The existence of overlength fiber in manufactured staple can cause serious problems in the spinning of these fibers into yarn. Overlength fibers may create problems in carding, but more especially high-strength multiple cut fibers may cause cockling in spinning.

Since the overlength fibers are caused by dull or damaged cutting knives or by uneven flow of tow to the staple cutter, their existence within the fiber population is not uniform and their occurrence in the population follows a highly skewed distribution.

Manual methods of determining overlength fiber require much more operator time, and the standard deviations of the test between laboratories and operators are high. Use of the Fibrosampler method greatly reduces both operator time and standard deviation of testing.

In manufacturing it is important to know if fibers are overlength due to looping of the tow or multiple length due to damaged cutters.

This method for testing staple fiber for overlength fiber is not recommended for acceptance testing (see 13.1).

In some cases the purchaser and the supplier may have to test a commercial shipment of one or more specific materials by the best available method, even though the method has not been recommended for acceptance testing of commercial shipments. If there are differences of practical significance between reported test results for two laboratories (or more), comparative test should be performed to determine if there is a statistical bias between them, using competent statistical assistance. As a minimum, use the samples for such a comparative tests that are as homogeneous as possible, drawn from the same lot of material as the samples that resulted in disparate results during initial testing and randomly assigned in equal numbers to each laboratory. The test results from the laboratories involved should be compared using a statistical test for unpaired data, a probability level chosen prior to the testing series. If a bias is found, either its cause must be found and corrected, or future test results for that material must be adjusted in consideration of the known bias.

FIG. 1 Fibrosampler

FIG. 2 Fibrosampler Combs

1.1 This test method covers the determination of the percent by number of overlength or multiple length fibers in a sample of manufactured cut staple. The method is applicable to fiber taken immediately after manufacturing, from the bale, or from partially processed stock.

Note 1—For measurement of length and length distribution of manufactured staple fibers, refer to Test Method D5103.

1.2 This test method covers procedures using the Fibrosampler Model 335A (inch-pound units), the Fibrosampler Model 335B (SI units), and Fibrosampler combs Model 336.

1.2.1 The Fibrosampler Model 335A is equipped with a sample plate that has 15.8-mm (⁵/₈-in.) diameter sample holes and is recommended for use on blended staple taken from the fiber blender or from a carding machine.

1.2.2 The Fibrosampler Model 335B is equipped with a sample plate that has 10-mm (0.4-in.) diameter sample holes and is recommended for use on unblended staple as may be taken from the fiber cutter or from a bale of staple fiber.

1.3 The values stated in either SI units or inch-pound units are to be regarded separately as the standard. The values stated in each unit are not exact equivalents; therefore, each unit must be used independently of the other.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.