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Predetermined Motion Time Systems

Sections:

1. Overview of Predetermined Motion

Time Systems

2. Methods-Time Measurement

3. MTM-1

4. Maynard Operation Sequence

Technique (MOST)

Chapter 14

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Overview-PMTS Defined

An alternative to direct time study that does not require performance rating.

PMTS is a database of basic motion elements and their associated normal time values, together with procedures for applying the data to analyze manual tasks and establish standard times for the tasks

Basic motions include:

o Reach

o Grasp

o Move

o Release

The time required to perform these basic motions usually depends on certain work variables (reach and distance; move and weight of object; etc.).

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PMTS Procedure

To apply PMTS to a task the analyst must accomplish the following steps:

1. Analyze method that would be used to perform the task

The method is described in terms of basic motion elements

2. Retrieve normal time values for each motion element

Sum the element times to determine the task normal time

3. Evaluate method to make improvements by

eliminating motions

reducing distances

using both hands simultaneously etc.

4. Apply allowances to determine standard time

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PMTS Levels and Generations

First-level PMT Systems use the basic motion elements

Reach, grasp, and move used separately to define

the task

Higher-level systems combine several motion elements

into motion aggregates

Reach and grasp combined into one element called

“get”, “Put” which combines move and position

There are various types of PMT systems, and these types

are variety in the basic motion elements.

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PMTS Levels and Generations (CONT.)

First-level systems were chronologically the first to be

developed and are called first generation PMTS (MTM-1)

MTM-2 is the second generation of PMT systems was

developed. MTM-3 is the third generations.

Some of Predetermined Motion Time systems:

• Method Time Measurements (MTM)

• Maynard Operation Sequence Technique (MOST)

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Comparisons

First-level PMTS

Most accurate

High application speed ratio

Most suited to highly repetitive short cycles

Basic motion elements

Very detailed

Highest flexibility

Higher-level PMTS

Less accurate

Less time to set standards

Longer cycle times feasible

Motion aggregate

Less detailed; easier to apply

Less flexible

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Methods-Time Measurement (MTM)

MTM is a procedure which analyzes any manual

operation or method into the basic motions required to

perform it and assigns to each motion a predetermined

time standard which is determined by the nature of the

motion and the conditions under which it is made

Time units are TMUs (Time Measurements Units)

1 TMU = 0.00001 hr = 0.0006 min = 0.036 sec

1 sec = 27.8 TMU

MTM is a family of products available through the MTM

Association (www.mtm.org) and the original MTM is now

called MTM-1.

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Methods-Time Measurement

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MTM-1

Operates at the basic motion element level in our pyramidal structure of work (same in therbligs)

Most MTM-1 basic motions involve hand and arm movements

Also includes elements for eye, leg, foot, and body actions

More appropriate for tasks that are highly repetitive and cycle times are less than 1 min

Time unit in MTM are called TMUs (time measurement units).

1 TMU = 0.00001 hr = 0.0006 min = 0.036 sec

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MTM-1: Motion Elements

1- Reach (R): Basic motion elements

involves moving the hands and fingers to the

new destination.

R1C takes 3.6 TMUs

Normal Time (Tn)= 3.6 * 0.036 = 0.130 sec

Example:

Motion element

Symbol

Case and

description

Distance

(inches)

Normal Time in

TMU

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G1C3 takes 10.8 TMUs

MTM-1: Motion Elements (Cont.)

2- Grasp (G): Use fingers and hands to

gain control on one object or more.

Example:

Normal Time= 0.389 sec

Motion element

Symbol

Case and

description

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M6B12.5 takes

TMU= Constant + Factor * (TMU value from

table)

= 3.9+1.11(8.9)=13.8 TMUs

MTM-1: Motion Elements (Cont.)

Normal Time= 13.8 * 0.036= 0.497 sec

Example:

3- Move (M): Using the hand and fingers to

relocate an object

Motion element

Symbol

Weight

up to Type of

case

Distance in

inches

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Round peg in a round hole: S(ymmetrical)

Key inserted in a lock: N(on)S(ymmetrical)

P3NSD takes 53.4 TMUs

Example:

Normal Time= 53.4* 0.036= 1.92 sec

4- Position (P): A relatively short hand motion employed to align, orient or engage

the object to another.

MTM-1: Motion Elements (Cont.)

Motion element

Symbol class

Symmetry Easy handle OR

Difficult

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RL1 takes 2.0 TMUs

Example:

Normal Time= 0.072 sec

5- Release (RL): A hand and finger

motion element in order to release

(free) an object

MTM-1: Motion Elements (Cont.)

6- Disengage (D): A hand and finger motion

element in order to separate one object from

another one (disassemble)

D3E takes 22.9 TMUs

Example:

Normal Time= 0.824 sec

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Example (MTM-1)

Q1. A worker seated at a table performs a REACH. The sought-after

object is jumbled with other objects in a tote pan, and the distance of

the reach is 18 in. Determine the MTM-1 symbol and normal time in

TMUs for this motion element.

MTM-1 symbol = R18C (From Reach table)

Solution:

So, the normal time (from Reach table) = 18.4 TMU

The normal time in sec = 18.4 TMU * 0.036 = 0.662 sec

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Example (MTM-1) (Cont.)

Q2. A work element in a manual assembly task consists of the

following MTM-1 elements: (1) R16C, (2) G4A, (3) M10B5, (4) RL1,

(5) R14B, (6) G1B, (7) M8C3, (8) P1NSE, and (9) RL1. (a) Determine

the normal times in TMUs for these motion elements. (b) What is the

total time for this work element in sec?

(a) The individual motion element times are given as follows:

(1) R16C, Tn = 17.0 TMU (2) G4A, Tn = 7.3 TMU

(3) M10B5, Tn = 2.2 + 1.06(12.2) = 15.1 TMU (4) Rl1, Tn = 2.0 TMU

(5) R14B, Tn = 14.4 TMU (6) G1B, Tn = 3.5 TMU

(7) M8C3, Tn = 2.2 + 1.06(11.8) = 14.7 TMU (8) P1NSE, Tn = 10.4 TMU

and (9) RL1, Tn = 2.0 TMU. Total = 86.4 TMU.

Solution:

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Example (MTM-1) (Cont.)

(b) The normal time of the manual assembly task in second:

Total normal time of the task in second = 86.4 TMU (0.036) = 3.1 sec

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Maynard Operation Sequence Technique

(MOST)

MOST is a high-level PMTS based on MTM

Same time units as MTM: TMU

MOST is a product of H.B. Maynard and Company (an educational and consulting firm), Pittsburgh, Pennsylvania

(www.hbmaynard.com)

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MOST in the Work Pyramid

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Basic MOST

Focused on work involving the movement of objects (e.g.,

parts, tools) from one location to another in the workplace

Uses motion aggregates

Called activity sequence models

Three activity sequence models:

General move – object moved freely in space

Controlled move – object remains in contact with a

surface

Tool use – use of hand tools (e.g., hammer,

screwdriver)

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Activity Sequence Model

Consists of sequence model parameters, which correspond roughly to basic motion elements

Sequence model parameters for General Move:

A – Action distance (move hands or feet) – horizontal body motions

B – Body motion (sit, stand up) – vertical body motions

G - Gain control (closely related to grasp)

P – Placement (e.g., position, lay aside, orient)

Standard sequence in General Move:

A B G A B P A

ABG: to get an object;

ABP: to move the object to a new location;

A: return to original position

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Normal Time in TMU = 10 * (sum of index values)

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Example: General Move

Develop the activity sequence model and determine the normal time for the following work activity: A worker walks 5 steps, picks up a small part from the floor, returns to his original position, and places the part on his worktable.

Solution

A10B6G1A10B0P1A0

where A10=walk 5 steps;

B6=bend and arise;

G1=gain control of small part;

A10=return back;

B0=no body motion;

P1:lay aside part on table;

A0=no motion

The sum of index values: 28.

Normal time: 10*28=280 TMUs = 280*0.036 = 10.1 sec

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Controlled move

Used when an object is moved through a path that is somehow constrained. In this case we need additional three new parameters beside previous parameters of the general move (A, B and G):

M-Move, used to describe any manual body motion require to move an object with controlled condition.

X-Process time: since it may include the operation of machinery.

I-Align: this parameters is used when the manual motions are performed at the end of the control move to align object

Standard sequence in controlled move:

ABGMXIA

ABG: to get an object;

MXI: to move the object followed by a process time and alignment,

A: to return

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Controlled move (Cont.)

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Controlled move (Cont.)

Type of Milling Machine

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Controlled move (Cont.)

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Example: Controlled move

Q1. Develop the activity sequence model and determine the normal time for the following work activity: A worker takes 2 steps, grasp the waist-level feed lever on the lathe in stand position, pulls up the lever approximately 15 cm to engage the feed. Process time to turn the part is 25 sec and aligns the lever with one specific speed and then he needs to return the original workstation with 5 steps.

Solution:

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Example: Controlled move

Q2. Develop the activity sequence model and determine the normal time for the following work activity in second: A machinist standing in front of his milling machine, grasps the waist level feed lever on the machine, and rotates the lever one crank to engage the feed. The process time to mill the part is 50 sec. There is no alignment and no action by the worker at the end of the process time.

Solution: