Control Mechanisms

Control Mechanisms:
Handle is offset from and parallel to Shaft
For high turning speeds up to 200 r.p.m
For rapid control turns
For manual movement of heavy loads

Hand Wheel>
Circular control gripped by the rim preferable with both the hands.
For low turning speeds (rpm or less)
For very accurate partial turns
For a torque above 15 inch/Ib
For turn not exceeding 900

Rotary control> Operated by gripping it freely on both sides with the fingers of one hand
For making fine adjustments
For light loads (up to 22 inch/Ibs)
As rotary selector switch

Rod like
Hand operated
For small effective travel
For fast movement which does nor require accuracy
For medium heavy load

Lever which works in two directions
For continuous simultaneous control in two dimensions
For rapid multiple switching operations

Toggle Switches>
Miniature levers
300–400 movement on either side of the central position
Not useful for discreet adjustment
Used as selector switches. Should not be used for more than three switching positions

Pedal Hand grip>

Rotary lever
Limited area of movement
Gripped near the shaft
For rotary multiple switching

Rotary Lever>
Attached to a shaft to allow complete turn
When a fairly high force is required
For powerful force

Reciprocating control
Operated by one foot
For continuous controlling
For on off or start or start stop switching

Push Button>
Reciprocating control. Positive action in one direction only.

Rudder Bar>
Reciprocating control. Pivoted about its center. Operated by foot. Example: Treadle
For accurate control and little force.

Methods Time Measurement (MTM):

The MTM system was developed from motion picture of industrial operations, and the time standards were first published in 1948. This system is defined as a procedure which analyses 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 it is made.

Beginning in 1963 the first new member of MTM system called General Purposes data (MTM–GPD) was introduced and at that time MTM – 1 used to designate the original basic MTM system. Today the family of systems includes MTM – 1, MTM – 6PD, MTM – 2, MTM – 3, MTM – V, MTM – M, MTM – C , & 4M DATA

MTM – 1

It uses data tables. The unit of time used in these tables is 0.00001 hour, and is refereed to as one time measurement unit (TMU). Thus equals 0.0006 minutes.

The basic elements are:

1) Reach
2) Move
3) Turn
4) Apply pressure
5) Grasp
6) Position
7) Release
8) Disengage
9) Eye times
10) Body, Leg and Foot Motions
11) Limiting Motions.

MTM – 2

Of the family of MTM system MTM – 1 is the most accurate provides the most detailed methods description but requires the longest tome for analysis.

MTM – 2 was developed by constructing motion combination from basic motions of MTM -1. It has a smaller number of distance ranges and fewer cases of control than MTM – 1. Although the analysis can be made more quickly than with MTM – 1, accuracy and method description are not as great. MTM – 2 is suitable for work that is not highly repetitive and for elements that are not less than 1 min long.

The system consists of none categories of manual motions:

Motion Symbol

1) Get G
2) Put P
3) Apply pressure A
4) Re-grasp R
5) Eye Action E
6) Crank C
7) Step S
8) Foot Motion F
9) Bend & Arise B

(Get & put are the only variable categories and only 37 times standard appear on MTM – 2 Data Card)

Speed of analysis with MTM – 2 is twice as fast as with MTM – 1.

MTM – 3

It is the simplest of the MTM systems and is intended for use with long cycle short run operations. The MTM – 3 System consists of four categories of motions:

Motion Symbol

1) Handle H
2) Transport T
3) Step & Foot Motion SF
4) Bend & Rise B

Of these, the two motions Handle & Transport have variable categories and only ten time standards appear on the MTM – 3 data card.

Speed analysis with MTM- 3 is seven times as fast as with MTM – 1 and three times as fast as with MTM – 2.

Limitations: MTM – 3 should not be used for analyzing manual motions with a frequency higher than 10 or a sequence of eye movements. In such cases MTM – 2 or MTM – 1 should be used.

MTM – 6PD: It has been derived form MTM – 1 time values for basic data. This is a building block process for development of standard data.

MTM – V: It is designed for use with machine tool operations including such items as setting machine tools, handling tools and work, process, measuring and gauging, operating the machine and clearing work pieces and equipment.

MTM – M: It is a second level Functional System of original data designed for the analysis and measurement of manual assembly work performed under stereoscopic magnification of 5 to 30 power.

MTM – C: It is a two level data system synthesized from MTM – 1 and is used for clerical related work. Its use includes desk top operation and such tasks as filling, typing, key punching and data entry.

4D Data (Micro-Matic Methods & Measurements): It is a computer aided means of applying MTM – 1. The computer takes over much of the work of the analysts and assists in standard data development, recalling elements, and mass changing standards.