Plastic drive train components offer benefits often unrealised in Australasia, including design flexibility, reduced noise, and the ability to operate without lubrication.
Other pluses include lower cost and weight, higher efficiency, (improved accuracy), and chemical resistance, says Pat Flood, NSW Manager of the national and international engineered plastics specialist, Cut To Size Plastics.
"Traditionally Australasian industry has been wedded to metal drive train engineering, which is suitable for a proportion of particular application needs. But the more our industries evolve, the greater the need to think carefully about the smartest use of materials for ‘Clever Country’ industries and design solutions. This is particularly true for rapidly evolving hygiene-conscious sectors such as food and beverage, chemical, recycling, water and waste water management, robotics and medical engineering."
Durable alternatives to metal with major design advantages in particular applications include Cut to Size’s WEARLON™ nylon ranges and Wearace™acetal engineering plastics. Gears and drive train components made from them can be moulded and precision machined into shapes difficult to machine in metal. Other functional elements, such as springs and pawls, can be incorporated into them, thereby consolidating parts and trimming the cost, weight, and complexity of geared speed reducers.
WEARLON™ nylons and Wearace™ acetyl ranges (above left and right respectively) each have major strengths in particular applications.
All WEARLON share major advantages such as high mechanical strength, hardness and stiffness, as well as high mechanical damping capacity. They offer good fatigue and very high wear resistance, with good sliding and emergency running properties. They are also suitable for machinery subject to constant moisture and washdown.
"These properties, along with good machinability, lend them to typical applications such as bearings, guides, chain wheels and guides, bushings and slide and guide plates," says Flood.
Other applications include toothed racks, mixer rollers, guide rails, rope pulleys, bearings, tappets, cam discs, gear wheels, transport stars, mixer blades, pump wheels, pinions, curved guides, crane supports and idler and guide rollers.
For particularly specialised applications, there are custom-engineered polyamides in the PA nylon family, including PA 6G, which is produced by the monomer casting process for even better strength and abrasion/wear resistance, while having a lower specific weight for improved balance and reduced vibration. A further modification of the PA6G polyamide is OILAMID, which is especially designed for sliding applications through the addition of oil, solid lubricants and stabilizers.
"Engineering for specific outcomes, in the case of OILAMID, results in a product with excellent sliding properties, exceptional wear resistance, even lower moisture absorption and better dimensional stability."
Oilamid Technical Data Sheet available here.
Wearace™ polyacetal, while typically specified for handling lesser loads than nylons, is eminently suitable and highly cost-efficient for sliding, guiding and roller elements of materials handling machinery.
Being physiologically inert, Wearace is highly suitable for food contact applications in natural form. Its main properties are high stability, high rigidity, high hardness, good impact resistance at low temperatures, low level of moisture absorption and good creep resistance. Complementing the physical advantages are a high fatigue and impact strength (even at low temperatures) and good electrical insulating characteristics. In addition, because moisture absorption is low, the Wearace stock part's influence on mechanical and electrical properties is minimised.
"Products such as Wearace derive their mechanical properties from their highly crystalline design, which makes them ideally suited for machining on automatic lathes," says Flood, who has more than 30 years’ experience in specifying engineering plastics Able to maintain its integrity under harsh operating conditions, Wearace is strong, hard and rigid. Its good sliding properties and a low co-efficient of friction ensure that performance requirements are consistently met and that wear and maintenance downtime are minimised.
The Wearace range’s structure facilitates application across an extensive range of industries, including machine construction, electronics, medical equipment and chemical processing.
Typical uses that benefit from Wearace’s properties include gear wheels with small moduli, cams, heavily loaded bearings and rollers, bearings and gears with small clearances, valve seats, snap fit assemblies, and insulating components for electrical engineering and parts which operate continuously in water of 60 deg C – 80 deg C. Industry-specific examples are scraper blades on gelatine extruders, buffer blocks on electromagnetic bogie brakes and ratchet wheels on stapling machines.
20 years of progress
"The use of plastics in drivetrain engineering has come a long way over the last 20 years, "said Flood. "From previously being considered only suitable for light, low-power and non-critical applications, engineering plastics today have moved out into areas such as bevel gears, metric gears and worm gears. Now cams, lugs, ribs, webs, shafts and holes are moulded into plastic gears in one integral design in a single operation, opening the door to significantly lower production costs in areas as diverse as automotive, conveyor and feeder drives, through to materials handling, packaging and robotics.
"But, as with all precision engineering, specifiers must be particular in their selection of the best materials for maximum suitability for purpose, initial cost- efficiency and whole-of-lifespan.
"There is often an investment of knowledge required in innovation - and it is essential that users of engineering plastics have an experienced supplier partner – but the rewards of being ahead of the competition far outweigh the risk of overtaken by these superior technologies."