Transcript Quality Control Tools

Chapter 4

Maintenance Work
Measurement
Chapter Objectives
1.
Enable students to understand the
role standard time plays in
improving
maintenance systems
2.
Enable students to understand the
basic techniques for developing
Standard times for maintenance
work
Chapter 4 Objectives
3. Enable students to evaluate the
adequacy of the existing time
standards
maintenance
programs.
5. Enable students to use time
standards effectively in
maintenance
Role of Standard Times (ST)
1.
Aid in evaluating the performance of
workers
2. Enable effective planning and control of
maintenance resources.
3.
Aid in scheduling
4.
Enable management
productivity.
to
gauge
Time Standard
It is the required time by a qualified
worker working at standard pace to
perform a job.
Qualified worker is one who has acquired
the necessary skills, knowledge and other
attributes necessary to carry out the work
to satisfactory standard of quantity,
quality and safety.
Time standards
Standard pace ( performance ) it is
the rate that a qualified worker
naturally will achieve as an
average over the working day.
Nature of Maintenance Work
Occurs randomly
High variation
Various places
Varying environmental conditions
Work Measurement
Techniques
Direct
Indirect
Measurement
Measurement
Time
Work
Study
Sampling
Pre-determined
Motion Time
Systems
Standard Data
Comparative
Estimating
Job Standards
Estimating
Time study
Time study is performed by timing the
worker as the job is performed,
summing the times for the pertaining
elements of the job, standardizing the
observed times and adding allowances
for personal and other working
conditions.
Steps of Time Study
1. Select the job ( Standardize the job
in terms of material and the
operator )
2. Break the jobs into elements
3. Observe the job
4. Compute the basic time
( BT = OT * ( Rating/ Standard rating)
BT = Basic time, OT = Observed time
Standard rating = 100%
Steps of Time Study
5. Determine allowances
6. Establish job standards
Job Standards = BT( 1 + ALL)
ALL = Allowances
Table 4.3 provides guidelines for
allowances.
Work Sampling
Work sampling is a technique
for finding
the
percentage
occurrence of a certain activity
using statistical
sampling.
It can be applied to see the
utilization of a maintenance
worker, machine utilization, etc.
Example
A worker is observed randomly 1000
times. In 750 times he was busy. In 250
he was idle.
pq
 
pq
pp ZZ / 2

pq
p  Z / 2 nn
n
Utilization = 750/1000 = 0.75
Confidence interval for utilization is
Planning work Sampling study
1.
2.
3.
4.
5.
Define clearly the objective of the
study
Determine the population of the
study.
Activity definition
Observation form design
Observation route planning
Planning work Sampling study
6. Fix study schedule
7. Determine number of observations
8. Observation time schedule
9. Sample population preparation
10. Observer training
Predetermined Motion –
Time Systems
Pre-determined
motion
time
systems are used for setting job
standards. One of the better known
pre-determined
motion
times
systems is the Method-Time
Measurement
(MTM).
The
fundamental motion times are the
result of studying a large sample of
diversified operations
Predetermined Motion –
Time Systems
For setting a job standard, an
analyst would break the job into
the basic motions required to
perform it and then sum the
appropriate pre-determined times
for all the basic motions involved.
Procedure for Setting a
Predetermined Standard
1.
Observe the job or think it through if
it
is yet to be establish
2.
Break the job into elements and
record each element.
Obtain time units for each job
element from the tables.
3.
4. Add the total motion units for
all elements.
Procedure for Setting a
Predetermined Standard
5. Estimate allowance for personal time,
delays
and fatigue.
6. Add the performance motion time and
allowance units for a standard job
motion unit
together and compute
the motion units to actual time in
minute, hour etc. PMTS can be used
for developing job standards even
before the work get started.
Standard Data
Standard data refers to standard data
banks for various elements which
occur repeatedly in the workplace.
These elements can be put together to
develop job standards.
Developing standard Data
Several maintenance jobs in a company
may contain the same work elements. It is
not necessary to time these work elements
in every job if a reasonable job standard has
been determined from one or more
previously studied jobs. In the maintenance
department a data base can be maintained
for work element duration obtained through
previous time studies or by pre-determined
motion time systems
Estimation
Estimating is the process of using past
experience to predict future events. It
can be used to develop job standards in
an expensive way.
Advantage and Disadvantage of this
method
Comparative Estimating
( Slotting)
The basis of comparative estimation is
its reliance on a series of benchmark
jobs. These benchmark are jobs,
representative of a range of jobs, which
are similar in work requirement, types
of tools used etc. and are capable of
being measured by accepted time
measurement techniques