M
All,
I am doing a capability study on a new machining process and have run into some issues. I'll start with a little background info:
- the process is thinning plastic sheets (19"x19") to a targeted thickness = 0.035"
- we take thickness measurements at each corner and halfway between the corners, resulting in 8 measurements per sheet.
- when subgrouping, I use a subgroup size of 8 because this would represent one sheet. Is this OK?
- I have data on 43 sheets.
- Issue one: controll chart (X-bar) indicates the process is out of control.
- Issue two: non-normal distribution.
- I am using Minitab for analysis.
I plan to investigate the process further to see what is causing the issues mentioned but I did run Cpk just to see what I would get. I was surprised that it was ~1.5. I don't think a process can be out of control and be capible at the same time, correct? Am I going about the capibility study the right way? Should I be doing something different?
Thanks.
I am doing a capability study on a new machining process and have run into some issues. I'll start with a little background info:
- the process is thinning plastic sheets (19"x19") to a targeted thickness = 0.035"
- we take thickness measurements at each corner and halfway between the corners, resulting in 8 measurements per sheet.
- when subgrouping, I use a subgroup size of 8 because this would represent one sheet. Is this OK?
- I have data on 43 sheets.
- Issue one: controll chart (X-bar) indicates the process is out of control.
- Issue two: non-normal distribution.
- I am using Minitab for analysis.
I plan to investigate the process further to see what is causing the issues mentioned but I did run Cpk just to see what I would get. I was surprised that it was ~1.5. I don't think a process can be out of control and be capible at the same time, correct? Am I going about the capibility study the right way? Should I be doing something different?
Thanks.