Question

Dear Expert. I have been studying about Statistical Process Control. And my professor required me to collect the data from real manufacturing in Taiwan. I wonder how can I make a plan in Data collection for SPC. This manufacturing product ordered product ( house door, ventilator, window, etc...). The main raw material is steel. I had gone there last week and seen how it work. I already know what kind of machine and part I need to collect. But the problem is that I need the specific time to collect data like in 1 hour or 2 hours for 25 subgroups with 120 observations. Or I need to collect the data base on their week, like 5 parts per day in 25 days for 25 subgroups. My professor required me to make a timetable in precise time. Can you help me with this problem? Thank you, Master.

Answer 1

Answer :

Data Collection for the SPC for Subgroup category:

For SPC the data collection sampling plan should be such that it reflects the real manufacturing scenario so that we can carry out the SPC for the real operating conditions of the process.

For the subgroup category of SPC - The data collection should be

• Random data collection

• Data Collection at determined frequency.

• We need to capture the variation between the subgroups instead of within the subgroup.

Thus for the given SPC, the data collection should be as below

• 5 sample per day in the particular shift for the particular product and this we need to continue for 25 days.

• This will be able to provide the data collection for 25 subgroups where each subgroup will have 5 data sets.

• This approach will help in taking the random data for 25 days so that we can capture the variation between the groups instead of within the groups.

For Non subgroup SPC - For the non-subgroup SPC calculations, the data collection should be such that the normal process is operating and we need to collect the continuous 32 data samples for the SPC study. The continuous 32 sample of data will be sufficient to conduct the short term SPC for the process.