A case study on machine utilization at

krishan and coWork sampling case study

ByChetan Patil

Introduction

Product manufactured ◦ Speedometers

◦ Pressure gauges

◦ Temperature indicators

◦ Tachographs

◦ Cables

◦ Warning lamps

Manufacturing facility

Machine room◦ Lathes

Semi automatic

Manual

◦ Gear hobbing machine

◦ Milling machines

Assembly room

Testing bay

Current problems

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

The consultants report based on work sampling study

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

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

Machine grouping

Group Machine type No of machines

1 Automates 10

2 Lathes 13

3 Hobbing 6

4 Milling 3

5 Drilling 9

Obtaining random numbers

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

Pilot study

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%

Total observations for each group

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

Summery of the results of study

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

Results and discussion

01020304050607080

working

operator

material

tool

breakdown

machine open

others

Poor machine utilization for all machines except automates

Contribution to total time

working52%operator

34%

material3%

tool1%

breakdwon6%

machine open2%

others2%

contribution to total time

Discussions

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

Machine time available

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, Interference, etc.

5 6 8 5

Breakdowns 5 8 5 1

Waiting for tools 1 2 2 2

Waiting for material 0 2 0 2

Total 16 22 20 15

Calculations of machine hours required

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

Allowances for Rejection

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

Machine hours required for production plan

Product 1 2 3 4

Speedometer 12600 13400 19000 0

Pressure gauges 5200 19300 0 3700

Temp gauges 0 10000 0 100

Tachographs 3100 3000 2700 440

Fare meters 30 300 53 0

Cables 19800 2100 0 3900

Hub wires 765 200 500 250

Warning lamps 1240 440 0 420

Total 42735 48740 22253 9710

Capacity expansion

S.N. 1 2 3 4

1 Net hours/ year 37800 45630 21600 11500

2 Total required 42735 48740 22253 9710

3 Additional 4900 3300 653 -1800

4 OT/week/machine 10 5 3 0

5 M/c hours for 2 months inventory

7094 7974 3028 1596

6 Total (3+5) 11994 11274 3681 -204

7 hours/machine/year 3780 3510 3600 3825

8 Additional machines (6/7) 3 3 1 Nil