Yarn Count in Air Jet Spinning: Calculation, Performance, and Fiber Selection
Yarn count is used to indicate the fineness of yarns and to judge if they are suitable for production and fabric needs. Air jet spinning: Knowledge of yarn count helps in accurate calculations, sample evaluation, and optimizing the process. The linear density calculations, spinning performance, fiber selection, and yarn count and strength relationship are covered in this guide.
What Is Yarn Count in Air Jet Spinning?
Yarn count is a measure of the fineness or coarseness of yarn and relates the mass and length of yarn. It allows you to define the sought yarn, compare the yarn production samples and decide if the yarn fulfills the requirements of your desired fabric or textile application in an air jet spinning process.
There are two forms of numbering systems used for yarns: direct and indirect. The higher the value, the coarser and heavier the yarn as more mass will be found in a given length of yarn. Some direct systems are common, such as tex and denier.
The indirect numbering systems tell you how many yards per pound or pounds per 100 yards. The higher the number, the finer the yarn because a mass of yarn will yield more length. English cotton count (Ne), used for cotton/cotton-blend yarns.
| Numbering system | Definition | Interpretation |
| Tex | Grams per 1,000 meters | Higher Tex = coarser yarn |
| Denier | Grams per 9,000 meters | Higher denier = coarser yarn |
| English cotton count (Ne) | Number of 840-yard hanks per pound | Higher Ne = finer yarn |
When comparing yarn specifications, confirm which numbering system is being used. A yarn described as 30 Ne cannot be compared directly with a yarn described as 30 Tex without converting the values.
How to Calculate Yarn Linear Density
Yarn linear density is a measure of the mass of a unit length of yarn. This can be done by measuring a given length of yarn and obtaining a mass under controlled conditions. The number obtained will allow you to check yarn specifications, compare samples produced, and look at variations in yarn fineness. These formulas are used to calculate the yarn count for various types of yarns.
The numbering system used should be appropriate for your test procedure.
Tex:
- Tex = (Mass in grams ÷ Length in meters) × 1,000
Denier:
- Denier(D) = Mass(mg) x 9000/Length(m).
English cotton count (Ne):
The number of threads in a measurement of one inch of fabric.
- Ne = 840 yds in hanks/lb of the mass.
The formulas for Tex and denier need the mass (in grams) and length (in meters). If Ne, first change the length measured in yards into 840-yard hanks and the mass measured in pounds to pounds.
Worked Example: Calculating Tex
Let’s look at an example of how to calculate a Tex.
If you are taking a sample of yarn 1000m long that weighs 2.5 g,
- Tex = (2.5 ÷ 1,000) × 1,000
- Result: 2.5 Tex
That is, the yarn’s linear density is 2.5 grams per 1000 meters. The longer the length measured, the more mass and the coarser the yarn; the more mass the shorter the length measured, the finer the yarn.
Factors That Affect Measurement Accuracy
The proper measurement of yarn counts involves consistent sampling and testing procedures. There are several factors which can affect the outcome:
- Moisture content – Fibres absorb moisture, and the mass of the sample changes. Sample conditioning is always done prior to testing.
- Measurement of length: If wound improperly, with too little or too much tension, or if measured incorrectly, this will lead to inaccurate results.
- Balance accuracy: When measuring fine yarn and low sample mass, use a suitable calibrated balance.
- Sample uniformity: If there are local variations in the mass of the yarn, then measurements will be affected by short samples.
- Test conditions: When comparing results, follow the same conditioning, sampling, and calculation steps.
Follow the relevant yarn test standard for accurate comparisons and record the test conditions.
Effect of Yarn Count on Air Jet Spinning Performance
The magnitude of the yarn count is a factor of the performance of air jet spinning because it influences the volume of fibre introduced into the structure of the yarn and the set of spinning process conditions needed for a stable spinning process. The effect will vary depending on the characteristics of the fibres, the machine setup, nozzle design, and the yarn specifications.
Yarn Count and Spinning Stability
Yarn count can impact on the amount of drafting, fiber control and yarn formation. Process control may be needed to be more stringent with finer yarns since the variability of fibre delivery can make a significant impact on the uniformity and continuity of the yarn. The feed and delivery settings might need to vary with coarser yarns to obtain the structure and production stability desired.
A certain number is not always the number of end breaks that gives the best stability. Test the chosen count under the required operational conditions of the machine manufacturer and check for end breaks, yarn defects, and consistency during production.
Yarn Count, Production Speed, and Efficiency
Yarn count is related to other spinning conditions and delivery speed. Changes in count can impact the amount of yarn produced per unit of time, but factors such as machine speed, downtime and end breaks, as well as production efficiency can also play a part in the final output.
Consider and document production speed, actual production, end breaks, and rejected yarn when testing a new count. This will help you to see if the settings that you’ve chosen will make your machine more efficient or just faster.
Yarn Count and Yarn Quality
There are several factors that affect the quality of yarns, one of which is yarn count. It needs to be assessed in conjunction with fiber properties and processing parameters.
| Performance factor | Influence of yarn count | What to evaluate |
| Spinning stability | Changes the process requirements for yarn formation | End breaks and operating consistency |
| Production efficiency | Interacts with machine settings and production speed | Actual output and downtime |
| Yarn evenness | Can affect the distribution of mass along the yarn | Evenness and mass variation |
| Yarn strength | Influences breaking force through linear density and structure | Breaking force and tenacity |
| Fabric performance | Contributes to yarn mass and the resulting fabric construction | Fabric weight, appearance, and durability |
Note: A yarn that meets its nominal count may still fail to meet requirements for strength, evenness, or fabric performance.
Selecting Suitable Yarn Counts for Different Fibers
Choosing a yarn count involves more than just determining the fibre type. The preparation quality, machine capabilities, end use, fiber length, fineness, strength, and composition of the blend have to be taken into account. The number of appropriate is the number that can be produced consistently and in accordance with the yarn and fabric requirements.
Cotton and Cotton Blends
The length and fineness of fibers can affect the ability to control and incorporate them into the yarn for cotton yarns. The quality of the preparation also has an influence on the processing stability and properties of the yarns produced. The strength of the fibres used also has an impact on processing stability and yarn properties.
Cotton blends call for the evaluation of the properties of each component, not assuming that the blend will have the same properties as pure cotton. Variations in fiber length, surface properties, and mechanical properties can impact the quality of the yarn and its drafting.
Select the number of fibers needed based on the desired characteristics of the fabric and test it in production. Avoid choosing a count for its fiber type.
Polyester and Other Synthetic Fibers
There are a variety of synthetic fibers, each with varying qualities in terms of length, fineness, cross section, surface characteristics, and mechanical properties. These differences will affect their processing properties and the kind of yarns they can give.
Consider the fibre specifications, the combination of fibres, the machine compatibility and the final application before choosing a count for polyester and blended yarns. Verify the proposed fibre preparation and spinning conditions are suitable for the selected fibre.
The characteristics of one polyester staple fiber may not be the same as the other fiber or fiber blend. Try out the real product on the actual production conditions before the finalisation of the specification.
Selecting Yarn Counts for Different Applications
The characteristics of the yarn required by the end use help to determine the yarn requirements. The drape and surface appearance of apparel fabrics might be important, while the durability and repeated use of home textiles might be important. Technical textiles have to be able to perform a function that is appropriate for the application.
| Application | Key yarn-selection considerations |
| Apparel fabrics | Hand feel, drape, appearance, and durability |
| Shirting | Surface uniformity, fabric construction, and comfort |
| Home textiles | Strength, abrasion resistance, and required fabric weight |
| Technical textiles | Application-specific mechanical and functional properties |
These considerations do not establish fixed yarn-count ranges. The appropriate count depends on the fabric design, fiber properties, machine limitations, and required performance. Confirm the selection through sampling, testing, and production trials.
Relationship Between Yarn Count and Yarn Strength
Strength and count of yarns are related but measure different properties. Yarn count gives an indication of the fineness or coarseness of the yarn, and yarn strength gives an indication of the resistance of the yarn to the breaking load applied.
A higher breaking force may be achieved with a coarser yarn, due to the fact that a coarser yarn will have more material per unit length. This in itself however is no guarantee of the strength of its fibres, nor of the efficiency of its structure. The properties of the fibre, as well as the process and formation of the yarn, also affect the strength of the yarn.
Breaking Force vs. Tenacity
Breaking force: force needed to break a yarn in a tensile test. It is usually measured in centinewtons (cN).
Tenacity is a measure of breaking force per unit of linear density and is generally expressed as centinewtons per tex (cN/tex).
Tenacity= Breaking force/Linear density (tex)
For instance, if the linear density of a yarn is 20 Tex and the breaking force is 400 cN, the tenacity of the yarn is:
Tenacity = 400 ÷ 20 = 20 cN/tex
Tenacity is a measure of the strength performance of yarns of different linear densities. Now, however, comparisons are valid only if the samples are tested under similar conditions with an appropriate test procedure. Learn our
Conclusion
The selection of the proper yarn count for air jet spinning depends on accurate measurement, knowledge of the properties of the fibers, and testing under actual operating conditions. Consider count along with spinning stability, yarn evenness, strength, and end use, instead of as an independent specification. Fluctuating test results and unrecorded production trials leave you with a lack of confidence in the yarn that you are using and that you are getting right.
