Belt Conveyor Delivers Faster Part Cycle Times

Three companies collaborate to improve productivity, reduce operating costs, and create innovative new products, millions of parts per year.

By Staff -- Control Engineering, 12/15/2006

Key outcomes of a successful automation project include improved productivity, reduced operating costs and creation of innovative products. Three companies collaborated to achieve those results:

• Sunnyvale, CA-based Cepheid Inc.—a relatively new company applying breakthrough microfluidics and microelectronics technologies to new test systems for DNA analysis;
• Stirling Engineering Inc., in nearby San Jose, CA—designer and builder of automation equipment; and
• Belt Technologies Inc., of Agawam, MA—manufacturer of metal belts and related equipment.

Combining microelectronics and microbiology—which Cepheid calls microDiagnostics—the company is working to develop proprietary products aimed at complete, cost-effective automation of complex DNA-detection procedures. Recently, Cepheid developed a significantly faster thermocycles test used to detect the presence of specific DNA in a test sample. The process can take as little as 10 minutes to complete.

While the test procedure was markedly faster than competitive tests, and faster even than the company’s previous offerings, Cepheid’s manufacturing process for the test was not speedy. Initially, the company was manually producing a disposable reaction tube—a key test component—in quantities of only 400 tubes daily. Obviously, some degree of automation was necessary to produce the annual 18 million parts required to meet expected market demand.

Increased throughput was only half of the equation; cost saving was the other. Cepheid’s mechanical engineer, Doug Dority, said: “After performing the financial analysis, it was clear that we could reduce the overhead on the part cost by developing a faster part cycle time. Given the number of parts we would be producing, the savings could be significant.” After investigating several options, Cepheid turned to Stirling Engineering, which specializes in designing and building custom factory-automation conveyors. According to Greg Stirling, metal belt technology would improve flexibility and reduce cost and over-all dimensions of the assembly line. It also would provide a very clean process for Cepheid. Belt Technologies would supply the belts.

Ultimately, Cepheid engineers Dority and Ron Chang chose Stirling after evaluating competitive quotes from other machine builders who proposed rotary table concepts. Stirling’s concept was not only more cost-effective, they said, but it would also quadruple the parts capacity compared to the second-best solution. Ultimately, Stirling recommended and built an automated assembly line that incorporated 12 assembly stations and a cycle time of three seconds. A machine with eight channels met the desired production rate and would yield more than 20 million parts annually.

Stirling’s process was fast and “provided a very clean parts transfer, as clean as any I’ve seen,” said Dority. “Cepheid had looked at various conveyor products and had a problem with the high mass of the conveyor. The obvious solution was metal belts, which provide low inertia and excellent repeatability. Plus, in the future, we could also extend the line very easily, with the belts’ flexibility.”

Metal belts offer advantages over similar products, including belts made of other materials. They have unique properties that result in superior precision control, longevity, and cost-effectiveness. In many cases, they’re preferable to other belt types. Because they do not stretch, variations in surface speeds are minimized. Metal belts from Belt Technologies do not require any lubrication, offer unlimited travel lengths, and are available in various alloys.

Once Stirling completed its initial engineering design, the concept was presented to Belt Technologies’ Rich Lunden, who provided exact metal belt and pulley design specifications. Stirling subsequently incorporated Lunden’s information into the conveyor design. Belt Technologies provided drive and idler pulleys, metal belt, and timing screws used to attach the cleats.

Metal belts minimize contamination issues and are better for precise positioning, Dority stated; the conveyor, delivered on schedule and under budget, has been running flawlessly since installation. The operation produces 1,800 units hourly and is easily managed by one person.

“Essentially, Stirling built an experimental line at the facility, with a limited budget. Cepheid saved substantial sums as a result, plus the prototype line performed well enough to become a permanent solution,” he explained.

Dority says that the conveyor’s flexibility provides Cepheid with significant competitive leverage, allowing easier adjustments to projects already underway.