Fast and economical manufacture of complex special parts

• What was needed: Special gliders with complex geometries
• Manufacturing process: Laser sintering
• Requirements: Sliding-optimised, self-lubricating, durable
• Material: iglidur® i3
• Industry: Automotive
• Success through co-operation: cost-effective, fast production of small series. Durable components with dry operation.

Drivers who cannot use their legs can accelerate with their hands on the steering wheel thanks to the Darios digital throttle ring. Developed by Kempf in Alsace, the elegantly unobtrusive throttle ring offers comfort and safety when driving and can be integrated into most automatic vehicles. To adapt the throttle ring to flattened steering wheels, the engineers were faced with the challenge of allowing the ring to slide around the corner. In 2019, the company received the manus® award for innovative problem solutions with plastic bearings for its solution - the special sliders made from the slide-optimised 3D printing plastic iglidur® i3.

With the self-lubricating SLS-plastic iglidur® i3, the 3D printing service from igus® can produce complex special parts within 24 hours. The components printed from the iglidur® sliding polymers are characterised by their high wear resistance and predictable service life.

"For the production of throttle rings for flattened steering wheels, the company regularly requires special glides that are movably connected to each other and slide around the corner" via a metal ring. More than 200 elements are required per steering wheel. The only way to realise this movement is to construct special sliders with complex geometry. These sliders contain numerous undercuts, which makes production using conventional manufacturing processes not only difficult but also very cost-intensive. As Kempf's driving aids come with a 30-year guarantee, the special gliders have to be extremely durable and reliable. It is not possible to lubricate the components as they are permanently installed inside the leather cover of the gas ring.

The complex structures and undercuts of the special gliders can only be produced efficiently using additive manufacturing. With the slide-optimised high-performance plastic iglidur® i3, Kempf found the ideal material for printing the filigree elements. The special gliders, which are produced within 24 hours using the laser sintering process, run smoothly around the corner without lubrication or maintenance. Despite the high quantity of more than 10,000 pieces per order, the production of the special gliders using 3D printing even proved to be cheaper than injection moulding due to the high level of complexity.

"The gas ring is the best product on the market in terms of quality. The workmanship is unrivalled and its reliability unbroken. I have driven a total of 785,000 kilometres so far without any technical problems. Yes, it's 785,000 kilometres and 19.625 circumnavigations of the earth."

This is just one of the many enthusiastic testimonials from Darios users. No wonder, after all, Kempf is committed to the highest quality and offers its customers a 30-year guarantee on all driving aids.

KEMPF was founded in 1955 by Hans Kempf, who was disabled after suffering from polio. As a keen mechanic, he invented the throttle ring so that he could drive with both hands on the steering wheel. By the end of his life in 2002, he had converted over 100,000 vehicles.

The hand throttle system developed by Kempf is the only one available on the market that adapts to the speed of the vehicle: At slow speeds, acceleration is smooth, progressive and economical; at high speeds, acceleration is dynamic to ensure safe driving and fast overtaking manoeuvres are precise and easy. All the usual functions of the steering wheel, such as adjustability, airbag and horn, are retained. The pedals also remain functional - Darios can be switched off using a switch so that other drivers can operate the vehicle in the usual way.

To accelerate, the ring is pushed in the direction of the steering wheel. This only requires a very small amount of force (approx. 3 Newtons). The stroke between idling and full throttle is only approx. 18 mm. When the steering wheel slides back into the straight-ahead position after a bend, the freely rotating cover enables precise acceleration at the exit of the bend, regardless of the steering wheel position. Both hands can remain on the steering wheel when operating Darios, whereby the throttle ring can also be operated with just one hand, for example to operate the right-hand parking brake with the other.

Covered in fine leather, the throttle ring blends harmoniously into the interior of the vehicle, and drivers can even choose the colour of the leather if they wish. As many cars now have flattened steering wheels, Darios 211 was developed. This gas ring is flattened, but also has a freely rotating cover. But how do you provide a flattened ring with a sliding cover?

The new trend of equipping vehicles with flattened instead of round steering wheels presented the engineers at Kempf with a major challenge. For both technical and aesthetic reasons, a flattened steering wheel requires an equally flattened throttle ring. The inconspicuous throttle ring, which is integrated into the vehicle as a matter of course, actually contains a number of elaborate details. Equipping a round throttle ring with a sliding cover is comparatively simple. Providing a flattened throttle ring with a cover that rotates just as freely as a round one required a technically sophisticated solution.

The product developers at Kempf found this solution in co-operation with the 3D printing team at igus®. The new Darios 211, the world's first flattened gas ring, uses additively manufactured components made from the slip-optimised plastic iglidur® i3. The flattened gas ring has more than two hundred of these flexibly connected elements. They form a sliding ring around the flattened metal core of the gas ring, allowing the casing to slide seamlessly. Kempf was presented with the bronze manus® award at Hannover Messe 2019 for this particularly innovative solution.

The engineers decided to manufacture the complex special gliders using 3D printing, as injection moulding was very complicated and therefore expensive due to the numerous undercuts. Additive manufacturing places hardly any restrictions on design rules, which makes the production of components with complex geometries particularly economical. This also eliminates mould costs.

One of the most important reasons for selecting iglidur® i3 as the material for manufacturing the special gliders was the solid lubricants it contains. This eliminates the need to maintain the components and significantly increases their service life, as there is hardly any wear. iglidur® i3 is an SLS powder that can be processed on all conventional laser sintering machines. The powder is melted layer by layer with a laser, which enables the precise diagram of fine structures. Depending on the size of the component, several thousand pieces can be produced in a printing process that takes around 24 hours. Customers benefit not only from the high cost savings, but also from the unbeatably fast production and delivery time. Another special feature that only laser sintering makes possible in this form is the printing of packaging for the filigree parts in the same printing process. This eliminates costs and effort for packaging and the risk of individual components being lost or damaged.

iglidur® i3 is by far the most frequently used 3D printing plastic in the 3D printing service from igus®. In addition to various sliding applications, it demonstrates its strengths as the best plastic currently available on the market for 3D printed gears.