Set the drawing process to control the neps and linters in the drawing process
The drawing process of drawing can be divided into two types: "reverse drafting" and "swing drafting". What they have in common is that they can improve the uniformity of the sliver and improve the straightness of the fiber, but the emphasis on the degree of separation between the two is different, and the shortcomings are also obvious. It is best to achieve the advantages of both and overcome their shortcomings, so that the drawn fibers can achieve good control, improve uniformity and fiber straightness.
Draft allocation adopts "reverse draft, large rear area"
First of all, the total drafting process uses "reverse drafting", feeding 8 slivers together. To increase the total draft multiple of the head lane, as long as it is slightly higher than the combined number, the final lane requires the draft multiple to be slightly lower than the combined number. Secondly, the first and last draws are used in the rear zone to increase the multiple, that is, the first draw is expanded to between 1.75 and 2.10, and the last draw is expanded to between 1.30 and 1.35, assuming three and two The parameter is between the first and the last, it is easy to be too large at this time. Use the spacing of the large rear area to match, and the results will be better.
The new technology mainly uses "reverse drafting", which is to ensure the uniformity of the strip, and then increase the draft ratio of the rear zone to improve the straightness, separation and parallelism of the fiber, and play the "straight drafting" The advantages of the machine are to reduce the neps and short pile level as much as possible while increasing the production speed of the draw frame.
In practice, this method is fully applicable to the production of pure cotton varieties, and it can also obtain better results for chemical fibers, wool, and hemp.
When the total draft of the head road is higher than the combined number. When the head of the "reverse draft" is higher than the combined number, it will cause the whole stem to deteriorate, and with the continuous increase of the multiple, the degree of deterioration will continue to increase, which is also the main feature of this method. . The processing of the first draw is mainly about the fiber straightness, separation and mixing, but not to solve the problem of dryness. Through production practice, it has not been found that the use of "reverse drafting" affects the overall performance.
The main purpose of increasing the "reverse drafting" multiples of the head-end drafting is to arrange all drafting tasks in the head-end, so as to avoid excessive pressure on the end-track and increase the adjustment space for the entire end-drawing. To ensure that all indicators are completed.
The total draft distribution uses "reverse draft", and each draw is mainly higher than the posterior draft multiple. The multiple of the first draw is basically maintained at 1.8 to 2.1, generally the feeding amount is below 22 g / (5 m) (10 feeds), and when the feeding amount is above 22 g / (5 m), the first passage The draft multiple of the rear zone of the draw frame must be continuously increased, and once the sliver quantification is relatively large in the production process, the draft of the rear zone must be enlarged so that a better effect can be maintained.
Increase the drafting of the rear zone of the draw frame in order to be able to exert the advantages of "smooth drafting", increase the fiber straightness and separation, and avoid the occurrence of neps.
Open the "live neps"
In the process of merging and drawing, the draw frame not only needs to straighten the hook of the fiber and undertake the main task of blending cotton. After practical research, it is found that it can also open the "live neps", which also makes the drawing process possible One of the processes to reduce the yarn neps, there is a good room to explore.
The "live neps" mentioned here are not true neps, but due to various reasons, the hooked fiber bundles in the direction of the sliver being fed are messy, if they are not straightened during the drawing process , The fiber mass may be tangled into true neps under the action of friction, so it must be adjusted during merging and drafting to open it into a normal drafting fiber whisker, which cannot be successfully opened. Neps will evolve into real neps.
This method is difficult to understand thoroughly through theory, but it has a good effect in production practice. Therefore, in order to reduce the formation of neps in the drawing process, the method of increasing the post-drafting can play a better effect.
With the improvement of the draft of the rear zone, the draft of the main zone will be further reduced, so the middle of the three draws will take the middle value of the first and the last, and take a larger grasp. Get good results.
Normally, the neps account for about 20% of all yarn defects.
It is worth noting that the greater obstacles must be overcome to complete the above drafting purposes, mainly because: ① At high speeds, the time for the sliver to pass the two roller gaps is very short, so a larger gap must be provided It can complete its function; ②Because there is a certain angle between the surface rib and the roller bus, the fiber is inclined in the direction of the rib during the drafting process, if the gap is not large, it is easy to form neps; ③ larger The draft in the rear zone must have a larger space for spacing, otherwise the draft will not open, and it is easy to form long, thick and thin.
Lower cotton linters
The increase in the draft ratio of the rear zone must be accompanied by the decrease of the draft in the main zone. And in practice, it is concluded that it is not the pitch but the multiple of draft that breaks the fiber. The broken long fiber forms a new short fiber, which becomes a spun hairiness in the back lane. This is also the main reason why some manufacturers have high spun yarn hairiness and are not strong enough. On the basis of the previous one, once the rear zone increases by 0.1 to 0.2 times, the hairiness usually drops by about 20%.
Stabilize and improve the evenness
Practice has shown that the increase of the draft multiple in the rear zone must be accompanied by the decrease of the draft multiple in the main zone, which can optimize the entire link, and can make the whole index of the whole line more stable, the whole curve more smooth, the index of the index The range of fluctuations is significantly reduced. Usually on the basis of the previous, once the rear zone increases by 0.1 to 0.2 times, the evenness of the strips increases by 2% to 3%.