Tension Control
The slight, controlled force applied to a yarn as it is wound onto a wrap reel prevents sagging and ensures that every turn is wrapped at a uniform length. This wrap reel pretension is necessary to obtain an accurate yarn count measurement, as loose wrapping produces shorter skeins and artificially high count results. It is standardized according to the linear density of the yarn being tested, ensuring that the yarn is straightened without being elastically deformed or stretched during the winding process.
Mechanism of Action
Tension is applied via disk tensioners, spring-loaded plates, or weighted guides that the yarn passes through before reaching the reel. Applying too much wrap reel pretension stretches the yarn, which results in a lighter apparent yarn count. This tension must be calibrated using a gram-force meter at the start of each testing shift.
Standard Reference
International standards define the specific tension levels in centinewtons per tex that must be applied for different yarn types. Following the wrap reel pretension requirements guarantees that laboratories in different countries obtain comparable yarn count data. This eliminates discrepancies in global trade transactions.
Process Consistency
Operators verify that yarn packages unwind smoothly to avoid sudden spikes in winding tension. Consistent wrap reel pretension is essential for producing uniform skeins for subsequent lea strength testing. This prevents errors in count-strength product calculations.
