The hairiness tester consists of a light source (LED) and a monochrome CCD camera. The light source is slightly tilted and illuminates the fabric surface tangentially, so that the camera does not register the shadows of the protruding fibers, but the refracted light. This type of measurement is called dark field measurement, because the background remains black, whereas the objects are shown bright.

Camera and light source are installed in a dust and water proof enclosure (IP67). The lenses of the camera is protected by scratch-resistant sapphire glass. Both parts of the unit feature air nozzles which keep the optics dust-free.

The camera signal (up to 2 cameras configuration is possible) is sent to an industrial PC via G bit Ethernet cable. The industrial PC is located in the main cabinet and runs an analysis program, which determines the bottom limit (fabric surface) and top limit (topmost visual point of hairs) of the fibers.

The distance in-between is the length of the hair. After this, a variety of statistical data is calculated, where for the evaluation of the hairiness the mean value and the standard deviation are used. The mean value reflects the grade (how short are the hairs in general), the standard deviation reflects the quality (the constancy of the hair length) of the hairiness. We define hairiness as the sum of the mean value and the standard deviation.

The picture shows the screen of the PC where the signal coming from the camera is evaluated. The important values are Hn (mean value) and Sn (standard deviation). Top right is the camera picture, below is a histogram showing the distribution of the hair lengths. The above example shows hairs between approx. 0.15 mm and 1.8 mm length, the major part of them being approx. 0.3 mm long.

Unsinged fabric.

The second picture shows the operating panel of a singeing unit (our laboratory machine) consisting of a centre unwinding device, dedusting unit, singeing machine (for woven fabrics and knitwear), two more dedusting units and a big batching device with centre winding. The hairiness tester is located behind the dedusting unit following the singer. The right-hand side shows a pre-set hairiness value of 205, the actual value being 2188.

By means of Osthoff Senge hairiness tester, we are - for the first time - able to measure and influence the important variable, i.e. the hairiness, directly. The measured value is used to control the process parameters, or in more detail: intensity of the burners is adjusted depending on preselected hairiness value.

Advantages:

• It is ensured, that the whole batch has the same hairiness value.
• In the future, similar articles will be singed with the same parameters (repeatability).
• The gas consumption is only as high as necessary. If the desired hairiness is achieved with a lower intensity, the settings are adjusted accordingly.