Sorting of foreign fibers in cotton

Application field: Sorting

At present, the problem of foreign fibers mixed in cotton in our country is prominent. Although the proportion of foreign fibers mixed in cotton is small, the harm is very great. After being struck and combed by textile machinery, the irregular fibers break longitudinally and separate laterally, and their quantity increases several times. During spinning, the scattered fibers of the opposite sex can easily cause the cotton yarn to break, reducing production efficiency. When weaving fabric, a large number of fabric surface defects occur, affecting the quality of the fabric surface. When dyeing, the appearance is affected due to different coloring rates.

In domestic cotton processing plants, in order to remove the foreign fibers, apart from strictly controlling the pipes and conducting manual sorting during the purchase process, there are also dedicated personnel who sort the foreign fibers on the cotton stacks before feeding the flowers. This kind of manual sorting is time-consuming and laborious. The application of machine vision technology in the sorting of different fibers not only enhances accuracy but also significantly boosts work efficiency, thereby saving a considerable amount of costs.

Machine vision is used to sort out the foreign fibers mixed in cotton (commonly known as "three filaments"), which refer to chemical fibers, animal fibers and non-cotton fibers, such as polypropylene filament, plastic rope, various colored threads, film, hair, chicken feathers, rags and contaminated cotton, etc.

Main process

After the cotton passes through the cotton separator, the fan drives the cotton through the cotton channel through the glass window. On both sides of the glass window, two high-speed high-resolution color line scanning cameras are used to collect images of the cotton respectively. The image data is transmitted to the industrial control computer. After being processed by the image processing software, the processing results are given to the I/O unit. The impurities are blown into the redundant box through the high-frequency solenoid valve.

In the software, the color difference and brightness information of dissimilar fibers are used to determine whether they are impurities compared with the difference values of cotton fibers. Compare the gray value of each pixel point with the set threshold range.

There are mainly two types of opposite fibers:

Colored impurities, with at least one component of RGB being lower than one component of RGB in cotton fibers.

For highly reflective substances with bright colors and those that exhibit fluorescence effects, at least one of their RGB components is higher than that of cotton fibers.

Due to the unevenness of the pixels themselves in the camera sensor, lens distortion and the unevenness of the light source, there is a certain gray level difference between the two ends and the middle area of the obtained image. The camera can be corrected in a flat field to reduce this difference, or this factor can be taken into account during image processing and a nonlinear threshold can be set when setting the threshold.

Detection method for dissimilar fibers with a system operation interface similar to that of cotton fibers

After a thorough analysis of the main types and materials of the foreign fibers in cotton, it can be known that over 90% of the impurities in the foreign fibers that are similar in color to cotton and are also the most difficult to detect are paper and white polypropylene filament (commonly known as "woven tape filament"), etc. These white substances share a common feature: they contain whitening agents (such as ditriazine aminodistyrene type, coumarin type, etc.) These substances emit bright fluorescence with wavelengths of 400 to 500 nanometers under ultraviolet light, while cotton fibers do not change color under ultraviolet light. This difference is an important basis for distinguishing cotton from white fibers of the opposite sex. The wavelength of ultraviolet rays ranges from 10 to 400 nm, among which the photochemical effect of ultraviolet rays with a wavelength of 200 to 400 nm is the most significant.