Yarn Crimp Tester: Complete Guide to Testing Crimp in Textile Fabrics


 

A yarn crimp tester is a special testing instrument in the textile industry that tells you the ‘crimp’ percentage or crimp ratio of yarns. Crimp here can be defined as the waviness that yarns have because of interlacing during the weaving process.

The crimp tester relies on the individual warp extracted and placed into the tester grip, where the yarn is pulled to straighten the yarn, and the length is measured. It has many functions and supports fabric design, yarn consumption estimations, and quality control in textiles.

What Is Yarn Crimp?

A yarn crimp is the waviness of the woven yarn. This is because when warp and weft yarns interlace during weaving, they don’t weave in straight lines, but each yarn bends over and under the crossing yarns, which introduces the wavy corrugated path of weaving. The waviness in the yarn is called crimp.
A more technical definition of yarn crimp is the percentage excess of the yarn axis length over the cloth length. You can imagine the length of the fabric and then the length of the yarn, which has to be larger than the fabric’s length because of the waviness.
Don’t confuse crimp as a defect; it is a property that controls fabric performance and yarn consumption in factories.
Crimp in Warp vs. Weft Yarn: Key Differences
​In a woven fabric, warp yarns run lengthwise and are continuously stretched or under tension on the loom. These warp yarns are more uniform and stronger because they have to resist the abrasion during the weaving process.
Weft yarns are also called filling yarns, and by contrast are inserted under no tension and often use specialty yarns because they must bend over and under every warp yarn across the width of the fabric. Weft yarns have more crimp.

How a Crimp Tester Works: Step-by-Step

A yarn crimp tester extracts a yarn from a fabric of known length, straightens it under tension, and measures the straightened length to compute the final crimp percentage.
  1. Select the test direction (choose warp or weft) and cut a fabric strip of known length. The standard is to use at least 5 threads per direction, and 10 provides a greater confidence in the final result.
  2. Use a dissecting needle to separate the central portion of the thread from the fabric fringe. Be careful not to remove the twist.
  3. Transfer the thread to the crimp tester: Place one end in the fixed grip and the other in the movable grip. The yarn should be placed as carefully as possible without altering the twist in the yarn.
  4. Enter the tension value based on the yarn count and type. Machines like the FYI Crimp tester provide a user-friendly interface and standardized tension tables. Apply the tension gradually until the yarn is straight but not stretched or elongated beyond the elastic limit.
  5. Check the straightened length using a scale or digital Crimp tester and calculate the crimp % using the crimp formula above.
  6. You can repeat this process for all test threads and average the readings.

Types of Yarn Crimp Testers in Textile Laboratories

Manual Crimp Tester
The manual crimp tester is the most common and standard in many places. It is almost always present in yarn labs, and researchers still rely on it for readings. It uses a fixed grip, a movable grip, a beam with a sliding weight, and a graduated scale. In a manual crimp tester, you adjust the sliding weight position to apply tension. It has many possibilities of human error, but it is suitable for most woven fabrics.
Digital Yarn Crimp Tester
Digital yarn crimp tester completely automates the tension application and length measurement process. There is little operator variability, and most of the process is automated. The digital readout removes parallax errors from manual scale reading. Some features of the digital yarn crimp tester include a touch screen display, adjustable stretching speed, automatic positioning, and a high-precision tension sensor for accurate standardized research testing.
Fiber Crimp Tester
Fiber crimp testers are specifically designed for single fibers. These are different from yarns extracted from fibers. It has a force sensor to measure fiber lengths under light and heavy loads, calculates crimp ratio, and uses images to analyze the count of crimp waves in a standard 25 mm fiber segment.
Fiber crimp tester is particularly for research institutions and chemical fiber production industries.

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