Fabric feed systems

Fabric feed systems used for stitching sportswear... 

The automated spreading process is performed on special tables. The main parts of a spreading machine are a fabric spreader tmck, a fabric feed system, an automatic cutting device, an end-catchCT, an operator stand panel, an encoder system, and a control panel. 

The end section of the fabric on the body of the truck and the attached cutting device are lifted after each automatically laid ply. These are driven by the sensor of a lifting device to avoid contact between preceding spreads and newly laid plies. During the spreading process, the fabric feed system automatically adjusts the feeding speed of the material and measure its length. 

The previous topics have been addressed to the review of the occurrence of seam pucker and other surface distortions, and defects caused by needles and fabric feeding systems. The present section wUl review the problems related to stitch formation stitch imbalance, stitch distortion and skipped stitches. 

Chemical activities in the field of mass screening are often related to combinatorial chemistry [51,52]. One major goal, especially in the field of solid phase chemistry involving polymers like DNA or peptides, aims at the increase in the number of compounds per reactor volume and time. Commercially available microtiter plates are established as reactors in this case whereby robotic feed systems fit perfectly to their dimensions. A drastic reduction of reaction volume and increase in number of reaction vessels ( wells ) leads to the so-called nanotiter plates (e.g. with 3456 wells). Microfabrication methods such as the LIGA process are ideal means for the cost effective fabrication of nano-titer plates in polymeric materials by embossing or injection molding techniques so that inexpensive one-way tools are realized. 

Figure 11.13 X-feed system, (a) Central feed dog (gold colour) is up and transporting the fabric while needle is down, (b) The side feed dog (sky blue colour) is up and transporting the material while needle is up.

Differential fabric stretch, or feed pucker (Amann Group, n.d.-b), occurs when different fabric plies being sewn are fed in dissimilar conditions by the material feeding system of the sewing machine. This causes the individual plies to be stretched... 

This kind of pucker is often observed when sewing two or more plies of fabric on machines with a drop-feed system. Drop-feed is the most common and simple feeding system, being composed of a presser-foot, a throat plate and a feed-dog (Figure 12.3). 

The feed-dog has an approximately elliptical movement. After the withdrawal of the needle from the fabrics, the feed-dog rises above the throat plate and presses the fabrics against the underside of the presser-foot, whilst pushing it forward to a predetermined distance, which defines the stitch length. This system has the drawback of not being able to provide the same feeding action on the upper and lower fabric plies. Only the lower ply has direct contact with the feed-dog, the mechanical element promoting fabric motion, while the upper ply has the tendency to get stretched because of the friction exerted on it by the presser-foot. Conversely, the problem of ply-shift, described later in this chapter, is also caused by the principle of the drop-feed system. 

The most immediate upgrade is the change to a needle-feed system, in which drop-feed is combined with the movement of the needle in the seam direction. The needle-feed system avoids ply-shift and thus reduces the effect of feed pucker, but it may be more prone to tension pucker. This is due to a major difference between the needle and the drop-feed systems Feeding of the material occurs when the needle is in the material in needle-feed machines, whilst it occurs when the needle is outside the fabric in drop-feed systems. Stitch tightening occurs when the needle is outside of the fabric. This means that in a needle-feed machine, stitch tightening occurs when the feed-dog is under the stitch plate and thus not supporting the fabric from the lower side, leaving the fabric more loose and subject to tension pucker. 

One of the more recent types of compound feeding system is the X-feed system by Xi an Typical Industry Co., Ltd. (Xi an, China). In this system, the drop-feed is combined with the needle-feed, but unlike a normal feed-dog, the feed-dog in this system is split into two parts, with each being active in about half of the sewing cycle. The fabric is thus supported between the presser-foot and feed-dog in a more even way throughout the stitch cycle. Jana and Khana (2014) studied this new feeding system and in their experiments found that this system reduced ply slippage and produced flatter seams than the traditional drop-feed. More details of X-feed is described in Chapter 11. 

Feeding system (differential fabric stretch or feed pucker)... 

Inadequate use of feeding systems (producing non-uniform fabric feeding action) Empirical setting of the sewing machine feeding system... 

Proper adjustment of the stitch length, sewing threads and needles, according to the type of fabric (structural jamming appears mainly in dense, lightweight fabrics) Correct adjustment of thread tensions Proper selection of the feeding system (on knits and stretch wovens, use differential feed and minimum of pressure-foot pressure)... 

Poor fabric feeding (loopers, feeding system and speeds)... 

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