Robotic arm and tufting
Tufting represents a very novel approach to localized through the-thickness (TTT) reinforcement in composite structures for the dry preform/liquid resin injection manufacturing route. It is intended to combat the problem of delamination by modifying the fibre/resin architecture. The dry preform is processed by means of a newly commissioned tufting head (KSL KL150), interfaced to a 6 joints computer controlled robot arm (Kawasaki). A single needle takes a yarn through the fabric layers and returns back along the same trajectory, leaving a loop of the yarn on the back side of the plies. It is different to machine stitching in that the tufting stitch is never ‘locked’ and only remains in position because of frictional forces acting on it. This leads to a virtually tension‑free structure and, in turn, to less waviness in the fabric and fewer problems during subsequent resin injection.
Tufting can also join semi-finished parts together, making the laid up material easier to handle. It is a one-side access technique and then not only requires less tooling in comparison to standard stitching, but also makes possible:
- Tufting on the mould
- Processing complex and 3D shaped pre-forms
- Processing unlimited thickness by subsequent lay ups
- Choosing needle penetration angle
The robot assisted tufting represents an ideal approach for localized reinforcement because of the possibility of rapid processing of complex three dimensional shapes. Automation implies high reproducibility, in less time, with virtually no manual handling of the fabric before resin injection.
Essentially tufting is equivalent to Z-pinning, but used to reinforce dry fabrics prior to resin injection using Liquid Composite Moulding techniques.