Predetermined Time Systems

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Chapter 26:Chapter 26: Predetermined Predetermined Time Systems (PTS) Using MTMTime Systems (PTS) Using MTM

MTM = Methods-Time MeasurementMTM = Methods-Time Measurement• MTM-1 // MTM-2 // MTM-3MTM-1 // MTM-2 // MTM-3

Developed by the Gilbreths:Developed by the Gilbreths: improved the bricklaying by 300%: a > 2000 yrs practice !!

Occurs in 2 steps:Occurs in 2 steps:• Break work down into its therblig elementsBreak work down into its therblig elements• Assign time values to each elementAssign time values to each element

Each element is independent and additiveEach element is independent and additive

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MTM-1MTM-1

Most detailed Most detailed systemsystem

Motions are broken Motions are broken into 10 categoriesinto 10 categories

Times are found in Times are found in Tables 26.1-26.11Tables 26.1-26.11

Distance, Distance, complexity, and/or complexity, and/or weights are taken weights are taken into considerationinto consideration

MTM Categories MTM Categories • ReachReach• MoveMove• Turn Turn • Apply PressureApply Pressure• GraspGrasp• PositionPosition• ReleaseRelease• DisengageDisengage• Body MotionsBody Motions• Eye MotionsEye Motions

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Methods Analysis and Time:Methods Analysis and Time:

Reference: Karger, D. & Bayha, F. “ Engineered Work Reference: Karger, D. & Bayha, F. “ Engineered Work Measurement”, 4th edition. New York, Ind. Press Measurement”, 4th edition. New York, Ind. Press 1987.1987.

• Time is given in time measurement units (Time is given in time measurement units (TMUTMU’s)’s)

1 TMU = 0.000 010 h = 0.000 600 min = 0.036 s1 TMU = 0.000 010 h = 0.000 600 min = 0.036 s

-Or--Or-

1 s = 27.78 TMU’s1 s = 27.78 TMU’s1 min = 1,667 TMU’s 1 min = 1,667 TMU’s 1 hr = 100,000 TMU’s1 hr = 100,000 TMU’s

No Allowances Included

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MTM-2 and MTM-3MTM-2 and MTM-3

Fewer types of motions than MTM-1 Fewer types of motions than MTM-1 therefore are easier to usetherefore are easier to use

Fewer cycles needed in order to Fewer cycles needed in order to study the processstudy the process

• MTM-1 – requires 250 cycle timesMTM-1 – requires 250 cycle times• MTM-2 – requires 100 cycle timesMTM-2 – requires 100 cycle times• MTM-3 – requires 35 timesMTM-3 – requires 35 times

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REACH: Table 26.1

Distances: Motion path of hand knuckle or finger tip. Body assistance (shoulder movement or pivoting) not included. Interpolation is suggested: R15A

Acceleration & Deceleration:Hands could be in motion at the beginning and end of the cycle. Then Acc. & Decel. can be omitted. Double this decrease is subtracted (Hand in Motion Table 26.2)

MOVE: Table 26.2

Hand is usually holding something (or pushing and dragging an object. Three cases are considered (nature of their destination).

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Movements can be refined to consider the effect of acceleration or Dec., or both. Also considered as a refinement for Object weight resistance to movement.

MTM: Both Moves and Reach are influenced by motions preceding or following them

Nomenclature:Accel. - Decel. If omitted we use m: mM6B or M6Bm

Weight: Included up to 2.5 lb/hand If two hand used, and object is 5lb, no extra time is allocated.

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Sliding: Takes the Object Weight (wood-wood = wood-metal = 0.4, metal-metal = 0.3)

Example: M6B = 8.9 a 5lb weight object(T-26.2) M6B5 = 8.9 1.06 + 2.2 = 11.8

Dynamic Factor Static Constant

Weight of Additional Components: To gain control through dynamic component for extra Travel Time.

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TURN: (Table 26.4)Considers the rotation of the hand, wrist and forearm about long axis of forearm:

Time = f(,weight, resistance to )

APPLY PRESSURE: (Table 26.5)Is the application of force without resultant move:APA = Basic element APB = APA + Regrasp

GraspPosition

DisengageRelease

Time Reducers

Skill Motions

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Methods Analysis and Time:Methods Analysis and Time:GRASP: (Table 26.6)To gain Control of an object or Objects (followed by a move). Considers 5 Types:

Type 1: Pick-up Grasp: Follows an A or B reachType 2: Regrasp: Performed during a move: limited-outType 3: Transfer Grasp: Control from 1 hand to the otherType 4: Jumbled Grasp: Follows a C reachType 5: Contact, sliding or hook Grasp: Between a Reach & a Move

POSITION: (Table 26.7)

Collection of minor hand movements (less than 1 inch) for aligning, orienting, engaging 1 object with another.

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Align: Orient longitudinal axes of the two items.

Orient: Rotation about long axis to align mating features (key in a lock, for example).

Engaging: Move along longitudinal axis to mate the parts

Disengage: Complement of the engage portion position Assumption: Alignement & Orientation are done: t = 0

Position Times: Table 26.7They are a function of: Pressure to Fit, Object Symmetry, Ease of Handling

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Methods Analysis and Time:Methods Analysis and Time:3 Classes of Fit: (Table 26.8)

1) Loose: Gravity will do it, code = 1

1) Close: Light pressure needed (1 APA), code = 2

1) Tight: Heavy pressure needed (3APA+G2), code=3

3 Classes of Symmetry: (Table 26.8)

1) Symmetrical (Code = S): No matter the orientation no rotation is needed for assembly (peg in round hole)

1) Non-Symmetrical (Code = NS): There is one and only one orientation in which the parts will mate.

1) Semisymmetrical: Any position that is not S or NS Example: A turn of 45°

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Same rules as MODAPTSSame rules as MODAPTS

Need experienced operator and Need experienced operator and experienced practitionerexperienced practitioner

Allowances are applied separatelyAllowances are applied separately Will need to measure certain number Will need to measure certain number

of cycles in order to get statistically of cycles in order to get statistically significant sample significant sample

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Plus Some Additional RulesPlus Some Additional Rules

Must be repetitive work, not occasionalMust be repetitive work, not occasional Distances (or degrees or other Distances (or degrees or other

qualifying codes) determine time qualifying codes) determine time elementselements

Tables must be present in order to get Tables must be present in order to get correct time per elementcorrect time per element

Additional weight (or symmetry or Additional weight (or symmetry or other “penalties”) may be appliedother “penalties”) may be applied

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Predetermined Time Systems