Industrial Engineering and Ergonomics - Startseite - IAW · © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University Industrial Engineering and Ergonomics

© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University

Industrial Engineering and Ergonomics

Dr.-Ing. Dr. rer. medic. Dipl.-Inform. Alexander Mertens

Univ.-Prof. Dr.-Ing. Dipl.-Wirt.-Ing. Christopher M. Schlick

Chair and Institute of Industrial Engineering and Ergonomics

RWTH Aachen University

Bergdriesch 27

52062 Aachen

phone: 0241 80 99 494

email: [email protected]

Unit 5

Modeling and optimizing manual work processes with MTM

Fall Winter 2016/2017

5 - 2 © Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University

Learning Targets

Learning the basic principles of the sequence-analytical time modeling (predetermined motion-time systems) of manual work processes

Getting to know and generally being able to independently apply MTM (“Methods-Time Measurement”)

Being acquainted with compressed MTM data systems

Being capable of choosing the correct MTM data system in practice

Being acquainted with the possibilities and limitations in the usage of MTM


Introduction: Automobile assembly

How to conduct “line-

balancing” of manual tasks in

an assembly line, so that the

utilisation is as high as

possible without constraining

the employees by the process

design?

Work station 1 W 1.1

Work station 2

W 2.2

Work station 3

W 2.1.1

W 2.1.2

W 2.3

...

Clock cycle

W 1.2

W 1.3

Illustration for line-

balancing

(Gantt chart)

Source: DPA; Spiegel Online 2008 M

ate

rial flow


Methods for the determination of time data

Determining time

experimental methods (ACTUAL TIMES)

computational methods (TARGET TIMES)

observation

• manual time measurement - stopwatch - video analysis - REFA procedures

• work sampling (time measurement by means of statistical analysis)

– frequencies (MMH) – time-on-task (MMZ)

• interview techniques

self-report

• made by the worker

comparison and estimation

• Comparison of the work procedures for which the time standards are to be determined with similar activities for which time standards have already been set.

• The estimation is based on standard times for the procedure based on historical records or experience (comparative estimation).

compilation

calculation of work cycles

• systems of predetermined times • based on

process models (e.g., for turning)

• with quantitative information processing models

• with biomechanical models

– list of activities, their duration, and the frequency of their occurrence (e.g., office work)

• with the aid of devices (e.g., computer log-files)

• standard times - catalogue of task times - nomograph

- Methods Time Measurements (MTM) - Work Factor (WF)

Statistical time models Sequence-analytical time models


MTM as a Predetermined Motion-Time System

The method

determines the

time

Methods

Time

Measurement

MTM is a predetermined motion-time system (PMTS).

Predetermined motion-time systems are methods to fractionalize manual

operational procedures, which can be influenced by the worker, in elements of

motions and to assign motion time standards to these elements.

2 3 4 5

time

Motion element

3

3

4

4

5

5 2

Right hand motion

Left hand motion

1

2 1

1


Application of Predetermined Motion-Time Systems

(PMTS)

• planning of the

operating process

• optimization of the

operating process

• design of tools and

equipment

• design of the

manufacture

• creation of target

times

• determination of

standard time for

performance-related

wages

• pre-costing

• description of the

operating processes

for education and

instruction materials

PMTS applications

work instruction time determination design of the work

system


Historic milestones in the development of PMTS

1900

1910

1920

1930

1940

1950

F. W. Taylor: Scientific Management (fractionalization of tasks and measurement of subtracted

times)

F. B. Gilbreth (1911) Motion Study

R. Thun (1925) (proposals for the development of a system of

pre-determined times)

(Gilbreth detected that human motions can be put down to

seventeen fundamental motions - Therbligs - by dint of film

shots.)

WF (Work Factor): Start of development (1934)

WF published in 1945 (Quick et al.)

MTM: Start of development (1940)

MTM published in 1948

(H. B. Maynard, J. L. Schwab, G. J. Stegemerten)

1970 MOST published in 1972 (K. Zandin)


Development of MTM-1 - Procedure

Acquisition of motion sequences and their influencing variables

in different work situations with different workers by means of

film shots

(single pictures with a rate of 16 pictures per second)

Determination of actual times by counting single pictures

Compensation of interpersonal performance variation by using

the Lowry-Maynard-Stegemerten (LMS) method

Compensation of variance by regression analysis

Result: MTM-1 metric card


influences independent

from people

effort dexterity constancy of

execution time

working

conditions (e.g. lightning)

influences dependent

from people

performance index

according to LMS

= actual time according

to video analysis /

time recording

median LMS-

performance index of

the evaluation group

MTM standard

performance

A standard performance of 100% is described within the LMS method as

“performance of a moderately high trained person who can show this

performance in perpetuity without work fatigue”.

Development of MTM-1 -

The Lowry-Maynard-Stegemerten method

LMS: Lowry, Maynard, Stegemerten

(names of the developers of this

method)


Development of MTM-1 -

Results

Result of the development:

MTM-1 metric card

The MTM-1 metric card

comprises time values for

fundamental motions subject to

time-influencing factors

Time values are stated as TMU

(Time Measurement Unit)

1/100,000 h = 1 TMU

0.036 s = 1 TMU

Deutsche MTM-

Vereinigung e.V.


MTM-1:

Fundamental motions at a glance (1a)

5 fundamental motions of the finger-, hand-, and arm-system

Release Reach

Grasp

Move

Position

Deutsche MTM-

Vereinigung e.V.

Motion

cycle


MTM-1:

Fundamental motions at a glance (1b)

The performance of

simple motions such as

Reach and Move can

hardly be improved by

means of additional

training.

Difficult motions such

as Grasp and Position

are available for training

and can thereby be

improved.

(Source: Rohmert & Kirchner, 1969)

Comparison of the learning progress for the different motions:

time per

motion

Grasp

Reach

Position

Move

person A

person B

person C

training time training time


3 additional fundamental motions of the

finger-, hand-, and arm-system:

Turn

MTM-1:

Fundamental motions at a glance (2)

Disengage

Apply Pressure

Resistance which is

to be overcome to

open the fridge’s

door

Deutsche MTM-

Vereinigung e.V.


2 fundamental motions of the eyes:

D = 30 cm

T =

4 0

c m

MTM-1:


Eye focus

Eye travel

Deutsche MTM-

Vereinigung e.V.


15 fundamental motions for body movements:

MTM-1:


body

movements

without shift of

body axis

with shift of

body axis

with inclination

of body axis

foot motion

leg motion

side step

turn body

walk

bend

arise from bend

stoop

arise from stoop

kneel on one knee

arise from kneel on one knee

kneel on both knees

arise from kneel on both

knees

sit

stand


MTM-1: Time-influencing factors considering

reaching as example

2 or less 2,0 2,0 2,0 2,0 1,6 1,6 0,4

4 3,4 3,4 5,1 3,2 3,0 2,4 1,0

6 4,5 4,5 6,5 4,4 3,9 3,1 1,4

8 5,5 5,5 7,5 5,5 4,6 3,7 1,8

10 6,1 6,3 8,4 6,8 4,9 4,3 2,0

12 6,4 7,4 9,1 7,3 5,2 4,8 2,6

14 6,8 8,2 9,7 7,8 5,5 5,4 2,8

16 7,1 8,8 10,3 8,2 5,8 5,9 2,9

18 7,5 9,4 10,8 8,7 6,1 6,5 2,9

20 7,8 10,0 11,4 9,2 6,5 7,1 2,9

22 8,1 10,5 11,9 9,7 6,8 7,7 2,8

24 8,5 11,1 12,5 10,2 7,1 8,2 2,9

26 8,8 11,7 13,0 10,7 7,4 8,8 2,9

28 9,2 12,2 13,6 11,2 7,7 9,4 2,8

30 9,5 12,8 14,1 11,7 8,0 9,9 2,9

35 10,4 14,2 15,5 12,9 8,8 11,4 2,8

40 11,3 15,6 16,8 14,1 9,6 12,8 2,8

45 12,1 17,0 18,2 15,3 10,4 14,2 2,8

50 13,0 18,4 19,6 16,5 11,2 15,7 2,7

55 13,9 19,8 20,9 17,8 12,0 17,1 2,7

60 14,7 21,2 22,3 19,0 12,8 18,5 2,7

65 15,6 22,6 23,6 20,2 13,5 19,9 2,7

70 16,5 24,1 25,0 21,4 14,3 21,4 2,7

75 17,3 25,5 26,4 22,6 15,1 22,8 2,7

80 18,2 26,9 27,7 23,9 15,9 24,2 2,7

R-E

E Reach to indefinite location to get

hand in position for body balance or

next motion or out of way.

Case and Description

Distanc

e moved

in cm

Time TMU

R-C

R-DR-BR-A

m-Wert

für B

mR-B

R-Bm

D Reach to a very small object or

where accurate grasp is required.

mR-A

R-Am

A Reach to object in fixed location,

or to object in other hand or on

which other hand rests.

B Reach to single object in location

which may vary slightly from cycle to

cycle.

C Reach to object jumbled with

other objects in a group so that

search and select occur.

2. Case of motion

3. Type of

motion path

1. Distance moved “Reach” (R) is the fundamental movement

for moving the fingers or hand to a determined or

undetermined location. Messpunkt

Messpunkt

Bewegungslänge in cm

Messpunkt

Messpunkt

Bewegungslänge in cm

Pictured example: R-B

v

t

v

t

v

t

v

t Typ II

R30Bm mR30B

v

t Typ I

R30B



grasping as example

“Grasp” (G) is the fundamental motion which is

accomplished to keep one or several items in check

with fingers or hand, so that the following fundamental

motion can be carried out.

Case TMU

G1A 2,0 Pick Up Grasp:

G1B 3,5

G1C1 7,3 > 12 mm Ø

G1C2 8,7 6 to 12 mm Ø

G1C3 10,8 < 6 mm Ø

G2 5,6

G3 5,6

G4A 7,3

G4B 9,1

G4C 12,9

G5 0,0

Description

Very small object or object lying close against a flat surface.

Small, medium or large object by itself, easily grasped.

Regrasp. Shift of the control point of an item without losing control of item

Transfer Grasp. One hand takes over control of an item while other releases.

Contact, sliding or hook grasp. Gain sufficient control over item through

contact so that following fundamental movements can be executed.

Interference with grasp on bottom and one side of nearly

cylindrical object.

< 6x6x3 mm

Select grasp:

Object jumbled with other objects so search

and select occur.

> 25x25x25 mm

6x6x3 bis 25x25x25 mm

Time-influencing

factors:

1. Mode of

grasping

2. Position of item

3. Constitution of

item


Pick up grasp G 1

Regrasp G 2

Transfer grasp G 3

Select grasp G 4


grasping as example

Seldom in practice Frequent in practice Highly frequent in

practice

G 1 A G 1 B G 1 C

Start of motion Motion End of motion

Right hand (dashed) to

left hand Handing over

Right hand (dashed)

has taken on check on

the item.

G 4 A G 4 B G 4 C

Two partial dimensions should fall in the respective category.

> 25 x 25 x 25 mm > 6 x 6 x 3 mm

< 25 x 25 x 25 mm < 6 x 6 x 3 mm

7,3 TMU 9,1 TMU 12,9 TMU


Application of MTM-1:

Procedure

Motion analysis

Segmentation of the motion sequence in

elements, i.e. reaching.

Time analysis

Determination of the time-influencing factors for

every single motion element, i.e. distance moved,

or property of item.

Coding

of the motion element and of the influencing

variables.

Addition

of the elementary motion times to obtain the basic

motion time in demand.

Extraction

of the elementary motion time from the charts.


Reach

for bolt • Distance moved: 40 cm

• bolt is mixed with others

R 40 C 16,8 TMU

Grasp

at bolt

• admeasurements: 8 x 12 mm

• bolt is mixed with others G 4 B 9,1 TMU

Move

the bolt to

apparatus

• Distance moved: 40 cm

• accuracy of placing: move object

to exact

location

M 40 C 18,5 TMU

Position

the bolt

to hole

• assembling tolerance: tight

• symmetry: fully symmetric

• handling: easy

P2SE 16,2 TMU

Release

of bolt

• opening the fingers RL 1 2,0 TMU

Description of the

motion sequence

Necessary information for the

time allocation

Coding Time Value

Cumulative time

needed

62,6 TMU

2,25 s


Example



Systematics of the Motion Sequence (1)

simultaneous

movements

combined

movements

successive movements non-successive movements

Motion sequence

Successive movements are single

movements or movements in a

series which are executed

consecutively by the same or

different body parts without

temporal overlapping and

interruption.

Description A H Code TMU Code A H Description

12.8 R30B pens

2.0 G1A

15.1 M30C device

5.6 P1SE

2.0 RL1




simultaneous

movements

combined

movements


Motion sequence

Combined movements are two

or more completed

movements that are executed

at the same time by one body

part.

In the example, a non time-determinig re-grasping (with the same hand) occurs during the movement.

TMU Code A H Description

9.1 G4B

10.5 (M16C device

(G2

5.6 P1SE




simultaneous

movements

combined

movements


Motion sequence

Simultaneous movements are single

movements or movements in a series

that are executed by different body parts

at the same time.

Left hand Right hand

Description A H Code TMU Code A H Description

pens R20C 11.4 [R10C pens

9.1 G4B

G4B 9.1

device M16C) 10.5 (M16C device

G2) (G2

P1SE 5.6 P1SE

RL1 2.0 RL1




Degree of control of

basic movements

Degree of practice of the

worker

State of the site/ the

objects

Determining criteria for

the simultaneity of

movements:

Read-off example for the simultaneity of movements:

easy

with practice

difficult

Possibilities for

simultaneous execution:

Reach

Move

Grasp

Position

Disengage

Disengage Position Grasp Move Reach

within normal field of view

outside normal field of

view

Easy to handle

Difficult to handle

V5-1 Bimanual movements

MTM Legobeispiel Methodenvergleichgültig.mpg


Example of application: Assembly of two bolts –

Analysis using MTM-1

Reach R30C 14,1 TMU

Grasp G4B 9,1 TMU

Move M30C 15,1 TMU

Position P2SE 16,2 TMU

Release RL1 2,0 TMU

Reach R30C 14,1 TMU

Grasp G4B 9,1 TMU

Move M30C 15,1 TMU

Position P2SE 16,2 TMU

Release RL1 2,0 TMU

Total Time 113 TMU

left hand right hand

R30C 14,1 TMU R30C

G4B 9,1 TMU

9,1 TMU G4B

M30C 15,1 TMU M30C

16,2 TMU P2SE

P2SE 16,2 TMU

RL1 2,0 TMU RL1

81,8 TMU


Possibilities and limitations in the application

of MTM-1

Application of MTM-1

mass production in large batches

limited product variety

short-cyclical workflows

exactly defined basic conditions

experienced, highly trained employees

workstations with a detailed-oriented design

comparison

of

processes

comparison

of design

alternatives

process

optimization

evaluation

of short-

cyclical

workflows

creation

of the

work plan

and training


Further development of MTM (1)

change of the

market

requirements for

analysis systems

objectives of

further

development

shortening of the

product-life-cycles

increase in the

number of

alternatives

smaller batch sizes

frequently-changing

production requests

high analysis

speed

sufficient

accuracy of

the time data

transparency and

reproducibility

of the time data

accommodation to the

method level in the following

areas of application:

single-part and

small-series production

series production


MEK -

stages of

extension

MEK

UAS -

stages of

extension

MTM-1 fundamental motion

sequence of motions

fundamental operation

steps of operation

sequence of operation

work process

UAS

values of production area

basic values

single-part/

small-series series production mass production

method level low high

data

com

pre

ssio

n

Universal Analyzing System

MTM for single-part and small- series production (MEK)


Deutsche MTM-Vereinigung e.V.


MTM-1

Get and Place

MTM standard data /

basic values

MTM-UAS/

-MEK

sequence of

motions

fundamental

operations

Reach

Grasp

Move

Position

Release

Get

Place

fundamental motions


Data construction by high and transverse

aggregation

Deutsche MTM-

Vereinigung e.V.


Application Example: Comparision of MTM-1 and

MTM-UAS at a soldering process

Description Code TMU

Get and Place AC2 55

Handle the soldering

iron HC2 70

Soldering PT 100

Release PA2 20

Total 245

MTM-1 MTM-UAS

Left hand Right hand

Description Code TMU Code

Reach R30B 12,8 [R35A

Grasp G1A 2,0 G1A

Move M30C 15,1

Move 16,8 M35C

Position P2SE 16,2

Position 43,0 P3SE

Soldering PT 100,0

Move M30B] 16,8 M35C

Position 5,6 P1SE

Release RL1 2,0 RL1

Gesamt 230,3


Application example:

Carburetor of type Stromberg 175 CD-2

MTM-1 MTM-UAS

Predicted assembly time 140s 146s

Number of MTM components 975 182

Comparison of MTM-1 and MTM-UAS using the example of

learning process of the subassembly of a carburetor

0 250 500 750 1000

146

T [s]

n

industrial mechanic,

graphical work plan

1 2 3 4 5

146

291

603

TUAS =

T1 =

TUAS =

T [s]

T5 =

n


Advantages and disadvantages of the MTM

methodology

Advantages

It is possible to determine operating processes and execution times explicitly already in the planning phase of a work system.

Training periods can be reduced since employees can already be trained before the introduction of new work processes.

It is possible to design work systems in a target-oriented way, as influencing variables concerning the execution times become transparent by means of the MTM methodology.

MTM time values are based on a 100% standard performance. An evaluation of the performance rate – as to be found in REFA Stop watch time study – is not necessary.

The coding of the motion elements leads to an internationally homogenous, reproducible description of the operational procedures.

Disadvantages

The implementation of MTM is limited to manually operated tasks.

The analysis effort is rather high.

The analysis can be influenced subjectively.

V5-2 Final example

mtm_english.mpg


Quick Knowledge Check

What is the purpose of predetermined motion-time systems?

What was the procedure during the development of MTM-1?

Which 5 fundamental motions of the finger-, hand-, and arm-system

can be distinguished within MTM-1?

What is the procedure for the application of the MTM method?

What are the preconditions for the application of MTM-1?

What are the reasons for the development of compressed

MTM methods?

How do you determine which MTM analyzing system should

be applied in operational practice?

What are the advantages and disadvantages of the MTM method?


References

Antis, W.; Honeycutt, J.M.; Koch, E.N. (1973): The Basic Motions of MTM, The Maynard Foundation, fourth

edition.

Bokranz, R.; Landau, K. (2006): Produktivitätsmanagement von Arbeitssystemen – MTM-Handbuch, Schäffer-

Poeschel Verlag Stuttgart.

Gilbreth, F.B. (1911): Motion Study: A Method for Increasing the Efficiency of the Workman, Van Nostrand, New

York.

Jeske, T.; Schlick, C. (2012): A New Method for Forecasting the Learning Time of Sensorimotor Tasks. In:

Advances in Ergonomics in Manufacturing, S. 241-250, Boca Raton (FL).

Maynard, H.B.; Stegemerten, G.J.; Schwab, J.L. (1948): Methods-time Measurement. McGraw-Hill Book

Compony, New York.

Rohmert, W.; Kirchner, J.H. (1969): Anlernung sensumotorischer Fertigkeiten in der Industrie. Beuth, Berlin.

Salvendy, G. (2001): Handbook of Industrial Engineering, Wiley-Interscience, New York, N. Y. 10158, third

edition.

Schlick, C.; Bruder, R.; Luczak, H. (2010): Arbeitswissenschaft, Springerverlag Berlin Heidelberg.

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