Breaking thread is the most common fault in sewing. Unqualified sewing quality, inappropriate machine adjustment, sharp edges in threaded parts, problems in operation methods, inadequate cooling of needles, etc., will lead to wire breakage. When you are sewing uneven thickness products with lock seam machine
and meeting the problem of breaking thread, in addition to considering and analyzing the above reasons one by one, attention should also be paid to the broken thread caused by two hooks. In the sewing equipment, the transmission ratio of the upper shaft and the spindle of the lock seam machine is 1:2 because of the need of distributing the action cycle in the design. The upper axle rotates one week and the spindle rotates two weeks.
If the spindle hooks the surface thread every time, which means, once the machine needles the material and twice the spindle hooks, it will conflict with the drawing and placing of the surface thread, resulting in the phenomenon that the sewing line is broken. This may occur when you are sewing uneven thickness seams. The reason has to start with the formation process of lock-type trace.
Formation of Lock-type Track
Lock stitches are made up of interwoven surface and bottom stitches in sewing materials. When the sewing machine is working, the needle lead surface thread passes through the sewing material and rises up after reaching the lower limit position. Because of the friction between the stitching material and the stitching thread, the surface thread can not be lifted synchronously by random needle, but remains under the stitching material and expanded to both sides of the machine needle under the action of elasticity to form a ring. Then, the spindle tip reaches the machine needle in the process of motion, passes through the surface loop, and expands the hooked loop in the process of continuous rotation. When it reaches its own radius, it "jumps" over the enlarged loop like a rope skip. The next step is to take the pick-up rod off and feed dog so that these movements have enough time. The shuttle still rotates at the original speed for a week, but no longer hooks, only idles for a circle. Due to the closing effect of the take-up rod, the area loop which is enlarged and "leaped" by the shuttle quickly shrinks until the bottom line drawn from the center of the shuttle is pulled into the sewing material to form an interweaving. When the needle reaches the upper limit position and goes down again, the sewing machine starts again, and repeats the above-mentioned action process, thus forming continuous and regular lock stitches on the sewing material.
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