AUTOMATED PROCESS CONTROL IN TEXTILE AND APPAREL INDUSTRY

Textile and garments process control technology is not as specific as vision technology; process control encompasses all textile manufacturing sectors. The process controllers relevant to textile manufacturing are basic information-electronic systems that, installed on the textile and garments machine, control certain fundamental parameters relating to the production process carried out on the machine itself. Essentially, they can be broken down into 4 categories according to the technology of the controller involved, which is itself dependent upon the type of process being controlled.

AUTOMATION IN PROCESS CONTROL SYSTEM
1.Cycle programmers: These process control system are present on many dyeing machines and they are based on the general principle of activating outputs according to inputs of the process. But their actual functioning is more specific. Those control system are pre-programmed to manage a sequential cycle of operations automatically. This facilitates programming, because the only thing that has to be done is determine the sequence of the steps in the cycle and the conditions required for the passage from one step to the next (the reaching of a certain temperature, the expiry of a set time, the arrival of a go-ahead signal, etc.). There exist two types of cycle programmer: one based on a microprocessor whose hardware and software remains the property of the supplier, and one based on a PC- or PLC-formatted architecture, which offers all the advantages of standard hardware and flexible software of automated process control.

2. PC-driven Programmable Logical Controllers (PLCs): these systems of process control are equipped to receive logical information (from switch or pushbutton contacts, limit switches, photocells, any kind of ON/OFF sensor) and to activate logical outputs (electric drives, relay contacts, etc). A controller checks continuously the status of inputs (openings/closures, presence/absence of electrical current), and according to the configuration of the inputs, activates its own outputs (activated/deactivated, ON/OFF, command presence/absence). The logical correlation between input status and the output status consequently imposed is determined when programming the system. Thus, the PLC can be regarded as a completely general purpose tool, capable of carrying out, when duly programmed by the user for proper process control, the most diverse functions. In practice, PLCs are used to resolve all those problems relating to automation and sequence management that used to be resolved using electrical systems and relay logics for process control. They feature on practically all the systems used for automated process control, in textile finishing, for operations such as washing, mercerization, dyeing, drying, calendaring, raising, pad-batching and steaming.

3. Numerical Controls of process control: these control system are electronic systems, specifically designed to control the positioning of a number of moving organs (e.g., robot axes). Using special languages, they programmed the sequences of the positions of the various axes, each of which is controlled through measurement of the position of the organ. This measurement is carried out by high precision transducers (encoders, resolvers, optical rulers), which transmit to the numerical control a number (hence the name of the system) which represents that position.

4. Special programmers: This automated process control system is developed specifically to carry out dedicated functions of textile process. These programmers are designed with and for the machine, in such a way that input and output signals and processing capacity are kept to the absolute minimum. In order to reduce costs, size and maintenance of production, they are often engineered in the form of single electronic cards. The four systems of process control described above are can be integrated with one another, and are often used together.

Benefit of automated process control
 -Better process quality
 -Reduction of errors
 -Greater production flexibility
 -Rationalization of the cycle according to scientific criteria
 -Rapid personnel training
 -Greater familiarity with production characteristics
 -Scope for integration with other company information systems
 -Repeatability of procedures
 -End quality no longer dependent upon the skill and experience of staff

Limitation of automated process control
 -Need for organizational changes
 -Difficulty personalizing the system to specific requirements
 -Difficulty interfacing with different IT products
 -Need for assistance and maintenance

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FABRIC RESOURCES

Primary Sources of Fabric
A primary source of fabric is a company that makes or creates the material. The Firms in this category are mills and mills and converters. Some of the mills produce woven fabrics exclusively; others make only knit fabrics, while some of the giant mills manufacture both.

In the Primary fabric market, most sales are based on contracts with shipments to be made months later. The converters and mills work closely with their customers designer’s and merchandisers to create designs and working samples. Sales of fabric either in inventory or about to be ready for sale (called spot or nearby goods) also occur, but on a much smaller scale. Unusually, very small orders will not be take, this being the function of the jobber.



 Fabric Resources (Mill)
The mill is a company that owns textiles machinery and makes fabric. The large textile mills are vertically integrated. They not only make the fabric, but also produce their own yarn and perform the finishing processes required after the fabric has been completed. However, they do not make their own fibers.
The mills sell their finished fibroin to various customers. The converter, discussed in the next section, is a major buyer.

Garment and home furnishings manufacturers use fabrics in making their products. Jobbers, who help dispose of excess or surplus merchandise for the mill, are another customer. Large retail stores, which in turn sell to the home sewer, also buy from the mills. Most of the staple fabrics are sold by the mills. A staple fabric is one, which is produced continuously each year with no change in construction or finish, and includes poplin, taffeta, tricot and sheeting. There are, however, many fancy or novelty fabrics also offered for sale by the mills.

The converter is an individual or organization that buys greige (or grey) goods (unfinished fabric), usually from mills, has the fabric dyed or printed and finished buy other companies, and then sells the finished fabric. All aspects of the fabric, including construction, design color and finish, are determined by ther converter.

Fabric Resources (Importer)
Many textile fabrics (and yarns) are made overseas and then imported into the United States. Since about 1980 the volume of textile imports has risen dramatically and today accounts for a large percent of the fabrics used domestically. While the greatest amount of textiles and textile products comes from the Far East. They are also received from many other parts of the world.

The textile importing companies are of two types. The direct importer buys fabrics or manufactured textile products (e.g.., clothing or soft luggage) from a foreign mill or other supplier. The other type, the import mills, is a foreign company that owns textile machinery and makes the fabric (or yarns) that is then exported. A secondary source of fabric is a company, which buys cloth and then sells it. Such a company is not involved in the making or creating of the material. Therefore, any seller of fabric other than mills and converters is considered a secondary source.

Fabric Resources (Jobber)
The jobber buys from mills, converters and garment manufacturers and other users. Although their purchases of a specific fabric type. Print or color are usually relatively small, jobbers nevertheless are valuable customers of the mills and converters. Jobbers often buy mill or converter fabrics that would otherwise be difficult to sell, including discontinued styles and colors and mill overruns. ( A mill overrun or tailing occurs when a mill produces more dyed, printed or finished fabric than the order specified . An overrun occurs for various reasons, including allowances for damaged yardage and short pieces unacceptable to the customer.) The jobber also sometimes buys fabric from users who have excess cloth. The excess cloth usually results from a decline in anticipated sales.

Fabric Resources (Retail Store)
Fabrics sold in the retails store are called over the counter sales and are bought by home sewer for their own needs. Put-up is the tern used to indicate the way fabric is packaged when it is sold. Most fabrics sold to garment and other manufactures are in a rolled, in either open width or tubular form. Some fabrics are doubled and rolled. Such fabrics are folded in half lengthwise, and then wound around a flat piece of cardboard. Cloth when sold to retail stores is usually in this put-up, in under 30 yard lengths. Velvet and other plush fabrics are usually not rolled because.

The resulting pressure would flatten the surface. The fabric is placed on a frame so the surface3 doses not contact any other part of the cloth. Pieces of woven fabric less then 40 yards in length are called shorts. These pieces are usually sold in either 20 to 40 yard pieces ( called 20 ‘ to 40 ‘s ), 10 to 20 yard pieces ( called 10 ‘s to 20’s ) or 5 to 10 yard pieces (Called 5’s to 10’s). Jobbers normally are the buyers of these short pieces of woven fabric.

Pound goods are usually very short pieces of fabric (often containing pieces less than one yard in length). They are sold by the pound and not by the yard. Fabric that cannot be sold in nay other manner is sold this way. These goods are bought at the buyer’s risk and receive the lowest price. End cases include stuffing for furniture and clothes for dolls.


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Knitted fabric properties

Wales per cm of knitted fabric

Wales per cm is a very much important properties knitted fabric. Wales are perpendicular lines of loop along the knitted fabric length. Wales is the column of loops along the length of the fabric. Wales determine the width of the knitted fabric and are measured as Wales per centimeter. The number of Wales per cm is depend the types of knitted fabric. For examples, 10 wales per cm is taken for single jersey knitted fabric and 7 wales per cm is taken for rib fabric knitting, it is measured along the course direction by using counting glass and needle.

  

Process sequence for measuring wales per cm of knitted fabric:

· When loop transfer occurs it is possible to transfer a wale A to another B and to recommence knitting with the second needle in which case more than one needle will have produced intermeshed loops in the same wale. 

· In warp knitting a wale can be produced from the same yarn if the same guide laps the same needle at successive knitting cycles . 

· Wales are connected together across the width of the fabric by sinker loop(weft Knitting) or under laps (Warp knitting) 

· Wales show most clearly on the technical face and technical back of single needle bed fabric. 

· For single jersey fabric wales show on face side as V shape and from back side as half circle.

Course per cm of knitted fabric:

A course is a predominantly horizontal raw of needle loops produced by adjacent needle during the same knitting cycles. Course is a row of loops across the width of fabric. A course determines the length of fabric and measured as course per centimeter. The number of course per centimeter is called course/cm. It Is measured along the wale direction by using counting glass and needle.