time delays

8/3/2019 Time Delays

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EngineeringEngineeringEngineering --- TeamTeamTeam

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Time delays inautomatic GT

loader-Curingsection (AKM).

By

Keerthi Kumar H.M

52 BTTP Nov2011

Industrial Engineer - Medak


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Assignment snap shot

Section name - Curing Section

Tyre type - Considered only Radial tyres.

Machine - Automatic GT loaders.

Objective of the assignment :

To reduce the time differences found inautomatic loaders to the level of ideal

time found in same group.


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Scope of the assignment: By collecting data regarding timings observed for automatic

loader operation, we can compare the differences found in each

mould with respect to ideal time to complete that process.

With this data collection, we can make a priority analysis to

reduce the excessive time consuming in set of moulds.

As curing time is constant, only way to increase curing

production is by reducing the excessive time found in GT

loader operation.

As the short delays are repeating in each cycle of operation,there is a much scope to reduce large loss in longer run.

By reducing the time difference, we can increase the tyre curing

capacity of existing moulds.

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ABS

TRAC

T: The assignment was based on conducting the time study on variousmoulds for loading/unloading operation of automatic GT (green tyre)loader. When we compiled this data its found that each automaticloader is taking different time to do the same operation in similar tyretype.

In this assignment considered 50 mouls(100 cavities) which areproducing radial tyre curing for our study purpose. Out of 50 mouldscategorized the moulds which are producing same type of tyres intoone group. The minimal time found in each group had beenconsidered as ideal time/ Bench mark time for reducing excessivetime found in other moulds due to various reasons.

From the differences found in each mould, we have analyzed themost probable reasons for the existence of these delays.


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The process: Green tyre will be loaded on the GT stand with alignment with

side walls joining point.

Switch on the auto pick up button of loader. So that it will pickthe tyre by hydraulically operated one way cylinderarrangement.

The collapse/Expand action of the loader will be controlled bypneumatic cylinder.

The GT will be loaded into the lower bladder ring byhydraulically controlled (cold water with pressure of 250 PSI)two way cylinder for IN/OUT movement.

Same Sequence will be repeated during bringing back theloader to original position.

The sensors had been provided to receive the signals forbottom & top position reached during both loading &unloading cycle.

The entire automatic loading system will be controlled by

instrument air with pressure of40 PSI.


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Methodology Followed:

With the help of stop watch study, captured the

loading/unloading time observed in each mould.

Considered 04 readings in each mould for arriving at

average time.

Captured the data in prescribed format which is covering

all the required data.

The attached excel sheet will indicate the different data's

had been collected for fulfilling the purpose.

Total time required for automatic loading of GT loader

had been arrived by considering summation of mould

open time, loading/unloading time & mould closing time.


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D

ataC

ollection: In the similar type of tyre curing moulds, we have

compared the differences by considering minimal time

found in same group as a benchmark.

The time delays had been projected to one year to get theimportance of the minimal delays in repetitive manner.

Formula used are,

1.No. of cycles per day= available time / (curing time+ideal

time for L/UL)

2. Total time delay per year = Individual time loss * No. of

cycles per day * 365.

3. Projected production loss per/year = Total time delay /

(curing time+ideal L/UL time).


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D

ata Interpretation:

Comparison of loader timings v/s

different moulds-140/60 R17 REVZ.

107100

73

8993 95

75

0

20

40

60

80

100

120

161/162163/164171/172187/188189/190195/196199/200

Total time (sec)

Ideal time - 73 sec


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Calculation:

Max. % of deviation in time delay:

Example taken in case of 140/60 R17 REVZ

Max. time found in mould # 161/162 106 sec

Min.time found in mould # 171/172 -73 sec

= (Max. time - Min. time)/Min. time * 100

= 106-73/73 * 100

Max. % of time delay = 45.20 %.


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Comparison of Diff. in time WRT

minimal time found in mould #

171/172.(140/60 R17 REVZ)

34

28

0

16

2123

3

-5

0

5

10

15

20

25

30

35

40

161/162163/164171/172187/188189/190195/196199/200

Diff. in time WRT Ideal time.


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161/162

163/164

171/172

187/188

189/190

195/196

199/200

972

791

0

467

591

648

76

-200 0 200 400 600 800 1000

161/162

163/164

171/172

187/188

189/190

195/196

199/200

Projected Mouldwise loss of Tyre

curing production/year. (140/60 R17REVZ)

Projected loss of Tyre curing

production/year.


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Observations:

The difference in automatic loading timings are due tocombination of following reasons:

Drop in hydraulic pressure due to air leakages found in smallerpipes. (leakage may be due to small hole in the pipe or

improper joints). Due to hardness of water, scaling will be developed inside the

pipes after used it for quite longer days. These scaling (sulphuroxide) will black the valve, hence by reducing the water flowrate.

Whenever cylinder had been replaced with newer one, pistonmovement will be slower WRT to older cylinder in other sideof the arm. (due to restricted movement of piston disc).


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Continued.. The Cylinder piston disc might have damaged slightly /wear out , it will be affected in cross passing of pressure

so that reducing the final output pressure exerted on the

cylinder.

Drop in instrument air pressure(40 PSI) due to leakage

problem will also result in insufficient/partial opening of

valve gate.

Sometimes, water inlet valve will be partially closed

during operators handle it manually. No visual proof foridentifying the correct position of hand valve at fully

open condition.


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Continued..

Due to any one of these reason/ combination of reasons,

water pressure will be different at both the sides of the arm

(left & right), as we are having common return valve, thecylinder which is having higher pressure will move fast

thru the common return valve by restricting movement of

water from other cylinder.

During returning of cold water, it may contain with any

minute foreign particle which will obstruct in outlet valve.

This may also affect out flow rate of water hence by

delaying downward movement. ( Strainer is provided for

inlet pipe to filter foreign material).


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CO

NCLUS

IO

N: Whenever considering practical difficulties, itshighly cost effective to completely avoid these

variations. But by attacking on the most probable

reasons by preventive maintenance can solve theproblem to acceptable level / within the

tolerance.


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LIM

ITATIONS:

Due to non availability of sufficient time, only 3 major

groups of similar types tyre had been considered for

analysis.

Also no. of readings taken in each mould to arrive at

average time is not sufficient so that final time may not

accurate enough.

Although we have found out various causes & its effect

on GT loader performance, but we are not able to find out

root cause in each loader. (Because it needs furthermouldwise breakdown of analysis)


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Thank You.

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time delays

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