Remote laser welding: a few things to know - Produce - effects on retooling

Automotive Design & Production, Oct, 2002 by Gary S. Vasilash

Laser welding for body and component applications in U.S. facilities are slowly growing. Some of the benefits of remote laser welding may cause an acceleration. Here are some things to know about it.

Is it possible for machinery to minimize the amount of tooling necessary in a body shop, particularly for component (e.g., door, rear-shelf) assembly? The answer to that question, according to Vancho Naumovski, manager, Laser Systems, Utica Enterprises (Shelby Township, MI), is yes. And the equipment in question, of course, is a laser. But not just what has now become the (more or less) run-of-the-mill laser. Naumovski is talking about [CO.sub.2] remote laser systems.

A word about remote laser welding. One of the fundamentals of laser processing is that it is a noncontact operation. But whereas in conventional laser processing the work head is close to the work, with remote laser processing, there is a standoff distance on the order of 16 in. Consequently, there is the ability to effectively move the beam around with mirrors far more expeditiously than, say, if the laser is mated with a robot. In the case of a setup that Utica has developed, in its lineup of Flexlaser systems, the same sort of small, fast motor used in computer printers is deployed to rapidly move the mirror around--after all, the mirror has low mass, so the moving mechanism can be far less than what's needed to move a robot arm.

The key benefit of this standoff distance and this ability to maneuver the beam results in a comparatively large work area--such as 24 x 48 x 16 in.

Which brings us back to the issue of tooling. The reason why less tooling is required for remote laser welding than other types of welding is because, instead of having to move an assembly-in-becoming from station to station--which means from fixture to fixture--in order to weld it, the larger work area facilitates applying more welds in a single station. And less tooling can mean less money (although one must certainly take into account the necessity of designing tooling that is suitable for laser welding, which is different than that which is used for traditional setups).

More Advantages. There is an additional benefit: reduced tooling requirements mean that the overall footprint of the work cell can be notably reduced compared with what would typically be the case (e.g., one system Utica developed is 30% the floor space that would otherwise be required). And Naumovski makes another point about the remote laser welding process: It's fast. He talks about five spots per second.

Of course, there is the array of other benefits that are characteristic of laser welding of any type, such as the need for just one-sided access to the part (essentially, if there's line of sight, it can be welded with the beam); faster changeover (going to another part, depending on the flexibility of the fixturing, could simply require a program change in the laser welder control); and an array of weld patterns (e.g., continuous lines, line segments, circles, ovals).

The remote laser welding system is capable of producing butt, fillet, and lap welds. The 3-kW diffusion-cooled slab laser used in the Utica system (a 5-kW system is being developed, which will provide the means to have an even-greater work area) can be used to weld materials including mild steel, high-strength steel, stainless steel, aluminum, and magnesium. The system is capable of welding materials that are galvannealed, electroplated or hot-dipped galvanized, and aluminized. Naumovski recommends, however, that the coating thickness be both consistent across the surface of the material, as well as controlled to 14 microns or less.

Less METAL. There can be design benefits realized from the process. For example, with traditional spot welding of two pieces, there is often the need for a flange measuring from 12 to 18 mm to accommodate the spot welding gun. With laser welding (remote or otherwise), there can either be a smaller flange (say, 7 mm) or, assuming there's good metal fit up, no flange at all (which can be an overall savings in terms of not only the price of the material saved, but also with regard to the weight of the part or vehicle). The heat-affected zone resulting from laser welding is typically limited. Because of the noncontact nature, there isn't the issue of deformation from the clamping action of a spot welding gun.

One issue related to the remote laser welder's speed is that it is so fast that there can be a concern with the noncycle time: that is, it can weld faster than parts can be loaded. Utica has designed a number of different types of systems, such as with two dial tables that allow parts to be loaded with parts while welding is proceeding.

Naumovski admits that the amount of remote laser welding is rather limited right now (e.g., there is a system that DaimlerChrysler is using for welding the rear-door assemblies for the Liberty), but there is growing interest. One recommendation that he makes for those who are looking into the possibility is that they be sure to include a wide array of people in the project--from designers through welding engineers to production people. This is not only because of the fact that the technology is comparatively new, but it is necessary to look at the program from various perspectives in order to take advantage of what the process can offer. For example, the full benefit of laser welding (remote or otherwise) is not going to be gained if it is simply a matter of laser welding a part that's been designed for spot welding (e.g., there is likely to be a flange that's bigger than necessary). And, although operational maintenance is comparatively low (e.g., cleaning the mirrors with acetone every six shifts or so), it is a different type of maintenance, so those people need to be brought into the loop.