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Customized assembly support from the 3D printer

News International-French

1 Jul 2014

Ergonomic production – Pilot project at the Munich plant evaluates application of individual orthotic devices in vehicle assembly

The BMW Group considers people the key to a lean production that focuses on the customer benefit. This is why the company interprets ‘Industry 4.0’ as a way to make reasonable use of technologies in order to provide the best-possible support to the workers in production and in support areas. How this can be achieved is demonstrated by a pilot project in Plant Munich’s vehicle assembly. Only recently, a new and innovative ergonomic tool has been introduced: a flexible finger cot, which protects workers against excess strains on the thumb joints while carrying out certain assembly activities. The project is part of a dissertation in cooperation with the Department of Ergonomics at the Technical University of Munich, which is a way for the BMW Group to address and meet the specific demands of an ergonomic production. Each of the flexible assembly aids is a unique piece, customized to the match the form and size of a worker’s hand. The BMW Group makes these orthotic devices in-house, using additive production procedures that are currently the talk of the town, namely ‘3D printing’.

The innovative orthotic devices are applied as part of a pilot project in an assembly area where rubber plugs are fitted. These have to be pressed in with the thumb and close, among other things, the drain holes for the paint coat. Even for people with strong hand muscles, this movement requires a certain effort. In order to prevent the unnecessary overstretching of the thumb joint, the finger cots made of thermoplastic polyurethane are put over the thumb like a second skin. Right at the thumb joints, the assembly aid is open to allow the thumb to move without restriction. At the back of the thumb, though, the plastic material is reinforced. If the thumb is stretched, as in a ‘like it’ gesture, the reinforced elements collide, forming a stable splint. This way, the effort needed to press in the plug is spread across the entire thumb, down to the carpus. In initial practical tests, the feedback of workers was very positive. It is currently being evaluated how the assembly aids can be applied as standard tools in further production areas.

Each of these finger cots is made specifically for its user. To this end, the worker’s thumb is measured with a mobile 3D hand scanner. Based on a standard production layout, the future orthotic devise is then computed and divided virtually into individual layers. Layer by layer, each of them about as thick as a human hair, the tool is then manufactured in a selective laser sintering process. Put simply, the way this additive production procedure works is similar to a 3D printer: A digital data set is cut into individual layers of information. Based on the layer data, a plastic powder is selectively fused by a CO2 laser in a pre-heated construction chamber. This way, the plastic does not only mold into the layer presently created, but also merges with the previously formed one.

Thermoplastic polyurethane, the material used, is perfectly suited to making flexible orthotic devices. As a rule, it is elastic, but forms solid and rigid combinations at higher material strengths. The mechanical tensile strength is high, ensuring that the material can resist also strong, continuous strains without tearing. The BMW Group has been involved in research projects that have recently resulted in the market maturity of the highly innovative material, following several years of development. A major benefit: The mechanical component properties can be ‘customized’ for the respective application via a combination of different process parameters.

Photo: BMW Group’s Munich plant: Customized assembly support from the 3D printer