24 Apparel Industry – Machineries, equipments, mechatronics used automation

V. Bhanurekha

1. INTRODUCTION

Manufacture of apparels is an activity dominated by the need for human skills, with a great range of raw materials, product types, production technologies, production volumes, retail markets and brands. It requires a lot of manual manipulation because of the limp nature of the material. The apparel manufacturing processes happen in three stages namely; pre-assembling processes, assembling processes and post assembling processes. All the three stages involve a wide spectrum of machineries and equipment and most of them have possibilities of integrating automations.

Recent times apparel sewing machinery has seen many developments ranging from new programmable sewing machines to a variety of gadgets, work aids and mechanized sub-assembly systems, to improve the quality and the productivity. Though the new innovations are effective the garment industries they lack investment capacity due to their small scale nature of business. This has created a large market for versatile and indigenous semi-automatic apparel sewing equipment at affordable prices.

2. LEARNING OBJECTIVES:

At the end of this module, the students will be able toacquire knowledge on the following available for the various processes involved in the apparel manufacture:

a) The various machineries and equipments

b) The various automations and software

3. MACHINERIES AND EQUIPMENTS IN VARIOUS STAGES OF APPAREL MANUFACTURE:

Pre assembling process involves fabric inspection, pattern making, fabric spreading, fabric cutting and labelling machines. Assembling process involves Sewing machines, pressing, fusing, welding machines, sealing, bonding and work aids like folders, trimmers, edge guides, movers, stackers etc. This stage involves various operations which assemble the garments parts together. Assembling processes dominate the output of a clothing factory, however large or small it is. Sewing is the major process which is involved in most of the garment factories. The objective of sewing is the construction of seams (the part where 2 garment components are joined together) that combine the required standards of appearance and performance with an appropriate level of economy in production. Post assembling processes involve the trimming, pressing, and a whole range of finishing equipments.

2.1. PRE-ASSEMBLING PROCESS:

2.1.1. 3D body scanning technologies:

The development of 3D body scanning technology allows for the quick and consistent extraction of body measurements and can generate customised fit for any number of people. For the clothing industry, scanners capture an accurate 3D representation of a garment’s relationship to the body. The extracted measurements and the virtual picture are the foundation for individual pattern construction and digital data management. The measurements obtained using this technology is more precise and reproducible than those obtained through the traditional, physical measurement process. Measurement data can be renewed or revised at any time. The 3D scanning technologies used for body measurement extraction on today’s market are based on various systems. Laser scanning technologies work on the basis of a light-plane and triangulation method. A laser is used as a light source and a technology called CCD (couple charged device) scans the field of view. The CCD detects the displacement of the light on a body. Body scanners based on laser technology are able to scan about 60,000 points per second.

3.1.2. Fabric defects checking:

Portion of defect less fabric is first scanned and stored as standard raster image (pixel information stored) for reference. Roll of fabric is exposed to image processing set up where camera starts examining fabric little by little. Sensed image is translated to digital image in form of 2-dimensional array (raster image) of numbers by analogue to digital converter. This sensed image is compared with standard image using algorithms and filters. Drop stitch run can be detected by applying low-pass filter to image. Low pass filter effectively averages out areas in image to highlight regions of different light intensities (hole or normal fabric).

Small areas of light between stitches will be eliminated but larger areas of light caused by passing through hole remain and thus hole is identified. Other details like dimensions and technical details of defect are also identified. There are other types of algorithms and filters which complete fabric defect checking process. These algorithms demand large processing time and hence require special purpose powerful processors for complete real time inspection for eg: parallel processing hardware like transputers or PC with frame grabber could be employed. This would take a sensed image, process it identify defects and then takes next frame. This frame management is highlight of using frame grabbers. Transputers are not economically viable.

Fig 2: Computer controlled Fabric defect checking system

3.1.3. Computer aided designing (CAD) software used for garment designing:

3.1.3.1. Pattern design and pattern making software:

The most popular CAD software used for garment design are pattern making, grading and lay planning software. Pattern making consist of the design and creation of templates from which clothing and craft items can be sewn. Patterns are made of pieces of paper shapes that are traced onto the fabric need to be cut, with each pattern piece serving as a form for an individual part of the garment or item to be sewn. For the purposes of sewn garment design, the software usually allows the designer to create patterns from basic sloper shapes (A sloper is a basic garment shape, also known as a body glove or a body block).The designers can then modify the patterns, insert darts and create seam allowances.

3.1.3.2. Pattern Grading Software:

The prepared patterns of the garment can be proportionately and systematically increased or reduced in required sizes in order to facilitate for better size customization in the mass production. This process is called Grading. The patterns can be viewed in the fabric layouts in which the designer can align the patterns, make the measurements and create markers. The final design can be printed in the form of a technical drawing. Also, the designs on paper can typically be digitized and then edited in such software.

3.1.3.3. Marker planning software:

The designed and graded patterns are imported into software called the Marker planning or the lay planning software. Marker planning software attempt to minimize the amount of fabric waste by placing the various graded patterns on a length of fabric as compactly as possible. The graded patterns are displayed as miniatures at the top of the screen, and separated into their sizes – which sometimes is reinforced by being in different colours. The fabric width is given as an input, so the simulated fabric is available on the screen to arrange the various graded patterns. The arrangement is done so as to enable the economic usage of the fabric and the marker length is determined. All patterns are configured to lay along the grain of the cloth, as designated to individual patterns during the pattern making process.

The lay planning software interacts with the pattern making, grading and cutting software programs which means that at any stage the other programs can be accessed to change any part that needs adjusting, such as grain lines or punch holes, etc. It means that the system gives much greater flexibility and speed when adjustment is needed, and does not mean a long process of scrapping a whole marker just to alter some small details. When the marker is finished and deemed efficient enough, it is stored for further use. The lay plan can also be plotted out in miniature and sent with the patterns to an outworker unit to enable manual laying of the patterns and cutting. Otherwise the lay plans could be directly fed into the computer controlled cutting systems for the next step of fabric cutting, thereby avoiding the printing and saving paper.

3.1.3.4. Virtual proto typing:

Virtual proto typing is using virtual reality to create product prototypes and test their properties. Virtual prototyping is a computer-based prototyping technique in the process of apparel product development. It contains Computer-Aided Design (CAD) and Computer-Aided Engineering (CAE) software to validate a design before committing to making a physical prototype. This is done by creating (usually 3D) computer generated geometrical shapes (parts) and either combining them into an “assembly” and testing different automated motions, fit and function or just aesthetic charm.

One of the major challenges for any fashion company is ensuring that the fit of a garment is as close as possible to its target customer. The process of fit approval is a lengthy and expensive process which may require several iterations before the garment is fit-approved or eventually rejected from the line. Involvement of 3D technology at this stage can help reduce cost and time-to-market by digitally doing the patterns and virtual making of sample which will again contribute to reducing the number of samples required and their associated costs. Virtual prototyping permits firms to gauge and enhance product performance virtually.

3.1.4. Fabric spreading:

Spreading is the process of unwinding large rolls of fabric onto long, wide tables in preparation for cutting each piece of garment. Precautions needed while spreading fabric so that the plies are aligned as per requirement of the final garment, in consideration with the fabric defects the lays should contain only defect less portions of the fabric. The fabrics have to be spread in the correct ply direction and tension. The fabric must also be flat and free from any crinkle & crease. Spreading may be done in many ways like – Manual Spreading, Machine Assisted Spreading, Semi- Automatic spreading and Fully Automatic spreading. Spreading related Equipment are a table and Fabric Loader to spread fabric on the tables, which is controlled mechanically or by a computer. The tables may be of various types like Normal table, Vacuum table, Conveyor table, Pinned table.

Fully Automatic Spreading Machines have Automatic loading/unloading device for fabric rolls, Automatic roll turning arrangement for face to back lay, Automatic leveling device for fabric edge alignment. , Automatic cutting device at the end of a run, Automatic tensioning device to control fabric tension, Automatic lay height sensing elevator and Programmable lay length, ply height and step-laying. Spreading seeds are up to 140 m/min.

3.1.5. Fabric cutting:

Cutting is the process where fabric is cut out into pattern pieces from specified fabric, to be assembled as garments through various assembling methods. Types of Fabric cutting machines:

i. Manual, e.g. scissors

ii. Machine cutters: Semi-automatic or Fully computerized a. Portable cutters like straight and round knife cutters

b. Stationery cutters like band knife, die cutting, servo cutting, plasma cutting, water jet cutting or laser cutting

c. Position markers like notchers, drills and thread markers

Advantages of semi-Automatic Cutting Equipment are they are comparatively cheap, production speed is very good, rough work can be easily done by hands. Their disadvantages are Faulty knife could damage fabric layer, knife required to be changed, weight of the motor creates knife deflection which may create faulty pieces.

Advantages fully-automatic Cutting Equipment are cutting defects are less, less labor cost as the machine requires less human intervention, Suitable for very large scale of production. There is no need of marker paper to be printed as the marker planning details are directly load on to the computer of the cutting machine and this guides the cutting machine head to cut the fabrics. Some of their disadvantages are that they are very expensive machines, very high on maintenance, some methods are not suitable for cutting multilevel fabric like laser cutting, some methods are not suitable for synthetic fabric like laser cutting.

3.1.6.Cut order planning software:

Cut order Planner is a software package for use in the textile manufacturing industry for automatic cut order planning. CutPlanner takes a customer’s order for a clothing item and creates a cut plan for that item, including different sizes and different fabric types or colors, which minimizes production costs. A cut plan is an assignment of sizes and fabric types to markers. For each of these markers, the required number of plies is computed to fulfil the order’s specifics. The objective of CutPlanner is to minimize total production costs. They consist of the costs for the fabric used, and several production costs incurred by making the markers, preparation of the cutting process, and the picking of pieces to be cut.

3.1.7.Labelling machines:

The InfoMark GERBER labeler is an optional label application system for GTxLmulti-ply GERBERcutter® systems. It automatically prints, positions and applies labels during the cutting process. The InfoMark GTxL labeler is installed directly on the head of the cutter. The InfoMark prints and applies labels as parts are cut. As a result, through put is increased, the time to pick parts is improved and post-cutting part identification is made easier. Placing up to 30 labels per minute, it uses inexpensive, off-the-shelf, adhesive back labels. Using the InfoMark labeling technology, the need for plotter paper is eliminated. In addition, operators are no longer required to handle plotted markers or nests and thereby reducing manual identification time and freeing them to focus on other tasks.

3.2. ASSEMBLING PROCESS:

In garment production, until garment components are gathered into a finished garment, they are assembled through a sub-assembly process. The production process includes a set of workstations, at each of which a specific task is carried out in a restricted sequence, with hundreds of employees and thousands of bundles of sub-assemblies producing different styles simultaneously. Various industrial sewing machines can sew different types of stitches. Some machines work sequentially and feed their finished step directly into the next machine. There are other processes, which have multiple machines performing the same operation or a series of operations done in a sequence and then passed to the next operation. Finally, the sewn parts of the garment, such as sleeves or pant legs, are assembled together to give the final form to the clothing.

The most common and conventional method of joining or assembling fabrics is by sewing with needles and threads or a sewing machine where stitches are formed in various types. These seams can be used in garments made from porous fabrics. However, if the garment is made from non porous materials such as those used for water proof, fire resistant or chemical resistant clothing, then the perforations caused by a conventional sewn seam will compromise the integrity and performance of the garment. For example, a water proof garment will leak at the seams or dust particles will be able to pass through a dust proof garment. For such applications, therefore, either the sewn seams are sealed with tapes or entirely new technologies based on welding and bonding of layers are being employed to create fully sealed seams.

3.2.1. Sewing machines:

Categories of Sewing Machines: Sewing machines are categorized based on stitches formed, bed type, feeding mechanism and the lubrication system. One unit of confirmation of thread resulting from repeatedly passing a strand or strands or loops of thread into or through a material is called a stitch. Stitches can be formed without a material, inside material, through material and on material. Stitch types are formed by

• Interlacing – is passing of a thread over or around another thread or loop of another thread, example stitch type 301.

• Intra-looping – is passing of a loop of thread through another loop formed by the same thread, example stitch type 101.

• Interlooping – is passing of a loop of thread through another loop formed by a different thread, example stitch type 401.

Fig 2: Methods of stitch formation

Sewing machine classification based on stitches:Class 100 – Single chain stitch varieties, Class 200 – Hand stitches and their simulations, Class 300 – Lock stitch varieties, Class 400– Multi thread chain stitch varieties, Class 500 – Over lock chain stitch varieties, Class 600 – Covering stitches – to hold heavy fabrics, Combination stitches – eg – 401.504. Machines which can sew these stitches are Single needle lock stitch machines, Over lock machines, Flat lock machines, Buttonhole sewing machine, Button sewing machines, Smocking machines, Shape tack machines, Cycle stitching machines with input facilities, Multi needle chain stitches, Automatic pin tuck machine etc.

Classification based on bed types:Flat bed, Cylinder bed, Post bed, Wide armed bed

Classification based on feed types: Drop feed, Compound feed, Differential drop feed, Unison feed, Drop feed and Variable top feed, Differential drop and Variable top feed, Wheel feed/Puller feed, Cup feed

3.2.2. Welding:

The term welding refers to the thermal bonding and sealing of seams in knitted, woven, and nonwoven thermoplastic materials without adhesives, chemical binders, staples, needle, or thread. Thermoplastic coatings, such as polyvinylchloride (PVC), polyurethane (PU), polyethylene fabric (PE) and polypropylene (PP) are used for heat sealing. It is done when the product needs to have special functional properties like water resistance, abrasion resistance, resistance to thread decay, and fine appearance. The three principles of welding fabrics are heat, speed and pressure. The precise combination of these principles allows one to achieve a properly welded seam in thermoplastic materials either by point bonding of fabric or continuous sealing of film. The efficiency of welding of a woven fabric is affected by yarn density, thermoplastic content, tightness of weave and uniformity of material thickness while the random orientation of fibres in nonwovens gives them excellent bond strength.

3.2.3.Ultrasonic sealing machine:

Ultrasonic Fabric Sealing System bonds nonwoven and manmade thermoplastic materials without the use of a needle or thread. Materials are produced at the rates up to 50 surface feet per minute. With modifications, speeds up to 160 feet per minute can be achieved. In order to achieve successful seaming, thermoplastic fabrics, or fabric containing significant amount of thermoplastic materials must be used. 100% synthetics such as nylon, polyester, polypropylene, polyethylene, modified acrylics, some vinyls, urethane, and synthetic blends with up to 40% non-synthetic fiber content have been processed by other investigations. Garments that are typically made with this technique of assembling include protective garments, disposable hospital gowns, shoe covers, face masks, infants’ nursery garments, filters, bags, curtains, sails, and web splicing. Ultrasonic seaming is beneficial in the manufacturing of these items because the sealed edges and seams with no stitch holes provide no penetration by chemicals, liquids, blood-borne pathogens or other particles

3.2.4. Bonded seams

Bonding is a process used to join two fabrics that are non thermoplastic such as cotton or wool or blends with little synthetic content. In this process, a heat activated materials is placed between the two layers, and as heat is applied, this heat-activated material begins to flow into the fibres of the fabric, joining them together. Different technologies of pasting and welding are used for thermoplastic bonding of textile layers. It allows the elimination of sewing for many applications, including seams, hems, zippers, pockets and patches. By using adhesive films designers may perfect the technology of garments and improve their construction. Bonded garment technology allows for a seamless look and feel, moreover, bonded seam can be waterproof.

3.2.5. Work Aids:

The work aids that are used during sewing operations can be categorised in a number of different ways based on their purposes. Some offer greatly to increased productivity and some to perfection in quality and a few more just to help hold the pieces to be assembled or to hold assembled components. In terms of their function the commonest ones are used for guiding or folding materials, for trimming threads and other components from garments, and for stacking the work after sewing. The method of working of all these work aids may be mechanical, pneumatic, photo-electric and some are electronic. Some are built into the machine such as a special motor, some are a variation of a normal machine part such as a special presser foot, and some are a completely separate added part.

They are guides, edge guides, folders, clips, Feeding Devices, stackers, Special pressure feet, Stitching jig, slack feeding and elastication, computerized controls and equipments etc. Most of the other work aids are dynamic, e.g. those that help supply materials to the needle point. Compressed air can be an effective work aid, assisting the quantity and quality of a machinist’s work. One such application overcomes the problem of single jersey fabrics which curl at the edges, especially when given a light pull as they are handled through the machine.

3.2.6. Fusing:

A wide range of fusing machines is available which prepare garment components to be sewn. Fusing attaches garment component layers with 3 basic parameters of heat, speed and pressure. It needs the principle layer, the fusing material and bottom layer to be fused together. Fusing material has a base material woven, knitted or non woven and a layer of thermo plastic material. Many varieties of fusing material are available which vary in the thickness of the base material, quantity of the thermo plastic material, techniques in which the thermoplastic material is applied on the base material etc. Collars, waist bands etc are examples of fused garment components. To prepare a fabric to be embroidered, nonwoven backing material is fused. Varieties of fusing machines are available with their design owing to their end use. Fusing machines are available with roller mechanism or with pneumatics.

3.3. POST-ASSEMBLING PROCESS:

3.3.1. Pressing/ Finishing:

The next operations are those of finishing and/or decorating. Moulding may be done to change the finished surface of the garment by applying pressure, heat, moisture, or certain other combination. Pressing, pleating and creasing are the basic moulding processes. Creasing is mostly done before other finishing processes like that of stitching a cuff. Creasing is also done before decorating the garment with something like a pocket, appliqués, embroidered emblems etc. Vertical and form presses is automated machines. Perform simple pressing operations, such as touching up wrinkles in knit shirts, around embroidery and snaps, and at difficult-to-reach places on garments.

Pressing makes a large contribution to the finished appearance of garments and thus their attractiveness at the point of sale. Steam and pressure are frequently applied during garment assembly to ensure the quality of the final product. For the opening of seams, creasing of edges, and pressing garments with gathers and fullness, and in situations where style change is frequent, pressing with an iron is common because it is simple and flexible. Garments requiring extensive under pressing and final pressing include those that require the pressing open of seams and the setting of edges during manufacture. They are often of more mouldable fabrics, which use large areas of interlining and are usually wholly or partly lined. The category includes men’s jackets, trousers and waistcoats, many skirts, women’s tailored jackets and trousers, topcoats, trench coats and other lined rainwear. Style change in many of these garments is infrequent and a range of specialised, shaped press equipment has been developed. Pleating or ‘permanent press’ finishing will be described later.

3.3.2. Automations in the apparel industry:

Automation has a key role to play enable rapid adjustments from style to style, eliminating non-productive handling of fabrics and garments, improve quality, eliminate handling defects, eliminate manual error, accuracy in mass production, accurate reproduction, decrease labour strain, better utilisation of labour skill. The various tools for automation which are generally adapted in apparel industry are Computer controlled sewing machines or pneumatics. Typically, the computer programs for different stitches are stored in removable memory disks or cartridges. The sewing-machine computer may also hook up to a PC in order to download patterns directly from the Internet. They also have a series of sensors that tell the computer how all of the machine components are positioned. By precisely moving the work area forward, backward and side to side while adjusting the needle assembly to vary the stitching style, the computer can produce an infinite number of elaborate shapes and lines.

4. Automated workstations

These carry out many complex functions in addition to sewing. They make use of electric, electronic and pneumatic control, and incorporate sophisticated conveyor and clamp technology. Examples are patch pocket setting on jeans and shirts, run stitching collars or flaps, long seam joining, making jetted pockets, serging trousers and sequential buttonholing. The operator still loads the machine and may remove the garment part after sewing, but the machine controls the rest of the handling and all of the sewing.

The operator is able to undertake various handling activities, depending on the type of machine, during the sewing cycle. Thus handling time is incorporated into sewing time and the machine utilisation can rise from the 20 per cent that is typical of a basic sewing machine to as much as 80 per cent. Each machine carries out one basic conformation of sewing, but size or shape of, for example, collar or patch pocket, can be altered for different sizes and styles.

Automated workstations have achieved productivity improvements by: Increasing speeds of machines, numerically-controlled features often combined with Sensors; enabling easy maintenance of pay roll, worker evaluation and reporting, attachments and work aids in order to improve speed and quality and requiring the operator to load and unload only, enhancing reliability and thereby reducing downtime, quick changeovers, thereby reducing downtime each workstation is allotted with an operation. Operations are the divisions of the total work content of garments. Each operation consists of a work cycle, which is the sequence of elements of cutting or sewing, fusing or pressing, required performing a job or yielding a unit of production to complete a garment. Programmable automated work stations could be reprogrammed and a change of garment style could be taken up for production.

4.1. MICROCHIPS IN SEWING MACHINERY

Application of microchips in sewing machinery extensively helps to control and diagnose sewing machine functions. Some of the functions of such machines are programming stitch in pattern tacking machines, controlling the speed of the machine, programming the number of stitches in different sewing cycles, controlling the feed dog movements, diagnosing the machine malfunction area, Voice activated start-stop of machine, step motor for driving puller, computerized thread tension monitoring (active tension control), thread break/exhaust indicator for needle, bobbin and looper, online seam quality inspection / Fabric ply sensor , speed responsive presser foot, pressure / Elastic/tape metering device.

4.2. RFID :

Radio frequency identification (RFID) technology is used in Cut Part Identification Systems. It collects and analyzes production data during the entire production workflow on a real time basis. This specifically deals with common production problems encountered on the shop floor. An RFID system not only obtains information about production quantities in real time basis but also traces the efficiency of each lines, performance of each sewing machine and each workers. It shows who is working in which bundle, fast resolution of bottlenecks and rapid tracing of quality issues to their source. Main components of the system are RFID software, computer, data cable, RFID card, RFID scanner, RFID reader and terminal to display information to the operator. In real time RFID system, data is captured through scanning of RFID cards (tags) at operator terminals (workstation).

To manage production, shop floor production information is very essential. For the purpose of line balancing, knowing hourly production and even individual operators performance at the end of the day the common method is capturing operator wise production quantity manually. To replace manual data tracking process with IT based technology, Bar code and RFID systems are available. Both systems have their own advantages and disadvantages. Multiple RFID tags can be scanned at a time and RFID reader scan tags from any direction within a limited distance. Only one bar code sticker can be scanned at a time and Bar code scanner scan a Bar code from front only.

So RFID system is faster in data capturing. In the case of installation and running Cost, for Bar code initial cost is less compared to RFID but running cost will be high in case of Bar code system. RFID can be reused many times where Bar codes consumed once can’t be re-used. In RFID you will get real time information which enables reporting and maintaining the management information systems. In case of Bar code updated production information is got only when the individual barcodes are scanned explicitly which is generally done once in 2 hours.

Conclusion:

Apparel industry is equipped with wide varieties of machineries and equipment and is well driven with sophisticated automation technologies. These automations are steadily increasing according to the growing needs of the dynamic apparel industry and will for sure improve the quality and productivity of the industry in multi-folds.

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References

Carr and Latham ( 2008). Technology of Clothing Manufacture(4th ed.) , ISBN: 978-1-4051-6198-5, Wiley-Blackwell
Wendy Horobin(2003). How it works- Science and Technology(3rd ed.), Marshall Cavendish