Because they need no oiling and have no moving parts, bearings made from internally lubricated polymers can provide maintenance and cost advantages over plain and rolling-element bearings made from metal. But load and thermal limitations that have kept plastic bearings out of many heavy-duty applications--until now. A new bearing material from igus GmbH dramatically extends the performance of mass-produced polymer bearings.
Called iglide Z510, the new polymer compound readily withstands static loads up to 43,500 psi at continuous use temperatures as high as 500 F, according to Christoph Klingshirn, one of the company’s materials engineers.
The company keeps the exact nature of all its polymer compounds secret, though Managing Director Gerhard Baus says most are based on modified semi-crystalline materials--like nylon, to take one example. Unlike most of the company’s bearing materials, though, igus bases Z510 on an amorphous polymer with an extensive custom blend of additives.
Some of igus’ earlier iglide bearing materials could nearly match Z510 in the temperature department--but only at about half the maximum load. “In 2004, the maximum load for any of our bearings was 25,500 psi, and we didn’t think there was much to be done about it,” Klingshirn says.
So Klingshirn says he was “quite surprised” when the company’s ongoing materials development program yielded a polymer that took such high loads. And Z510 does more than hold up under high static loads: The material has performed well in the the company’s rotating and oscillating wear tests--though not always better than some of the company’s earlier iglide materials.
But Z510 has a big advantage when it comes to modulus retention at high temperatures. Baus explains that previous materials can lose enough stiffness with rising temperature to loosen in their housings. For example, one of the company’s top performing materials, iglide T500, can lose its press fit at roughly 300 F. This loosening wasn’t necessarily a big deal. Engineers could design around it by adding retaining features or extra components to keep the bearing in place. Z510, however, needs no such retention help. “It holds its press fit nearly to its maximum temperature,” Baus reports, pointing out that that the improved press fit capabilities can help engineers simplify housing designs and possibly reduce component count.
A new bearing polymer from igus stands up to temperatures as high as 500 F and loads as high as 43,500 psi--about double the load the company’s earlier plastic bearings could tolerate.
For all its advantages, Z510 has some limitations that will keep the other iglide materials in use. Remember that some other materials can at times exhibit better wear resistance, so they might remain a better choice at lower temperatures and loads. What’s more, Z510 currently seems to work best under specific loading conditions. The material has, for example, performed best in wear tests with slow oscillations, according to Klingshirn. At higher oscillations, the material didn’t perform as well as previous iglide materials. Plus the new material seems to be noisier than earlier materials. Still, Z510’s ability to withstand high loads and temperatures will could open up a number of new applications for plastic bearings. Baus says the material’s first use will be in truck’s lift gate, an application that previously needed metal bearings. He expects a number of other applications in agricultural and packaging equipment as well.
In-stock sizes for bearings made from Z510 have yet to be determined, but the company will over the next few months add all the relevant dimensional and performance data for Z510 bearings to its on-line bearing selection tool (available at http://www.igus.de/Main_fs.asp?LANGUAGE=E&KATALOG=XIGLIDUR&GO=IGLIDUR_EXPERTE).
For more information on igus, go to www.igus.com.