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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

Topic Posted by: Reliability & Maintainability Forum (src_forum@alionscience.com )
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998

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Original Message:

Posted by: Uma
Date posted: Fri Sep 30 15:40:47 US/Eastern 2005
Subject: Qualifying suppliers
Message:
Hi, Does anybody have an example of a supplier questionnaire that we can use to qualify the devices we are buying? For eg. questions like "what is the predicted reliability of the device?" "How was it derived?" "Has this been tested?" "How accurately does your field returns mimic this prediction"? "What is done to assure reliability during the design process? etc etc Is there a standard that can be used? Thanks for your help in advance.


Reply:

Subject: Supplier reliability FDL RITA
Reply Posted by: Larry George (pstlarry@yahoo.com )
Organization: Problem Solving Tools
Date Posted: Sat Oct 1 14:24:49 US/Eastern 2005
Message:
I have used the following letter with some success (See http://www.fieldreliability.com/Nwslt2.doc for more info.): Dear Vendor: Congratulations on being considered to include your parts in our products. Final vendor selection depends on the availability of your field reliability data. Your data helps us choose vendors on the bases of profit and customers’ life cycle costs, because profit and life cycle cost depend on your parts’ field reliabilities. Your field reliabilities help us: • diagnose process and design defects • recommend the diagnostic sequence that minimizes time to find problems • estimate warranty returns and set warranty reserves • provide early warnings and estimate sizes of problems • forecast service manpower, tools and spares requirements • set spares stock levels and reorder points • recognize product retirement before we get stuck with obsolete spares Please understand. We don’t choose vendors solely on the basis of their parts’ field reliabilities. We eliminate vendors who don’t share their field reliability data. Better the devil we know than the devil we don’t. Our managers want to manage randomness. They know they can’t have certainty and they prefer randomness to uncertainty. Your field reliabilities allow our managers to convert uncertainty into randomness. To estimate field reliability, we need any of these kinds of field data, in order of preference, on all your products not just a sample, by individual product or grouped by operating or calendar hour, day, month, cycle, quarter or year: • times-to-failures (replacements, returns, ships of spares) and installed base data • ships and returns (failures, replacements or ships of spares) data • ships and warranty returns (failures, replacements or ships of spares) data If you don’t have field data, laboratory test data will help. If you don’t have data on the product you’re selling us, field data on products with comparable reliability will help. From this data we will estimate your parts’ age-specific field reliability and failure rate functions and test hypotheses regarding improvements. We will share these results and their interpretations with you only, not with your competitors. Email your data to Larry George, pstlarry@yahoo.com (internet). Please include your voice phone number because Larry will ask a few questions about spares accounting, sell-through time, and repair or replacement effects. Larry will make nonparametric estimates of your products' field MTBF, reliabiity, and failure rate functions and send the estimates back to you along with diagnostics, free of charge. Thank you very much. FDL RITA stands for Falling Down Laughing Rolling In the Aisles


Reply:

Subject: FDL RITA
Reply Posted by: Larry George (pstlarry@yahoo.com )
Organization: Problem Solving Tools
Date Posted: Sun Oct 2 14:02:58 US/Eastern 2005
Message:
Sorry about FDL RITA. Supplier responses to my requests for field reliability info. ranged from: 0. "Our product is reliable." 1. "The MTBF prediction is X,000,000 hours." 2. "We tested 20 units at X00 degrees, and none failed." 3. "We don't track units by serial number, so we can't estimate field reliability." [WRONG] 4. "We would love to share our our field data with you, but let me talk with our lawyers first." If you would like to read more, check http://www.fieldreliability.com/Virtrel.htm and http://www.fieldreliability.com/ExcuLite.htm. The letter request in my previous reply results in constructive, successful sharing of field reliability information, both for vendors and for the companies I have worked for. Vendors learn their parts' reliabilities in our products, and we learn their parts' reliabilities in other products.


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