CpK on a manufactured assembly?

FloridaST

Involved In Discussions
#1
Greetings, I'm new to the QA world and a customer is requesting a CpK on a manufactured box build assembly as part of their PPAP. Now I'm familiar with doing a CpK on items with actual measurable upper and lower limits but I'm a bit unsure as to where to start with this request. Essentially we're placing a circuit board into an enclosure and then potting it. Any advice would be appreciated. Thanks!
 
Elsmar Forum Sponsor

FloridaST

Involved In Discussions
#3
Can you provide more details. What measurable output or characteristic is the customer asking you to calculate Cpk for?
The customer clarified and realized they asked for a CpK on the wrong thing.

Let me ask you this, who determines the measured characteristic when a CpK is requested? These aren't our products or designs, we simply build to specification. I'm not strong in this area so I really couldn't give much help to the customer.
 

Golfman25

Trusted Information Resource
#4
The customer clarified and realized they asked for a CpK on the wrong thing.

Let me ask you this, who determines the measured characteristic when a CpK is requested? These aren't our products or designs, we simply build to specification. I'm not strong in this area so I really couldn't give much help to the customer.
It should be based on your customer's needs.

If you get to pick, then pick the easy one. :)
 

ScottK

Not out of the crisis
Leader
Super Moderator
#5
Echoing Golfman… it's based on the customer needs - if you are building to their specification then they should specify which characteristics are critical to quality (CTQ) and require some sort of capability analysis.
 
N

ncwalker

#6
Customer needs is ONE aspect of it.

The purist answer is - you should do it on every measurable process you have. Who WOULDN'T want to know how capable they were on everything? More data means better data driven decisions, right?

Unfortunately, they cost to perform. AND some of your tolerances are really easy to hit. So you really want a strategy - let's do them on the things that count.

One of these is what your customer identifies as critical, as everyone has said. But there's a few more sources:

1) YOU may know some items are also critical. Your customer may not be the expert on your product.

2) There may be some features that are very difficult for whatever reason. They may not be critical, but they are still toleranced and just very tricky to make.

3) There may be some features that have little meaning to the part. They may not even be dimensioned or specified. But ... they may give you easy to measure metrics that the process is behaving.

So when you are deciding what to do a capability study, these are good things to think about. By no means do you have to do all of them, there should be some logic surrounding what you pick.
 
C

Chonchalerms

#7
You may start to do Cpk study of solder paste volume such as the thickness characteristic. it is the important thing and can effected to relative soldering defects.
 
#8
Echoing Golfman… it's based on the customer needs - if you are building to their specification then they should specify which characteristics are critical to quality (CTQ) and require some sort of capability analysis.
Usually there would be such legend in drawing callout or note to specify it as like significant characteristic or critical characteristic in automotive discipline for PPAP. Some customer should have like "customer specific requirement" as part of supplier manual to follow.
 
Thread starter Similar threads Forum Replies Date
D Ford CSR Cpk/Ppk Requirements Statistical Analysis Tools, Techniques and SPC 8
PQ Systems Cpk: Indispensible Index or Misleading Measure Using SQCpack Software 0
R Cpk demands from automotive customer Capability, Accuracy and Stability - Processes, Machines, etc. 8
Q Can I use Cpk to compare if one part is usable in another part? Capability, Accuracy and Stability - Processes, Machines, etc. 5
C Capability in sewing processes CP,CPk,PP,PPk Capability, Accuracy and Stability - Processes, Machines, etc. 10
G What's the difference between 1.32 and 1.33 Cpk? Capability, Accuracy and Stability - Processes, Machines, etc. 18
W LTPD, AQL, Ppk and Cpk validation sampling plan table Inspection, Prints (Drawings), Testing, Sampling and Related Topics 0
M Cp and Cpk for straightness and parallelism Capability, Accuracy and Stability - Processes, Machines, etc. 8
Q Capability - CPk comparison values Capability, Accuracy and Stability - Processes, Machines, etc. 12
D Tolerance definition based on expected Cp/cpk Reliability Analysis - Predictions, Testing and Standards 14
K Analysis variation among the lots during cpk calculation. Design and Development of Products and Processes 1
S Recommendation for user friendly Gaga R&R and Cpk software Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 10
A How to set up Continuous CpK monitoring of an injection mold process Reliability Analysis - Predictions, Testing and Standards 7
A Interpretation with regards to Ppk > Cpk Capability, Accuracy and Stability - Processes, Machines, etc. 14
U Cpk Calculation - I analyse a double seam cans Manufacturing and Related Processes 15
Proud Liberal Cp / Cpk on position using multiple MMC bonuses Capability, Accuracy and Stability - Processes, Machines, etc. 2
I Can we use pin gauges to measure an accurate Cpk ? Capability, Accuracy and Stability - Processes, Machines, etc. 9
T Final process capability results - What I am supposed to present? Cp and CpK? APQP and PPAP 11
M How is the Cmk and Cpk calculated? Statistical Analysis Tools, Techniques and SPC 0
O Cpk for Unilateral Tolerance Capability, Accuracy and Stability - Processes, Machines, etc. 9
B How to calculate CPK with n = 1 Manufacturing and Related Processes 2
O CPK with a P value less than 0.005 Manufacturing and Related Processes 8
A Short Term vs. Long Term SPC Study - Where is Cp and Cpk Defined Statistical Analysis Tools, Techniques and SPC 8
A Cpk Formula seems off, need help!? Capability, Accuracy and Stability - Processes, Machines, etc. 11
D Cp/Cpk on Gages for MSA (vs. Cg/Cgk) Capability, Accuracy and Stability - Processes, Machines, etc. 21
E Questions regarding Cpk Calculation - Should we be using LSL/USL or LCL/UCL? Capability, Accuracy and Stability - Processes, Machines, etc. 5
B Maximum Material Condition with Bonus - Determine Cpk for this one kpc Measurement Uncertainty (MU) 2
Hami812 Cpk Setting Tolerance - Cart before the Horse? (Wifi Routers) Capability, Accuracy and Stability - Processes, Machines, etc. 3
T Calculating LCL, UCL, Cp, and Cpk in an Excel Spreadsheet Statistical Analysis Tools, Techniques and SPC 3
Proud Liberal Cpk on Position w/ MMC on Location and Size Capability, Accuracy and Stability - Processes, Machines, etc. 3
E SPC Production - Getting Cpk and Ppk Statistical Analysis Tools, Techniques and SPC 8
S Track Cpk trend Statistical Analysis Tools, Techniques and SPC 5
M Cp & Cpk about a diameter measured with min.,max. and average values. Capability, Accuracy and Stability - Processes, Machines, etc. 13
P Non-normal Data Cpk Statistical Analysis Tools, Techniques and SPC 5
alonFAI Cpk for Solder Paste Height Statistical Analysis Tools, Techniques and SPC 5
I As a part of validation, should i include the acceptance criteria of CPk index >1.33? Qualification and Validation (including 21 CFR Part 11) 4
T Cpk for 0 as Ideal Value Statistical Analysis Tools, Techniques and SPC 1
P Profile Tolerance and CPK Manufacturing and Related Processes 3
V When to use Cp Cpk and Pp Ppk Capability, Accuracy and Stability - Processes, Machines, etc. 4
M Calculating Cpk when sample size equals to 1 Capability, Accuracy and Stability - Processes, Machines, etc. 12
S CpK in Minitab when 0.0 is the lower spec limit Statistical Analysis Tools, Techniques and SPC 7
I Best way to Chart an On-Going CPK Requirement Capability, Accuracy and Stability - Processes, Machines, etc. 4
U Cpk for Contaminant Mass - Washing Parts Capability, Accuracy and Stability - Processes, Machines, etc. 6
G Help with Cpk procedure Capability, Accuracy and Stability - Processes, Machines, etc. 3
J Calculation of σ within subgroups for Cpk in Minitab Using Minitab Software 1
S Value of Ppk or Cpk when targeting thinner material Statistical Analysis Tools, Techniques and SPC 4
B How to validate Microsoft Excel Spreadsheet Calculations for the Cpk value Capability, Accuracy and Stability - Processes, Machines, etc. 9
D Calculating Cpk on Non-Normal Data Distribution Capability, Accuracy and Stability - Processes, Machines, etc. 10
D Cpk relation to Reliability Capability, Accuracy and Stability - Processes, Machines, etc. 4
B Process Capability - Changing Limits to Improve Cpk or find Root Causes? Capability, Accuracy and Stability - Processes, Machines, etc. 8

Similar threads

Top Bottom