Technical staff at igus, a leading manufacturer of polymer materials for moving applications, have conducted exhaustive tests comparing the performance of traditional polyoxymethylene (POM) with the company’s latest 3D-printing materials. POM has been a standard engineering plastic for wear-resistant and mechanically loaded components for decades, and its strength has become the benchmark for components such as gears, bearings and bushes. With new tribological 3D-printing materials now available, igus engineers wanted to evaluate the options these open up, particularly for customised or low-volume parts and replacement components.
The new igus white paper compares its iglidur 3D-printing materials directly with POM to examine friction, wear and service life across different applications. The results indicate that appropriately selected 3D-printed materials can provide a practical alternative to conventionally machined POM in a number of applications. The comparisons were based on grease-free testing, relevant for applications where additional lubrication is undesirable or impractical.
igus develops its iglidur 3D-printing materials specifically for applications involving friction and wear. The materials incorporate solid lubricants into the polymer, allowing components to operate without external lubrication. They are available for several additive manufacturing processes, including FDM filament, SLS powder and DLP resin. The testing considered both the properties of the material and its behaviour as a finished component, which is important for tribological applications because friction and wear are influenced by load, speed, mating surface, component geometry and operating conditions.
According to igus, its 3D-printing materials produced lower wear and more stable friction than POM in the tests conducted. Gear testing produced particularly significant differences, with the company reporting more than eight times the service life in VDI 2736 testing and ten times longer service life in Framo Morat gear testing. Pivot testing recorded up to five times less wear than POM. These results apply to the specific materials, components and test conditions used and should not be interpreted as a universal replacement factor for every POM application. They nevertheless demonstrate the potential of tribological additive manufacturing for functional components.
Gears under rolling and sliding contact
Gears are particularly demanding components because their teeth experience a combination of rolling and sliding contact under repeated loading. Progressive wear can alter tooth geometry, increase backlash and eventually result in tooth failure. In one igus test, a gear manufactured from iglide i3 by laser sintering was compared with a machined POM gear in a rack-and-pinion arrangement, and the 3D-printed iglide gear lasted five times as many cycles before failure as the POM gear. Another test involving iglide i6 worm gears recorded more than one million cycles while remaining functional, whereas the comparable milled POM gears showed significant wear after 321 000 cycles, with teeth eventually breaking at 621 000 cycles.
The choice of printing material can also be matched to the gear application. iglide i3 is suited to applications requiring higher strength, including spur and helical-bevel gears. iglide i6 has optimised sliding properties and is suitable for worm gears, while iglide i8-ESD is intended for applications requiring electrostatic dissipation.
Plain bearings and on-demand parts
Plain bearings provide another area where 3D printing can offer practical advantages. A conventional POM bearing is straightforward to produce in volume, but customised dimensions or small quantities can make conventional manufacturing less attractive. A 3D-printed component can be produced directly from a CAD model without dedicated tooling. This is particularly relevant where machinery requires an unusual bearing geometry, a replacement part is no longer readily available, or where only a small number of components are required. The same principle applies to lead screw nuts and other sliding components. Instead of using additive manufacturing simply to produce a prototype, engineers can use a wear-optimised material for the functional component itself. igus testing also indicates that its 3D-printing materials can perform in specialised environments, with tests of SLS-printed iglide i8-ESD plain bearings under water showing service life comparable to injection-moulded iglidur materials developed specifically for underwater applications.
The manufacturing advantage
Commenting on the tests, igus South Africa managing director Ian Hewat says material performance is only part of the argument for additive manufacturing. The other advantage is the manufacturing process itself, where 3D printing eliminates the need for conventional tooling and allows components to be produced directly from digital designs. A manufacturer can produce a single component or a small batch from a CAD model, and produce another version without creating new tooling.
“It can also reduce material consumption compared with machining a component from a larger block of material. igus reports potential production-cost reductions of up to 40% and material-waste reductions of up to 90% in the applications it has evaluated. For maintenance departments, the ability to manufacture a replacement component from a digital file can also reduce dependence on discontinued or difficult-to-source parts,” says Hewat.
“The comparison does not mean that POM has become redundant. It is a well-established engineering material with predictable characteristics and proven conventional manufacturing methods. For high-volume production of identical components, machining, injection moulding or other established processes can remain economically attractive. We think the case for 3D printing is strongest where production quantities are relatively small, where geometries are complex, or where a replacement part is needed quickly and the choice depends on the application rather than simply the material,” says Hewat.
Hewat notes that the paper found the materials highly suited to applications such as gears, plain bearings, lead screw nuts and other wear components, and that these should be considered for additive manufacture. The company also offers an online 3D-printing service that allows customers to upload a CAD file and have individual components or series manufactured using its own wear-resistant materials, and the service can be used to estimate component service life.
“In South Africa, we think the main significance of the POM comparison is that it shows engineers they have another manufacturing option. For customised, low-volume and replacement components, the combination of wear performance and on-demand production can make 3D printing a practical alternative to conventionally manufactured POM. We want to help engineers find workable solutions based on the requirements of the component and its production volume, rather than treating 3D printing as a technology reserved for prototypes,” concludes Hewat.
| Tel: | +27 11 312 1848 |
| Email: | [email protected] |
| www: | www.igus.co.za |
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