@Mike-Carnell We have our operators run SPC checks at set intervals. If they are below 1.66/1.33 then they need to take some form of action to correct the issue. The problem though, is that if a machine that can only run within .001 is running a part w/ a tolerance of +/- .001, our Cp/Cpk are going to be inherently low.
Currently, we are having…[Read more]
Say we are trying to hold a tolerance that is 1.000-1.010. We want to maintain a Cpk of 1.33 or higher and a Cp of 1.66 or higher on that spec. If we drop below that on either one, then we will start to fix possible issues w/ the machines/processes. That’s what I mean by a Cp/Cpk standard. 12 months ago
At my shop, we run SPC on every part fairly religiously, holding our parts to a 1.66/1.33 Cp/Cpk standard. We find a major issue, however when we try to run parts with say a +/-.00045 tolerance on a machine that is designed to hold within .0003. As the parts run on this machine, they get a natural spread and their Cp/Cpk values are thrown way…[Read more]