The biggest difference between reverse stitching and positive seam is that the stitches are different. The stitch stitches are standard lock stitches that are wound up and down like a rope. The reverse stitch still doesn't know its official name, and it is called the buckle stitch for the time being, because the upper thread is tied around the lower line and it is like the first dead knot of the lace system. It is obvious that the buckle has higher requirements on the thread, and the sewing thread is required to have higher strength, more uniform strip, and smoother and softer characteristics.
The second major difference between the reverse stitch and the positive seam is that the timing of the cooperation between the needle bar and the lifting tooth eccentricity is different. During the reverse sewing, it is possible to catch up with the needle puncturing cloth during the moment of pressing and lifting the back-stitching wrench. If the feeding tooth is still exposed on the surface of the needle plate at this time, the needle will oscillate with the sewing material instantaneously. This is one of the reasons for the broken stitch of the reverse stitch. In order to avoid this, it is necessary to adjust the eccentricity of the lifting teeth according to the requirements of the reverse stitching, so that the needle does not swing with the moment when the sewing material is pressed and lifted. This adjustment avoids the problem of the needle swinging instantaneously, but it raises another problem and loves to set it out.
The third major difference between the reverse seam and the positive seam is that the friction resistance of the rotary hook is required to be smaller and smoother, so that the thread take-up rod can overcome the frictional resistance when the rotary hook is running with a minimum force when tightening the upper thread. Only in this way can the pressure of the pressure reducer be minimized without going out of the sleeve. Because the friction resistance here is the force of the shuttle bowl (or shuttle frame, shuttle) close to the hook of the hook, the greater the force, the tighter the compression spring on the pressure plate, and the greater the chance of wire breakage.
The fourth major difference between the reverse seam and the positive seam is that the seam is not the same as the needle, especially below the needle hole. The friction in both directions requires that the needle's smoothness is omnidirectional and no burrs are allowed.
The four major differences between the reverse seam and the positive seam determine the difficulty of the reverse stitching operation. The objective conditions in actual production determine whether the reverse stitching can proceed smoothly. In addition to the maintenance personnel to adjust and repair the machine within the limits of their ability, the proper reduction of the reverse sewing speed in the case of using high-quality needles and sewing threads is the most effective way to save money. Why do you say this? Because the speed is reduced, the requirements for the needle, the sewing thread and the hook are reduced accordingly. It is possible to reduce the speed at a high speed, because the maintenance personnel can only adjust the maintenance machine within the limits of the force, and the maintenance personnel cannot improve the quality of the suture. There is no way for the maintenance personnel to use the sewing thread without the use of the reverse seam. In addition, a particularly good rotary hook has a good hook for the reverse sewing speed of the same speed as the positive seam speed. The hook that can withstand such continuous work tests may be tens of miles based on experience. Most factories will give up this road. If it is easy to use a high-quality needle, it is also difficult to use high-quality sewing thread, because the money immediately goes out with the sewing thread, and it is not good to buy a good line. Only the easiest way to achieve the goal without having to spend money and to achieve the desired reduction in the speed of the backlash is that it is the best way to adjust the machine.
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