Sewing Knitted Fabrics

INFORMATION FOR THE SEWING INDUSTRY

SEWING KNITTED FABRICS Guidelines for sewing of outerwear, underwear, lingerie, shirts, blouses, swimwear and leisurewear

AMANN SEWING THREADS FOR THE KNITWEAR INDUSTRY The production of a wide range of outerwear, underwear, lingerie, shirts, blouses, swimwear and leisurewear from knitted fabrics is a very important part of the clothing industry. Thanks to their high wearing comfort, the excellent adaptability of fit to each individual’s measurements and movements, and their casual but elegant style, garments made from knitted fabrics have won a strong market position next to articles made from woven textiles, and have gained a high degree of acceptance among consumers. In fact, knitted fabrics are now the standard for garments like underwear, lingerie, shirts, blouses and swimwear. The generic term „knitted fabrics“ stands for certain kinds of textiles such as knitted and chainstitch fabrics.

The knitted fabric is produced as follows:

Stitch head Stitch shank Stitch foot

previous built stitch Stitch structure from right:

Stitch structure from left:

The stitch foot is placed under the head of the last stitch that was formed.

The stitch foot is placed over the head of the last stitch that was formed.

Adjacent stitches are referred to as a „stitching row“, and a line of stitches in the longitudinal direction is referred to as a „stitching line“. Row direction Knitted fabric (left/left pattern)

Knitted fabrics are made of stitches which are created from a loop of thread held in position by other loops of thread. A distinction is made between right and left stitch patterns, which determine the appearance of the right and left sides of the fabric.

Line direction

Stitching row

Stitching line

Chainstitch fabric (right/left pattern)

In the chainstitch knitting pattern, threads running in the longitudinal direction are looped together. The threads making up one or more ‘chains’ are shifted sideways and joined together with the threads of adjacent chains.

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To enable all the positive features of knitted fabrics to be exploited to the full in the production of garments, the typical characteristics of these fabrics must be taken into account in the sewing process. This means that, in addition to the sewing method best suited to the type of knitted fabrics used, the sewing thread must be included in this fundamental consideration because, after all, it is the connecting link.

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1. DEMANDS PLACED ON THE SEWING THREAD The following characteristics are required when working with knitted fabrics: 1. High tensile strength with a fine cross-section 2. Compactness and purity of the thread 3. Balanced elasticity, comfortable to the skin 4. Brilliant colours with high colour-fastness 5. Shrink-free, resistant to washing SABAC cone, spool, fashion colour card, card no.555 and product profile.

6. Heat-resistant during ironing 7. Precise winding and even thread take off

RASANT (polyester/cotton core-spun thread)

8. Resistance to wear and abrasion When these factors are considered more closely, it can be seen that they are equally applicable to the stitching of fine, lightweight knitted fabrics. In general, the task of the sewing thread is to absorb and distribute all the forces which are applied to the seams. At the same time it has to follow all movements elastically, regardless of the nature of the various sections which are joined together. 2. RECOMMENDATIONS FROM THE AMANN RANGE

RASANT is the proven, established sewing thread for the manufacture of garments like underwear, lingerie, shirts, blouses and lightweight knitted fabrics. Thanks to its cotton mantle and the resulting harmony with most knitted fabrics, RASANT has an extremely pleasant and comfortable feel. It offers excellent performance on all types of sewing machines used in the production of garments from knitted fabrics. Additional benefits of RASANT are its resistance to washing and ironing and seam durability. The extensive range of RASANT thread counts, structures and colours meets all the wishes of manufacturers carrying out sewing processes.

For the production of garments from knitted fabrics, Amann offers a range of sewing threads that meet all the demands of manufacturers: SABAC (polyester/polyester core-spun thread) SABAC is the universal thread for all seams. It guarantees the highest sewing performance on all types of machines, and ensures durable, long-lasting seams. Thanks to the thin cross-section and high flexibility of the thread, SABAC threads are non-obtrusive and give a comfortable feel and a high level of comfort in wear. The SABAC range offers a comprehensive choice of thread counts together with a wide selection of fashionable and matching colours.

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RASANT cone, spool, fashion colour card, card no. 5000 and product profile.

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TEXTURAN (polyester textured thread)

SEAM CONSTRUCTION AND SEWING

This thread type is used for overedge stitching or cover stitch seams, wherever a high degree of coverage and softness is required.

Two aspects are particularly important: 1. LONGITUDINAL ELASTICITY AND LATERAL STRENGTH OF THE SEAM 2. AVOIDANCE OF DAMAGE TO THE FABRIC BY THE SEWING PROCESS

1. LONGITUDINAL ELASTICITY AND LATERAL STRENGTH OF THE SEAM The right degree of longitudinal elasticity of the seam required to meet the strains arising during the later wearing of the garment is a very important factor in the sewing process. TEXTURAN cone with spoolholder, colour card 103 and product profile.

SERAFIL (polyester multifilament continuous thread) SERAFIL 120/2 and 200/2 are extremely fine threads with a smooth, completely uniform surface. Their application areas are blindstitch or overedge stitching or needle thread for extreme fine fabrics.

1.1 SUITABLE SEWING THREADS Synthetic or semi-synthetic sewing threads form the basis for elastic seams, because they combine a high tensile strength and well balanced elasticity with a small cross-section. The optimised diameter in comparison with other thread types allows the use of finer needles, which are an essential requirement for good sewing results with knitted fabrics. SABAC, RASANT, SERAFIL and TEXTURAN are the ideal threads to provide the desired bi-elastic wearing comfort of knitted fabrics. Cotton threads do not meet the demands that arise when working with knitted fabrics because of the following disadvantages:  low elastic breaking strain of approximately 5% stretch  significantly thicker thread cross-section for comparable tensile strength, requiring correspondingly thicker needles to be used which give unfavourable results with knitted fabrics

SERAFIL kingspools with colour card 25 and product profile.

 insufficient resistance to abrasion, which means that seam durability cannot be guaranteed

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1.2 QUANTITY OF THREAD IN THE SEAM To ensure good longitudinal seam elasticity, the quantity of thread used in the seam is an essential factor. The quantity of thread that can be achieved in practice is determined to a large extent by the type of stitch, the stitch density, the weight of the fabric and the thread tension. All these factors are well suited for seams with longitudinal elasticity, and are therefore used in making garments from knitted fabrics. The quantity of thread used will also be significantly affected by a change in the type of stitch. The more stitches that are sewn per cm of seam, the greater will be the length of thread used in the seam. This results in a higher seam elasticity. In other words, the general rule when sewing knitted fabrics is:

Seam elongation in % 100

Stitches/cm of seam length

90 80 70 67 %

60 55 %

50 46 %

40 30 20 10 1

2

3

4

5

6

stitches per cm

The greater the number of stitches per cm of seam length, the greater will be the length of thread used in the seam, and the higher will be the elasticity of the seam. The decisive factor for the choice of the most suitable stitch density is the combination of the material to be sewn and the desired elastic stretch value of the thread. As a general guide, a stitch density of 5 - 8 stitches/cm can be used, according to the type of stitch and the weight of the fabric. Very high stitch densities bring with them the risks of damage to the structure of the fabric and puckered seams.

Material: knitted fabric, pure wool approx. 300 g/m2 Sewing thread: SABAC No. 120 Stitch type: double chainstitch type 401

Compared with a straight lockstitch seam (stitch type 301), a lockstitch seam with a slight zig-zag (stitch type 304) and a seam width of approximately 2 - 3 mm will give a considerable increase in the longitudinal elasticity of the seam. The reason for this is the use of a greater quantity of thread compared with a straight seam.

The following diagram shows the influence of the number of stitches per cm of seam length on the longitudinal elasticity of the seam.

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1.3 SEWING MACHINES

1.4.2 LOCKSTITCH SEAMS

The ability to incorporate greater quantities of thread into the seam will be increased by the use of sewing machines with suitable stitchtypes and feeding systems (differential transport), which enables the fabric to be stretched further after the sewing process.

For interlocking machines, the needle and looper thread tensions should be set so that the interlocking of the two threads takes place in the centre of the fabric layers; i.e. the same quantities of needle and looper threads are used. The tension of both threads should be set as low as possible, as long as the resulting seam tightness is sufficient.

1.4 OPTIMAL THREAD TENSION Optimally adjusted thread tensions are a necessary to ensure correct thread balance and the use of a sufficient quantity of thread in the seam.

LOCKSTITCH (STITCH TYPE 301) Optimum and incorrect thread balance for a lockstitch seam:

1.4.1 CHAINSTITCH, COVERSEAMSTITCH AND OVERLOCK STITCH SEAMS For all chainstitch, coverstitch and overlock machines, the thread tensions are correctly adjusted when the needle thread appears as small dots on the underside of the fabric and the optimally tensioned looper thread can be pulled through these dot-shaped thread-loop ends without any effort.

Well balanced stitch pattern; maximum seam elasticity and tensile strength

Needle thread tension too high or bobbin tension too low; insufficient seam elasticity and tensile strength

DOUBLE CHAINSTITCH (STITCH TYPE 401)

Correct and incorrect thread balance, shown using an example of a double chainstitch seam:

Bobbin tension too high or needle thread tension too low; insufficient seam elasticity and tensile strength

Well balanced tension for a double chainstitch seam

Incorrect tension for a double chainstitch seam

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Examples of damage to the structure of the fabric

2. AVOIDANCE OF DAMAGE TO THE FABRIC BY THE SEWING PROCESS Damage to the structure of the fabric occurs when the fabric is penetrated by the needle. Since no allowance is made for the position of the fabric loops during the sewing process, the needle can penetrate at any point in the fabric. It can therefore deform the fabric loops or cause the fabric structure to be opened to such an extent that it will be torn open or damaged. In many cases this type of damage is caused by a finishing treatment of the fabric which is too hard. This makes the fabric loops rigid and inflexible and prevents them from being displaced by the tip of the needle. All knitted or woven fabrics made of natural fibres are particularly sensitive to damage when the humidity of the air falls strongly, for example in winter when central heating causes dry air. Natural fibres have hygroscopic characteristics, causing them to have a certain moisture content which keeps the fabric soft and flexible. Dry air makes natural fibres brittle, which makes the fabric inflexible. This means that they cannot easily be displaced when the fabric is penetrated by the needle, and are therefore liable to break during the sewing process. If extremely fine fabrics are being sewn under these conditions with high needle speeds, excessively thick needles or the wrong needle tip shape, the fabric structure can literally be destroyed. If very high needle temperatures are reached, molten particles from the fabric treatment, or in the case of synthetic fibres from the fabric itself, can become deposited on the surface of the needle, and in the needle eye. Thread breakages may occure.

Damage to the structure of the fabric can be prevented by: 2.1 USE OF THE RIGHT NEEDLE SIZE It is well known that if an excessive needle thickness is used, the fabric structure can be deformed beyond its elastic limit and as a result can be subject to an irrecoverable strain. This can result in significant damage to the structure of the fabric. For this reason, the thinnest possible needles, for example Nm 80 or 70, should be used. Ball-point needles will prevent damages as well.

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2.2 CHOICE OF THE RIGHT NEEDLE POINT When sewing knitted fabrics, it is beneficial to use needles with a small ballpoint shape („SES“) for fine fabrics, or a medium ballpoint shape („SUK“) for heavier fabrics. These points will not penetrate into the individual threads or capillaries of the fabric, but instead will simply displace them slightly. For special fabric grades, the use of needles with other tip shapes may also be found to give good sewing results. Note: The needle thickness has a greater influence on the possibility of damage to the fabric structure than the needle point, because the differences between „R“, „SES“ or „SUK“ needles with a thickness of approximately 70 are minimal.

2.3 FREQUENT NEEDLE CHANGING Even the slightest damage to the tip of the needle will automatically cause damage to the structure of the fabric each time the needle penetrates it. The needle should therefore be checked constantly and changed whenever necessary. Practical experience shows that frequent changing of the needle at regular intervals greatly reduces damage to the structure of the fabric.

2.4 SELECTING THE CORRECT NEEDLE HOLE SIZE The size of the needle holes in the needle plate should always be matched to the needle thickness, because if the needle holes are too large the fabric will be pulled through them in the shape of a funnel. This is another way in which damage can be caused to the structure of the fabric.

2.5 ADJUSTMENT OF THE MACHINE SPEED If the above recommendations are followed and the fabric is still damaged, the cause may be an excessively high rotational speed of the machine. Reducing the speed of the machine will always give better sewing results, and may in some cases allow the use of a thicker needle (for example in decorative lockstitch work). However, reducing the sewing speed should only be regarded as an emergency solution. A check should first be made of whether the damage to the fabric can be prevented by using a differently treated fabric which gives better sewing results.

Damaged needle point

Photo: SCHMETZ

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2.6 CARRYING OUT SEAM TESTS Before sewing knitted fabrics, thorough seam tests should be carried out on the various material weights and colours. It is impossible to be sure that no damage to the fabric will be caused in production until these tests have been completed with positive results. A final conclusion can be gained by a manual stress test, in which the fabric parts which have been stitched together are moved vigorously in relation to each other using both hands. Only a test like this will reveal stitches in the fabric which have been damaged during the sewing process, and which would not have been noticed by visual checking alone. Manual stress test

SABAC AND RASANT - STILL OUR STRONGEST ARGUMENT With SABAC, the polyester/polyester core-spun thread, RASANT, the polyester/cotton core-spun thread and TEXTURAN, the polyester textured thread, AMANN offers garment manufacturers a choice of threads which offer an outstanding combination of quality characteristics: Universel usage for all applications and production areas Optimal sewing characteristics on all machines = excellent results in automated processes Trouble-free sewing performance High lateral seam strength Superior resistance to abrasion Optimal elasticity Consistent colours from batch to batch

Outstanding seam quality Allows rationalisation of the sewing thread range, thanks to its suitability for both visible and invisible seams

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AMANN THREAD APPLICATIONS FOR KNITWEAR AND WOVEN FABRICS JOINING SEAMS

SABAC 80/ RASANT 75 for seams subject to high strains in menswear and leisure wear SABAC 120/ RASANT 120 for all seams subject to normal strains in menswear, women’s wear, leisure wear, underwear and swimwear SABA 150*/ RASANT 150 for all extremely fine seams in underwear, shirts and blouses etc.

OVERLOCK

SERAFIL 120/2, SERAFIL 200/2

AND COVER THREADS

SABA 150*/RASANT 150

DOUBLE CHAIN-

TEXTURAN 120

STITCH SEAMS

TEXTURAN 250

DECORATIVE SEAMS

SABA 30* SABAC 50, RASANT 50 SABAC 80, RASANT 75

BLINDSTITCH SEAMS

SERAFIL 120/2, 200/2 SABA 150*

EYELET BUTTONHOLES

SABAC 80 and where applicable SABA 30* as Gimpe RASANT 75

BUTTONHOLES IN SHIRTS,

SABAC 100

BLOUSES ETC.

SABAC 120/RASANT 120

*other thread construction or material

SEWING APPLICATION SUPPORT We will be glad to provide you with support in relation to any application and process issues. Please do not hesitate to contact us at:

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phone +49 (71 43) 277-250

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* Basis: Standard sewing material 1mm with 4 stitches/cm

THE MOST IMPORTANT STITCH TYPES IN THE KNITTED FABRICS INDUSTRY WITH SEWING THREAD REQUIREMENTS FOR STANDARD SEWING PARAMETERS*

More information can be obtained from our brochure „Determining your sewing thread requirements” STITCH TYPE

ISO 4915 DIN 61400

Two-needle double chainstitch

Two-needle double chainstitch with cover thread

Three-needle covering chainstitch with cover thread

Four-needle covering chainstitch with cover thread

Three-thread overedge stitch interlaced at needle hole

Four-thread overedge stitch

Double chainstitch

Lockstitch zigzag

Lockstitch

SEAMCONSTRUCTION

THREAD REQUIREMENT %

PER 1m SEAMLENGTH

NT: UT:

406

NT: UT: CT:

602

NT: UT: CT:

605

NT: UT: CT:

607

NT: UT:

504

NT: UT:

514

NT: UT:

401

NT: UT:

304

NT: UT:

301

3,40 m 8,40 m

29% 71%

11,80 m

100%

3,40 m 8,40 m 5,10 m

20% 50% 30%

16,90 m

100%

5,10 m 11,60 m 5,80 m

23% 52% 25%

22,50 m

100%

6,80 m 14,80 m 5,80 m

25% 54% 21%

27,40 m

100%

1,70 m 12,10 m

12% 88%

13,80 m

100%

3,40 m 13,70 m

20% 80%

17,10 m

100%

1,70 m 3,10 m

35% 65%

4,80 m

100%

2,70 m 2,70 m

50% 50%

5,40 m

100%

1,40 m 1,40 m

50% 50%

2,80 m

100%

NT=Needle thread · UT=Underthread (looper or bobbin thread · CT=Cover thread 11 5

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Amann & Söhne GmbH & Co. · Hauptstraße1 · D-74357 Bönnigheim · phone +49 ( 7143) 2 77- 0 · fax +49 ( 7143) 2 77 - 200 · http://www.amann-online.de 100041 GB05000120