Top and bottom compound feed lockstitch sewing machine is a specialized machine that is used in the garment industry to create precise and high-quality stitching on thick fabrics. Its biggest feature is the use of a large rotary shuttle hook and the configuration of an up and down comprehensive feeding mechanism and an alternating lifting mechanism for the pressure foot. Due to its strong sewing ability, good layer sewing performance, and stable reverse stitching, it is widely used in medium thick material products such as leather and canvas. Although the machine is designed to be reliable and durable, it is still subject to wear and tear, which can lead to various faults as below.
(1) Needle position
When the needle descends to the lowest point, the center of the needle hole should be at the same position as the inner circumference of the rotary shuttle. If the sewing material is thick, the center of the needle hole can be appropriately lowered by about 0.5mm.
(2) The synchronization of the needle and the rotary shuttle
Standard synchronization relationship: After the needle moves downwards to the lowest position and then rises upwards by 2.5mm, the hook tip of the rotary hook should be consistent with the centerline of the needle. At this position, the hook tip of the rotary hook should be about 1.2-1.5mm higher than the upper edge of the needle hole. In addition, the gap between the bottom of the needle notch and the hook tip of the rotary shuttle should be between 0 and 0.05mm.
(3) Location of feeding teeth
① The standard position is to adjust the feeding amount to the maximum. When the front end of the feeding tooth is close to the front side of the needle plate groove, the plane gap between the front end of the feeding tooth and the front side of the needle plate groove is 1.5mm. After adjusting, adjust the feeding amount to the desired position.
② When the feeding teeth move to the highest point, they should be 0.8-1.2mm higher than the needle plate plane. When sewing thicker materials, they can be appropriately adjusted by about 1.5mm. The feeding teeth are generally in a horizontal position and should be adjusted when sewing conditions require tilting.
(4) Feed synchronization
The standard position is that when the feeding tooth moves to be flush with the needle plate surface, the machine needle tip should also be exactly flush with the needle plate surface. If the sewing material is thin, the needle tip of the machine can be slightly lower than the flat surface of the needle plate by about 0.5mm.
(5) Adjustment of the feeding mechanism
In general, the upper feeding should be synchronized with the lower feeding, but in actual sewing, special situations are often encountered. Adjustments should be made according to the different friction coefficients of various sewing materials and the sewing process requirements, that is, the center distance between the swing presser foot slider of the upper feeding mechanism and the swing presser foot shaft should be adjusted. Increasing the center distance increases the amount of upward feeding; Reduce the center distance and decrease the amount of upward feeding. In addition, in practical operation, the upper feeding time can be adjusted to be slightly slower than the lower feeding time according to special requirements.
In conclusion, the top and bottom compound feed lockstitch sewing machine is an indispensable tool in the garment industry. However, like any other machine, it is subject to wear and tear and can develop various faults. By following the adjustment methods outlined in this article, you can easily fix these faults and keep your machine in top condition. At the same time, if you have questions for other industrial sewing machine or want to purchase a long arm top and bottom feed sewing machine, welcome to KINGMAX.