|An automated assembly line uses metal belts to boost production capacity of DNA-analysis equipment to four times that of proposed rotary-table designs. At $450,000, the metal-belt system also costs 40% less than the proposed cost of a rotary-table design.|
Three companies recently collaborated to increase production capacity of DNA-analysis equipment from 146,000 to 24 million parts/yr using metal belts and factory automation. Cepheid, the Sunnyvale, Calif., company that manufactures the equipment, developed a 10-min thermocycle test to detect the presence of specific DNA in samples. Although the procedure is faster than the company's previous offerings and competitors' tests, it was still deemed too slow.
Cepheid was producing a key component - disposable reaction tubes - by hand and completing only 400 tubes/day. To meet rising demands, however, the company needed to ramp output up to at least 18 million parts/yr. Stirling Engineering Inc., San Jose, Calif., a general-contracting firm specializing in designing and building custom factory-automation systems, proposed an automated system that could produce 24 million parts/yr and manufacture four separate products on the same line.
Stirling's proposal called for metal belts, from Belt Technologies, Agawam, Mass., which offer several advantages over other power-transmission devices. Unlike rubber or fiberglass timing belts, for instance, metal belts do not stretch, and surface-speed variations are minimal. Metal belts also run without lubrication, offer unlimited travel lengths, and are available in a variety of alloys. In addition, metal belts are often selected over linear actuators, leadscrews, and chains, because of their high strength-to-weight ratio, durability, and positioning precision.
"Stirling's process was not only fast, it provided a very clean parts transfer," reports Doug Dority, a Cepheid mechanical engineer. "We looked at other conveyor products and had a problem with high mass," Dority adds. "The obvious solution was metal belts, which provide low inertia and excellent repeatability. Plus, in the future we can easily extend the production line due to the flexibility of the belts." According to Dority, the system has been running flawlessly since April 1999. The operation produces 1,800 units/hr, and is easily managed by one person.