The measure phase

This phase is concerned with selecting one or more

product characteristics, mapping the respective

process, making the necessary measurements,

recording the results on process control cards, and

establishing a baseline of the process capability or

process performance. Process mapping provides a

picture of the steps needed to create the output or

process Y$.$ It is a pictorial representation of the

process, which helps to identify all value$-$ and nonvalue$-$added steps, key process inputs $($X$)$ and outputs $($Y$).$ Figure $2$ shows the process mapping of the

casting process of the engine cylinder head. There

are three core processes: sand preparation, core

preparation, and wash preparation and coating.

Having mapped the process, the team proceeded to

analyse the potential causes of defects. Although this

task is carried out in detail during the Analyse phase

of the Six Sigma methodology, the team had to plan

how well the X inputs are controlled in the given

process. Figure $3$ illustrates the cause and effectanalysis for the water$-$jacket$-$passage jamming problem. The $$effect$$ in this example is the porous core.

The output of the cause and effect diagram depends

to a large extent on the quality and creativity of the

brainstorming sessionThe cause and effect analysis showed that the

process variables affecting the porous core were

sand leakage, blow pressure, the AFS number of the

sand, the gap in the core box, bulk density of thethe team members that the contribution of the

porous core to water$-$jacket$-$passage jamming was

over $80$ per cent. Having constructed the cause and

effect diagram, the team then created a cause and

effect matrix. Table $1$ is a cause and effect matrix

showing the customers$$ needs and the relative importance of the process characteristics that are critical to

customers.

The next step was to define performance standards

according to the customer requirements. The goal of

these performance standards was to translate customer needs into measurable characteristics. Based

on the specification limits$,$ performance standards

for each process parameter were established $($see

Table $2).$ Having established the key process parameters and the critical$-$to$-$quality characteristic $($depth

of porous core$),$ it was essential to establish the

accuracy of the measurement system and the quality

of the data. A data collection plan was established to

focus on the project output and also to carry out the

standard$-$setting exercise for the same. A Gauge

repeatability and reproducibility $($R&R$)$ study was

conducted to identify the sources of variation in the

measurement system and to determine whether the

measurement system was capable or not. It may be

necessary to redesign the gauge and perform proper

maintenance of instruments when repeatability is

large compared with reproducibility. When reproducibility is large compared with repeatability, then

the operator needs to be better trained in how to

use and read the gauge instrument; a suitable fixture

was needed to help the operators use the gauge more

consistently. The measurement system was considered acceptable when the measurement systemvariability was less than $10$ per cent of total process

variability $[21].$ However, the system may be acceptable when the measurement system variability is

between $10$ and $30$ per cent; at above $30$ per cent

variability, the measurement system was not considered acceptable. This study is performed in order to

check the accuracy of the gauges used for the

measurement of characteristics, as well as to check

the accuracy of the workers operating the machine.

The Gauge R&R study performed on the system

showed variation of $6\mathrm{.}08$ per cent, which implies

that the measurement system is acceptable. Table $3$

illustrates the results of the Gauge R&R study carried

out during the Measure phase of the project.

The baseline process capability $$Cpk$$ was also

established in this phase. The Cpk value based on

the existing process conditions is estimated to be

$0\mathrm{.}49.$ This clearly indicates that process performance

is poor and clearly needs improvement.

sand, and vent choking. It was also observed by