Study of Manufacturing System: Work study

Showing posts with label Work study. Show all posts

Wednesday, September 27, 2017

Line Balancing (Designing Product Layout), Cycle time, Precedence diagram, Network analysis, Critical Path Method (CPM)

Line Balancing (Designing Product Layout)

The process of assigning tasks to workstations in such a way that the workstations have approximately equal time requirements

The process of deciding how to assign tasks to workstations
Minimizes idle time along line & results in a high utilization of labor & equipment

Perfectly balanced line will have a smooth flow of work

Cycle time

The maximum time allowed at each workstation to complete its set of tasks on a unit

Establishes the output rate of a line

The primary determinant of line balancing is what the line’s cycle time will be

Facilities Layout

An operation or process means how its transformed resources are positioned relative to each other & how its various tasks are allocated to these transforming resources

- The configuration of departments, work centers, & equipment, with particular emphasis on movement of work through the system

The basic objective is to facilitate a smooth flow of work, material & information

To facilitate attainment of product or service quality
To use workers & space efficiently
To avoid bottlenecks
To eliminate unnecessary movements of workers or materials
To minimize material handling costs
To minimize production time or customer service time
To design for safety

The layout decision is relatively infrequent but important

Process Selection

Refers to deciding on the way production of goods or services will be organized

- Occurs as a matter of course when new products or services are being planned, also occurs periodically due to technological changes in products or equipment as well as competitive pressures.
- Has major implications for capacity planning, layout of facilities, equipment, & design of work systems.

Description of Predetermined motion time systems (PMTS) MTM-2 Categories

GET(G)

Action of reaching out with hand or fingers to an object, grasping the object & subsequently releasing it.

The scope of GET

Starts: With reaching out to the object,

Includes: Reaching out to, gaining control & subsequently releasing control of the object

Ends: When the object is released

Three variables of GET Selection:

Case of GET—distinguished by the grasping action employed
Distance reached
Weight of the object or its resistance to motion

Predetermined Motion Time Systems (PMTS)

Also known as predetermined time standards (PTS) or synthetic time standards.

Define the time needed for the performance of various operations by derivation from pre-set standards of time for various motions & not by direct observation & measurement
Established for basic human motions, classified according to the nature of the motion & the conditions under which it is made

Example: Putting a washer on a bolt. The operator will reach to the washer, grasp the washer, move the washer to the bolt, position it on the bolt & release it

Components of a basic PMTS

The standard time

Standard time is the total time in which a job should be completed at standard performance

Standard time for a simple manual job.

Time study: Allowances

It is very difficult to determine precisely the allowances needed for a given job

Factors related to the individual (physical condition)
Factors related to the nature of the work (sitting down, posture during work)
Factors related to the environment (heat, humidity, noise, dirt, vibration)

Calculation of allowances

Rating in time study.

Rating is one of the most controversial aspects of time study.

Rating is the assessment of the worker's rate of working relative to the observer's concept of the rate corresponding to standard pace

A qualified worker is one who has acquired the skill, knowledge and other attributes to carry out the work in hand to satisfactory standards of quantity, quality and safety.

Achieves smooth and consistent movements
Acquires rhythm
Responds more rapidly to signals
Anticipates difficulties and is more ready to overcome them
Carries out the task without giving the appearance of conscious attention and is therefore more relaxed.

Time study

Recording the times of performing a certain specific job or its elements carried out under specified conditions, and analyzing the data so as to obtain the time necessary for an operator to carry it out at a defined rate of performance

Equipment required for time study

A stop-watch (mechanical and electronic)
A study board (placing the time study forms)
Time study forms (recording of substantial amounts of data)

Work sampling

Work sampling is a method of finding the percentage occurrence of a certain activity by statistical sampling and random observations.

Also known as "activity sampling", "ratio-delay study", "random observation method", "snap-reading method" and "observation ratio study“

Obtain a complete and accurate picture of the productive time and idle time of the machines

Work measurement

Work measurement is the application of techniques designed to establish the time for a qualified worker to carry out a task at a defined rate of working.

- Eliminate ineffective time.

- Set standard times for carrying out the work.

Work measurement particularly time study acquired a bad reputation in the past, especially in trade union circles.

- Directed exclusively to reducing the ineffective time within the control of the operatives by setting standards of performance.

Ineffective time within the control of management was virtually ignored

- Lack of raw materials

- Plant breakdowns

“Elimination of ineffective time due to management shortcomings precede any attack on the ineffective time within the control of the workers”

Motion Study

Systematic study of the human motions used to perform an operation

Eliminate unnecessary motions
Identify the best sequence of motions for maximum efficiency

An important avenue for productivity improvements

The most-used techniques are the following

Motion study principles

Analysis of therbligs

Micro-motion study

Charts

Method study

Method study is the systematic recording and critical examination of ways of doing things in order to make improvements

Eliminate unnecessary movement

Basic approach to method study consists of the following steps:

Select
Record
Examine
Develop
Evaluate
Define
Install
Maintain

Techniques of Work Study and Their Relationship

Method study is the systematic recording and critical examination of ways of doing things in order to make improvements.

Work measurement is the application of techniques designed to establish the time for a qualified worker to carry out a task at a defined rate of working.

Work study

“Work study is the systematic examination of the methods of carrying on activities so as to improve the effective use of resources and to set up standards of performance for the activities being carried out.”

Examine the way an activity is being carried out.

Simplifying or modifying the method of operation.

Reduce unnecessary or excess work.

Wasteful use of resources.

Setting up a time standard for performing that activity.

Total time of a job

The time taken by a worker or a machine to carry out an operation.

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