When three ball screws manage docking on the ISS in orbit

When it is dusk and the sky is dark, the ISS is lit by the sun, you can see it from earth. The International Space Station shines like a bright star. It is bigger than a football field yet flies at an altitude of 400 kilometres with such speed that it defies gravity. Eichenberger, the Swiss thread specialist yet again proven that it can provide a solution for any customer request or performance requirements: three ballscrews master the docking on the ISS in orbit.

No matter how specific requirements are

Designers are regularly faced with the challenge of finding the right drive technology to implement linear movements. Often, high positioning accuracies and oscillating movements from high frequencies must be accomplished when trying to achieve the smallest lifts or high dynamics in constant use. We focus on safety and reliability. Restricted assembly space with heavy loads is a frequent challenge. Maintenance time, service life and, of course, cost also play an important role. The requirements on mechanical drive elements and the demands in the relevant areas of use increase similarly. Ballscrews are one of the most commonly used drive systems in many industries with the advantages of highly efficient performance and energy efficiency.
The Eichenberger screw technology, thread rolling (cold-forming of the surface of round components), combines the highest carrying capacity and power density, extreme dynamics and precision with maximum performance.

 

«The most important thing in a conversation is hearing what has not been said.» - Peter F. Drucker

 

For Eichenberger, the focus is always on the customer: Actively listening and asking, advising, designing, building, testing, optimising, producing. Only through targeted exchange of information and ideas, can needs be fully understood and implemented. In this way the thread expert uses its strenghts to adapt products and the value-added chain in response to constantly increasing international change. A vital part of the company culture of the thread specialist is to be pro-active instead of reactive. Its tailor-made ballscrews are used everywhere, from medical equipment, electrical, automotive and automation engineering to aviation and even space travel.

 

«The same path leads to core competencies in every field: Persistent cracking of special nuts.»
- Karl Heinz Karius

 

Experience with various customer tasks over almost seven decades have turned the thread roller from Burg (CH) into an experienced and sought-after specialist. Eichenberger manufactures items very efficiently and speedily. Prototypes, including thread rolling tools, if required, can be manufactured quickly. This is only possible because the development, production, quality management and sales departments work perfectly together in-house. Thanks to this, we are able to manufacture products flexibly and competitively. Today, the most unusual customer solutions are developed upon request. Using our cost-effective cold-rolling procedure, the impossible is achieved.

 

Space rendevous
Eichenberger thread drives make it possible

The goal of creativity is to produce success stories. Not infrequently solutions for exotic special applications begin with inspiring discussions. In 2015, a project was launched in Burg with the leading global supplier of products to the aerospace industry. The goal set for collaboration is executing docking manoeuvres during a space rendezvous between the ISS and the innovative, re-useable space glider from 2020 onwards. The docking unit, which is “300% safe” and functional, is the integral part. The centre piece inside this docking system consists of three robust, corrosion-resistant Carry ballscrews with end cap ball return, type KGE, 16 x 16. Reliability is the highest priority for the space shuttle service. Its robustness and resilience in the harsh, unfavourable orbit environment plays an essential part. Meticulous accuracy is also vital.

 

Gewinde RaumgleiterSource: Sierra Nevada Space Systems

Shuttle service into space

The new space shuttle will blast off inside the nose of the Atlas V launch vehicle to go into near-earth orbit. It can fly with or without a crew and land at any conventional airport. There is room for up to seven astronauts in the space glider. For example, it could be used as a research platform, to transport people or freight into space or to actively remove space junk from orbit. Using the docking unit in which Eichenberger CARRY ballscrew guarantees a precise, safe docking procedure, the space glider will be able to dock on the occupied station ISS in orbit. At a speed of 28,800 kilometres per hour, the flying laboratory takes only 92 minutes in zero gravity to circumnavigate the earth. Astronauts living and working in the station therefore experience 16 sun rises and sun sets every day.

The challenge of aerospace – extreme conditions

The first major hurdle following the strenuous rocket launch with extreme acceleration and vibrations, is the vacuum. It has an effect on everything that is liquid or that can evaporate, including lubricants. Grease that is solid on earth, evaporates in a vacuum. That is why mobile parts must be able to comply with maximum service life requirements, even without lubrication. Temperature extremes are also challenging. The temperature of the components in orbit depends on the material that faces the sun. A range from 50°C to + 90°C is expected on the docking station. Additionally, ultra-violet light, X-rays, particles with a high energy charge and atmospheric atoms have an impact on the material which becomes more prone to corrosion. Eichenberger is proving that the extraordinary characteristics of the Inox CARRY ballscrew, with integrated high-performance plastic in the ball return, will withstand the aggressive environment of space, ensuring function as well as resisting corrosion and wear.

A close look at competency

What makes the Carry ballscrew so resilient and the ideal functional element for this application?

The cold-rolling of threads creates very precise geometries with high surface quality. In contrast to grinding, milling or turning, the longitudinal fibres of the material are not cut but deflected during the thread rolling process. The result is a compressed and extremely resilient surface which has been rolled smooth. This is essential for the long service life of a screw. Roughness values of around Rz 1.0 on the edges of the thread is also a significant advantage. In steel ball bearings, the rolling friction co-efficient is about 0.0013 compared with sliding friction of steel on steel (lubricated) of 0.1 to 0.05. The excellent sliding properties of cold-rolled ballscrews ensure minimal friction and provide little scope for contamination. The quiet rolling of the balls is therefore easily achieved.

The demanding specifications for surface hardness and corrosion resistance of the stainless steel could be met thanks to the innovative Hard-Inox® P treatment. During this process, the performance of the lateral structure of corrosion-resistant steel is significantly increased, by high-temperature nitriding. (Surface hardness reaches 550 to 750 HV with a hardness penetration depth of 0.1 to 1.0 mm.) The great benefit lies in the increase in service life and value retention. The art is to master distortion and changes in dimensions despite the high-temperature treatment. The perfect combination of hardness and precision has to be achieved.

The perfect partner from single-unit production to series production

The wheel of mechanics cannot be reinvented. Yet, Eichenberger claims to constantly testing the limits of cold-rolled ballscrews. Competency goes beyond knowledge. Or to put it another way: competency is the skill of solving problems. Each screw that is developed from scratch is included in the thread rolling range. Over the decades, this has generated a wide selection of ballscrews and lead screws.

Designers always try to start with a standard nut or screw, then adapt these elements to the application-specific requirements. This has a significant price advantage. The challenge for designers in high-cost Switzerland is to create outstanding added technological value in a competitive product in line with the market. Technological know-how, research and development are just as necessary as a willingness to change and mastery of efficient production procedures.

Gewinde RaumgleiterBallscrew Carry type KGE 16x16 MSX – The perfect interaction of balls, screws and nuts

Service provider for development

The need for practical solutions is perpetual. Eichenberger Gewinde AG successfully implements the opportunities this brings and has thus managed to establish itself in the drive technology niche with tailor-made rolled thread drives. The Swiss thread specialist has clear objectives: To roll (cold forming) threads and manufacture thread drives (screw and nut). Using state-of-the-art production methods and developing new dimensions, Eichenberger is able to support customer innovations. 

  • «Carry»: Wear-free ballscrew for applications where heavy loads must be moved with low energy consumption. Depending on the version, particularly high operating speeds are possible.
  • «Speedy»: The high-helix lead screw converts linear motion into rotational motion with high moving speeds.
    New: Some versions available in aluminium.
  • «Rondo»: The round thread lead screw with very quiet running properties.
    New: Some versions available in aluminium.
  • «Easy»: The hard-anodised light lead screw made of aluminium with an efficiency of more than 0.8, for higher loads than for normal lead screws. The special profile prevents jamming in the nut.
avatar

Ursula Schädeli

Marketing, Eichenberger Gewinde AG

Eichenberger Newsletter – information in motion

What’s moving in the world of drive technology? We keep you up to date with new ideas, developments and concrete solutions for the increasing challenges for perfect motion.

REGISTER