# What should the FMEA Occurence Rating be based upon?

A

#### Andrews

Sub : Occurence rating
Should occurrence rating be based on the no. of times a failure occurs or no. of non-conforming parts i.e if a particular undersize problem had occurred twice when running a batch of 10,000 components and if on segregation we found 2000 components non-conforming then should we take the failure rate as 2/10,000 thereby assigning occurrence rating of 5 or should we take the failure rate as 2000/10000 ,thereby getting an occurrence rating of 10.Likewise an undersize problem could have occurred 10 times when running 10000 nos. but on segregation found only 100 pieces.In this case should the failure rate be taken as 10 / 10000 i.e occurrence rating of 7 or take failure rate as 100/10000 nos. i.e occurrence rating of 10.

A

#### Atul Khandekar

Ten

Andrews,

Is it 2 out of 10000 or 2 out of some sample size? In any case I think you should take the maximum number that you found (in this case after segregation) to decide the occurence rating. You would get an occurence rating of 10.

Occurence must always be seen in conjunction with detection. Segregation or 100% inspection would be an inefficient and expensive method of detection. If you are doing sampling or SPC, you should be able to get a close enough estimate (PPM) of non-conforming.
-Atul.

R

#### Randy Benedict

Atlu,

Occurance happans before detection, therefore detection can't be assumed when rating occurance?

The detection may be the best in the world, but it only detects what has already occurred.

To reduce an occurance rating don't we need to implement improvement on the front end as opposed to the rear end (detection?)

D

#### db

What do you want to solve?

Andrews, I think you are mixing data (if I understand you properly). Here is the data as I see it:

10000 components
2000 nonconforming parts

2 process deviations (which lead to the 2000 n/c parts)
? possible process deviations

If you use the 10000 components, then your comparison must also be in components. If you are going to compare the number of process deviations, then you must have something to compare it with, for example the number of possible deviations. Let me explain.

Let’s say you produced 10 million parts. You had one process deviation that resulted in 100% of the parts being rejected. Would you say you had 1 deviation in 10 million parts? Probably not, it just would not make sense.

If your FMEA is looking for the number of possible deviations, then use the 2 versus what ever the number of runs.

One last thing. Normally, FMEAs are developed prior to the manufacture. The historical data can then be used to test the validity of the FMEA

U

#### Udawantsaraf

Quality Assurance Supervisor

I would like to know details about
ISO 9000 , 90001, 9002, 9003, 90004 and 9005
Is that depends on type of industries ? If yes let me know which standards are using for which type of industies.

Narhari

S

#### Sam

Andrews,

"Occurrence is the likelihood that a specific cause /mechanismof failure will occur".

The fact that that you had two failures during the run and 2000 after sorting only indicates that you chose the wrong occurrence number.

You chose a particular Occ. no. based on something, past history, detection process in place or a "gut feeling". This was found to be incorrect during the sorting process.
The information you gathered during sorting is not used to change the Occ. no., it should be used to improve the process.

A

#### Andrews

I feel the thread is going in a different direction. Maybe because I did not project my problem properly.Let me explain my problem with a hypothetical example.

Example :Let us assume that we work from 8.30 a.m to 5.00p.m (8hrs with an 1/2 hr lunch break) and that 'X' job was running from 8.30 a.m on 21.03.2002 after setting approval and we had detected a hole undersize problem during the hourly inspection (DETECTION method) that was conducted at 11.30 a.m whereas during 10.30 inspection we did not have this failure.Since we keep the items that ran between the last hourly check and the present check separately,we were able to quarantine the quantity between 10.30 inspection and 11.30 inspection.So maximum number of non-conforming products is the quantity that will run between 10.30 check and 11.30 check (say 1000 nos.).After correcting the problem we ran the machine till 2.30 p.m without a problem.But at 2.30 hourly inspection we detected the SAME problem.We quarantine the quantity between 1.30 inspection and 2.30 inspection.Let us say we again got 1000 defective pieces.We correct the problem and run this machine till 9.00 next day without this or any other problem.Totally we have got the same failure (hole undersize) twice during the production run of 10000 pieces and the total no. of defectives is 1000+1000=2000nos.
Based on this case what is the occurence rating I should give and why?

D

#### D.Scott

Andrews

The Potential Failure Mode and Effects Analysis (FMEA Third Edition) Reference Manual gives a pretty straight forward evaluation criteria on page 49.

Based on the numbers you give, you show a 1 in 5 occurrance (number of failed pieces in the total run). This would be classed as "very high" on the chart and result in a ranking of 10. You can also determine the ranking based on Ppk values which is explained on page 71.

Now to the question.

If you determine a failure occurs every 3 hours, why not put a preventive maintenance program into effect which changes the (assumption here) drill every 2 hours? This would slow down the process for the change but you would gain on the number of parts made without a nonconformance.

One puzzle though. You say you can run from 2:30 until 9:00 the next day with no problem. I would be very interested in learning the off shift secret on how they keep running with no problem. Either they are not measuring the same way to find failures or they have developed a way to run the equipment that my day shift needs to learn. There is a definate pattern shown on days. I would spend a whole lot of time finding out why there is such a big difference.

Dave

A

#### Al Dyer

D. Scott,

Very astute, why does it seem that if there are 3 shifts, there are 3 different "companies" and opinions. Like you say, there is a need to root out the problem between the shifts.

In doing this I would also look at the total fallout rate reported by the customer. If you have no customer complaints from any shift, maybe the first shift is being over critical?

This situation just cries for a mean time between failure study and have all shifts adhere tio the resulting data.

Any traceability data?

Internally, if you hold an hours worth of production for sorting and find 2 bad pieces, what is your PPM? The hours worth of production or the 3 bad pieces?

Look at the real world when calculating PPM. If the big 3 find one bad part and put an entire shioment of 10,000 pieces on hold, they will count 10,000 pieces against your PPM.

Is this right? Not in my opinion.

Don't bash yourself too much, it is your company and you do as you wish while staying within the guidelines you have chosen. If you hold an hourly batch, inspect it and report only those actual defects to your internal PPM.
-----------------------------------------------
Hypothetical from left field:

We find 1 bad part laying on a table after production has been shut down for the day.

The part is not traceable.

We produce 100,000 parts per day.

Do we hold all production from that day and do a sort? I think not.

Since it is not traceable, was it even from today, or could it be from maybe 3 weeks ago? Possibly

Maybe call the customer and see how everything is doing before going into kamakazi mode? Sure

Think on a broad scope and control that which you can? Yes
------------------------------------------------------

Just some thoughts to invigorate the thought process!!!

Why the Greek god Hephaestus should have done a design FMEA (DFMEA) on his giant robot APQP and PPAP 1
Design FMEA for a component - Should I make the following assumptions? FMEA and Control Plans 7
S What should the FMEA Severity for SC & CC Characteristics be? FMEA and Control Plans 4
M Should all Drawing Dimensions be in the FMEA FMEA and Control Plans 5
H What should be included in a Machining Process FMEA? FMEA and Control Plans 8
R Should I include all possible Risks of our software in the FMEA? US Food and Drug Administration (FDA) 7
C DFMEA (Design FMEA) and PFMEA (Process FMEA) - Who should lead? FMEA and Control Plans 14
L FMEA - Should a severity of 9 or 10 be always followed by recommended actions? FMEA and Control Plans 2
FMEA start point - should it be flexible? FMEA and Control Plans 2
A Should inspection be part of the FMEA FMEA and Control Plans 2
A FMEA Reviews - At what frequency should FMEA's be reviewed? FMEA and Control Plans 26
A Process FMEA - Should FMEA be done for all processes? FMEA and Control Plans 7
P Shipping by our own truck as part of an FMEA - Where FMEAs should end FMEA and Control Plans 6
UDI-DI how should we interpret Device version or model to determine if a new UDI-DI is needed? EU Medical Device Regulations 0
Interesting Discussion Should ISO 9004 be changed from a guidance standard to a requirements standard? ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 5
Should I take an online course for a career in Occupational Health and Safety? Career and Occupation Discussions 2
Should a Class 1 medical device with an option to measure body weight be considered Class 1m? EU Medical Device Regulations 0
Should APQP/PPAP has its own section in a QM? Quality Management System (QMS) Manuals 1
What should i choose for "testing procedure" characteristics? (N95) General Information Resources 0
Should eIFU link per ISO 15223-1:2016 be added to labels out of scope of Reg 207/2012? EU Medical Device Regulations 1
Which Sampling Plan(s) Should I Use? Inspection, Prints (Drawings), Testing, Sampling and Related Topics 7
Document release vs its related training. Which should come first? ISO 13485:2016 - Medical Device Quality Management Systems 18
Which department should prepare the control plan? could you show me a standard regarding to this matter. FMEA and Control Plans 17
Help settle a disagreement: Should external providers of preventive maintenance be on your ASL? AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 5
Master Samples - What should we be keeping? IATF 16949 - Automotive Quality Systems Standard 9
Supplier delivered recent PPAP, should he deliver yearly layout inspection? IATF 16949 - Automotive Quality Systems Standard 4
Vote - Should ISO9004 Become a Requirements Standard? ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 11
Capability Study - in the beginning of your career what should you have known about the tool Quality Tools, Improvement and Analysis 11
Manufacturers should develop a testing device for covid19 Service Industry Specific Topics 0
510(k) submission - Which name should I use in the submission? Other US Medical Device Regulations 3
ISO 19011:2018 - 5.4.2 "...audit program should engage in appropriate continual development..." Training - Internal, External, Online and Distance Learning 4
Should I perform Gage R&R only at the beginning of a new project? Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 6
Should the requirements FAA/EASA Part 21 be addressed within the QMS and AS9100D quality manual? AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 5
Should 510(k) Predicates be Actively Listed Devices? Other US Medical Device Regulations 12
On PFMEA for danger labels - Label always should be assigned severity 10 ? FMEA and Control Plans 3
Who should be listed as the manufacturer/distributor on the box? 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 15
MDR, RED and LVD - Should our device comply with them? EU Medical Device Regulations 3
How Many Processes should be created for each Department? Process Maps, Process Mapping and Turtle Diagrams 5
Should volume of sales be factored into risk probability assessments? ISO 14971 - Medical Device Risk Management 33
Should potential bugs be considered in software risk analysis? ISO 14971 - Medical Device Risk Management 5
Should safety checks be included in the Control Plan? IATF 16949 - Automotive Quality Systems Standard 5
Which incubation condition should be selected to recover both bacteria and fungus effectively Miscellaneous Environmental Standards and EMS Related Discussions 3
Is there a specific location for PPE such as safety glass holders and glove dispensers should be mounted Occupational Health & Safety Management Standards 10
Which Registrar Should I Choose for ISO 9001:2015 registration? Registrars and Notified Bodies 10
Who should receive the bills from suppliers and vendors, account payable or procurement? Consultants and Consulting 4
IATF 16949 8.4.1 Control of externally provided processes, products and services - Should the CB be on our Approved Supplier List? IATF 16949 - Automotive Quality Systems Standard 10
We are ISO 13485:2016 should we be audited to ISO 14971 ISO 13485:2016 - Medical Device Quality Management Systems 16
Received a Major finding during IATF Surveillance audit for loss of BIQS Level 3 (more than 6 SPPS in 6 months)...how should we address SYSTEMIC CA? IATF 16949 - Automotive Quality Systems Standard 11
Organization merger. Should we keep two separate ISO 13485 certificates? ISO 13485:2016 - Medical Device Quality Management Systems 6