• @Mike-Carnell We’ve already decided that the machine is not completely capable of holding our standards, that is why we are looking to lower our standard. Our issue is how much to lower it. 12 months ago

  • @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]