10_Predetermined time systems.pdf

8/10/2019 10_Predetermined time systems.pdf

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!

How can we establish time standards for an operation?! Time Study

! Work Sampling

! Predetermined Times


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!

How do we obtain standard time in time studies?

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!

How do we find standard time throughwork sampling?

Example:

! During a work day of 8 h, 420 units are assembled.

! A work sampling study found that 85% of the time, the operator was

working on the assembly of the part."

using this information, can we estimate the Standard Time of the

assembly operation?

" The answer is NO.

" However, we can obtain the Observed Timeof the Operation. We wouldneed rating and allowances to estimate the standard time

! Assume that the analyst made a note on the pace rating of theassembly operation observed, and the average rating was R = 110.

Also, assume allowances of 15%. What is the standard time of theoperation?

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.


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!

How do we obtain standard time usingPredetermined Time Systems?

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Chapter 13

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Definition:

!

Predetermined Time Systems (PTS) is a database ofbasic motion times used to predict the normaltime

for new or existing operations.! A.k.a. basic motion times or synthetic times.

! PTS can also be used for:

! Determining time standards

!

The analysis of work methods

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!

Advantages:

1. Developing methods and cycle times in advance of actualproduction

2. Improve existing methods

3. Establish work standards or portions of work standards

4. Eliminate the need for performance rating, since it has been

considered in the establishment of the PTS motion times

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!

Disadvantages & Limitations of PTS:

1. Differences in the time values among the tables advocated bythe various systems

2. So many systems may be available that it can be difficult to

select the system which best fits the needs of a specific

company.

3.

PTS, as a rule, do not make any provisions for fatigue

4. Time study is still needed to verify the results

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11

Family tree of

predetermined time

systemsCourtesy: Standards International, Chicago, Illinois


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!

10 categories ofmovements:

1. Reach

2. Move

3. Turn

4. Apply pressure

5. Grasp

6. Position

7. Release

8.

Disengage9. Body Motions(leg-foot,

horizontal, vertical)

10. Eye Motions

!

Times are given in timemeasurement units(TMU)

! 1 TMU = .000 010 h=.036 s

! Times are for an experienced

worker working at a normalpace (100%)

! No allowances are included in

the times

!

Complaints regarding MTM-1are often a result of ignoring

learning curve

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How many TMUs are there in

1 second?


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! Reach is a motion that usually occurs with an empty hand

! 5 Types (A, B, C, D, E):

A. To an object in a fixedlocation or in the other hand Low visual control

B. To a single object whose generallocation is known Location may vary slightly from cycle to cycle Some visual control is necessary

C. To an objectjumbledwith others in a group

Considerable visual, muscular and mental control is necessary Most difficult reach Following grasp is complex

D. To a very small object or where accurate grasp is required Considerable visual control is necessary for accurate grasp.

E. To an indefinite location to get hand in position for body balance or next motionor out of way

!

Distances are for path for the hand knuckle or fingertip!

The effect of acceleration and deceleration can be omitted if the hand is inalready in motion.

! Example of reach code: R6B

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What is the time (in

seconds) for the ReachMovement R6B?

What is the time (in

seconds) for the ReachMovement R15A?


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!

Move is a motion that usually takes place with the hand holding something!

3 Types (A, B, C):A. Move object to the other hand or against stop

Minimal control needed

B. Move object to an approximate or indefinite location Some control needed

C.

Move object to an exact location Considerable control needed

! Code: M6B

!

Effect of weight moved should be considered! Up to 2.5 lb is included in standard time

! Code time = Standard time* Dynamic factor + Static constant

!

Example: moving 5-lb weight, 6 in., to indefinite location: code: M6B5

!

If object is slid, Effective Net Weight = weight * coefficient of friction! 0.4 for wood-wood, and wood-metal

! 0.3 for metal-metal

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M6B5


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3. Turn! A movement that rotates the hand, wrist, and forearm about

the long axis of the forearm

! Time depends on degrees of turn, weight of the object, and

resistance against turn! Eg: T30S, T45M

4. Apply pressure

! Application of force without resultant movement

! Eg: APA, APB

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!

Grasp is a motion in which the purpose is to gain control of an object! Skill Motion

! Improvements usually result in time reductions

! Often followed by move

! 5 TypesType 1. Pickup grasp (follows A,B-Reach)

"

Subdivided further, based on object size, surface, cylindrical size (1A, 1B, 1C1, 1C2, 1C3)

Type 2.Regrasp (to change or improve control during move)

Type 3.Transfer grasp (follows either A Reach or A Move)"

Transfer from one hand to another

Type 4.Jumbled grasp (follows C Reach)

"

Subdivided further, based on size of jumbled objects (4A, 4B, 4C)Type 5. Contact, sliding, or hook grasp (between Reach and Move) no timerequired for contact

! Eg: G1A

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!

Aligning, orienting, or engaging one object with another! Usually follows a C Move

! Also a skill motion

! Requires minor hand movements

!

Position times vary with:

! Amount of pressure needed to fit" (1)Loose, (2)close, (3)exact fit

! Symmetry of the object" (S)Symmetrical, (NS)nonsymmetrical, (SS)semisymmetrical

! Ease of handling" (E)Easy or (D)difficult

! Eg: P2SSE

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!

Breaking contact between one object and another! Includes involuntary movement from sudden end of resistance

! Times vary with:

!

Class of fit (loose, close, tight)! Ease of handling (easy and difficult)

! Care in handling

! Eg: D3E

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!

Relinquishing control of an object by the hand or fingers

!

Two types:

! RL1: Simple opening of the fingers (2 TMU)

! RL2: Contact release (0 TMU)

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9. Body Motions

!

Leg-foot, horizontal torso, vertical torso,

! Eg: W5P, SS15C1

10. Eye Motions

! Eye travel and eye focus

! Reading: TMU = 5.05 * # of words read

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!

All left-hand and right-hand motions required toperform the operation are summarized

!

The rated times in TMU for each motion aredetermined from the methods- time data tables

! Only limiting motions will be summarized

!

Allowance for personal delays, fatigue, or unavoidable

delays are not included in the tabulated values

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!

Lets work on the activity: Replace page in 3-ring binder! The elements include:

" Reach to binder (30 inches away on a shelf full of binders)

" Grasp binder

" Move to desk

" Release

" Reach to cover (located 7 in away from the hands)

" Grasp edge

" Open cover (Assume the hand moves along 16 in)

"

Release

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!

Combined Motions occur when the same bodymember performs two or more motions at the sametime.

! E.g: regrasp during move

!

Take greater of two times

! Draw a dash line instead of the time next to the motion code

that will be omitted

1.

E.g.: Regrasp during move of a 1lb object along 3inches to the other hand

2.

E.g.: Regrasp during move of a 1lb object along 6inches to the other hand

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!

Simultaneous Motions occur when different bodymembersperform different motions at the same time.

"

E.g.: Right and left hands

! Make sure simultaneous moves are truly simultaneous!

Can they be easily done simultaneously? (See Table X)

" If they are trulysimultaneous, allow only for the longer timeE.g.: M8A(left) and M10A (right)

"

If they are only apparently simultaneous, allow for both times.

E.g.: M8C(left) and M8C (right)

! See Step 2 of MTM-1 Analysis of:! Replace page in 3-ring binder

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!

Maynard Operational Sequence Technique! Based on observation that the majority of activities are

associated with a limited number of motion sequences

! Five times faster than using MTM-1 with similar accuracy

!

There are several MOST systems for different types ofoperations.

" See the H.B. Maynard and company website (www.hbmaynard.com)

! Basic MOST: Three sequence models

1.

General move2. Controlled move

3. Tool use

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!

The movement of an object through space where the path is notrestricted! E.g. free movement of an object through the air.

! 3 Components:! Get, Put, Return

!

Components are described by parameters related to actions/motions! A- action distance

! B- body motion

! G- gain control

! P- placement

!

The index of each parameter vary from 0 to 16, depends on the action:! Figure 13.13 (p. 528)

! E.g.: Get = A3B6G3

! Find TMU! The sum of the index values is multiplied by 10

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.

.


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!

Example:

An operator gets a washer 5 in away (within reach), placeon a bolt located (loose fit) 5 in away, and comes back tothe original position.

The total sequence and values is as follows:

(get) (put) (return)

A1B0G1 A1B0P1 A1

! Total time: 5x10 = 50 TMU

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!

Now your turn:

Walking 3 steps, bending down to pick up a bolt from thefloor, arising walking the three steps back and placing the

bolt in a bolthole.

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!

Example:

1.

Engaging a feed lever on a milling machine

This is a controlled move:

A1B0G1M1X10I0A0

Get:A1: Reach to LeverB0: No body movement

G1: Gain Control of light lever

Move/actuate lever:

M1: Move lever (


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!

Example of tool use :

1.

An operator picks up a knife (light) from a bench twosteps away, makes onecut across the top of a

cardboard box, and puts the knife back on the bench.The operator remains on the bench.


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!

Example of analysis


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!

Modular Arrangement of Predetermined Time Standards

!

Based on the concept that the body member used is thekey variable.

!

All body movements are multiples of a MOD (1 MOD= .129 s).

! www.modapts.org

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! How do we obtain standard time using Predetermined TimeSystems?

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Break the operation into elements

Break the elements into fundamental motions Depending on the PTS chosen

Determine the PTS code for each motion

Find the normal time for the code using PTS tables

No ratings are needed

Add allowances to the normal time to find the standardtime of the elements and operation.


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!

Predetermined timesystems are used to predict

the standard time for new orexisting jobs.

!

Time Studies are used topredict the standard time for

existing jobs.

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!

PTS directly provide normal times! Need to add allowances for standard

time.

! Time Studies provide observed time

! Need to include a Rating to obtain

normal time

! Need to add allowances to obtain

standard time

!

Need to understand the task

! Need to find normal times for task

components in tables

! Need to convert TMUS to

appropriate time units

!

Need to understand the task

! Need to gather data

! Need to analyze data to findobserved and normal times.


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Documents

10_Predetermined time systems.pdf