Process capability and control charts

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Discussion Overview

The discussion revolves around process capability and control charts in the context of manufacturing, specifically focusing on the production of screws. Participants explore the implications of process control, capability indices, and the effects of tool wear over time.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant notes that the process capability (Cp) is 1.013 and questions whether a process that is in control and just about capable can be assumed to be centered and not skewed.
  • Another participant raises questions about the manufacturing process of screws, specifically whether they are cast or cut with a die, and how this affects the tolerance of the screw diameter.
  • There are inquiries about what aspects of the process may be skewed and how this skew might change over the lifetime of the die used in production.
  • Some participants express uncertainty about the nature of the questions, suggesting that they may be more appropriate for a homework help context.
  • One participant mentions that after 30 hours of operation, the process will start producing products outside the lower control limit (LCL), prompting questions about the reasons behind this phenomenon.
  • There is a suggestion to consider how the initial dimensions of the die could be adjusted to maximize its lifetime, indicating a focus on practical implications of the discussed concepts.

Areas of Agreement / Disagreement

Participants express varying levels of expertise and understanding, with some questioning the nature of the original inquiry and others providing insights into the manufacturing process. The discussion remains unresolved regarding the specifics of the skew and the implications of tool wear.

Contextual Notes

Participants have not reached a consensus on the assumptions regarding process skewness or the effects of tool wear on production quality. The discussion includes multiple perspectives on the manufacturing process and its implications for process capability.

lee123456789
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<< 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
 
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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?
 
Also, this sounds like a schoolwork question. Should I move the thread to the Homework Help forums for you?
 
berkeman said:
Also, this sounds like a schoolwork question. Should I move the thread to the Homework Help forums for you?
ok thank you
 
Thanks. Thread moved to the schoolwork forums...
berkeman said:
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? :smile:
 
berkeman said:
Thanks. Thread moved to the schoolwork forums...

So can you comment on my questions? :smile:
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
 
lee123456789 said:
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?
 
lee123456789 said:
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? :smile:
 

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