Question 9: Where should the control limits be located on the control chart?
The best thing to do is to let the control limits follow the process automatically. It is a common myth that the operator then adjusts the process too often, but in practice the reverse is usually true: you adjust the process less often than when you are running it without SPC.
If the process is affected by fixed tools, on the other hand, letting the control limits follow the process may cause problems; in that case you can opt to lock the control limits at a given distance from the tolerance limits.
SPC in plain language explains very clearly how control limits work.
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? »