How do to select USL and LSL limits?

For example,

I have observation results of 30 Re is 3.43, 3.27 ,3.19, 3.17,3.17, 3.19, 3.19, 3.24, 3.1, 3.12 ,3.25, 3.2, 3.35, 3.2, 3.2, 3.22, 3.23, 3.18, 3.19, 3.31, 3.18, 3.08, 3.18, 3.17, 3.23, 3.19, 3.25, 3.26, 3.23, 3.18

mean = 3.2117, STD = 0.07

Company datasheet provided for Re is 3.08 and production tolerances +/- is 7.50%

——–

to find Cpk how do I calculate USL and LSL values?]]>

We are trying to validate that the test works as designed.

30 (No Good) pieces were ran..and the data collected (the "measurements from the LVDT)

I was not part of the test..just given the data and ask to provide a statistical study showing the equipment did what it was supposed to do (i did..it rejected all 30 parts..but someone was some stats to back it up)

What...

What method to validate?]]>

Thanks for the advice.]]>

My mind has went blank when trying to work this out and was hoping someone could help me

We are judged by our main customer using our PPM score - that's the easy bit.

The bit i am confused about is that we supply them 3 separate product ranges, all of them have different PPM targets.

There is also a total PPM target - how would i work out my total PPM target based on the 3 different sub-targets.

Would it be a...

Parts per Million (PPM)]]>

2. Regarding collecting data for SPC from the specific process, I have another question.

What is the best sampling frequency for collecting data for conducting SPC.

Generally we apply rule: 5 pieces per each hour of manufacturing, overall 25 hours = 125 pcs.

Is it a must, or other rules can...

Capability for one sided specification]]>

Capability Calculations for Unilateral Specifications]]>

i want to know about relation between "relation between process capability index and tolerance".

what i mean to say is PC index=1, if we use 100% tolerance.

kedar]]>

The relationship between normal tolerance intervals (k factors) and process capability index (Ppk) is as follows: k = 3 x Ppk or Ppk = k/3.

In my work I have to assess process validation documentation and recently I have seen this statement in use from a number of external suppliers. My google fu has failed me on finding a source, none of the suppliers can provide one ( SOP's were written...

Tolerance interval and Ppk]]>

Thank you.

George]]>

QS9000 recommend Ppk >1.33 and Cpk >1.67 whereas

VDA 6.3 require Ppk >/=1.67 and Cpk >/=1.33.

In my opinion, I tend to agree with QS9000 since the Cpk usually

greater than Ppk. I do not understand how VDA 6.3 determined such target.

This is from QS9000

View attachment 187

This is from VDA 6.3

View attachment 188]]>

Cm & Cmk]]>

Cpk calculation for ongoing production.

With the same set of data, the Ppk calculation shows about 1.5 whereas Cpk calculation shows more than 2.00.

Since the target is 1.67, using Ppk will never meet such target and customer keep asking for the improvement while I have no more idea to improve further.

Please advise if any reason that I can convince customer to use Cpk calculation...

Ppk VS Cpk]]>

Customer is looking for a cpk on a measurement for positional tolerance of a hole.

The problem I have with this is the nominal measurement is 0 and tolerance is 0.25 but it's a position tolerance, it's not +/- 0.25 (I can't measure negative position).

Does anyone know how to make this or should I make 2 cpk's, one for each axis?

Reports come from a CMM and if I have to make two I would like to know if anyone knows the formula for calculating the tolerance for each axis. Example (Y...

CPK for positional tolerance]]>

Kedar]]>