1 The process parameters of the draw frame mainly include the following aspects
A. Roller spacing
B. Draft multiple
C. Pressure rod height
D. Front roller speed
E. Number of mergers, number of drawing passes, and draft distribution of two drawing passes
F. Quality control standard settings
G. Others (pressure, bell mouth diameter, tension draft, etc.)
2 Objectives of drawing process design
A. The fibers are well straightened, the evenness is improved, the raw materials are fully mixed, and the subsequent production is satisfied.
B. Yarn defects rarely occur.
C. Higher production efficiency.
3 Setting of the draw roller gauge
The main factor that determines the size of the roller gauge is the drafting force. It first It is closely related to the length of the fiber. It is also related to the fineness and uniformity of the raw materials, the quantity of the feed products, the curl and draft ratio of the fiber, etc. The size of the roller gauge is finally determined through experiments. When producing cotton fiber, the roller gauge is determined by referring to the fiber length distribution chart
A. The drafting gauge is determined according to the following scheme:
①. Main drafting distance = longest fiber length
②. Main drafting distance = 1% of longest fiber length + (2~3)mm
③. Main drafting distance = 2.5% longest fiber length + (9~10)mm
④. Other influencing factors (poor straightness, large back draft, high short pile, light basis weight, the gauge should be set smaller)
B , the drafting distance after drawing is determined according to the following scheme:
①The longest fiber length.
② Based on the main drafting distance + (4~8).
③The rear drafting distance setting must also consider factors such as the rear drafting multiple, fiber uniformity, and sliver ration. (Large draft ratio, high short pile, light basis weight, and the gage should be set smaller)
C. The longest fiber length and 2.5% of the fiber length are different from those drawn by hand. Approximate relationship of length
①. The longest fiber length is about hand-pulled length + 14mm.
②. The length of 2.5% fiber is approximately hand-pulled length + 8mm.
4 Settings for drafting in the rear area of drawing
The role of drafting in the rear area of drawing is to prepare for straightening of fibers and to prepare for the drafting of the front area. Stretch to prepare.
The determination of the draft ratio in the rear area is based on the raw material conditions, length, length uniformity, straightening of the semi-finished fiber, number of drawing passes, sliver ration, roller spacing, etc. Sure. It must be noted that the selection of the draft ratio of the small back zone must take into account the equipment status.
Principles for determining the draft ratio in the rear area:
①. The larger and more consistent the fiber length is, the larger the draft ratio can be. .
②. The shorter and more inconsistent the fiber length is, the smaller the drafting multiple must be.
③. The more curled the raw material is, the greater the draft ratio of the back area must be.
④. The more passes there are, the smaller the drafting ratio of the rear area must be.
5 Number of drawing passes
A. Single drawing after combing is the development direction, but it must be based on a certain basis implementation.
①. Draw frame with short-segment autolevelling.
②. The quality of the combed sliver reaches a certain level (unevenness inside and outside).
The reason why only one draw can be used after combing is because:
① The raw materials have been fully mixed (from raw materials There are as many as 6*28*8=1344 times the combined multiple from strip to combed strip).
②. The fiber has reached basic straightening (the cylinder and top comb of the combing machine comb both ends of the fiber).
③. Auto-leveling can fully improve the unevenness of the combed sliver.
Practice has proven that using single-pass drawing after combing can reduce accidental drafting of slivers, reduce yarn defects, and improve product quality and production efficiency.
B. It is feasible to use single-combination for pure cotton carded rotor spinning, but it must be implemented on a certain basis and there are some risks.
①. It must have a high level of carded sliver quality (good mixing, blowing and carding combined sliver with self-levelling of long and short segments)
②. Reliable and efficient autoleveling draw frame
The main factor that enables rotor spinning to adopt single-pass draw frame is: the requirements of air-jet spinning for fiber separation and straightening Different from ring spinning (the fiber transportation of air spinning itself causes damage to fiber straightening, centrifugal force falling, and airflow inhalation), the carding effect of the carding roller and the combined effect of the rotor reduce the fiber elongation value. At the same time, due to the high-efficiency mixing of long and short segments of the blowroom and carding unit, the auto-levelling greatly improves the quality level of the sliver, and then the auto-leveling draw frame ensures the uniformity of the sliver.
However, there are certain risks in using one draw. When the raw materials change frequently, it is easy to cause insufficient mixing of the raw materials, which ultimately leads to dyeing color differences in the product.
C. It is not advisable to use single-bundling for ring-spun pure cotton carding. The main reason is that the fibers cannot be fully straightened and separated, and the single-bundled strips enter the roving and produce high Uneven drafting and unstretched fibers equal short velvet. In addition, the raw materials cannot be fully mixed and may easily produce color differences.
D. Cotton pre-combination cannot be canceled. The main reasons are as follows:
①. Feeding of combed sliver The fibers in small rolls have poor straightening separation and many hooked fibers. When the combing process remains unchanged, the noil rate increases significantly. The noil rate will increase by more than 5% through the test.
②. Due to the poor fiber elongation separation, the carding load of the combing machine increases significantly and the mechanical loss increases.
③. Increased fiber damage.
④. Due to the above reasons�, the cost of the product will increase and the quality will decrease.
6 Combination number
A. Combination number of combing preparation, researched by Rieter Company, total number of combing preparation A draft of 9 to 10 is best for the yarn quality (hairiness, strong unevenness, etc.) and is beneficial to the combing operation. A smaller preparatory draft multiple is beneficial to reducing the stickiness of small rolls. (Confirmed in production practice).
Since the drafting ratio of the strip drawing and rolling equipment is about 1.5 to 2 times, the drafting multiple of the drawing strip should be about 5 to 6 times, taking into account the Quantitatively, the combined number should also be around 5 to 6.
B. The number of combinations after combing. In fact, the number of combinations after single-pass drawing has been reduced. Since the elongation fiber effect of drawing after combing is basically no longer Yes, if the quality of the combed sliver can be guaranteed, the number of combinations should be reduced. This reduction will help reduce the draft load of the draw frame and reduce the unexpected draft of the sliver.
C. The number of pure cotton carding and combining. The front sliver is cleaned and carded and has long and short segments that are self-levelling. Two drawings are used to combine 6 times each. It should be feasible, because the carded sliver after blowing and carding has high-quality mixing effect and uniformity, the mixing effect of drawing has been reduced, and the 36-fold drafting of the two passes should be able to solve the problem of fiber elongation and reduce the The number of combinations can reduce the drafting load and strengthen the control of fibers; it is beneficial to improve the quality level and productivity.
7 Issues that must be paid attention to in the drawing process
A. Prevention of sudden yarn defects.
B. Reduce the increase of neps.
C. There is a certain memory relationship between the settings of roller distance, draft multiple, pressure rod height, and sliver quantitative parameters.
D. The process design must be based on the equipment. Pay attention to reducing the drafting load of the draw frame, otherwise serious quality problems will occur, especially the roller spacing. Designed with a centralized front area for drafting. </p