Technische Universität München invents thumb support that reduces strain on the joints

In automotive manufacturing the thumb is exposed to more strain than any other finger. Day in, day out it must bear great loads – literally. Christin Hölzel, a doctoral candidate at the Chair of Ergonomics of the Technische Universität München (TUM) had an idea: A support for the thumb that reduces strain on the joints. Assembly line workers at the BMW Group’s Munich plant gave their “thumbs up” for this invention, which is being deployed there in a pilot project.

MUNICH, 25-7-2014 — /EuropaWire/ — Thumbs do four times the work of the other fingers during manual production. A good example is automotive assembly. Here, plug seals made of rubber are pressed into the floor pan with great force. They are used, among other things, to close drain holes for chassis paint.

Pressing in the plugs can lead to an over extension of the thumb joint. Prof. Veit Senner at the Department of Sports Equipment and Sports Materials at the Chair of Ergonomics explains: “Imagine the way a thumbnail is pressed into a wall with great force. The thumb bends in a backwards arch and the joints are overextended.” Of course, pressing in a single thumbnail is no cause for concern – but the workers at the BMW Group production line in Munich repeat this motion hundreds of times. “Over time, this can harm the joint,” says Senner.

Exoskeleton protects thumb joint

In the context of her dissertation at the Chair of Ergonomics, Christin Hölzel is working at the BMW Group to investigate the question of how to reduce the strain induced by these kinds of work processes. She has developed a flexible, synthetic exoskeleton for the thumb to prevent overextension of the thumb joint.

The aid may not obstruct other work processes if it is to be accepted by the workers. The assembly aid is thus open at the thumb joints, allowing the thumb to move freely. On the inside, by contrast, the synthetic material is built up in a thick layer. When the thumb is extended, reinforced elements make contact with each other and act a strong splint. The force applied to press in the plug is thus distributed along the entire thumb, all the way to the carpus.

Custom-tailored assembly aids out of a 3D printer

Since no thumb is like another, the so-called orthoses are individually adapted. The anatomy of the hand is scanned and the assembly aid then printed on a 3D printer. Assembly workers at the BMW Group plant in Munich have already tested the orthoses – the feedback was positive.

In the near future, Hölzel will use a computer model and simulation to determine the degree to which the assembly aid reduces the load on the thumb joint. The engineer also wants to investigate if the aid does not induce additional strain on other joints.

High resolution images


Prof. Veit Senner
Technische Universität München
Fachgebiet Sportgeräte und -materialien
Tel. +49 (89) 289 – 15364

Saskia Eßbauer
BMW Group
Tel.: +49 89 382 18364


Thumbling from a 3D printer protect joints. (Photo: BMW Group)

Thumbling from a 3D printer protect joints. (Photo: BMW Group)


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