MTBF to DPPM Calculation Based on the Unit's Typical Working Hours

[ravivangara]

Hello Elsmar Forum Members Greetings,
Can any one help me to explain how to calculate the details as explained in the enclosed file. Based on the MTBF data and the actual working hours of the unit, the slide has calculated the probability of return of goods from the market.
Thanx

[Michael Walmsley]

DPPM = Defects per Million Miles?????

[Tim Folkerts]

The probabilty a part is still working is simply e^{-(run time)/MTTF}.

In the example given, the part is used (300 hr/month)*(12 months)=3600 hr. Plug in the numbers and you will get the results they have.

Tim F

[Al Rosen]

Originally Posted by Michael Walmsley

DPPM = Defects per Million Miles?????

Defective Parts Per Million

[Michael Walmsley]

Thanks Al! Cant seem to keep up with all the acronyms.

ravivangara :
Your DPPM's will be Failure % X 1000000.

eg
513000 DPPM
302000 DPPM
165000 DPPM
86700 DPPM

[Al Rosen]

Originally Posted by Michael Walmsley

Thanks Al! Cant seem to keep up with all the acronyms.

ravivangara :
Your DPPM's will be Failure % X 1000000.

eg
513000 DPPM
302000 DPPM
165000 DPPM
86700 DPPM

I thought it was % * 10,000

% = (No Defective/Total no of parts)*100

DPPM = (No Defective/Total no of parts)*1,000,000

[Michael Walmsley]

Al,
You are sort of thinking six sigma.

Defects per million opportunities = DPMO = ((Number of defects / Total # units) * 1,000,000) / ( # of Opportunities for error on one unit).

Here ,
he has been given MTBF = 5000 hours.
"Note that at 5,000 hours MTBF, over half of the units can be expected to fail in the one year period."

Which means that if 1,000,000 units were produced per year that 51.3% would be defective or you would have a rate (DPPM) of 513,000 .

[Al Rosen]

Main point:

To go from % to per million mutiply % by 10,000.