Question 10: What capability index should we have as a minimum requirement?
It is much more important to get started on process control than to get bogged down in discussions of what the right capability indices are. When you start using statistical process control, the operators acquire a shared way of looking at the process, and in many cases that results in an adequate quality improvement.
The most usual minimum requirement is Cpk 1.33.
Question 11: We produce short runs. Is SPC any use to us?
Probably. With short runs it is not so easy to reap the long-term benefits of SPC, but if you adopt it you centre the process right from the start and can hopefully safeguard the quality of the whole short run.
If the software allows, you can add in the next short run and thereby discern trends over a longer period, even though the individual runs are short.
Faq´s about SPC
1. Why should we use SPC in my company? »
2. Where should we start using SPC in our operations? »
3. What can we achieve with SPC? »
4. Can we start to introduce SPC without any preparation? »
5. What is MSA? »
6. What should we think about before starting to use SPC? »
7. What software should we use? »
8. What is the difference between producing with and without SPC? »
9. Where should the control limits be located on the control chart? »
10. What capability index should we have as a minimum requirement? »
11. We produce short runs. Is SPC any use to us? »
12. At what intervals should we measure the sample groups? »