Wear-resistant clockwork parts from the 3D printer

• What was needed: Components for a mechanical clockwork
• Manufacturing process: Filament extrusion (FDM)
• Requirements: High abrasion resistance, good mechanical characteristics, detail accuracy
• Material: iglidur® i150
• Industry: Model making
• Success through cooperation: improved wear resistance, significantly higher service life of the components, more regular running of the escapement and thus of the movement as a whole

The application at a glance:
As part of a Jugend Forscht project, Kai Schmidt-Brauns constructed a completely 3D printable movement and compared a mathematically calculated profile curve of an escapement of a mechanical movement with an empirically determined profile curve. To test the respective profile curves, he printed a mechanical movement based on his mathematical model. In addition to the tests with components made of conventional PLA, the student from Wolfsburg tested the different profile curves with components made of the tribofilament® iglidur® i150. This confirmed a better performance of the escapement with the igus® material. Thanks to the tribologically optimised filament, components that are exposed to particularly high mechanical loads were able to achieve a significantly longer service life and more regular running than parts made from conventional PLA.

In order for a mechanical movement to run precisely, the geometry of all components of the mechanism must be determined exactly and the friction between moving parts must be minimised. The aim of Kai Schmidt-Brauns' project was to design an escapement mechanism for the 3D printable movement and then determine its geometry using a mathematical model. Although the mathematical model resulted in a more regular movement, the question arose as to other ways of making the movement even more accurate. In the tests with 3D-printed components made from conventional PLA, the heavily loaded parts, such as the ratchet (consisting of a ratchet wheel and ratchet ring) in the winding mechanism, did not have a particularly high service life.

After the tests with the movement made of conventional PLA, Kai Schmidt-Brauns replaced critical components with specimens printed from the igus® tribofilament® iglidur® i150. The comparison revealed that the sliding and static friction between the components made of iglidur® i150 was significantly reduced. In addition, thanks to the high wear resistance of the igus® material, the service life of the ratchet was increased and a more regular running of the escapement was observed.

Jugend Forscht is a German competition for young talent for pupils from the 4th grade up to the age of 21. Participants can work on and submit problems of their own choosing in the fields of maths, computer science and natural sciences. As part of this competition, Kai Schmidt-Brauns from Wolfsburg first created a mathematical model to determine the exact geometry of the components of a 3D-printable escapement mechanism. In particular, this involved the profile curve of the profile wheel, which he was able to calculate from well-defined parameters. The escapement of a watch is the part that determines the accuracy of the watch. The escapement mechanism "inhibits" the gear train at regular intervals, for example with the help of an anchor, and ensures that one minute in the clock corresponds to one minute and does not sometimes take 61 and sometimes 55 seconds. In the next step of the project, Kai Schmidt-Brauns compared the calculated profile curve with an empirically determined profile curve. He found that the movement with the calculated profile curve has a more regular rate than the empirically determined profile curve.

In addition to comparing the mathematical formula and the empirically determined profile curve, Kai Schmidt-Brauns tested the escapements with different materials. The choice fell on the tribofilament® iglidur® i150. With a bed temperature of 40 °C, a printing speed of 30 mm/s at a layer height of 0.1 mm and an extruder temperature of 250 °C, the student achieved the best results with the filament from igus®. In comparison to conventional PLA, he was also able to determine a significantly more regular movement of the escapement during a test run. In addition to the results in the escapement, the tribologically optimised filament was able to provide an improvement with its wear resistance in heavily loaded components. The pawl ring of the ratchet (see picture), which is located in the winding mechanism of the clockwork, had to be replaced significantly more often with conventional PLA than with iglidur® i150. In addition, he was able to record a higher toughness and flexibility compared to that made of conventional PLA through tests with a spiral spring printed from iglidur® i150.

In addition to iglidur® i150, igus® offers many other tribologically optimised filaments for 3D printing. They all have in common that they are intended for sliding applications due to their high abrasion resistance. iglidur® i150 can be processed very easily like PLA and PETG filaments. In the wear test from the igus® test laboratory, the igus® tribofilaments perform up to 50 times better than conventional plastics such as PLA and ABS (see image). It is also food compliant in accordance with EU Regulation 10/2011 and therefore suitable for corresponding applications in the food and packaging industry. The all-rounder filament is particularly suitable for printing beginners thanks to its ease of processing. The 3D printing service is also available at any time with a delivery time of 1-3 days if the help of experts is required.