benchmarks,Â conceivably the quality levelÂ within some of those vehicles is goingÂ to be getting even better soon. ThatâsÂ because, says Gisbert Ledvon, businessÂ development manager, GF AgieCharmillesÂ (GFAC; gfac.com/gfac.html , a producerÂ of laser ablation equipment (as wellÂ as a range of other products used toÂ manufacture high-quality molds andÂ dies, including electrical dischargeÂ machining (EDM) equipment andÂ precision milling machines), a fewÂ years ago suppliers for some of theÂ German builders bought laser ablationÂ equipment to produce tooling forÂ interior components, and given theÂ roughly three year lead-time, thoseÂ vehicles are about to hit the streets.Â
âLaser ablationâ is a process throughÂ which a metal is sublimated, or goesÂ from a solid to a gas without theÂ intermediate step of a liquid form (as inÂ melting). The laser ablation performedÂ by a GFAC machine is done with aÂ pulsed ytterbium laser with a power ofÂ 20 W or 50 W. The spot size ranges inÂ diameter from 30 to 70 microns.Â
The laser is guided by a program thatÂ is based on digital input, be it a CADÂ model of the texture to be achievedÂ or a 3D scan of a physical model ofÂ the desired surface. Thanks to the useÂ of the digital model, there is a highÂ degree of consistencyâa higher degree,Â Ledvon says, than can be achieved viaÂ the common method of using chemicalÂ etching for creating the surface texturingÂ on molds and dies used to produceÂ interior components ranging from trimÂ pieces to instrument panels. This isÂ particularly the case when there areÂ multiple molds involved in producing aÂ given component due to the variabilityÂ from the texture that can be producedÂ on each of the molds, as analog methodsÂ arenât as repeatable as digital. InÂ addition to which, there are differencesÂ predicated on the process parametersÂ of the chemical etching process (i.e.,Â unless each of the components is in theÂ chemical solution for precisely the sameÂ amount of time, there will be variationsÂ in the degree of etching).Â
Because the laser processing is highlyÂ deterministic (i.e., it is driven by theÂ digital model; the laser makes a seriesÂ of spots of the same size and depthÂ on the surface based on the program)Â variation is essentially nonexistent.Â
Consider, for example, instrumentÂ panels where there is a door cut outÂ for the passenger airbag. As thoseÂ are two different parts, it is often theÂ case that the texture on the tools isÂ slightly different between the largeÂ piece (the panel) and the smaller partÂ (the door). Ledvon points out that inÂ some cases, larger part textures areÂ produced through the use of chemical etching while the molds for some smaller parts are made with EDM, which results in a different texture. If vehicle manufacturers are looking for consistency across the 3D surfaces, then the pulsed laser processing is the way to achieve it because the same pattern can be produced on each of the tools.
Preparing a surface for chemical etching is labor intensive. This is because the foils and films used in the process must be precisely aligned and located. But the chemical etching process is much quicker at removing material than laser ablation. This is most notable in cases where the surface area to be addressed is large.
So some companies, Ledvon says, are using a combination etching-ablating process, one that minimizes the direct labor of the etching process and optimizes the amount of time required to perform the texturing. The surface of the mold is spray painted. Then the laser ablation system is used to remove the paint, exposing the steel as required for the texturing.
However, there are cases where there needs to be the utmost precision in details and featuresâagain, think of Â the interiors of high-end German carsâand Ledvon maintains that to achieve, say, a stitching pattern on a surface there is no alternative to the laser ablation technique.
Another advantage of the laser approach is that it permits far more layering of the texture on the surface than is possible otherwise, as many as 50 layers. This means that the surface produced is far richer in 3D appearance.
In addition to providing visual grains on instrument panels and center consoles, there is an additional interior use. Knobs and buttons can be produced with a distinctive texture. Plastic can feel like satin, Ledvon says.
GFAC offers five laser ablation machines, starting with the LASER 500, which offers three axes of laser processing (X, Y, Z axes= 500 x 405 x 82 mm) to the LASER 1200 5Ax (X, Y, Z axes= 1,200 x 900 x 1,200 mm), which also provides a rotary B-axis to move the part and a tilting A-axis for the laser head, thereby making it capable of performing 5-axis laser ablation. (Maximum part size for the LASER 1200 5Ax is 700 x 700 x 700 mm).
According to Ledvon, the people at vehicle manufacturers who have shown the greatest interest in the laser ablation process are not engineers but designers: âWhen they see what can be achieved . . .â
Need to Know
â¢ Laser ablation uses a pulsed laser to vaporize metal on the surfaces of tools and molds
â¢ Using a 3D scan or a CAD file, the surface finish generated is precise (the systems fromÂ GF AgieCharmilles (GFAC) have linear scales with a resolution of 0.5 Î¼m on all axes)
â¢ The fiber laser source has a life expectancy of >30,000 hours
â¢ Chemical etching fluids present environmental issues
â¢ In addition to automotive interiors, tire manufacturers are looking at laser ablationÂ to provide visual distinctiveness of their products. Headlight mold manufacturers areÂ using it for processing the lamp reflectors.
By using a laser processâlaserÂ ablationâto remove metal from theÂ surfaces of molds and dies, a moreÂ consistent pattern can be achievedÂ than is possible with chemical etching,Â which is valuable for producingÂ interior components such as instrumentÂ panels and other trim pieces.