Shell Weight reduction in BH521 6 Cavity

Duration Sept‐2007  to Nov‐2007Project Leader – Abdullah Ansari

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Project Start date : 01/09/07Target Completion date : 15/11/07 Date of proj presentation : 20/11/07Throughput Project Open days : 75Sponsors reviewed proj  : YesNo of team meetings : 06

Savings : Current FY Rs. 2 L Annualized Rs. 6 L

Phase completed : D M A I CBelts % time on project : 40%Project review status : ( R / Y / G ) 

Sponsors                 MBB 

Define                 Measure  Analysis  Improve  Control

GGGGG

GGGGG

DEFINE

Define project objective, expected benefits to the organization, team members, project schedule.

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Objective:

Benefits:

ProjectTeam:

Schedule: Measurement: 20/09/07 Analyze: 10/10/07 Improvement:  10/11/07              Control:  15/11/07 

S J Chougule   (Prod Engg)Ashok Khanna S S Kulkarni     (Prod Engg)R K Choudhary                           Mahesh            (Proc Engg)

S N Soddy        (Quality)R K Jena           (Melting)

A T Ansari 

To increase number of BH521(6 Cavity) shells per MT of resin coated sand by reducing shell weight from 27 Kgs to 25 Kgs at molding while maintaining the minimum possible defectives due to shell making.

Savings: 52.5 K Rs per MonthImproved process cycle timeReduced operator fatigueEffective utilization of raw material

Revision 1

Shell Weight reduction in BH521 6 Cavity

MEASURE

Base Current Shell Weight – 26 to 27 Kgs CurrentCurrent Cycle Time – 257 Seconds per shell (14 shells per hour)Investment time – 85 Seconds

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6

50,000 ft Process Map

Inputs (Xs) Outputs (Ys)C/U/S

Resin Coated sand C No. of Shell per hourCycle Time C Shell weightHeated pattern U

C = Controllable

U = Uncontrollable

S = SOP

Shell Making

Shell Weight reduction in BH521 6 Cavity

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C & E Matrix

Rating of Importance to Customer

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Process Step Process Inputs No.

of S

hell

per h

our

She

ll w

eigh

t

Total

1 Shell Making Investment time 6 6 962 Shell Making Resin coated sand 0 6 483 Shell Making Preheat time 2 2 324 Shell Making Preheat temp 0 2 165 Shell Making Baking time 2 0 16

8

554943373125191371

28.5

28.0

27.5

27.0

26.5

26.0

25.5

Observation

Indi

vidu

al V

alue

_X=26.882

UCL=28.247

LCL=25.517

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I Chart of Shell Weight

‘I’ Chart for Shell Weight before improvement

ANALYZEWhich factor affecting on shell weight?

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10

Histogram of Shell Wt.

28.227.627.026.425.8

20

15

10

5

0

Shell Wt

Freq

uenc

y

Mean 26.88StDev 0.4979N 60

Histogram of Shell WtNormal

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Regression Analysis

180175170165160155

28.5

28.0

27.5

27.0

26.5

26.0

Pattern Temp

Shel

l Wei

ght

S 0.494345R-Sq 3.1%R-Sq(adj) 1.4%

Fitted Line PlotShell Weight = 24.35 + 0.01501 Pattern Temp

Pattern temperature is not the major factor resulting in increase or decrease of shell weight.Take trials by varying temperature and investment time and redo regression analysis. 

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Regression analysis – Fitted line plot for Inv time

8580757065

27.5

27.0

26.5

26.0

25.5

25.0

Investment time

Shel

l wei

ght

S 0.195085R-Sq 96.5%R-Sq(adj) 95.6%

Fitted Line PlotShell weight = 18.58 + 0.1025 Investment time

IMPROVE

To decide optimum process parameters to achieve required shell weight.

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DOE

RUN Pattern Temp x Investment T ime Plan / Status Actual Avg TempActual Avg Shell

Weight

Run 1 220 x 65 04.10.2007 220.8 25.14

Run 2 220 x 75 04.10.2007 220.9 26.21

Run 3 220 x 85 04.10.2007 220.9 27.08

Run 4 240 x 65 07.10.2007 240.8 25.04

Run 5 240 x 75 07.10.2007 240.2 26.13

Run 6 240 x 85 07.10.2007 238.8 26.63

Run 7 260 x 65 08.10.2007 260.1 25.36

Run 8 260 x 75 08.10.2007 262.6 27.09

Run 9 260 x 85 08.10.2007 261.4 28.04

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AB

B

A

20151050

Term

Standardized Effect

1.99

A Inv estment timeB Pattern Temprature

Factor Name

Pareto Chart of the Standardized Effects(response is Shell weight, Alpha = .05)

DOE Results

Investment time

Patt

ern

Tem

prat

ure

8580757065

260

250

240

230

220

210

> – – – – – – < 25.0

25.0 25.525.5 26.026.0 26.526.5 27.027.0 27.527.5 28.0

28.0

Shell weight

Contour Plot of Shell weight vs Pattern Temprature, Investment time

Investment time = 69.9450Pattern Temprature = 220.231Shell weight = 25.5168

Investment time = 65.0255Pattern Temprature = 240.176Shell weight = 25.2558

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Optimized Process controls for further full heat trials

• Investment time = 65 to 70 Seconds– Target 67/68 Seconds

• Pattern Temperature = 230 to 250 0C– Target 240 0C

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Results of full heat trials with new process parameters

332925211713951

26.4

26.2

26.0

25.8

25.6

25.4

25.2

25.0

Observation

Indi

vidu

al V

alue

_X=25.651

UCL=26.362

LCL=24.940

I Chart of Shell Wt

26.025.625.224.824.424.023.6

30

25

20

15

10

5

0

Shell WtFr

eque

ncy

Mean 25.00StDev 0.5079N 172

Histogram of Shell WtNormal

Data of 1stTrial

Data of shell weight 172 shells ~ 5 heats

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Any effect on Casting Rejection…?

• Before• Casting rejection 6%• Casting rejection due to swelling and shell crack – 1.5%

• After• Casting rejection in full heat trials 5%

• Casting rejection due to swelling and shell crack – 1%

No Negative Effect

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Improvement Summary

• Earlier shell weight 26.9Kgs (based on data collected on 18/09/2007), Now 25.5Kgs

• Saving of 1.4 Kg resin coated sand per shell• Earlier investment time 85/90 Seconds, Now 67 Seconds• Cycle time reduction by 18/23 Seconds per shell.• Forecasted saving

– Due to saving in resin coated sand• Rs 49000 per month• Rs 5.88 Lacs per annum

– Productivity improvement• 20 seconds x 14(shells per hour) = 280 Seconds ~ 1 shell per hour• Capacity enhancement of 3744nos of castings per month

CONTROLIntroduce Controls to sustain the improvement

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Control Plan

• Resin coated sand– Sand properties should be strictly within specifications at receiving 

inspection.– Build up should be 49% to 52%

• Investment time– Should be 65 to 70 Seconds. 67 is ideal. To be ensured while setup 

approval.• Pattern Temperature

– Target for 2400C – Measure by infrared gun while setup approval– Maintain temperature by keeping burners on/off for every 2 alternate 

shells, as temperature on machine can not be controlled automatically.  

Thank You