An SPC dimension is a specific dimension designated to be monitored for process control. Typically I use the DIN 16742 standard to establish the tolerance based on the size of the dimension. I am attempting to find more information on the process for establishing the tolerance size other than relying on the DIN standard. I hope this is not too ambiguous but I do not know how else to explain what I am trying to achieve.Sorry for being so dense but I don’t know what a “SPC dimension” is?
In general there are several ways to set tolerances on any characteristic. Some are good some are ‘meh’ and some are just dumb.
The tolerance should be based on what the thing is expected to do, and how that might fail if the size is wrong. There are risks involved, such as making the tolerance too loose or tight, but there are no tables that will help you to determine that. How do you know the dimension must be monitored for process control if you don't know the tolerance?An SPC dimension is a specific dimension designated to be monitored for process control. Typically I use the DIN 16742 standard to establish the tolerance based on the size of the dimension. I am attempting to find more information on the process for establishing the tolerance size other than relying on the DIN standard. I hope this is not too ambiguous but I do not know how else to explain what I am trying to achieve.
I am the dimensional engineer and I determine which dimensions are to be used as SPC. They do not necessarily need to be functional dimensions, as I am choosing them for process control only. Functional dimensions are typically toleranced much too tightly to ever achieve a 1.67 Cpk.The tolerance should be based on what the thing is expected to do, and how that might fail if the size is wrong. There are risks involved, such as making the tolerance too loose or tight, but there are no tables that will help you to determine that. How do you know the dimension must be monitored for process control if you don't know the tolerance?