The MTM1, Method Time Measurement, is an analysis of human movements in the context of production operations. From the motion analysis tables, operating times are predetermined for each basic movement and thus deduct the total standard time of the production cycle.
By definition, “MTM1” is a procedure that analyzes manual operations and assigns to each basic movement a standard predetermined time based on the nature of the movement and the conditions in which it is performed. 1 “
Based on the work of Taylor and Gilbreth at the beginning of the Twentieth Century, Team Maynard, Stegemente and Schwab in partnership with Westinghouse Electric Corporation, developed the MTM1 (Method Time Measurement) to 19403.
In 1945, the United States Office of consultancy in the organization “Methods Engineering Council“, completed the studies undertaken and, as of 1947, the MTM is broadcast first in the USA and then worldwide. The MTM1 was introduced in France in 1951 and was created in 1952 the Association MTM française. All national MTM1 actions are now coordinated by the MTM1 International Executive Board, which is the only one to issue an official diploma for agents specialising in MTM1, known as the Stémistes.
The MTM1 principle
The MTM1 method allows, by decomposing all the basic movements necessary for a task, to determine the standard time of an operation. Originally, Gilbreth, starting from his work on the basic movements named Therblig, grouped these movements into 4 categories:
- The movements of the upper limbs: reach, grasp, move, position and release, but also turn, apply pressure, disengage and crank movement
- Visual movements: Examining and moving the look
- The movements of the lower limbs: from the foot or the leg
- Movements of the body: moving (walking, not sideways, rotating the body) or bending (bowing, stooping, kneeling on the ground, kneeling, sitting, rising)
Each of these elements is characterised by different elements:
- A precise definition
- A list of motion variables: amplitude, effort…
- Weights related to the simultaneous movement
The unit of measurement
The unit of measurement of the MTM tables is the TMU, time Measurement unit, in French the MHC (one hundred thousandth of an hour). It is expressed in a hundred thousandth of an hour is equivalent to:
- 100 000 TMU = 1 hour
- 1 minute = 1 667 TMU
- 1 second = 27.8 TMU
- 1 TMU = 0.00001 hour or 0.00006 minute or 0.036 seconds
This methodology, which is only applicable to manual operations, has many applications. Among these, we find:
- The development of the working standards.
- Calculating working times and therefore balancing tasks.
- The choice of operating modes.
- The design and ergonomics of workstations.
- Decomposing each of the task’s movements.
- Determination of variables for each of the movements.
- Codification of each movement.
- Restoring the time required for movements using tables.
- Determination of the time of the operation.
No coefficient of performance required.
Only one observation is enough to determine the standard time.
Method that is now familiar in the industry.
One can compare simply different ways of doing and compare theoretical values with practical values.
Allows you to determine a ” priori ” time and can be used as soon as a process is designed.
Not taken into account the characteristics of each: sex, age, size, motivation…
No taking into account the working conditions: noise, light…
Works only for manual processes.
A rather complex and long tool to implement by its precise degree: it is usually necessary to count a working day to analyze 1mn cycle.
The tables of the MTM1
The recognized tables are under the version MTM-Data Card 101 A, edition 1955.
The main variables
Most tables have a variable distance. Depending on it a time is granted. Note that distances of more than 80cm are considered not to be possible without a total movement of the body.
Adding movement for the reach and move tables
In the move and reach tables, it is added for some movements the letter “m”:
- Type 1: The hand moves at the beginning of movement: M before R is mR.
- Type 2: The hand moves at the end of the movement: m after R is Rm.
- Type 3: The hand moves at the beginning and end of movement: m before and after R is mRm.
In some tables, a notion of effort is added. So just identify it and take the associated values.
Reach – R
Move your hand or fingers to a defined place. It corresponds to the Therblig ” Transport empty “. The variable that determines the movement is the nature of the destination, as well as the presence or absence of acceleration or deceleration.
Five case classes are noted:
- Class A: reach an object always placed in the same place, or object located in the other hand or on which the hand rests.
- Class B: Reach an isolated object whose location may vary slightly from cycle to cycle.
- Class C: Reach an object located in the middle of others causing a search.
- Class D: Reach a very small object, or requiring precaution and precision.
- Class E: Move the hand to an indefinite position either to ensure the balance of the body, to prepare the next movement, or to clear the work area
For combinations other than A and B, the following formulas must be used5 :
- mRC = RC – (RB-RBm)
- mRD = RD – (RB – RBm)
- mRE = RE – (RB – RBm)
- REm = RE – (RB – RBm)
The third type is impossible with classes C and D because they require too many concentrations. This gives us for the other classes:
- mRAm = RA – 2 * (RB – RBm)
- mRBm = RB – 2 * (RB – RBm)
- mREm = RE – 2 * (RB – RBm)
Move – M
Move an object with your hand or fingers to a place. It corresponds to the Therblig ” Transport loaded “. The variables are the same as to achieve with in addition the concept of weight. We find 3 classes of movements:
- Class A: Move the object to the other hand or to a stop.
- Class B: Move the object to an approximate or undefined location.
- Class C: Move the object to a specific location or with caution.
It is calculated in the following way:
TMU = static constant + dynamic coefficient * TMU
Example for a weight shift of 10kg to 12cm
M12B10 = 9 + 1, 27 * 7.7 = 18,779 TMU or 0.67 sec
Turn – T
The hand, empty or loaded, the wrist and the forearm revolve around the main axis of the forearm. The maximum rotation is 180 ° because physiologically we can do no more.
Grasp – G
Fingers or hand provide partial or total control of one or more objects. Variables are the type of “ grasp “, the nature of the object to grasp, its localization…
Position – P
These are generally short hand movements (less than 3cm) to align (longitudinal positioning), Orient (rotation axis of objects) or engage one object in another. The variables are the force of pressure for the engagement, the symmetry of the shapes, the depth of insertion and their simplicity of handling.
- For P1SE: The alignment accuracy must be between 1, 5mm and 6mm
- For P2SE: The alignment accuracy must be less than 1.5 mm
It depends on the shapes of the parts at the point of engagement and the importance of the orientation necessary to make the profiles coincide. We find three cases:
- S for symmetrical: a round in a round.
- SS for Semi-symmetrical: Case between S and NS.
- NS for Non-symmetric: Inserting a key into a lock.
The handling :
It results from the Shape, the nature, the conditions of use of the object.
Release – RL
Fingers or hand give up control of an object. It can release them by simply opening the fingers or or only by no longer having contact.
Disengage – D
A gesture made to break the contact between two objects previously held together by a force. It is characterized by the fact that there may be an involuntary movement when there is no more resistance.
The hand describes a circular plane trajectory while the elbow and upper arm remain motionless. The variables are the number of revolutions, if the movement is continuous or intermittent, the effort and the amplitude of the movement.
Apply Pressure – AP
It is a muscular force applied to an object with or without movement. Usually applied by fingers or hand, this table is valid for pressure exerted by all parts of the body (foot…).
Eye Travel – and
Move the eyes from one point to another, with the head stationary.
The exact formula is:
TMU = 0.285 * Angle of eye rotation in degrees.
The approached formula is:
TMU = 15.2 * T/D
- T: Distance between the 2 points viewed
Eye Focus – EF
Fix the look on an object to make sure that it has certain characteristics that are easy to recognize and that there is no movement of the axis of the vision.
The time here is universal 7.3 Cmh
- In addition, the MTM1 adds a reading parameter and indicates a standard time of 5.05 TMU for 1 word or for a paragraph of 200 words a time of 1010 TMU or about 36 seconds.
- The normal area of vision is a circle 10 cm in diameter at a distance of 40 cm from the eyes.
Movements of the lower limbs
- Foot Motion – FM: The foot pivots around the ankle (typical action on a pedal). The toe of the foot moves vertically; The range of motion is limited to 10cm to avoid abnormal fatigue.
- Leg Motion – L: They concern the movement of the foot forward, back or side (in the sitting position, the knee serves as a pivot, in standing position, the hip serves as a pivot), moving the knee to the side in a seated position.
- Horizontal Movements: walking, side steps and body rotations.
- Vertical Movements : Stand up, sit down.
These are the basic movements carried out simultaneously or combined, most often applied for hand movements.
The combined movements
By definition, combined movements are several basic movements performed by the same part of the body simultaneously. To consider these cases, the main movement (the longest in TMU) must not be hindered by the other combined movements. We consider then that the time of the operation is the longest time, the others being neglected.
For example, if during a 30cm movement of the hand, I come to grab a Part at half of it and without hindered this movement, then the total time will only be set time to move the hand from 30cm.
By definition, simultaneous movements are several basic movements performed by different parts of the body at the same time. Usually applied for hand movements, with some simultaneous movements being harder than others, they are classified according to 3 levels:
- Easy to perform at the same time.
- Can be done at the same time with a little practice and training.
- Difficult to perform at the same time.
The ” limiting principle ” indicates that the total time of an easy or need-to-exercise simultaneous movement (case 1 and 2) is the time of the greatest movement. The time taken for a difficult combination (case 3) is the addition of all times.
- It is considered simple to reach something with both hands. The time of the operation will be the time put by the movement of the longest hand.
- It is considered very difficult to position 2 objects at the same time. The time of the operation will therefore be the addition of the times of each of the positions.
It also includes two other factors:
- For the movements of disengagement and positioning: We find the classes D, difficult to manipulate and E, easy to manipulate.
- For the movements to grasp, move or reach: we find the W-classes, in the normal field of vision, O, outside the normal field of vision.
- Class 3 to disengage (D3) is normally considered difficult (case 3). However, all classes can be considered difficult if there is a risk of injury or damage to the parts.
- Class 3 of position (P3) is still considered difficult (case 3).
- Letting go is always considered easy.
- Applying pressure can have the 3 cases and therefore each situation is to be analyzed on a case by case basis.
- Turning is generally considered easy except with disengagement or when it needs to be controlled (high degree of accuracy – judgement left to the observer).
Source: C. M. Schlick (2013)-Modeling and optimizing manual work processes with MTM
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3 – W. Rohmert (1971) – Predetermined motion-time systems
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