Lesson 10: Job design & work measurement

Operations Management

• Method study - It is the analysis and design of tasks, work methods involving human work activity, including jigs, tooling, equipment, technologies, workplace layout, plant layout, and work environment

• Work measurement – analysis of a task to determine the time that should be allowed to perform the task

Job design and work study

It is the function of specifying the work activities of an individual or group in an organizational setting aiming at developing jobs that meet the requirements of the organization and its technology and that satisfy the jobholder’s personal and individual requirements.

• Work study is the systematic examination of the methods of carrying on activities so as to improve the effective use of resources and to set up standards of performance for the activities being carried out.

• Known also as method study (the systematic recording and critical examination of ways of doing things in order to make improvements).

Work study

Method study includes:Methods analysis and Methods design.

Methods analysis is concerned with the study of an existing method or process.

Methods design is concerned with the design of a new method or process

Specifying the tasks that constitute a job for an individual or a group1.Specialization. Smith, Babbage.2.Method and Workplace optimization (Taylor, Ford3.Behavioral aspects: Hawthorne Studies (Elton Mayo)

4.Job expansion, motivation and incentive systems

Fundamentals of work study

They discovered productivity was independent from lighting levelsThey introduced psychology into the workplace: the social system may be more important than physical factors

Ultimate Job

Structure

Degree of

Specialization

Job Enrichment

(vs. Enlargement)

Balancing the specialization in a job

and its content through enrichment

Adding more variety to jobs Intended to reduce boredom associated with labor

specialization Job enlargement Job rotation Job enrichment Employee empowerment Self-directed teams

Job expansion

Task VarietySkill VarietyFeedback

Task IdentityTask Autonomy

Process Technology

Needs

Worker/Group Needs

Sociotechnical system: interaction between

technology and the work group

Sociotechnical Systems

Improved quality of work life Improved job satisfaction Increased motivation Allows employees to accept more

responsibility Improved productivity and quality Reduced turnover and absenteeism

Benefits of expanded work

Visual utensil holder encourages housekeeping.

Use low-cost visual devices to share information quickly and accurately: A clock reminds employees of the goal.

The visual workplace

Visual signals at the machine notify support personnel.

Process specifications and operating procedures are posted in each work area.

Visual kanban.

• Increase productivity and efficiency• Reduce cycle time • Reduce product cost• Reduce labor content • Improve product and/or service quality• Reduce lead times and improve work flow• Increase flexibility of work system• Improve worker safety• Apply more ergonomic work methods• Enhance the environment (both inside and outside the

facility)

Aims of work study

Step 1: Select work to be studied 1. Economic or cost-effective considerations.2. Technical or technological considerations.3. Human considerations.

Step 2: Record and Examine present methodStep 3: Develop alternatives Step 4: Evaluate Alternatives and Select the BestStep 5: Define and Implement the Best MethodStep 6: Audit the Study and maintain the new standard

Methods analysis

Ergonomics is the study of the interface between man and machine (workplace arrangement)

The work environment Illumination Noise Temperature Humidity

Ergonomics and the work environment

Good arrangement of parts and tools in workplace Numbers indicate sequence of work elements in relation to locations of hand tools and parts bins.

Ergonomics and the work environment

Method of work: standard practice sheet

Outline process chart

An outline process chart is a process chart giving an overall picture by recording in sequence only the main operations and inspections

ASME symbols

Flow process chart

Worker type

Material type

Equipment type

Flow process chart

A worker-type flow process chart is a flow process chart whichrecords what the worker does

Process flow diagram (Spaghetti chart)

Incoming parts

From Milwaukee on a JIT arrival schedule

Engines and transmissions

Flow chart

The string diagram is a scale plan or model on which a thread is used to trace and measure the path of workers, material or equipment during a specified sequence of events

String diagram

Multiple activity chart/activity chart

Worker-machine chart

Activity chart

Two-handed process chart

The two-handed process chart is a process chart in which the activities of a worker's hands are recorded in their relationship to one another

Operation chart

SIMO chart

A procedure flowchart

Value Stream Map

50 conjunts. magatzem 50 components

d’origen (1) “C” (nous”) magatzem

40m.0,2h es transp. 50 cjts del recanvis magat.(1) al lloc treball (3) es transp.50 comp. 1 conjunt 30m. 0,2h del magat.(2) al lloc treball (3) 0,034h desmuntar i 1 comp.”C” comprovar conjt.

“A” 0,02h muntar “C” a caixa “A” i verificar “B” mecanitzar

0,048h i verificar 0,05h posar “C”(rebutja) 10 cjts/caixa (espera) muntar “B” a 0,015h comp. “A” 5 caixes (50 cjts.) es transp. a

40m. 0,2 h magatz. (1) (espera)

magatz.(1)

1 11

1

1/1

1

2

2

3

3

2/2

3

4/3

5

2

50 conjunts. magatzem 50 components

d’origen (1) “C” (nous”) magatzem

40m.0,2h es transp. 50 cjts del recanvis magat.(1) al lloc treball (3) es transp.50 comp. 1 conjunt 30m. 0,2h del magat.(2) al lloc treball (3) 0,034h desmuntar i 1 comp.”C” comprovar conjt.

“A” 0,02h muntar “C” a caixa “A” i verificar “B” mecanitzar

0,048h i verificar 0,05h posar “C”(rebutja) 10 cjts/caixa (espera) muntar “B” a 0,015h comp. “A” 5 caixes (50 cjts.) es transp. a

40m. 0,2 h magatz. (1) (espera)

magatz.(1)

1 11

1

1/1

1

2

2

3

3

2/2

3

4/3

5

2 <<<<<<<<<<<<<<<

b) - Número d’operaris necessaris:

Càlcul temps unitari:

- Producció dia: 240.000 / 240 = 1.000 cjts/dia

- Nº obrers necessaris:

-

obrersobrerdiah

diacjtscjth 1775,16/8

/000.1/134,0

c) - Distribució d’operaris:

0,2/50=0,004h 0,034h 0,015h

0,2/50=0,004h 0,048h 0,05/10=0,005h

0,2/5x10=0,004h 0,02h

Total: 0,012h 0,102h 0,02h

Temps tipus unitari: 0,012h + 0,102h + 0,02h = 0,134h

1

2

3

2/2

4/3

1/1 3

5

1

1 2 3

4

6

2

5

7

8

N Simbol Tempsunitari

1000Cjts/dia

Núm. Operaris(8h)

1 0,004h 4 h 1 Sobra 4h(fer 1 i 8)

2 0,034h 34 h 4 Falta 2h

3 0,048h 48 h 6

4 0,015h 15 h 2 Sobra 1h

5 0,004h 4 h3

6 0,02h 20 h

7 0,005h 5 h 1 Sobra 3h(fer 7 i ajudar a 2)

8 0,004h 4 h

1/1

2/2

4/3

3

5

1

3

2

• Time is the most frequently used measure of work (work-hours)– How many minutes or hours are required to perform a

given task? • Most workers are paid by the time they work

– Salary– Incentive systems

• Labor requirements computed in units of time (Labor-hours, man-hours)

Work measurement: the importance of time

Labor standards are the amount of time required to perform a job or part of a job

Started early in the 20th century (Taylor, Gilbreth) Necessary for determining staffing requirements Important to labor incentive systems

Work measurement: labor standards

1. Labor content of items produced2. Manpower planning: Staffing needs3. Cost and time estimates4. Crew size and work balance5. Expected production6. Basis of wage incentive plans7. Efficiency of employees

Work measurement is the application of techniques designed toestablish the time for a qualified worker to carry out a task at adefined rate of working

Estimation: experience / Historical records

Time studyTime study is a work measurement technique for recording the times of performing a certain specific job or its elements carried out under specified conditions, and for analyzing the data so as to obtain the time necessary for an operator to carry it out at a defined rate of performancePredetermined motion time systems (PMTS)Work sampling Standard data systems

Work measurement: techniques

How the task was performed last time Easy and inexpensive Data available from production records or time cards Data is not objective and may be inaccurate

1. Define the task to be studied2. Divide the task into precise elements

3. Time and record element times and rating of performance

4. Compute average normal time5. Determine standard time

A qualified worker is one who has acquired the skill, knowledge and other attributes to carry out the work in hand to satisfactory standards of quantity, quality and safety. 

Work measurement: 2. time studies

An element is a distinct part of a specified job selected for convenience of observation, measurement and analysis

• Repetitive element is an element which occurs in every work cycle of an operation. Examples: the element of picking up a part prior to an assembly operation; putting aside a finished component or assembly.

• Occasional element is performed with a frequency of less than once per cycle. It will be incorporated in the final standard time for the job. Examples: adjusting the machine setting.

• Manual element is an element performed by a worker.

• Machine element is an element performed automatically by any process.

Work measurement: types of elements in time studies

Defined as the pace or relative speed of working. Actual time to perform the cycle depends on worker performance

Work measurement: Worker performance

Normal performance: a pace of working that can be maintained by a properly trained average worker throughout an entire work shift without injurious effect on the worker’s health or physical well-being. Walking at 3 miles/hr.Normal time is the time to complete a task when working at normal performance.The basic time (0.20 minutes in the example) represents the time the element would take to perform if the operator was working at the normal rate, instead of the faster one actually observed (in the judgment of the observer).

Rating is the assessment of the worker's rate of working relative tothe observer's concept of the rate corresponding to standard pace

Desired accuracy 5% (h = 0.05)Confidence level 95% (z = 1.96)

Sample mean x = 13Sample standard deviation s = 1.0

n = 2zs

hx n = ≈ 9.1 > no

21.96 x 1.0.05 x 13

s = ∑(xi - x)2

no

n-1

Work measurement: Time study sample size

Work measurement: Worker performance

Defined as the normal time but with an allowance added in to account for losses due to personal time, fatigue, and delays (PFD)

Tstd = Tn (1 + Apfd)

where Tstd = standard time, Tn = normal time, and Apfd = allowance factor

Work measurement: Standard time (allowed time)

The function of the allowance factor is to inflate the value of standard time in order to account for the various reasons why the worker loses time during the shift

To account for the delays due to: • Personal time (P) 4% - 7% for use of restroom, water fountain, etc.• Fatigue (F) Rest breaks are intended to deal with fatigue• Delays (D) Interruptions, equipment breakdowns

Work measurement: Allowances

• Given: The normal time to perform the regular work cycle is 3.23 min. In addition, an irregular work element with a normal time = 1.25 min is performed every 5 cycles. The PFD allowance factor is 15%.

• Determine (a) the standard time and (b) the number of work units produced during an 8-hr shift.

Work measurement: Exercise. Computing the standard time

Worker efficiency – work accomplished as a proportion of shift hours

Ew = Hstd / Hsh

Ew = worker efficiencyHstd = standard hours of work accomplished

Hstd = Q Tstd Q = quantity of work units completedTstd = standard time per work unit

Hsh = shift hours

Work measurement: Worker efficiency

• Suppose the worker’s pace in the task is 125 (2.78 min). The actual hours worked is 7.42 hr.

Determine • (a) the number of pieces produced• (b) the number of standard hours accomplished• and (c) the worker’s efficiency.

Work measurement: Exercise. Computing efficiency

• Operator’s work elements that are performed in succession with the machine’s work elements are called external work elements

• Those that are performed simultaneously with the machine cycle are called internal work elements.

Work measurement: Worker-machine systems

Tc = 0.10 + 0.12 + 0.75

= 0.97 min

Divide manual work into small basic elements that have established times

Can be done away from the actual production operation

Can be set before the work is actually performed

Work measurement: 3. Predetermined time standards

Activities of the limbs and other body parts:– Reaching for an object– Grasping the object– Moving the object– Walking – Eye movement

A work element consists of multiple basic motion elements

Work measurement: basic motion elements

• Most of the MTM basic motions involve hand and arm movements, although elements are also provided for eye, leg, foot, and body actions: reach, move, turn, grasp, position

• MTM was developed by studying motion pictures of work activity. Time units are called TMUs (time measurement units). 1 TMU = 0.00001 hr

Work measurement: Methods Time Measurement (MTM)

Tiempos en UMT (cmh) a actividad 111% para micromovimientos MTM 2 Distancia a recorrer en

cm.

SIMBOLOS Observaciones G P

A B C A B C De 0 a 5 3 7 14 3 10 21 Las categorías A, B y C

indicadas se refieren a la complejidad de las acciones de recoger y poner.

De 5 a 15 6 10 19 6 15 26 De 15 a 30 9 14 23 11 19 30 De 30 a 45 13 18 27 15 24 36 De 45 a 80 17 23 32 20 30 41

Con

correcciones 1 C

orrección (N

o usar) Sin correcciones M

uy peque, plano, inter- ferencias, am

ontonado C

oger, cam

biar de m

ano Sin coger, indefinido, sólo contacto

SIMBOLOS Aplicar al peso: x 0,4 o x 0,2 o / 2 A R E C S F B GW PW 14 6 7 15 18 9 61 1 por 1 Kg. 1 por 5 Kg.

Categoría

Símbolo

Observaciones Español Inglés Recoger,

Conseguir (alcanzar+coger+soltar)

Grasp

G

Hay cuatro categorías. A tres de ellas se las denomina: A, B y C, y se refieren a la complejidad de la acción de recoger. La cuarta, denominada GW, se utiliza cuando hay que levantar pesos superiores a 2 kg.

Poner, Colocar (mover+posicionar)

Put P Como en el caso anterior, hay también cuatro categorías: A, B, C y W. Consiste en cambiar de sitio un objeto con la mano

Reasir Regrasp R Consiste en cambiar la manera de asir un objeto.

Aplicar Presión Apply Pressure A Ejercer cierto esfuerzo sobre un objeto.

Emplear los Ojos Eye Motion E Reajuste ocular para localizar un objeto o necesidad de cambiar el campo visual.

Mover el Pie Foot Motion F Realizar un movimiento con el pie o con la pierna.

Dar un Paso Step S Desplazar el cuerpo o mover la pierna más de 30 cm.

Inclinarse y Levantarse Bend and Arise B Mover el tronco hacia adelante.

Hacer Girar Crank C Desplazar el objeto con la mano según trayectoria circular.

Work measurement: Exercise 1

Work measurement: Exercise 2

Estimates percent of time a worker (machine…) spends on various tasks

Requires random observations to record worker activity

Can be used to set staffing levels, reassign duties, estimate costs, and set delay allowances

Work measurement: 4. Work sampling

n: required sample sizez: standard normal deviate for desired confidence level (z = 2 for a 95.45%)p = estimated value of sample proportionh = acceptable error level in percent (h =0.03)

All but idle and personal time are work related Percentage idle time = (126 + 62)/833 = 22.6%

Work measurement: Work sampling example

No. of Observations Activity

485 On the phone or meeting with a client126 Idle62 Personal time23 Discussions with supervisor

137 Filing and computer data entry833