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Pricing matters when considering usage of plastics over metals

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Even though engineers these days are much better educated about the advantages of plastics over metals in many important applications, there is one myth that is very hard to kill - and that concerns pricing. 

Because thermoplastics have such outstanding advantages – high strength, lower wear, lower co-efficient of friction no lubrication, no corrosion – people tend to assume they must be much more expensive. 

This is so often not the case. Indeed, with one of the most ubiquitous and hard working of thermoplastics, Nylon (Ertalon Polyamide), the cost can actually be three, four and five times cheaper than metals or alloys that will not do as good a job. 

Have a look at the chart below, which is based on the cost of a one metre bar of 100mm diameter stainless steel, mild steel, aluminium, bronze and Nylon. Apart from the obvious weight advantage of Nylon (which translates into better handling, easier installation and generally less friction and wear) the cost benefit is compelling. 

The arguments for Nylon become more compelling when you consider the general advantages it has over all the metals above: including low density and high specific strength; corrosion and chemical resistance; electrical and thermal insulation; and being easily shaped and coloured. 

Bushes, bearings and gears 

The comparison becomes even more interesting when you look at some of the most common of industrial components for which plastics vie with metals, including bushes, bearings and gears. In this application plastics not only offer a lower co-efficient of friction and don’t require lubrication (maximising transferred power and minimising maintenance and noise) but also they increase the wear life of the component many times over – as well as reducing wear to the counterface. 

Wire rope sheaves show similar advantages, with these lightweight and corrosion-resistant components offering two to three times the sheave wear life while also offering 2-6 times the rope life in applications such as mobile, tower and container cranes.  

Indeed Polyamide Ertalon (to give Nylon its scientific name) is changing the habits of component engineers who until recently showed a fixation for using metal-based industrial components in original equipment manufacture and maintenance requirements. 

As Ertalon’s scope for application is virtually endless in most industries, each requirement can almost always be facilitated due to subtle variations in physical properties afforded by a different additive in each grade of the product. 

Naturally some of these formulations may be more expensive than others, such as the new miracle plastic Nylatron 703 XL. This amazing product features ‘Zero Slip-Stick’ performance for precise and efficient motion control of machinery components including wear pads, bearing blocks, wear guides and linear bearings. But even the most sophisticated members of the Ertalon family are nowhere near as expensive as may commonly be supposed - and offer outstandingly cost-efficient features tailored to their particular application. 

Supplied and engineered by Dotmar EPP, the range of Ertalon polyamide stock shapes can be engineered to suit applications requiring high mechanical strength, stiffness hardness and toughness, fatigue resistance, high mechanical damping ability, good sliding properties, noise damping, electrical insulating, dielectric properties and excellent wear resistance. 

These unmistakable characteristics and performance level are equal to - and often better than - those embodied by metal alternatives, but at much less expense. 

As a result, production efficiencies are increased and downtime greatly reduced in applications extending across manufacturing, materials handling, mining, marine, transport and packaging industries as well as general engineering.  

Specific applications include sleeve and slide bearings, wear pads, support and guide wheels, conveyor rollers, tension rollers, sleeves for wheels and rollers, pulleys and pulley-linings, cams, buffer blocks, hammer heads, scrapers, gear wheels, sprockets, seal rings, feed screws, starwheels, cutting and chopping boards and insulators

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