Sewing needles types

An approved fire extinguisher [the dry chemical (bicarbonate) type is preferred, but the CO2 type is satisfactory] should be mounted near at least one exit and refilled after every use, no matter how small. The laboratory should be arranged so as to provide two or more avenues of escape from any experimental setup in case of emergency. A first-aid kit containing Band-Aids, sterile gauze, adhesive tape, petroleum jelly, a mild antiseptic, sterile cotton swabs, tweezers, a set of sewing needles, a packet of razor blades, and a quick-reference first-aid manual will provide adequately for most minor emergencies. 

Sewing needles come in a wide range of point types that are used for sewing many different types and properties of material. Indeed, you could write a book on the sewing needle alone. 

Table 11.4 Sewing needle cloth point types... 

The most important aspect of needle design is the needle point because it has to penetrate the fabric without causing any damage to the material. It is also the most diverse part of the needle due to the many different types of points used. Needle points are designed for sewing on many different fabric types and seams. An example of needle point designs can be seen in Figure 6.21. 

Each number denotes a sequence of stitches within that class. For example, aU lockstitch formations are contained within the class of 300. Therefore, stitch types 301, 302, 303 and so on are all single-needle lockstitches. The primary stitches for sewing sportswear fabrics are described as follows. 

Seam types used for woven fabrics include superimposed seams and double-lapped seams, especially when a high degree of strength is required, for example, in judo suits. Hemmed seams are also used on legs, and a lockstitch is used on areas that include labels and pockets. Sewing threads would be mainly staple core-spun polyester. Round-point needles are used for stitching these materials. 

When a tensile load is applied to a fabric seam, it has to overcome two types of frictional forces. One is the inter-yam frictional forces within a fabric, and the other is the frictional force of the stitch assembly. The former is dependent upon the crimp, yam diameter, fiber content, and number of cross-over points. The latter, however, is dependent upon the fabric properties like fiber content, type of yam (spun or filament), thickness, lateral compression, cover factor (threads per cm), bending, shear, tensile and surface roughness, and coefficient of friction. It is also dependent upon the properties of the sewing thread like fiber content, diameter, coefficiait of Mction, initial modulus, and extensibility. All of these properties, together with the machine variables like needle and bobbin thread tension and the stitch length, make up the frictional force of the stitch assembly. Thus different combinations of these would be expected to provide different frictional resistance and hence different loads at which seam slippage may take place. 

A sewing stitch may be formed without any material, inside a material, through a material and on a material. All stitch types are formed by a needle penetrating into a fabric while transporting a sewing thread. It is essential to understand how the unique characteristics of every stitch type are dependent upon the mechanical actions of the sewing machine and fabric type, which determines the stitch properties. 

In these machines, the needle moves only up and down to form the stitch, and the clamp feed moves the fabric horizontally (jc-axis) or vertically (y-axis), creating the required shape. The movement of the clamp is controlled by a cam-follower mechanism or electronics. In a cam-follower mechanism, the specific pattern of button sew (e.g. N or X), specific length and width of buttonhole or specific shape of tack (e.g. I or D) can be made by one specific cam type, and for any change of pattern and/or shape of tack, the cam needs to be replaced and involves machine downtime. In an electronic machine, the movement of the cam is controlled by a microprocessor, and thus a different pattern and/or shape of tacks can be sewn easily by changing the program in the microprocessor. 

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. 

Another main problem found in the sewing room is the defects caused by the interaction between the needle and the fabric. This can cause different types of damages in the fabric, namely ... 

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)... 

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