Machine Capability vs. Process Capability - Differences?

[sunita]

Hi!

Can anyone enlighten me what is the difference between machine capability and process capability?

 

[JRKH]

Re: Difference between machine capability and Process capability

Hi!

Can anyone enlighten me what is the difference between machine capability and process capability?

Just briefly,:
Machine capability is a function of the machine's ability to repeat movement. This is a governed by such things as its design, wear, and condition.

Process capability is a function of the machine's capability modified by the additional variables of type of cutting tool, material being cut, method of work holding, speeds, feedrate, coolant used, etc.....

Hope this helps.

James

 

[sunita]

Re: Difference between machine capability and Process capability

Just briefly,:
Machine capability is a function of the machine's ability to repeat movement. This is a governed by such things as its design, wear, and condition.

Process capability is a function of the machine's capability modified by the additional variables of type of cutting tool, material being cut, method of work holding, speeds, feedrate, coolant used, etc.....

Hope this helps.

James

Hi! James,

Thanx. How to calculate machine capability? Any suggestions.

 

[TamTom]

Hello,

I have attached an excerpt from our internal procedure which is based on the AIAG SPC manual maybe it helps

Greetings

Tamara

 

[sunita]

Hi! TamTom,

Sorry i cannot open your attachment, i get error messages. Hope you can help.

Thanx

sunita

 

[TamTom]

Hi! TamTom,

Sorry i cannot open your attachment, i get error messages. Hope you can help.

Thanx

sunita

Hi,

in the documents are the formel editor used, maybe that cause the problem.
I will see I can change this.

Tamara

 

[TamTom]

Hi,

in the documents are the formel editor used, maybe that cause the problem.
I will see I can change this.

Tamara

Here are the formule for Machine capability:

Cm = USL – LSL / 6s
Cmk = min {CMU, CML}

where CMU = [USL - x¯ (x cross)] / 3s and
CML [x¯ (x cross)] – LSL] / 3s
where USL = upper specification limit
x cross = mean of measured values
LSL = lower specification limit
s= standard deviation of measured values.
Note: The method described applies to the normal distribution. If the distribution is not normal, other appropriate graphic or computer-aided methods shall be used.

Process Capability is not possible with the standard Ascii- Code, you need the windows formule editor.

Tamara

 

[sunita]

Hi! TamTom,

Your effort is much appreciated.

 

[quality.shesha]

process capability is the combined effect of every paramater as James(JRKH) said for which measurement system has also a part to play.

 

[Sushil Kumar]

process capability is the combined effect of every paramater as James(JRKH) said for which measurement system has also a part to play.

Machine capability is calculated on target value with individual sample standard deviation with unchanged conditions i.e. operator, material etc. While process capability is calculated on sample subgroup & individual both with average x bar. I am enclosing some litrature also hope it would be helpful to you.


Sushil