Progress in NC Stitching Machines: Improving Shoe Seam Appearance

In recent years NC controlled lock‐stitch sewing machines operating on shoe upper sub‐assemblies held in flat pallets have become well‐established in shoemaking businesses. However, a major problem for manufacturers of high‐quality footwear is that such machines are subject to malformation of the lockstitch when the pallet moves in certain directions with respect to the sewing head. The stitch malformation, known as half‐hitching, results in seams which have an inconsistent and unsightly appearance. Examines the reasons for half‐hitching and strategies for its prevention. One approach involves rotating the stitching head about a vertical axis so that the direction of sewing is always maintained at a tangent to the seam. Systems such as this have been proposed in the past but have been prohibitively complicated and cumbersome. Introduces a stitching machine concept which enables a much simpler demonstration rotating head stitching machine to be built. It is expected that industrially‐developed units using the principle illustrated will find widespread use in the shoemaking industry. They will be relevant not only in conventional pallet loaded NC stitching machines, but also in a new generation of palletless machines.