Adjustment of drafting force
In daily production, changes in product varieties, raw materials, seasons, climate, etc. often occur. Changes in these factors will inevitably cause changes in drafting force, so process adjustments must be made. Process adjustment essentially means adjusting the drafting force or holding force so that the drafting device can adapt to new changed conditions.
The most common method is to adjust the drafting force or holding force by adjusting the basis weight, draft multiple, roller spacing, rubber roller pressure, etc. For example, when changing varieties to spin fine special yarns, since fine special yarns require raw cotton with long length, low linear density, good uniformity, many natural twists, and good maturity, the drafting force of such raw cotton spinning must be large, so , it is necessary to use light weight, larger draft multiple, larger roller spacing or heavier rubber roller pressure (changing the pressure means changing the holding force to adapt to the draft force).
In daily production, there are large differences in the length and linear density of raw cotton from batch to batch, or saw-tooth cotton with good uniformity is used to replace top roller cotton spinning. Due to changes in drafting force , causing the yarn to slip under the roller nip, which can easily cause the sliver to deteriorate. At this time, it is necessary to appropriately enlarge the roller spacing or increase the roller and pressure to adjust the drafting force. If you want to adjust the drafting force in the rear area of the spinning frame, you can also adjust it by adjusting the twist coefficient of the roving.
Stability of drafting force
In order to improve the evenness of the yarn, in addition to controlling the size of the drafting force, It is also necessary to control the fluctuation of the drafting force, that is, to reduce the unevenness of the drafting force and keep the drafting force stable. There are two main ways to stabilize the drafting force in production:
1) Reasonable selection of process parameters, that is, reasonable selection of yarn sliver quantity, draft multiple, roller spacing and rubber rollers Pressure and other process parameters are used to keep the drafting force within a certain range and adapt to the holding force.
2) Strictly grasp the differences in performance of raw cotton between batches. When blending cotton, the difference in average length and linear density of mixed cotton fibers before and after batching should be strictly controlled to minimize fluctuations in drafting force; at the same time, changes in the mechanical state of the drafting device, wear and aging of machine parts, and changes in workshop temperature and humidity and other factors directly affect the change of drafting force. Therefore, in order to stabilize the drafting force, relevant work must be done well at the same time.
3) Controlling appropriate drafting force and maintaining its stability are necessary conditions to ensure the stability of fiber movement during the drafting process, which directly affects whether the drafting process can proceed normally and Product uniformity. To this end, the drafting force must meet two limiting conditions:
① The upper limit of the drafting force cannot approach or exceed the holding force of the roller jaws under normal pressurization;
② The lower limit of the drafting force should maintain appropriate tension in the weakest part of the yarn in the drafting area.
The drafting force must be limited within these two limit values, and the tension generated by the drafting force on the yarn sliver should be reasonably distributed along the yarn sliver. The tension must not exceed the strength of the yarn, otherwise it will cause the yarn to split or even break, making the drafting unable to proceed normally. </p
