Fiber sampling method - Numerical, Random and cut square method

Fibre sampling method

Numerical sample / Unbiased sample

The numerical sample is a sample that has the percentage of fibre length equal to the percentage of fibre length of bulk materials.

This means the sample truly represents the whole quality of bulk in length parameters.

To prepare samples from sliver, roving, and yarn by numerical method, a Bulk of fibres are collected from the sliver, roving, or yarn surface by untwisting.

Lay down all fibres in a parallel manner. As mentioned in the below figure, suppose A and B are two vertical planes parallel to each other with a 1-2 cm distance.

Now separate all fibres which have left-hand ends starting between the A and B planes.

(Remove fibres that have stating points beyond the AB plane and also fibres whose only middle portion passes between A and B.)

In this way, the prepared sample has an equal portion of fibre length with the bulk portion.

(Consider that various lengths of fibres are equally distributed in sliver, roving, or in yarn structure to, achieve an equal percentage of fibre length.)

However, a slight variation comes into results, when fibre samples are collected rather than the A and B planes. (For samplings from another plane like P and Q, the length of fibre percentage may vary slightly.)

This line of planes is used because the chances of fibre passing between A and B planes are proposals to fibres' length and due to carding and drafting process, higher chances to equal distribution of fibres in sliver, roving, or yarn surface.

Numerical sampling method

Random draw method

The random draw method is generally used for the card sliver and ball sliver.

In the random method, it is necessary to take a sample from the sliver can very carefully by hand and during its breakage.

Random sampling

Fibres at the end or breakpoint should not be cut or broken.

A sample of silver is then placed over the first velvet boards with the parted end near the front of that board.

The opposite end of the sliver is weighed down with a glass plate to stop it from moving.

Random Sampling Method

A wide grip that is capable of holding individual fibres is then used to remove and discard a 2mm fringe of fibres from the parted end.

This procedure is repeated, removing and discarding 2mm draws of fibre until a distance equal to that of the longest fibre in the sliver has been removed.

The sliver end has now been 'normalized' and any of the succeeding draws can be used to make up a sample as they will be representative of all-fibre lengths.

This is because they represent a numerical sample as described above where all the fibres with ends between two lines are taken as the sample.

When any measurements are made on such a sample all the fibres must be measured.

Cut square method

The cut square method is basically used for sampling fibres that are drawn from the yarn.

The required length of the yarn for testing is cut from the yarn and the end is untwisted by hand.

The ends of the fibres are then laid on a small velvet board and covered with a glass plate to minimize variation.

The untwisted end of the yarn is then cut about 5mm from the edge of the plate.

All the fibres that project in front of the glass plate are removed one by one with a pair of forceps and discarded.

By doing this all the cut fibres are removed from the glass plate, leaving only fibres with their natural length. Thereafter, moved the glass plate back a few millimetres so that more fibres are exposed.

These fibres are then removed gently one by one and then measured.

When these all fibres have been measured the plate is moved back again until a total of 50 fibres have been measured completely.

In each case of fibre transferring and measurement, once the plate has been moved all projecting fibre ends must be removed and measured.

The whole process is then repeated on fresh lengths of yarn chosen at random from the bulk until sufficient fibres have been measured.

Cut square method

Questions -

What is the numerical or unbiased sample?
What is the random draw method?
What is the cut-square method?

References

Cenote, M. (2015). Google Books. In The SAGE Guide to Key Issues in Mass Media Ethics and Law (pp. 847–858). SAGE Publications, Inc.

Fundamental textile testing: Mechanical and Physical Tests. (n.d.). Fundamental Textile Testing: Mechanical and Physical Tests. from https://www.eurofins.com/textile-leather/articles/fundamental-textile-testing-mechanical-and-physical-tests/

Handbook of textile testing and quality control - Google search. (n.d.). G.Co. from https://g.co/kgs/RvVMgm

NPTEL IIT. (n.d.). Note.Ac.In. from https://nptel.ac.in/courses/116102029

Elsevier. (2016). Performance testing of textiles (1st ed.). Woodhead Publishing.

Houck, M. M. (2009). Identification of Textile Fibers (M. M. Houck, Ed.; 1st ed.). Woodhead Publishing.

Textile School. (2010, October 27). Fibre Identification - tests to identify a fibre. Textile School. https://www.textileschool.com/321/fiber-identification-tests-to-identify-a-fibre/

Trivedi, Y. (2020, April 10). Identification of Textile Fibers. Textilesphere.com. https://www.textilesphere.com/2020/04/identification-of-textile-fibers.html

(N.d.). Textilelearner.net. from https://textilelearner.net/classification

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