A quantitative evaluation method for needle and hook scratch damage

Abstract

This invention relates to a method for quantitatively evaluating needle hook scratch damage. The invention establishes a yarn-needle hook wear motion coordinate system, creates a force model of the yarn within the groove, and then calculates the quantified tension fluctuation (ΔT) caused by yarn slippage, the quantified index of yarn scratch damage, and the needle hook structural damage index. Ultimately, a quantitative evaluation standard for needle hook wear can be established. This invention provides a quantitative failure analysis tool for knitting needle manufacturers and R&D teams. By analyzing the scores of individual items in the comprehensive index, R&D personnel can accurately pinpoint shortcomings in product structural design or surface processing, thereby providing targeted guidance for product upgrades and technological iterations.

Description

Technical Field

[0001] This invention relates to the technical field of knitting needle wear evaluation methods, specifically a quantitative evaluation method for needle hook scratch damage. Background Technology

[0002] In high-speed knitting production, wear grooves form on the inner side of the needle hook due to long-term friction from the yarn. Currently, the industry relies primarily on manual experience to determine the degree of needle hook wear, a qualitative rather than quantitative method with significant limitations. Manual judgment is prone to large errors and lacks standardized criteria. Secondly, manual experience is based on needle breakage and a significant decline in fabric quality, lacking multi-dimensional quantitative indicators. Needle hook wear not only manifests as cross-sectional thinning affecting strength but also involves complex physical consequences, such as yarn tension fluctuations and yarn fuzzing. The current lack of a refined grading decision-making system prevents standardized demand matching and economic benefit assessment between needle manufacturers and users, resulting in the waste of high-value needles or the risk of operating defective needles. Therefore, there is an urgent need for a digital, comprehensive, and quantitative evaluation method that integrates structural strength, yarn damage, and tension fluctuations, replacing subjective manual judgment. Summary of the Invention

[0003] This invention addresses the shortcomings of existing technologies by providing a method for quantitative evaluation of needle and hook scratch damage.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for quantitatively evaluating needle hook scratch damage includes the following steps:

[0006] Step 1: Collect loom parameters and yarn parameters. Loom parameters include the sinker advance distance. and yarn bending depth Yarn parameters include yarn radius The static friction coefficient between yarn and knitting needles Yarn pull-back angle and side deflection angle and yarn tension ; Obtain the real-time wear depth at the groove of the knitting needle hook. h ;

[0007] Step 2: Calculate the climbing angle β and the combined resistance angle. The critical tension required for the yarn to escape from the groove ;

[0008] Step 3: Analyze the yarn tension fluctuation and calculate the tension fluctuation ratio. ;

[0009] Step 4: Calculate the yarn damage index Damage to the hook structure ;

[0010] Step 5: Calculate the overall performance index:

[0011]

[0012] in It is a safety gating function used to determine whether the knitting needles possess basic "serviceability":

[0013]

[0014] and The preset structural safety threshold and yarn damage threshold;

[0015] Mass decay function:

[0016]

[0017] This is the preset maximum tension fluctuation ratio;

[0018] Step 6: Based on the comprehensive performance index The value is used to determine the wear level of the loom, and the wear level is used to determine whether the machine needs to be stopped.

[0019] Furthermore, in step 2, the climbing angle β and the combined resistance angle... The critical tension required for the yarn to escape from the groove The calculation formula is:

[0020] ;

[0021] ;

[0022]

[0023] Furthermore, the yarn tension in step 1 Obtain it through one of the following two methods:

[0024] Method 1: Real-time data collection of yarn tension at various times within a time period and calculation of the average value as the yarn tension. ;

[0025] Method 2: Directly collect the fixed yarn tension value set on the loom as the yarn tension. .

[0026] Furthermore, in step 4, the yarn damage index The calculation formula is:

[0027]

[0028] in, Frictional work represents the energy consumed when the yarn slides through the groove. It is a yarn cohesion energy index, representing the ability of yarn fibers to resist separation; This represents the scraping efficiency factor, which is related to the sharpness of the groove edge. Calculated.

[0029] Furthermore, in step 4, the damage amount of the needle hook structure The calculation formula is:

[0030]

[0031] in, λ is the diameter of the needle hook cross-section, which is approximately circular or elliptical, and λ is the notch sensitivity coefficient, which is related to the heat treatment process of the needle material.

[0032] A quantitative evaluation system for needle hook scratch damage uses the above-mentioned method.

[0033] A computer-readable storage medium storing a program capable of implementing the above-described method.

[0034] The beneficial effects of this invention are as follows:

[0035] This invention provides a method for quantitatively evaluating the wear degree of knitting needles corresponding to specific yarns, solving the problem of assessing knitting needle damage. The method can quantitatively determine the wear condition of knitting needles, preventing needle breakage and fabric damage, and avoiding premature needle scrapping. The NOPI comprehensive performance index designed in this invention includes hard judgment thresholds and score evaluations, allowing for hard judgment of fatal losses and soft judgment of non-fatal losses. The judgment method is practical and reasonable, and the final output is a single quantitative index that is intuitive and easy to understand, allowing frontline personnel to quickly judge without professional knowledge, greatly simplifying equipment management. Weaving mills can use the standardized evaluation method provided by this invention to conduct comparative tests on knitting needles from different manufacturers under the same operating conditions. By comparing the NOPI index decay curves of knitting needles from different brands after running for the same amount of time, companies can objectively identify the products with the highest cost-effectiveness and best wear resistance, thereby formulating data-driven procurement strategies and gaining the initiative in supply chain bargaining. This invention provides knitting needle manufacturers and R&D companies with a quantitative failure analysis tool. By analyzing the scores of each item in the comprehensive indicators, R&D personnel can accurately pinpoint the shortcomings of the product in terms of structural design or surface processing, thereby providing targeted guidance for product upgrades and technological iterations.

[0036] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the method flow of the present invention;

[0038] Figure 2 This is a schematic diagram of the structure of the groove at the needle hook of a knitting needle. Detailed Implementation

[0039] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0040] 1. Establish a coordinate system for yarn-needle hook wear motion.

[0041] Let the cross-section (radius) of the yarn A wear groove (depth) on the surface of the hook. )middle.

[0042] Coordinate system definition:

[0043] With the center of the bottom of the groove as the origin .

[0044] Y-axis: Perpendicular to the surface of the needle hook and pointing inward (radial pressure direction).

[0045] X-axis: tangent to the surface of the needle hook backward (the direction in which the yarn moves out).

[0046] Key parameters:

[0047] : Effective radius of cotton thread (considering the compressed state under tension).

[0048] : Groove depth.

[0049] The static friction coefficient between the cotton thread and the steel needle (usually 0.2~0.3).

[0050] Tension at both ends of the yarn.

[0051] Pull-out Angle: The angle between the force vector of the yarn being pulled backward and the normal line of the groove (Y-axis).

[0052] 2. Establish a stress model for the yarn inside the groove.

[0053] When wear grooves appear on the inside of the needle hook, the movement of the yarn will no longer be smooth, but will become a process of "sinking into - climbing up - popping out" of the wear grooves.

[0054] Yarn tension.

[0055] : Lifting angle (wrapping angle, the angle between the two ends of the yarn and the vertical line). It represents lifting vertically upwards.

[0056] Side slip angle (the angle at which the yarn is pulled back). That is, the angle between the yarn plane and the needle plane (the axis of the needle body).

[0057] Radial normal force of yarn on the surface of the needle hook ( ).

[0058] (Wear groove depth): The vertical distance from the deepest point of the pit formed by friction and wear on the inside of the knitting needle hook to the original surface.

[0059] : The maximum slope angle of the groove sidewall. As depth increases... Increase, Increase .

[0060] The coefficient of friction between the yarn and the knitting needle.

[0061] Friction angle :

[0062] When the two ends of the yarn are lifted upwards, a radial resultant force perpendicular to the tangential direction of the yarn is generated. This force presses the yarn into the groove.

[0063]

[0064] When the sinker pushes the yarn into the circular knitting machine, it creates an angle on the yarn. When the force moving outward along the inclined plane is greater than the resistance moving inward along the inclined plane, the yarn slides out along the groove wall. Due to the angle, the normal force of the yarn against the wear notch decreases to tension. This reduces friction by decreasing the component of the force. The notch is considered an inclined plane, with a normal force perpendicular to the inclined plane. for

[0065] The lateral pull-out force of the yarn is:

[0066]

[0067] The resistance to yarn pull-out is:

[0068]

[0069] The critical equilibrium condition for yarn unwinding is ( ):

[0070]

[0071] If the angle of pulling the yarn backward Smaller than this The yarn will be locked in the groove and cannot be pulled out no matter how much tension is applied (unless the yarn breaks or the needle is damaged). The yarn will only pop out when the angle changes (caused by the movement of the needle) beyond this value.

[0072] 3. Quantification of tension fluctuations caused by yarn slippage ( )

[0073] The yarn's elongation while inside the groove is greater than its elongation after exiting. At the critical point where the yarn exits from the bottom of the groove, the instantaneous relaxation caused by the bounce results in a sudden change in tension, releasing elastic potential energy and creating tension fluctuations. (Elongation difference) Approximately equal to the difference between the arc length and chord length of the groove, or simplified to the depth. Functions: , The curvature of the yarn covering the knitting needle.

[0074] Calculate the tension pulse according to Hooke's Law: in For yarn modulus, This refers to the length of the free yarn segment.

[0075] The elastic energy released by the yarn at the moment it springs out is equal to the work done to overcome the resistance force. (Tension fluctuation peak) With resistance Proportional: ,because Follow The more rapidly the groove increases, the deeper it becomes, the more difficult it is to pop out, the greater the energy accumulated, and the more intense the tension impact during the bounce, resulting in a significant decrease in the quality of the woven fabric, which means that the value of the knitting needle has decreased.

[0076] 4. Calculate the quantitative index of yarn scratch damage.

[0077] The yarn surface damage index is defined as follows:

[0078]

[0079] Frictional work represents the energy consumed when the yarn slides through the groove. It is a yarn cohesion energy index, representing the ability of yarn fibers to resist separation; This represents the scraping efficiency factor, which is related to the sharpness of the groove edge. Calculated.

[0080] 5. Calculate the damage index of the needle hook structure.

[0081] Calculate the section modulus attenuation factor:

[0082]

[0083] in, The diameter is the diameter of the hook's cross-section, which is approximately circular or elliptical.

[0084] Calculate the stress concentration factor at the bottom of the wear groove:

[0085]

[0086] The fatigue index of the knitting needle hook structure is defined as follows:

[0087]

[0088] λ is the notch sensitivity factor, which depends on the heat treatment process of the needle material. For high carbon steel, the empirical value is 2.0 to 3.0.

[0089] 6. Establish a quantitative evaluation standard for needle hook wear.

[0090] Define the comprehensive performance index

[0091]

[0092] in It is a safety gating function used to determine whether the knitting needles possess basic "serviceability".

[0093]

[0094] and The set structural safety threshold and yarn damage threshold.

[0095] Calculate the mass decay function

[0096]

[0097] Based on the calculated NOPI value, the system outputs the final decision instruction, and the evaluation method is shown in Table 1:

[0098] Table 1

[0099] NOPI score range Level Name Physical state description System Execution Instructions 0 Failure Contact with fabric damage or broken needle thread Immediately stop the machine and sound an alarm; lock the needle size. 1 - 59 Unqualified Safe, but the fabric will inevitably have horizontal stripes. Planned shutdown for replacement, marked as defective area. 60 - 79 warn Slight hidden streaks are present, suitable for coarse yarns. Reduced speed operation or only for low-end fabrics 80 - 100 normal The weaving process is stable and there is no quality risk. Keep running

[0100] Example

[0101] like Figure 1As shown, this invention is used to quantitatively evaluate the wear degree of a knitting needle corresponding to a specific yarn. This embodiment is implemented through five steps: (S1) parameter initialization and measurement → (S2) tension fluctuation rate calculation → (S3) yarn scratch damage calculation → (S4) needle hook structure damage calculation → (S5) needle hook wear degree assessment.

[0102] Step S1: System parameter initialization and measurement, determining important parameters such as yarn radius, sinker advance distance, and yarn bending depth, as detailed below:

[0103] Circular knitting machine parameters:

[0104] Serial number: E28, which means 28 pins per inch.

[0105] Weaving speed: 25 RPM.

[0106] Unwinding cam angle (determines the tension angle α): Set at the instant of unwinding, the equivalent angle between the yarn and the needle hook plane. .

[0107] Knitting needle parameters (standard sample):

[0108] needle hook cross-sectional radius : 0.4 mm.

[0109] yarn bending depth 10cm

[0110] Settling plate advance distance 10cm

[0111] Knitting safety threshold:

[0112] The structural safety threshold is set at 0.3. Below this value, the needle hook may fracture due to fatigue at any time.

[0113] The yarn damage threshold is set at 2.5mg. If it exceeds this value, a large amount of lint will be generated, and the machine must be stopped.

[0114] The tension fluctuation threshold is set to 10. Tension fluctuations exceeding 10 times will cause serious damage to the fabric quality.

[0115] Yarn parameters:

[0116] Raw material: 32S combed cotton yarn.

[0117] The yarn diameter is 0.18 m, and the effective radius r = 0.09 mm.

[0118] Basic yarn feeding tension :5 cN.

[0119] Fracture strength : 180 cN.

[0120] coefficient of friction : 0.3 (cotton-steel dynamic friction).

[0121] Calculate the maximum tilt angle of the yarn during the loop formation process

[0122] like Figure 2 As shown, the geometric data of the current knitting needle hook groove is obtained through machine vision inspection system or microscopic measurement:

[0123] The selected measurement object was the Nth needle of the needle cylinder, and the wear depth h was measured to be 0.027 mm.

[0124] To calculate the mechanical resistance caused by wear, first calculate the geometric locking angle (climbing angle) β:

[0125]

[0126] Then calculate the overall drag angle. :

[0127]

[0128] Calculate the critical tension required for the yarn to emerge from the groove. :

[0129] Assuming the radial pressure of the yarn on the needle hook .

[0130]

[0131] Substitute the values:

[0132]

[0133] Step S2: Analyze the yarn tension fluctuations and calculate the tension abrupt changes caused by wear.

[0134] Theoretical steady tension:

[0135] Actual peak tension:

[0136] Tension fluctuation ratio

[0137] times

[0138] Step S3: Calculate the yarn damage index

[0139] For 32S cotton yarn The empirical value is 0.5 mJ / mg, and the calculated frictional resistance is:

[0140]

[0141] The frictional work is calculated as follows:

[0142]

[0143] Calculate the scraping efficiency factor:

[0144]

[0145] Calculate the damage index:

[0146]

[0147] Step S4: Calculate the damage amount of the needle hook structure

[0148]

[0149] Step S5: Assessment of hook wear

[0150] Calculate the overall performance index:

[0151]

[0152] The determination result of this embodiment:

[0153] According to the NOPI classification, the knitting needle's health registration is unqualified, and the machine must be stopped and replaced.

[0154] The above description provides examples of the preferred embodiments of the present invention. Parts not detailed herein are common knowledge to those skilled in the art. The scope of protection of the present invention is determined by the claims. Any equivalent modifications based on the technical teachings of the present invention are also within the scope of protection of the present invention.

Claims

1. A method for quantitatively evaluating needle hook scratch damage, characterized in that, Includes the following steps: Step 1: Collect loom parameters and yarn parameters. Loom parameters include the sinker advance distance. and yarn bending depth Yarn parameters include yarn radius The static friction coefficient between yarn and knitting needles Yarn pull-back angle and side deflection angle and yarn tension ; Obtain the real-time wear depth at the groove of the knitting needle hook. h ; Step 2: Calculate the climbing angle β and the combined resistance angle. The critical tension required for the yarn to escape from the groove ; Step 3: Analyze the yarn tension fluctuation and calculate the tension fluctuation ratio. ; Step 4: Calculate the yarn damage index Damage to the hook structure ; Step 5: Calculate the overall performance index: ； in It is a safety gating function used to determine whether the knitting needle has basic "serviceability": ； and The preset structural safety threshold and yarn damage threshold; Mass decay function: ； This is the preset maximum tension fluctuation ratio; Step 6: Based on the comprehensive performance index The value is used to determine the wear level of the loom, and the wear level is used to determine whether the machine needs to be stopped.

2. The method for quantitative evaluation of needle hook scratch damage according to claim 1, characterized in that, In step 2, the climbing angle β and the combined resistance angle The critical tension required for the yarn to escape from the groove The calculation formula is: ； ； 。 3. The method for quantitative evaluation of needle hook scratch damage according to claim 1, characterized in that, yarn tension in step 1 Obtain it through one of the following two methods: Method 1: Real-time data collection of yarn tension at various times within a time period and calculation of the average value as the yarn tension. ; Method 2: Directly collect the fixed yarn tension value set on the loom as the yarn tension. .

4. The method for quantitative evaluation of needle hook scratch damage according to claim 1, characterized in that, In step 4, the yarn damage index The calculation formula is: ； in, Frictional work represents the energy consumed when the yarn slides through the groove. It is a yarn cohesion energy index, representing the ability of yarn fibers to resist separation; This represents the scraping efficiency factor, which is related to the sharpness of the groove edge. Calculated.

5. The method for quantitative evaluation of needle hook scratch damage according to claim 1, characterized in that, In step 4, the damage amount of the needle hook structure The calculation formula is: ； in, λ is the diameter of the needle hook cross-section, which is approximately circular or elliptical, and λ is the notch sensitivity coefficient, which is related to the heat treatment process of the needle material.

6. A quantitative evaluation system for needle hook scratch damage, characterized in that, The method described in any one of claims 1-5 was adopted.

7. A computer-readable storage medium, characterized in that, It stores a program that can implement the method according to any one of claims 1-5.

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