Top 6 limitations that you should know before deciding using Excel for Online SPC data collection and quality control.

1) No or ineffective authorization control

• Excel is a spreadsheet application; anybody can just alter any fields in the spreadsheet. Therefore, its difficult to prevent authorize user from changing data or other pre-set configuration such as subgroup, control limits, specs, chart color, format etc. Although there is ‘password’ field protection, but maintaining this is a tedious job for the end-user.
• There is no proper tracking on who has actually worked on the file and the data.

2) Risk of losing valuable configuration and data

• In Excel, all configuration and data is saved in a single file. It is really easy to accidentally corrupt the file due to ‘human error’, virus attack, vandalism or even ‘file copy’ error. Moreover, it is easier to corrupt excel files when as the size grows.
• Even backing up of files will not ensure data can be restored properly, because corrupted files can just be backup like any other files.

3. Difficult to scale as the SPC requirement grows

• Excel can fulfill occasional plotting of a few simple SPC charts. However, it will be too difficult to maintain a large number of charts using excel, because there is no simple ‘group’ configuration features to maintain each chart configuration at a central place. Now, what if customers or management request for changing of chart type or increase of subgroups or simple changing of line colors? Each excel files have to be updated because the configuration is set at each file.

4. Difficult to do cross section analyses

• Does these sounds easy if you use excel? - Total out-of-control for all Process in May, - Pareto of abnormality for all machines for a selected customer’s product, - - Cpk across weeks or months, - Ppk for product running at 3 machines. This is just some example of some occasion where you need cross section compilation of your data. You will need more man-hours to compile these data each time using excel.

5. Difficult to monitor SPC violation

• You can use Excel to highlight on values above UCL or LCL by setting some ‘pre-conditions’. However to get Excel to highlights on all the 7 nelson rules will be too just too difficult or almost impossible for general users. Therefore you will still need human to manually interpret the charts to detect the trends which are tedious, time consuming and mistake prone.
• The task of interpreting SPC chart is therefore difficult to pass down to the lower level.

6. Difficult to track actions and progress

• Excel is not able to automatically trigger email or alerts when there is Out-of-control.. It is also difficult to know who has taken action on the problem because there is no tracking of feedbacks on the activities at each stage of problem resolution process. Therefore the progress such as date, time, action histories, re-inspection history will not be clearly recorded.