4. Difficulties in meeting the sales order
Planning is pinpointing manufacturing dept.
for under utilization of machines
Manufacturing are blaming improper
scheduling
But sales are growing and GM wants to know
current m/c utilization and future capacity
requirements
And GM is interested in building in two
months inventory stock
Current problems
6. Steps for work sampling
Classification and grouping of activities
Designing of forms
Properly randomized times of
observation were obtained
Activities were observed and data were
recorded
Pilot study to compute number of
observations to get desired accuracy and
confidence level
7. Work categories
Machine
working
Set up, loading
and unloading,
machining,
inspection and
cleaning
Machine not
working
Breakdown
Electrical
Mechanical
Waiting for
tools
To bring tools
Grinding of
tool
Waiting for
material
Waiting for
operator
Personal work
Machine
interference
No reason
For
instructions
Machine open
8. Group Machine type No of
Machine grouping
machines
1 Automates 10
2 Lathes 13
3 Hobbing 6
4 Milling 3
5 Drilling 9
9. Random number table was used
950, the first digit indicates the hour and
second indicates fraction of the hour
That is 950 would mean 9.30 am
12 observations were made in a day
Random no. falling outside the working
hours and excluded
Obtaining random numbers
10. Cares taken during study
◦ Observations at proper time
◦ Avoid biasing
◦ Record what observed without an anticipation
◦ Random approach during taking observations
Pilot study was carried out to find approx. value
of p
On the basis of calculated p value for different
groups of machines actual observations needed
were calculated using the formula
n=4(1-p)p/L², L=error%
Pilot study
11. Group no No of observations
1 815
2 1025
3 1115
4 1055
Drilling machines were excluded from study as from
sample study it was revelled that they were not critically
loaded and had ample capacity to take up additional load
Total observations for each group
12. category automats Lathes Hobbers Millers
Working 69.70 41.38 51.46 47.10
Idle for operator 15.82 33.00 47.91 39.85
Idle for material 2.30 3.62 0 4.35
Idle for tool 1.22 2.10 0 1.52
Breakdown 7.69 14.73 0 0.87
Machine open 2.08 4.33 0 2.83
Others 1.21 0.9 0.6 3.48
Summery of the results of study
13. 80
70
60
50
40
30
20
10
0
working
operator
material
tool
breakdown
machine open
others
Poor machine utilization for all machines except automates
Results and discussion
14. contribution to total time
machine open
working
breakdwon
6%
2%
operator 52%
34%
material
3%
tool
1%
others
2%
Contribution to total time
15. Idle for operator is major about 34% total
time which requires in detail further study
Reasons for operator idle time
◦ Time waste in personal work
◦ Put on other jobs like material handling
◦ Too early cleaning of machine at the time of shift
end
◦ Machine interference in case of Hobbing
machine(47.91%)
Idle for material is another major concern
Breakdowns are on higher side
Discussions
16. Group 1 2 3 4
m/c hours / year 45000 58500 27000 13500
Allowances % 16 22 20 15
Net hours/ year 37800 45630 21600 11500
Allowances to get net machine hours available
Activity 1 2 3 4
Set up 5 4 5 5
Operators personal time,
5 6 8 5
Interference, etc.
Breakdowns 5 8 5 1
Waiting for tools 1 2 2 2
Waiting for material 0 2 0 2
Total 16 22 20 15
Machine time available
17. Considerations
◦ Grouping of similar instruments
◦ List of components being made was made and
this was in turn used to calculate load due to
particular part.
◦ Operation time was taken from time study data
◦ For unavailable time study data, time was
estimated
◦ For some operations stop watch time study was
done to find out operation time
Calculations of machine hours
required
18. A survey was carried out for about 50 odd
items and considerations from quality
departments taken to decide on the
rejection %
Group Rejection allowance
Automatics 2
Lathes 10
Hobbies 10
Milling 5
Allowances for Rejection
