MMS

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CHAPTER 5

TAXONOMY OF APPAREL MANUFACTURING

5.1 VALUE CHAINS IN APPAREL PRODUCTION

5.1.1 Overview

Apparel production, also known as garment production is a process

where fabric is being converted into garments. The term apparel production is

basically used when garments are manufactured in a factory. Traditionally

apparel manufacturing factories have been divided into two sectors such as

domestic and export. A factory produces bulk quantity of garments for a style

or design at a time. Prior to starting production of an order, factory needs to

gone through some activities which are known as pre-production. Pre-

production process includes sampling, costing, production planning, sourcing

of raw material and production pattern making. Fabric cutting, printing,

embroidery, sewing, thread trimming, washing, ironing, folding and packing

are the production functions

5.1.2 Sampling

Sampling is a process where factory develop garment samples

according to buyer's specified design. This is also known as product

development stage. Samples are required at various stages to get approval

from buyer on a particular design. As per the development stages samples are

named as Proto sample, Fit sample, Size set sample, Sales man sample,

production sample, Top Of Production (TOP) sample and shipment sample.

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5.1.3 Costing

A business is all about making profit. So correct costing of a

product before order finalization is very important. Costing of garment is the

cumulative cost of raw materials, direct labors and direct and indirect

overheads. After developing sample or directly receiving buyer's sample,

factory needs to send FOB (freight on board) price of the garment. To decide

FOB of a garment, factory makes cost sheet including raw material cost, total

of direct labour costs of each processes, and factory overhead. An FOB is the

sum of garment cost, factory margin and taxes.

5.1.4 Production Planning

After receiving the order, factory plans for raw material

requirement for the order. Raw materials like fabrics, sewing threads, packing

materials, hang tags and other accessories are sourced. Factory plans time

lines like when to start cutting, when to submit pre-production sample, when

to finish sewing and finishing, final inspection date and shipment date. In

production planning stage job responsibility for different processes are

defined.

5.1.5 Cutting

In this stage fabrics are layered on a table, layer by layer, up to a

certain height. Then by means of a cutting machine fabric are cut into garment

shapes or pattern and separated from the layer. Fabric layering is possible for

both manual spreading and automated spreading. Cut parts are then numbered

and bundled and sent to sewing room. The quality of end product (garment)

very much depends on the good cutting quality. Secondly, fabric is the

primary raw material of the garment represents about 70% of total garment

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cost. That is why cutting is an important process to minimize the cost of

production.

5.1.6 Sewing

Garment panels are stitched together in sewing room by means of

sewing machines. In sewing 2D fabric patterns are converted in 3D forms. An

operator run the machine and using sewing threads garment parts are joined

together. Various types of sewing machines are available for sewing.

Machines are selected according to the seam and stitch requirement. In

industry traditionally sewing machines are laid in row. Cut parts are fed at the

start of the line, passed through the line and at the end of the line a complete

garment comes out. Each machine is run by individual operator and an

operator sews only one or two operations of the garment. A line consist of

sewing operators, helper to feed them with cut parts, thread and other trims,

quality checker and one fully or partially devoted supervisor.

5.1.7 Thread trimming

After stitching, all hanging thread are cut by means of hand

trimmer. Auto thread trimming machines are also available to perform this

task. All loose threads inside a garment are removed as well. Garments

without any loose thread and long tail are basic quality requirement.

5.1.8 Washing

This process is performed when buyer wants washing or special

finishes to the garments. There are various kind of special washing are

available such as emzyme washing,stone washing, Acid washing, Silicon

washing, softener washing etc… For light color garment washing is carried

out to remove dirt and stains though buyer does need washed garment as per

orders.

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5.1.9 Finishing

Generally this process includes checking of garment, measurement

checking, ironing, and spotting. After sewing of the garments, all pieces are

checked by quality checker to ensure that garments are being made as per

buyer quality standard. Checking normally is done for visual appearance and

measurements. Spotting is required to remove stain in the pieces. Various

chemicals (solvents) are used to remove various kinds of oil stain, marks and

hard stain. Each garment then ironed to remove creases by means of press.

5.1.10 Packing and Folding

Each pressed garment is then folded with tissue or card board.

Folding varies with product to product and also buyer to buyer. Hang tags,

special tags and price stickers are attached with plastic Kimble or threads.

Folded and tagged garment are then packed into poly bag. During packing

garments are randomly checked by internal quality controllers to ensure that

only quality goods are being packed.

5.1.11 Final Inspection and Dispatch

Once garments are packed (also known as shipment), before

dispatching quality inspection of the garments is carried by buyer Quality

Assurance (QA) department. Many times a third party quality auditor is hired

for this final inspection job. If the packed goods meet the buyer’s quality

standards, shipment is accepted by buyer. Factory then dispatches goods to

the buyer.

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5.2 APPAREL PRODUCTION SYSTEMS

Sewing fabric is a large segment and the most labor intensive

process involved in the production of garments. The sewing room has also

undergone changes to improve the productivity and responsiveness in sewing

(Malhotra 1991). Apparel products fall into the category of piece part goods

like automobiles, ships, airplanes, appliances; etc.The production process

involves the manufacture of numerous discrete parts that are then assembled

into finished products (Malhotra 1991). Most of the production systems

employed in clothing factories is as follows.

5.2.1 Make through/Whole Garment System

This is essentially the traditional method of production whereby

one operator assembles the entire garment. In men's bespoke wear, it is not

uncommon for a tailor to perform nearly every operation required to make the

garment, including machining, hand work and pressing. With this production

system the operator would be given a bundle of cut work and would proceed

to sew it according to his or her own method of work. Of necessity, the labour

required by this system must be highly skilled and versatile, a combination

which is becoming exceedingly rare and increasingly expensive.

This type of system is effective when a very large variety of

garments have to be produced in extremely small quantities. A typical

application would be in the sewing room of a boutique, which produces its

own merchandise. In the whole garment system one individual makes the

entire garment from cutting the cloth to sewing and pressing the garment. The

garment is ready for dispatch once the operator completes the final operation.

This type of system is used in a few places, which are engaged in custom-

wholesale. They are normally high priced and exclusively made for a

particular customer. They are limited in number and distribution; normally

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about 10-20 garments are made.It is the traditional method of manufacturing

in which an operator makes one garment at a time right through. That is one

operator will do all the stages of the sewing operations of one garment and

after completing it he/she will go for the next garment.

Advantages

This system is more effective when a very large variety of

garments have to be produced in extremely small quantities.

In individual piece rate system the operators will do their work

with full involvement to finish more pieces, to earn more

money.

Operator will be specialized in his own working area.

As the pay depends upon the complication of the operation,

the operator will try to finish the complicated operation also

without any difficulties.

The Work in Progress (WIP) is reduced, and at a time one cut

garment is given to one operator and so the amount of

inventory is reduced.

Disadvantages

Highly skilled labourers are used, so the cost of labour is high.

The operator is more concerned on the number of pieces

finished rather than the quality of work.

Productivity is less due to lack of specialization.

For long run/bulk quantity of same style is not effective in this

system.

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5.2.2 Progressive Bundle System (PBS) - Batch System

This system is exactly what its name implies, a system whereby the

garments are gradually assembled as they move through successive

sub-assembly and main assembly operations in bundle form. This is the most

commonly used manufacturing system for the sewing room till date. In this

system, the work pieces move in bundles, creating larger inventory,

increasing the space requirement and creating material handling problems.

One of the popular variations of the bundle system is the skill center bundle

system, where the sewing room operations are grouped into sub-assembly

sections. Each sub-assembly section can accommodate style variations to

some extent, giving the system flexibility for style changes. This system is

currently used in a large number of plants. The slow response time of the

bundle system, however, makes it unsuitable for quick response production.

Other flexible and faster ways of physically moving the fabric through the

plant have also been developed through the following types of apparel

manufacturing systems.

The amount of machinery for each operation would be determined

by the output required. A work store is positioned at the start and end of every

section of these buffers and is used to store work received from a preceding

operation, and to hold work completed by that section. Due to these work

stores or buffers, each section is not directly dependent on the preceding

section, but can absorb slight variations in output via the stocks held within

the section. The progressive bundle system, while being somewhat

cumbersome in operation and requiring large quantities of work in progress, is

probably one of the most stable systems with regard to output. Unless there is

serious absenteeism or prolonged special machine breakdowns, most of the

usual hold-ups can be absorbed because of the amounts of work in progress.

Balancing and the changeover to new styles are also somewhat difficult, due

to the amount of work held in reverse.

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When properly managed, the progressive bundle system is versatile

and efficient.

Advantages

High productivity

A high level of labour utilization can be achieved

Training time and costs can be reduced

Individual performance can be monitored and incentives

offered.

Semi-skilled labour can be used, since the operations are

broken into small simple operation. Hence the cost of labour is

very cheap.

The components are moved in bundles from one operation to

next operation, so there is less chance for confusion like, lot

mix-up, shade variation, size variation, etc.

Disadvantages

Machines and operations are organized into sections according

to basic functions, which produce sub components.

Within each sections work is balanced according to time

required for each sub-functions.

Machine investment costs are high.

The system is not very adaptable for short-run production and

frequent style changes, as these require rearrangement of the

workstation.

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It involves high handling costs for bundle handling and

transportation.

It requires a high level of work in progress and therefore a

high capital commitment.

It requires a high level of management skills to arrange the

workflow and decide on the number of operators for each

operation.

5.2.3 Unit Production System (UPS)

The model of Unit Production System (UPS) is shown in

Figure 5.1. This system moves the fabric pieces for one garment on a single

hanger through the factory. A computer balances the line by routing garments

to sewing operators with higher performance and lower inventory

(Albrecht 1989). The garment components are automatically transported from

work station to work station according to pre-determined sequence according

to Albrecht (1989). The work station are so constructed that the components

are present as close as possible to the operator’s left and in order to reduce the

amount of movement required to grasp and position and component to be

sewn. UPS addresses the problem that a bundle system generates, where 80%

of the production operator's time is devoted to material handling. It also helps

to eliminate time spent for labeling and moving fabric pieces. This system

also helps improve quality by spotting the sewing errors sooner, and thus

corrections can be made on them before large quantities of garments are

affected. Another benefit of UPS is lower work-in-process. With this system,

throughput is quicker and the garment can be shipped to the customer sooner

(Albrecht 1989).

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Figure 5.1 Unit production system (Albrecht 1989)

Unit Production Systems (UPS) are good for large garments like

pants, coats, skirts, dresses etc., because large parts are normally difficult to

handle in the conventional way when they are in bundles (Lokiec 1990).

According to Lokiec (1990), under the UPS the parts can be better

prepositioned before they are fed into the machine.

Advantages

1. Bundle handling completely eliminated.

2. The time involved in the pick-up and disposal is reduced to

minimum.

3. Output is automatically recorded, eliminates the operator to

register the work.

4. The computerized systems automatically balance the work

between stations.

5. Up to 40 styles can be produced simultaneously on one

system.

Disadvantage

1. Unit production system requires high investments.

2. The payback period of the investment takes long time.

3. Proper planning is required to be effective.

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5.2.4 Modular Manufacturing System (MMS)

Another system for moving fabric quickly through the factory is

called the Toyota Sewing System (TSS), synchronized, or the more popular

term, Modular Manufacturing System (MPS) as shown in Figure 5.2. The

Modular Manufacturing System is a U shaped layouut holding small group of

machines to complete parts of a garment or a total garment (Albrecht 1989).

According to Albrecht (1989), in a modular layout the number of operators

are less than the number of machines. Each operator is cross trained on two or

more machines and moves from machine to machine to balance the line as

necessary. Albrecht (1989) also suggests that modular manufacturing

provides small manufacturers with short lead times while producing high

quality garments under good management control. Of course, larger

manufacturers can also benefit from it. Quality can be achieved in modular

manufacturing through team work to keep the line balanced or fabric pieces

moving through smoothly. Modular manufacturing means sewing a variety of

garments within a module. To accommodate some garments, machines in the

module are changed rather than trying to fit various garments into the

production line.

Figure 5.2 Modular manufacturing system (Albrecht 1989)

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Modular manufacturing can be compared to the Just - In-Time (JIT)

management system which works toward a zero inventory buffer and total

quality control (Albrecht 1989). According to Albrecht (1989), flexibility via

modular manufacturing is important for a company to remain responsive to

the market. Flexible manufacturing includes the ability to quickly produce

quality products in the quantities needed. The Modular Production System

(MPS) approach is more like a culture, concept or philosophy, rather than a

technology that requires a total company commitment throughout the

organization (Gilbert 1990). Gilbert (1990) suggests that the modular

manufacturing is a process, not a program.

Advantages

Operators can work freely as a team.

All operators are highly skilled in the operation of all the

different machines in one workstation.

In-process inspection stations are built into the line and the

inspector is able to return faulty work via the system to the

operator concerned.

Quality of the garment is very high because the operator

handles the garment in quality conscious manner.

As there are so few garments on the line throughput time is

extremely short, which is the objective of this system.

A typical unit would have eight work stations arranged

around the transport system.

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5.3 IMPORTANCE OF LAYOUT DESIGN

Layout design is one of the key activities that determine the long-

run efficiency of operations. Layout design has numerous strategic

implications because it establishes an organization’s competitive priorities

with regard to the capacity, processes, flexibility and cost as well as quality of

work life, customer contact and image. An effective layout can help an

organization to achieve a strategy that supports differentiation such as cost

reduction, or response (Heizer and Render 2000). The layout must consider

how to achieve the following.

1. Higher utilization of space, equipment, and people.

2. Improved flow of information, material or people.

3. Improved employee morale and safer working conditions.

4. Improved customer/client interaction.

5. Flexibility (whatever the layout is now, it will need to

change).

5.3.1 Assembly Line Balancing

Different line design layouts are all associated with an Assembly

Line Balancing (ALB) problem. Balancing distributes tasks to work stations

and work content per station and variant. Line balancing is divided in areas

depending on layout of the assembly line. To minimize work overload,

sequencing is carried out (Boysen et al 2008). The sequence determines

spreading of material demand and labour utilization at workstations.

Line balancing is usually undertaken to minimize imbalance

between machines or personnel while meeting a required output from the line.

The production rate is indicated as cycle time to produce one unit of the

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product, the optimum utilization of work force depends on the basis of output

norms. The actual output of the individual may be different from the output

norms. Hence the time to operate the system keeps varying. It is, therefore,

necessary to group certain activities to workstations to the tune of maximum

of cycle time at each work station. The assembly line needs to balance so that

there is minimum waiting of the line due to different operation time at each

workstation. The sequencing is therefore, not only the allocation of men and

machines to operating activities, but also the optimal utilization of facilities

by the proper balancing of the assembly line . The process of assembly line

balancing involves three steps (Heizer and Render 2000)

1. Take the units required (demand or production rate) per day

and divide it into the productive time available per day

(in minutes or seconds). This operation gives us what is called

the cycle time. Namely, the maximum time that the product is

available at each workstation if the production rate is to be

achieved.

Pr oduction TimeAvailable per DayCycleTimeUnits Required per Day

2. Calculate the theoretical minimum number of workstations.

This is the total task duration time (the time it takes to make

the product) divided by the cycle time. Fractions are rounded

to the next higher whole number.

n

i 1

Timefor Task iMinimum Numer of WorkstationsCycleTime

Where n is the number of assembly tasks.

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3. Balance the line by assigning specific assembly tasks to each

workstation. An efficient balance is one that will complete the

required assembly, follow the specified sequence, and keep

the idle time at each work stations to a minimum.

5.3.2 Takt Time

Takt is a German word for a pace or beat, often linked to

conductor’s baton. Takt time is a reference number that is used to help match

the rate of production in a pacemaker process to the rate of sales. This can be

formulated as below (Rother and Harris 2001).

Available Work Time perShiftTakt TimeCustomer Order Quantity perShift

Takt time can be defined as the rate at which customers need

products i.e. the products should be produced at least equal to takt time to

meet the customer demand. Takt time works better when customer demand is

steady and clearly known; but if the customer demand varies on the daily

basis then it is difficult to calculate the takt time as well as balance the

production facility according to varying takt time. So if the orders are varying

every day the information of actual shipments (not orders) should be gathered

for last few months or years and takt time for the particular product should be

calculated. In this way, the production can be balanced to meet changing

customer demand.

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5.3.3 Cycle Time

Cycle time is defined as how frequently a finished product comes

out of our production facility (Heizer and Render 2000). Cycle time includes

all types of delays occurred while completing a job. So cycle time can be

calculated by the following formula.

TotalCycleTime ProcessingTime Set UpTime WaitingTime MovingTimeInspectionTime ReworkTime OtherDelaystoCompletetheJob

To meet customer demand or monitor productivity the cycle time

and takt time should be balanced in parallel. The higher cycle time than takt

time may result in late delivery and customer dissatisfaction whereas shorter

cycle time than takt time may cause excess inventory or excess use of

resource which is considered as process waste.

5.3.4 Cycle time Vs Takt time

The cycle time is the time it takes for one unit of product to go

through the manufacturing process. The Takt time is the rate of customer

demand. Ideally, for a lean process, the cycle time of each step should be

equal to the Takt time. In other words, the product should be produced at the

rate that the customer is demanding the product. Producing faster than the

Takt time creates overproduction; while producing slower than the Takt time

leads to bottlenecks. The Takt time should be used to determine the rate of

production.

For example Figure 5.3 below shows the cycle times of each step in

the assembly operation process. The Takt time was found to be 96 seconds.

One can see the discrepancies between the cycle times and Takt time for each

step in the process. Earlier steps cycle times were found to be much shorter

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than the Takt time, while the later steps cycle times were longer than the Takt

time. These discrepancies led to the build-up of WIP inventory.

Figure 5.3 Comparison of cycle time Vs talk time

5.3.5 Setup time

Setup time is defined as the time it takes to go from the production

of the last good piece of a prior run to the first good piece of a new production

run (Trvino 1993). Setup cost is a non-value added cost; that explains why

many companies look to reduce the setup time. Trvino (1993) developed a

total cost function, which can utilize the setup data. Recommendations were

made to reduce the setup, and the information is applied to the total relative

cost function to decide if setup time is economically feasible. A general

equation was derived expressing relationship between percentage setup time

reduction and required investment.

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Lee, et al (1994) applied goal programming to provide insight into

setup time and lot size reduction. The objective of their model was to reduce

production length, WIP cost and setup cost minimization. Rajendran and

zeigler (1997) considered static flow shop with sequence dependent setup

time of jobs. The main objective of their heuristic is to minimize the sum of

weighted flow time in a sequence dependent setup time scenario. Genreau

et al (2001) presented a heuristic for the multiprocessor scheduling problem

with sequence dependent setup times. The goal of his algorithm was to

minimize overall processing time by determining assignments of jobs to

machine and cyclic sequence of jobs on each machine

5.4 METHOD STUDY

Method study focuses on how a task can be accomplished. Whether

controlling a machine or making or assembling components, how a task is

done makes a difference in performance, safety, and quality. Using

knowledge from ergonomics and methods analysis, methods engineers are

charged with ensuring quality and quantity standards which are achieved

efficiently and safely. Method analysis and related techniques are useful in

office environments as well as in the factory. Methods techniques are used to

analyze the following (Heizer and Render 2000)

1. Movement of individuals or material. Analysis for this is

performed using flow diagrams and process charts with

varying amounts of detail.

2. Activity of human and machine and team activity. Analysis

for this is performed using activity charts (also known as man-

machine charts and crew charts).

3. Body movement (primarily arms and hands). Analysis for this

is performed using micro-motion charts.

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5.4.1 Labor Standards and Work Measurements

Effective operations management requires meaningful standards

that can help a firm to determine the following (Heizer and Render 2000)

1. Amount of labor contribution for any product (the labor cost).

2. Staffing needs (how many people will it take to meet required

production).

3. Cost and time estimates prior to production (to assist in a

variety of decisions, from cost estimates to make or buy

decisions).

4. Crew size and work balance (who does what in a group

activity or on an assembly line).

5. Expected production (so that both manager and worker know

what constitutes a fair day’s work).

6. Basis of wage-incentive plan (what provides a reasonable

incentive).

7. Efficiency of employees and supervision (a standard is

necessary against which to determine efficiency).

Properly set labor standards represent the amount of time that it

should take an average employee to perform specific job activities under

normal working conditions. The labour standards are set in by historical

experience, time studies, and predetermined time standards and work

sampling.

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5.5 TIME STUDY

The classical stopwatch study, or time study, originally proposed by

Federic Taylor in 1881, is still the most widely used time study method. The

time study procedure involves the timing of a sample of worker’s

performance and using it to set a standard. A trained and experienced person

can establish a standard by following these eight steps (Heizer and Render

2000).

1. Define the task to be studied (after methods analysis has been

conducted).

2. Divide the task into precise elements (parts of a task that often

takes no more than a few seconds).

3. Decide how many times to measure the task (the number of

cycle of samples needed).

4. Record elemental times and rating of performance.

5. Compute the average observed cycle time. The average

observed cycle time is the arithmetic mean of the times for

each element measured, adjusted for unusual influence for

each element.

Sumof theTimesRecorded to PerformEach TaskAverageObservedCycleTimeNumber of CycleObserved

6. Determine performance rating and then compute the normal

time for each element.

NormalTime (AverageObserved CycleTime) (Performance ratingFactor)

7. Add the normal times for each element to develop a total

normal time for each task.

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8. Compute the standard time in the form of Standard minute

value (SMV). This adjustment to the total normal time

provides allowances such as personal needs, unavoidable

work delays and worker fatigue.

Total NormalTimeStan dard Allowable Minutes (SMV)1 Allowance Factor

Personal time allowances are often established in the range of 10%

to15% of total time, depending upon nearness to rest rooms, water fountains,

and other facilities. Delay allowances are often set as a result of the actual

studies of the delay that occurs. Fatigue allowances are based on the growing

knowledge of human energy expenditure under various physical and

environmental conditions. The major two disadvantages of this method are;

first they require a trained staff of analysts and secondly the labour standards

cannot be set before tasks are actually performed.

As per the Lean principles, any form of allowance is non value

added time though it is unavoidable. In this context up to cycle time

measurement is the value added time. Moreover in cycle time, the exactly

needle moves is the value added time, even though we cannot skip out the

material handling time though this a kind of non value added time which is

technically called necessary non value added time. SMV would be used to

balance the product line in progressive bundling time. But in Lean production

system cycle time is the factor that would be considered for product line

balancing.

5.5.1 Predetermined Time Standards

Predetermined time standards divide manual work into small basic

elements that already have established times (based on very large samples of

workers). To estimate the time for a particular task, the time factors for each

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basic element of that task are added together. Developing a comprehensive

system of predetermined time standards would be prohibitively expensive for

any given firm. Consequently, a number of systems are commercially

available. The most common predetermined time standard is methods time

measurement (MTM), which is the product of the MTM association (Heizer

et al 2000 ).

Predetermined time standards are an outgrowth of basic motions

called therblings. The term "therblig" was coined by Frank Gilbreth.

Therbligs include such activities as select, grasp, position, assemble, reach,

hold, rest and inspect. These activities are stated in terms of Time

Measurement Units (TMUs), which are each equal to only 0.00001 hour or

0.0006 minutes. MTM values for various therbligs are specified with the help

of detailed tables. Predetermined time standards have several advantages over

direct time studies. First, they may be established in laboratory environment,

where the procedure will not upset actual production activities. Second,

because the standard can be set before a task is actually performed, it can be

used for planning. Third, no performance ratings are necessary. Fourth,

unions tend to accept this method as fair means of setting standards. Finally,

predetermined time standards are particularly effective in firms that do

substantial numbers of studies of similar tasks.

5.6 SUMMARY

This chapter reviewed the process value chains in garment

production system and the need of lean process implementation to the

garment industry is further understood. Subsequently various production

system involved in garment production are analyzed .With this review the

suitable layout is understood for lean implementation and various other

advantage and disadvantages of Production systems are also analyzed. The

choice of best apparel production system will depend on the product and

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policies of the company and on the capacities of manpower. In addition to

this, Method study, time study and predetermined motion cycle are further

reviewed, since these tools are used for method analysis and time analysis of

various garment operations.