How Woven and Knitted Fabrics Are Built
Fabric performance depends on greige interlacing geometry, wet processing relaxation, and multi-mill supply chain lead times.
Latch Needles
Mechanical Component
Mechanical component used in knitting machines that employs a swinging latch to close the needle hook and cast off a previous stitch while forming a new loop. Use of latch needles is the standard for most circular and flat knitting machines due to their ability to operate without an external pressing mechanism. This needle consists of a stem, a hook, a latch and a butt that interacts with the cam track to control the vertical movement.
The latch is pivoted on a small pin and moves freely between the open and closed positions as the yarn and the previous loop pass over it. The boundary of this technology is the speed of the machine, as the physical swinging of the latch can become a limiting factor in ultra-high-speed operations.
Mechanical Cycle
Formation of a stitch begins with the needle in the clearing position where the old loop has pushed the latch open and is resting on the stem. As the needle moves upward, the latch remains open, allowing the hook to receive the new yarn from the feeder. When the needle starts its downward stroke, the old loop slides up the stem and strikes the underside of the latch, forcing it to flip over and close the hook.
This creates a smooth surface for the old loop to slide over the closed hook and off the needle, a process known as knocking over. The new yarn is then pulled through the old loop to form the next stitch in the column. This self-acting mechanism simplifies the design of the knitting machine and allows for the production of complex structures with multiple yarn types.
However, the friction between the latch and the pin can cause wear over time, leading to loose latches that fail to close properly. This results in dropped stitches or fabric defects that are difficult to repair. Maintenance teams must regularly inspect the needles for damaged latches or bent hooks to ensure consistent fabric quality.
Production Efficiency
Versatility is the primary reason for the dominance of this needle type in the apparel industry, as it can handle a wide range of yarn counts and fibers. Latch needles allow for the creation of intricate patterns, such as cables and pointelle, by transferring loops between different needle beds. This flexibility enables the factory to produce a variety of garment styles on the same machine with only minor adjustments to the cams.
The rugged design also makes them less prone to breakage than other needle types when working with heavy or irregular yarns.
Maintenance Boundary
Replacement of these components is a routine part of mill operations, as the mechanical stress of millions of cycles eventually causes fatigue. A broken latch needle can cause a vertical line of holes in the fabric, which is a major quality issue. Automated needle detectors are often installed on the machines to stop the motor the moment a failure occurs.
Careful needle selection ensures the gauge of the needle matches the yarn and the machine gauge.