Spinning Frame Drafting Device Control for Yarn Evenness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for controlling drafting devices in spinning frames result in yarn unevenness due to delayed twisting and untwisting, which leads to yarn breakage and unevenness during activation and deactivation processes, as the change in break draft ratio affects the thickness of the spun yarn without considering its immediate influence.
Innovation Solution
A method that controls the drafting device by changing the break draft ratio during deactivation to reduce load torque and untwisting, and synchronously adjusts the main draft ratio during reactivation to correct yarn unevenness by calculating the timing of the fiber bundle's passage through the rollers, using independent servo motors and a controller to manage the speed of the front, middle, and back bottom rollers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the break draft ratio is changed during deactivation to reduce load torque and limit untwisting, then yarn breakage is reduced, but yarn unevenness occurs due to the immediate influence on fiber bundle thickness
Solution Approach 1:
The controller calculates the timing when the fiber bundle passes through each roller and schedules the main draft ratio change to occur precisely when the fiber bundle passes the front roller. This preliminary timing calculation ensures that the draft ratio correction is applied at the optimal moment to compensate for the thickness change caused by break draft ratio adjustment, thereby preventing yarn unevenness while maintaining the benefits of reduced untwisting.
Solution Approach 2:
The system dynamically adjusts two parameters: the break draft ratio (to limit untwisting during deactivation) and the main draft ratio (to correct yarn thickness). By coordinating changes in both parameters with precisely calculated timing, the system resolves the contradiction between reducing yarn breakage and preventing yarn unevenness.
2Reliability
If the deceleration rate of the middle bottom roller is changed to adjust the break draft ratio, then untwisting is limited, but the main draft ratio changes causing immediate influence on spun yarn thickness
Solution Approach 1:
The controller monitors the timing of fiber bundle passage through the drafting device and uses this feedback to determine when to adjust the main draft ratio. This feedback mechanism ensures that the main draft ratio is changed at the precise moment when the fiber bundle passes the front roller, compensating for thickness changes and maintaining uniform spun yarn quality while the break draft ratio adjustment limits untwisting.
Solution Approach 2:
The system coordinates changes in multiple parameters: the deceleration rate of the middle bottom roller (affecting break draft ratio and untwisting), and the main draft ratio (affecting yarn thickness). By synchronizing these parameter changes with calculated timing based on fiber bundle position, the system resolves the contradiction between untwisting control and yarn thickness uniformity.
3Productivity
If the spinning frame is reactivated with increased acceleration rate to return to normal operation, then productivity is improved, but yarn unevenness occurs due to tentative draft ratios
Solution Approach 1:
The controller calculates the timing for main draft ratio adjustment in advance based on the expected position of the fiber bundle during reactivation. This preliminary timing calculation allows the system to quickly reactivate the spinning frame while ensuring that the main draft ratio is adjusted at the precise moment when the fiber bundle passes the front roller, preventing yarn unevenness even during rapid reactivation.
Solution Approach 2:
The system dynamically adjusts both the break draft ratio and main draft ratio during reactivation, coordinating these parameter changes with precisely calculated timing. This allows the spinning frame to be reactivated quickly (improving productivity) while maintaining yarn quality (preventing unevenness) through synchronized parameter adjustments.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
In a method for controlling a drafting device of a spinning frame, the drafting device includes a front bottom roller 12, a middle bottom roller 13, a back bottom roller 14, and motors (15, 16a, 16b, 17a, 17b) that independently drive the bottom rollers. The method includes changing a break draft ratio of the drafting device in a deactivation process of the spinning frame so that a load torque of the drafting device is smaller than when the break draft ratio is set to a value for normal operation to limit untwisting of the bottom rollers. The method further includes changing a main draft ratio when a fiber bundle, which has passed by the middle bottom roller 13 during a period the break draft ratio is changed, passes by the front bottom roller 12, to cancel influence on the fiber bundle of the changing in the break draft ratio.