What Questions Do You Need to Ask to Find Out Why a Process Is Out of Control?

It is easy to ask, “Why is my process out of control?” Here are a few questions to help you discover why your process is out of control.
1. Are your measurement tools and processes calibrated? Are the calibrations themselves verified regularly?
2. Is the process variability related to specific people, work groups, sites or shifts? If you do not know, how could you determine this?
3. Have the specification limits changed? For example, did the average change or the standards get tighter?
4. Have the standards you must meet changed?
5. Has your QC department changed? Do you have new inspectors? Did they get new inspection equipment? Has the visual inspection equipment had a software upgrade?
6. Has there been a software change on any piece of production equipment? For example, has the software, be it control software or operating system patches, been changed or upgraded on the CNC machine?
7. Is something in the process wearing out? Has the necessary maintenance been performed? Conversely, has anything significant been repaired or replaced recently?
8. Has throughput increased recently? After all, quality may drop if people are struggling to complete items coming off the line.
9. Has the sampling policy changed?
10. Is it possible that the problem has been evolving over time and just now become noticeable? Have minor corrective actions been taking place on the line?
11. Have your suppliers or subcontractors changed their processes, product designs or materials?
12. Has the inventory of raw materials aged or started to deteriorate?
13. Has there been a threat of strike or worker discontent that could be related to poor quality?
14. Is your quality circle still in session? If so, what have they done recently?
15. Has your environment changed? Has humidity risen? Have you installed or removed air filters? Has the temperature in the building been allowed to fluctuate with the day-night cycle to save on electricity, affecting the equipment or materials inside?
16. Are items from the repair shop and depot returns making their way into the production line?
17. Who just did a six sigma project or lean manufacturing project in our area?