Laser systems offer flexibility from prototyping to production
September 14, 2004
Products change, and so do manufacturing methods used to make products. In the tube and pipe industry, however, manufacturing changes have been few and infrequent over the past few decades.
It's no secret that manufactured products change continuously. Technological developments and higher consumer expectations are two of the forces that drive changes in nearly every manufactured item.
Just as manufactured goods change, so do the approaches used to manufacture them. From the 1950s to the 1970s, for instance, manufacturing success hinged on productive capacity. During the 1980s, quality became more important in consumer purchasing decisions. In the early 1990s, product cost reduction was a primary focus aimed at gaining and maintaining a competitive edge in the face of mounting foreign competition.
Manufacturers that have survived the last 40 to 50 years generally are those that have been flexible enough to respond to the ever-shifting landscape as the market demands of capacity, quality, and cost reduction emerged, one after another.
U.S. manufacturing is continuing its drive to maintain its competitive position in the global metal fabrication market while a new approach is emerging. In the current decade, innovation and new-product development are the most important weapons in a manufacturer's arsenal.
Despite the changes in the manufacturing climate, one thing has remained relatively constant over the last few decades, and that is the level of technology used in the tube and pipe fabrication industry. A conventional fabrication process consists of several steps—cutting to length, coping the ends, and making side wall openings of several shapes and sizes. Some parts require sawing, drilling, coping, machining, punching, and deburring, necessitating up to six different machines to complete.
Meanwhile, other technologies and increasingly sophisticated manufacturing systems have emerged in response to fabricators' needs. Manufacturing systems that perform several functions can help fabricators and manufacturers compete by reducing the number of machine operators required, handling of semifinished parts, necessary floor space, work-in-process inventory, and complications in production planning and control.
Industrial lasers are among these newer technologies. A laser-based tube cutting system can consolidate up to six fabrication steps into one continuous cutting process. Such systems are based on standard, proven configurations that are now being used in more than 350 installations in Europe, Japan, and North America.
These laser-based tube cutting systems have brought process and economic benefits to the fabrication and assembly of mechanical tubing into a range of end-use products. These benefits are concentrated in three primary areas:
|Whereas some laser machines accommodate straight tube only, others can cut features into tube that has been bent into its final shape.|
Laser-based tube cutting systems can cut round, square, rectangular, flat oval, triangular, and many other tube shapes.
Two types are available: systems for cutting parts from straight lengths of raw material and systems designed to cut features into tubes that already have been bent into their final 3-D form.
Systems that cut straight tubes are delineated by size and length of raw material they can handle. One system type can handle tubes up to 6 inches in diameter and raw tube lengths up to 28 feet, while a larger class of machines is available for cutting up to 11.8 in. diameter and up to 40-ft. lengths.
Some systems are available with a fifth or sixth axis of motion in the cutting head, which facilitates applications such as bevel cutting for weld preparation or straight hole cutting for a pass-through fit.
Cutting tubing after it has been bent into its final form helps to ensure tight location tolerancing of the features to be cut. Multiaxis laser-based cutting systems are suitable for tubular components requiring accuracies of ±0.005 in.
Laser tube cutting systems have several loading options. A simple system allows manual loading of single tubes, whereas a complex machine uses an automatic tube bundler to load up to 9,000 lbs. of material. The systems also include automatic unloading of tubes cut to specification and discharged to several different locations from the machine.
In addition, the systems are flexible and able to accommodate changes in tube configuration and part design in a few minutes. In most cases, the setup and changeover are fully automated under the control of the system CNC and are determined by the part program. Typical changeover time from one round tube size to another is less than one minute. Changeover from round to square or rectangular is usually three to four minutes.
Polaris Industries evaluated, purchased, and installed a laser-based cutting system in 2000. The driving force was a need to improve the efficiency and quality of the company's tube fabricating operations. The decision to implement laser equipment also led to using the technology's flexibility to integrate its capabilities into its new-product design functions.
Rapid changeover gave the company the flexibility to do small lot sizes or long production runs, if needed, without losing the prod-uctivity benefits. Studies by Polaris Industries' Manufacturing Engineering Department measured the labor productivity needed for 14 parts totaling 650,000 parts per year. The studies found that the company had achieved a 74 percent reduction in labor-hours, on average, when it switched to using laser-based tube cutting equipment. In examining whether production volume had any appreciable effect on those savings, the company discovered that the parts being cut on the laser tube cutting systems ranged from a low of 3,000 to a high of 62,400 pieces per year. Labor-hour reductions were between 70 percent and 84 percent, regardless of the annual production volume.
Some laser tube cutting systems come with standard software control packages that include a scrap reduction cycle capable of minimizing scrap to 3 in. at the end of each piece of raw stock. Additional features include the ability to program multiple part numbers from the same piece of raw material, making it possible to segregate different parts automatically to different locations near the machine, which, in some cases, is an advantage in downstream assembly processes.
Some software packages can record and report on a minute-by-minute basis the machine's utilization over time to monitor productivity by the hour, the shift, or other extended periods to support effective system management.
|Designers can use the bend notching technique to reduce the number of parts from four to one in a multicomponent rectangular frame.|
Laser-based tube cutting systems typically have axis positioning tolerances of ±0.002 in. When combined with the typical tolerance variations in bow and twist in tubular material, these systems generally produce finished parts with tolerances in the range of ±0.005 in. to ±0.007 in.
Finished parts are also more consistent, not only because of the accuracy of the machine, but also because the finished parts are not subjected to additional tolerance losses that can creep in when using multiple machines.
Greater accuracy and consistency reduce assembly time by eliminating much of the time it takes welders to force misfitted parts into the final assembly fixture and to fill gaps between assembled components. Tight part tolerances produced by laser tube cutting systems also enable robotic welding.
Flexible manufacturing systems help designers reduce the number of parts in an assembly. Benefits include fewer parts to track and handle, simplified fixturing, and up to a 25 percent reduction in welding.
Self-locating features also can help to reduce assembly costs. Cutting slots in one member and tabs or hooks in a mating piece allows a complete assembly to be snapped together in a simple fixture. This technique generally eliminates the need for tack welding.
Product life cycles are decreasing, and this has an impact on nearly every business and on the entire manufacturing supply chain. This is driven, in part, by start-up and low-cost producers making inroads into established companies' markets, particularly at the bottom end of the product ranges. To separate themselves from the pack, established companies must focus on new-product development.
According to "Blueprint for Renewal," an article in Industry Week (September 2002 issue, p. 33), it is commonly accepted in the new-product development function that 70 percent of a product's cost is determined in the design stage. Choosing equipment that allows design flexibility can help to reduce the single largest cost associated with product development.
Tubular part design is eased by CAD/CAM software that is available as part of the standard package with all laser tube cutting systems. These software packages typically allow a manufacturing engineer to go from a newly released part drawing to a finished prototype, part in hand, in less than 30 minutes. A laser system eliminates the cost and lead-time associated with hard tooling and reduces the cost of last-minute design changes along the way.