. If this seems like a rather limiting requirement, think about it. But if you think you can simply mold a plastic spring in the image of its metal predecessor, think again. "Others," she says, "are designing springs, but don't know it. It loses 60 percent of its original force after 10,000 hours (about a year), and two-thirds of its force after 100,000 hours (about 11 years). The input pinion of a dual drive washer transmission has two radial antibackup leaf springs molded into its sides. Such consolidation often requires a reassessment of the design of the product. They've developed some handy guidelines for spring applications. Acetal copolymer is the material of choice for Ticona, says Smith. It has good creep resistance and retains its toughness at high temperatures. Polyethylene and polypropylene are inexpensive, but exhibit poor resilience and poor resistance to creep. For some companies, he says, scrap rates approach 5 percent. Dec 19, 2017 - Bernie demonstrates how to finish your zig zag spring installation by stabilizing them with twine. Only the spring in the middle (of a 9 spring configuration) is not tied to a wood rail. On the design front, remember that plastic coil springs are not your only option. A minimum of 5 springs should be used under each seating area i.e. Consider the products pictured throughout this story. Copyright © 2020. The well-known snapfit buckle is sprung only to lock and release, hardly a full-time job. Zig-zag or sinuous springs are not as long lasting as coil springs. Lines and paragraphs break automatically. The operating temperature also affects plastic spring performance. If you're designing a new spring, or replacing an existing spring, recovery time should be at least equal to the time under load, says Smith. chair = 5 springs, 2 seater sofa =10 springs. Number 8860726. Between the tacks and the springs, the twine is kept very taut. Acetal copolymer loses 50 percent of its spring force after 1000 hours (about six weeks). The cord lock is used only to adjust the tension on the cord. Zig-Zag Springs. It will probably mean eliminating several parts and completely redesigning the assembly to accommodate the springs of plastic. Nylon is tough when dry, but stiffness can decrease up to 25 percent when exposed to 50 percent relative humidity. Like most springs that use plastic, this well-known buckle design is used intermittently to engage and disengage the lock, giving the spring time to recuperate in between. Unfortunately that does not mean that the problem is not with the springs. Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Older couches tend to have coiled springs, while newer couches have zig-zag springs. Linear polyphenylene sulfide is more brittle than acetal copolymer and better for high-load, low-deflection applications. https://www.plasticstoday.com/sites/all/themes/penton_subtheme_plasticstoday/images/logos/footer.png. The answer to your question regarding if zig-zag (no-sag) springs wear out is no, they never wear out. In fact, says Fletcher, a lot of designers don't realize that plastic can be a spring. This design replicates the action of a coil spring, but uses a high-modulus resin and flexible beams to achieve greater stiffness than molded coil springs. Registered in England and Wales. The payoffs are lower cost, lighter weight, and easier assembly. The material you choose should be partly determined by its resilience. If they're broken you may need to bring your couch to an upholsterer.