3.0 IntroductionConstruction firms are faced with the problem of securing sufficient work to remain viable in an industry containing many companies capable or at least willing to undertake almost any type of work for clients. Consequently, competition is severe and profit in relation to turn over tends to be relatively low.
A primary task in construction is, therefore, to bring about a climate favourable for management, workforce and resource to combine effectively and efficiently, all directed toward raising productivity and quality, i.e. achieving a given level of output with fewer inputs, while also providing high rewards for those involved. In this respect, a partial measure of productivity (the ratio of output divided by input) concentrating mainly on labour related inputs would be of prime concern to field managers. Results might be achieved firstly, by establishing clear systems for achieving continuous improvement in performance; secondly, by ensuring a well managed and supervised environment throughout; thirdly, by devising optimum methods of working for individual construction activities and work tasks; and finally, having a ready means of monitoring and ultimately controlling output as illustrated in fig. 2.
3.1 Systems
The strategic process of continuous improvement developed by the manufacturing sector aimed at achieving first class standards relies on concepts such as total quality management, bench marking, and lean production.
3.2 Total quality management (TQM)
Is the important step beyond mere implementation of quality assurance, quality assessment or simple quality control procedures in being the management led philosophy of providing
complete customer satisfaction. All levels of activity must be involved in quality procedure and standards from the individual, working gang, construction site, head office departments to the overall corporation itself including Sub contractors and other outside suppliers, all aimed at ensuring customers receive products and services at the standards expected.
There are five key principles in understanding TQM:
1. Management Commitment Plan (drive direct) Do (deploy, support, and participate) Check (review) Act (recognize, communicate, revise)
2. Employee Empowerment Training Suggestive Scheme Measurement + Recognition Excellence Teams
3. Fact Based Decision Making Statistical process control Team oriented problem solving (TOPS)
4. Continuous Improvement Systematic measurement + focus Excellence Teams Cross-functional process management Attain, maintain, + improve standards
5. Customer Focus Supplier partnership Service relationship with internal customers Never compromise quality Customer driven standards
3.2.1 Implementation of TQMTotal Quality Management emphasizes detecting potential problems before they occur.
There are five major areas of TQM, which are:
• Focus on quality and prevention of problems
• Cooperation with suppliers and customers
• Continuous improvement
• Encouragement of proper climate and employee empowerment
• Use of measurements to back decisions
In the process of TQM customers are the ones who define a quality product. Not only should
employees inspect products or services while performing duties, but companies must design
quality products. During the design process there should be input from customers, marketing and those who assemble the final product.
To be truly effective the system, in striving for continuous improvement, demands the
establishment of clear visions, mission and realistic targets, bench marked against high standards detailed in plans, specifications, work instructions, inspection tests etc including supplier involvement backed up by adequate training and communications. Subsequent achievements need to be monitored and amended. This is achieved through regular audits and rigorous acquisition of feedback data that relate to performance indicators such as;
- Reduced absenteeism levels
- Fewer defects identified
- Lowered labour turnover
- Faster progress on projects
- Improved financial results
- Higher levels of satisfaction reported by clients
- Fewer disputes
- Better relationships with Sub contractors and suppliers.
Bench marking – This originated in the manufacturing industry as systematically and
continuously measuring and comparing the firms business and management processes against leaders in the field as a means of identifying areas of potential improvement. The primary objective of comparison is to achieve ―best practice‖ principally by measuring effectiveness against quality of end product or service to the customer, productivity, cost level, safety and delivering time criteria.
Bench marking procedure: Establish function to be bench marked e.g accident rate control, variations mgt,
equipment maintenance mgt, quality mgt, disputes and resolution etc. Identify competitor for bench marking task. Collecting and gathering of data. Analysis of the information and comparison with the competitor. Implementation of the recommendations for improvement.
Lean constructionLean construction is a ―way to design production systems to minimize waste of materials, time, and effort in order to generate the maximum possible amount of value (Koskela et al., 2002)‖.Designing a production system to achieve the stated ends is only possible through the
collaboration of all project participants (Owner, A/E, Contractors, Facility Managers, and Enduser) at early stages of the project. This goes beyond the contractual arrangement of design/build or constructability reviews where constructors, and sometime facility managers, merely react to designs instead of informing and influencing the design (Abdelhamid et al., 2008). Lean construction supplements traditional construction management approaches with (Abdelhamid, 2007): (1) two critical and necessary dimensions for successful capital project delivery by requiring the deliberate consideration of material and information flow and value generation in a production system; and (2) different project and production management (planning-execution-control) paradigms. Cain (2004) suggests lean construction be defined by six goals of construction best practice:
Finished building will deliver maximum functionality, which includes delighted end users. End Users will benefit from the lowest optimum cost of ownership. Inefficiency and waste in the use of labour and materials will be eliminated. Specialist suppliers will be involved in design from the outset to achieve integration and
buildability.
Design and construction will be through a single point of contact for the most effective
co-ordination and clarity of responsibility. Current performance and improvement achievements will be established by
measurement. While lean construction is identical to Lean Production in spirit, it is different in how it
was conceived as well as how it is practiced.
The common spirit flows from shared principles:
Whole System Optimisation through Collaboration and systematic learning continual improvement/pursuit of perfection involving everyone in the system a focus on delivering the value desired by the owner/client/end-user allowing value to flow by systematically eliminating obstacles to value creation and those
parts of the process that create no value creating pull production
The differences in detail flow from a recognition that construction is a project based production where the product is generally a prototype.
As Sowards stated (2004) the priority for all construction work is to:
1) keep work flowing so that the crews are always productive installing product;
2) reduce inventory of material and tools and
3) reduce costs.
The ―lean‖ concept emphasises on producing to demand rather than through the batch process, so minimising the costly storage of work-in-progress and attending to large requirements for buffer stocks.
The aim is to eliminate all defects while using less input i.e. less labour, less machinery, less
space and less time in design, principally by reducing the number of conversion activities and
movement flows in making a product. Conversion being the operations performed in adding
value to material or information in providing the product and flow conversely representing tasks like inspections, waiting, moving, and storing. The end result would be expected to show:- A reduced proportion of non value adding activities
Less variability in quality Fewer steps, stages and linkages in the flow patterns Quicker production cycles Balance in flows (input and output) Fewer and better quality suppliers and subcontractors
Lean manufacturers improve efficiency by making products only as and when required than in bulk to be held in store waiting for a buyer, thus in many ways the construction industry finds it a familiar concept. To achieve good results with lean construction some of the common tools of production management include: just in time materials management e.g ready mixed concrete; concurrent engineering i.e the integration of the design and construction phases; employee participation in work planning and value based management i.e elimination of unnecessary processes and costs.
Figure 2: Process for continuous improvements in productivityPERFORMANCE MONITORING Work sampling Output ratesRAISED PRODUCTIVITY Lower costs Early finish Improved quality Better market standing
Production Plan
| Introduce improvements in work |
SYSTEMS Quality management Lean construction Bench markingMANAGEMENT Worker survey Delay survey WORK TASKS Goal setting Methods analysis Work measurement Work sampling
Definitions
3.3 Production and Productivity
Production is defined as a process or procedure to transform a set of input into output having the desired utility and quality. It‘s an organised process of conversion of raw materials into useful finished products as seen in figure 3.Figure 3: Production System
Productivity – is the quantitative relation between what we produce and what we use as a
resource to produce them i.e. arithmetic ratio of amount produced (output) to the amount of
resources (input). Productivity = output/inputProductivity is the amount of output per unit of input (labour, equipment, and capital). There are many different ways of measuring productivity. For example, in a factory productivity might be measured based on the number of hours it takes to produce a good, while in the service sector productivity might be measured based on the revenue generated by an employee divided by his/her salary.
Productivity is a measure of output from a production process, per unit of input. For example, labor productivity is typically measured as a ratio of output per labor-hour, an input. Productivity = Output / Input (e.g. Earned hours / Worked hours). It‘s an indicator of how well the factors of production (land, labour, machinery, capital and energy) are utilised. It measures the efficiency of a production system. Men Machines Money Materials Management Information Energy
| Goods and services |
INPUT TRANSFORMATION PROCESS OUTPUT
Construction labour productivity is a measure of work process efficiency. It can be defined as the ratio of the value labour produces to the value invested in labour. Productivity increases asneeded labour resources are minimised and wasted efforts eliminated from the work process. Productivity may be conceived of as a metric of the technical or engineering efficiency of production. As such, the emphasis is on quantitative metrics of input, and sometimes output.
Productivity is distinct from metrics of allocative efficiency, which take into account both the
monetary value (price) of what is produced and the cost of inputs used, and also distinct from
metrics of profitability, which address the difference between the revenues obtained from output and the expense associated with consumption of inputs (Courbois & Temple, (1975); Gollop, (1979); Kurosawa (1975); Pineda (1990); and Saari (2006).
3.4 Importance of national productivity growth
Productivity growth is a crucial source of growth in living standards. Productivity growth means more value is added in production and this means more income is available to be distributed. At a firm or industry level, the benefits of productivity growth can be distributed in a number of different ways:
to the workforce through better wages and conditions; to shareholders and superannuation funds through increased profits and dividend distributions; to customers through lower prices; to the environment through more stringent environmental protection; and to governments through increases in tax payments (which can be used to fund social and
environmental programs).
Productivity growth is important to the firm because it means that it can meet its (perhaps
growing) obligations to workers, shareholders, and governments (taxes and regulation), and still remain competitive or even improve its competitiveness in the market place.
There are essentially two ways to promote growth in output:
Bring additional inputs into production; or Increase productivity.
Adding more inputs will not increase the income earned per unit of input (unless there are
increasing returns to scale). In fact, it is likely to mean lower average wages and lower rates of profit.
But, when there is productivity growth, even the existing commitment of resources generates more output and income. Income generated per unit of input increases. Additional resources are also attracted into production and can be profitably employed.
At the national level, productivity growth raises living standards because more real income
improves people's ability to purchase goods and services (whether they are necessities or
luxuries), enjoy leisure, improve housing and education and contribute to social and environmental programs.Common Causes of Labour Overruns
| Internal:• Poor planning & management of work • Rework & errors • Bad estimate • Lack of training • Morale problems • Staff turnover • Material & equipment availability | External:• Overtime • Changes • Crowding • Trade Stacking • Weather • Site Access | These factors seldom occur in isolation |
Effect of Congestion (Crowding) on Labour Efficiency
U.S. Army Corp of Engineers "Modification Impact Evaluation Guide" - July 1979
Why Measure Productivity?• You can‘t correct a problem if you don‘t know it exists
• By the time the job is over, you‘ve lost the money
• You will have current information to manage and control your project
• You should correct losses arising from internal problems
• You may be able to recover losses arising from external causes
3.5 MANAGEMENT - Worker Surveys
Research findings by (Broomfield 1985) indicate that lost production time can regularly account for about 50% of the working day. The causes are usually inter connected and typically arise through unsatisfactory execution of managerial and supervisory functions surrounding short term planning ,daily and weekly scheduling, materials standardisation and control, information flow, constructability of designs, subcontractors and suppliers‘ performance, workforce, goals and competency rather than specifically in the methods of working.
Below are the kind of problems causing serious production difficulties which wherever identified will need rooting out and devising remedies.5 % 0 %
10
%
15
%
20
%
0 %
5 %
10
%
15
%
20
%
25
%
30
%
35% Crowding %% Labour Loss to Inefficiency
Lack of materials - due to waste, transport facilities, improper handling on site, misuse of
specification, lack of a proper work plan, inferior materials or excessive paperwork. Excessive weather delays Equipment breakdowns Drawings and / or specification changes Variation orders Inadequate tools or equipment Inspection delays Absenteeism Poor work planning Work repetition – due to poor finishes, negligence, poor supervision, over complicated
drawings / specifications, improper materials and poor design High labour turn over – due to low pay, casual labour, remote site, work discontinuities,
harsh/fatiguing working conditions, poor working facilities and lack of materials. Work interference Poor communication
3.5.1 Supervisor delay surveys
Here the supervisor identifies and records time losses for the gang at the end of the working day in order to reveal areas of inefficiency resulting from factors other than those due to the
performance of the workforce. Thus, the Supervisor delay survey (SDS) is aimed at determining the administrative items which are outside the supervisor‘s control, but which nonetheless affect the performance of the work group.
The SDS technique potentially provides a cost effective tool particularly useful for evaluating
managerial related problems and has the following features: It provides a link between management and Supervisors facilitating discussion of
problem and means of solutions. Delays to particular groups of workers are immediately highlighted. Information is provided on particular aspects, such as materials, subcontract
interference, drg information, plant availability, etc The whole project can be readily monitored.
The survey is inexpensive to carry out, can be done regularly and by untrained
personnel. The information is current.
Supervisor Questionnaire
| Problems causing delay | Manhours lost | |
| No. of hours | No. in a gang/crew | Labour hours |
| 1. a) Waiting for materials (on site) | ||
| b) Waiting for materials (from suppliers | ||
| 2.Waiting for tools and equipment | ||
| 3. Equipment breakdown | ||
| 4. Lack of access | ||
| 5. Changes/doing wor | ||
| 6. Waiting for information | ||
| 7. Increment weather | ||
| TOTAL | ||
| COMMENTS : |
3.6 Methods of increasing Productivity.
In construction industry, the productivity of men and machines is very important and hence
management should give proper attention to these two factors. In construction work many items such as brickwork, mixing and laying of concrete are amenable to improvement by modifications in the working methods (task based), proper sequencing of operations, adopting rational method of gauging labour and minimising the idleness of men and machinery. Similarly, the optimum utilisation of machinery and equipment (technology based) can be achieved by suitable modifications in the methods of working. The cost of supervision also can be reduced to a great degree by giving proper training to the supervisory staff and workers, adopting systematic and rational work methods at the site of work, adopting proper control system and fixing responsibility at various levels of supervisory staff.
3.7 Work task analysis (Work Study)
Work study is a major tool of productivity analysis. It consists of two major parts: i) Motion
study or method study and ii) Time study or work measurement. Experience suggests that 5 –10% incremental improvements are attainable, potentially in production efficiency through
regular application of work study techniques. The process of observing, evaluating and
improving performance in production operations is called work study which is defined in the BS glossary of terms (BS3138) as:
―A measurement service based on the techniques, particularly method study and work
measurement, which are used in the examination of human work in all its context, and which
lead to the systematic investigation of all the resources and factors which affect the efficiency
and economy of the situation being reviewed, in order to effect improvement‖
More specifically method study is used to record work procedures, provide systems analysis and develop improvements. Applications of the methodology can assist in project planning, site layout evaluation, design of temporary works, balancing plant and other resources at the work place and re-planning and progressing of production.Work measurement – (time study) is the measurement of the time required to perform a task so that an output standard of production for a worker and / or machine may be established. Both methods have gained wide acceptance in the manufacturing industry, and are increasingly finding favour in the construction industry by bringing improvement to the badly organised environment that are often found on construction projects.
In particular, the method study technique provides a disciplined procedure for recording
information on work tasks where subsequent analysis ought to reduce inefficiency, increase
productivity and raise competition.
Higher productivity which Increased productivity results in: Increase in production and hence higher profits Products produced will be cheaper Higher wages and bonus can be allowed to workers because of large profits Improvement in living standard of workers Brings prosperity in the country.
Method Study
To improve methods of productionWork measurement To assess human effectiveness To analyse and simplify
production techniques To develop economical ways of
doing a job To give improved planning and
control and better use of material,
manpower and plant / equipment To determine length of time of each job To determine the correct gang and plant
balance Check on general efficiency
Work study
Higher productivity which benefits the operatives and
Employer financially.
Method StudyMethod study is defined as:
― The systematic recording and critical examination of the factors and resources involved in
existing and proposed ways of doing work as a means of developing and applying easier and
more effective methods and reducing costs ―
Many situations arising in construction work identified through regular performance monitoring are improvable by the introduction of method study and might manifest themselves typically in the following symptoms; Recourse to excessive labour overtime Bottlenecks in the flow of materials Higher material wastage Frequent plant breakdown Fatiguing work Late programmes Poor quality and workmanship Delays to and by subcontractors Excessive errors and mistakes Shortage of resources Insufficient information Site congestion Bad working conditions High labour turnover Cost overrun Poor design of temporary work Poor site layout
ASME SYMBOLS – (American Society of Mechanical Engineers)
To record the sequence of activities on a construction site, a set of symbols is used and assists in the visualisation of the processes under study. This technique illustrates clearly and simply the work done, (flow diagram) and allows each event to be considered with a view to making improvements.
| SYMBOLS | ACTIVITY | MEANINGS |
| OPERATIONS | Actual production of work which leads to output i.e laying bricks, spreading concrete, excavation. | |
| INSPECTION | Checking, weighing, measuring, comparing for or quantity. | |
| TRANSPORT | Movement of materials, plant 0r operatives from one place to another | |
| STORAGE | Safe keeping of materials/products until required | |
| DELAY | The unnecessary storage or laying aside of materials/work due to bottlenecks in production |
Work Measurement (Time Study)
Work measurement is defined as; ―The application of techniques designed to establish
the time for a qualified worker to carry out a specified job at a defined level of
performance.‖ The aim of the technique is the evaluation of human work and provides a
fundamental part of the recording procedures described earlier under method study.
However, the applications of work measurement data are extensive and can be used in:
Determining suitable labour levels on construction activities Setting standards of machine utilisation and labour performance (standard time of
an operation) Providing the basis for sound financial incentive targets Providing a basis for cost control by fixing standard performance targets Determining the most economic from alternative methods.
The method study procedure is used to analyse and reduce the incident of such problems
in a series of steps as summarised below:
OUTLINE PROCEDURE OF METHOD STUDY
| Select/DefineThe work or activity to be studied |
| Record FactsThe existing or proposed methods of work are observed and data recorded by |
| STRING DIAGRAM | PROCESS CHARTS | FLOW DIAGRAM | MULTIPLE ACTIVITY CHARTS |
To all these questions ask WHY?
| Develop From the examination of results the most economical and efficient method best suited for the particular situation |
| MaintainBy checking periodically that the installed new system/method is running satisfactory, and if necessary, prepare to effect slight improvements where needed |
Higher productivity
| ExamineThe data collected critically by the questioning technique to eliminate unnecessary activities and delays |
| WHAT Is achieved ? PURPOSE WHERE Is it done or obtained from? PLACE WHEN Will it be required? SEQUENCE WHO Should do it? PERSONS HOW Should it be done? MEANS |
| InstallThe selected method and explain its working to the Supervisors and operatives, and foster their cooperation |
3.8 Procedure of carrying out Time study
It is necessary to begin the study by recording all the existing facts about the job,
including the working conditions, degree of skill, effort etc required. The work study
officer should watch the operative complete one or more cycles of the work to be studied
to decide what the ―elements‖ of the job are and exactly where the ―break points‖ occur.
1. Choose the job and extent of it (when it starts and finishes). Obtain and record
information about the job, the operator and working conditions.
2. Break the job down into elements and decide break points eg collect
component, measure, cut, fix, etc (the break point being the points between
the completion of one element and the starting of another).
3. Record the elements in order of execution on the Time study recording sheets.
4. Time each element by the repetitive or continuous timing method and record
in the time study recording sheet. Observed time (O.T) or Watch Reading column (W.R)
5. Simultaneously to timing an element, a rating R, should be recorded in the RColumn.
6. Calculate the basic or normal time for a work task as Observed time x assessed rating
Standard rating
7. calculate the standard time as:
Standard time = Basic time + relaxation allowance + contingency
= Standard hours or standard minutes.
This would represent the proper time for a qualified worker working at a standard rating
to accomplish a task and once this is obtained, the worker will have achieved standard
performance. Standard performance is defined as ―The rate of output which workers will naturally achieve without over exertion as an average over the working day or shift provided they are motivated to apply themselves to their work‖.
Rating - The rating corresponding to the average rate at which qualified workers will
naturally work at a job, provided they adhere to the specified method and are motivated
to apply themselves to their work.. If the standard rating is maintained and the appropriate relaxation is taken, a worker will achieve standard performance over the working day or shift.
The work study officer must be experienced to make fair judgment in the different speeds
of movement, effort, consistency in order to be able to differentiate between fast, slow or
medium rates of doing work..
The BS rating scale provides a suitable description for varying levels of worker
performance and is divided into five – point graduations with 100 representing standard
rating.
| Thus; 0 | - | represents inactivity |
| 50 | - | very slow, unskilled, unmotivated |
| 75 | - | not fast, average skill, disinterested |
| 100 | - | brisk, qualified, skilled, motivated |
| 125 | - | very quick, high skill, highly motivated |
Qualified worker -Average worker who has the attributes necessary for the job for
which he/she is employed i.e. degree of intelligence, skill and physical fitness.
STEPS IN TIME STUDY
| SELECTThe job to be timed |
| OBTAIN AND RECORDDetails regarding method, operation, job and working conditions |
| DEFINEThe elements, break the job into elements convenient for timing |
| MEASURETime duration for each element and assess the rating |
| EXTENDObserved time into normal time (basic time) |
| DETERMINERelaxation and personal allowances |
| COMPUTEStandard time for the operation for defined job or operation |
Element – distinct part of a specified job selected for convenience of observation,
measurement and analysis.Cumulative timing and fly back timing
Cumulative timing – Watch runs continuously through out the study. At the end of each
element the watch reading is recorded and individual element times are obtained by
successive subtraction after the study is completed.
Fly back timing – the hands of the stop watch are returned to zero at the end of each
element and allowed to start immediately, the time for each element is obtained directly.Abstracting – This is the collection of the basic times for each repeated element which
are then added together, the element totals are then divided by how many times they have
been repeated to arrive at the average basic times.
Factors which affect the observed time- Quality of tools used
- Type and quality of materials worked on
- Working conditions
- Learning period required before task becomes familiar
- Interruption of supply of materials
- Quality of working days
- Supervision
| - | Quality specification |
| It‘s advisable to take a large number of studies to get a representative sample. |
Importance of work study
1. Work study is a means of enhancing the production efficiency (productivity)
of the firm by elimination of waste and unnecessary operations.
2. It is a technique to identify non-value adding operations by investigation of all
the factors affecting the job.
3. It is the only accurate and systematic procedure oriented technique to establish
time standards.
4. It is going to contribute to the profit as the savings will start immediately and
continue throughout the life of the product.
5. It has got universal application.
Advantages of work study
- It helps to achieve the smooth production flow with minimum interruptions.
- It helps to reduce the cost of the product by eliminating waste and
unnecessary operations.
- Better work management operations.
- Meets the necessary consultant.
- Reduction in rejections and scrap and higher utilisation of organisation
resources.
- Helps to achieve better working conditions.
- Better workplace layout
- Improves upon the existing process or methods and helps in standardisation
and simplification.
- Helps to establish the standard time for an operation or job which has got
application in power planning, production planning.
Contingencies
To obtain the final standard time it is usually prudent to include additional time which
cannot be determined accurately but which will almost certainly occur. The following
contingencies are typical and can either be added as a percentage to the basic time or as
absolute time itself.
| - | Adjustment and maintenance of tools |
| - | Waiting time caused by subcontractors, machine breakdowns, lack of |
materials etc.
- Unexpected site conditions e.g. bad ground, high winds, bad weather.
- Learning time
- One-off tasks
- Design changes.Allowances:
| - | Process allowance |
| - | Rest/fatigue/relaxation |
Process allowance-This is a process or unavoidable delay allowance which is given so
that the worker will not lose earnings due to an enforced delay over which he has no
control, eg cleaning of tools or plants.
Rest allowance - These vary with every performance and condition of work, and are
added so that a worker can keep physically fit to perform an operation for an allotted
time. This is sometimes termed ―fatigue allowance‖.
Items taken into account are as follows:
a) Basic 9% minimum - This is the minimum requirement for the personal needs of
every person regardless of work. (Men 9%, women 12%).
(b) Variable rest allowance- Position of body, 0 – 7%. This will vary from the sitting in a
comfortable chair to working in a cramped position under stairs or similar.
(c) Working conditions up to 15%- Include such items as; noise, bad light, dust heat,
etc. The difference in conditions numerous and can range from working in a hot boiler to
excavating in a deep muddy wet trench.
(d) Mental strain, up to 8% - This relates to the concentration that needs to be applied to a
piece of work or a task. For example a tower crane driver positioning heavy loads or a
painter doing detail design.
(e) Manual effort up to 20% - This is the amount of muscular force used from
demolition to manual unloading and carrying materials. (light weights 0 – 10%,
heavy weights 11 – 20%) .
(f) Monotony up to 5% (degree of repetitiveness)- By adding up the related percentage
given to a task, a total rest allowance is obtained; if this figure is high, consideration
should be given to reducing it as would appear that the task to be carried out by the
worker is too arduous, about 40% is an approximately maximum generally acceptable.
Example 1
The element times (in minutes) for 4 cycles of an operation using a stop watch are
presented below:
| Elements | Cycle time in minutes |
| 1 | 1.5 1.5 1.3 1.4 |
| 2 3 4 5 | 2.6 2.7 2.4 2.6 3.3 3.2 3.4 3.4 1.2 1.2 1.1 1.2 0.51 0.51 0.52 0.49 |
Calculate standard time for the operation if;
(i) Elements 2 and 4 are machine elements.
(ii) For other elements, the operation is rated at 110%
(iii) Total allowances are 15%.
Solution:
| Elemen t No | Cycle time Minutes | Average Cycle time | Rating % | Normal time =Avg time x rating |
| 1 2 3 4 5 | 1 2 3 4 1.5 1.5 1.3 1.4 2.6 2.7 2.4 2.6 3.3 3.2 3.4 3.4 1.2 1.2 1.1 1.2 0.51 0.51 0.52 0.49 | 1.425 2.575 3.325 1.175 0.505 | 110 m/c element 110 m/c element 110 | 1.425x1.1=1.568 = 2.575 3.325x1.1=3.658 = 1.175 0.505x1.1=0.555 |
Normal time for the cycle = 9.531
Standard time = 9.531 + (0.15x 9.531)
= 10.961 standard minutes
Example 2
The observed times and the performance ratings for five elements are given below,
Compute the standard time assuming rest and personal allowance as 15% and
contingency allowance as 2%.
| Element 1 2 3 4 5 |
| Observed time (Min.) 0.2 0.08 0.50 0.12 0.10 |
| Performance rating 85 80 90 85 80 |
Solution:
| Element | Time(Observed) | Rating | Normal time |
| 1 2 3 4 5 | 0.2 0.08 0.50 0.12 0.10 | 85 80 90 85 80 | 0.2 x 85/100 = 0.170 0.08 x 0.8 = 0.064 0.50 x 0.9 = 0.450 0.12 x 0.85 = 0.102 0.10x80 = 0.080 |
| Total | 0.866 |
Normal time per piece = 0.866
Rest and personal allowance = 0.15 x 0.866 = 0.1299
Contingency allowance = 0.02 x 0.866 = 0.0173
Standard time = Normal time + Rest and personal allowance + Contingency
Allowance
= 0.866 + 0.1299 + 0.0173
