HAND STITCH SEWING MACHINES FOR MEN SUIT MANUFACTURING

: Hand stitches seams along edges of lapels, collars and pocket fl aps on a men jacket help to fi x canvas interlining under face fabric, keep the edges fl at and prevent them from rolling or curling. Traditionally hand stitches seams also indicate high quality of the suit. Real hand stitch machines imitate had stitch 209. Depending on the length of the top and bottom stitch parts the machines can create pick stitches, saddle stitches and other stitch patterns. One group of the machines create stitches by help of a hooked needle, other machines use a double pointed needle. The machines work with limited length threads, most often with 90 cm and 120 cm long ones. The hand stitch seams can to be sewn with special waxed silk threads or regular threads. To increase work productivity and quality the machines use manual or auto thread trimming devices, reverse stitch function, half stitch option, seam beginning and end securing, programmable stitch type, sewing speed, stitch length, thread trimming time.


INTRODUCTION
To ensure high productivity work process, wide range of special sewing machines are developed to manufacture men suits in industrial way. They replace temporary and permanent hand stitches with machines stitches of the same or diff erent structure and appearance but the same application [1,2].
Permanent decorative hand stitch seams use to be sewn on edges of lapels, collars, pocket fl aps, front lines and other places of men jackets and vests [3,14].
In tailored suit these small almost invisible stitches help to fi x canvas interlining under face fabric, keep the edges fl at and prevent them from rolling or curling [3,4]. With time hand stitch seams got also important decorative function (See Fig. 1). They are sewn with waxed silk threads in the colour of the jacket or in contrast colour [3]. The hand stitch seams along lapels and a collar of the jacket indicate high quality of the suit, the best materials and complicated manual or mechanized technologies used in its manufacturing process. The machines which imitate had stitch 209 [5], (see Fig.2, 3, 4) are called real hand stitch machines (can be used also other names, such as, decorative hand stitch machine, pick stitch and saddles stitch machine, pin point and saddle stitch machine). They are developed by companies: Juki, Japsew, AFM, Complett, ASS, Global, New-tecH, Alfa, Foxsew, others. Compar-ing with other type sewing machines, they are slow. Their speed is only 350-500 r.p.m.

STITCH PATTERNS
One complete stitch 209 consists of two parts -a top stitch which lies on the top fabric surface and a bottom stitch which is created on the bottom fabric surface [5], (see Fig.4). Every part of the stitch is formed in separate work step of the machine.
Depending on the length of the top and bottom part of the stitch, diff erent stitch patterns can be created: • pick stitch -top and bottom stitches are very short almost like small dots (see Fig.1 and • long/short variations -longer top stitches and shorter bottom stitches or vice versa (see Fig.4.3); • irregular stitches -all diff erent variations of changing length stitches on both fabric surfaces, for example, two long/one short, three short/two long, other variants (see Fig.3.c).

STITCH FORMATION PRINCIPLES
The real hand stitch machines use two diff erent kind of stitch formation mechanisms with diff erently shaped needles. One group of the machines create stitches by help of a hooked/ bearded needle (Japsew, Global, Alfa, Foxsew, Complett, New-tecH, ASS), [6,7,8] other machines use a double pointed needle (AFM, Juki), [9,10,11].
Hook needle (see Fig.5): The stitch is formed by help of three main components: a hooked needle, an upper thread hook and a lower thread hook. In the fi rst step the hook needle together with the upper looper creates the upper part of the stitch on the top fabric surface. In the second step the needle and lower thread hook forms the bottom part of the stitch on the bottom fabric surface [6,7,8].
Double pointed needle with an eye in the middle (see Fig.6): During the work process the needle is fi xed alternatively in two needle bars. In the fi rst work step the needle operates above a throat plate being fi xed in the upper needle bar. It makes the fi rst part of a stitch placed on the top fabric surface. After the needle penetrate the fabric and moves under the throat plate, it is fi xed in the lower needle bar to create the second part of the stitch on the bottom fabric surface. This is more advanced stitch formation principle. While the hook needle use to snag threads in delicate fabrics, the double pointed needle with a standard eye this problem does create [9,10,12].

THREADS
Sewing seams of the hand stitch 209, the thread has to be pulled through the material in its entire length. Therefore the length of the thread is limited. The most often machines work with 90 cm and 120 cm long threads. The threads for the hand stitch machines use to be sold in already cut-to-length pieces or in standard cones. To cut thread from a standard cone the machines can be equipped with manual or auto thread trimming devices. On average from 120 cm long thread 100 cm long seam can be sreated (seam length depends on material thickness).
Top quality hand stitch seams are sewn with special waxed silk or synthetic threads (produced by companies Fujix and Onuki Limited (Japan), others). They have higher strength and smooth surface allowing the machine to work in higher speed. All hand stitch machines can work also with regular threads slightly reducing the quality of the seam and sewing speed, but reducing production costs considerably. The waxed silk threads are much more expensive than regular ones.

ADDITIONAL FUNCTIONS TO INCREASE PRODUCTIVITY AND QUALITY
The most part of machines have reverse stitch function. By help of it any type of stitch pattern can be reversed stitching a front line of a jacket at the lapel break point (see Fig.7).  The machines can have also half stitch option. When at the end or a corner of the seam there is not more space for a full stitch, the machine can create a half stitch [14]. The seams use to be secured at the beginning and end with zig-zag stitches, bar-tacking stitches, or reverse-feed stitches. The machines use diff erential bottom and top feed mechanism [13,14] with a walking foot (see Fig. 8) to ensure qualitative seaming of diff erent thickness woven and knitted materials. A presser foot consists of two parts -a left teethed foot and a smooth right foot. The teethed part of the foot together with the bottom feed dogs moves the fabric ahead while the needle is out. The right part of the foot presses the fabric down while the needle is in the fabric. The user of a computerized machine [13,14,16] can program and store large number of diff erent stitch patterns (up to 100). Programmable are also other parameters: stitch type, sewing speed, stitch length, thread trimming time etc.

CONCLUSIONS
By help of the real hand stitch machines industrially manufactured suits can get visual appearance similar to tailored ones. The machine seams are perfectly parallel to the edges where they are created and all stitches has precise determined length. These are important quality parameters for decorative seams with contrast colour threads. Seams with the same high quality can create only very skilful tailors. However, the real hand stitch machines cannot fully replace hand stitching. Changing tension of stitches at certain places of the seam, tailors form the needed curved shape of lapels and collars of a jacket. This process cannot be fully ensured by the machine.
Real hand stitch machines are also used to create decorative seams on other kind of garments and home textiles. However they are not seen often in clothing factories. They have comparatively high price and low stitching speeds. Limited length of the thread forming hand stitches 209 create certain diffi culties in the work process, too. If the whole seam cannot be formed with maximal available length of the thread, sewing cycle has to be stopped to continue it with the new portion of the thread. Problematic is also securing of the end/beginning of the seam to avoid its unraveling. This process takes additional time and can reduce the quality of the seam if the thread changing place becomes visible. However, real hand stitch machines are ten time more productive than hands of a experienced tailor and in industrial manufacturing of men suits cannot be replaced with any other kind of machine.