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The topic of reducing cycle time

Chapter II

Literature Review

This chapter reviews old research and theories that cite the subject of cut downing rhythm clip, which is relevant to tilt constructs and simulation. The subject of this chapter are below.

  1. Product rhythm clip betterment
  2. Principles of thin
  3. Simulation Modeling
  4. Review literature
  5. Research Frame work

In the past, most research focused on the development of dispatching and releasing regulations to better rhythm clip.

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With less limitation on the equipment, batch size decrease would be another alternate to shorten rhythm clip which considered apparatus clip and capacity restraints to work out the batch size job. Some constructs use thin fabrication to extinguish waste and non-value-added clip. Some bookmans used simulation methods to make the rhythm clip analysis by uniting simulation and computing machine algorithms to seek for the batch size for each single merchandise in a multi-product environment. Most of the past surveies sing batch size concentrated on traditional fabrication environments, with fixed demands and production rates. The primary end of this model was to minimise the entire production rhythm clip.

2.1 Product rhythm clip betterment

Cycle clip decrease involves placing and implementing more efficient ways to make things. Reducing rhythm clip requires extinguishing or cut downing non-value-added activities, which is defined as any activities that do non add value to the merchandise.

Examples of non-value-added activities in which rhythm clip can be reduced or eliminated include fix due to defects, machine set-up, review and agenda holds. Explained by Kivenko ( 1994 )

1.2.1 The component of fabricating lead clip can be farther divided into:

  1. Queue clip before processing.
  2. Put up clip.
  3. Run ( treating ) clip.
  4. Waiting clip after processing.
  5. Move clip.

There is an of import follow-on consequence to cut downing the frequence of set-ups. Just as presenting computing machine integrated fabricating removes operator engagement and operator accomplishments wasting ( Coble and Bohn, 1997 ) , diminishing set-up frequence drives set-up proficiency down. The danger is an of all time downward spiral of cut downing set-up frequence and increasing batch size. Even when the operator component is reduced or replaced in “ flexible ” fabricating systems, the public presentation is in some instances worse than the manual system. Rather than bring forthing more assortment of lower volume, these systems frequently produce less assortment of higher volume ( Meyer, 1993 ) . That is to state, set-up clip is reduced and batch size increased. ( Youngman, 2003 )

2.1.2 Bottleneck

A constriction is the resource that constrains or limits the end product of the overall operating unit. In a line flow procedure design, the constriction is the procedure phase with the highest rhythm clip. In a occupation store or batch procedure design, the constriction can be more hard to place. Certain pieces of equipment and/or specific people may be used at multiple procedure phases. ( Prasad, 1995 )


Page ( 2003 ) explained “ batch ” is the term usually used for the measure of a peculiar merchandise to be made all in one spell. An full batch of work might take several yearss to finish. Traditionally, this would affect the batch traveling through one operation at a clip, and it would n’t be allowed to travel to the following operation until the full batch measure had gone through the current phase of processing. The batch is kept together like this to let the inspector a opportunity to compare the constituents from the beginning, center and terminal of the batch to specification all at the same clip. It is easy to maintain WIP on procedure.

Schragenhein and Dettmer ( 2000 ) said that increasing batch size affects work-in-process stock list degrees, fabricating lead clip, local and planetary safety clip issues, and finished goods stock degrees by increasing them. Increased batch size affects quality and throughput by diminishing them. However, good thought-out alterations to critical batch sizes can enormously alter these parametric quantities within a procedure. It does so non by rushing up machine or procedure clip, but by cut downing idle clip when work sits on the workshop floor ( or office desk, or computing machine difficult disc ) between procedure points after cut down batch size found that smaller batches can travel much faster.

Batch size issues at a formal degree have tended to be treated as a trade-off analysis or optimisation between set-up or ordination costs, storage and retention costs, and stock out costs ( Jaber and Bonner, 1996 ) . The attendant optimum batch size is known as the Economic Order Quantity or EOQ. ( Trigeiro, Thomas and Jo, 1989 ) . However, while most everyone knows about Economic Order Quantity, really few people of all time bother to cipher it. There is a far more cardinal driver to batch size. The cardinal driver is cut downing “ non-productive ” set-up clip, and maximising “ productive ” processing or machine clip. There are normally really strong measuring inducements – timesheets – which cause workshop floor forces to minimise set-up clip and maximise procedure clip. The easiest manner to make this is to diminish the frequence of set-ups by increasing the batch size. There is, nevertheless, another more elusive and less frequently expressed driver at work every bit good. ( Spearman, 1996 )

Some considerations when taking the figure for batch size: Koskela ( 1992 )

  • If the figure is excessively big, the sum of queue infinite taken up on both terminals of the nexus becomes inordinate. Messages take up queue infinite when they are non committed, and can non be removed from waiting lines until they are committed.
  • If there is likely to be a steady flow of messages, you can better the public presentation of a channel by increasing the batch size. However, this has the negative consequence of increasing restart times, and really big batches may besides impact public presentation.
  • If message flow features indicate that messages arrive intermittently, a batch size of 1 with a comparatively big disconnect clip interval may supply better public presentation.
  • Even though liable messages on a fast channel do non wait for a sync point, they do lend to the batch-size count.

Thin rules can be used to better productiveness driven by workers, based on their cognition of the work and equipment, with the end of increasing value added work ( Holly and Gaskins, 2004 )

2.1.4 Cycle clip is linked to other facets of Thin

  1. Continuous betterment leads to step betterments in rhythm clip one time takt times come down for all stairss.
  2. Standardized work is a cardinal to doing rhythm clip work on the floor.

2.2 Principles of Lean

Lean was started at Toyota because they wanted a clear definition of client value. It acknowledges that all value is created by some procedure. Therefore, Lean can develop procedures that are waste or “ muda ” is defined by Shoichio Toyoda, laminitis of Toyota, as “ anything other than the minimal sum of equipment, stuffs, parts, infinite and worker ‘s clip which are perfectly indispensable to add value to the merchandise. ” Lean is a methodological analysis that is used to increase velocity and cut down the cost of any procedure by extinguishing waste. A Thin enterprise is to give a simple manner of understanding the impact of attempts through be aftering betterment activities, look intoing the consequences and doing appropriate accommodations. In add-on, Lean tools aid to find the fiscal impact of betterments such as increasing stock list bends, cut downing work-in-process and cut downing changeover clip. ( Ohno, 1990 )

The Toyota Production System ( TPS ) identifies seven signifiers of waste in fabrication, which Ohno calls “ The Seven Deadly Wastes. ” The wastes can be classified as follows:

  1. Overproduction: doing more than needed
  2. Inventory: material puting around ( frequently a symptom of another waste )
  3. Defects: Time spent repairing defects, including defect that get thrown off and the clip make the merchandise right
  4. Waiting: Waiting clip for making something..
  5. Over processing: devising to a higher quality criterion than expected by the client.
  6. Transportation system: extra moving of stuff.
  7. Gesture: inefficient people motion.

Thin Manufacturing is an operational scheme oriented toward accomplishing the shortest possible rhythm clip by extinguishing waste. It is derived from the Toyota Production System and its cardinal push is to increase the value-added work by extinguishing waste and cut downing incidental work. The technique frequently decreases the clip between a client order and cargo, and it is designed to radically better profitableness, client satisfaction, throughput clip, and employee morale. ( Michael and Kentaro, 1998 )

2.2.1 Features of a Leans procedure

The features of Lean procedure aid to flux of procedure run every bit continuously as possible with a rapid rhythm clip. The precise description of each work station activity stipulating rhythm clip, take-time, the work sequence of specific undertakings, and the minimal stock list of parts on manus needed to carry on the activity ( Stenzel, 2007 ) .

The features of thin procedures are:

  • Make to order
  • Single-piece production
  • Just-In-Time materials/pull programming
  • Short rhythm times
  • Quick conversion
  • Continuous flow work cells
  • Compressed infinite
  • Multi-skilled employees
  • High first-pass outputs with major decreases in defects

2.2.2 Thin tools

Thin fabrication tools can decide many jobs in production lines. In This chapter we will concentrate on thin tools that concern this survey by utilizing standard work and rapid conversion. Standard Work: Definition

The definition of standard work was explained by Jeff Hajek ( 2009 ) a common term given to any aggregation of clip value. The format of the information is as tabular arraies or worksheets. The informations can be utilized in concurrence with deliberate rhythm clip but can non make up one’s mind the operating parametric quantities for a works supplying a thin fabrication environment. Standard Work has three chief constituents:

  1. It is balanced to the takt clip.
  2. It specifies standard work-in-process ( WIP ) .
  3. It defines the sequence of operations for a individual operator.

The precise description of each work activity stipulating rhythm clip, undertaking clip, the work sequence of specific undertakings, and the minimal stock list of parts on manus needed to carry on the activity. Henry Ford said that “ If you think of standardisation as the best that you know today, but which is to be improved tomorrow – you get someplace. But if you think of criterions as confining, so advancement Michigans. ”

Somnath Kundu ( 2008 ) studied the application of design mechanization to cut down rhythm clip of hydro turbine design. Because of the rapid growing in the demand for electricity and increased recognition hazards in the fiscal markets, there is a strong concern deriver? To cut down the design to committee rhythm clip of procedure. The first measure that is of import is standardisation. The key to success for any design mechanization undertaking is standardisation: The standardisation of the merchandise construction and design pattern and automatizing the same has given the user an border over its rivals.

Front Line Professionals ( 2001 ) : said that Standardized work is one of the most powerful thin tools. Professionals that do the work on the floor can frequently outdo papers the current best patterns. Establishing standardised work relies on

Roll uping and entering informations as it really happens. Such standardised patterns serve as the baseline for kaizen or uninterrupted betterment. As the criterion is improved, the new criterion becomes the baseline for farther betterments, and so on. Standardizing the work adds subject to the civilization, an component that is often neglected but indispensable for thin transmutation. Standardized work besides supports audits, promotes job resolution, and involves squad members in developing safety guards ( poka-yokes ) . All of the standardisation attempts need to be surrounded and embedded in the civilization of the thin organisation. Takt clip: Definition

Takt Time comes from a German word ‘takt ‘ significance beat. The definition of Take clip was explained by Jon Miller ( 2003 ) is a 1 of the cardinal rules in a Thin Enterprise. Takt Time sets the ‘beat ‘ of the organisation in synch with client demand. Takt Time balances the work load of assorted resources and identifies constrictions.

Takt Time is a simple construct, yet counter-intuitive, and frequently baffled with rhythm clip or machine velocity. In order for fabricating cells and assembly lines to be designed and built Lean, a thorough apprehension of Takt Time is required. Takt Time is used to fit the gait of work to the mean gait of client demand. Takt is non a figure that can be measured and is non to be mistaken with rhythm clip, which is the clip it takes to finish one undertaking. Cycle clip may be less than, more than, or equal to Takt Time.

The expression for Takt clip is:

Takt clip = Net Available Time per Day Customer Demand per Day Rapid alteration overtime

SMED ( individual minute exchange of dice ) is a theory and tools set of techniques that make it possible to put up or alteration overtime equipment. Change overtime is the clip from when the last goods item/piece comes off a machine or out of a measure until the first good item/piece of the following service/product is made. Changeover clip includes set up, warm up, test tally, accommodation, first-piece review, etc. Changeover Time is the sum of clip it takes to alter over equipment/programs/ files/documents from the terminal of the old measure to the beginning of the current measure. Changeover is the sum of Set-up clip and Run-up clip. Changeover can be the clip and do the difference between a good merchandise and a good merchandise at the right velocity. If can cut down alteration overtime, can cut down rhythm clip of procedure as good. Jaikumar ( 1986 ) while Dave ( 1996 ) need to cut down machinery alteration overtime because have two biggest wastes are overrun and WIP waiting lines. There is one “ existent ” issue that must be overcome in order to greatly cut down batch size without increasing cost. The constituent of alteration overtime following list:

  1. Internal apparatus takt that can be performed merely while the machine is shut down.
  2. External set up takt that can be performed while the machine is running Effectss of alteration overtime Decrease

  1. Batch size can be reduced.
  2. Aid to cut down stock list.
  3. Increase the capacity on constriction equipment.
  4. Aid to extinguish the apparatus bit

2.2.3 Traditional V. Thin Fabrication

A cardinal difference in Thin Manufacturing is that it is based on the construct that can be driven by existent client demand. Alternatively of bring forthing what you hope to sell ; Lean Manufacturing can bring forth what your client wants with shorter lead times. Alternatively of forcing merchandise to market, it ‘s pulled at that place through a system that ‘s set up to rapidly react to client demand.

2.2.3 Traditional V. Thin Fabrication

A cardinal difference in Thin Manufacturing is that it is based on the construct that production can and should be driven by existent client demand. Alternatively of bring forthing what you hope to sell ; Lean Manufacturing can bring forth what your client wants with shorter lead times. Alternatively of forcing merchandise to market, it ‘s pulled at that place through a system that ‘s set up to rapidly react to client demand.

2.3 Simulation Modeling

Simulation is the dynamic representation of a existent system by a computing machine theoretical account which behaves in the same mode as the system itself. In the fabrication industry, simulation represents the dynamic fabrication procedure in the computing machine theoretical account, and shows diagrammatically and over fake clip the effects of a possible scenario to back up the decision-making procedure. Bielunska and Gun ( 2002 ) .A conventional information flow of fabricating simulation is shown in Figure 2-4.

Manufacturing simulation converts the elaborate operational informations into the direction information. It enables assorted scenarios to be tested without big investing on puting up a pilot line or interrupting the production. It eliminates the common job in fabricating industry: constrictions

2.3.1 Application Areas of Manufacturing Simulation.

In the fabrication companies, directors and applied scientists are able to measure the public presentation of fabricating procedure under several different sets of status to place the proper layout and operational policy. That can lend to accomplish better production public presentation such as high throughput, short lead clip, low work-in-process ( WIP ) , and high resource use. Case of the application of fabricating simulation by the current users are:

Implementing new fabrication construct

Imperfect design from the debut of this construct can do the production end product decrease ; nevertheless, the possible jobs can be identified by simulation. The re-layout undertaking of National Semiconductor Malaysia studied in one procedure Tung, Wang and Sun ( 1995 ) by utilizing simulation is the good case. Before application of new layout, the kineticss of simulation benefit indentified the possible jobs, helped the affecting section to understand the procedure of new layout, and saved 5 % on the capital investing.

Bettering bing procedure; the bing procedure demand to be adapted to manage the new demand when new merchandises are launched or demand pattern becomes different from the yesteryear. Simulation is really effectual to analyze the impact of alteration to smooth the alteration. Motorola Malaysia was reported the economy to be US $ 250,000 equivalent of capacity addition within one twelvemonth after the company usage simulation to analyze the merchandise mix and batch size to better the apparatus clip and machine aid clip Yong ( 1994 ) .

Reducing Work-In-Process ( WIP ); a high WIP is frequently built because of unexpected dislocations, taking to a high stock list cost, slow stuff flow, and inflexible merchandise mix. Simulation is used to analyse the sensitiveness of WIP degrees. Flextronics Singapore used simulation to analyze the most economical manner to cut down WIP and the consequence reported at more than 50 % decrease, significantly improved others company public presentation such as stock list, bringing public presentation Chang and Kum ( 1994 ) .

Merchandise timing: Simulation is superb for make up one’s minding the order lading sequence and operation timing. It was arranged a systematic direction to the merchandise store degree. It is easy to happen this simulation on a day-to-day footing to bring forth timing instructions to the operations of PCB Manufacturing CIMTEX ( 1994 ) at Digital Singapore. These besides greatly reduced WIP and stabilized operations.

2.3.2 Core propensity construct and Simulation

To set up the direction acquisition by following a description of how simulation is being usage since it increasing larning perceptual experience. Along prognostic simulation tilting theoretical account. Learning period is greatly reduced and eliminates waste. Majority companies have been utilizing simulation to happen solution to making value or merchandise betterment procedure. Simulator procedure created an thought tool for developing alternate procedure scenarios to help the public presentation of current operation inefficiencies. Furthermore, the function theoretical account to extinguish through the atilt execution.

2.4 Review of related surveies.

2.5 Researching Model Work:

The nucleus constructs of the theoretical account are a type of intermediate theory that attempt to link to all facet of enquiry ( e.g. , job probe, intent, literature reappraisal, methodological analysis informations aggregation and analysis ) . This theoretical account is able to make the maps that give coherency to empirical enquiry. Due to the theoretical accounts are possible similarity to empirical enquiry, they take different signifiers depending upon the research inquiry or job in figure 2-5.

2.5.1 The constituent of the rhythm clip determination elements:

  • Processing clip: timing that the thing is being worked on by an operation. To analyzing this affair earnestly by utilizing tool ; a stop watch from camera – following unit being processed by one operator – all the manner through the procedure ( or sub-process ) .
  • Waiting clip: timing between sub-process that the thing gets shuffled around or sits around waiting for person to work on it. Equally good as cognizing “ Waiting & A ; Transportation Time ” or “ Inventory/Transpiration Time. In this instance have consequence from waiting clip in each work station and wait clip of portion of auto theoretical account.
  • Change overtime ; the sum of clip takes to alter over the devising or plan from the terminal to old measure to the current measure. If you have to takes ever will consequence with entire rhythm clip.
  • Since a batch size of one has been unpracticed the end is in improve productiveness sporadically. The finally reduces stock list carry costs, work in advancement, and rhythm clip. Besides this enabling the company operates productively at lower borders.

2.5.2 The significance of component of the finding in rhythm clip decrease.

  • Productiveness: From analyzing shown manner to better productiveness by cut down rhythm clip in order to protect loss sale, cut down cost in fabrication and increase client satisfaction.
  • A cost incurred by a concern when it is unable to make full an order and must finish it subsequently. A back order cost can be distinct, as in the cost to replace a specific piece of stock list, or intangible, such as the effects of hapless client service.
  • On clip deliver: one of the ground why is company demand to cut down rhythm clip. The existent measuring will be the per centum of units you produce that run into your client ‘s deadline. Is n’t it interesting that it has to make with the client ‘s deadline.

In this chapter, the research worker has discussed relevant constructs in rhythm clip decrease by usage simulation to optimal batch size every bit good as suggesting the construct model for this research undertaking. In the following chapter, the research worker will explicate the methodological attack this undertaking.

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