Method Study in Operations Management

Objec­tives and impor­tance#

The main objec­tive of method study is to develop the sim­plest, safest, quick­est and most eco­nom­i­cal way of doing a job. Speed alone is not the goal; the aim is bet­ter over­all per­for­mance.

Spe­cific objec­tives#

• elim­i­nate unnec­es­sary work and move­ment
• improve processes, pro­ce­dures and the flow of work
• improve the lay­out of the fac­tory, shop or work­place
• improve the design of equip­ment and the use of mate­ri­als, machines and labour
• reduce fatigue and improve work­ing con­di­tions and safety
• raise pro­duc­tiv­ity, improve qual­ity and lower cost

What a poor method costs#

A poor method causes need­less move­ment, extra time, fatigue, machines wait­ing for work, higher cost and low out­put. A good method reduces waste, smooths the flow of work, reduces effort, improves safety and raises out­put. Because the gains come from reor­gan­is­ing work rather than buy­ing equip­ment, method study is often called work sim­pli­fi­ca­tion.

Method study within work study#

Work study has two parts: method study, which finds the best way, and work mea­sure­ment, which finds the stan­dard time for that way. Method study is nor­mally done first, because tim­ing a poor method only fixes its waste into the stan­dard.

When method study is use­ful#

Method study is use­ful both to improve old meth­ods and to design new ones. Typ­i­cal sig­nals are:

• high pro­duc­tion cost or low out­put
• exces­sive move­ment of work­ers or mate­ri­als, or a poor lay­out
• fre­quent delays, bot­tle­necks or idle machines
• exces­sive han­dling of mate­ri­als
• work that causes fatigue, com­plaints or acci­dents
• intro­duc­tion of a new prod­uct or process

When choos­ing, the ana­lyst weighs three sets of con­sid­er­a­tions: eco­nomic (is the sav­ing worth the study?), tech­ni­cal (is exper­tise avail­able to improve it?) and human (how will peo­ple react to the change?).

Steps in method study (SREDIM)#

Method study fol­lows a log­i­cal sequence, often remem­bered as SREDIM. The Inter­na­tional Labour Office's clas­sic treat­ment also lists Define (write down the new method as a stan­dard prac­tice) and Eval­u­ate (com­pare results with the old method), which fit between Develop and Install.

1. Select#

Choose the job or process to study. Pri­or­ity goes to jobs where cost is high, delays are fre­quent, motion is exces­sive, com­plaints are com­mon, out­put is low or safety is poor.

2. Record#

Record all rel­e­vant facts about the present method, gath­er­ing enough data of good qual­ity and quan­tity to act as the basis for exam­i­na­tion: the sequence of steps, worker move­ments, machine use, dis­tances trav­elled, mate­r­ial flow, times and work­place arrange­ment. No improve­ment is pos­si­ble with­out clear facts, and record­ing tools are described below.

3. Exam­ine#

Exam­ine every recorded step crit­i­cally using the ques­tion­ing tech­nique. The pri­mary ques­tions chal­lenge each activ­ity:

This is the most ana­lyt­i­cal step. It exposes unnec­es­sary steps, dupli­cated work, bad lay­out, avoid­able motion and poor sequence.

4. Develop#

Develop the most prac­ti­cal, eco­nom­i­cal and safe method, tak­ing all cir­cum­stances into account. The ana­lyst applies four prin­ci­ples, in this order:

• Elim­i­nate the step alto­gether if it adds no value.
• Com­bine steps where pos­si­ble, for exam­ple inspect­ing while assem­bling.
• Rearrange the sequence for bet­ter flow and less back­track­ing.
• Sim­plify what remains with bet­ter tools, jigs, fix­tures or lay­out.

5. Install#

A good method has no value until it is used. Instal­la­tion needs man­age­ment approval, worker train­ing, rear­rang­ing the work­place, new writ­ten instruc­tions, super­vi­sor sup­port and often a trial run.

6. Main­tain#

Check reg­u­larly that the improved method is still fol­lowed, because peo­ple may drift back to old habits when super­vi­sion is weak. Main­te­nance means ver­i­fy­ing com­pli­ance, mon­i­tor­ing results, mak­ing small cor­rec­tions and keep­ing the new stan­dard up to date.

Record­ing tech­niques#

Method study relies on charts and dia­grams that make the present method vis­i­ble.

Process chart sym­bols#

Process charts use five stan­dard sym­bols, orig­i­nally based on those of the Amer­i­can Soci­ety of Mechan­i­cal Engi­neers (ASME):

Charts#

• Out­line (oper­a­tion) process chart: shows only the main oper­a­tions and inspec­tions, giv­ing an over­all pic­ture of a process.
• Flow process chart: shows all five activ­i­ties in sequence, with dis­tances and times. It can be drawn from the point of view of the worker, the mate­r­ial or the equip­ment.
• Two-handed (left-hand, right-hand) process chart: records what each hand does at a work­place, use­ful for bench assem­bly.
• Mul­ti­ple activ­ity chart: shows the activ­i­ties of sev­eral work­ers or machines on a com­mon time scale, reveal­ing idle time.
• SIMO chart: a simul­ta­ne­ous motion cycle chart that records therbligs of both hands from film or video, used in micro­mo­tion study.

Dia­grams#

• Flow dia­gram: a scale draw­ing of the work­place show­ing the path of move­ment; it reveals back­track­ing, cross­ing paths and long travel.
• String dia­gram: a scale plan on which a thread traces each move­ment, so the length of thread mea­sures the total dis­tance trav­elled. It suits irreg­u­lar move­ments such as those of a store­keeper.
• Travel chart: a table of the num­ber of moves between each pair of work cen­tres, used for lay­out plan­ning.
• Tem­plates and mod­els: two- or three-dimen­sional rep­re­sen­ta­tions used to test lay­outs before mov­ing equip­ment.

Worked exam­ple: present and pro­posed method#

Sup­pose a small fur­ni­ture unit (hypo­thet­i­cal fig­ures) records the han­dling of a table top from cut­ting to despatch on a mate­r­ial-type flow process chart. The sum­mary is:

The pro­posed method moves the drilling machine next to the saw (elim­i­nat­ing two trans­ports), com­bines one inspec­tion with sand­ing, and sched­ules the pol­ish so the tops no longer wait.

Step 1: per­cent­age sav­ing in dis­tance.

$$\displaystyle \frac{62 - 24}{62} \times 100 = \frac{38}{62} \times 100 = 61.3\%$$

Step 2: per­cent­age sav­ing in time.

$$\displaystyle \frac{18.5 - 11.0}{18.5} \times 100 = \frac{7.5}{18.5} \times 100 = 40.5\%$$

Step 3: out­put per 8-hour shift (480 min­utes).

$$\displaystyle \text{Present} = \frac{480}{18.5} = 25.9 \approx 25 \text{ units} \qquad \text{Proposed} = \frac{480}{11.0} = 43.6 \approx 43 \text{ units}$$

(Only com­plete units count, so the fig­ures are rounded down.)

Step 4: labour cost per unit. If the labour cost of the crew is ₹4 per minute, the present method costs $18.5 \times 4 = 74$ rupees per table top and the pro­posed method costs $11.0 \times 4 = 44$ rupees, a sav­ing of ₹30 per unit. At 43 units a shift, that is $43 \times 30 = 1{,}290$ rupees saved per shift.

Prin­ci­ples of motion econ­omy#

Method study is closely linked with motion econ­omy, which reduces unnec­es­sary body move­ment and makes use­ful move­ment eas­ier. The prin­ci­ples, devel­oped from the Gilbreths' work, fall into three groups.

Use of the human body#

• both hands should begin and end their motions together and should not be idle at the same time
• arm motions should be sym­met­ri­cal and in oppo­site direc­tions
• use the low­est body move­ment that will do the job (fin­gers before wrist, wrist before arm)
• use momen­tum and smooth, curved motions rather than sud­den changes of direc­tion

Arrange­ment of the work­place#

• keep a def­i­nite, fixed place for every tool and mate­r­ial
• place tools and mate­ri­als within the nor­mal reach area and in the order of use
• use grav­ity-feed bins and drop deliv­er­ies
• pro­vide good light­ing and a chair and bench of the right height

Design of tools and equip­ment#

• use jigs, fix­tures or foot-oper­ated devices to free the hands
• com­bine two or more tools where pos­si­ble
• design han­dles and levers to suit the hand and give max­i­mum advan­tage

Method study and lay­out#

Many method prob­lems are caused by lay­out: tools far away, mate­ri­als mov­ing back­wards, badly arranged machines and cross­ing paths. Flow and string dia­grams reveal these, and method study improves lay­out by short­en­ing travel, improv­ing the sequence, reduc­ing con­ges­tion and smooth­ing flow. The table-top exam­ple shows how mov­ing one machine removed two trans­ports.

Appli­ca­tions#

Man­u­fac­tur­ing#

Assem­bly work, mate­r­ial han­dling, machine load­ing, inspec­tion flow, tool arrange­ment, work­place lay­out and pack­ing. In a fur­ni­ture fac­tory, for instance, method study can cut the move­ment between cut­ting, drilling and assem­bly sec­tions.

Ser­vices#

Hos­pi­tals can reduce patient move­ment between depart­ments, banks can cut the paper­work steps in loan pro­cess­ing, offices can sim­plify file flow, and retail stores can redesign billing coun­ters.

Advan­tages and lim­i­ta­tions#

Con­di­tions for suc­cess#

• man­age­ment sup­port and ade­quate resources
• worker coop­er­a­tion and par­tic­i­pa­tion in sug­gest­ing improve­ments
• accu­rate obser­va­tion and record­ing
• prac­ti­cal, afford­able improve­ments
• train­ing after the change and fol­low-up after instal­la­tion

Method study should be intro­duced as a way of improv­ing the work, not of crit­i­cis­ing work­ers.

Key terms#

Method study

Sys­tem­atic record­ing and crit­i­cal exam­i­na­tion of exist­ing and pro­posed ways of doing work to develop bet­ter meth­ods.

SREDIM

Select, Record, Exam­ine, Develop, Install, Main­tain: the steps of method study.

Ques­tion­ing tech­nique

Ask­ing what, where, when, who and how, and why each time, to chal­lenge every activ­ity.

Flow process chart

A chart show­ing the sequence of oper­a­tions, trans­ports, inspec­tions, delays and stor­ages, with dis­tances and times.

Flow dia­gram

A scale draw­ing of the work­place show­ing the route fol­lowed by mate­r­ial or work­ers.

String dia­gram

A scale plan on which a thread traces move­ments so that total dis­tance can be mea­sured.

Motion econ­omy

Prin­ci­ples for reduc­ing unnec­es­sary body move­ments and fatigue at the work­place.

Therblig

A basic ele­ment of man­ual motion, such as reach, grasp or release, used in micro­mo­tion study.

Work sim­pli­fi­ca­tion

Another name for method study, stress­ing the removal of unnec­es­sary work.

Com­mon ques­tions#

What are the steps of method study?#

Select, Record, Exam­ine, Develop, Install and Main­tain (SREDIM). Some texts add Define and Eval­u­ate. Each step builds on the one before, and the ques­tion­ing tech­nique is applied dur­ing Exam­ine.

What is the dif­fer­ence between a flow process chart and a flow dia­gram?#

A flow process chart lists the activ­i­ties in sequence using sym­bols, with dis­tances and times. A flow dia­gram draws the same move­ment on a scale plan of the work­place, so the phys­i­cal path, back­track­ing and cross­ing can be seen.

Why is "Why?" asked for every step in the Exam­ine stage?#

Because the pur­pose ques­tion decides whether a step is needed at all. If a step has no valid pur­pose it is elim­i­nated, which is the biggest sav­ing; only nec­es­sary steps are then com­bined, rearranged or sim­pli­fied.

What are the five process chart sym­bols?#

Oper­a­tion (cir­cle), trans­port (arrow), inspec­tion (square), delay (let­ter D) and stor­age (tri­an­gle).

How is method study dif­fer­ent from work study?#

Work study is the broad field. Method study is one part of it, deal­ing with how the work is done; work mea­sure­ment is the other part, deal­ing with how long it should take.

Ref­er­ences#

1. Kanawaty, G. (ed.) Intro­duc­tion to Work Study. Inter­na­tional Labour Office, Geneva.
2. Gilbreth, F. B. (1911) Motion Study. D. Van Nos­trand Com­pany.
3. Chary, S. N. Pro­duc­tion and Oper­a­tions Man­age­ment. McGraw-Hill Edu­ca­tion (India).
4. Pan­neer­sel­vam, R. Pro­duc­tion and Oper­a­tions Man­age­ment. PHI Learn­ing.
5. Muther, R. (1973) Sys­tem­atic Lay­out Plan­ning. Cah­n­ers Books.

Related read­ing#

• Work Study in Oper­a­tions Man­age­ment
• Time Study and Work Mea­sure­ment in Oper­a­tions Man­age­ment
• Qual­ity Man­age­ment in Oper­a­tions Man­age­ment