3D knitting as an additive manufacturing process for the textile industry

Within the AiF research project Addknit, the DITF have created a process model for the development of individualized knitted fabrics. This covers all steps from the definition of requirements to the knitted product using the Addknit knitting algorithm.

The requirements profile includes all the properties necessary to characterize the finished product. For implementation, a division is made into physical properties of the surface and properties of the 3D model (geometry). The surface properties are taken into account by selecting the material mix and weave. The mesh size depends on the material and weave and is determined in the process model by material tests.

A Matlab algorithm was developed in the project to convert the 3D model (scanned or CAD-generated) into a knitted jacquard, for which the stitch size is the key parameter. These 3D models must be reduced to the surface to be knitted and adjusted if necessary. Parameters such as elongation, thickness and strength are taken into account via the 3D model. In the Addknit software, the 3D model of the body to be knitted is loaded in the graphical user interface and the boundary conditions are set.

The knitting algorithm generates a knitting jacquard, which can be converted into knitting programs using software interpreters from various machine manufacturers. For this purpose, a symbol or color is defined once for each knitting operation in the knitting algorithm.

The knitting program is loaded onto the flat knitting machine and knitted with the appropriate yarn configuration. The knitted product is finished according to the specifications in the requirement profile and checked for systematic errors such as holes or stitch accumulations. The accuracy of fit of the product to the original 3D model is also checked. Optical processes such as comparative 3D scans can be used for this purpose.

The results of the project will be presented at the “Innovationstag Mittelstand“ of the Federal Ministry of Economics and Climate Action (BMWK) on June 13 in Berlin.