Chain sprockets printed in 3D make e-bikes whisper

• What was needed: plastic pinion
• Manufacturing method: selective laser sintering
• Requirements: high wear resistance, good sliding properties, long service life
• Material: iglidur I3
• Industry: bicycle sector
• Success through collaboration: quick configuration of the component in the online 3D printing service, quieter operating noise than with metal

The application at a glance:
E-bikes are becoming increasingly lighter and also very quiet. During operation there are hardly any motor noises. However, resourceful inventors, such as Lars Hartmann from Reichshof are not satisfied with that. The bicycle chain was too loud for him. A metallic sprocket served as a guide roller for the chain to prevent it from colliding with the frame but was very loud. In search of a remedy, he remembered an offer from igus which he had encountered at a trade show: The 3D printing service, which manufactures individual components cost-effectively with a 3D printer.
 

The 3D printed plastic pinion made of iglidur I3 in use

Problem

The standard metal sprocket made very loud running noises on the electric bike. The sprocket was the guide roller of the chain so that it did not touch the frame. The friction noises, however, made the e-bike sound like a tractor. Accordingly, Lars Hartmann set out to find a material that had the same running properties as the metal sprocket but was significantly quieter. Other requirements for the material were good sliding properties and a long service life, as well as high wear resistance when interacting with metal.

Solution

In the context of his work for VMA Getzmann GmbH, manufacturer of stirring, dispersing, and fine grinding systems, he tested machine parts that igus had produced with its 3D printing service. The results were so good that Lars Hartmann considered the printed parts for his e-bike as well. It was the perfect solution for the hobbyist: "The standard metal pinion generates a lot of operating noise. We drew it and had it printed at igus from iglidur I3. Getting the part was simple and fast. We used the 3D printing service to upload the relevant data, chose the material, and ordered the quantity." The chain sprocket has been in used in two bikes for several months – and the noise level has decreased significantly, Hartmann is pleased to say.

Optimum coefficients of wear and stability

The material in use, iglidur I3, is of course also suitable for industrial application and mass production. It is especially attractive due to its low coefficients of wear and high stability and is processed with selective laser sintering (SLS).

In addition, igus has developed the iglidur I6 for particularly high demands with regard to wear resistance and for a long service life. In tests, the high-performance plastic beats machined gear wheels made of common materials such as POM and PBT. A worm wheel with 5Nm of torque and 12rpm was tested. The gear made from the iglidur I6 laser sintering material exhibited minor wear after one million cycles, when the test was complete, and was still fully functional. That was significantly better than machined gears – POM gears exhibited total wear after 621,000 cycles, while milled PBT gears broke after just 155,000 cycles. Also part of the test: a gear made of the PA12 laser sintering material. Its high coefficient of friction caused it to stop after 521 cycles.

Left: POM gear, breakdown after 621,000 cycles
Right: iglidur® I6 gear, low wear at 1 million cycles

Easy to configure

At the same time, designers can profit from the igus® gear configurator. It allows you to configure custom gear wheels or chain sprockets, even in special dimensions. In a few steps, the user only needs to enter the specifications of the required gear wheel (such as the tooth module, number of teeth, width and inner diameter). This automatically generated a 3D model that can be exported as a STEP file. By uploading the file in the igus 3D printing service, the configured gear made from the new durable laser sintering material iglidur I6 for gears can be ordered immediately. With one click, the user can order his/her wear-resistant gear with no minimum order quantity or request a quotation. Already within three days, the custom-made part is ready for shipment.
 
 

Easy configuration of gears with the igus gear configurator