Cannot agree more,
We look at ICT as a tool to help CM's trouble shoot assemblies, prior to functional testing. We only measure/monitor the CM's FPY at the functional test systems and ask they provide and monitor their internal FPY information at ICT and AOI. CM's only need to report their FPY information when there is a >= 10% change in FPY's or >4 data points showing a trend. Again we strive to have 100% "testable" nodal coverage at ICT and use the DFMEA to determine overlapping functional testing and coverage for circuits that may have been missed (couldn’t be tested or confirmed) during ICT and or AOI. Our goal, after AOI, ICT, boundary scan and functional, is to have a minim of 98% test coverage when each system is used in conjunction with one another. Anything with a high RPN may have redundant tests to help reduce the RPN. Any CTQ's (Critical to Quality) identified are flagged and require SPC monitoring.
One key take away regarding FMEA's is that they are living documents. All too often I hear or see the FEMA being completed and not updated. Each time an 8D or A3 is generated the FMEA needs to be evaluated and perhaps updated. A FMEA (DFMEA and PFMEA) review should be standard when reviewing a corrective action to insure your original assumptions were correct and if necessary, adjust the RPN's, rethink the problem and or solution. Let's face it, the first stab at any new FMEA is a best guess so you should expect it needs updating.
Ted T.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Blair Hogg
Sent: Monday, May 13, 2013 7:36 AM
To: [log in to unmask]
Subject: Re: [TN] ICT Coverage
I've read all the excellent comments on this thread and although not all are in agreement I think good points are being made.
If you wan tto do it right, use the FMEA tools to determine the testing needs. Your FMEA score will let you know what your likelihood of shipping bad product is, and will help you look at ways to minimize it.
The FMEA process runs somthing like this:
Identify all possible failures modes, their effects and the severity of the effect, and the likelihood that it will occur.
-> This gets to be a really big task, especially on assemblies with many components, as there are mulitple failures modes for each component, e..g missing, wrong component type, wrong value, out of tolerance, etc.
Sort the list with those with largest severity, highest likelihood on top, then identify methods to mitigate the failure mode, e.g. test and repair, process change, visual inspection, AOI, etc.
Continue until your overall FMEA score is low enough such that the risk of shipping bad product is minimal.
ICT will not detect every failure as was already mentioned. A combination of ICT, AOI, functional testing, etc. will be needed to reduce the risk of shipping defective product to an acceptable level.
Blair
On Thu, 9 May 2013 19:25:28 +0000, Furrow, Robert <[log in to unmask]> wrote:
>Hi all,
>
>I know the goal is "as much as possible", but what is a reasonable expectation for % coverage during ICT for Class 2 products?
>
>Thanks,
>Bob Furrow
>Quality Assurance Engineer
>Honeywell Aerospace - Sarasota
>941-360-6285
>[log in to unmask]
>
>
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