Polyester yarn

100% Polyester Material and Polyester Ring Spun Yarn 40s2 Raw White

Principle analysis of mechanical wave in spinning process

The spectrum of yarn sliver is mainly used to analyze the causes of various periodic unevenness of yarn sliver, and to eliminate the problems in equipment or technology in time. In mechanical wave analysis, it is necessary to distinguish the fundamental wave from each harmonic wave, in which the harmonic frequency is an integral multiple of the fundamental frequency. Fundamental wave and harmonic wave have their own amplitude and phase. Fundamental wave and harmonic wave can be superimposed into periodic wave of various shapes. The wavelength of synthetic wave is the wavelength of fundamental wave.

1、 Some notes on the application of spectrogram

1.1 draft wave

The drafting wave is the structural difference of each section of sliver caused by the random distribution of fibers, and the highest peak is at 2.5-3.0 times of the average fiber length.

1.2 mechanical wave

Mechanical wave is caused by mechanical defects or faults (such as roller eccentricity, gear missing teeth, tooth surface wear, dirt in rotor, needle cloth defect, etc.) or improper equipment adjustment, which generally occupies one or two adjacent channels.

Credibility of 1.3 waves

In order to ensure the credibility of the test results, the number of measured wavelengths must reach 25, otherwise the test time and sample length should be extended. It should also be noted that if there are abnormal phenomena on the spectrogram, do not rush to analyze or draw a conclusion. The test should be repeated three or four times to confirm that the same phenomenon appears on the spectrum before it can be regarded as credible.

For example, if the test speed is 400m / min and the test time is 1min, then the sample length is 400m, then the mechanical wave with wavelength less than 16m on the spectrogram is credible. When the test time is extended to 5min and the sample length reaches 2000m, the mechanical wave with the wavelength less than 80m is credible.

1.4 "thumb rule" for harmful waves

Periodic irregularity or draft irregularity in yarn, which is reflected in the height of "chimney" or "hill" in spectrogram, will cause adverse effect on fabric appearance in varying degrees. We should not only pay attention to the absolute height P of the "chimney" or "hill", but also compare it with the normal amplitude B at the corresponding position of the spectrum. If the "chimney" occupies two or three channels, the total height P should be accumulated for comparison. The "thumb rule" can be followed, that is, when p > b / 2, the effect on fabric appearance can be considered as serious.

1.5 matters needing attention in spectrum analysis

(1) The difference between the calculated and measured values is within ± 15%. Analysis and calculation is only a means, not an end, and the final conclusion should be confirmed on the basis of analysis and confirmed by field troubleshooting.

(2) Regular sampling should be adopted in daily test, that is, each processing part (each spindle and each eye) of the spinning equipment should be inspected at least once within the specified time. For example, Uster has suggested that the time required to check the whole equipment is 1 week for carding machine, 2 days for comber, 1 day for final drawing frame, 1 month for roving frame and 6 months for ring spinning frame. The sampling plan should be designed scientifically and the key varieties, equipment and processes should be monitored and controlled.

(3) When analyzing the fault, we should make clear the train of thought, pay attention to distinguish individuality and generality; static and dynamic; light load, heavy load; stable or sometimes not.

(4) If necessary, some simulated fault tests can be carried out for comparison and verification, so as to know what it is and why it is. At the same time, in the process of solving problems, from phenomenon to analysis, calculation, to the whole process of troubleshooting, we should make records, constantly summarize and improve.

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.

3、 Analysis and calculation method of mechanical wave

3.1 common fault calculation of drafting system

It is the most basic analysis method to calculate the possible fault position according to the transmission ratio or draft multiple. Take the gear transmission parts of jwf1566 ring spinning frame as an example

The wavelength of drafting parts (roller, roller and apron) is λ = π × di × di × E

Where: Di is the diameter of the drafting part; Di is the drafting multiple from the part to the front roller; E is the drafting multiple of the next process.

For example, on the spectrogram of this process:

The wavelength of front roller is π × D (diameter of front roller).

The wavelength corresponding to the middle roller is π × D (diameter of middle roller) × D1 (draft multiple of front zone).

The wavelength corresponding to the apron = π × D (diameter of the epithelial ring) × D1 (draft multiple of the anterior region).

(d) × the length of the draft roller.

3.2 calculation of common mechanical faults in carding

Suppose that the carding speed is up (M / min), the doffer diameter is D1 (m), and the doffer speed is N1 (R / min). There is a damage on the doffer card clothing, which causes the uneven thickness of the web after one revolution. The wavelength of the periodic irregularity in the output sliver is λ, which is equal to the perimeter of the faulty part doffer multiplied by the draught multiple D1 from doffer to the output end, that is: λ = π × D1 × D1 = π × D1 × carding speed / doffer linear speed = up / N1

According to the known production speed up and mechanical wave length λ of the equipment, it is easy to calculate N1. Based on this, it is possible to find the parts on the equipment whose rotational speed is basically consistent with N1, which may be the source of the fault. It is more direct and convenient to use this method to analyze the fault position when it is reciprocating.

3.3 calculation method of transmission ratio

Wavelength λ = π × D × I × e

Among them:

D is the diameter of the front roller.

I is the transmission ratio between the gear and the front roller.

E is the draft multiple of the next process.

4、 Conclusion

With the help of spectrogram, the cause of yarn periodic unevenness can be analyzed, and the hidden trouble of quality can be quickly found out and eliminated, and the economic benefit of the enterprise can be improved. Many of our polyester yarn factories don't know whether to adopt this technology?