3D LASERS AND THEIR GENERAL APPLICATION
By Frank Geyer
While high quality parts demand the precision and dynamics of 3D laser cutting, good workholding is absolutely critical to having a successful system. A poorly fixtured part will cause problems during the cutting process, regardless of the capabilities of the system. Because certain 3D laser cutting applications can be quite challenging, tight tolerances and quality control for the workpiece must be in place to produce repeatable high quality cuts at maximum processing speeds.
For example, one challenging scenario that 3D laser cutting faces is small diameter tubes, where the cut will always affect the opposite inner wall of the tube due to spatter and the heat affected zone. Depending on the part geometry and cutting process, those effects can be minimized or eliminated. One solution can be to put inserts in place to protect the inside or run media through the tube at high volume to minimize this effect. In this situation, the ability to isolate the cutting area is the key to making the process feasible.
When cutting tubular components, for example, the addition of a 6th axis to turn the parts synchronized to the other 5 axes helps reduce the overall cycle time while making areas accessible that otherwise the 5th axis could not reach due to the limited swivel of the cutting head. This is commonly done when cutting hydroformed frame parts.
Even as the systems and laser sources evolve at a rapid pace, they still have their limitations. A typical part geometry that is not suited for laser cutting is a rolled or drawn profile, possibly with double walled areas. The cutting process requires clear access for both laser and process gas to be applied to the workpiece. The gas is used to blow out the molten metal out of the joint and also evacuate oxygen from the cutting surface if required. Profiles with tight sections that the beam cannot enter at required process angles means cutting is no longer possible. If rolled profiles have two walls close to each other, the cut of the inner wall is not possible because the gas cannot maintain its pressure needed to blow out the material below the first cut. Examples of profiles that are not suited for laser cutting are extruded aluminum profiles used for structural framing or automotive window frames.
Bevel cuts are another area where laser systems have limitations. Though a cut up to 30 deg is possible, the edge quality decreases as the bevel angle increases because the cutting gas is not able to continually provide the pressure needed due to the geometry of the cut.
Because of these sorts of challenges, each part being processed should be reviewed by experienced specialists – in addition to lab trials – to check on feasibility because some geometric shapes do not lend themselves to laser cutting.
Safety is a critical factor in 3D laser applications because the beam no longer stays pointed down on a flat sheet as in 2D processing. This means that appropriate safety protocols must be in place.
One of the primary uses of a 5-axis laser cutting system is for cutting hot-stamped sheet metal components for the automotive industry. The combination of high dynamics in 3D with repeatable cutting quality provides an economical solution that easily adapts for part design changes.
Other common uses of 3D laser processing are cutting hydroformed frames for the automotive industry and fuselage and turbine parts for the turbine industry (both aerospace and land-based).
3D LASER WELDING
Furthermore, 3D laser processing extends to 3D laser welding, which includes:
– Direct welding, where the processing head is close to the workpiece and cover gas and wire feed may be required.
– Remote welding via scanning optics, a popular process in the automotive industry that promotes a significant increase in output and a reduction of robots, floor space and consumables compared to resistance spot welding. (See Figure 2)
3D LASER METAL DEPOSITION (LMD)
This application uses the laser to melt/weld a metal powder that is blown onto the workpiece in a near-net-shape deposition with no voids. This process is used in a variety of industries, with aerospace/commercial engines, offshore and agricultural equipment being the major markets. (See Figure 3)
As you can see, there are many applications for 3D laser processing systems, making them a useful and economical tool for manufacturers everywhere. And the exciting part is that this technology continues to develop. Check back with me sometime in the future and I’m sure we’ll add to the already extensive list of applications for this incredible technology.
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About the Author: Frank Geyer is the product manager for multi-axis laser systems at the Laser Technology Center of Trumpf, Inc., 47711 Clipper Street, Plymouth Township, MI 48170, 734-454-7200, Fax: 734-354-9769, firstname.lastname@example.org, www.us.trumpf.com.