The definition and classification of the stop marks
During the knitting process of the Circular Knitting Machine, when the machine starts and stops, it will generate a horizontal trace on the cloth surface, which is called the so-called stop mark. The phenomenon of the stop mark is particularly evident on single-sided spandex fabrics. From the fabric appearance point of view, there are two types of stop marks. The first category: the traces are very fine, and the boundaries with the normal fabric are clear, and the coils at the mark of the stop are clearly tightened or skewed; the second category: the traces are wide, the boundary with the normal fabric is blurred, and the traces of the rest are The density of the fabric is greater than that of the normal part, and the coil is not tightened or skewed.
Analysis of Causes of Stop Marks
The first type of stop marks
a. It is related to the excessive clearance of the machine's transmission part and the looseness of the big Gear.
Because the transmission gap is too large, when the machine starts and brakes, the yarn feeding device is not synchronized with the rotation of the cylinder, or the Needle Cylinder drifts, which causes the yarn tension to change drastically, and the size and shape of the coil change accordingly to form a stop mark. In severe cases, holes, missing needles, broken yarns and other defects can also be caused.
b. It is related to the loose tension of the accumulator belt or the accumulation of fly in the speed disk.
The yarn tension of the yarn storage device is loose or the flywheel accumulates in the governor disc. The friction coefficient between the belt and the slider in the yarn feed control plate is reduced (the friction force is reduced), causing the belt to slip when the machine is started, and the yarn feeding speed is instantaneous. Smaller, and when the machine is running at a constant speed, belt slippage disappears, forming a stop mark.
c. related to severe triangulation
When the triangle, especially the settlement triangle, wears out, the surface of the needle track appears obvious grooves. When the machine is started from a static state, the knitting needles and the sinkers accelerate along the cam needle. Due to the wear of the cam needles, the knitting needles and the sinkers are violently beaten. As a result, the knitting process of the yarn becomes extremely unstable, and the coil becomes uneven. As the machine gradually moves into a constant speed, these jumps become smaller. Forming a stop mark.
d. The double-sided machine generates such kind of stop marks, which is related to the unsynchronized needle plate and lower needle cylinder
The non-synchronization of the needle plate on the double-sided machine and the lower cylinder will also cause a stop mark, but the general reaction is not obvious. Because the coil of the double-sided fabric enters the finishing process after completing the detachment, it mainly depends on the pulling force of the fabric looms. During the sorting process, the dial coil and the needle coil will transfer to each other under the action of the pulling force. This eliminates the non-uniformity and skewness of the coil formed during the partial start-up. Therefore, on the double-sided fabric, the phenomenon of the stop mark is not as obvious as reflected on the single-sided machine.
e. Towel fabrics produce such kind of stop marks, which are related to the installation accuracy of the settlement triangle
Towel-like fabrics produce such strike marks that are mainly reflected on the loop surface. When the loop yarn is bent, the yarn rides on the nose of the Sinker. At this time, the sinker should be in a relatively stationary state relative to the Knitting Needle to ensure the stability of the looped yarn. However, in actual use, due to the wide settlement triangle, deviations in its centripetality during installation may cause relative movement between the sinker and the needle (instead of being relatively stationary) when the loop yarn is bent. The terry yarn is under tension. Under the effect of friction, the terry yarn will shift with the relative movement of the sinker and the knitting needle. This offset is obviously different between the machine acceleration and the constant speed operation. This produced a stop mark (see Figure 1a).
f. Towel type fabrics produce such kind of stop marks, related to the fit between the sinker and the needle's motion path
Under normal circumstances, when the bending ends, the sinker begins to advance towards the center of the needle cylinder. To ensure the smooth progress of the knitting needle withdrawal process, the knitting needle should have a lifting motion to relax the settlement before the movement of the sinker. Pieces of terry yarn on the nose.
When the looped yarn is finished, the sinker begins to advance towards the center of the needle cylinder. Before entering the withdrawal phase, the knitting needle is not lifted in time to loosen the loop yarn, so that the loop yarn is still under tension. When the machine is running at a constant speed, the tensioned terry yarn will be compensated by the terry yarn that is lifted by the adjacent knitting needles. When the machine starts up at an accelerated speed, the transfer process is too late to produce a stop mark (see Figure 1b).
![QQ screenshot 20150827144522]()
The second type of stop marks
These types of stop marks are generally common on single-sided spandex fabrics. There are two types of causes for analysis.
a. The coiling operation of the coiler lags behind the operation of the machine
When the machine is started and run, the winder winds up and winds up, which results in a smaller cloth tension and an increase in the fabric density at the beginning of the machine movement. When the machine gradually enters a constant speed operation, the take-up speed of the cloth winding machine gradually becomes uniform, and the cloth tension returns to normal, resulting in a stop mark. Since this process is not completed in an instant, the track marks are wide and the boundaries are blurred.
b. Related to the width of the needle path at the lowest point of the knitting triangle presser
Because when designing the triangle, it tends to emphasize the versatility of the different machine triangles, so that the width of the needle groove at the lowest point of the pressure needle exceeds the needle width at the lowest point of the pressure needle, resulting in an outage trace. Specific analysis is as follows:
At the needle point of the triangular curve of the knitting needle, the knitting needle under the action of the triangular needle path suddenly turns from upward to upward. Due to the thickness of the pinhole, the width of the cam track here varies according to the thickness of the pinhole. However, for the convenience of the user, the 18 to 28-pin/25.4-mm triangle is generally designed as a general-purpose design. The 18-pin/25.4-mm machine has a pin thickness of 0.64 mm, and 28 pins/25.4 mm. The needle thickness of the machine is generally 0.41 mm or even thinner. In order to be versatile, a 0.64 mm thick needle is generally used as a design basis. The designed triangular pressure pin part is shown in Figure 2a.
However, when this cam is used on a 28-pin/25.4 mm (0.41 mm-thick needle) machine, the width of the needle track at the pin point becomes too wide. When the machine is running at a low speed, due to the tension of the old coil, the knitting needle is pulled up. The movement of the needle in the needle path is along the upper edge of the needle path, as shown by the dashed line in Figure 2b. When the machine is running at a high speed, the movement path of the needle in the needle track will change due to inertia and the rotation speed of the cylinder, as shown in Figure 2c. It is not difficult to see from the figure that the bending amount of the machine at high speed is obviously lower than that at low speed (ie, the yarn tension of the machine at high speed is higher than that at low speed). Therefore, during the process of the machine moving from rest to acceleration to normal speed, the trajectory of the knitting needle changes, the amount of bending yarn changes, and the density of the fabric also changes. This change changes with the speed of the machine. The formation of the stop marks is wider and the boundaries with the normal fabric are blurred.
It can be seen that the large gap between the needle point and the needle groove at the point where the needle is pressed is the main reason for this kind of stop mark. However, if there is no gap, the machine will not operate normally. Minor changes in the knitting needles caused by slight vibrations can cause pinching, so it is necessary to maintain a certain clearance, but not too large. In theory, even small gaps can cause minor stop marks, but the response on the cloth surface is minimal.
![QQ screenshot 20150827144530]()
The solution to the stop mark
The first type of stop marks First of all, always check the wear of the parts, the wear of the bearing parts, the wear and aging of the belt, check the looseness of the big gear every six months (maximum not more than one year), and check the level of the machine once a year. Replace wear and aging parts in time. The amount of looseness of the big gear should be controlled within 0.05 mm. If it is beyond this range, it should be adjusted in time. For suspended steel wire structures, gaskets should be removed and shrunk in time; for superposed wire needle paths and wear-resistant film needles, machining processes must be promptly repaired.
When adjusting the machine table, the towel machine should pay special attention to the adjustment of the relative positions of the settlement triangle and the knitting needle triangle, and ensure the position shown by the dotted line in FIG. 1b. In addition, when adjusting the settlement triangle, it is necessary not only to ensure that the position of entry and exit is the same, but also to ensure the centripetality of each triangle so as to ensure that the needle and the sinker are in a relatively stationary state during bending.
The second type of stop marks The key point is to make clear requirements when purchasing the machine. Do not unilaterally pursue the versatility of the triangle. Machines with excessive versatility tend to miss one another. If the machine is used, it is found that the yarn tension at the low speed operation differs from the high speed operation by more than 5 g. When it is necessary, contact the equipment manufacturer in time to replace the triangle that matches the machine number.
The above-discussed stop marks are the marks of the stop marks reflected on the blank cloth. After dyeing and finishing, it will generally fade or even remove. However, the improvement effect of the first type of trace dyeing after finishing is not obvious.
