Convincing conservatively minded engineers to specify plastics in demanding applications instead of long-used, traditional metal materials always has been a challenge. Igus GmbH, founded in Germany 40 years ago to injection mold bearings from engineering thermoplastics, decided late last year to launch a design contest to promote innovative applications of its products and to raise awareness of the benefits offered by plastic bearings.
It dubbed it ``manus: the first North American plastic bearing design contest,'' with manus (Latin for ``hand''), symbolizing ``the courage and tenacity'' in implementing new applications for such products. Pulled together in just three months, the contest attracted more than 60 entries, more than twice what was expected, according to Tom Miller, business unit manager for iglide-brand bearings for East Providence, R.I.-based Igus Inc. Miller, speaking Feb. 23 during the National Design Engineering Show in Chicago, revealed the following winners:
* First place (and $5,000): Six Flags Theme Parks in Valencia, Calif., for its use of the iglide Z plastic bearing on the new X roller coaster, the world's first ``four-dimensional'' coaster.
* Second place ($2,500): Harriston Industries of Minto, N.D., for successfully substituting iglide J bearings for oil-impregnated bronze bearings in the pick arm of its automatic potato planter.
* Third place ($1,000): Nova Biomedical in Waltham, Mass., for using DryLin R bearings on the two-axis tray and both DryLin R and DryLin N linear slides on the three-axis probe in its immuno-assay biotechnical instrument.
The manus panel of judges - comprising Miller, two science and engineering professors and a senior editor for Design News magazine - gave top billing to the Six Flags project based in part on the application's creativity, technical advancement and economic impact.
Jeff Hudgins, Six Flags corporate engineer, said that after the coaster had operated for six months continuously in the height of the season, inspections revealed ``virtually no noticeable wear on bearing or shaft.''
``Maintenance has been reduced by 95 percent and annual cost of replacement parts has been reduced by at least 54 percent.''
The plastic bearings also needed to be highly flexible to provide the high level of vibration dampening needed for optimal performance. ``My application was one of the most demanding on the ride,'' Hudgins said.
Certainly, the need for such dampening is easy to comprehend, once one sees the X roller coaster in action. Riders strapped into seats with a harness spin independently 360 degrees forward and backward on a separate axis, creating a ``don't know what to expect next'' sensation. Perched on the edge of a 20-foot-wide, wing-shaped vehicle, riders plummet 200 feet head-first and face down, and race at 76 miles per hour spinning head over heels, twisting and turning, along a 3,600-foot-long, steel track.
A special component of the coaster's chassis, called the X-bogie, enables the unique rotation of the seat on the X trains. It has four wheels that travel along the track and are attached to pivot housings that create the suspension. Loads induced on the vehicle components tax both the bearings and lubricants, while space restrictions make it difficult to lubricate or to perform regular maintenance.
Second-place winner Harriston Industries said use of Igus' iglide J bearings in its potato-planting pick arm has increased the parts' lifespan by five to six times, and at a cost 70-80 percent lower than the bronze bearings with graphite plugs that it previously used. Abrasive conditions - caused by high salt content in the air on the East Coast and by high levels of volcanic ash in the soil on the West Coast - used to cause high wear and significant corrosion.
``We were suffering tremendous failures,'' Harriston research and development specialist Dave Paschke said at the Design Show. ``We would probably have been out of business'' if the firm had failed to solve the problem.
A six-row potato-planting machine does 12-20 cycles per minute, and each machine uses 144 bearings. The bronze bearings needed to be changed at least twice a season, with each refitting taking at least five hours. Paschke said Harriston has been using the plastic bearings for two years now, and said, ``I have yet to find a bearing comparable to it.''
Winner of the bronze manus award, Nova Biomedical, opted to use Igus DryLin R linear bearings, since the bearings on its biotech instrument need to be lubrication-free so as not to contaminate the saltwater fluids involved. It also had to be maintenance-free because the medical-technician end users would not be qualified to perform regular upkeep.
Nova also chose plastic linear guides for its three-axis probe since it uses a cantilevered arm that needs to be lightweight and accurate.
Privately held Igus employs 850 worldwide, including 118 in North America. The firm develops and produces 16 proprietary compounds, and manufactures more than 28,000 stock products across three product lines - all at a single, 350,000-square-foot plant at its headquarters in Cologne. A spokewoman declined to provide details about the makeup of the firm's compounds, other than to say each features three components - a base resin, a dry lubricant and some type of reinforcing fiber.
Gunther Blase started the company in 1964 in his garage to injection mold custom plastic bearings. Five years later, at the suggestion of a textile-machinery customer, the firm introduced a line of plastic cable carriers, dubbed Energy Chain systems, which previously had been made only in metal. Cable carriers guide, protect and extend the life of cables and hoses that are attached to automated - and usually mobile - machinery.
In 1990, five years after establishing East Providence as its North American headquarters, Igus developed its Chainflex line of continuous-flex power cables, specifically for demanding energy chain applications.
Today the firm is run by the founder's two sons, President Frank Blase and Vice President Carsten Blase. It generates some $30 million in U.S. sales, with bearings accounting for about $7 million of that total.