December 11, 2007
The new high-powered lasers allow fab shops to serve a broader range of custom needs.
Laser cutting originated for processing of sheet materials, but new, high-powered lasers, capable of processing heavier-gauge and plate materials, are moving lasers into the thick of part-making.
For the many industries that produce lots of flat parts, laser cutting can provide major lean production benefits. Today's high-power, high-output lasers can reduce processing steps, throughput time, and part-making costs. Laser cutting can duplicate some of the functions that punching, drilling. and machining equipment delivers, which quickens part processing, eliminates setup labor, and provides processing flexibility. It also eliminates tooling and fixturing expenses.
For the purpose of discussing the capabilities of an advanced laser cutting system, the conversation will concentrate on laser cutting systems with linear-motor drives and 5,000 watts of laser power.
On thick materials (see Figure 1), a 5,000-W laser can deliver cutting rates significantly higher than machining's:
On top of these speed advantages, the laser makes possible one-stop, start-to-finish processing of many kinds of parts. When part tolerances don't permit one-stop processing, the laser can be highly effective at roughing operations, particularly in reducing in-process time for lengthy roughing routines.
The productivity gains from laser cutting are greatest on parts with multiple features or complex geometries. For example, makers of circular saw blades were early adopters of laser cutting.
The quality of gears, sprockets, ratchets, and pawls can benefit from laser cutting. Figure 2shows an assortment of such shapes cut from various materials.
These high-powered lasers are beneficial to job shops in other ways as well.
No Setup or Fixturing. The laser merely requires that the sheet material be loaded on the pallet. No special setup is required.
A noncontact process, laser cutting requires no fixturing of material, eliminating machine downtime and operator costs for setup, as well as investment in fixtures. The part shown in Figure 3, for example, would require multiple tools and fixturings to machine its various size holes, slots, and web connectors.
Dual-pallet machines enable one pallet to be unloaded or loaded while another pallet is being processed. Pallet change takes only a few seconds. Lasers also can be configured with automated material handling systems to permit long periods of unattended laser processing.
Depending on part requirements, a lens or nozzle change may be required. However, nesting or batching software allows parts to be ganged by material type and thickness, reducing change frequency. Grouping parts can reduce changes to once or twice a day, perhaps even less.
Pallet/Table Capacity. The work zone is limited on most machine tools, except for special machines for aerospace and agriculture and construction equipment. A yard-square table is a fairly large machining center, while lasers provide four to six times that load capacity with standard 5- by 10-ft. or 6- by 12-ft. beds.
The greater table capacity permits nonstop processing—more parts per given unit of time—for leaner, faster production. In some cases, a ship set or assembly set of parts can be produced in the same run, further reducing work-in-process.
One of the industry's largest linear-motor-driven lasers with 8- by 20-ft., interchangeable pallets accepts standard 8- by 20-ft. mill size sheets for maximizing material purchasing. The large table can allow "done in one" processing on large parts or components and avoid weld-up of smaller cutouts.
The side panels for the separator in Figure 4previously required template layout, shearing, torch cutting of shaft mounting holes, drilling of smaller holes, and edge finishing—five handlings and operations to get a completed panel. Laser cutting of the 3/8-in.-thick stainless panels consolidated everything into a single operation.
Mixed-lot Flexibility. Lasers allow multipart and mixed-lot processing without fixturing, supporting manufacturing's drive to greater production flexibility. Software can group parts of similar material and thickness for batch running. Nesting software positions part shapes for the best material utilization. Small parts can be located in cutouts from large parts.
Hole-making. The laser enables various hole sizes and shapes to be created in a continuous process without tooling costs or tool change time. Lasers can effectively cut holes down to diameters equal to the material thickness. Figure 5shows an example of hole laser-cut in heavy plate.
Using rapid pierce capability, a 5,000-W laser can pierce 1/2-in. steel in 0.85 second, 3/4-in. steel in 2 seconds, 1-in. steel in 3.2 seconds, and 11/8-in. in 3.2 sec.]. Holes are created by interpolation of the laser beam. Depending on material characteristics, operator knowledge, and process gas application, holes smaller than the material thickness can be burned in short cycle times and without having to employ a different process that adds to throughput time.
The benefits can be exponential on large parts with many holes or cut-outs (see Figure 6).
High-speed lasers are especially productive on thin materials:
These are straight-line feed rates, but even on extremely contoured and complex shapes, cutting speed will average nearly 100 percent of the maximum feed rate. Linear motor drives are designed to help deliver these results. They can provide high acceleration and deceleration rates and deliver stiffness to maintain ±0.001-in. positioning accuracy.
Figure 7—a motor lamination—shows the kind of intricate parts that lasers can cut from thin material at very fast speeds.
On prismatic, straight-line parts, high-speed cutting can allow laser cutting of sheet metal cases, containers, cabinets, panels, and myriad similar components, especially on an as-needed basis to reduce work-in-process.
Laser capabilities can open up opportunities for creative designs and methods. For example, laser cutting allows use of tabs and slots to simplify assembly and reduce or avoid the need for fixtures in welding and joining.
The new, high-powered lasers help fabrication shops to serve a broader range of custom needs. Metal service centers can expand their value-added capabilities, especially by offering contract cutting of geometric and complex-shaped parts. Machine shops can find laser cutting a faster, lower-cost alternative to machining on plate work, while giving them the flexibility to process thinner materials and nonmetals, winning a wider customer base.
Lasers also can be a transformational technology for volume manufacturers of flat parts, offering a means to faster, leaner production.
The FABRICATOR® is North America's leading magazine for the metal forming and fabricating industry. The magazine delivers the news, technical articles, and case histories that enable fabricators to do their jobs more efficiently. The FABRICATOR has served the industry since 1971. Print subscriptions are free to qualified persons in North America involved in metal forming and fabricating.