2、 Several common mechanical waves
2.1 circular strip wave
When the bobbin and the coiler rotate relatively, the sliver will be stretched when it moves to the periphery of the bobbin, and it will be squeezed when it moves to the center of the bobbin, resulting in additional draft and periodic irregularity, which is called coiling effect. The pseudo mechanical wave caused by coiling effect has a wavelength of λ = 2 × π × RS (RS is the coil radius of the coiler, which varies with the diameter of the coiler, generally 1-1.2m). In severe cases, a series of odd and even harmonics (60cm, 40cm mechanical waves) will appear. In order to judge whether the true or false mechanical wave is similar to the length of the sliver, the tested sliver can be tested backward or directly sampled from the inclined tube of the coiler with a tray (the sliver does not enter the bobbin) for testing.
2.2 "lap wave" of comber
In comber, due to the fiber bundle separation and poor joint when the nipper plate moves, the cotton web will have periodic thickness unevenness, and the wavelength range is about 30-50cm, which generally does not affect the yarn quality. Wavelength λ = up / N1
Where: up is the stripping speed of combing machine (M / min); N1 is the clamp number displayed on the panel (two-way, clamp times / min).
2.3 draft wave of spinning
In the drafting area, the floating fibers are out of control and run unsteadily, resulting in uneven thickness and forming draft waves. The main factors causing draft wave are: raw material change, poor configuration of process and parts, bad or missing status of process parts, sudden change of pressure, change of draft, bad air-conditioning environment, etc. On the spinning spectrum, the draft wave at 7-10CM should be checked if it is an individual spindle
(1) No lower apron spinning or apron damage.
(2) Whether the pressure is too light.
(3) Whether the spacer block is normal.
(4) Whether the position and operation of upper and lower apron are normal.
(5) Whether the concentrator position is correct.
In case of the whole vehicle, check:
(1) Whether there is the problem of excessive traction force caused by improper process configuration.
(2) Whether the raw materials have changed.
2.4 drawing draft wave
On the spectrum of high-speed drawing frame, if there is obvious draft wave at 1.5-4cm (the basic wavelength is about 2.2cm), it is generally caused by improper adjustment of self-adjusting leveling point.
2.5 spinning tension effect wave
Under the condition of nearly full tube, the fluctuation of winding tension will lead to periodic unevenness when the steel ring plate drives the yarn to move up and down, and the wave length is the same as that of the spinning ring (mostly in the range of 8-9m or 5-6m). If the spinning speed of the spinning frame is UPM / min and the lifting times of the ring plate are n1 times / min, the wavelength of the effect wave of the spinning tension is λ = up / N1. The tension effect wave of spinning will disappear automatically after it is warped.
Twist effect wave of 2.6 roving
During roving twisting, due to the "twist effect", the roving sliver will have periodic irregularity, and its wavelength is related to the roving frame winding speed up (M / min) and roving frame flyer speed n1 (R / min).
(1) True twist wave: each twist of true twist will result in two unevenness on roving, and the wavelength corresponding to each irregularity is λ = 0.5 × up / N1. Generally, the wavelength is about 1cm, which is relatively weak. It is stronger on individual roving frames and affects spinning.
(2) False twist wave effect wave: when testing roving, there is mechanical wave at about 2-3cm, and the wavelength is λ = up / N1. This is generally a pseudo twist wave effect wave, which will not affect the spectrum of the yarn after drawing.
