Application
The Yarn Twist Tester is designed to measure the twist of single or plied yarns. It features a quadrant type with automatic stop and reverse functions, suitable for both conventional twist and untwist/re-twist methods. The tester offers an adjustable test length up to 500 mm (20 inches) for both S and Z twist yarns. The inching function allows operators to quickly identify the desired twist. Test results, displayed in TPI (Twists Per Inch) or TPM (Twists Per Meter), are directly shown on the touch screen for easy analysis.
Testing Method
Importance of Twist in Yarn
The twist of yarn plays a crucial role in determining yarn strength, color accuracy after dyeing, and the fluffiness of cheese yarn. A higher twist rate is recommended for rewinding to extend the time for dyeing the yarn, resulting in a higher average dyeing speed. During hank dyeing, higher twist leads to greater shrinkage under hot and humid conditions, increasing the yarn’s linear density.
Yarn Twist Definition
Yarn twist refers to the degree of tightness applied to the fiber and is typically measured by the number of twists (one twist equals 360° of fiber rotation) per unit length. For staple yarns, the standard unit length is 10 cm, with a ratio of 1 m. The greater the number of twists, the tighter the fibers, resulting in a firmer yarn structure.
Yarn Twist Test Method
- Apparatus and Materials:
- VIT 370 Yarn Twist Tester
- Types of yarns to be tested
- Preparation for Specimen:
- Expose the specimen to a standard atmosphere (Grade 2 standard for non-arbitration experiments) for at least 16 hours.
- Use 1 longitudinal spline and 5 latitudinal splines. The specimen length should be 70–80 mm longer than the experimental length, with an appropriate width based on the number of yarns tested.
- Testing Procedure:
- Unweave the yarn by approximately 100 mm and observe the twist pattern (S or Z twist).
- Unweave the yarn from one end, maintaining proper tension.
- Rotate the twisting grip to untwist the yarn until all fibers are parallel or the yarns are separated.
- Record the number of untwisting rotations.
- Repeat the process for the desired number of yarns.
- For filament or staple yarns, calculate the stretching tension according to the yarn’s linear density and adjust as necessary.
- Calculation:
- Calculate the average twist values for both longitudinal and latitudinal directions, rounding to the nearest whole number.
