Feeding Systems

1. The presser foot, 2. The feed dog, 3. Thumbscrew for removing the presser foot

Material feed means the controlled movement of the material being sewn from one stitch position to the next. Moving the material through the sewing pint is what converts a series of stitches into seam. The fabric material can be moved in any horizontal direction; in most cases it is only forwards or backwards. Usually the fabric is moved just after the needle point is raised clear of the surface and stops just at is about to re-enter, therefore accurate control of plies of material being sewn is essential for satisfactory stitching, affecting appearance, pucker and seam strength.

Material feed is achieved by the feed dog which contains several rows of serrated teeth. The feed dog is moved upwards and forwards through slits in the throat plate to engage with the underside of material being sewn and to advance it by a distance of one stitch length. Contact between feed dog and material is controlled by the spring loaded presser foot. The feed dog is then lowered and move back to its starting position.

Various types of feed dogs, presser foot and throat plate are used according to the type of material being sewn and the particular sewing operation. Feed dogs can have different shapes and types of teeth.

Compound Feed is a combination of synchronized drop feed and needle feed. Feeding occurs while the needle is still in the material by combined motion of needle bar and the feed dog. Since needle holds the plies of material in registration of feeding this reduces pucker and slippage between the plies of material. Used mainly for edge stitching, checks and stripes.

Variable Top and Bottom Feed (before the needle) is a feed mechanism where the feeding foot similar to presser foot is provided with two rows of teeth and acts alongside the presser foot. The strokes of the feeding foot and the feed dog can be adjusted independently.

Variable Top and Bottom Feed (after the needle) – mechanism is when the feeding foot operates behind the needle to deliver especially smooth seams.

Alternating Compound Feed – This system involves a combination of three types of feeding; feed dog, needle feed and feeding foot. In this process fabric cannot be gathered. This application is used when sewing multiple plies and sewing bulky seams in heavy fabrics.

Puller/Roller Feed is an auxiliary feed using a wheel or roller positioned behind normal feed mechanism. This roller operates either continuously or intermittently. This is suitable for long straight seams without causing puckering.

Reverse Feed is the feed used in majority of Lockstitches to move the fabric material away from need towards sewer for bar tacking. Chain stitch machines rarely have this bar tacking feed mechanism.

Feed systems usually work on the underside of the material but can also operate above or from both sides at the same time, depending on the need to avoid particular problem in sewing.

Drop Feed is basic material feed system where the feed  alternately engages and disengages with the underside of material and is suitable for general sewing operations on any material which has no particular sewing problems.

Differential Drop Feed is a differential feed which utilizes two independently driven feed dogs. The stroke of each feed dog can be adjusted separately. If the stroke of front feed dog is greater than the fabric may stretched to provide a more stretchable seam.