During winding, twisting, knitting, or weaving, yarns are stressed over their full length with tensile forces that may exceed their breaking strength in a few places. These weak spots lead to yarn breaks. which result in downtime in the production process and may cause faults in the final product. They are caused for instance by very thin places in the yarn, sections with improper twist take-up, or segments with inclusions of foreign matter. The increasing
use of recycled fibre material makes the control of weak spots even more important.

Usually, the average breaking strength of a yarn shall be significantly higher than the tensile forces in the downstream manufacturing processes. Even though this safety margin isused, staple fibre yarns inevitably contain weak spots, where the safety margin is exceeded.

DYNATENS dynamically tests staple fibre yarns to detect and characterize weak spots.

The instrument continuously subjects the tested yarn with an increasing amount of stretch resulting in up to 12 yarn breaks per second at yarn feeding speeds of up to 800 m/min. Additionally, almost the full length of the yarn (> 90 %) which is passed into the instrument is checked. In this way, the chance of overlooking a weak spot is minimized which corresponds to highest testing efficiency.
Simultaneously, DYNATENS also measures the average breaking strength and the average elongation at break reliably.

In DYNATENS, two co-moving godets achieve very high testing rates and maximum efficiency. Both godets rotate in the same direction. The second godet runs faster than the first one, causing the yarn to stretch and eventually break.

After each yarn break, the yarn threads itself through the second godet. It does not need any additional moving parts or yarn reservoir inside the tester. Additionally, the DYNATENS also only requires a minimum level of maintenance resulting in low total cost of ownership.