Question

The periodic mass variations in yarn are mainly caused by \(\underline{\hspace{2cm}}\)

• A. Machine faults
• B. Machine setting
• C. Random fiber arrangement
• D. Personal error

Hint:

When analyzing yarn evenness: - Random Faults = Natural, unavoidable variation. - Periodic Faults = Mechanical problem (e.g., bad roller, broken gear). Look for a repeating pattern. The spectrogram is the tool used to diagnose these periodic faults.

Answer 1

The Correct Option is A

Step 1: Understand "periodic mass variations." Yarn evenness testing (using a spectrogram) can reveal different types of mass variations. 

- Random variations: These are inherent to the process of forming a yarn from staple fibers and do not have a repeating pattern. 

- Periodic variations: These are faults that repeat at regular intervals along the yarn length. They show up as distinct peaks on a spectrogram. 
 

Step 2: Analyze the causes of periodic faults. A repeating, regular pattern is a tell-tale sign of a mechanical issue. Such faults are caused by a defective or improperly functioning rotating part in the spinning machinery, such as an eccentric (off-center) roller, a broken gear tooth, or a vibrating component. Each revolution of the faulty part creates a thick or thin spot in the yarn, leading to a fault whose wavelength corresponds to the circumference of that part.

Step 3: Evaluate the other options. 
- (B) Machine setting: An incorrect setting might produce a generally poor yarn, but not typically a periodic fault unless it causes a part to vibrate. 
- (C) Random fiber arrangement: This is the cause of random variations, not periodic ones. 
- (D) Personal error: This is unlikely to cause a fault that repeats with machinelike regularity. 

Conclusion: Periodic mass variations are almost always caused by mechanical machine faults.