Comparable problem situations in the chain stitch and lock stitch sectors have made similar suggested solutions possible. Ever since the introduction of LPC (loop position control) geometry in the 02/2010 edition of the Online Newsletter, the LPC range has been extended to include the chain stitch sector. At the ITMA in Barcelona, Groz-Beckert is presenting the solutions. LPC technology will also be demonstrated at the CISMA (Hall E4, Stand C29) in Shanghai, from September 27-30, 2011.
If very dense or hard materials are sewn together in several layers, the thread is crushed between the fabric and the edge of the longitudinal groove during the downward stroke of the needle. Especially when thick multifilament sewing threads are processed, the thread tends to be twisted tighter above the fabric and get caught in the longitudinal groove of the sewing needle. Above the fabric the thread is then usually twisted more tightly, and below the throat plate the thread is partially untwisted. This twist displacement can have negative effects on loop formation.
Through improved geometry of the shank and the longitudinal groove on the LPC lockstitch needle, Groz-Beckert has achieved far better thread protection and less load on the thread as it runs over the edges of the longitudinal groove.
The result is gentler treatment of the thread. Furthermore, benefits are achieved even with critical applications. On the one hand, stable loop formation is made possible, while on the other, skipped stitches and thread breakage caused by poor loop formation can be reduced.
On 2- to 4-needle machines the needle which is closest to the gripper forms the smallest needle thread loop. The reason for this is the short loop stroke. Machines adjusted to have a highly tensioned thread, or which process textured sewing threads, have a tendency to make skipped stitches. In high-speed photos it can be clearly seen that the needle thread loop is too small or badly formed.
The LPC chain stitch needle also has the new shank and groove geometry - as well as a large eye in relation to the needle thickness. The processing of textured sewing threads is therefore improved. In combination with correct machine adjustment, LPC chain stitch needles make a well-formed, strong loop, even when a high stitch tension is required and with the use of textured yarns.
Whether it's lock stitch or chain stitch, Groz-Beckert sewing-machine needles with LPC geometry are impressive in every respect. They all stand for:
Come to the ITMA Barcelona and CISMA trade fairs and find out about your benefits in detail! If you have any queries or suggestions at this point, please feel free to contact your partners.