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7th December 2017, Salzbergen

Robotic control at SGL-Kümpers

At two plants in Lathen and Rheine North in Germany, 120-year-old family-owned company Kümpers is currently producing around 14,000 square metres of glass fibre non-crimp fabrics (NCFs), 1,400 square metres of carbon NCFs, 120,000 square metres of braided fabrics and 1,000 square metres of wovens.

Its NCFs are already supplied for parts for the Audi A8, as well as the BMW i3 and i8 electric vehicles and it is also involved in a joint venture with SGL Group – the leading manufacturer of carbon fibres, composites and prepregs – for the annual supply of over 100,000 carbon fibre preforms to BMW annually.

The company operates two plants in Lathen and Rheine North in Germany. © SGL-Kümpers

The roof frame of the latest BMW7 includes a number of carbon fibre composite parts in combination with others made from aluminium, and SGL-Kümpers is supplying the side roof frame preform.

At three metres in length, the multilayer preform incorporates varying braid angles in its structure.

In establishing the process for its series production, common expectations from the automotive industry – comparable to those set for steel parts – had to be achieved.

They included overall efficiency of the automated system of above 75%, delivery quality of less than 300-500 ppm (defects per million pieces) a scrap rate of less than 5% and a narrowing of the initial gap between the cost of the carbon part and an alternative of steel.

In terms of process development, SGL-Kümpers had to first establish the multi-layer preform handling and a new continuous braid process for maintaining the braid cycle. The braiding machines involved had to be specially adapted for the process and ancillary processes such as trimming and labelling also established.

Multimove robot steering was also introduced, not without some initial difficulties.

The company produces 120,000 square metres of braided fabrics. © SGL-Kümpers

“Textile materials cannot be handled robotically like metal parts and initially this proved a real challenge,” explained Franz-Jürgen Kümpers, managing director of SGL-Kümpers at the 2017 International Composites Congress (ICC) held in Stuttgart. “The handling of materials with high bending strength called for a new approach and final trimming was a very large challenge.”

Quality assurance

Other challenges in rapidly establishing the programme were in the areas of quality assurance and process traceability.

Around 1,000 individual values need to be tested for machine capability, with inline testing for critical properties such as the braid angle and weight.

In order to ensure traceability, some 500,000 data sets are being generated each week, with the tracking of raw material batch data, process parameters and part data carried out by an individual production data acquisition system.

Following par finalisation, the data is automatically transmitted to BMW.

“The system means every part can be traced back to every individual carbon fibre spool it was made from and the data will be stored for up to 20 years,” Kümpers said.

The preform fabrication process that was established has a total of 30 robots working at six braiding machines, with four synchronised to work at each machine at any one time.

“No manual tests are necessary within the braid cycle as the robots pull the preform through the machine and we have achieved better-than-planned efficiency,” Kümpers said.

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