Analysis of Warp Yarn Tension on a Multiaxial Warp Knitting Machine : Model for a warp yarn tension control on a Copcentra MAX 3 CNC with multiaxial glass roving weft insertion

An operator of a warp knitting machine with multiaxial weft insertion is demanded to adjust the parameters to each non-crimp fabric NCF. Besides specifying parameters as definition of textile appearance (pattern type and stitch length) undefined ones exist, especially the warp let-off. It initiates different warp yarn tensions in sub-minute range and plays a significant role in adjustment. The aim of this work was to analyse the warp yarn tension on a Copcentra MAX 3 CNC via online measurements. For this purpose a mathematical correlation of the machine settings with the yarn tensions has been developed, which comprised an algorithm for the required loop length within the NCF. A future opportunity is provided to substitute the subjective warp let-off adjustment by a model of tension control. The analysis revealed that the warp yarn tension is affected clearly by the interaction of pattern types, stitch lengths and warp let-off extremes. It showed that yarn tension boundaries have not been exhausted. The model of a control based on the correlation between yarn tension and loop length establishes the groundwork for replicable yarn tension and compliance with NCF quality requirements.