Application of Six Sigma to reduce an engine overheating problem$$

Anthony, Kumar and Tiwari $-$control phase. The real challenge of Six Sigma methodology is not in

making improvements to the process but in sustaining the optimized results. This requires standardization and constant monitoring and control of the

optimized process. An extensive training program

for the process$-$related personnel was conducted

within the company where the case study was performed. It is well known that real improvement will only come from the shop floor. Process sheets and

control charts were made so that the operator could

take preventive action before the critical process

parameters and critical performance characteristics

went outside the control limits$.$ A complete database

was prepared to sustain the improved result. Proper

monitoring of the process helped to detect and

correct out$-$of$-$control signals before they resulted in

customer dissatisfaction. Normal silica or chromite

sand was mixed with shell sand of AFS number $70$

$75$ to achieve better results. Zircon mixed with

magnetite was used as a wash substitute to increase

the refractoriness of the wash. Implementation of

the aforementioned suggestions resulted in further

improvements in process capability and process

yield.

Run charts for the depth of the porous core were

constructed $($Figs $8$ and $9)$ before and after improvements were made to the process. The purpose of the run charts here was to analyse variability in the

porous core around its mean value. Figure $9($after

the improvement phase$)$ shows that all the points

are within the specifications and that variability in

the porous core had been reduced significantly. $1.$ List Steps for this phase $2.$What was involved, why done, how done? $3.$Observations, Facts, Conclusion, Data, Results