Question

In Yarn Evenness testing the variance length curve is more suitable for

• A. Periodic faults
• B. Non-periodic mass variation
• C. Imperfections
• D. Variation in the count

Hint:

The variance-length curve is particularly useful for identifying periodic faults in yarn, which appear as peaks at specific lengths on the curve.

Answer 1

The Correct Option is A

Step 1: Understanding Yarn Evenness Testing: Yarn evenness testing assesses the variation in yarn linear density (mass per unit length) along its length. Unevenness can be caused by various factors during spinning.
Step 2: Variance-Length Curve (V-L Curve): The variance-length curve (also called the spectrogram in some testing instruments) is a graphical representation of yarn unevenness. It plots the variance of the yarn mass (or a related parameter) against different lengths of yarn. The X axis of the curve represents different lengths, and y axis shows variation.
Step 3: Identifying Periodic Faults: Periodic faults are variations in yarn mass that repeat at regular intervals. These faults are often caused by mechanical issues in the spinning machinery (e.g., a damaged roller, eccentric gear). On a variance-length curve, periodic faults appear as distinct peaks at specific lengths corresponding to the period of the fault.
Step 4: Other Options: Non-periodic mass variation: This would show up as a general increase in variance across all lengths, not as distinct peaks. Imperfections: This is a general term. The variance length curve can help detect them, especially when they have some periodicity. Variation in the count: This is what evenness testing is about, but is not specific to the variance-length curve.