Process capability and control charts

[lee123456789]

<< Mentor Note -- Thread moved from the technical forums, so no Homework Template is shown >>

I was looking into process control and capability of general manufacturing company.
e.g one that constructs bolts

There process was was within tolerance and in control producing screws within tolerance, but will go out of control later on.
There process capability (Cp) = 1.013 was just about ok.

Im slightly confused on the skew of the data
If the process in control and just about capable can you assume the process is centred, not skewed

 

[berkeman]

I'm no expert on this, but if they are making screws, how to they make them? Do they cast them (how coarse are they?), or more likely they cut the threads with a die, right? How does a die work? What determines the tolerance of the diameter(s) of the screw cut by the die?

And after answering those questions, can you say a bit about what will be skewed, and how it will vary over the lifetime of the die?

 

[berkeman]

Also, this sounds like a schoolwork question. Should I move the thread to the Homework Help forums for you?

 

[lee123456789]

Also, this sounds like a schoolwork question. Should I move the thread to the Homework Help forums for you?

ok thank you

 

[berkeman]

Thanks. Thread moved to the schoolwork forums...

And after answering those questions, can you say a bit about what will be skewed, and how it will vary over the lifetime of the die?

So can you comment on my questions?

 

[lee123456789]

Thanks. Thread moved to the schoolwork forums...

So can you comment on my questions?

sorry I am not sure.
all i got is process cability number, and control charts from them it says the the process is incontrol and capabilile. but after 30 hours process will start producing products out side the LCL
a machine its made on. all i got on it

 

[berkeman]

but after 30 hours process will start producing products out side the LCL

And why would parts that are coming out of a die have that characteristic? Have you ever used a saw blade a lot until it got worn down and too dull to keep using?

 

[berkeman]

but after 30 hours process will start producing products out side the LCL

And once you figure out why this happens, what can you say about what you should do with the initial dimensions of the die to maximize its lifetime?