Inspection method for the quality of dyed yarn

Except the obvious color knot, color fastness and color difference, the inspection methods of the other spinning items are the same as those of the natural yarn. In daily production, the tube yarn can be inspected according to the standard, but when the user has objections to the quality of the product, the package inspection should be used and must be carried out under standard test conditions. The test methods of obvious color knot and color fastness are described as follows:
1. Definition of color knot
The color knot is formed by the dyed and natural immature cotton or stiff cotton due to poorly assembled in the process of embossing or spinning, and the color appears.
2. Determination of obvious color knot
1) When the content of dark fiber in color spinning is 30% or more, the obvious color knot refers to the dark large neps and natural neps. When the content of dark fiber is below 30%, the obvious color knot refers to the natural color of large neps and dark neps.
2) The large neps in the obvious color knots refer to the color knots with the thickness up to 2.5 times of the original yarn.
3) When the dark fiber content or natural fiber content of color spinning is less than 15%, if the natural fiber or dark bundle fiber is wrapped around the yarn, because the color is more obvious, they are counted as obvious knots.
3. Calculation of obvious color knot
The obvious color knot (grain) is equal to the total number of obvious color knots in 10 squares on both sides of 10 blackboards.

4. Inspection method
1) Based on package yarn, take 10 blackboards per batch.
2) Requirements for the inspection location: try to use north-facing natural light sources. During normal inspection, there must be a large window, and the window must be free of obstacles to ensure sufficient light in the window.
3) Requirements for light source inspection: Generally, it is carried out at an illumination of not less than 400LX (maximum not more than 800LX). When the illumination is less than 400LX, light inspection (with cyan or white fluorescent tubes) should be added. The light should be incident from the left rear, the placement angle of the inspection surface should be 45 ± 5 ° from the horizontal plane, and the shadow of the inspector should be avoided from being projected on the blackboard.
4) Inspection steps: first insert the light blue (or other color) bottom plate between the sample and the blackboard, and then use the original blackboard piece to press on the sample to test the obvious color knot in each square of the front and back sides.
5) Note: The yarn should not be turned during the inspection, and the line of sight should be perpendicular to the sliver. The distance should be based on the principle of the inspector's eyesight to identify the defect without effort.
5. Requirements for color knot inspection
The obvious knot of colored spinning is different from the neps of natural yarn, which is the main indicator of the quality of the knitting. Therefore, the obvious knot inspection of colored spinning should be combined with the actual quality of the knitted fabric. The general color Spinning factories will increase the inspection of fabric samples.